Maximum suppression of HIV replication leads to the restoration of HIV-specific responses in early HIV disease

HIV-1-specific T-cell responses and exhaustion profiles in people with HIV after switching to dual therapy vs. maintaining triple therapy based on integrase inhibitors

BACKGROUND

Dual therapy (DT) has shown comparable results to triple therapy (TT) in efficacy and other immunological aspects. However, there are still some concerns about DT, including several immunological features. Therefore, we evaluated whether HIV-1-specific memory T-cell responses and exhaustion phenotypes are adversely influenced after simplification to DT.

METHODS

HIV-1-specific CD4+ and CD8+ T-cell responses were assessed by intracellular cytokine and degranulation marker staining, and polyfunctionality indexes after stimulation with a Gag peptide pool. Exhaustion phenotypes were evaluated by PD-1, TIM-3, and LAG-3 expression in CD4+ and CD8+ T cells.

RESULTS

Forty participants in the TRIDUAL trial (ClinicalTrials.gov: NCT03447873) who were randomized to continue integrase inhibitor-based TT (n = 20) or to switch to DT (dolutegravir or darunavir/cobicistat plus lamivudine) (n = 20). After 96 weeks, the magnitude of CD4+ and CD8+ T-cell responses was similar in both treatment arms (p = 0.221 and p = 0.602, respectively). The CD4+ polyfunctionality index decreased in the TT arm (p = 0.013) and remained stable in the DT arm, while the polyfunctionality of CD8+ T cells was unchanged in both arms. There was a significant decrease in the expression of PD-1, TIM-3, and the co-expression of PD-1+TIM-3+LAG-3+, and PD-1 +TIM-3 + in both CD4+ and CD8+ T cells. However, the decrease in the expression of exhaustion markers did not improve HIV-1-specific T-cell responses.

CONCLUSIONS

Our results suggest that simplification to DT does not negatively influence the HIV-1-specific T-cell response or the exhaustion phenotype after 96 weeks of follow-up.

Everything counts - a method to determine viral suppression among people living with HIV using longitudinal data for the HIV care continuum - results of two large, German, multi-center real-life cohort studies over 20 years (1999-2018)

Background

The aim of this study was to develop a standardized method to reconstruct persons’ individual viral load (VL) courses to determine viral suppression and duration of viremia for the HIV care continuum in Germany using longitudinal cohort data.

Methods

We analyzed data from two large, multi-center German cohort studies under the direction of the Robert Koch Institute. We included data from 1999 to 2018 of all diagnosed people and of people who initiated antiretroviral treatment (ART). We developed a model generating virtual VL values and an individual VL course corresponding to real VL measurements with a maximum distance of 180 days, considering ART status and VL dynamics. If the distance between VL measurements was > 180 days, the time between was defined as gap time. Additionally, we considered blips, which we defined as a single detectable VL < 1000 copies/ml within 180 days.

Results

A total of 22,120 people (164,691 person-years, PY) after ART initiation were included in the analyses. The proportion of people with viral suppression (VL < 50 copies/ml) increased from 34% in 1999 to 93% in 2018. The proportion of people with VL < 200 copies/ml increased from 47% in 1999 to 96% in 2018. The proportion of people with viremia > 1000 copies/ml decreased from 37% in 1999 to 3% in 2018. The proportion of people with gap time fluctuated and ranged between 18 and 28%. An analysis of the first VL after gap time showed that 90% showed viral suppression, 5% VL between 50- < 1000 copies/ml and 5% VL > 1000 copies/ml.

Conclusion

We provide a method for estimating viral suppression and duration of viremia using longitudinal VL data. We observed a continuous and remarkable increase of viral suppression. Furthermore, a notable proportion of those with viremia showed low-level viremia and were therefore unlikely to transmit HIV. Individual health risks and HIV drug resistance among those with low-level viremia are problematic, and viral suppression remains the goal. In 2018, 93 and 96% of people after ART initiation showed VL < 50 copies/ml and VL < 200 copies/ml, respectively. Therefore, using the threshold of VL < 200 copies/ml, Germany reached the UNAIDS 95 target of viral suppression since 2017.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-10088-7.

Brief Report: Relationship Among Viral Load Outcomes in HIV Treatment Interruption Trials

Viral load (VL) rebound timing and set point were analyzed in 235 participants undergoing analytic treatment interruption (ATI) in 6 AIDS Clinical Trials Group studies. There was no significant association between rebound timing and ATI VL set point for those who rebounded ≤12 weeks. VL set points were lower in participants with rebound >12 weeks (P < 0.001) and participants treated during early infection (P < 0.001). Pre-antiretroviral therapy VL correlated with set point, though 68% of participants had a set point lower than pre-antiretroviral therapy VL. These results illustrate complex relationships between post-ATI virologic outcomes and the potential presence of biological factors mediating rebound timing and set point.

Factors associated with 10 years of continuous viral load suppression on HAART

Background

The principal goal of HAART is sustained viral load (VL) suppression resulting in immune reconstitution and improved HIV outcomes. We studied the factors associated with 10 years of continuous VL suppression on HAART in the US Military HIV Natural History Study.

Methods

Participants with continuous VL suppression (CS, n = 149) were compared to those who did not have continuous viral load suppression (NCS, n = 127) for ≥10 years on HAART. Factors associated with >10 years of VL suppression were evaluated by multivariate logistic regression. Additionally, association between CS and CD4 reconstitution was analyzed with a mixed effects model.

Results

Compared to NCS participants, a lower proportion of CS participants started HAART in the early HAART era (66 vs 90 %, for years 1996–1999; p < 0.001) and had less antiretroviral use prior to HAART (37 vs 83 %; p < 0.001). At initial HAART, the median CD4 cell count was higher and VL was lower for CS compared to NCS participants (375 cells/uL [256, 499] vs 261 cells/uL [146, 400]; p < 0.001 and 4.4 log₁₀ copies/mL [3.5, 4.9] vs 4.5 log₁₀ copies/mL [3.8, 5.0]; p = 0.048, respectively). New AIDS events were lower during HAART (5 vs 13 %; p = 0.032) and post-HAART CD4 trajectories were greater for the CS compared to NCS group. Factors negatively associated with ≥10 years of VL suppression included log₁₀ VL at first HAART (OR 0.61, 95 % CI 0.4, 0.92; p = 0.020) and antiretroviral use prior to HAART (OR 0.16, 95 % CI 0.06, 0.38; p < .001).

Conclusions

Sustained VL suppression is a key to long-term health in HIV-infected patients, as demonstrated by the lower proportion of AIDS events observed 10 years after HAART initiation. The current use of more potent and well-tolerated regimens may mitigate the negative factors of pre-HAART VL and prior ARV use encountered by treatment initiated in the early HAART era.

Slow resolution of inflammation in severe adult dengue patients

BACKGROUND

The pathogenesis of severe dengue has not been fully elucidated. The inflammatory response plays a critical role in the outcome of dengue disease.

METHODS

In this study, we investigated the levels of 17 important inflammation mediators in plasma collected from mild or severe adult dengue patients at different time points to understand the contribution of inflammation to disease severity and to seek experimental evidence to optimize the existing clinical treatment strategies. Patients were simply classified as mild and severe dengue according to the 2009 WHO classification. Plasma was collected on day 3-5, 6-7, 8-10 and 14-17 of illness. Levels of 17 inflammation mediators including TNF-α, IL-1α, IFN-γ, IL-6, IFN-α, MIF, IL-10, IL-1RA, IL-8, IP-10, MCP-1, RANTES, GRO, eotaxin-1, sICAM-1 and sVCAM-1 were determined by a multiplex Luminex® system. Different trends of inflammation mediators throughout the disease were compared between mild and severe patients.

RESULTS

Inflammation mediators including IL-1α, IFN-γ, IL-10, IL-8, IP-10, MCP-1 and sVCAM-1 displayed significant differences on day 8-10 of illness between mild and severe dengue patients. Their concentrations were higher in severe patients than mild ones at the same time points. Moreover, those cytokines decreased gradually in mild patients but not in severe patients.

CONCLUSION

Our results revealed the coexistence of excessive inflammatory response and slow resolution of inflammation in severe adult dengue patients. Hence suppression and/or pro-resolution of inflammation could be a potential therapeutic approach for treatment of severe dengue.

The activation and dynamics of cytokine expression by CD4+ T cells and AIDS progression in HIV-1-infected Chinese individuals

CD4(+) T cells are the main targets of HIV-1 and play a central role during the progression of AIDS, but the mechanism has not been clearly elucidated. In the present study, blood samples were collected from HIV-1-infected Chinese individuals, including typical progressors (TPs) and long-term nonprogressors (LTNPs). More HIV-1 productively infected CD4(+) T cells were obtained through co-cultures and the infected CD4(+) T cells were discriminated from bystander cells by intracellular p24 staining. The activation level and dynamics of cytokine expression of CD4(+) T cells were analyzed. After stimulating the freshly isolated PBMCs with PHA, the frequencies of CD69(+)CD4(+) T cells/CD25(+)CD4(+) T cells were higher in TP than in LTNP group and were positively correlated with viral load and negatively correlated with CD4(+) T cell counts. The activation level of CD4(+) T cells in the co-cultured PBMCs was higher in TP than in LTNP group, and HIV-1 productively infected CD4(+) T cells were more activated than bystander CD4(+) T cells. The expression of Th1 cytokines (IL-2 and IFN-γ) and the frequency of Th1 cells in co-cultured PBMCs were lower in TP than in LTNP group. HIV-1 productively infected CD4(+) T cells expressed higher level of Th1/Th2 cytokines than bystander cells. More productive HIV-1 infection occurred in Th1 than in Th2 cells, followed by Th0 cells. The present results suggest that the excessive activation level of CD4(+) T cells and the preferential replication of HIV-1 in Th1 cells that lead to the shift of Th1 to Th2 are likely crucial to AIDS progression in HIV-1-infected Chinese individuals.

Treatment with IL-7 prevents the decline of circulating CD4+ T cells during the acute phase of SIV infection in rhesus macaques

Although treatment with interleukin-7 (IL-7) was shown to transiently expand the naïve and memory T-cell pools in patients with chronic HIV-1 infection receiving antiretroviral therapy (ART), it is uncertain whether a full immunologic reconstitution can be achieved. Moreover, the effects of IL-7 have never been evaluated during acute HIV-1 (or SIV) infection, a critical phase of the disease in which the most dramatic depletion of CD4⁺ T cells is believed to occur. In the present study, recombinant, fully glycosylated simian IL-7 (50 µg/kg, s.c., once weekly for 7 weeks) was administered to 6 rhesus macaques throughout the acute phase of infection with a pathogenic SIV strain (mac251); 6 animals were infected at the same time and served as untreated controls. Treatment with IL-7 did not cause clinically detectable side effects and, despite the absence of concomitant ART, did not induce significant increases in the levels of SIV replication except at the earliest time point tested (day 4 post-infection). Strikingly, animals treated with IL-7 were protected from the dramatic decline of circulating naïve and memory CD4⁺ T cells that occurred in untreated animals. Treatment with IL-7 induced only transient T-cell proliferation, but it was associated with sustained increase in the expression of the anti-apoptotic protein Bcl-2 on both CD4⁺ and CD8⁺ T cells, persistent expansion of all circulating CD8⁺ T-cell subsets, and development of earlier and stronger SIV Tat-specific T-cell responses. However, the beneficial effects of IL-7 were not sustained after treatment interruption. These data demonstrate that IL-7 administration is effective in protecting the CD4⁺ T-cell pool during the acute phase of SIV infection in macaques, providing a rationale for the clinical evaluation of this cytokine in patients with acute HIV-1 infection.

The development of highly effective cocktails of antiretroviral drugs has had a major impact on the survival and quality of life of individuals with HIV-1 infection. Yet, current protocols often fail to fully restore the immunologic function, a limitation that has prompted the clinical evaluation of immune-reconstitution agents, such as IL-7, as adjuvant therapies. To date, however, IL-7 has been tested exclusively in patients with chronic HIV-1 infection, while it appears that the immune system is irreparably damaged during acute primary infection, within the first few weeks after encountering the virus. We used a macaque model to show that treatment with IL-7 has beneficial effects if implemented during the acute phase of infection with SIV, the simian AIDS virus. Early administration of IL-7 was safe and effectively protected CD4⁺ T cells, the primary target cells for the virus, from the marked decline that typically occurs during acute SIV infection. Furthermore, IL-7 boosted the development of antiviral immune responses. Thus, IL-7 might be an effective adjuvant therapy in acute HIV-1 infection, which can protect the pool of CD4⁺ T cells before it is irreversibly compromised by the action of the virus.

Immune reconstitution after a decade of combined antiretroviral therapies for human immunodeficiency virus

The introduction of combined antiretroviral therapies (HAART) has reversed the fatal course of human immunodeficiency virus (HIV) infection. HAART controls virus production and, in most cases, allows the quantitative and functional immune defects caused by HIV to be reversed. Here, we review T cell homeostatic mechanisms that drive immune recovery. These homeostatic mechanisms, as well as differences in T cell antigen exposure, explain the distinct patterns of recovery for HIV-specific T cells versus T cells specific for other pathogens. Immune restoration during HAART can, however, have adverse effects. Immune restoration syndrome occurs in some patients as a result of successful but unbalanced immunity.

Clinical management of acute HIV infection: best practice remains unknown

Best practice for the clinical management of acute human immunodeficiency virus (HIV) infection remains unknown. Although some data suggest possible immunologic, virologic, or clinical benefit of early treatment, other studies show no difference in these outcomes over time, after early treatment is discontinued. The literature on acute HIV infection is predominantly small nonrandomized studies, which further limits interpretation. As a result, the physician is left to grapple with these uncertainties while making clinical decisions for patients with acute HIV infection. Here we review the literature, focusing on the potential advantages and disadvantages of treating acute HIV infection outlined in treatment guidelines, and summarize the presentations on clinical management of acute HIV infection from the 2009 Acute HIV Infection Meeting in Boston, Massachusetts.

Predictive value of immune parameters before treatment interruption (TI) for CD4+ T-cell count change during TI in HIV infection

Background

Despite the contraindications, stopping treatment for HIV infection continues to be a common practice. Understanding whether T-cell proliferative capacity and phenotypic markers before treatment interruption (TI) can predict CD4+ T-cell count change and nadir during TI would be clinically useful.

Methods

This retrospective study included 27 HIV- infected patients in the chronic phase of infection while on combination antiretroviral therapy (cART) who underwent a TI. Peripheral blood mononuclear cells from a baseline pre-TI time point were screened for T-cell proliferation to cytomegalovirus (CMV) lysate, an HIV Gag p55 peptide pool as well as positive and negative control stimuli. CD28 and CD57 expression on CD4+ and CD8+ T-cells were measured.

Results

Baseline viral load, CD4+ T-cell count, pre-cART nadir CD4+ T-cell and percentage CD4+CD28+ T-cells were all predictive of the lowest CD4+ T-cell count during TI (Spearman's correlation P<0.05 for all analyses). In addition, CD4+ and CD8+ T-cells proliferation to CMV lysate, baseline CD4+ T-cell count and percentage CD4+CD57+ T-cells correlated negatively with CD4+ T-cell decrease during TI (Spearman's correlation P<0.05 for all analyses).

Conclusions

In treated chronic HIV-infected patients, pre-TI immune parameters are potential predictors for both the nadir CD4+ T-cell count and CD4+ T-cell count decrease during TI.

Valproic acid without intensified antiviral therapy has limited impact on persistent HIV infection of resting CD4+ T cells

OBJECTIVES

Valproic acid and intensified antiretroviral therapy may deplete resting CD4+ T-cell HIV infection. We tested the ability of valproic acid to deplete resting CD4+ T-cell infection in patients receiving standard antiretroviral therapy.

METHODS

Resting CD4+ T-cell infection was measured in 11 stably aviremic volunteers twice prior to, and twice after Depakote ER 1000 mg was added to standard antiretroviral therapy. Resting CD4+ T-cell infection frequency was measured by outgrowth assay. Low-level viremia was quantitated by single copy plasma HIV RNA assay.

RESULTS

A decrease in resting CD4+ T-cell infection was observed in only four of the 11 patients. Levels of immune activation and HIV-specific T-cell response were low and stable. Valproic acid levels ranged from 26 to 96 microg/ml when measured near trough. Single copy assay was performed in nine patients. In three patients with depletion of resting CD4+ T-cell infection following valproic acid, single copy assay ranged from less than 1-5 copies/ml. Continuous low-level viremia was observed in three patients with stable resting CD4+ T-cell infection (24-87, 8-87, and 1-7 copies/ml respectively) in whom multiple samples were analyzed.

CONCLUSION

The prospective addition of valproic acid to stable antiretroviral therapy reduced the frequency of resting CD4+ T-cell infection in a minority of volunteers. In patients in whom resting CD4+ T-cell infection depletion was observed, viremia was rarely detectable by single copy assay.

Immunophenotypic alterations in acute and early HIV infection

To understand the extent of immune dysregulation in primary HIV infection (PHI) and the impact of antiretroviral therapy (ART) on restoring these abnormalities, we longitudinally evaluated 52 subjects (Acute-Treated (AT); Early-Treated (ET); Early Untreated (EU)) for markers of activation, proliferation, and function on T cells. ET and AT patients differed by 0.54 log viral load (VL) at baseline but did not differ thereafter by more than 0.34 log10 VL. AT subjects had higher CD8(+) T cell counts and expression of markers indicative of CD8(+) T cell activation (CD38), and proliferation (Ki67), at baseline, than ET subjects but were not different 48 weeks post-ART. Although acute PHI is marked by higher level of immune activation than early PHI, virologic and immunologic responses were similar post-ART, suggesting that the extent of immunologic recovery is not negatively impacted by a delay of treatment beyond the acute stage of disease.

HIV infection of primary CD4+ Th2 cells, defined by expression of the chemoattractant receptor-homologous (CRTH2), induces a Th0 phenotype

The association between HIV, cytokine profile, and disease progression is controversial. In this study, we evaluated whether HIV infection of a primary T helper-like type 2 cytokine (Th2) cell subset augments their cytokine profile. We utilized the CRTH2 (chemoattractant receptor-homologous) marker to identify CD4+ Th2 cells. Approximately 2-4% of CD4+ T cells are CRTH2+. CRTH2+ expression is confirmed to delineate a Th2 subset as indicated by robust inducible IL-4 response. CD4+ CRTH2+ T cells were also more inherently activated than their CRTH2-negative counterpart as indicated by a higher percent expression of CD69, CD45RO, CD95, CD25, and HLA-DR. CD4+CRTH2+ T cells were not terminally differentiated as indicated by expression of CD27 and CD28. In vitro HIV infection of primary human CD4 CRTH2T cells, independent of chemokine coreceptor usage, potently upregulated IFN-gamma production while still maintaining robust IL-4 expression. This Th0 (IFNgamma+ IL-4+) phenotype was upregulated in CD4+CRTH2+ T cells post-HIV infection by 18-fold, demonstrating a shift to a Th0 phenotype. Ex vivo studies also demonstrated that HIV+ patients exhibited a decline in CD4+CRTH2+ cells and a shift of this population toward cells that express both IFN-gamma and IL-4. Collectively, these data indicate that HIV replication in Th2 cells induces a Th0 phenotype. This phenomenon may be a deliberate viral escape mechanism to prevent the skewing of the immune response toward Th1 or Th2.

Innate immune defenses in HIV-1 infection: prospects for a novel immune therapy

HIV-1 infection leads to a severe decrease of CD4(+) T lymphocytes, dysregulation of several leukocyte subpopulations and generalized immune activation, with the subsequent development of opportunistic infections and malignancies. Administration of highly active antiretroviral therapy (HAART) has been successful in reducing HIV-1 plasma viremia; however, the ability of HAART to restore immunocompetence appears incomplete, particularly in patients with chronic and advanced disease. Several components of the innate immune system have direct anti-HIV-1 effects, and studies to analyze the benefits of enhancing the function of the innate response during HIV-1 infection are increasing. Development of any complementary therapeutic approaches to HIV-1 infection, particularly those able to compensate for the limitations of HAART, and enhance the anti-HIV-1 innate immune activity would be of interest. The stimulation of innate immune responses using Toll-like receptor agonists, such as monophosphoryl lipid A and oligodeoxynucleotides with CpG motifs, are currently being investigated and their benefit in HIV-1-infected patients are under evaluation.

Changes in paracrine interleukin-2 requirement, CCR7 expression, frequency, and cytokine secretion of human immunodeficiency virus-specific CD4+ T cells are a consequence of antigen load

Virus-specific CD4+ T-cell responses are thought to be required for the induction and maintenance of many effective CD8+ T-cell and B-cell immune responses in experimental animals and humans. Although the presence of human immunodeficiency virus (HIV)-specific CD4+ T cells has been documented in patients at all stages of HIV infection, many fundamental questions regarding their frequency and function remain. A 10-color, 12-parameter flow cytometric panel was utilized to examine the frequency, memory phenotype (CD27, CCR7, and CD45RA), and cytokine production (interleukin-2 [IL-2], gamma interferon, and tumor necrosis factor alpha) of CD4+ T cells specific for HIV antigens as well as for adenovirus, Epstein-Barr virus (EBV), influenza H1N1 virus, influenza H3N2 virus, cytomegalovirus, varicella-zoster virus (VZV), and tetanus toxoid in normal controls, long-term nonprogressors (LTNP), and HIV-infected patients with progressive disease on or off therapy. The HIV-specific CD4+ T-cell responses in LTNP and patients on therapy were similar in frequency, phenotype, and cytokine production to responses directed against adenovirus, EBV, influenza virus, and VZV. HIV-specific CD4+ T cells from patients off antiretroviral therapy demonstrated a shift towards a CCR7(-) CD45RA(-) phenotype and a reduced percentage of IL-2-producing cells. The alterations in cytokine production during HIV viremia were found to be intrinsic to the HIV-specific CD4+ T cells and caused a requirement for IL-2 supplied exogenously for proliferation to occur. These observations suggest that many previously described changes in HIV-specific CD4+ T-cell function and phenotype are a consequence of high levels of antigen in viremic patients. In addition, defects in function and phenotype of HIV-specific CD4+ T cells are not readily discernible in the context of antiretroviral therapy but rather are similar to responses to other viruses.

Presence of distinct subsets of cytolytic CD8+ T cells in chronic HIV infection

Cytolytic T lymphocytes (CTL) play an important role in the control of HIV infection. The eventual failure to contain HIV-1 infection may arise because of a functional impairment of HIV-specific CTL. We evaluated Gag-specific cytotoxicity in HIV-1-positive Ugandans. Expression of CD107, a marker for cytolytic activity, was present in CD45RA(bright) and CD45RA(dim) CD8(+) T cell populations in HIV-infected individuals. The frequency of Gag-specific CD107(+)CD45RA(bright)CD28(-)CCR7(-) CD8(+) T cells decreased with CD4 cell depletion and correlated with the presence of Gag-specific T helper response. In contrast, the frequency of Gag-specific CD107(+)CD45RA(dim)CD28(-)CCR7(-) CD8(+) T cells within the same individuals has no significant association with viral load or CD4 cell count. The ratio of CD45RA(bright) to CD45RA(dim) CTL correlates significantly with CD4 cell count. This positive association decreases with antiretroviral treatment (ARV), indicating that suppression of viral replication alters the balance of circulating Gag-specific CD8(+) effector T cells. Subsets of cytolytic T cells may have distinct antiviral functions and further characterization of these effector CD8(+) T cells may yield important information on T cell regulation and dysfunction in HIV infection.

Changes in T-cell subpopulations during four years of suppression of HIV-1 replication in patients with advanced disease

We compared the number/percentages of naive and memory CD4+ T-cells, CD38+ CD8+ T-cells, and CD28+ CD4+ and CD28+ CD8+ T-cells in patients with advanced HIV disease (baseline CD4+ count < 100) with those with less advanced (baseline CD4+ cell count > 100) HIV disease during 4 years of suppressive highly active antiretroviral therapy. This prospective, longitudinal study included 30 treatment-naive patients and 32 controls. Advanced HIV-infected patients (n = 13) gained more CD4+ T-cells than less advanced patients (n = 11) at 1 month (median: 60 vs. 36 microL(-1)), 3 months (86 vs. 14), 6 months (111 vs. 23), 12 months (174 vs. 47), 24 months (162 vs. 72) and 48 months (257 vs. 123) (P = 0.15, P < 0.001, P = 0.026, P = 0.021, P = 0.1 and P = 0.06, respectively). Advanced patients gained more naive CD4+ T-cells at 48 months compared to less advanced patients (27.3 vs. 11.4%, P = 0.05). The relative gain in memory CD4+ T-cells was greater in advanced vs. less advanced patients at 1 month (median: 6.4 vs. 1.4%), 3 months (4.3 vs. 2.0), 6 months (6.7 vs. 1.6), 12 months (6.9 vs. 2.4), 24 months (7.5 vs. 3.1) and 48 months (11.3 vs. 6.8) (P = 0.002, P = 0.013, P < 0.001, P = 0.004, P = 0.001 and P = 0.015, respectively). At 48 months, CD38+ CD8+ T-cells and naive CD4+ T-cells reached normal values (9.2%, P = 0.869 vs. controls and 47.5%, P = 0.699, respectively) in less advanced patients, as did CD38+ CD8+ T-cells in advanced patients (4.7%, P = 0.309 vs. controls). The kinetics of naive and memory CD4+ T-cell reconstitution is different in less advanced compared to advanced HIV patients.

Persistent abnormalities in peripheral blood dendritic cells and monocytes from HIV-1-positive patients after 1 year of antiretroviral therapy

Antiretroviral therapy (ART) has led to marked decreases in morbidity and mortality rates among HIV-1-positive patients; however, immune recovery is not complete. Although dendritic cells (DCs) were shown to be involved in HIV-1 pathogenesis, few studies have investigated the effect of ART on DCs. We have analyzed the effect of ART on numerical distribution, expression of chemokine receptors, and ex vivo production of inflammatory cytokines by peripheral blood (PB) monocytes and DCs in a cohort of chronically infected HIV-1-positive patients. Patients were tested before therapy and at weeks +2, +4, +8, +12, and +52 after starting ART.Our results show an incomplete T-cell immune reconstitution in chronically infected patients who had undetectable plasma viremia while taking ART for 1 year. This was associated with persistent abnormalities at week +52 of ART, corresponding to increased numbers of CD16 DCs and monocytes, as well as altered expression of CXC chemokine receptors, in the form of increased CXCR1 expression on monocytes and decreased reactivity for CXCR2 and/or CXCR4 on myeloid and plasmacytoid DCs. In addition, an abnormally high spontaneous ex vivo secretion of inflammatory cytokines by CD16 DCs and monocytes was still detected after 1 year of ART. These abnormalities were especially pronounced in patients with less than 200 CD4 T cells/microL, which could be related to the persistence of undetected viral replication and sustained immune activation.

Routine, rapid HIV testing

HIV testing identifies HIV-positive persons, allowing for reduced future HIV transmission while simultaneously providing policy makers with surveillance data to inform policy planning. If current costs of HIV testing were reduced, these funds could be redirected to increase testing rates or to expand treatment. The cost of testing is lowered and impact increased if noninvasive (oral and urine), rapid-testing modalities are utilized, pretest counseling uses cost-efficient counseling methods (e.g., video, pamphlets, small group discussions), and opt-out consent strategies are implemented while posttest counseling is more narrowly targeted to HIV-positive persons. Rather than relying on one international standard, customizing HIV testing procedures to local environments may be more efficient and effective. In the United States, laboratories with substantial HIV testing revenues are likely to be most resistant to altering current practices. However, AIDS researchers, policy makers, and advocates may dramatically influence the epidemic's course by encouraging flexibility and innovation in HIV-testing guidelines.

HIV-1 persistence, viral reservoir, and the central nervous system in the HAART era

HAART therapy has led to a significant reduction of general and neurological morbidity, and mortality among HIV-1 infected patients. It can also decrease HIV-1 RNA titres in plasma and CSF towards undetectable level. However, the initial hope of achieving total eradication of the virus from the body has vanished. Even in patients who do not develop viral resistance or treatment intolerance, two kinds of viral persistence have been demonstrated both in lymphoid and central nervous system. The first one is a smoldering infection that persists, despite prolonged and apparently efficient HAART, in monocytes, tissue macrophages and most probably microglia. The second one is an integration of proviral DNA in the genome of subpopulations of CD4 lymphocytes of patients receiving efficient HAART. A similar viral integration in astrocytes and less likely in resting microglia is suggested by several studies, although it has yet to be demonstrated conclusively.

CD8+ cell noncytotoxic anti-HIV response: restoration by HAART in the late stage of infection

Highly active antiretroviral therapy (HAART) is currently the best HIV infection management strategy. However, its effects on the CD8+ T cell noncytotoxic anti-HIV response (CNAR) are not well known. We investigated if HAART has different effects on CNAR in patients at the intermediate and late stages of HIV infection. Untreated healthy HIV-infected subjects with a mean CD4+ T cell count of 606 cells/microl were examined as a reference group. Plasma viral load, CD4+ T cell count, and CNAR activity were measured at baseline and regular intervals for at least 48 weeks following initiation of HAART. Baseline CNAR activity in all subjects correlated inversely with viral load and directly with CD4 T+ cell counts. The level of CNAR in the latestage group was significantly lower than in the intermediate-stage and the healthy reference group (p < 0.01). Following initiation of HAART, substantial increases in CD4+ T cell counts and decreases in viral loads were observed in both groups, indicating treatment success. CNAR activity was found to be increased significantly during HAART, but only in the late-stage group (p < 0.01). This increase in CD8+ cell function was seen within 4 weeks of treatment initiation and resulted in levels of CNAR activity almost equal to those observed in the healthy reference subjects. Our findings suggest a beneficial effect on CNAR in those individuals with reduced activity, typically in late-stage infection.

Advances in understanding immunologic control of HIV infection

Over the past several years, the progress made in understanding the cellular immune response to HIV is likely greater compared to any other time since the beginning of the worldwide epidemic. This progress has largely been made possible by technical advances that have permitted a much more quantitative and highly detailed study of virus-specific cellular immunity in humans than was previously available. However, despite intensive study of the HIV-specific cellular immune response, we do not fully understand the nature of immunologic control in some rare cases and lack of control in most of untreated patients. It has become increasingly clear that HIV replication is poorly controlled in most untreated patients, despite a high-frequency HIV-specific cellular immune response. Therefore, attention has turned to qualitative features of the immune response that may dictate restriction of viral replication. Because most vaccines in preclinical or clinical testing rely on cellular immune responses that may alter disease progression but are unlikely to prevent infection, understanding these qualitative features is of particular importance. Further study could yield critical information for inducing effective immunity in vaccinees, preventing the loss of control of viral replication on the infection of vaccinees, or inducing immunologic control in infected humans.

Presence of HIV-specific CD4+ T-cell responses in HIV-infected subjects with sustained virologic control after highly active antiretroviral therapy

HIV-specific CD4+ T-helper cell responses in 40 subjects with chronic infection (CI) who had virus suppression after highly active antiretroviral therapy (HAART) were compared with those in 34 subjects treated during primary infection (PI). A CD4+ T-cell proliferative response to HIV p24 protein was present in 50% of these subjects compared with 79% of subjects treated during PI. The existence of a proliferative response in CI subjects was associated with a higher CD4+ T-cell count at initiation of HAART, a longer duration of virus suppression, and a higher CD4+ T-cell count at the time of analysis. These results show that an HIV-specific proliferative response is preferentially observed in treated CI subjects with CD4+ T-cell counts of >200/microL. However, in treated CI subjects with a significant degree of CD4+ T-cell depletion (<200/microL), it may also be observed in 35% provided that the duration of virus suppression is long enough, which may have implications for future therapeutic strategies.

Depletion of latent HIV-1 infection in vivo: a proof-of-concept study

BACKGROUND

Persistent infection in resting CD4+ T cells prevents eradication of HIV-1. Since the chromatin remodeling enzyme histone deacetylase 1 (HDAC1) maintains latency of integrated HIV, we tested the ability of the HDAC inhibitor valproic acid to deplete persistent, latent infection in resting CD4+ T cells.

PROCEDURES

We did a proof-of-concept study in four volunteers infected with HIV and on highly-active antiretroviral therapy (HAART). After intensifying the effect of HAART with subcutaneous enfuvirtide 90 mug twice daily for 4-6 weeks to prevent the spread of HIV, we added oral valproic acid 500-750 mg twice daily to their treatment regimen for 3 months. We quantified latent infection of resting CD4+ T cells before and after augmented treatment by limiting-dilution culture of resting CD4+ T cells after ex-vivo activation.

FINDINGS

The frequency of resting cell infection was stable before addition of enfuvirtide and valproic acid, but declined thereafter. This decline was significant in three of four patients (mean reduction 75%, range 68% to >84%). Patients had slight reactions to enfuvirtide at the injection site, but otherwise tolerated treatment well.

INTERPRETATION

Combination therapy with an HDAC inhibitor and intensified HAART safely accelerates clearance of HIV from resting CD4+ T cells in vivo, suggesting a new and practical approach to eliminate HIV infection in this persistent reservoir. This finding, though not definitive, suggests that new approaches will allow the cure of HIV in the future.

Differential Upregulation of CD38 on Different T-Cell Subsets May Influence the Ability to Reconstitute CD4+ T Cells Under Successful Highly Active Antiretroviral Therapy

BACKGROUND

Immune activation is an independent surrogate marker of CD4 T-cell depletion in HIV-infected patients. Highly active antiretroviral therapy (HAART) reduces disease progression as a direct consequence of suppressing HIV replication. Immune function does not normalize completely in most subjects on HAART, however, perhaps reflecting residual HIV replication. So far, it is unclear to what extent immune activation may influence the evolution of CD4 T-cell counts in patients on HAART.

PATIENTS AND METHODS

The expression of CD38 on naive and memory subsets of CD4+ and CD8+ T cells was measured quantitatively by flow cytometry in 62 drug-naive HIV-positive and 30 HIV-uninfected controls. In addition, the evolution of this marker as well as that of some virologic parameters (plasma viremia and proviral load) and CD4 counts were assessed in 25 HIV-infected individuals who initiated HAART and were followed for 12 months.

RESULTS

The mean level of CD38 on memory CD4+ and CD8+ T cells as well as in naive CD8+ cells was significantly higher in drug-naive HIV-positive subjects than in HIV-negative controls. Moreover, it was highly correlated with viral load titers. In patients on successful HAART, immune activation declined in all T-cell subsets, particularly among memory CD8+ cells. It remained elevated with respect to HIV-negative controls, however, even after 12 months of HAART. There was a significant correlation between the CD8+ T-cell activation decay and the increase of CD4+ T cells on HAART. Patients with the highest decline in CD8 activation were those showing the highest CD4 T-cell gains after 12 months of therapy.

CONCLUSIONS

The level of CD38 expression on different T-cell subsets is differentially upregulated in drug-naive HIV-infected patients. After successful HAART, immune activation decreases in all T-cell subsets, although it still remains elevated in most cases after 12 months of HAART. The extent of immune deactivation under successful HAART correlates with the ability to reconstitute CD4 counts.

Flow Cytometry Evaluation of the T-Cell ReceptorVβ Repertoire Among HIV-1 Infected Individuals Before and After Antiretroviral Therapy

HIV-1 infection leads to serious impairment of the immune system and perturbations in the T cell receptor Vbeta repertoire are also described. Immune reconstitution can be potentially achieved in response to HAART. In the present study 10 patients were investigated for the Vbeta pattern expression before and after six months of HAART. TCR were analyzed for T CD4+ and CD8+ subsets, separately, by flow cytometry, using a monoclonal antibody set of 24 different Vbeta chains. Compared to eight Brazilian healthy controls, no differences in Vbeta pattern of expression was observed for patients before or on antiretroviral therapy. Some chains such as Vbeta 3, 14, 16, 20 and 21.3 were over utilized by both T subsets, independently of HIV infection and/or antiretroviral treatment, differing from the ones described for individuals of other nationalities. However, when each patient was taken individually, particular alterations were detected for the Vbeta gene usage, compared to controls, for all individuals. After treatment, significant Vbeta usage changes were observed for seven patients. One or more chains on both T subsets were engaged in this process, defining a preferential oligoclonal profile for TCR repertoire distribution, after HAART. Although no pattern of specific Vbeta changes was detected in the circulating T cells, we cannot exclude that differential immune responses to HIV or other important antigens are being focused by these cells.

Memory responses in human immunodeficiency virus type 1-infected individuals with long-term viral load suppression are independent of CD4 cell nadir

The persistence of memory responses in suppressive highly active antiretroviral therapy (HAART) has been an area of controversy. By using a previously described proliferation assay that augments specific responses, peripheral blood lymphocytes (PBL) from 61 human immunodeficiency virus type 1-seropositive individuals with CD4 counts of >300/mm3 and suppressed viral burdens were studied for response to p24 antigen as a function of time of viral load suppression on HAART. In the majority of cases, proliferative responses could be measured in PBL from patients with plasma viral load suppression. No differences could be found in proliferative responses from PBL between individuals with a low and those with a high CD4 cell nadir. PBL that did not respond to either Casta antigen or p24 were found to have a higher percentage of naive cells than did PBL that responded well to antigen. These data support the contention that, after long-term viral load suppression, PBL from infected individuals have memory cell populations that can respond to antigenic stimulation under inducible conditions.

Human immunodeficiency virus type 1 (HIV-1)-specific CD4+ T cells that proliferate in vitro detected in samples from most viremic subjects and inversely associated with plasma HIV-1 levels

Diminished in vitro proliferation of human immunodeficiency virus type 1 (HIV-1)-specific CD4+T cells has been associated with HIV-1 viremia and declining CD4+ T-cell counts during chronic infection. To better understand this phenomenon, we examined whether HIV-1 Gag p24 antigen-induced CD4+ T-cell proliferation might recover in vitro in a group of subjects with chronic HIV-1 viremia and no history of antiretroviral therapy (ART). We found that depletion of CD8+ cells from peripheral blood mononuclear cells (PBMC) before antigen stimulation was associated with a 6.5-fold increase in the median p24-induced CD4+ T-cell proliferative response and a 57% increase in the number of subjects with positive responses. These p24-induced CD4+ T-cell proliferative responses from CD8-depleted PBMC were associated with expansion of the numbers of p24-specific, gamma interferon (IFN-gamma)-producing CD4+ T cells. Among the 20 viremic, treatment-naive subjects studied, the only 5 subjects lacking proliferation-competent, p24-specific CD4+ T-cell responses from CD8-depleted PBMC showed plasma HIV-1 RNA levels > 100,000 copies/ml. Furthermore, both the magnitude of p24-induced CD4+ T-cell proliferative responses from CD8-depleted PBMC and the frequency of p24-specific, IFN-gamma-producing CD4+ T cells expanded from CD8-depleted PBMC were associated inversely with plasma HIV-1 RNA levels. Therefore, proliferation-competent, HIV-1-specific CD4+ T cells that might help control HIV-1 disease may persist during chronic, progressive HIV-1 disease except at very high levels of in vivo HIV-1 replication.

Recent changes in the management of primary HIV-1 infection: results from the French PRIMO cohort

OBJECTIVES

To describe the management of primary HIV infection (PHI), focusing on changes in the design of therapies and time to initiation of antiretroviral treatment, the clinical outcome, and the immuno-virological response over time to highly active antiretroviral therapy (HAART) and its tolerance.

DESIGN AND METHODS

In the French PRIMO multicentre cohort, 291 patients presenting with PHI were enrolled between 1996 and 2001. Data were analysed to describe treatment prescription habits over a period of 5 years, and response to and tolerance of treatment.

RESULTS

The proportion of patients who initiated treatment during PHI decreased from 92% in 1996 to 56% in 2001. At 6 months, whatever the initiated treatment, 74% of treated patients achieved a plasma viral load<400 HIV-1 RNA copies/mL and 53% achieved a viral load of<50 copies/mL. Prescription of protease inhibitor (PI)-sparing regimens has become more frequent since 1999. Despite a similar virological response, patients in the PI-containing group tended to experience a greater 1-year increase in CD4 cell count than those in the non-nucleoside reverse transcriptase (NNRTI)-containing group (218 cells/microL versus 157 cells/microL, respectively). An adverse event was recorded in 51% of treated patients. The most frequent events were gastrointestinal disorders (71%), lipodystrophy (27%) and mood disorders (19%). The main reason for modifying or stopping therapy was the occurrence of an adverse event.

CONCLUSIONS

Limitations of therapy and poor tolerance to antiretroviral regimens have changed physician attitudes in PHI. This suggests the need for evaluation of better-tolerated regimens and new therapeutic strategies.

Prognostic value of proliferative responses to HIV-1 antigen in chronically HIV-infected patients under antiretroviral therapy

BACKGROUND

In the chronic stage of HIV infection T cell proliferative responses to HIV antigens are rare, mostly of low level, and the influence of responses on antiretroviral therapy is not known.

OBJECTIVES

To determine a potential correlation between HIV-specific proliferative responses and the subsequent course of infection under antiretroviral therapy.

STUDY DESIGN

Proliferation assays were performed with freshly isolated blood mononuclear cells from 45 chronically HIV-infected HAART treated individuals using HIV-p24, other recall antigens, and mitogens as stimulants. Virus load was monitored at the time of stimulation and during 33 months follow-up.

RESULTS

A proliferative response to HIV antigen stimulation was detectable in 7 of 45 patients (15.5% responders). This group showed elevated reactions against tetanus toxoid and tuberculin, whereas reactions against standard mitogens were equal in the HIV responder and nonresponder groups. None of the seven HIV-specific responders had a blood virus load rebound of more than 1000 genome copies/ml during follow-up, whereas in 50% of the non-responders higher virus rebounds occurred. CD4 cell levels were slightly higher in the responder group, but mostly independent of virus rebound within the non-responders. Only four patients with high and continuous virus rebound experienced a significant CD4 cell decline.

CONCLUSIONS

In patients under HAART, HIV-specific proliferative response is frequently related to anamnestic antigen responses and an enduring control of virus replication.

Dynamics of cytokine expression in HIV productively infected primary CD4+ T cells

Using intracellular p24 staining to discriminate between bystander and HIV productively infected cells, we evaluated the properties of HIV productively infected cells in terms of cytokine expression, activation status, apoptosis, and cell proliferation. We demonstrate that HIV productively infected primary CD4+ T cells express 12- to 47-fold higher type 1 cytokines than bystander or mock-infected cells. The frequency of HIV productive replication occurred predominantly in T-helper 1 (Th1), followed by Th0, then by Th2 cells. These productively infected cells expressed elevated levels of CD95, CD25, CXC chemokine receptor 4 (CXCR4), and CC chemokine receptor 5 (CCR5). While productively infected cells were only 1.8-fold higher in apoptosis frequency, they up-regulated the antiapoptotic protein B-cell leukemia 2 (Bcl-2) by 10-fold. Up-regulation of interleukin-2 (IL-2) and Bcl-2 were dependent on phosphatidylinositol-3-kinase signal transduction, given that it was down-regulated by Wortmanin treatment. Additionally, 60% of productively infected cells entered the cell cycle, as evaluated by Ki67 staining, but none divided, as evaluated by carboxyfluoresccin diacetate succinimidyl ester (CFSE) staining. Evaluation of cell cycle progression by costaining for DNA and RNA indicated that the cells were arrested in G2/M. Collectively, these data indicate that HIV replication occurs predominantly in Th1 cells and is associated with immune activation and up-regulation of Bcl-2, conferring a considerable degree of protection against apoptosis in the productively infected subpopulation. (Blood. 2004;103:4581-4587)

Evaluation of the impact of highly active antiretroviral therapy on immune recovery in antiretroviral naive patients

OBJECTIVES

To examine the extent of immune reconstitution in treatment-naive patients with CD4 T-cell counts <500 cells/microL following 48 weeks of highly active antiretroviral therapy (HAART).

METHODS

Thirteen antiretroviral naive patients were evaluated longitudinally for 48 weeks on HAART utilizing immune functional and lymphocyte phenotyping assays, including lymphocyte proliferation assay, flow cytometric evaluation of cell surface markers, and delayed type hypersensitivity skin tests. Virologic responses were monitored using commercially available viral load assays and gag/pol mRNA quantification using simultaneous immunophenotyping/UltraSensitive fluorescence in situ hybridization (ViroTect In Cell HIV-1 Detection Kit; Invirion, Frankfort, MI). Thymic function was evaluated for a subset of four patients using real-time polymerase chain reaction (PCR) for T-cell receptor excision circle (TREC) quantification and thymic scans using computerized axial tomography (CT) of the thymus.

RESULTS

HAART initiation resulted in a significant decline in plasma viremia and percentage of infected peripheral blood cells, and a rise in CD4 T cells from a baseline median of 207 cells/microL to a week-48 median of 617 cells/microL. The rise was predominately in CD4 memory cells. Naive T cells also increased in number, but at a slower rate. Activated (HLA-DR CD38) CD4 and CD8 T cells were elevated at baseline (24 and 62%, respectively) and declined by week 48 (17 and 36%, respectively) but did not reach normal levels. The number of Fas CD4 T cells increased from a baseline median of 169 to 381 cells/microL at week 48. Both soluble interleukin (IL)-2 and tumour necrosis factor (TNF) II receptors declined by week 48. HIV p24 lymphocyte proliferation assay responses were transiently detected in three patients. TREC values increased from a median 6400 copies/microg at baseline to a week-48 median value of 26 697 copies/microg.

CONCLUSION

Immune functional reconstitution was not achieved in these HAART naive patients.

CD38 expression on CD8 T lymphocytes as a marker of residual virus replication in chronically HIV-infected patients receiving antiretroviral therapy

The level of CD8+ CD38+ T lymphocytes in blood correlates with disease progression in HIV-infected individuals, independently of the CD4 count. Effective antiretroviral therapy reduces this lymphocyte subset in parallel with plasma viremia, although CD38 expression on CD8+ cells does not normalize completely in most subjects, and might reflect residual HIV replication. The expression of CD38 on CD8+ cells (as number of CD38 molecules per CD8+ cell) was measured quantitatively by flow cytometry in 200 individuals, of whom 170 were HIV positive and 30 were HIV-uninfected controls. Forty-six HIV-infected subjects were on antiretroviral therapy and had undetectable viral load. The remaining 124 HIV-positive persons were not on therapy and had detectable plasma viremia. The mean level of CD38 on CD8+ cells was higher in HIV-positive, untreated patients than in subjects on antiviral therapy and controls (5023, 2029, and 1978 molecules per CD8+ cell, respectively, p < 0.01). In HIV-positive, untreated subjects, the higher CD38 expression mainly occurred on CD45RO+ CD8+ cells. The level of CD38 strongly correlated with plasma HIV-RNA (r = 0.63, p < 0.001). The levels of CD38 on CD8+ cells declined steadily in HIV-positive subjects after beginning antiretroviral therapy. A few individuals presented viral blips whereas being on antiviral treatment, levels of CD38 on CD8+ cells increased transiently in parallel with episodes of viral replication. Levels of CD38 on CD8+ cells are increased in chronic HIV infection, and strongly correlate with plasma viremia. The slow decline of CD38 expression on CD8+ cells over time in subjects with undetectable plasma viremia while being on antiretroviral therapy suggests that CD38 expression on CD8+ cells could be used as a marker of residual virus replication.

The use of growth factors and cytokines to treat opportunistic infections in HIV-1 disease

The success of highly active antiretroviral therapy (HAART) in reducing AIDS-related mortality means that in regions where HAART is available, HIV infection may now be regarded as a chronic disease. However the inability of HAART to eliminate HIV-1 from various anatomical and cellular reservoirs within the body means that HIV-infected individuals require life-long treatment with therapy that can have significant side effects. Management of HIV disease is therefore increasingly focused on drug-related toxicities and the improvement of current HAART regimens. Here we review the potential use of immunomodulatory cytokines to directly or indirectly stimulate the mononuclear phagocyte system as adjuncts to current HIV treatment as well as their use in the management of opportunistic infections in individuals who develop immunodeficiency. We argue that cytokines, which stimulate mononuclear phagocyte activity against opportunistic pathogens, may be useful for the treatment of individuals who develop recurrent opportunistic infections. Cytokines may act synergistically with antimicrobial agents to improve outcomes, which is of particular importance since recurrent infections frequently result in resistance to standard antimicrobial treatments. Before their use can be advocated however, given their toxicity and significant cost, the potential benefits of cytokines must be demonstrated in larger clinical trials.

Treatment of primary HIV-1 infection with nonnucleoside reverse transcriptase inhibitor-based therapy is effective and well tolerated

OBJECTIVES

Highly active antiretroviral therapy (HAART) has been advocated for the management of primary HIV-1 infection. We investigated the use of a nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimen in this setting.

METHODS

Twenty-one antiretroviral-naïve individuals with early HIV-1 disease were treated with a combination of efavirenz and Combivir (GlaxoSmithKline, Uxbridge, Middlesex, UK). They were evaluated for immune and lymphocyte function by standard immunological assays.

RESULTS

The median time to an undetectable HIV-1 viral load was 12 weeks (range 4-36 weeks). CD4 and CD16/56 counts increased during treatment and CD8 counts decreased minimally. The main side-effects observed were transient sleep disturbances (five patients). In addition, we observed a decrease in lymphocyte activation as assessed by CD38 surface expression.

CONCLUSIONS

This study demonstrates that primary HIV-1 infection can be treated with NNRTI-based HAART.

Immune Restoration in Patients with HIV Infection: HAART and Beyond

Since the introduction of highly active antiretroviral therapy (HAART), there has been a dramatic decrease in HIV-related morbidity and mortality. Suppressing HIV replication by HAART can result in a restoration of the CD4+ T-cell count and, consequently, a diminished risk of opportunistic infections. However, the degree of immune restoration that can be achieved with HAART varies from patient to patient. It is often incomplete and can be poorest in those patients who, because of their very low CD4+ counts, need it the most. Additional approaches are needed to increase immune restoration still further. Structured treatment interruptions, therapeutic immunization, and recombinant interleukin-2 are three such options that are currently being investigated.

Diminished proliferation of human immunodeficiency virus-specific CD4+ T cells is associated with diminished interleukin-2 (IL-2) production and is recovered by exogenous IL-2

Virus-specific CD4(+) T-cell function is thought to play a central role in induction and maintenance of effective CD8(+) T-cell responses in experimental animals or humans. However, the reasons that diminished proliferation of human immunodeficiency virus (HIV)-specific CD4(+) T cells is observed in the majority of infected patients and the role of these diminished responses in the loss of control of replication during the chronic phase of HIV infection remain incompletely understood. In a cohort of 15 patients that were selected for particularly strong HIV-specific CD4(+) T-cell responses, the effects of viremia on these responses were explored. Restriction of HIV replication was not observed during one to eight interruptions of antiretroviral therapy in the majority of patients (12 of 15). In each case, proliferative responses to HIV antigens were rapidly inhibited during viremia. The frequencies of cells that produce IFN-gamma in response to Gag, Pol, and Nef peptide pools were maintained during an interruption of therapy. In a subset of patients with elevated frequencies of interleukin-2 (IL-2)-producing cells, IL-2 production in response to HIV antigens was diminished during viremia. Addition of exogenous IL-2 was sufficient to rescue in vitro proliferation of DR0101 class II Gag or Pol tetramer(+) or total-Gag-specific CD4(+) T cells. These observations suggest that, during viremia, diminished in vitro proliferation of HIV-specific CD4(+) T cells is likely related to diminished IL-2 production. These results also suggest that relatively high frequencies of HIV-specific CD4(+) T cells persist in the peripheral blood during viremia, are not replicatively senescent, and proliferate when IL-2 is provided exogenously.

CD8+ T cells that express CD4 on their surface (CD4dimCD8bright T cells) recognize an antigen-specific target, are detected in vivo, and can be productively infected by T-tropic HIV

CD4 can be up-regulated on CD8+ T cells generating a CD4dimCD8bright phenotype. We previously demonstrated that the CD4dimCD8bright phenotype constitutes an activated phenotype of CD8+ T cells. We demonstrate here that the activated CD4dimCD8bright T cells are not undergoing apoptosis and do not produce significant intracellular levels of interferon gamma (IFNgamma), interleukin 2 (IL-2), or IL-10 but express elevated levels of intracellular IL-4 in comparison to CD8+CD4- and CD4+ T cells. In response to cytomegalovirus (CMV) peptide (pp65) priming, CD4dimCD8bright cells recognized CMV pp65 tetramer approximately 19-fold higher than CD4-CD8+ T cells, indicating that these cells are capable of antigen-specific recognition to a far greater extent than CD4-CD8+ T cells. CD4dimCD8bright T cells also express both CXCR4 and CCR5 but are susceptible to T-tropic and not M-tropic HIV infection. A soluble factor believed to be beta-chemokine is responsible for the inhibition of M-tropic HIV infection in CD4dimCD8bright T cells. CD8+ T cells from HIV+ patients were capable of up-regulating CD4 on CD8+ T cells. We also provide evidence of the presence of peripheral blood CD4dimCD8bright T cells in HIV+ patients, albeit at low frequency. Collectively, these data suggest a role of CD4dimCD8bright T cells in both normal T-cell biology and HIV pathogenesis.

Nucleoside analogue mutations and Q151M in HIV-1 subtype A/E infection treated with nucleoside reverse transcriptase inhibitors

OBJECTIVES

To investigate genotypic drug resistance in HIV-1 subtype A/E infection associated with failure of double/triple-nucleoside reverse transcriptase (RT) inhibitor therapy.

METHODS

Patients from HIV-NAT 002 [stavudine (d4T)/didanosine (ddI) dose reduction study] and HIV-NAT 003 (zidovudine (ZDV)/lamivudine (3TC) versus ZDV/3TC/ddI) whose HIV-1 RNA was > 1000 copies/ml at week 48 and/or week 96 were tested for genotypic resistance. In both studies, after 48 weeks, patients were switched to the other dual or triple-nucleoside RT inhibitor (NRTI) either according to randomization or to the occurrence of virological failure.

RESULTS

Resistance mutations found in the d4T/ddI, ZDV/3TC, and ZDV/3TC/ddI groups: none at baseline; at week 48, nucleoside analogue mutations (NAM), 2/17 (12%), 2/10 (20%), and 1/8; Q151M complex, 3/17 (18%), 0%, and 0%; M184V, 0%, 10/10 (P < 0.001), 3/8; V75T, 3/17 (18%), 0%, and 0%; L74V, 3/7 (18%), 0%, and 0%, respectively. At week 96, among the switchers, i.e., group A d4T/ddI to ZDV/3TC, group B ZDV/3TC to d4T/ddI, and group C ZDV/3TC/ddI to d4T/3TC/abacavir: NAM, 12/21 (57%), 4/7 and 1/3; Q151M, 4/21 (19%), 0% and 1/3, respectively. Interestingly, four or more NAM were observed in a higher proportion in group A (4/17 versus none in the others).

CONCLUSIONS

Multi-NRTI resistance (NAM and Q151M) and M184V (only in 3TC failure) are commonly found in HIV-1 subtype A/E infection associated with NRTI failure. Suboptimal d4T/ddI therapy led to a high incidence of V75T and L74V mutations. Switching from d4T/ddI to ZDV/3TC may be associated with a higher incidence of four or more NAM. Thus, suboptimal and dual NRTI therapy is not recommended for global application.

Immunity to human immunodeficiency virus (HIV) in children with chronic HIV infection receiving highly active antiretroviral therapy

Our objective was to describe the CD4-mediated human immunodeficiency virus (HIV)-specific cell-mediated immunity (CMI) and its virologic and immunologic correlates in children with chronic HIV infection on highly active antiretroviral therapy (HAART). Twelve HIV-infected children on stable antiretroviral therapy with a median level of CD4+ lymphocytes (CD4%) of 25.5% and a median viral load (VL) of 786 HIV RNA copies/ml were enrolled in this study. Nine of these children were also cytomegalovirus (CMV) seropositive. Blood mononuclear cells, stimulated with HIV and CMV antigens, were used to measure lymphocyte proliferation and to enumerate gamma interferon (IFN-gamma)-producing CD4+ cells. HIV CMI and CMV CMI were detected in similar proportions of patients and correlated with each other, although the HIV responses were less robust. HIV lymphocyte proliferation significantly increased with lower HIV VL and showed a trend to increase with higher CD4% and longer time on HAART. The in vitro IFN-gamma response to HIV or CMV was not affected by CD4%, VL, or HAART. Pediatric patients with established HIV infection on HAART frequently exhibit HIV CMI despite undetectable HIV replication. We concluded that the association between HIV CMI and CMV CMI indicates that the same factors govern responsiveness to either antigen.

Antigen-presenting cell modulation induces a memory response to p24 in peripheral blood leukocytes from human immunodeficiency virus-infected individuals

The accurate determination of human immunodeficiency virus type 1 (HIV-1)-specific proliferative responses is critically important when evaluating immune recovery after highly active antiretroviral therapy. Using a new assay to enhance proliferative responses to recall and HIV antigen, we addressed the questions of whether viral load affects cellular immunity and whether long-term viral load suppression results in loss of antigen-specific responder cells. This assay is based on the fact that lipopolysaccharide (LPS) can augment proliferative responses to antigen after monocyte adherence to a tissue culture plate. Twenty-six HIV-1-infected individuals donated peripheral blood leukocytes (PBL). Proliferation assays against p24, using LPS and cell adherence, were performed on all samples. Medical record abstraction provided information on CD4 cell nadir and time of viral load suppression. PBL from HIV-1-infected individuals with a viral load of <200 copies/ml had a significant proliferative response and a stimulation index of >5 to p24 (12 of 15) compared to those with a viral burden (2 of 11), using the LPS-adherence assay. Proliferative responses to p24 could be found in PBL from virally suppressed donors independent of the CD4 cell nadirs and in the majority of the donors who were virally suppressed for >10 months (7 of 10). The data presented here demonstrate that LPS and monocyte adherence provide a sensitive and specific way to boost proliferative responses to recall and HIV antigens.

Restoration of human immunodeficiency virus-1-specific responses in patients changing from protease to non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy

The effect of altering antiretroviral therapy (ART) on responses to viral, recall and human immunodeficiency virus (HIV)-1-specific recombinant antigens and interleukin-2 (IL-2) in HIV-1-infected patients was assessed. A longitudinal cohort study in eight HIV-1 infected individuals following a clinically indicated therapy change (seven for drug intolerance and one for virological failure) from protease inhibitor (PI) to non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral regimens was performed. CD4 T-cell counts, viral loads, lymphoproliferative responses, cytokine production and latent proviral deoxyribonucleic acid (DNA) were measured at baseline and at weeks 12 and 24 after therapy substitution. Following therapy-switch there was a 33% proportional increase in mitogen response (95% confidence interval (CI), 3-33%) and a 31% increase (95% CI, 15-48%) in viral and recall-antigen responses. Six patients developed proliferative responses to low concentration IL-2 stimulation. All patients demonstrated an increase in median HIV-1-specific responses, as three had detectable virus at baseline (two being viral rebound); this may reflect an autovaccination effect. Proviral DNA changes largely reflected plasma HIV-1 ribonucleic acid (RNA). In conclusion, NNRTI substitution for a PI may favour immune reconstitution with an improvement in HIV-1-specific responses, which may reflect differential effects on antigen processing and presentation, an autovaccination effect or alternatively a potential suppressive effect of the PI.

Diverse repertoire of HIV-1 p24-specific, IFN-gamma-producing CD4+ T cell clones following immune reconstitution on highly active antiretroviral therapy

HIV-1 Ag-specific CD4(+) T cell proliferative responses in human subjects with advanced, untreated HIV-1 disease are often weak or undetectable. Conversely, HIV-1-specific CD4(+) T cell proliferation is occasionally detected following suppression of HIV-1 replication with highly active antiretroviral therapy (HAART). These observations suggest that unchecked HIV-1 replication may lead to depletion or dysfunction of HIV-1-specific CD4(+) T cells, and that these defects may be partially corrected by viral suppression and subsequent immune reconstitution. However, the impact of this immune reconstitution on the repertoire of HIV-1-specific CD4(+) T cells has not been thoroughly evaluated. To examine the HIV-1-specific CD4(+) T cell repertoire in this clinical setting, we established HIV-1 p24-specific CD4(+) T cell clones from a successfully HAART-treated subject whose pretreatment peripheral CD4 count was 0 cells/ micro l. Eleven different p24-specific CD4(+) T cell clonotypes were distinguished among 13 clones obtained. Most clones produced both IFN-gamma and IL-4 upon Ag stimulation. Clones targeted eight distinct epitopes that varied in their conservancy among HIV-1 strains, and responses were restricted by one of three MHC II molecules. Clones showed a range of functional avidities for both protein and peptide Ags. Additional studies confirmed that multiple HIV-1 p24-derived epitopes were targeted by IFN-gamma-producing CD4(+) cells from subjects first treated with HAART during advanced HIV-1 disease (median, 4.5 peptides/subject; range, 3-6). These results suggest that in HAART-treated subjects whose peripheral CD4(+) T cell pools were once severely depleted, the HIV-1-specific CD4(+) T cell repertoire may include a diverse array of clonotypes targeting multiple HIV-1 epitopes.

Immune intervention strategies for HIV-1 infection of humans in the SIV macaque model

Studies in the SIVmac macaque model have demonstrated that the extent of virus-specific CD4+ and CD8+ T-cell responses induced by vaccination prior to virus-challenge exposure correlate with viremia containment following establishment of infection. These findings led to the hypothesis that active immunization with vaccines able to induce virus-specific T-cell responses following the establishment of infection could also ameliorate the virological outcome. Here, we will review the relative effect of ART and vaccination during primary SIVmac infection of macaques.

Entrapment of recent thymic emigrants in lymphoid tissues from HIV-infected patients: association with HIV cellular viral load

OBJECTIVE(S)

Depletion of thymus derived naive T-cells is a feature of HIV infection. Here the impact of HIV infection on the compartmentalization of recent thymic emigrants of (RTE) and naive T-cells was examined.

METHODS

Peripheral blood mononuclear cells (PBMC) and lymphoid tissue (LT) from 43 HIV-infected patients and 12 controls were examined for RTE distribution by measuring coding joint T-cell receptor excisional circles (cjTREC) by PCR and naive and memory T-cell subsets and adhesion molecules (L-selection, LFA-1) by flow cytometry.

RESULTS

In HIV-infected patients, the RTE as quantified by cjTRECs in CD4 LT cells were significantly higher than in PBMC. Their values, however, were less than in control subjects, in both the LT and PBMC compartments. This was associated with an increase in L-selectin and LFA-1 expression on LT derived T cells. In PBMC, a significant positive relationship between TREC and naive CD4 cells and an inverse relationship between TREC and cellular viral load (CVL) was observed. Whereas in LT, there was a positive relationship between cjTREC and both naive CD4 cell percentage and CVL.

CONCLUSIONS

Collectively, the data suggests that LT is a significant reservoir for RTE. The RTE appeared to be entrapped in LT from HIV-infected subjects. Such entrapment is probably a response to the high viral load in these tissues. These observations may partially explain the decline in RTE observed in the peripheral blood of HIV-infected patients, and the delay in recovery of naive cells in blood after initiation of HAART.

Immune recovery in HIV disease: role of the thymus and T cell expansion in immune reconstitution strategies

While the progressive depletion of CD4(+) T cells is the hallmark of the impact of HIV on the immune system, considerable data also point to the loss of T cell function. The question is: Can the immune system recover from this insult and what are the therapeutic strategies available to us to mediate this immune recovery? This review will focus on our current knowledge of immune recovery following treatment with highly active antiretroviral therapy (HAART). Enhancement of thymic function in generating de novo T cell synthesis post-HAART has also emerged as a viable immune recovery strategy. Advances in molecular (T cell receptor excision circle assay) and conventional (computed tomography scans of the thymus) approaches to evaluate the role of the thymus in immune recovery as well as potential agents that might enhance thymic output (interleukin-7, IL-7) will contribute greatly to the assessment of the success of these approaches as immune recovery strategies. In this review, we will integrate this new information in the context of the current strategies for HIV therapy leading to long-term immune reconstitution.

The Role of CD4(+) and CD8(+) T Cells in Controlling HIV Infection

Presently, it is thought that virus-specific T cells play a major role in restricting lentiviral replication and determining the rate of disease progression in humans. However, it remains unclear why this restriction fails in the majority of infected individuals. The major exception is a rare subgroup of HIV-infected long-term nonprogressors (LTNPs) who have been infected for approximately 20 years yet maintain normal CD4(+) T-cell counts and less than 50 copies of viral RNA/mL of plasma. Although virus-specific cellular (CD4(+) and CD8(+) T lymphocytes) immune responses have been shown to exert some degree of in vivo control of HIV replication, the precise correlates of protective immunity differentiating LTNPs from patients with progressive disease remain unknown. A greater understanding of the components and magnitude of an effective immune response to HIV is an important step toward the development of effective vaccines and immunotherapies.