Immunologic Reconstitution After 1 Year of Highly Active Antiretroviral Therapy, With or Without Protease Inhibitors:

Advances in Mechanism of HIV-1 Immune Reconstitution Failure: Understanding Lymphocyte Subpopulations and Interventions for Immunological Nonresponders

In individuals diagnosed with AIDS, the primary method of sustained suppression of HIV-1 replication is antiretroviral therapy, which systematically increases CD4+ T cell levels and restores immune function. However, there is still a subset of 10-40% of people living with HIV who not only fail to reach normal CD4+ T cell counts but also experience severe immune dysfunction. These individuals are referred to as immunological nonresponders (INRs). INRs have a higher susceptibility to opportunistic infections and non-AIDS-related illnesses, resulting in increased morbidity and mortality rates. Therefore, it is crucial to gain new insights into the primary mechanisms of immune reconstitution failure to enable early and effective treatment for individuals at risk. This review provides an overview of the dynamics of key lymphocyte subpopulations, the main molecular mechanisms of INRs, clinical diagnosis, and intervention strategies during immune reconstitution failure, primarily from a multiomics perspective.

Comparative Impact of Suppressive Antiretroviral Regimens on the CD4/CD8 T-Cell Ratio: A Cohort Study

Although different factors have been implicated in the CD4/CD8 T-cell ratio recovery in HIV-infected patients who receive effective antiretroviral therapy (ART), limited information exists on the influence of the regimen composition. A longitudinal study carried out in a prospective, single-center cohort of HIV-infected patients. ART regimens including non-nucleoside reverse transcriptase inhibitors (NNRTI), protease inhibitors (PI), or integrase strand transfer inhibitors (INSTI) from patients who achieved long-term (≥6-month duration) virological suppression (HIV-RNA < 400 copies/mL) from January 1998 to June 2014 were analyzed. The impact of ART composition on the changes of the CD4/CD8 T-cell ratio was modeled using a mixed linear approach with adjustment for possible confounders. A total of 1068 ART regimens from 570 patients were analyzed. Mean (SD) age of the patients was 42.15 (10.68) years and 276 (48.42%) had hepatitis C virus (HCV) coinfection. Five hundred fifty-eight (52.25%) regimens were PI-based, 439 (40.10%) NNRTI-based, and 71 (6.65%) INSTI-based; 487 (45.60%) were initial regimens, 476 (44.57%) simplification, and 105 (9.83%) salvage regimens. Median (IQR) number of regimens was 1 (1-2) per patient, of 29 (14-58) months duration, and 4 (3-7) CD4/CD8 measurements per regimen. The median baseline CD4/CD8 ratio was 0.42, 0.50, and 0.54, respectively, with the PI-, NNRTI-, and INSTI-based regimens (P = 0.0073). Overall median (IQR) increase of CD4/CD8 ratio was 0.0245 (-0.0352-0.0690) per year, and a CD4/CD8 ratio ≥1 was achieved in 19.35% of the cases with PI-based, 25.97% with NNRTI-based, and 22.54% with INSTI-based regimens (P = 0.1406). In the adjusted model, the mean CD4/CD8 T-cell ratio increase was higher with NNRTI-based regimens compared for PI-based (estimated coefficient for PI [95% CI], -0.0912 [-0.1604 to -0.0219], P = 0.009). Also, a higher CD4/CD8 baseline ratio was associated with higher CD4/CD8 increase in the adjusted model (P = 0.001); by contrast, higher age (P = 0.020) and simplification of ART regimen (P = 0.003) had a negative impact on the CD4/CD8 ratio. Antiretroviral regimen composition has a differential impact on the CD4/CD8 T-cell ratio; NNRTI-based regimens are associated with enhanced CD4/CD8 T-cell ratio recovery compared to PI-based antiretroviral regimens.

Amino-acid co-variation in HIV-1 Gag subtype C: HLA-mediated selection pressure and compensatory dynamics

Background

Despite high potential for HIV-1 genetic variation, the emergence of some mutations is constrained by fitness costs, and may be associated with compensatory amino acid (AA) co-variation. To characterize the interplay between Cytotoxic T Lymphocyte (CTL)-mediated pressure and HIV-1 evolutionary pathways, we investigated AA co-variation in Gag sequences obtained from 449 South African individuals chronically infected with HIV-1 subtype C.

Methodology/Principal Findings

Individuals with CTL responses biased toward Gag presented lower viral loads than individuals with under-represented Gag-specific CTL responses. Using methods that account for founder effects and HLA linkage disequilibrium, we identified 35 AA sites under Human Leukocyte Antigen (HLA)-restricted CTL selection pressure and 534 AA-to-AA interactions. Analysis of two-dimensional distances between co-varying residues revealed local stabilization mechanisms since 40% of associations involved neighboring residues. Key features of our co-variation analysis included sites with a high number of co-varying partners, such as HLA-associated sites, which had on average 55% more connections than other co-varying sites.

Conclusions/Significance

Clusters of co-varying AA around HLA-associated sites (especially at typically conserved sites) suggested that cooperative interactions act to preserve the local structural stability and protein function when CTL escape mutations occur. These results expose HLA-imprinted HIV-1 polymorphisms and their interlinked mutational paths in Gag that are likely due to opposite selective pressures from host CTL-mediated responses and viral fitness constraints.

Clinical deterioration during antituberculosis treatment in Africa: incidence, causes and risk factors

BACKGROUND

HIV-1 and Mycobacterium tuberculosis cause substantial morbidity and mortality. Despite the availability of antiretroviral and antituberculosis treatment in Africa, clinical deterioration during antituberculosis treatment remains a frequent reason for hospital admission. We therefore determined the incidence, causes and risk factors for clinical deterioration.

METHODS

Prospective cohort study of 292 adults who initiated antituberculosis treatment during a 3-month period. We evaluated those with clinical deterioration over the following 24 weeks of treatment.

RESULTS

Seventy-one percent (209/292) of patients were HIV-1 infected (median CD4+: 129 cells/microL [IQR:62-277]). At tuberculosis diagnosis, 23% (34/145) of HIV-1 infected patients qualifying for antiretroviral treatment (ART) were receiving ART; 6 months later, 75% (109/145) had received ART. Within 24 weeks of initiating antituberculosis treatment, 40% (117/292) of patients experienced clinical deterioration due to co-morbid illness (n = 70), tuberculosis related illness (n = 47), non AIDS-defining HIV-1 related infection (n = 25) and AIDS-defining illness (n = 21). Using HIV-1 uninfected patients as the referent group, HIV-1 infected patients had an increasing risk of clinical deterioration as CD4+ counts decreased [CD4+>350 cells/microL: RR = 1.4, 95% CI = 0.7-2.9; CD4+:200-350 cells/microL: RR = 2.0, 95% CI = 1.1-3.6; CD4+<200 cells/microL: RR = 3.0, 95% CI = 1.9-4.7]. During follow-up, 26% (30/117) of patients with clinical deterioration required hospital admission and 15% (17/117) died. Fifteen deaths were in HIV-1 infected patients with a CD4+<200 cells/microL.

CONCLUSIONS

In multivariate analysis, HIV-1 infection and a low CD4+ count at tuberculosis diagnosis were significant risk factors for clinical deterioration and death. The initiation of ART at a CD4+ count of <350 cells/microL will likely reduce the high burden of clinical deterioration.

Three-Year Immune Reconstitution in PI-Sparing and PI-Containing Antiretroviral Regimens in Advanced HIV-1 Disease

Background

The long-term immunological benefit of protease inhibitor (PI)-sparing antiretroviral therapy (ART) using non-nucleoside reverse transcriptase inhibitors (NNRTIs) remains poorly investigated.

Methods

A total of 120 ART-naive, HIV-1-infected participants were included in the immunology substudy of INITIO, an international randomized trial comparing two NRTIs (didanosine + stavudine) combined with either: one NNRTI (efavirenz; EFV), one non-boosted PI (nelfinavir; NFV), or one NNRTI + one PI (EFV/NFV). CD4+ T-cell counts, HIV-1 plasma RNA load (VL), T-cell pheno-type, T-cell proliferation and IFN-γ production against opportunistic/recall and HIV-1 antigens/peptides were compared at baseline and at week (W) 96 and W156.

Results

Participants (37 EFV, 44 NFV, 39 EFV/NFV) had similar baseline VL; median CD4+ T-cell counts/mm3 were: 144 (64–303) EFV, 212 (42–313) NFV and 257 (86–331) EFV/NFV. At W156, the proportion of patients with VL ≤50 copies/ml was not different between the arms ( P=0.3). From baseline to W156 there was a significant increase in CD4+ T-cell counts ( P<0.001) and in naive CD4+ T cells ( P<0.001), with no difference between arms and percentages of total and activated CD8+ T cells decreased significantly ( P<0.001) in all arms. The decrease in activated memory CD4+T-cells was significantly greater in the EFV arm at W96 ( P=0.03) and W156 ( P=0.01), but did not persist after adjusting for baseline CD4+ T-cell counts. During follow-up, responses to opportunistic pathogens increased in all patients while specific T-cell responses to HIV-1-p24 and gp160 recombinant proteins or to Gag and Nef peptides were not restored.

Conclusion

Regimens using/sparing PIs provide similar levels of long-term immune reconstitution even in patients with low CD4+ T-cell counts.

Effects of highly active antiretroviral therapy and immune recovery on CD8+ T-cell-mediated inhibition of HIV-1 transcription

SUMMARY

: To date, the relation between the CD8 antiviral factor (CAF) and clinical indicators of disease progression in HIV-1 infection (CD4 T-cell counts and viral load [VL]) is inconclusive. Particularly, the effect of antiretroviral therapy and immune recovery on CAF production remains unclear. Using a transient transfection assay and a reporter gene activated by the HIV-1 long terminal repeat (LTR), we analyzed CAF production in CD8 T cells of HIV-1-positive individuals divided into 3 groups: patients on protease inhibitor (PI)-based therapy, patients on nonnucleoside reverse transcriptase inhibitor (NNRTI)-based therapy, and patients receiving no therapy. We found that within the untreated group, CAF activity inversely correlated with VL and high CAF was associated with lower VLs over a period of 0.5 to 3 years. Furthermore, patients who were drug-naive demonstrated significantly higher CAF than untreated patients who had previously undergone antiretroviral therapy. CAF activity in treated patients was similar to CAF in drug-naive patients and higher than in off-treatment patients. There seemed to be a trend toward higher CAF in patients on NNRTI-based therapy compared with those on PI-based therapy. These results suggest that immune recovery after highly active antiretroviral therapy (HAART) contributes to the normalization of CAF levels in HIV-1-positive individuals. Furthermore, we have distinguished between CD8 T-cell-mediated suppression of HIV-1 replication and gene transcription.

Monocyte derived dendritic cells from HIV-1 infected individuals partially reconstitute CD4 T-cell responses

OBJECTIVES

The study tests the hypothesis that monocyte derived dendritic cells from HIV-1 infected individuals are normal and can restore impaired CD4 T-cell antigen specific responses.

DESIGN

Monocyte derived dendritic cells were isolated from individuals at three different stages of HIV-1 infection with a wide spectrum of viral load and CD4 T-cell counts, and from healthy volunteers. The cell surface phenotype and allogeneic stimulatory potential of these dendritic cells was documented. CD4 T-cell responses to HIV p24, tetanus toxoid and purified protein derivative were measured using either unfractionated peripheral blood mononuclear cells, or purified dendritic cell/T-cell cultures.

RESULTS

Dendritic cells from all three HIV-1 infected groups did not differ from each other or from healthy volunteers in terms of cell surface phenotype or allogeneic stimulatory potential using T cells from healthy volunteers. Dendritic cells from immunosuppressed antiretroviral naive individuals enhanced the autologous recall proliferative responses both to HIV-1 p24, and third party antigens tetanus toxoid and purified protein derivative, both in terms of the proportion of responding individuals, and median proliferation.

CONCLUSION

Antigen presentation by dendritic cells partially restores impaired antigen specific CD4 T-cell responses associated with HIV-1 infection. Immunization strategies which target dendritic cells may therefore offer significant advantages in the ability to stimulate HIV-specific protective immune responses.

Restoration of CD4 T-cell responses to cytomegalovirus is short-lived in severely immunodeficient HIV-infected patients responding to highly active antiretroviral therapy

OBJECTIVES

To define the level of pathogen-specific immune reconstitution persisting over 3 to 5 years of highly active antiretroviral therapy (HAART) in HIV-infected patients who began therapy with CD4 T-cell counts below 50 cells/microL.

METHODS

Cytomegalovirus (CMV)-specific T-cell responses were analysed in adult HIV-1-infected patients with nadir CD4 T-cell counts below 50 cells/microL before HAART. CMV-specific CD4 T-cell responses were measured by interferon-gamma enzyme-linked immunospot assay (ELISpot assay), lymphoproliferation and interferon-gamma levels in cell culture supernatants.

RESULTS

CD4 T-cell responses to CMV were low in untreated patients and remained low during the first year on HAART, but increased progressively to levels similar to those found in HIV-seronegative CMV-seropositive controls at 3 years. Responses then declined markedly and at 5 years were lower than controls. This could not be explained by changes in CD4 or CD8 T-cell counts or plasma HIV RNA levels. Interferon-gamma and interleukin-5 responses to a mitogen were maintained or elevated.

CONCLUSIONS

CMV-specific CD4 T-cell responses were found to decline after 3-5 years on HAART and may provide inadequate long-term protection against CMV disease in patients who are severely immunodeficient prior to treatment.

Immune Restoration in HIV-Positive, Antiretroviral-Naive Patients after 1 Year of Zidovudine/Lamivudine plus Nelfinavir or Nevirapine

Objectives

To evaluate the immunological response in HIV-1-infected, antiretroviral-naive patients receiving highly active antiretroviral therapy regimen of two nucleosides plus a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor.

Design and methods

Of 142 patients included in a randomized, open, multicentre trial comparing zidovudine/lamivudine plus nelfinavir (NFV) or nevirapine (NVP), 36 patients (16 NFV, 20 NVP) were enrolled in an immunological substudy. Mean baseline CD4 T-cell counts was 360/mm3 (range: 11–679) and mean baseline plasma viral load >50 000 copies/ml (range: 2240–1468210). Viral load (VL), T-cell subsets and T-cell functions were analysed at baseline and after 1 year of treatment.

Results

After 12 months of follow-up, plasma viral load was reduced similarly in both groups, with 78% (NFV) and 83% (NVP) of patients achieving a VL <200 copies/ml. A significant increase in CD4 T cells was observed in both groups (mean: +182 cells, P=0.001). Both regimens were similarly effective in reducing activated T cells (CD38 and DR). A significant increase of both CD4 and CD8 CD28 T cells occurred in both arms of treatment. Patients of both regimens showed a significant decrease of activated memory (CD45RA–CD45RO+) CD8 T cells and a clear increase of naive (CD45RA+CD45RO-) CD8 T cells. Peripheral blood mononuclear cell proliferative responses to polyclonal stimuli (CD3 and CD3 +CD28) as well as to ubiquitous cytomegalovirus antigen increased significantly in both groups after 12 months of follow-up. Nevertheless, neither at baseline nor after 1 year of treatment, these patients showed any significant T-cell responsiveness to HIV-1 recombinant proteins gp160 or p24.

Conclusions

Our data indicate that immune restoration achieved after 1 year of therapy with either NFV or NVP was similar. This reinforces the role of NVP-containing regimens as a valid option for initiating antiretroviral therapy. Nevertheless, additional therapeutic approaches should be envisaged to restore HIV-1-specific T-cell responses.

Hydroxyurea in the treatment of HIV infection: clinical efficacy and safety concerns

Data from basic science and clinical studies suggest that hydroxyurea (hydroxycarbamide)-based regimens are effective treatment options for patients with HIV at various stages of disease. In vitro studies of HIV-infected lymphocytes have shown that hydroxyurea: (i) inhibits viral DNA synthesis; (ii) synergistically interacts with nucleoside reverse transcriptase inhibitors (NRTI); and (iii) increases the antiviral activity of didanosine. Clinical studies have confirmed that hydroxyurea in combination with didanosine produces potent and sustained viral suppression in patients with HIV infection. However, some concerns have been recently raised on the use of hydroxyurea in association with NRTI. Hydroxyurea can cause myelosuppression, skin toxicities, mild gastrointestinal toxicity, and abnormalities of renal and liver functions. In addition, hydroxyurea may accentuate the toxic effects of nucleoside analogues. In fact, some clinical data seem to indicate an increased risk of pancreatitis and neuropathy when hydroxyurea is combined with didanosine and stavudine. Since hydroxyurea-related toxicity is dose dependent, a systematic study of hydroxyurea optimal dosage and schedule was initiated to monitor patients for possible nucleoside toxicity. In the Research Institute for Genetic and Human Therapy (RIGHT) 702 study it was shown that a low, well-tolerated hydroxyurea dose (600 mg daily) achieved better antiretroviral activity than higher doses, together with better CD4+ cell count increase and fewer adverse effects. In this paper the effects of hydroxyurea as salvage therapy for heavily pretreated patients with advanced HIV disease are presented. These studies have shown that some patients with extensive pretreatment experience and advanced disease can respond substantially to the addition of hydroxyurea. The addition of hydroxyurea to didanosine does not prevent the emergence of resistance to didanosine; nonetheless, the efficacy of this therapeutic regimen may not be attenuated by the presence of didanosine-resistant HIV mutants. Since CD4 T lymphocyte activation is essential for virus replication and CD8 T lymphocyte activation may contribute to pathogenesis, the combination of hydroxyurea with other drugs may lead to the inhibition of HIV, by blocking the 'cell activation-virus production-pathogenesis' cycle. Clinical data indicate that hydroxyurea may play a role in attenuation of viral rebound and immune reconstitution by decreasing CD4 T cell proliferation, as well as preventing the exhaustion of CD8 T cell populations that may result from excessive activation during HIV infection. While the combination of hydroxyurea with didanosine has provided hope, future studies including those that evaluate optimal dosing and long-term toxicity are needed to define the role for this agent in the treatment of HIV infection.