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Epigenetic clocks based on patterns of DNA methylation have great importance in understanding aging and disease; however, there are basic questions to be resolved in their application. It remains unknown whether epigenetic age acceleration (EAA) within an individual shows strong correlation between different primary tissue sites, the extent to which tissue pathology and clinical illness correlate with EAA in the target organ, and if EAA variability across tissues differs according to sex. Considering the outsized role of age-related illness in Human Immunodeficiency Virus-1 (HIV), these questions were pursued in a sample enriched for tissue from HIV-infected individuals. We used a custom methylation array to generate DNA methylation data from 661 samples representing 11 human tissues (adipose, blood, bone marrow, heart, kidney, liver, lung, lymph node, muscle, spleen and pituitary gland) from 133 clinically characterized, deceased individuals, including 75 infected with HIV. We developed a multimorbidity index based on the clinical disease history. Epigenetic age was moderately correlated across tissues. Blood had the greatest number and degree of correlation, most notably with spleen and bone marrow. However, blood did not correlate with epigenetic age of liver. EAA in liver was weakly correlated with EAA in kidney, adipose, lung and bone marrow. Clinically, hypertension was associated with EAA in several tissues, consistent with the multiorgan impacts of this illness. HIV infection was associated with positive age acceleration in kidney and spleen. Male sex was associated with increased epigenetic acceleration in several tissues. Preliminary evidence indicates that amyotrophic lateral sclerosis is associated with positive EAA in muscle tissue. Finally, greater multimorbidity was associated with greater EAA across all tissues. Blood alone will often fail to detect EAA in other tissues. While hypertension is associated with increased EAA in several tissues, many pathologies are associated with organ-specific age acceleration.

OBJECTIVE: To investigate HIV- and age- related differences in hip bone structure in men and women. DESIGN: Cross sectional study of bone structure and HIV serostatus. METHODS: We used Quantitative Computed Tomography (QCT) data from the Multicenter AIDS Cohort Study (MACS) and Women’s Interagency HIV Study (WIHS) to examine cortical thickness (CT) and cortical (CBMD), trabecular TBMD), and integral (IBMD) bone mineral density across anatomic quadrants of the femoral neck in older adult men who have sex with men (MSM) and women with (PWH) and without (PWOH) HIV infection. The percent difference (%diff) in the means for CT and BMD overall and by quadrant between PWH and PWOH were estimated. RESULTS: Among 322 MSM (median age 60 years) with bone measures, distributions were similar between HIV serostatus groups with %diff in the quadrant means ranging from −7% to −1% for CT and from −1% to 4% for BMD, and overall lower hip cortical thickness than expected. In contrast, in 113 women (median age 51 years), PWH had lower CT, IBMD and TBMD consistently across all quadrants, with differences ranging from −10 to −20% for CT, −6 to −11% for IBMD and −3 to −6% for TBMD. Estimates reached statistical significance in superoanterior quadrant for CT and IBMD and inferoposterior for CT. CONCLUSION: Among women, PWH appear to have a thinner cortex and less dense integral bone compared to PWOH, particularly in the superior quadrants while MSM overall had a thinner than expected hip cortex.

Background: Epigenetic aging is accelerated in tissues of persons living with HIV (PLWH) and may underlie the early onset of age-related illnesses. This study examines the rate-of-change in epigenetic age in PLWH following HIV infection but before HAART, using archived longitudinal samples from the Multicenter AIDS Cohort Study.Methods: DNA was isolated from cryopreserved peripheral blood mononuclear cells from 101 men living with HIV, with baseline visit Results: Epigenetic age increased approximately twice as fast in PLWH as uninfected controls (Pan-tissue, Extrinsic, and Phenotypic clocks). Shortening of DNAmTL was nearly 3-fold faster in PLWH than controls. Faster rate-of-aging was associated with HIV status (Pan-Tissue, Extrinsic, Phenotypic, and DNAmTL), white race (Extrinsic, DNAmTL), higher cumulative HIV viral load (Grim), and lower baseline DNAm age (Phenotypic, Skin & Blood).Conclusion: Epigenetic rates-of-aging were significantly faster for untreated PLWH. Our findings expand on the important impact of HIV infection on biologic aging, both in elevating epigenetic age and increasing the rate-of-aging in the years following infection.

A hallmark of HIV-1 infection is chronic inflammation. Chronic immune activation drives the pathogenesis of HIV-1 infection, leading to loss of CD4+ T cells and exhaustion of antiviral cellular immunity. Previously, we demonstrated that persistent inflammation mediated by type I interferon (IFN-I) signaling drives T cell exhaustion. Combination of anti-retroviral therapy (ART) and IFN-I receptor blockade therapy led to accelerated viral suppression and reduced latent HIV-1 reservoirs, suggesting that targeting type I IFN signaling can be used as a therapeutic strategy to alleviate T cell exhaustion. However, as IFN-Is are key regulators for antiviral immunity, more specific interventions to fine-tune IFN-I signaling and chronic inflammation are needed. Autophagy is a homeostatic mechanism for disposal of damaged cellular organelles and elimination of intracellular pathogens, which is pivotal for cellular homeostasis, T cell development and function. Autophagy is also impaired during HIV-1 infection. Here we demonstrate that autophagy is directly linked to IFN-I signaling. Impairment of autophagy leads to accumulation of damaged mitochondria and spontaneous IFN-I signaling. Autophagy inducers reduce IFN-I signaling in activated macrophages and restore functions of exhausted anti-HIV-1 T cells in vitro. Importantly, autophagy inducer treatment in HIV-1 infected humanized bone marrow/liver/thymus (BLT) mice significantly reduced persistent IFN-I signaling and immune activation, restored exhausted antiviral T cell responses, and accelerated viral suppression by ART. Autophagy inducer treatment also led to reduced viral rebound after ART withdrawal. Taken together, our data suggest that therapeutically targeting autophagy could be used to treat persistent immune activation and improve immune control of HIV replication.

Background: HIV-1 infection is associated with acceleration of age-related methylation patterns in peripheral blood and brain of infected individuals although the relative contributions of HIV-1 infection versus its treatment to the observed accelerations in biological aging have not yet been investigated.Methods: In this longitudinal study of the effects of antiretroviral therapy (ART) on epigenetic aging patterns, we extracted DNA from peripheral blood mononuclear cells from 15 HIV-1-infected individuals infected at three time points: 6 months-1year pre-ART, 6-12 months post-initiation of ART, and 18-24 months after initiating ART. We compared these trajectories with those of 15 age-matched uninfected control participants at three time points with similar intervals. Methylation studies were performed using the Infinium methylation 450 arrays. We examined four epigenetic clock measurements: Age acceleration residual (AAR), Extrinsic (EEAA), Phenotypic (PEAA), and Grim (GEAA) epigenetic age acceleration. Weighted correlation network (WGCNA) analysis was used to identify clusters of highly co-methylated CpGs.Results: We found that prior to the initiation of ART all four epigenetic measures were significantly higher in HIV-1-infected individuals compared with uninfected individuals (P

People with HIV (PWH) experience accentuated biological aging, as defined by markers of inflammation, immune dysfunction, and the epigenetic clock. They also have an elevated risk of multiple age-associated comorbidities. To discuss current knowledge, research gaps, and priorities in aging and age-related comorbidities in treated HIV infection, the NIH program staff organized a workshop held in Bethesda, Maryland in September 2019. This review article describes highlights of discussions led by the Pathogenesis/Basic Science Research working group that focused on three high priority topics: immunopathogenesis; the microbiome/virome; and aging and senescence. We summarize knowledge in these fields and describe key questions for research on the pathogenesis of aging and age-related comorbidities in PWH. Understanding the drivers and mechanisms underlying accentuated biological aging is a high priority that will help identify potential therapeutic targets to improve healthspan in older PWH.

Although CD31 expression on human thymocytes has been reported, a detailed analysis of CD31 expression at various stages of T cell development in the human thymus is missing. In this study, we provide a global picture of the evolution of CD31 expression from the CD34+ hematopoietic precursor to the CD45RA+ mature CD4+ and CD8+ single-positive (SP) T cells. Using nine-color flow cytometry, we show that CD31 is highly expressed on CD34+ progenitors and stays high until the early double-positive stage (CD3−CD4+CD8α+β−). After β-selection, CD31 expression levels become low to undetectable. CD31 expression then increases and peaks on CD3highCD4+CD8+ double-positive thymocytes. However, following positive selection, CD31 expression differs dramatically between CD4+ and CD8+ lineages: homogeneously high on CD8 SP but lower or negative on CD4 SP cells, including a subset of CD45RA+CD31− mature CD4+ thymocytes. CD31 expression on TCRγδ thymocytes is very similar to that of CD4 SP cells. Remarkably, there is a substantial subset of semimature (CD45RA−) CD4 SP thymocytes that lack CD31 expression. Moreover, FOXP3+ and ICOS+ cells are overrepresented in this CD31− subpopulation. Despite this CD31−CD45RA− subpopulation, most egress-capable mature CD45RA+ CD4 SP thymocytes express CD31. The variations in CD31 expression appear to coincide with three major selection processes occurring during thymopoiesis: β-selection, positive selection, and negative selection. Considering the ability of CD31 to modulate the TCR’s activation threshold via the recruitment of tyrosine phosphatases, our results suggest a significant role for CD31 during T cell development.

Supplemental Digital Content is available in the text, To assess the intra-individual and inter-individuals biological variation and the effect of aging on lymphocyte T-cells subsets. We assessed lymphocyte phenotypes (CD3+, CD4+, and CD8+ T-cells) in 89 HIV-1-infected and 88 uninfected white non-Hispanic men every 6 months, to examine the biological variation for those measurements, and the average change in lymphocyte phenotype over 34 years. The markers showed significant intra-individuality in HIV-infected and uninfected individuals with index of individuality of

Author(s): Schrack, Jennifer A; Althoff, Keri N; Jacobson, Lisa P; Erlandson, Kristine M; Jamieson, Beth D; Koletar, Susan L; Phair, John; Ferrucci, Luigi; Brown, Todd T; Margolick, Joseph B; Multicenter AIDS Cohort Study | Abstract: BackgroundGait speed predicts functional decline, disability, and death and is considered a biomarker of biological aging. Changes in gait speed in persons aging with HIV may provide an important method of gauging health and longevity in an under assessed population. The objective of this study was to evaluate and quantify the rate of gait speed decline in HIV-infected (HIV⁺) men compared with HIV-uninfected (HIV⁻) men.MethodsThe study was nested in the Multicenter AIDS Cohort Study. The primary outcome was usual gait speed in meters per second measured between 2007 and 2013. Differences in the rate of gait speed decline and the incidence of clinically slow gait (l1.0 m/s) were assessed using multivariate linear regression models and Cox proportional hazards models, respectively.ResultsA total of 2025 men (973 HIV⁺ and 1052 HIV⁻) aged 40 years and older contributed 21,187 person-visits (9955 HIV⁺ and 11,232 HIV⁻) to the analysis. Average gait speeds at the age 50 years were 1.24 and 1.19 m/s in HIV⁻ and HIV⁺ men, respectively (P l 0.001). In fully adjusted models, gait speed decline averaged 0.009 m/s per year after age 50 years (P l 0.001); this decline was 0.025 m/s per year greater in HIV⁺ men (P l 0.001). Moreover, HIV⁺ men had a 57% greater risk of developing clinically slow gait (adjusted hazard ratio = 1.57, 95% confidence interval: 1.27 to 1.91).ConclusionsThese findings indicate a faster rate of functional decline in HIV-infected men, suggesting greater risks of disability and death with advancing age.

BACKGROUND: Clinicians often use population-based reference intervals (RIs) when interpreting patient results. However, this method can present problems if the analyte in question has wide variability from person to person. METHODS: We examined the biological variation of routine hematologic markers in 82 white non-Hispanic men every 6 months during a 30-year period, to determine the usefulness of population-based RIs and age-related decline of hematological markers. RESULTS: Many of these markers showed significant person-to-person differences (index of individuality

BACKGROUND: Age-related gait speed decline is accelerated in men with human immunodeficiency virus (HIV). Mitochondrial genetic variation is associated with frailty and mortality in the general population and may provide insight into mechanisms of functional decline in people aging with HIV. METHODS: Gait speed was assessed semiannually in the Multicenter AIDS Cohort Study. Mitochondrial DNA (mtDNA) haplogroups were extracted from genome-wide genotyping data, classifying men aged ≥50 years into 5 groups: mtDNA haplogroup H, J, T, Uk, and other. Differences in gait speed by haplogroups were assessed as rate of gait speed decline per year, probability of slow gait speed (

A hallmark of human immunosenescence is the accumulation of late-differentiated memory CD8+ T cells with features of replicative senescence, such as inability to proliferate, absence of CD28 expression, shortened telomeres, loss of telomerase activity, enhanced activation, and increased secretion of inflammatory cytokines. Importantly, oligoclonal expansions of these cells are associated with increased morbidity and mortality risk in elderly humans. Currently, most information on the adaptive immune system is derived from studies using peripheral blood, which contains approximately only 2% of total body lymphocytes. However, most lymphocytes reside in tissues. It is not clear how representative blood changes are of the total immune status. This is especially relevant with regard to the human gastrointestinal tract (GALT), a major reservoir of total body lymphocytes (approximately 60%) and an anatomical region of high antigenic exposure. To assess how peripheral blood T cells relate to those in other locations, we compare CD8+ T cells from peripheral blood and the GALT, specifically rectosigmoid colon, in young/middle age, healthy donors, focusing on phenotypic and functional alterations previously linked to senescence in peripheral blood. Overall, our results indicate that gut CD8+ T cells show profiles suggestive of greater differentiation and activation than those in peripheral blood. Specifically, compared to blood from the same individual, the gut contains significantly greater proportions of CD8+ T cells that are CD45RA- (memory), CD28-, CD45RA-CD28+ (early memory), CD45RA-CD28- (late memory), CD25-, HLA-DR+CD38+ (activated) and Ki-67+ (proliferating); ex vivo CD3+ telomerase activity levels are greater in the gut as well. However, gut CD8+ T cells may not necessarily be more senescent, since they expressed significantly lower levels of CD57 and PD-1 on CD45RO+ memory cells, and had in vitro proliferative dynamics similar to that of blood cells. Compartment-specific age-effects in this cohort were evident as well. Blood cells showed a significant increase with age in proportion of HLA-DR+38+, Ki-67+ and CD25+ CD8+ T cells; and an increase in total CD3+ ex-vivo telomerase activity that approached significance. By contrast, the only age-effect seen in the gut was a significant increase in CD45RA- (memory) and concurrent decrease in CD45RA+CD28+ (naïve) CD8+ T cells. Overall, these results indicate dynamics of peripheral blood immune senescence may not hold true in the gut mucosa, underscoring the importance for further study of this immunologically important tissue in evaluating the human immune system, especially in the context of chronic disease and aging.

OBJECTIVE Grip strength predicts functional decline and death, and is regarded as a biomarker of biological aging. The primary objective of this manuscript was to assess differences in the rate of decline in grip strength in persons aging with and without HIV. DESIGN Grip strength was assessed in 1552 (716 HIV+ and 836 HIV-) men aged at least 50 years participating in the Multicenter AIDS Cohort Study between 2007 and 2014. METHODS Grip strength decline was modeled longitudinally, adjusting for serostatus, demographics, comorbidities, and conditions. In HIV-specific models, coefficients were included for cumulative viral load and history of AIDS. RESULTS Grip strength at the age of 50 years averaged 37.9 and 38.2 kg for HIV+ and HIV- men, respectively (P = 0.70). In fully adjusted models, grip strength declined 0.33 kg/year in HIV- men (P

The accumulation of peripheral blood late-differentiated memory CD8 T cells with features of replicative (cellular) senescence, including inability to proliferate in vitro, has been extensively studied. Importantly, the abundance of these cells is directly correlated with increased morbidity and mortality in older persons. Of note, peripheral blood contains only 2% of the total body lymphocyte population. By contrast, the gut-associated lymphoid tissue (GALT) is the most extensive lymphoid organ, housing up to 60% of total body lymphocytes, but has never been assessed with respect to senescence profiles. We report here the development of a method for measuring and comparing proliferative capacity of peripheral blood and gut colorectal mucosa-derived CD8 T cells. The protocol involves a 5-day culture of mononuclear leukocyte populations, from blood and gut colorectal mucosa respectively, labeled with 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2'-deoxyuridine (BrdU) and stimulated with anti-CD2/3/28-linked microbeads. Variables tested and optimized as part of the protocol development include: mode of T cell stimulation, CFSE concentration, inclusion of a second proliferation marker, BrdU, culture duration, initial culture concentration, and inclusion of autologous irradiated feeder cells. Moving forward, this protocol demonstrates a significant advance in the ability of researchers to study compartment-specific differences of in vitro proliferative dynamics of CD8 T cells, as an indicator of replicative senescence and immunological aging. The study's two main novel contributions are (1) Optimization and adaptation of standard proliferative dynamics blood T cell protocols for T cells within the mucosal immune system. (2) Introduction of the novel technique of combining CFSE and BrdU staining to do so.

Background Epigenetic biomarkers of aging (the “epigenetic clock”) have the potential to address puzzling findings surrounding mortality rates and incidence of cardio-metabolic disease such as: (1) women consistently exhibiting lower mortality than men despite having higher levels of morbidity; (2) racial/ethnic groups having different mortality rates even after adjusting for socioeconomic differences; (3) the black/white mortality cross-over effect in late adulthood; and (4) Hispanics in the United States having a longer life expectancy than Caucasians despite having a higher burden of traditional cardio-metabolic risk factors. Results We analyzed blood, saliva, and brain samples from seven different racial/ethnic groups. We assessed the intrinsic epigenetic age acceleration of blood (independent of blood cell counts) and the extrinsic epigenetic aging rates of blood (dependent on blood cell counts and tracks the age of the immune system). In blood, Hispanics and Tsimane Amerindians have lower intrinsic but higher extrinsic epigenetic aging rates than Caucasians. African-Americans have lower extrinsic epigenetic aging rates than Caucasians and Hispanics but no differences were found for the intrinsic measure. Men have higher epigenetic aging rates than women in blood, saliva, and brain tissue. Conclusions Epigenetic aging rates are significantly associated with sex, race/ethnicity, and to a lesser extent with CHD risk factors, but not with incident CHD outcomes. These results may help elucidate lower than expected mortality rates observed in Hispanics, older African-Americans, and women. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-1030-0) contains supplementary material, which is available to authorized users.

BACKGROUND The heterogeneity of CD4 T-cell counts and HIV-1 RNA at 5-12 years after the initiation of highly active antiretroviral therapy (HAART) remains largely uncharacterized. METHODS In the Multicenter AIDS Cohort Study, 614 men who initiated HAART contributed data 5-12 years subsequently. Multivariate regression was used to evaluate the predictors of CD4 counts and HIV-1 RNA levels. RESULTS At 5 to 12 years post-HAART, the median CD4 T-cell count was 586 (interquartile range, 421-791) cells per microliter and 78% of the HIV-1 RNA measurements were undetectable. Higher CD4 T-cell counts 5-12 years post HAART were predicted by higher CD4 T-cell counts and higher total lymphocyte count pre HAART, lack of hepatitis B or C virus coinfections, and greater CD4 T-cell change and suppressed HIV-1 RNA in the first 5 years after starting HAART. Men who were 50 years and older with 351-500 CD4 cells per microliter at HAART initiation had adjusted mean CD4 T-cell count of 643 cells per microliter at 10-12 years post HAART, which was similar to the adjusted mean CD4 T-cell count (670 cells/μL, P = 0.45) in this period for younger men starting HAART with lower CD4 T-cell counts. HIV-1 RNA suppression in the first 5 years post HAART predicted subsequent viral suppression. CONCLUSIONS Immunological and virological responses in the first 5 years post HAART predicted subsequent CD4 T-cell counts and HIV-1 RNA levels. The association between age and subsequent CD4 T-cell count supports incorporating age in the guidelines for use of HAART.

In the general population, frailty, a late stage of the aging process, predicts mortality. We investigated whether manifesting a previously defined frailty-related phenotype (FRP) before initiating highly active antiretroviral therapy (HAART) affects the likelihood of developing clinical AIDS or mortality after HAART initiation.Among 596 HIV-infected men in the Multicenter AIDS Cohort Study whose date of HAART initiation was known within ±6 months and who had an assessable FRP status within 3 years before HAART, survival analyses were performed to assess the effect of FRP manifestation on clinical AIDS or death after HAART.In men free of AIDS before HAART, AIDS or death after HAART occurred in 13/36 (36%) men who exhibited the FRP before HAART but only in 69/436 (16%) men who did not (hazard ratio = 2.6; 95% confidence interval = 1.4-4.6; p.01). After adjusting for age, ethnicity, education, nadir CD4+ T-cell count, peak HIV viral load, and hemoglobin in the 3 years before HAART, having the FRP at25% of visits in the 3 years before HAART significantly predicted AIDS or death (adjusted hazard ratio = 3.8; 95% confidence interval = 1.9-7.9; p.01). Results were unchanged when the analysis was restricted to the 335 AIDS-free men who were HAART responders, to the 124 men who had AIDS at HAART initiation, or to the subsets of men for whom indices of liver and kidney function could be taken into account.Having a persistent frailty-like phenotype before HAART initiation predicted a worse prognosis after HAART, independent of known risk factors.

Early HIV-1 infection is marked by rapid evolution of both CD8(+) T lymphocyte (CTL) epitope targeting and viral sequences, while chronic infection demonstrates relative stability of these parameters. To examine the interactions of changing CTL targeting and viremia in early infection, we assessed CTL targeting and viremia levels in persons during early HIV-1 infection (estimated 15-271 days post-infection) who were placed on effective antiretroviral therapy. Pre-therapy, CTL targeting of viral proteins varied between persons depending on time after infection. Across individuals, increasing time after infection was associated with increasing Gag and Pol targeting, suggesting increasing targeting of conserved sequences. The intensity of Gag targeting correlated to lower viremia levels, while Env targeting correlated to higher viremia levels during early infection. This suggested that shifted targeting towards more conserved sequences is involved with the drop of viremia during early infection, consistent with prior observations of correlation between Gag targeting and lower viremia during chronic infection. After suppressive antiretroviral therapy, CTL targeting was generally static, indicating that HIV-1 replication and evolution drives the evolution of CTL targeting in early infection. Overall, these data suggest that early CTL targeting is directed towards more variable epitopes, causing escape and re-targeting until more conserved epitopes are recognized stably in chronic infection. Circumventing this natural history by pre-targeting CTL against more conserved epitopes with a vaccine could minimize the initial period of viral escape and immune damage during acute infection, improving long-term containment of HIV-1.

The presence of antibody to R7V (anti-R7VAb), a seven-amino acid sequence derived from beta(2)-microglobulin incorporated into HIV-1 virions from the surface of infected cells, has been proposed as an early marker of nonprogressive HIV-1 infection. The present study was undertaken because no prospective studies have tested this hypothesis. Stored samples collected prospectively from 361 HIV-1 seroconverting men in the Multicenter AIDS Cohort Study (0.44-1.53 years after seroconversion) were assayed for the presence or absence of anti-R7VAb, using a standardized ELISA. Using Cox proportional hazards models, crude and adjusted relative hazards (RH) were determined for the following outcomes: (a) clinically defined AIDS, (b) clinically defined AIDS or CD4 T cell count of200 cells/microl, and (c) death. A total of 143 (39.6%) men had early anti-R7VAb and 218 (60.4%) did not; 192 (53.2%) developed AIDS. At the visit tested, men with anti-R7VAb had significantly lower CD4 T cell counts and higher plasma HIV-1 viral loads than those without antibody. After adjustment for CD4 T cell count, HIV-1 viral load, CCR5 polymorphism, and use of combined antiretroviral therapy, the presence of anti-R7VAb was associated with a higher risk of progression for all outcomes, but not significantly so. Absence of anti-R7VAb was significantly associated with expression of HLA-B*5701 and -B*2705, two alleles associated with slower progression of HIV-1 disease. The early presence of anti-R7VAb in HIV-1 seroconverters was not associated with slower progression of HIV-1 disease.

Telomerase reverse transcribes telomere DNA onto the ends of linear chromosomes and retards cellular aging. In contrast to most normal somatic cells, which show little or no telomerase activity, immune cells up-regulate telomerase in concert with activation. Nevertheless, during aging and chronic HIV-1 infection, there are high proportions of dysfunctional CD8+ CTL with short telomeres, suggesting that telomerase is limiting. The present study shows that exposure of CD8+ T lymphocytes from HIV-infected human donors to a small molecule telomerase activator (TAT2) modestly retards telomere shortening, increases proliferative potential, and, importantly, enhances cytokine/chemokine production and antiviral activity. The enhanced antiviral effects were abrogated in the presence of a potent and specific telomerase inhibitor, suggesting that TAT2 acts primarily through telomerase activation. Our study is the first to use a pharmacological telomerase-based approach to enhance immune function, thus directly addressing the telomere loss immunopathologic facet of chronic viral infection.

To infect cells, HIV-1 must bind to both the CD4 protein and another transmembrane “coreceptor.” Early in the course of disease, HIV-1 variants usually bind to the chemokine coreceptor CCR5; such variants are termed “R5 viruses.” Viruses using another chemokine coreceptor, CXCR4, termed “X4 viruses,” emerge later in disease progression in ~50% of individuals infected with clade B virus [1], although a higher percentage has been suggested on the basis of studies that used sensitive detection techniques [2]. The presence of X4 viruses has been associated with accelerated disease progression and a decrease in CD4+ T cells [3, 4], but despite descriptions of in vitro cytopathicity of X4 viruses [5-7], no causal in vivo relationship or mechanism for this association has been proven [8, 9]. In 3 studies of coreceptor evolution during untreated HIV-1 infection [3, 4, 10], X4 viruses tended to emerge just before the beginning of the decrease in the total (CD3+) T cell count (i.e., the CD3+ inflection point) that presages the onset of an AIDS-defining illness [11]. The ability of HIV-1 to bind to CXCR4 may facilitate destruction of naive T cells, which preferentially express CXCR4 as opposed to CCR5 [8], and thus may contribute to more rapid depletion of T cells. The uncertainty surrounding mechanisms of selection and evolution of X4-using HIV-1 and the inability to predict the emergence of these strains have taken on greater importance since the development of CCR5 antagonists as inhibitors of HIV-1 replication [12,13]. For example, in a recent study of monotherapy with a CCR5 antagonist, X4 viruses present in low amounts replaced the R5 population shortly after commencement of therapy [14]. This has led to concern that use of CCR5 antagonists may predispose to selection of CXCR4-tropic viruses and, thus, to faster progression of HIV-1 disease than would occur without blockade of CCR5. To further characterize the emergence of X4 strains during HIV-1 infection, we undertook a systematic analysis of HIV-1 coreceptor tropism in men from the Multicenter AIDS Cohort Study (MACS; study Web site available at: http://www.statepi.jhsph.edu/macs/macs.html) who were selected for this study in order to reflect the full spectrum of rates of HIV-1 disease progression. Our specific goals were to evaluate (1) the timing of X4 virus emergence with respect to CD3+ T cell decline and development of an AIDS-defining event, (2) the degree to which emergence of X4 viruses correlates with an increased risk of rapid disease progression, and (3) whether determination of the CD4+ T cell count can be an accurate screen for detectable levels of CXCR4-tropic viruses.

Mucosal immune responses induced by HIV-1 vaccines are likely critical for prevention. We report a Phase 1 safety and immunogenicity trial in eight participants using the vaccinia-based TBC-3B vaccine given subcutaneously to determine the relationship between HIV-1 specific systemic and gastrointestinal mucosal responses. Across all subjects, detectable levels of blood vaccinia- and HIV-1-specific antibodies were elicited but none were seen mucosally. While the vaccinia component was immunogenic for CD8 + T lymphocyte (CTL) responses in both blood and mucosa, it was greater in blood. The HIV-1 component of the vaccine was poorly immunogenic in both blood and mucosa. Although only eight volunteers were studied intensively, the discordance between mucosal and blood responses may highlight mechanisms contributing to recent vaccine failures. © 2008 Elsevier Ltd. All rights reserved.

Background. Older healthy and HIV-infected adults exhibit physiological similarities. Frailty is a clinical syndrome associated with aging that identifies a subset of older adults at high risk of mortality and other outcomes. We investigated whether HIV infection increases the prevalence of a frailty-related phenotype (FRP) that approximates a clinical definition of frailty. Methods. We first defined the FRP and assessed its prevalence among HIV-uninfected men followed in the Multicenter AIDS Cohort Study (MACS) between 1994 and 2004. Using repeated measurements logistic regression models, we then assessed the association between FRP and HIV infection before the era of highly active antiretroviral therapies, adjusting for covariates among HIV-uninfected (N ¼ 1905) and incident HIV cases (N ¼ 245). Results. HIV infection was strongly associated with FRP prevalence. Compared to HIV-uninfected men of similar age, ethnicity and education, HIV-infected men were more likely to have the FRP for all durations of infection: for � 4 years, the adjusted odds ratio (OR) was 3.38, with 95% confidence interval (CI), 1.25‐9.11, and for 4.01‐8 years and 8.01‐12 years the corresponding figures were (OR ¼ 12.95, 95% CI, 6.60‐25.40) and (OR ¼ 14.68, 95% CI, 7.60‐28.35), respectively. The FRP prevalence for 55-year-old men infected with HIV for � 4 years (3.4%; 95% CI, 1.3‐8.6) was similar to that of uninfected men � 65 years old (3.4%; 95% CI, 1.5‐7.6). Conclusion. In this cohort, HIV infection was associated with an earlier occurrence of a phenotype that resembles the phenotype of frailty in older adults without HIV infection. Studies of frailty in the setting of HIV infection may help to clarify the biological mechanism of frailty.

This protocol describes a rapid and simple method for the identification of apoptotic cells. Owing to changes in membrane permeability, early apoptotic cells show an increased uptake of the vital DNA dye Hoechst 33342 (HO342) compared with live cells. The nonvital DNA dye 7-amino-actinomycin D (7-AAD) is added to distinguish late apoptotic or necrotic cells that have lost membrane integrity from early apoptotic cells that still have intact membranes as assayed by dye exclusion. The method is suitable to be combined with cell surface staining using Abs of interest labeled with fluorochromes that are compatible with HO342 and 7-AAD emissions. Surface antigen staining is carried out according to standard methods before staining for apoptosis. The basic assay can be completed in 30 min, and extra time is needed for cell surface antigen staining.

Decline in the number of CD4+ T-cells and expansion of CD8+ T-cells are hallmarks of HIV-1 disease progression. The most widely used method for quantifying T-cells in HIV-1 infection is flow cytometry. Many technical factors affect flow cytometry-based immunophenotyping results, including flow cytometer quality control, specimen age, antibodies used, method of sample preparation, and analytical/gating procedures (1–5). Given the numerous variables, it is critical that all sites generating flow cytometry data be monitored for proficiency in terms of accuracy and precision both within and between laboratories, especially for multi-center studies. The National Institute of Allergy and Infectious Diseases, Division of AIDS (DAIDS), has developed such a program, the Immunological Quality Assessment (IQA) Program, which is sponsored by DAIDS and administered by the New Jersey School of Medicine and Dentistry (3). All laboratories generating flow cytometry data for NIH studies are required to participate in this program and to maintain satisfactory performance in it. The IQA sends matched blood samples to all participating laboratories and then analyzes and summarizes their results according to specific statistical criteria. To evaluate inter- and intralaboratory performance, the T-cell results for each sample are compared with the median T-cell value for all laboratories reporting results for that sample. Values that differ from the median by 4% or less are considered acceptable. Intralaboratory performance is tested with blinded replicates sent to each laboratory and performance is considered acceptable if the range is within 3%. DAIDS has taken a strong, central role in directing flow cytometry laboratories to utilize improved methodologies with published guidelines for appropriate methods to perform CD4 enumeration in HIV infected individuals (2–4), and is an advocate for their adoption. In January, 2001, the DAIDS IQA Flow Cytometry Advisory Committee recommendations called for the use of CD45 gating for CD4 and CD8 immunophenotyping, based on the increased precision of lymphocyte gating strategies utilizing CD45 vs. right angle scatter rather than light scatter properties only (1,2,4). Laboratories using the CD3/CD4 and CD3/CD8 antibody combinations were required to begin using either CD3/CD4/CD45 and CD3/CD8/CD45 (3-color) or CD3/CD8/CD45/CD4 (4-color) combinations. However, laboratories could switch to the new method only after successfully completing a “switch” study involving the direct comparison of the old and new methods and obtaining approval from the IQA Advisory Committee. The switch study requires that 60 patient specimens with a CD4 percentage of ≤30% [by the 2-color method (4)] be tested by both the old and the new method. To “pass” the switch study, differences between the results must be within targeted ranges. Based on these evaluations, laboratories have been either certified to switch to the new method or, if the two methods did not agree sufficiently, required to repeat the evaluation. This report is based on the experience of the Multicenter AIDS Cohort Study (MACS) laboratories performing switch studies to transition from a 2-color to a 3-color T-cell immunophenotyping methodology. When two of the four MACS flow cytometry laboratories (which were certified for two-color analyses) repeatedly failed the required switch study, approval was sought and received to adopt the new (3-color, lyse no-wash) method despite the failures. This adoption resulted in more precise laboratory performance at these sites, suggesting that under certain circumstances a rigid requirement to repeat a failed switch study may be counterproductive. Based on this experience, we offer two possible alternatives to the current requirement of having to repeat a failed switch study, in an effort to increase the speed and efficiency of adopting new technologies.

Human immunodeficiency virus type 1 (HIV-1) evolves in vivo under selective pressure from CD8 + T-lymphocyte (CTL) responses, which are in turn determined by host and viral genetic factors, such as restricting major histocompatibility complex molecules and the available viral epitope sequences. However, CTL are derived stochastically through the random gene rearrangements to produce T-cell receptors (TCR), and the relative impact of genetic versus stochastic processes on CTL targeting of HIV and immune-driven viral evolution is unclear. Here we evaluate identical twins infected with HIV-1 as neonates from a common blood transfusion, with subsequently similar environmental exposures, thereby allowing controlled comparisons of CTL targeting and viral evolution. Seventeen years after infection, their CTL targeting of HIV-1 was remarkably similar. In contrast, their overall TCR profiles were highly dissimilar, and a dominant epitope was recognized by distinctly different TCR in each twin. Furthermore, their viral epitopes had diverged, and there was ongoing viral phylogenetic divergence between the twins between 12 and 17 years after infection. These results indicate that while CTL targeting is predominately genetically determined, stochastic influences render the interaction of HIV-1 and host immunity, and therefore viral escape and CTL efficacy, unpredictable.

Live attenuated HIV vaccines offer a means to introduce exogenous sequences into the viral genome to target the virus elimination in vivo. Foreign genes inserted into the nef region of HIV-1 NL4-3 were found to be rapidly deleted following virus infection and/or replication, in a size dependent manner, in the human fetal Thymus/Liver implants of severe combined immunodeficient mouse (SCID-hu) model. When the murine heat stable antigen (HSA) of 283 bp was substituted into HIV-1 nef region, the viral loads in vivo were comparable to the negative control nef attenuated HIV-1, and the reporter HSA gene was not deleted upon infection. However, the murine Thy1.2 gene (505 bp) substituted into the nef attenuated HIV-1, upon infection and replication, deleted 441 bp in vitro and 437 bp in vivo, of the inserted Thy1.2 gene. When the enhanced green fluorescence protein (eGFP) gene (720 bp) was substituted for nef, virus replication was aborted in vivo in the Thy/Liv implants, as seen by the background levels of viral loads, comparable to mock infected implants, and the eGFP gene was deleted. When the herpes simplex virus thymidine kinase gene, HSV-TK (1.15 kbp), or HSA gene, was substituted into the viral vpr gene, TK but not HSA gene was deleted, upon infection in vitro. Moreover, NL-TKI reporter virus with both intact nef and vpr genes shows deletion of TK gene both in vitro and in vivo. Excision of foreign genes occurred within the exogenous segments but not in the viral own regions. These results suggest that larger "suicide" genes introduced via HIV-1 can be deleted upon infection. However, smaller size nucleotide sequences or genes (approximately 300 bp) inserted in place of viral nef or vpr gene may be used to target the virus or its components, for attack and elimination in vivo, and thus have implications for the development of live attenuated HIV vaccines.

Objective: Although the epitopic breadth of HIV-1-specific CD8 T lymphocyte (CTL) responses has been described, the T cell receptor (TCR) diversity of virus-specific cells remains poorly defined. Design and methods: To address this issue, we applied a novel technique for subtractive analysis of the HIV-1-specific CTL repertoire, combining specific deletion of peptide-specific cells by 5-fluorouracil with TCR spectratyping to identify clonal breadth of CTL recognizing individual peptides. Results: Comprehensive analysis of an infected individual reveals that nine identified HIV-1-specific responses are comprised of at least 38 distinct T-cell clones (ranging from two to 10 distinct clones per epitope). Conclusion: Given the potentially crucial role of T-cell receptor breadth for viral recognition and avoidance of escape, this subepitopic analysis of CTL may offer an important measure of cellular immunity for pathogenesis and vaccine studies.

OBJECTIVE We examined the association between immunogenic exposure and T-cell receptor (TCR) diversity to more clearly assess the impact of HIV-1 infection on the T-cell repertoire. METHODS : To estimate the extent of T-cell clonality attributable to HIV-1 infection, we evaluated T-cell repertoires in low-risk and at-risk seronegative men and HIV-1 seropositive men by assessment of T-cell receptor beta-chain (TCR beta) complimentary determining region 3 (CDR3) lengths. RESULTS The frequency of T-cell clonality in both HIV-1 infected and at-risk uninfected men was elevated in comparison to low-risk uninfected men. Among low-risk and at-risk seronegative, and HIV-1 seropositive men, clonal expansions were present in 3, 8, and 10% of CD4+ CDR3 lengths, and 18, 22, and 28% of CD8+ CDR3 lengths respectively. In addition, the longitudinal conservation of clonal expansions was observed in at-risk seronegative men. Based on comparisons to at-risk seronegative men, we estimate that at-risk seropositive men with chronic HIV-1 infection exhibit a 27% increase in the number of expanded CD8+ CDR3 lengths. CONCLUSION These findings provide an approximation of the magnitude of the T-cell response in individuals undergoing chronic HIV-1 infection and demonstrate a significant association between the history of immunogenic challenge and the magnitude of clonality within the T-cell repertoire. In addition, these findings underscore the necessity of selecting controls with similar antigenic exposure histories when investigating T-cell dynamics in HIV-infected individuals.

Summary Background Eosinophils play a central role in asthma, but the interplay of the effects of smoking, eosinophils and asthma remains unclear. Objective The primary objective of our study was to investigate the extent to which smoking modifies the effect of asthma on circulating eosinophils, CD4+ and CD8+ T cell counts. Methods Data were collected semiannually between 1987 and 1994 from HIV-negative participants in the Multicenter AIDS Cohort Study. Asthma was defined by a questionnaire at baseline as a self-report of diagnosed asthma. A total of 1420 blood samples from 197 asthmatics and 15 822 from 1997 non-asthmatics were collected. Results Eosinophil levels were higher in asthmatics (28% of asthmatics had eosinophils 4% and 16% of non-asthmatics) regardless of smoking history, but smoking modified the association between eosinophils and asthma. Namely, the odds ratios for eosinophils being 4% in asthmatics to non-asthmatics decreased from 2.7 (95% CI: 2.0, 3.6) in never, to 2.1 (1.4, 3.1) in former, and to 1.5 (0.9, 2.3) in current smokers. Cross-sectional and longitudinal analyses coherently showed that smoking increased eosinophils in non-asthmatics, but the converse was true for asthmatics. In contrast, no differences in peripheral blood T cell counts between asthmatics and non-asthmatics were observed. Conclusion Under the established link between increased eosinophils and asthma, these data indicate that smoking modified this relationship. This finding suggests that smoking plays a different immunological role in asthmatics and non-asthmatics.

Nef is an HIV-1 protein that is absent in most retroviruses, yet its reading frame is highly maintained despite frequent targeting by CD8+ CTL in vivo. Because Nef is not necessarily required for viral replication, this consistent maintenance suggests that Nef plays an important role(s) and substantial fitness constraints prevent its loss in vivo. The ability of Nef to down-regulate cell surface MHC class I (MHC-I) molecules and render infected cells resistant to CTL in general is likely to be an important contributing function. We demonstrate that mutational escape of HIV-1 from Nef-specific CTL in vitro leads to progeny virions that are increased in their susceptibility to CTL of specificities for proteins other than Nef. The escape mutants contain multiple nef mutations that impair the ability of the virus to down-regulate MHC-I through disruption of its reading frame as well as epitope point mutations. Given the rarity of nef frameshifts in vivo, these data support the concept that the ability to down-regulate MHC-I could be a key constraint for preservation of Nef in vivo.

The majority of HIV-1 infections occur via sexual transmission at mucosal epithelia lining the vagina, cervix or rectum. Mucosal tissues also serve as viral reservoirs. However, our knowledge of human mucosal T-cell responses is limited. There is a need for reliable, sensitive, and reproducible methods for assessing mucosal immunity. Here we report on the collaborative efforts of two laboratories to optimize methods for processing, culturing, and analyzing mucosal lymphocytes. Rectal biopsy tissue was obtained by flexible sigmoidoscopy, which is rapid, minimally invasive, and well tolerated. Of the four methods compared for isolating mucosal mononuclear cells (MMC), collagenase digestion reproducibly yielded the most lymphocytes (4-7 x 10(6)). Furthermore, 0.5-1 x 10(6) MMC could be polyclonally expanded to yield 17 x 10(6) CD8+ T cells allowing mapping of responses to overlapping peptides spanning the HIV-1 genome using IFN-gamma enzyme-linked immunospot (ELISpot). Expansion also reduced the spontaneous IFN-gamma production normally detected in fresh MMC. Piperacillin-tazobactam and amphotericin B reduced contamination of MMC cultures to 4%. Taken together, these methods will be useful for studies of mucosal immunity to HIV-1 and other pathogens during natural infection and following vaccination.

OBJECTIVE: To examine temporal variation in the effects of CCR5-Delta32 and CCR2-64I chemokine receptor gene polymorphisms on HIV-1 disease progression. DESIGN: Pooled analysis of individual patient data from 10 cohorts of HIV-1 seroconverters from the United States, Europe, and Australia. METHODS: We studied HIV-1 seroconverters of European (n = 1635) or African (n = 215) ancestry who had been genotyped for CCR5-Delta32 and CCR2-64I. We used Cox proportional hazards models with time-varying coefficients to determine whether the genetic protection against AIDS (1987 case definition) and death varied with time since seroconversion. RESULTS: Protection against AIDS conferred by CCR5-Delta32 held constant at a 31% (RH 0.69, 95% CI 0.54, 0.88) reduction in risk over the course of HIV-1 infection, whereas protection against death held constant at a 39% reduction in risk (RH 0.61, 95% CI 0.45, 0.88). When the period from AIDS to death was isolated, the survival benefit of CCR5-Delta32 diminished 2 years after AIDS. Protection against AIDS conferred by CCR2-64I was greatest early in the disease course. Compared with individuals without CCR5-Delta32 or CCR2-64I, individuals with one or two copies of CCR2-64I had a 58% lower risk of AIDS during the first 4 years after seroconversion (RH 0.42, 95% CI 0.23, 0.76), a 19% lower risk during the subsequent 4 years (RH 0.81, 95% CI 0.59, 1.12), and no significant protection thereafter. CONCLUSION: The protection against AIDS provided by CCR5-Delta32 is continuous during the course of infection. In contrast, the protection provided by CCR2-64I is greatest early in the course of infection

The host immune factors that determine susceptibility to HIV-1 infection are poorly understood. We compared multiple immunologic parameters in three groups of HIV-1-seronegative men: 14 highly exposed (HR10), 7 previously reported possibly to have sustained transient infection (PTI), and a control group of 14 low risk blood bank donors (BB). Virus-specific cellular immune assays were performed for CD4(+) T helper cell responses, CD8(+) cytotoxic T lymphocyte activity, CD8(+) cell chemokine release, and CD8(+) cell-derived antiviral soluble factor activity. General immune parameters evaluated included CCR5 genotype and phenotype, interferon alpha production by PBMCs, leukocyte subset analysis, and detailed T lymphocyte phenotyping. Comparisons revealed no detectable group-specific differences in measures of virus-specific immunity. However, the HR10 group differed from the BB group in several general immune parameters, having higher absolute monocyte counts, higher absolute CD8(+) T cell counts and percentages, lower naive and higher terminal effector CD8(+) cells, and lower levels of CD28(+)CD8(+) cells. These changes were not associated with seropositivity for other chronic viral infections. The PTI men appeared to have normal levels of monocytes and slightly elevated levels of CD8(+) T cells (also with increased effector and decreased naive cells). Although we cannot entirely exclude the contribution of other chronic viral infections, these findings suggest that long-lived systemic cellular antiviral immunity as detected by our assays is not a common mechanism for resistance to infection, and that resistance may be multifactorial. General immune parameters reflected by CD8(+) T cell levels and activation, and monocyte concentrations may affect the risk of infection with HIV-1, and/or serve as markers of exposure.

T-cell receptor diversity enables the cellular immune response to recognize a broad range of viral and other pathogenic agents. An increasingly common method of characterizing T-cell receptor diversity and usage in response to antigenic challenges involves the identification of clonal expansions by PCR amplification of the CDR3 region of distinct TCRVβ families. Though clonal expansions often appear evident upon visual inspection of the results, a systematic method is needed for the valid enumeration of these expansions. Here, we describe a novel analysis method, termed the MaGiK method, for systematically identifying and enumerating clonal T-cell expansions and for applying the results to investigations of the T-cell receptor repertoire.

Epidemiologic studies have identified cocaine as a cofactor for development of acquired immunodeficiency syndrome (AIDS). To evaluate this interaction, human peripheral blood leukocytes (PBL) were implanted into severe combined immunodeficient mice and infected with human immunodeficiency virus (HIV) in both the presence and absence of cocaine. Concurrent administration of cocaine resulted in significantly more PBL becoming infected with HIV in vivo (38.85% vs. 18.5%). The number of CD4(+) cells recovered from HIV-infected, cocaine-treated animals was significantly lower than that from mice infected with HIV in the absence of cocaine (6.5 x 10(4) vs. 19 x 10(4)) and was associated with a lower CD4:CD8 ratio and a dramatic increase in virus load. Exposure to cocaine alone did not affect the implantation of PBL, suggesting a specific interaction between cocaine and HIV. This report describes a model for evaluating HIV cofactors and supports cocaine's role in the development and progression of AIDS.

© 2015 Rickabaugh et al. Patients with treated HIV-1-infection experience earlier occurrence of aging-associated diseases, raising speculation that HIV-1-infection, or antiretroviral treatment, may accelerate aging. We recently described an age-related co-methylation module comprised of hundreds of CpGs; however, it is unknown whether aging and HIV-1-infection exert negative health effects through similar, or disparate, mechanisms. We investigated whether HIV-1-infection would induce age-associated methylation changes. We evaluated DNA methylation levels at >450,000 CpG sites in peripheral blood mononuclear cells (PBMC) of young (20-35) and older (36-56) adults in two separate groups of participants. Each age group for each data set consisted of 12 HIV-1-infected and 12 age-matched HIV-1-uninfected samples for a total of 96 samples. The effects of age and HIV-1 infection on methylation at each CpG revealed a strong correlation of 0.49, p-200 and 0.47, p-200. Weighted gene correlation network analysis (WGCNA) identified 17 co-methylation modules; module 3 (ME3) was significantly correlated with age (cor=0.70) and HIV-1 status (cor=0.31). Older HIV-1+ individuals had a greater number of hypermethylated CpGs across ME3 (p=0.015). In a multivariate model, ME3 was significantly associated with age and HIV status (Data set 1: βage= 0.007088, p=2.08 × 10-9; βHIV= 0.099574, p=0.0011; Data set 2: βage= 0.008762, p=1.27× 10-5; βHIV= 0.128649, p= 0.0001). Using this model, we estimate that HIV-1 infection accelerates age-related methylation by approximately 13.7 years in data set 1 and 14.7 years in data set 2. The genes related to CpGs in ME3 are enriched for polycomb group target genes known to be involved in cell renewal and aging. The overlap between ME3 and an aging methylation module found in solid tissues is also highly significant (Fisher-exact p=5.6 × 10-6, odds ratio=1.91). These data demonstrate that HIV-1 infection is associated with methylation patterns that are similar to age-associated patterns and suggest that general aging and HIV-1 related aging work through some common cellular and molecular mechanisms. These results are an important first step for finding potential therapeutic targets and novel clinical approaches to mitigate the detrimental effects of both HIV-1-infection and aging.

The foregoing introduction to the epidemiology of aging in HIV-1 infection leads us to an important preliminary conclusion. That is, the study of older age in HIV-1 infection is more properly considered as (i) the study of a population of newly infected older individuals and (ii) the study of a separate group of long-term HIV-1-infected patients successfully treated with highly active antiretroviral (ARV) therapy (HAART). The authors used a generalized linear models approach with age category, HIV-1 disease category (HIV-1 seronegative, CDC stage B/early symptomatic HIV-1 infection, and CDC stage C/AIDS), and their interaction as predictors of the total number of MCMD symptoms (zero to six) defined by the American Academy of Neurology. Given the hypercortisolemia-induced neuronal cellular toxicity associated with major depressive disorder and with chronic stressor exposure, both of these conditions may enhance the likelihood of neurocognitive impairment (NCI) and neurocognitive disorder when superimposed upon the toxicities associated with the aging process and HIV-1 infection of the brain. In addition to the consideration of how aging might interact with HIV-1 infection in specific neuro-AIDS conditions, an overarching issue exists. That issue is related to how an increased frequency of medical comorbidities might interact with aging in the likelihood of expression of neuro-AIDS conditions.

Combined analysis of DNA content and immunofluorescence on single cells by flow cytometry provides information on the proliferative response of cellular sub-populations in mixed cell preparations. However, the presence of considerable numbers of dead (nonviable) cells impairs accurate flow cytometric data analysis, mainly, because dead cells can bind antibodies non-specifically and show alterations in their DNA staining profiles. We developed a rapid method for identification of dead cells by fluorescence in cell preparations that are stained simultaneously for two-color immunofluorescence and DNA content. Cells are stained with 7-aminoactinomycin D (7-AAD) for dead cell discrimination and with fluorescein-isothiocyanate (FITC) and phycoerythrin (PE)-labeled monoclonal antibodies (mAb) for cell surface immunofluorescence. Diffusion of 7-AAD from stained, dead cells into unstained, live cells after cell permeabilization is blocked by the addition of its non-fluorescent analogue actinomycin D (AD). DNA is stained with red-excitable TO-PRO-3 iodide (TP3) which has an emission spectrum that can be effectively separated from the emissions of FITC, PE, and 7-AAD. TP3 staining is performed in the presence of ribonuclease A (RNAse) in phosphate-citrate buffer containing saponin (PCBS) at low pH. FITC fluorescence is sensitive to acid pH; therefore, PCBS is replaced after DNA staining with 1x PBS at pH 7.2 containing saponin to permit accurate detection of FITC immunofluorescence on the flow cytometer. We apply this method to the analysis of differential proliferation of lymphocyte subsets in cultures of human peripheral blood mononuclear cells (PBMC) with low viability.