Skip to main content
Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Cytomegalovirus-specific CD8+ T-cell responses are associated with arterial blood pressure in people living with HIV

  • Vibe Ballegaard,

    Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Writing – original draft

    Affiliations Department of Infectious Diseases, Viro-immunology Research Unit, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark, Department of Clinical Immunology, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

  • Karin Kaereby Pedersen,

    Roles Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing

    Affiliation Department of Infectious Diseases, Viro-immunology Research Unit, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

  • Peter Brændstrup,

    Roles Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing

    Affiliations Department of Clinical Immunology, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark, Department of Hematology, Herlev University Hospital, Herlev, Denmark

  • Nikolai Kirkby,

    Roles Data curation, Methodology

    Affiliation Department of Medical Microbiology, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

  • Anette Stryhn,

    Roles Formal analysis, Investigation, Writing – review & editing

    Affiliation Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark

  • Lars P. Ryder,

    Roles Conceptualization, Data curation, Supervision, Writing – review & editing

    Affiliation Department of Clinical Immunology, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

  • Jan Gerstoft,

    Roles Conceptualization, Supervision, Writing – review & editing

    Affiliation Department of Infectious Diseases, Viro-immunology Research Unit, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

  • Susanne Dam Nielsen

    Roles Conceptualization, Project administration, Supervision, Validation, Writing – review & editing

    sdn@dadlnet.dk

    Affiliation Department of Infectious Diseases, Viro-immunology Research Unit, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark

Abstract

People living with HIV (PLHIV) are at increased risk for cardiovascular disease (CVD), and immunity against cytomegalovirus (CMV) may be a contributing factor. We hypothesized that enhanced T-cell responses against CMV and CMV-IgG antibody-levels are associated with higher arterial blood pressure in PLHIV. We assessed serum CMV-IgG, systolic- (SBP) and diastolic- (DBP) blood pressure, pulse pressure (PP), traditional risk factors, activated CD8+ T-cells (CD38+HLA-DR+), senescent CD8+ T-cells (CD28-CD57+) and interleukin-6 (IL-6) in 60 PLHIV and 31 HIV-uninfected controls matched on age, gender, education and comorbidity. In PLHIV, expression of interleukin-2, tumor necrosis factor-α and interferon-γ was measured by intracellular-cytokine-staining after stimulation of T-cells with CMV-pp65 and CMV-gB. Associations between CMV-specific immune responses and hypertension, SBP, DBP or PP were assessed by multivariate logistic and linear regression models adjusted for appropriate confounders. The median age of PLHIV was 47 years and 90% were male. Prevalence of hypertension in PLHIV was 37% compared to 55% of HIV-uninfected controls. CMV-specific CD8+ T-cell responses were independently associated with higher PP (CMV-pp65; β = 2.29, p = 0.001, CMV-gB; β = 2.42, p = 0.001) in PLHIV. No significant differences were found with regard to individual measures of SBP and DBP. A possible weak association was found between CMV-IgG and hypertension (β = 1.33, p = 0.049) after adjustment for age, smoking and LDL-cholesterol. HIV-related factors, IL-6, CD8+ T-cell activation or CD8+ T-cell senescence did not mediate the associations, and no associations were found between CMV-specific CD4+ T-cell responses and blood pressure in PLHIV. In conclusion, increased arterial blood pressure in PLHIV may be affected by heightened CMV-specific CD8+ T-cell responses.

Background

Despite treatment with antiretroviral therapy (cART), people living with HIV (PLHIV) have lower life expectancy than HIV-uninfected individuals[1], partly explained by excess risk of cardiovascular diseases (CVD)[25]. Hypertension is one of the major CVD risk factors[6], but studies are contradictory as to whether prevalence of hypertension is increased in treated PLHIV compared to uninfected controls [710]. However, several studies showed that HIV-related factors such as a low nadir CD4+ T-cell count and longer duration of cART were associated with increased risk of hypertension[8,9,11]. Mechanisms behind excess risk of CVD in PLHIV are multifactorial, and the search for underlying contributing factors is important in order to prevent morbidity and mortality.

CMV is a human β-herpesvirus with a world-wide distribution and a high prevalence in most populations[12,13]. The majority of PLHIV are infected with CMV, and PLHIV have higher T-cell and antibody-specific responses against CMV than HIV-uninfected[14,15]. CMV has been linked to increased risk of CVD-related morbidity and mortality in PLHIV[16], and increased magnitude of CMV-specific immune responses have been associated with subclinical cardiovascular disease[1719]. The relationship between CMV-specific immune responses and risk of CVD has been thoroughly described in the general population[2030], where CMV-specific immune responses are associated with risk of hypertension[22,2730], and CMV-specific T-cells have been shown to have a direct effect on the vascular endothelium[27,3134]. Thus, the relationship between CMV and adverse CVD-outcomes is not a unique feature of HIV infection, but may be increasingly relevant in this population due to high prevalence of CMV in PLHIV, higher immune responses against CMV, and increasing life expectancy leading to a higher lifetime CMV exposure in PLHIV.

In this study, we hypothesized that higher CMV-specific CD8+ and CD4+ T-cell responses against CMV-pp65 and CMV-gB, or higher serum CMV IgG, would be associated with higher systolic blood pressure, higher pulse pressure and hypertension in PLHIV.

Methods

Study population

A total of 60 PLHIV from the outpatient clinic at the Department of Infectious Diseases, Rigshospitalet, Copenhagen, were consecutively included in a study regarding cognitive function and cardiovascular risk profile, and 31 HIV-uninfected controls were selected for comparison and matched overall on age, gender, BMI, education and comorbidity index (assessed by the Charlson comorbidity index). Procedures for recruitment, data collection, demographics, and clinical characteristics of the participants have previously been described in detail[15,3539]. Nineteen of the controls also participated in a study on diabetes[40]. All PLHIV had suppressed viral replication for ≥ 1 year before inclusion, and had been on stable treatment with cART for ≥2 years. Exclusion criteria were acute illness, chronic infection with hepatitis B virus (HBV) defined by routine measurement of HBsAg/anti-HBc or hepatitis C virus (HCV) defined by routine measurement of anti-HCV/HCV-RNA, intravenous drug use, autoimmune diseases, diabetes (HbA1c > 48 mmol/mol and/or fasting glucose > 7 mmol/L), cancer, or pregnancy. Inclusion and exclusion criteria were selected to eliminate confounders with known impact on non-AIDS comorbidity.

Ethics approval and consent to participate

The study was approved by the National Committee on Biomedical Research Ethics for the Capital Region of Denmark (H-2-2010-089) and the Danish Data Protection Agency and conducted in accordance with the second declaration of Helsinki. Written informed consent was obtained from all participants.

Clinical assessments

Detailed information on demographic factors, medical history, smoking, physical activity, medication and data regarding HIV infection were collected at inclusion[3537]. All examinations were performed by trained medical staff. Waist and hip measurements and body mass index (BMI) calculations were performed[37], and according to WHO guidelines, abdominal obesity was defined as waist-hip ratio ≥ 0.90 for men and ≥ 0.85 for women[41]. Blood pressure (BP) was measured on the left arm after 5 minutes rest and in lying position using the mean of two measurements from a digital blood pressure monitor. Hypertension was defined as anti-hypertensive treatment and/or ≥ 140 mmHg systolic (SBP) and/or ≥ 90 mmHg diastolic (DBP) blood pressure values[42], and pulse pressure (PP) was calculated as the difference between systolic and diastolic blood pressure[43].

Blood analyses

A fasting venous blood sample was collected and analyzed for total cholesterol, LDL-cholesterol, HDL-cholesterol, HbA1c, and glucose[35,37]. CD4+ T-cell count (cells/uL) was measured as a routine analysis by flow cytometry as previously described[35]. HIV viral load (copies/mL) was measured with a polymerase chain reaction (PCR) quantitative kit (COBAS®AmpliPrep/COBAS®TaqMan® 48 System; Roche, Basel, Switzerland) according to the manufacturer’s instructions. Nadir CD4 was recorded as the lowest CD4+ T-cell count measured during HIV-infection[35]. As previously described, plasma concentrations of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), were measured by Meso-Scale Discovery MULTI-SPOT plate (MSD, Gaithersburg, MD)[35], and T-cell subsets (percentage of activated (CD38+HLA-DR+) and senescent (CD28-CD57+) CD8+ T-cells) were determined using a six-colour FACSCanto flow cytometer (Becton Dickinson, Franklin Lakes, NJ)[35].

CMV-specific immune responses

In this study we used frozen PBMC´s from the participants as a source of both antigen presenters and T-cells and short term stimulation (6 hours) with 15mer peptides. The method is a standardized and validated approach that has been used by multiple groups to determine ex vivo T-cell responses[4448]. The method has been described in detail in a previous publication[15]. In CMV-seropositive PLHIV (n = 54), CMV-specific CD8+ and CD4+ T-cell responses were determined by measurement of intracellular expression of IL-2, TNF-α and IFN-γ after stimulation of peripheral blood mononuclear cells (PBMC) with CMV-pp65 and CMV-gB[15]. We used the CFC Becton Dickinson assay that has been optimized by the manufacturer and with a recommended stimulation time of 6 hours (BD Bioscience)[46]. In brief, thawed PBMC were stimulated in duplicate samples using either a CMV-pp65 peptide pool containing 138 peptides derived from a peptide scan through 65 kDa phosphoprotein (pp65) (Swiss-Prot ID: P06725), a CMV-gB peptide pool of 224 peptides derived from a peptide scan through Envelope glycoprotein B (gB) (Swiss-Prot ID: P06473), or Staphylococcal enterotoxin B (SEB) (2.5 ug/mL; Sigma-Aldrich) as a positive control. The stimulated PBMC were incubated in the presence of co-stimulatory anti-CD28/CD49d (BD Biosciences) for six hours at 37ºC and Brefeldin A (BD Biosciences) was added after 2 hours. An unstimulated control was incubated with DMSO, anti-CD28/CD49d and Brefeldin A in order to detect background staining. Flourescence Minus One (FMO) controls were used as gating controls, and isotype controls were used to check for background due to nonspecific antibody binding.

At the end of stimulation, cells were washed, stained with BD Horizon Fixable Viability Stain 450 (FVS450), treated with FACS lysing- and FACS permeabilization solution (BD FACS) and stained with anti-CD4-FITC/anti-CD69-PE/anti-CD3-PerCP (clone SK3/L78/SK7 BD fastimmune), anti-CD8-V500 (clone SK1 BD Horizon), anti-IL-2-BV421 (clone 5344.111 BD Horizon), anti-TNF-α -APC (clone 6401.1111 BD FastImmune) and anti-IFN-γ-PE-Cy7 (clone B27 BD Pharmingen), at 22ºC for 30 minutes. Cytokine responses were acquired immediately using a BD FACSCanto II flow cytometer and flow cytometry results were analysed using BD FACSDiva (v8.0.1) software (BD Biosciences). The gating strategy has previously been described[15]. In brief, a lymphocyte gate based on FSC/SSC, a singlet gate, and a live/dead cell gate were applied before gating on CD3+CD4+ and CD3+CD8+ cells. Further, for each T-cell subset, CD69+ populations were gated from CD69+ histograms for CD4+ and CD8+ populations, and expression of IFN-γ, TNF-α and IL-2 was then determined from the CD4+ and CD8+ populations. Expression of IFN-γ, TNF-α and IL-2 was determined from the CD4+CD69+ and CD8+CD69+ populations, and co-expression patterns were analyzed by application of a combinational gating strategy. Net subset frequencies of CMV-specific CD4+ and CD8+ T-cells were determined after background subtraction, and a positive cytokine response was defined as above 0.01% of the reference subset (CD4+ or CD8+ T-cells) or at least 40 events[49,50]. By summing up the frequency of CD4+ or CD8+ T-cells within each unique combination of functions (IFN-γ, TNF-α or IL-2), we analyzed the magnitude of the total CMV-specific response (%CD8+ or %CD4+). Thus, each responding cell was calculated only once.

CMV IgG antibody levels were measured in participants with available frozen serum samples (n = 85), using a commercial chemiluminescent immunoassay (LIAISON ® CMV IgG II, DiaSorin S.P.A., Saluggia, Italy)[51], and antigen-binding avidity of CMV IgG antibodies in serum was measured with the LIAISON® CMV Avidity II assay (DiaSorin S.P.A., Saluggia, Italy)[52], according to manufacturer’s instructions. Plasma CMV DNAemia was assessed using the Amplicor CMV Monitor test (Roche Diagnostics, Indianapolis, IN).

Statistical analysis

Continuous variables were reported as median and interquartile range, while categorical data as percentage of total number and frequency. Different groups were compared with Student t-test or Mann Whitney test for continuous variables or Χ2-test/Fisher´s tests for categorical variables, where appropriate. Univariate and multivariable logistic models were used to test the association between CMV-specific T-cell responses and CMV-IgG and hypertension. Unadjusted and adjusted odds ratios (OR/aOR) and 95% confidence intervals [CIs] were reported. In addition, linear regression analysis was performed with CMV-IgG or CMV-specific CD4+ and CD8+ T-cells as independent variables and continuous measures of SBP, DBP and PP as dependent variables. Covariates were selected based on clinical assumptions or known associations with increased arterial blood pressure (age, education, sex, LDL-cholesterol, smoking, HbA1c, abdominal obesity, CMV IgG and HIV status). Due to a small sample size and few events, a backward elimination selection approach including only covariates with p<0.20 in univariate analysis and α = 0.10 was applied to build a basic multivariate model including CMV-IgG (per 100 U/ml)/total CMV-specific T-cell responses (% of CD4+ or CD8+ T-cells) in addition to age (per decade), LDL-cholesterol (per mmol/L) and smoking (yes/no). Using the same backward elimination selection approach, all the basic multivariate models included adjustment for age, smoking and LDL-cholesterol. Separate multivariate models for PLHIV were created to assess the association between CMV-specific immune responses and hypertension, SBP, DBP or PP while considering selected HIV-related (nadir CD4+, CD4+/CD8+ ratio and duration of HIV infection) or immunologic confounders (IL-6, senescent CD8+ T-cells, activated CD8+ T-cells). Selected covariates were added to the multivariate models one by one. Additional models were only created when the association was positive in the basic multivariate models. Residuals were checked for normal distribution and log transformation was performed when appropriate. False discovery rate (Benjamini-Hochberg method) adjusted p-values were calculated to adjust for multiple testing. A P-value of <0.05 was considered statistically significant, and statistical analysis was performed using SAS (version 9.4 SAS Institute, Copenhagen, Denmark) or GraphPad Prism 7 (GraphPad Software Inc).

Results

Study participants

A total of 60 PLHIV and 31 HIV-uninfected controls were included. Demographic and clinical characteristics are shown in summary in Table 1, and have previously been published[15,3539].

thumbnail
Table 1. General characteristics of the study population.

https://doi.org/10.1371/journal.pone.0226182.t001

Current CMV reactivation or primary CMV infection was not detected, since none of the participants had detectable CMV DNA in plasma, and all had an avidity index above 0.20. In addition, all PLHIV had suppressed HIV-RNA. In PLHIV 37% had hypertension compared to 57% of HIV-uninfected controls. However a significant difference in risk of hypertension could not be identified, and no significant differences were detected in SBP, DBP or PP (Table 1). In addition, HIV infection was not associated with increased risk of hypertension in univariate analysis or when adjusting for age, LDL-cholesterol and smoking (aOR 0.51 (0.19–1.39), p = 0.191).

Increased CMV-specific CD8+ T-cell responses were associated with higher pulse pressure in PLHIV

In CMV-seropositive PLHIV, there was a consistent association between increased CMV-specific CD8+ T-cell responses and PP in univariate analysis and also in multivariate analysis, after adjustment for age, smoking and LDL-cholesterol (Table 2, Fig 1). We could not consistently confirm, that the same association was present between increased CMV-specific CD8+ T-cell responses (% of CD8+ T-cells) and higher SBP (mmHg). (Table 2, Fig 1). No associations were found between CMV-specific CD8+ T-cells and DBP, and higher CMV-specific CD8+ T-cell responses were not associated with hypertension in PLHIV (Table 2). In addition, we did not find that CMV-specific CD4+ T-cell responses were associated with SBP, PP, or hypertension in PLHIV (S1 Table).

thumbnail
Fig 1. CMV-specific CD8+ T-cell responses are associated with systolic blood pressure and pulse pressure in PLHIV.

Simple linear regression with CMV-specific (pp65 and gB) CD8+ T-cells (% of CD8+) as independent variable and systolic blood pressure or pulse pressure as dependent variables. A fitted plot with 95% confidence limits is shown.

https://doi.org/10.1371/journal.pone.0226182.g001

thumbnail
Table 2. Univariate and multivariate regression models analysing associations between CMV-specific CD8+ T-cell responses and blood pressure in PLHIV.

https://doi.org/10.1371/journal.pone.0226182.t002

Impact of HIV-related factors on associations between CMV-specific CD8+ T-cell responses and pulse pressure in PLHIV

Nadir CD4+, duration of HIV infection and the CD4+/CD8+ ratio was added to the multivariate models one at a time, to determine whether these HIV-related factors might mediate the association between CMV-specific CD8+ T-cell responses and pulse pressure in PLHIV. The associations between CMV-specific CD8+ T-cells and PP were not affected by adjustment for HIV-related factors (Table 2). In addition, we tested whether adjusting for HIV-related factors would change the association between CMV-specific CD8+ T-cells responses and systolic blood pressure, and we did not find that these factors consistently affected the associations.

Impact of T-cell activation, T-cell senescence, and IL-6 on associations between CMV-specific CD8+ T-cell responses and pulse pressure in PLHIV

CD8+ T-cell activation (CD38+HLA-DR+, % of CD8+), CD8+ T-cell senescence (CD28-CD57+, % of CD8+), and plasma IL-6 (pg/mL) was added to the basic multivariate models one at a time to determine the impact of immunologic factors often associated with both CMV, HIV and vascular aging.

None of the immunologic factors had an impact on the associations between CMV-specific CD8+ T-cell responses and PP (data shown in Table 2 and in S2 Table).

Serum CMV IgG levels and hypertension in PLHIV

In PLHIV, no associations were found between CMV IgG and hypertension in univariate analysis, but a possible weak association was found after adjustment for age, smoking and LDL-cholesterol (Table 3). When investigating continuous measures of blood pressure, CMV IgG was not associated with elevated SBP, DBP or PP, in either univariate or multivariate linear regression analysis (data shown in S3 Table).

thumbnail
Table 3. Univariate and multivariate logistic regression analysis investigating risk factors for hypertension in CMV-seropositive PLHIV.

https://doi.org/10.1371/journal.pone.0226182.t003

Discussion

This study identified a possible relationship between CMV-specific cellular immunity and blood pressure in PLHIV on stable treatment. Increased CMV-specific CD8+ T-cell responses were independently associated with higher pulse pressure.

In the present study, 37% of PLHIV had hypertension compared to 57% of HIV-uninfected controls, but a significant difference in risk of hypertension was not identified which may be due to a small sample size and risk of type II errors. Importantly, the control group was matched on age, gender, education and comorbidity index[35]. For comparison, the prevalence of hypertension was 44% among PLHIV and 58% among controls in a recent large Danish cohort study of predominantly well-treated PLHIV[8]. In that study, HIV was associated with a lower risk of hypertension[8]. Although prevalence of hypertension may not be increased in PLHIV, the causal factors leading to hypertension may still differ, and it is important to understand the pathogenesis in order to prevent CVD and CVD-related mortality.

CMV-specific T-cell responses are elevated in PLHIV compared to HIV-uninfected controls[14,17,53], and CMV-specific CD8+ T-cell responses have been associated with carotid intima media thickness (cIMT)[17]. In addition, studies in HIV-uninfected populations has provided evidence of a relationship between CMV-specific immune responses and elevated blood pressure or arterial stiffness[22,2730]. However, no previous studies have investigated the relationship between blood pressure and CMV-specific T-cell immunity in PLHIV. In line with previous studies, we did not find associations between CMV-specific CD4+ T-cells and blood pressure. Although the CD4+ and CD8+ T-cell responses are linked, it is a well-known feature of CMV immunity in both PLHIV and HIV-uninfected, that the CMV-specific CD8+ T-cell compartment is expanded in comparence to the CD4+ T-cell compartment[14,44,45] but we were not able to further address the mechanism behind these observations.

In PLHIV, a recent study showed that PLHIV on cART had increased arterial stiffness compared to a matched control group[54]. Arterial stiffness is a strong predictor of CVD and CVD-related mortality[55]. Non-invasive surrogate markers of arterial stiffness are typically pulse pressure and isolated systolic hypertension[56], and some studies indicate that PP may better characterize arterial stiffness than SBP[43,57].Traditional risk factors may play a role, but in this study the association between CMV-specific CD8+ T-cell responses and pulse pressure, was still present after adjustment for traditional risk factors.

The mechanism by which CMV-specific CD8+ T-cells contribute to elevated blood pressure or arterial stiffness has not been identified. We previously showed that CMV-specific CD8+ T-cell responses were associated with senescence and terminal differentiation of CD8+ T-cells in treated PLHIV[15]. In addition, senescent CD8+ T-cells has been associated with arterial stiffness and hypertension in HIV-uninfected individuals[30,58], and increased frequencies of activated and senescent CD8+ T-cells were associated with prevalence of carotid artery lesions and arterial stiffness in PLHIV[5961]. The action of activated and/or senescent CD8+ T-cells on the endothelium could be direct (as in cytotoxicity) or indirect through increased release of proinflammatory cytokines. In the present study, activated or senescent CD8+ T-cells and/or serum levels of IL-6 was not associated with elevated blood pressure, and did not confound the association between CMV-specific CD8+ T-cell responses and pulse pressure. Since our study is observational and not mechanistic, we are not able to further address the mechanism behind the observed associations.

Duration of HIV infection and biological age are important confounders to consider. The majority of PLHIV are CMV-seropositive and the CMV-specific memory T-cell compartment is inflated during aging. This could lead to CMV immunity being randomly associated with hypertension. We address this by adjusting for age in the basic multivariable models, and adjustment for duration of HIV infection is included in additional multivariate models. The associations were stable when adjusting for age and duration of HIV infection. In a previous study, we found that nadir CD4+ and duration of HIV infection was associated with CMV IgG, but not with CMV-specific T-cell responses[15], and a low nadir CD4+ has been associated with increased risk of hypertension in several studies[8,11,62]. We hypothesized that the effect of CMV immunity on blood pressure was mediated by effects of late stage HIV defined by a low nadir CD4+ or inversed CD4+/CD8+ ratio. However, the association between CMV-specific CD8+ T-cells and PP was not affected, and we did not find support of this hypothesis. However, importance of HIV-related factors should be addressed in future studies.

CMV IgG has been established as a cardiovascular risk factor [29] [20,21,23,25], and has often been interpreted as a surrogate marker of subclinical CMV reactivations. However, CMV-IgG probably reflect a combined effect of lifetime burden of CMV, recent reactivations and reinfections, and host factors determining ability to suppress CMV replication[63,64].

PLHIV in our study had higher levels of CMV IgG than HIV-uninfected controls, and a possible weak association was found between higher CMV IgG and hypertension after adjustment for age, LDL-cholesterol and smoking. Because our sample size was small and number of events was limited the finding is exploratory. However, previous studies suggest that increased CMV IgG may be related to subclinical CVD in PLHIV[18,19] and also in HIV-uninfected populations,

The present study has limitations. First, it is a cross-sectional study with inclusion of a selected and limited number of participants. Therefore, direct cause-effect relationships could not be identified, and results may not be applicable to the general HIV population. Secondly, the small sample size increases the risk of type II errors, and limits the possibility to adjust for all appropriate confounders when multivariate models are created. Thus, the results should be interpreted with caution and should be confirmed in studies with larger sample sizes. Additionally, this study is descriptive and mechanistic studies are required to address mechanisms by which CMV-specific CD8+ T-cells contribute to increased blood pressure or arterial stiffness in treated PLHIV. Nearly all PLHIV in our cohort were CMV-seropositive, so we were not able to compare CMV-seropositive and CMV-seronegative individuals, although such comparisons would have added important extra information to the study. In addition, we were not able to perform analysis of CMV-specific T-cell responses in the control group due to insufficient amounts of PBMC although such analyses would have added relevant information to the study.

Since more than 150 CMV epitopes are immunogenic for CD8+ and CD4+ T-cells, and stimulation with 19 specific CMV epitopes are required to estimate the total CD8+ and CD4+ T-cell response to CMV[45], future studies would benefit from a full characterization of CMV-specific cellular immunity[65].

In addition, since CMV-specific CD8+ T-cell responses are polyclonal and major variations between individuals in response to CMV-antigens has been demonstrated[66], it is a limitation that we were not able to use a broader range of CMV-specific antigens in the assay. The various antigen-specific CD8+ T-cells could additively or synergistically affect blood pressure, and a broader representation of CMV antigens might have found stronger associations than presented in this study.

A strength of the study is a well-characterized cohort in terms of immunologic, cardiovascular and metabolic risk factors and important confounders were excluded since we used strict inclusion criteria. The precise role of CMV-specific immune responses with regard to hypertension and premature vascular aging in HIV infection warrants further investigations.

Supporting information

S1 Table. Univariate and multivariate logistic regression investigating associations between CMV-specific CD4+ T-cell responses and blood pressure in people living with HIV.

https://doi.org/10.1371/journal.pone.0226182.s001

(PDF)

S2 Table. Multivariate linear regression analysis investigating associations between CMV-specific CD8+ T-cells and pulse pressure in PLHIV while adjusting for immunologic factors (IL-6, senescent CD8+ T-cells and activated CD8+ T-cells).

https://doi.org/10.1371/journal.pone.0226182.s002

(PDF)

S3 Table. Univariate and multivariate linear regression investigating associations between CMV-IgG and systolic blood pressure, diastolic blood pressure and pulse pressure in people living with HIV.

https://doi.org/10.1371/journal.pone.0226182.s003

(PDF)

Acknowledgments

We gratefully acknowledge the participants who made this study possible, and we thank the staff of our departments for invaluable assistance.

References

  1. 1. Legarth RA, Ahlström MG, Kronborg G, Larsen CS, Pedersen C, Pedersen G, et al. Long-Term Mortality in HIV-Infected Individuals 50 Years or Older. JAIDS J Acquir Immune Defic Syndr 2016; 71:213–218. pmid:26334734
  2. 2. Rasmussen LD, May MT, Kronborg G, Larsen CS, Pedersen C, Gerstoft J, et al. Time trends for risk of severe age-related diseases in individuals with and without HIV infection in Denmark: a nationwide population-based cohort study. Lancet HIV 2015; 2:e288–e298. pmid:26423253
  3. 3. Smith CJ, Ryom L, Weber R, Morlat P, Pradier C, Reiss P, et al. Trends in underlying causes of death in people with HIV from 1999 to 2011 (D:A:D): a multicohort collaboration. Lancet 2014; 384:241–248. pmid:25042234
  4. 4. Antiretroviral Therapy Cohort Collaboration TATC. Causes of death in HIV-1-infected patients treated with antiretroviral therapy, 1996–2006: collaborative analysis of 13 HIV cohort studies. Clin Infect Dis 2010; 50:1387–96. pmid:20380565
  5. 5. Palella FJ, Baker RK, Moorman AC, Chmiel JS, Wood KC, Brooks JT, et al. Mortality in the highly active antiretroviral therapy era: changing causes of death and disease in the HIV outpatient study. J Acquir Immune Defic Syndr 2006; 43:27–34. pmid:16878047
  6. 6. Kannel WB, Wolf PA, McGee DL, Dawber TR, McNamara P, Castelli WP. Systolic blood pressure, arterial rigidity, and risk of stroke. The Framingham study. JAMA 1981; 245:1225–9. pmid:7206111
  7. 7. Bergersen BM, Sandvik L, Dunlop O, Birkeland K, Bruun JN. Prevalence of Hypertension in HIV-Positive Patients on Highly Active Retroviral Therapy (HAART) Compared with HAART-Naïve and HIV-Negative Controls: Results from a Norwegian Study of 721 Patients. Eur J Clin Microbiol Infect Dis 2003; 22:731–736. pmid:14610658
  8. 8. Gelpi M, Afzal S, Lundgren J, Ronit A, Roen A, Mocroft A, et al. Higher Risk of Abdominal Obesity, Elevated LDL Cholesterol and Hypertriglyceridemia, but not of Hypertension, in People Living with HIV: Results from the Copenhagen Comorbidity in HIV Infection (COCOMO) Study. Clin Infect Dis Published Online First: 17 February 2018. pmid:29471519
  9. 9. Baekken M, Os I, Sandvik L, Oektedalen O. Hypertension in an urban HIV-positive population compared with the general population: influence of combination antiretroviral therapy. J Hypertens 2008; 26:2126–2133. pmid:18854751
  10. 10. Gazzaruso C, Bruno R, Garzaniti A, Giordanetti S, Fratino P, Sacchi P, et al. Hypertension among HIV patients: prevalence and relationships to insulin resistance and metabolic syndrome. J Hypertens 2003; 21:1377–82. pmid:12817187
  11. 11. Manner IW, Trøseid M, Oektedalen O, Baekken M, Os I. Low Nadir CD4 Cell Count Predicts Sustained Hypertension in HIV-Infected Individuals. J Clin Hypertens 2013; 15:101–106.
  12. 12. Cannon MJ, Schmid DS, Hyde TB. Review of cytomegalovirus seroprevalence and demographic characteristics associated with infection. Rev Med Virol 2010; 20:202–213. pmid:20564615
  13. 13. Staras SAS, Dollard SC, Radford KW, Flanders WD, Pass RF, Cannon MJ. Seroprevalence of cytomegalovirus infection in the United States, 1988–1994. Clin Infect Dis 2006; 43:1143–51. pmid:17029132
  14. 14. Naeger DM, Martin JN, Sinclair E, Hunt PW, Bangsberg DR, Hecht F, et al. Cytomegalovirus-specific T cells persist at very high levels during long-term antiretroviral treatment of HIV disease. PLoS One 2010; 5:e8886. pmid:20126452
  15. 15. Ballegaard V, Brændstrup P, Pedersen KK, Kirkby N, Stryhn A, Ryder LP, et al. Cytomegalovirus-specific T-cells are associated with immune senescence, but not with systemic inflammation, in people living with HIV. Sci Rep 2018; 8:3778. pmid:29491459
  16. 16. Lichtner M, Cicconi P, Vita S, Cozzi-Lepri A, Galli M, Lo Caputo S, et al. CMV co-infection and risk of AIDS and non-AIDS events in a large cohort of HIV-infected patients. J Int AIDS Soc 2012; 15:18197.
  17. 17. Hsue PY, Hunt PW, Sinclair E, Bredt B, Franklin A, Killian M, et al. Increased carotid intima-media thickness in HIV patients is associated with increased cytomegalovirus-specific T-cell responses. AIDS 2006; 20:2275–83. pmid:17117013
  18. 18. Masiá M, Robledano C, Ortiz de la Tabla V, Antequera P, López N, Gutiérrez F. Increased Carotid Intima-Media Thickness Associated with Antibody Responses to Varicella-Zoster Virus and Cytomegalovirus in HIV-Infected Patients. PLoS One 2013; 8:e64327. pmid:23717597
  19. 19. Parrinello CM, Sinclair E, Landay AL, Lurain N, Sharrett AR, Gange SJ, et al. Cytomegalovirus immunoglobulin G antibody is associated with subclinical carotid artery disease among HIV-infected women. J Infect Dis 2012; 205:1788–96. pmid:22492856
  20. 20. Gkrania-Klotsas E, Langenberg C, Sharp SJ, Luben R, Khaw K-T, Wareham NJ. Seropositivity and higher immunoglobulin g antibody levels against cytomegalovirus are associated with mortality in the population-based European prospective investigation of Cancer-Norfolk cohort. Clin Infect Dis 2013; 56:1421–7. pmid:23442763
  21. 21. Roberts ET, Haan MN, Dowd JB, Aiello AE. Cytomegalovirus antibody levels, inflammation, and mortality among elderly Latinos over 9 years of follow-up. Am J Epidemiol 2010; 172:363–71. pmid:20660122
  22. 22. Youn J-C, Kim JY, Jung MK, Yu HT, Park S-H, Kim I-C, et al. Analysis of cytomegalovirus-specific T-cell responses in patients with hypertension: comparison of assay methods and antigens. Clin Hypertens 2018; 24:5. pmid:29568571
  23. 23. Nieto FJ, Adam E, Sorlie P, Farzadegan H, Melnick JL, Comstock GW, et al. Cohort study of cytomegalovirus infection as a risk factor for carotid intimal-medial thickening, a measure of subclinical atherosclerosis. Circulation 1996; 94:922–7. pmid:8790026
  24. 24. Wang H, Peng G, Bai J, He B, Huang K, Hu X, et al. Cytomegalovirus Infection and Relative Risk of Cardiovascular Disease (Ischemic Heart Disease, Stroke, and Cardiovascular Death): A Meta-Analysis of Prospective Studies Up to 2016. J Am Heart Assoc 2017; 6. pmid:28684641
  25. 25. Gkrania-Klotsas E, Langenberg C, Sharp SJ, Luben R, Khaw K-T, Wareham NJ. Higher immunoglobulin G antibody levels against cytomegalovirus are associated with incident ischemic heart disease in the population-based EPIC-Norfolk cohort. J Infect Dis 2012; 206:1897–903. pmid:23045624
  26. 26. Firth C, Harrison R, Ritchie S, Wardlaw J, Ferro CJ, Starr JM, et al. Cytomegalovirus infection is associated with an increase in systolic blood pressure in older individuals. QJM 2016; 109:595–600. pmid:27071749
  27. 27. Terrazzini N, Bajwa M, Vita S, Cheek E, Thomas D, Seddiki N, et al. A novel cytomegalovirus-induced regulatory-type T-cell subset increases in size during older life and links virus-specific immunity to vascular pathology. J Infect Dis 2014; 209:1382–92. pmid:24203779
  28. 28. Li Z, Tang Y, Tang N, Feng Q, Zhong H, Liu Y, et al. High anti-human cytomegalovirus antibody levels are associated with the progression of essential hypertension and target organ damage in Han Chinese population. PLoS One 2017; 12:e0181440. pmid:28837559
  29. 29. Haarala A, Kähönen M, Lehtimäki T, Aittoniemi J, Jylhävä J, Hutri-Kähönen N, et al. Relation of high cytomegalovirus antibody titres to blood pressure and brachial artery flow-mediated dilation in young men: the Cardiovascular Risk in Young Finns Study. Clin Exp Immunol 2012; 167:309–16. pmid:22236008
  30. 30. Yu HT, Youn J-C, Kim JH, Seong Y-J, Park S-H, Kim HC, et al. Arterial Stiffness Is Associated With Cytomegalovirus-Specific Senescent CD8+ T Cells. J Am Heart Assoc 2017; 6. pmid:28847915
  31. 31. Cheng J, Ke Q, Jin Z, Wang H, Kocher O, Morgan JP, et al. Cytomegalovirus infection causes an increase of arterial blood pressure. PLoS Pathog 2009; 5:e1000427. pmid:19436702
  32. 32. Bolovan-Fritts CA, Trout RN, Spector SA. High T-cell response to human cytomegalovirus induces chemokine-mediated endothelial cell damage. Blood 2007; 110:1857–1863. pmid:17519388
  33. 33. Bolovan-Fritts CA, Spector SA. Endothelial damage from cytomegalovirus-specific host immune response can be prevented by targeted disruption of fractalkine-CX3CR1 interaction. Blood 2008; 111:175–182. pmid:17895402
  34. 34. Pachnio A, Ciaurriz M, Begum J, Lal N, Zuo J, Beggs A, et al. Cytomegalovirus Infection Leads to Development of High Frequencies of Cytotoxic Virus-Specific CD4+ T Cells Targeted to Vascular Endothelium. PLOS Pathog 2016; 12:e1005832. pmid:27606804
  35. 35. Pedersen KK, Pedersen M, Gaardbo JC, Ronit A, Hartling HJ, Bruunsgaard H, et al. Persisting inflammation and chronic immune activation but intact cognitive function in HIV-infected patients after long-term treatment with combination antiretroviral therapy. J Acquir Immune Defic Syndr 2013; 63:272–9. pmid:23392469
  36. 36. Pedersen KK, Manner IW, Seljeflot I, Kvale D, Os I, Gerstoft J, et al. Monocyte activation, but not microbial translocation, is independently associated with markers of endovascular dysfunction in HIV-infected patients receiving cART. J Acquir Immune Defic Syndr 2014; 67:370–4. pmid:25226210
  37. 37. Pedersen KK, Pedersen M, Trøseid M, Gaardbo JC, Lund TT, Thomsen C, et al. Microbial translocation in HIV infection is associated with dyslipidemia, insulin resistance, and risk of myocardial infarction. J Acquir Immune Defic Syndr 2013; 64:425–33. pmid:23797689
  38. 38. Pedersen KK, Eiersted MR, Gaardbo JC, Pedersen M, Gerstoft J, Troseid M, et al. Lower self-reported Quality of Life in HIV-infected patients on cART and with low co-morbidity compared to healthy controls. J Acquir Immune Defic Syndr Published Online First: 21 May 2015. pmid:26017659
  39. 39. Ballegaard V, Ralfkiaer U, Pedersen KK, Hove M, Koplev S, Brændstrup P, et al. MicroRNA-210, MicroRNA-331, and MicroRNA-7 are differentially regulated in treated HIV-1-infected individuals and are associated with markers of systemic inflammation. J Acquir Immune Defic Syndr 2017; 74. pmid:27749601
  40. 40. Pedersen M, Pedersen KK, Bruunsgaard H, Krabbe KS, Thomsen C, Færch K, et al. Cognitive Functions in Middle Aged Individuals Are Related to Metabolic Disturbances and Aerobic Capacity: A Cross-Sectional Study. PLoS One 2012; 7:e51132. pmid:23251434
  41. 41. WHO. Waist Circumference and Waist-Hip Ratio: Report of a WHO Expert Consultation. World Heal Organ 2008;:8–11.
  42. 42. James PA, Oparil S, Carter BL, Cushman WC, Dennison-Himmelfarb C, Handler J, et al. 2014 evidence-based guideline for the management of high blood pressure in adults: report from the panel members appointed to the Eighth Joint National Committee (JNC 8). JAMA 2014; 311:507–20. pmid:24352797
  43. 43. Franklin SS, Khan SA, Wong ND, Larson MG, Levy D. Is pulse pressure useful in predicting risk for coronary heart Disease? The Framingham heart study. Circulation 1999; 100:354–60. pmid:10421594
  44. 44. Maecker HT, Maino VC. Analyzing t-cell responses to cytomegalovirus by cytokine flow cytometry. Hum Immunol 2004; 65:493–499. pmid:15172449
  45. 45. Sylwester AW, Mitchell BL, Edgar JB, Taormina C, Pelte C, Ruchti F, et al. Broadly targeted human cytomegalovirus-specific CD4+ and CD8+ T cells dominate the memory compartments of exposed subjects. J Exp Med 2005; 202:673–85. pmid:16147978
  46. 46. Horton H, Thomas EP, Stucky JA, Frank I, Moodie Z, Huang Y, et al. Optimization and validation of an 8-color intracellular cytokine staining (ICS) assay to quantify antigen-specific T cells induced by vaccination. J Immunol Methods 2007; 323:39–54. pmid:17451739
  47. 47. Loeth N, Assing K, Madsen HO, Vindeløv L, Buus S, Stryhn A. Humoral and cellular CMV responses in healthy donors; identification of a frequent population of CMV-specific, CD4+ T cells in seronegative donors. PLoS One 2012; 7:e31420. pmid:22347475
  48. 48. Braendstrup P, Mortensen BK, Justesen S, Osterby T, Rasmussen M, Hansen AM, et al. Identification and HLA-tetramer-validation of human CD4+ and CD8+ T cell responses against HCMV proteins IE1 and IE2. PLoS One 2014; 9:e94892. pmid:24760079
  49. 49. Lachmann R, Bajwa M, Vita S, Smith H, Cheek E, Akbar A, et al. Polyfunctional T cells accumulate in large human cytomegalovirus-specific T cell responses. J Virol 2012; 86:1001–9. pmid:22072753
  50. 50. Bajwa M, Vita S, Vescovini R, Larsen M, Sansoni P, Terrazzini N, et al. Functional Diversity of Cytomegalovirus-Specific T Cells Is Maintained in Older People and Significantly Associated With Protein Specificity and Response Size. J Infect Dis 2016; 214:1430–1437. pmid:27521364
  51. 51. Abate D, Saldan A, Mengoli C, Fiscon M, Silvestre C, Fallico L, et al. Comparison of cytomegalovirus (CMV) enzyme-linked immunosorbent spot and CMV quantiferon gamma interferon-releasing assays in assessing risk of CMV infection in kidney transplant recipients. J Clin Microbiol 2013; 51:2501–7. pmid:23678073
  52. 52. Delforge ML, Desomberg L, Montesinos I. Evaluation of the new LIAISON ® CMV IgG, IgM and IgG Avidity II assays. J Clin Virol 2015; 72:42–45. pmid:26395519
  53. 53. Stone SF, Price P, Khan N, Moss PA, French MA. HIV patients on antiretroviral therapy have high frequencies of CD8 T cells specific for Immediate Early protein-1 of cytomegalovirus. AIDS 2005; 19:555–62. pmid:15802973
  54. 54. Kooij KW, Schouten J, Wit FWNM, van der Valk M, Kootstra NA, Stolte IG, et al. Difference in Aortic Stiffness Between Treated Middle-Aged HIV Type 1-Infected and Uninfected Individuals Largely Explained by Traditional Cardiovascular Risk Factors, With an Additional Contribution of Prior Advanced Immunodeficiency. J Acquir Immune Defic Syndr 2016; 73:55–62. pmid:27513572
  55. 55. Vlachopoulos C, Aznaouridis K, Stefanadis C. Prediction of Cardiovascular Events and All-Cause Mortality With Arterial Stiffness. J Am Coll Cardiol 2010; 55:1318–1327. pmid:20338492
  56. 56. Shirwany NA, Zou M. Arterial stiffness: a brief review. Acta Pharmacol Sin 2010; 31:1267–1276. pmid:20802505
  57. 57. Haider AW, Larson MG, Franklin SS, Levy D, Framingham Heart Study. Systolic blood pressure, diastolic blood pressure, and pulse pressure as predictors of risk for congestive heart failure in the Framingham Heart Study. Ann Intern Med 2003; 138:10–6. pmid:12513039
  58. 58. Youn J-C, Yu HT, Lim BJ, Koh MJ, Lee J, Chang D-Y, et al. Immunosenescent CD8+ T Cells and C-X-C Chemokine Receptor Type 3 Chemokines Are Increased in Human Hypertension. Hypertension 2013; 62:126–133. pmid:23716586
  59. 59. Kaplan RC, Sinclair E, Landay AL, Lurain N, Sharrett AR, Gange SJ, et al. T cell activation predicts carotid artery stiffness among HIV-infected women. Atherosclerosis 2011; 217:207–213. pmid:21492857
  60. 60. Kaplan RC, Sinclair E, Landay AL, Lurain N, Sharrett AR, Gange SJ, et al. T Cell Activation and Senescence Predict Subclinical Carotid Artery Disease in HIV-Infected Women. J Infect Dis 2011; 203:452–463. pmid:21220772
  61. 61. Karim R, Mack WJ, Kono N, Tien PC, Anastos K, Lazar J, et al. T-Cell Activation, Both Pre- and Post-HAART Levels, Correlates With Carotid Artery Stiffness Over 6.5 Years Among HIV-Infected Women in the WIHS. JAIDS J Acquir Immune Defic Syndr 2014; 67:349–356. pmid:25314253
  62. 62. De Socio G V., Ricci E, Maggi P, Parruti G, Pucci G, Di Biagio A, et al. Prevalence, Awareness, Treatment, and Control Rate of Hypertension in HIV-Infected Patients: The HIV-HY Study. Am J Hypertens 2014; 27:222–228. pmid:24077828
  63. 63. Freeman ML, Lederman MM, Gianella S. Partners in Crime: The Role of CMV in Immune Dysregulation and Clinical Outcome During HIV Infection. Curr HIV/AIDS Rep 2016; 13:10–19. pmid:26810437
  64. 64. Gianella S, Letendre S. Cytomegalovirus and HIV: A Dangerous Pas de Deux. J Infect Dis 2016; 214 Suppl:S67–74.
  65. 65. Li H, Margolick JB, Bream JH, Nilles TL, Langan S, Bui HT, et al. Heterogeneity of CD4+ and CD8+ T-cell Responses to Cytomegalovirus in HIV-Infected and HIV-Uninfected Men Who Have Sex With Men. J Infect Dis 2014; 210:400–404. pmid:24532602
  66. 66. Jacobson MA, Sinclair E, Bredt B, Agrillo L, Black D, Epling CL, et al. Antigen-specific T cell responses induced by Towne cytomegalovirus (CMV) vaccine in CMV-seronegative vaccine recipients. J Clin Virol 2006; 35:332–337. pmid:16387547