Reduced and highly diverse peripheral HIV-1 reservoir in virally suppressed patients infected with non-B HIV-1 strains in Uganda.

BACKGROUND: Our understanding of the peripheral human immunodeficiency virus type 1 (HIV-1) reservoir is strongly biased towards subtype B HIV-1 strains, with only limited information available from patients infected with non-B HIV-1 subtypes, which are the predominant viruses seen in low- and middle-income countries (LMIC) in Africa and Asia. RESULTS: In this study, blood samples were obtained from well-suppressed ART-experienced HIV-1 patients monitored in Uganda (n = 62) or the U.S. (n = 50), with plasma HIV-1 loads < 50 copies/ml and CD4+ T-cell counts > 300 cells/ml. The peripheral HIV-1 reservoir, i.e., cell-associated HIV-1 RNA and proviral DNA, was characterized using our novel deep sequencing-based EDITS assay. Ugandan patients were slightly younger (median age 43 vs 49 years) and had slightly lower CD4+ counts (508 vs 772 cells/ml) than U.S. individuals. All Ugandan patients were infected with non-B HIV-1 subtypes (31% A1, 64% D, or 5% C), while all U.S. individuals were infected with subtype B viruses. Unexpectedly, we observed a significantly larger peripheral inducible HIV-1 reservoir in U.S. patients compared to Ugandan individuals (48 vs. 11 cell equivalents/million cells, p < 0.0001). This divergence in reservoir size was verified measuring proviral DNA (206 vs. 88 cell equivalents/million cells, p < 0.0001). However, the peripheral HIV-1 reservoir was more diverse in Ugandan than in U.S. individuals (8.6 vs. 4.7 p-distance, p < 0.0001). CONCLUSIONS: The smaller, but more diverse, peripheral HIV-1 reservoir in Ugandan patients might be associated with viral (e.g., non-B subtype with higher cytopathicity) and/or host (e.g., higher incidence of co-infections or co-morbidities leading to less clonal expansion) factors. This highlights the need to understand reservoir dynamics in diverse populations as part of ongoing efforts to find a functional cure for HIV-1 infection in LMICs.

Impaired human immunodeficiency virus type 1 replicative fitness in atypical viremic non-progressor individuals.

BACKGROUND: Progression rates from initial HIV-1 infection to advanced AIDS vary significantly among infected individuals. A distinct subgroup of HIV-1-infected individuals-termed viremic non-progressors (VNP) or controllers-do not seem to progress to AIDS, maintaining high CD4+ T cell counts despite high levels of viremia for many years. Several studies have evaluated multiple host factors, including immune activation, trying to elucidate the atypical HIV-1 disease progression in these patients; however, limited work has been done to characterize viral factors in viremic controllers. METHODS: We analyzed HIV-1 isolates from three VNP individuals and compared the replicative fitness, near full-length HIV-1 genomes and intra-patient HIV-1 genetic diversity with viruses from three typical (TP) and one rapid (RP) progressor individuals. RESULTS: Viremic non-progressors and typical patients were infected for >10 years (range 10-17 years), with a mean CD4+ T-cell count of 472 cells/mm3 (442-529) and 400 cells/mm3 (126-789), respectively. VNP individuals had a less marked decline in CD4+ cells (mean -0.56, range -0.4 to -0.7 CD4+/month) than TP patients (mean -10.3, -8.2 to -13.1 CD4+/month). Interestingly, VNP individuals carried viruses with impaired replicative fitness, compared to HIV-1 isolates from the TP and RP patients (p < 0.05, 95% CI). Although analyses of the near full-length HIV-1 genomes showed no clear patterns of single-nucleotide polymorphisms (SNP) that could explain the decrease in replicative fitness, both the number of SNPs and HIV-1 population diversity correlated inversely with the replication capacity of the viruses (r = -0.956 and r = -0.878, p < 0.01, respectively). CONCLUSION: It is likely that complex multifactorial parameters govern HIV-1 disease progression in each individual, starting with the infecting virus (phenotype, load, and quasispecies diversity) and the intrinsic ability of the host to respond to the infection. Here we analyzed a subset of viremic controller patients and demonstrated that similar to the phenomenon observed in patients with a discordant response to antiretroviral therapy (i.e., high CD4+ cell counts with detectable plasma HIV-1 RNA load), reduced viral replicative fitness seems to be linked to slow disease progression in these antiretroviral-naïve individuals.

Increased tissue factor expression on circulating monocytes in chronic HIV infection: relationship to in vivo coagulation and immune activation.

HIV infection is associated with an increased risk of thrombosis; and as antiretroviral therapy has increased the lifespan of HIV-infected patients, their risk for cardiovascular events is expected to increase. A large clinical study found recently that all-cause mortality for HIV(+) patients was related to plasma levels of interleukin-6 and to D-dimer products of fibrinolysis. We provide evidence that this elevated risk for coagulation may be related to increased proportions of monocytes expressing cell surface tissue factor (TF, thromboplastin) in persons with HIV infection. Monocyte TF expression could be induced in vitro by lipopolysaccharide and flagellin, but not by interleukin-6. Monocyte expression of TF was correlated with HIV levels in plasma, with indices of immune activation, and with plasma levels of soluble CD14, a marker of in vivo lipopolysaccharide exposure. TF levels also correlated with plasma levels of D-dimers, reflective of in vivo clot formation and fibrinolysis. Thus, drivers of immune activation in HIV disease, such as HIV replication, and potentially, microbial translocation, may activate clotting cascades and contribute to thrombus formation and cardiovascular morbidities in HIV infection.

Immunologic failure despite suppressive antiretroviral therapy is related to activation and turnover of memory CD4 cells.

BACKGROUND: Failure to normalize CD4(+) T-cell numbers despite effective antiretroviral therapy is an important problem in human immunodeficiency virus (HIV) infection. METHODS: To evaluate potential determinants of immune failure in this setting, we performed a comprehensive immunophenotypic characterization of patients with immune failure despite HIV suppression, persons who experienced CD4(+) T-cell restoration with therapy, and healthy controls. RESULTS: Profound depletion of all CD4(+) T-cell maturation subsets and depletion of naive CD8(+) T cells was found in immune failure, implying failure of T-cell production/expansion. In immune failure, both CD4(+) and CD8(+) cells were activated but only memory CD4(+) cells were cycling at increased frequency. This may be the consequence of inflammation induced by in vivo exposure to microbial products, as soluble levels of the endotoxin receptor CD14(+) and interleukin 6 were elevated in immune failure. In multivariate analyses, naive T-cell depletion, phenotypic activation (CD38(+) and HLA-DR expression), cycling of memory CD4(+) T cells, and levels of soluble CD14 (sCD14) distinguished immune failure from immune success, even when adjusted for CD4(+) T-cell nadir, age at treatment initiation, and other clinical indices. CONCLUSIONS: Immune activation that appears related to exposure to microbial elements distinguishes immune failure from immune success in treated HIV infection.

Desensitization to type I interferon in HIV-1 infection correlates with markers of immune activation and disease progression.

Type I interferon (IFNalpha/beta) plays a complex role in HIV-1 infection and has been proposed alternately to have roles in either disease protection or progression. Although IFNalpha/beta plays crucial roles in regulating monocytes and dendritic cells, responsiveness of these cells to IFNalpha/beta in HIV-1 infection is poorly understood. We report significant defects in IFNalpha/beta receptor (IFNalpha/betaR) expression, IFNalpha signaling, and IFNalpha-induced gene expression in monocytes from HIV-1-infected subjects. IFNalpha/betaR expression correlated directly with CD4+ T-cell count and inversely with HIV-1 RNA level and expression of CD38 by memory (CD45RO+) CD8+ T cells, a measure of pathologic immune activation in HIV-1 infection associated with disease progression. In addition, monocytes from HIV-1-infected persons showed diminished responses to IFNalpha, including decreased induction of phosphorylated STAT1 and the classical interferon-stimulated gene produces MxA and OAS. These IFNalpha responses were decreased regardless of IFNalpha/betaR expression, suggesting that regulation of intracellular signaling may contribute to unresponsiveness to IFNalpha/beta in HIV-1 disease. Defective monocyte responses to IFNalpha/beta may play an important role in the pathogenesis of HIV-1 infection, and decreased IFNalpha/betaR expression may serve as a novel marker of disease progression.

In vitro naïve T cell proliferation failure predicts poor post-immunization responses to neoantigen, but not recall antigens, in HIV-infection.

Immune reconstitution after HAART is incomplete, but no widely accepted method to quantify subclinical immune deficiency is available. We immunized 9 HIV-negative subjects and 29 HIV-infected patients with CD4>/=450 cells/microL and undetectable HIV RNA levels with 2 doses of diphtheria/tetanus toxoid (TT) and KLH, a presumed neoantigen. We quantified the response by lymphoproliferative assay, delayed-type hypersensitivity (DTH), and antibody titers up to 59days after enrollment. We assessed T cell proliferative capacity using anti-Vbeta3 and anti-Vbeta5 antibody stimulation, which we herein show induced predominant proliferation of naïve T cells. Subjects with detectable responses to KLH tended to exhibit greater proliferative responses to anti-Vbeta3/Vbeta5 stimulation; no such pattern was seen with response to TT. Several measures of in vitro T cell proliferative capacity correlated significantly with DTH and antibody responses to KLH, but not with TT responses; this association was independent of naïve T cell numbers. Our results indicate that naïve T cell proliferation predicts response to neo-, but not recall antigens, and suggest that it may be a meaningful reflection of in vivo immune competence in HIV-infected persons.

Impaired plasmacytoid dendritic cell (PDC)-NK cell activity in viremic human immunodeficiency virus infection attributable to impairments in both PDC and NK cell function.

Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infections impair plasmacytoid dendritic cell (PDC) and natural killer (NK) cell subset numbers and functions, though little is known about PDC-NK cell interactions during these infections. We evaluated PDC-dependent NK cell killing and gamma interferon (IFN-gamma) and granzyme B production, using peripheral blood mononuclear cell (PBMC)-based and purified cell assays of samples from HCV- and HIV-infected subjects. CpG-enhanced PBMC killing and IFN-gamma and granzyme B activity (dependent on PDC and NK cells) were impaired in viremic HIV infection. In purified PDC-NK cell culture experiments, CpG-enhanced, PDC-dependent NK cell activity was cell contact and IFN-alpha dependent, and this activity was impaired in viremic HIV infection but not in HCV infection. In heterologous PDC-NK cell assays, impaired PDC-NK cell killing activity was largely attributable to an NK cell defect, while impaired PDC-NK cell IFN-gamma-producing activity was attributable to both PDC and NK cell defects. Additionally, the response of NK cells to direct IFN-alpha stimulation was defective in viremic HIV infection, and this defect was not attributable to diminished IFN-alpha receptor expression, though IFN-alpha receptor and NKP30 expression was closely associated with killer activity in viremic HIV infection but not in healthy controls. These data indicate that during uncontrolled HIV infection, PDC-dependent NK cell function is impaired, which is in large part attributable to defective IFN-alpha-induced NK cell activity and not to altered IFN-alpha receptor, NKP30, NKP44, NKP46, or NKG2D expression.

Accessory cell dependent NK cell mediated PBMC IFN-gamma production is defective in HIV infection.

HCV and HIV infections impair dendritic cell function. We evaluated the impact of HCV, HIV, and HCV-HIV infection on MDC-NK interactions by analyzing CD3 depleted PBMC for NK cell IFN-gamma in response to IL-12 or poly (I:C). Purified MDC and NK cells were analyzed for TLR ligand-dependent, MDC-dependent NK activity. In HIV infection, IFN-gamma production by CD3 depleted PBMC was reduced in response to poly (I:C), while response to IL-12 was intact in HCV and HIV infections. Poly (I:C) induced activity was dependent on MDC and partially dependent on IL-12, consistent with accessory cell help. In purified MDC-NK co-cultures, MDC dependent NK IFN-gamma and Granzyme B was intact in both HCV and HIV infections, while MDC numerical defects were observed in HIV infection. These data indicate that during viral infection with HIV, accessory cell dependent NK function in the periphery is impaired. This impairment may be related to the identified MDC numerical defect.

Stability of plasma indices of inflammation/coagulation and homeostasis after fatty and non-fatty meals in treated people with HIV.

OBJECTIVES: The relationship between lipid levels in plasma and inflammatory indices is complex and fatty meals alter plasma inflammatory markers in people with diabetes. There is interest in monitoring the effects of interventions on plasma inflammatory and coagulation elements in people with HIV, as they have been linked to risk for morbid outcomes and HIV persistence. Understanding the effects of feeding and time of specimen acquisition is important for the correct scheduling of clinical sampling. METHODS: We examined the effects of feeding on plasma inflammatory, coagulation and homeostatic indices among 24 non-diabetic people with HIV, with controlled viraemia and on antiretroviral therapy after fasting and then 1, 3 and 6 hours after ingesting a fatty meal, and also approximately 1 week later after fasting and after an isocaloric non-fatty meal. Plasma levels of IL-6, IL-7, IP-10, sCD14, sCD163, sTNFrII and D-dimer were monitored by immunoassay. RESULTS: Fasting levels of all markers obtained approximately 1 week apart were significantly correlated (P<0.001). Mild alterations in plasma concentrations of inflammatory markers were observed after feeding but geometric means varied more than 10% from baseline for only IL-6 and IL-7. Meal type was differentially associated with changes in plasma levels for IL-7 only. Antiretroviral treatment regimen, body mass index and changes in plasma triglyceride levels were not linked to post-feeding changes in these biomarkers. CONCLUSIONS: These plasma inflammatory, coagulation and homeostatic indices are relatively stable at fasting and are only minimally affected by feeding or time of day. These findings will aid in the monitoring of inflammatory and homeostatic indices that may contribute to control of HIV expression and its persistence.

Dissociated production of perforin, granzyme B, and IFN-gamma by HIV-specific CD8(+) cells in HIV infection.

CD8(+) T cells play a crucial role in the control of viral infections such as HIV. The functional characterization of HIV-specific CD8(+) T cells has so far been largely restricted to studies of IFN-gamma. The TCR-triggered release of the effector molecules perforin (PFN) and granzyme B (GzB), however, is thought to be a central pathway for the destruction of virus-infected target cells by CD8(+) effector T cells. Here we would like to address two major findings. On the one hand we propose that ex vivo measurements of PFN and GzB secretion via ELISPOT may permit the distinction between in vivo resting versus activated CD8(+) memory T cells in healthy and HIV-infected individuals. Therefore, extending the present standard of IFN-gamma measurements to the analysis of PFN and GzB release in functional T cell assays will provide new insights into CD8(+) effector T cell functions. It should enable the evaluation of therapeutic vaccination efficacy by its ability to reactivate and convert IFN-gamma-positive, but GzB- and PFN-negative memory CD8(+) T cells into PFN/GzB-secreting effector cells. On the other hand, we report on a frequent ex vivo dissociation of the HIV peptide-induced secretion of PFN and GzB in chronic HIV infection underlining CD8(+) effector T cell diversity in this disease--an aspect that also has to be accounted for in immune monitoring approaches.

Proteome and Protein Network Analyses of Memory T Cells Find Altered Translation and Cell Stress Signaling in Treated Human Immunodeficiency Virus Patients Exhibiting Poor CD4 Recovery.

Background. Human immunodeficiency virus (HIV) patients who experience poor CD4 T-cell recovery despite viral suppression during antiretroviral therapy (ART) are known as immunological nonresponders. The molecular mechanism(s) underlying incomplete immune restoration during ART is not fully understood. Methods. Label-free quantitative proteomics on single-cell type central memory T cells were used to reveal relative protein abundance changes between nonresponder, responder (good CD4 recovery during ART), and healthy individuals. Proteome changes were analyzed by protein pathway and network analyses and verified by selected reaction monitoring mass spectrometry. Results. Proteomic analysis across groups detected 155 significant proteins from 1500 nonredundant proteins. Pathway and network analyses revealed dysregulation in mammalian target of rapamycin and protein translation-related proteins and decreases in stress response-related proteins for nonresponder subjects compared with responders and controls. Actin cytoskeleton signaling was increased for HIV responders and nonresponders alike. Conclusions. Memory T cells from immunologic nonresponders have increases in proteins related to motility and protein translation and decreases in proteins capable of responding to cellular stresses compared with responders and controls. The potential for T cells to manage stress and modulate metabolism may contribute to their capacity to reconstitute a lymphopenic host.

Responsiveness to IL-7 but not to IFN-α is diminished in CD4+ T cells from treated HIV infected patients who experience poor CD4+ T-cell recovery.

OBJECTIVE: To assess CD4 T-cell responsiveness to IL-7 and IFN-α in HIV-infected patients who experience poor recovery of CD4 T-cell counts during therapy (immune failure patients). DESIGN: Responses to IL-7 and IFN-α were compared between HIV-infected immune failure (CD4 cell counts <379 cells/µl) patients and immune success (CD4 cell counts >500 cells/µl) as well as healthy control patients. METHODS: Flow cytometry was used to assess peripheral blood mononuclear cells for IL-7-induced proliferation, CD25 expression, and signaling (signal transducer and activator of transcription 5 phosphorylation and Akt phosphorylation) in CD4 T cells. Freshly isolated cells were characterized by expression of IL-7Rα (CD127) among CD4 T-cell maturation subsets by flow cytometry and sorted CD3 T cells were assessed for expression of IFN-α and interferon stimulated genes (2'-5'-oligoadenylate synthetase-1 and myxovirus resistance A protein) by quantitative real-time PCR. Responses to IFN-α were assessed by induction of signal transducer and activator of transcription 1 phosphorylation and inhibition of IL-7-induced CD4 T-cell proliferation. RESULTS: IL-7-induced proliferation and CD25 expression were decreased in CD4 T cells from immune failure patients. CD127 expressing CD4 T cells were decreased, whereas expression of 2'-5'-oligoadenylate synthetase-1, myxovirus resistance A protein, and IFN-α mRNA were increased in total CD3 T cells from immune failure patients. CD127 expression correlated with CD25 induction but not proliferation, whereas T-cell IFN-α mRNA was associated with reduced proliferation in CD4 T cells from immune failure patients. IFN-α-mediated induction of signal transducer and activator of transcription 1 phosphorylation and inhibition of proliferation were not diminished in CD4 T cells from immune failure patients. CONCLUSION: IL-7 responsiveness is impaired in immune failure patients and may be related to expression of CD127 and IFN-α.

New entrants to HIV care are presenting only at marginally earlier stages of disease but may increasingly represent groups perceived at lower risk.

BACKGROUND: Treatment has improved HIV infection prognosis, but whether risk and health care seeking behavior have improved is unclear. METHODS: New entrants to HIV care at University Hospitals of Cleveland, Ohio, between 1995 and 2002, with no history of AIDS-defining illnesses or antiretroviral exposure were included. RESULTS: Of new patients, 806 (80%) met the inclusion criteria. Median age increased during the study period(35.2 to 38.6 years; P < .001); proportions of females and non-whites increased nonsignificantly. Prevalence of AIDS-defining illnesses decreased from 1995 to 1996 (25.0% to 14.2%; P <.001) but remained stable thereafter. Category B conditions and sexually transmitted diseases decreased significantly(31.7% to 9.1%; P = .039 and 22.5% to 8.0%; P = .003), as did hepatitis B and C seroprevalence (8.3% to 3.6%; P = .05 and 26.2% to 14.3%; P = .003). Median CD4 counts and HIV RNA did not change significantly. CONCLUSIONS: Prevalence of Category B conditions, sexually transmitted diseases, and hepatitis B and C declined significantly in this study. Prevalence of AIDS-defining illnesses decreased early in the highly active antiretroviral therapy era only, whereas markers of HIV disease stage remained stable, suggesting a need for earlier recognition of infection. Decreasing sexually transmitted diseases and hepatitis coinfections suggest that HIV infection is increasingly seen in populations previously perceived at lower risk.

Tc1 effector diversity shows dissociated expression of granzyme B and interferon-gamma in HIV infection.

OBJECTIVE: To examine antigen specific cytotoxic effector T cell diversity in HIV infected individuals. DESIGN: We used a panel of previously defined HLA class I-restricted HIV peptides to stimulate CD8 cells in freshly isolated peripheral blood mononuclear cells of HIV infected patients, to determine cognate killing via the perforin-granzyme pathway and inflammation induced by secretion of interferon (IFN)-gamma. METHODS: ELISPOT assays were used to measure the secretion of granzyme B (GzB) and IFN-gamma at single cell resolution. RESULTS: In all nine patients only approximately 20% of the peptides triggered a canonical Tc1 response with simultaneous release of GzB and IFN-gamma. The majority of these peptides (approximately 80%) that elicited recall responses fell into the 'single positive' category with induction of either GzB or IFN-gamma alone. The GzB positive cells did not produce interleukin (IL)-4 or IL-5. CONCLUSION: The GzB positive but IFN-gamma negative CD8 cells are programmed to induce apoptosis mediated killing without inflammation while the GzB negative and IFN-gamma positive CD8 cells could mediate inflammation without killing. This Tc1 CD8 effector cell diversity and the understanding of these differentiation mechanisms may enable the precise implementation and fine-tuning of fundamentally different defense strategies against HIV and other infections.

Nadir CD4+ T-cell count and numbers of CD28+ CD4+ T-cells predict functional responses to immunizations in chronic HIV-1 infection.

OBJECTIVE: To ascertain whether delaying the initiation of highly active antiretroviral therapy (HAART) compromises functional immune reconstitution in HIV-1 infection in persons who regain 'normal' CD4 T-cell counts after suppressive antiretroviral therapies. DESIGN: Prospective open-label study carried out at two University-affiliated HIV-outpatient clinics in the USA. SUBJECTS AND METHODS: Response to immunization was used as a model for in vivo functional immune competence in 29 HIV-1 infected patients with CD4 T-cell counts > 450 x 106 cells/l and HIV-RNA < 400 copies/ml for > 12 months after HAART and nine HIV-1 seronegative controls. After immunization with tetanus toxoid, diphtheria-toxoid, and keyhole limpet hemocyanin, immune response scores (IRS) were calculated using postimmunization antibody concentrations, lymphocyte proliferation, and delayed-type hypersensitivity responses to vaccine antigens. RESULTS: Despite normal numbers of circulating CD4 T-cells, the CD4 T-cell nadir before HAART initiation predicted the immune response to immunization (rho = 0.5; P < 0.005) while current CD4 T-cell count did not. Likewise, CD4 T-lymphocyte expression of the co-stimulatory molecule CD28 was also an independent predictor of response to immunization (rho = 0.5; P < 0.005). CONCLUSIONS: Even among persons who controlled HIV replication and normalized CD4 T-cell counts with HAART, pretreatment CD4 T-cell count and numbers of circulating CD4+CD28+ T-cells at immunization, but not current CD4 T-cell count, predict the ability to respond to vaccination. Delaying the initiation of HAART in chronic HIV-1 infection results in impaired functional immune restoration despite normalization of circulating CD4 T-cell numbers.

Plasma levels of B-lymphocyte stimulator increase with HIV disease progression.

We measured the plasma levels of B-lymphocyte stimulator (BLyS) in 101 HIV-1-infected patients and 18 controls. BLyS levels were higher among HIV-positive patients [median 5.70 (3.90) versus 4.62 (1.04) ng/ml, P = 0.002], who had significantly higher BLyS and total serum globulin levels with decreasing CD4 cell counts. Moreover, BLyS levels increased exponentially below 100 CD4 cells/microl. BLyS and globulin levels increase as HIV dis ease progresses, suggesting a role for BLyS in the hypergammaglobulinemia of HIV infection.

HIV long-term non-progressors maintain brisk CD8 T cell responses to other viral antigens.

OBJECTIVE: To examine the specificity of heightened CD8 cell responses in HIV-1-infected long-term non-progressors. DESIGN: Cross-sectional study examining CD8 cell responses to hepatitis C virus (HCV) peptides in HCV-HIV LTNP (n = 6), HCV-HIV progressors (n = 11), HCV singly infected patients (n = 32), HCV singly infected patients with self-limited disease (n = 10), HIV singly infected progressors (n = 7) and HCV-negative, HIV-negative controls (n = 10). METHODS: The frequency of HCV-reactive interferon gamma-producing cells in peripheral blood was assayed by enzyme linked immunospot assay using a panel of 61 HCV-1-derived peptides. RESULTS: Five of six HCV-HIV LTNP had HCV-specific CD8 responses. In contrast, responses were observed in 2 of 32 HCV singly infected patients, 2 of the 10 HCV singly infected patients with self-limited disease, and 0 of 11 HCV-HIV progressors (P < 0.001). Both frequency of HCV-specific CD8 cells and number of HCV peptides recognized were greater in HCV-HIV LTNP than in other groups. CONCLUSIONS: HIV-infected LTNP maintain heightened CD8 cell responses to HCV in addition to heightened HIV specific responses. Common mechanisms may underlie preservation of CD8 immune responses in these individuals. An improved understanding of these mechanisms will help to gain insight into protective antiviral immunity as well as to the means whereby these viruses impair host defenses.

Proliferation responses to HIVp24 during antiretroviral therapy do not reflect improved immune phenotype or function.

OBJECTIVE: To ascertain whether lymphoproliferation (LP) responses to HIVp24 in chronically infected patients treated with antiretroviral therapy (ART) predict an improved cytolytic T-cell phenotype or better in vivo immune function as measured by immunization responses. METHODS: HIV-infected patients who started ART during chronic infection and who achieved viral suppression (HIV-RNA < 400 copies/ml for > 12 months) were grouped by the presence of strong [stimulation index (SI) > 10; n = 21] or absent (SI < 3; n = 18) LP to HIV-core antigen. The two groups were compared for functional immune responses to vaccination with diphtheria-toxoid, tetanus-toxoid and keyhole-limpet-hemocyanin, frequency of circulating naive and memory CD4+ and CD8+ T lymphocytes, maturation phenotype and expression of cytolytic molecules on total and HIV-specific CD8+ T cells, and frequency of memory CD4+ T cells with intracellular HIV-mRNA. Group comparisons were analyzed by non-parametric Mann-Whitney tests. Proportions were estimated by Pearson's chi analysis. RESULTS: There were no differences between the groups in immune responses to vaccination or in the numbers or phenotype of circulating T cells. In a subgroup of HLA-A2+ or B8+ patients, HIV-reactive CD8+ T cells in both groups had similar expression of perforin, granzyme A and T-cell maturation markers (CD27, CD28, CCR7, CD62L). However, patients with SI > 10 in response to HIVp24 tended to more often have high levels of circulating CD4+ T cells with intracellular HIV-1 mRNA than did patients with SI < 3. CONCLUSION: Following long-standing suppression of viral replication on ART, the presence of HIV-1 specific T-helper proliferation responses does not correlate with improved indices of immune phenotype or function but may reflect relatively higher levels of HIV-expression.

Interferon-α is the primary plasma type-I IFN in HIV-1 infection and correlates with immune activation and disease markers.

Type-I interferon (IFN-I) has been increasingly implicated in HIV-1 pathogenesis. Various studies have shown elevated IFN-I and an IFN-I-induced gene and protein expression signature in HIV-1 infection, yet the elevated IFN-I species has not been conclusively identified, its source remains obscure and its role in driving HIV-1 pathogenesis is controversial. We assessed IFN-I species in plasma by ELISAs and bioassay, and we investigated potential sources of IFN-I in blood and lymph node tissue by qRT-PCR. Furthermore, we measured the effect of therapeutic administration of IFNα in HCV-infected subjects to model the effect of IFNα on chronic immune activation. IFN-I bioactivity was significantly increased in plasma of untreated HIV-1-infected subjects relative to uninfected subjects (p = 0.012), and IFNα was the predominant IFN-I subtype correlating with IFN-I bioactivity (r = 0.658, p<0.001). IFNα was not detectable in plasma of subjects receiving anti-retroviral therapy. Elevated expression of IFNα mRNA was limited to lymph node tissue cells, suggesting that peripheral blood leukocytes are not a major source of IFNα in untreated chronic HIV-1 infection. Plasma IFN-I levels correlated inversely with CD4 T cell count (p = 0.003) and positively with levels of plasma HIV-1 RNA and CD38 expression on CD8 T cells (p = 0.009). In hepatitis C virus-infected subjects, treatment with IFN-I and ribavirin increased expression of CD38 on CD8 T cells (p = 0.003). These studies identify IFNα derived from lymph nodes, rather than blood leukocytes, as a possible source of the IFN-I signature that contributes to immune activation in HIV-1 infection.

Increased platelet and microparticle activation in HIV infection: upregulation of P-selectin and tissue factor expression.

OBJECTIVE: HIV-1-infected patients have an increased risk for atherothrombosis and cardiovascular disease, but the mechanism behind these risks is poorly understood. We have previously reported that expression of tissue factor (TF) on circulating monocytes is increased in persons with HIV infection and that TF expression is related to immune activation, to levels of HIV in plasma, and to indices of microbial translocation. In this study, we explore the activation state of platelets in HIV disease. METHODS: Here, using flow cytometry-based assays, we measured platelet and platelet microparticle (PMP) activation in samples from HIV-1-infected donors and controls. RESULTS: Platelets and PMPs from HIV-1-infected patients are activated (as reflected by expression of CD62 P-selectin) and also more frequently expressed the procoagulant TF than did platelets and PMPs obtained from controls. Expression of these proteins was directly related to expression of TF on monocytes, to markers of T-cell activation (CD38 and HLA-DR), and to plasma levels of soluble CD14, the coreceptor for bacterial lipopolysaccharride. Platelet and microparticle expression of TF was not related to plasma levels of HIV but expression of P-selectin was related to plasma levels of HIV; neither TF nor P-selectin expression was related to CD4 T-cell count. CONCLUSIONS: Platelets and microparticles are activated in HIV infection, and this activated phenotype may contribute to the increased risk for cardiovascular and thrombotic events in this population although a role for other confounding cardiovascular risks cannot be completely excluded.