Defective IL-2 production by HIV-1-specific CD4 and CD8 T cells in an adolescent/young adult cohort

Elevated Numbers of HIV-Specific Poly-Functional CD8+ T Cells With Stem Cell-Like and Follicular Homing Phenotypes in HIV-Exposed Seronegative Individuals

HIV-specific CD8⁺ T cells are known to play a key role in viral control during acute and chronic HIV infection. Although many studies have demonstrated the importance of HIV-specific CD8⁺ T cells in viral control, its correlation with protection against HIV infection remains incompletely understood. To better understand the nature of the immune response that contributes to the early control of HIV infection, we analyzed the phenotype, distribution and function of anti-viral CD8⁺ T cells in a cohort of HIV-exposed seronegative (HESN) women, and compared them with healthy controls and HIV-infected individuals. Further, we evaluated the in vitro viral inhibition activity of CD8⁺ T cells against diverse HIV-1 strains. We found that the HESN group had significantly higher levels of CD8⁺ T cells that express T-stem cell-like (TSCM) and follicular homing (CXCR5⁺) phenotype with more effector like characteristics as compared to healthy controls. Further, we observed that the HESN population had a higher frequency of HIV-specific poly-functional CD8⁺ T cells with robust in vitro virus inhibiting capacity against different clades of HIV. Overall, our results demonstrate that the HESN population has elevated levels of HIV-specific poly-functional CD8⁺ T cells with robust virus inhibiting ability and express elevated levels of markers pertaining to TSCM and follicular homing phenotype. These results demonstrate that future vaccine and therapeutic strategies should focus on eliciting these critical CD8⁺ T cell subsets.

HIV therapeutic vaccines: moving towards a functional cure

Anti-viral T-cell and B-cell responses play a crucial role in suppressing HIV and SIV replication during chronic infection. However, these infections are rarely controlled by the host immune response, and most infected individuals need lifelong antiretroviral therapy (ART). Recent advances in our understanding of how anti-HIV immune responses are elicited and regulated prompted a surge of interest in harnessing these responses to reduce the HIV 'residual disease' that is present in ART-treated HIV-infected individuals. Novel approaches that are currently explored include both conventional therapeutic vaccines (i.e., active immunization strategies using HIV-derived immunogens) as well as the use of checkpoint blockers such as anti-PD-1 antibodies. These approaches appear promising as key components of complex therapeutic strategies aimed at curing HIV infection.

TB-IRIS after initiation of antiretroviral therapy is associated with expansion of preexistent Th1 responses against Mycobacterium tuberculosis antigens

BACKGROUND

The role of T-cell responses against Mycobacterium tuberculosis antigens in tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is unclear.

METHODS

Peripheral blood mononuclear cells from 45 HIV patients with treated TB, of whom 12 developed TB-IRIS, were collected at weeks 0, 2, and 6 of antiretroviral therapy (ART). Production of interferon-gamma (IFN-γ) and interleukin-2 by T cells after stimulation with purified protein derivative (PPD) or early secretory antigenic target-6 (ESAT-6) and T-cell expressions of CCR5 and CXCR3 were assessed by flow cytometry. IFN-γ and CXCL10 were assayed by enzyme-linked immunosorbent assay.

RESULTS

TB-IRIS patients had higher proportions of PPD- and ESAT-6-reactive IFN-γ⁺CD4⁺ and CD3⁺CD4⁻ T cells at weeks 0, 2, and 6. IFN-γ levels were also higher in peripheral blood mononuclear cell culture supernatants at all times with PPD but only at weeks 2 and 6 with ESAT-6. There were few differences for interleukin-2. CXCL10 levels in supernatants after PPD and ESAT-6 stimulation were only higher at week 6. CXCR3⁺/CCR5⁺CD4⁺ T cells were higher at week 2, and CCR5⁺CD4⁺ T cells were higher at week 6.

CONCLUSIONS

TB-IRIS is associated with Th1 responses against M. tuberculosis antigens by CD4⁺ and CD3⁺CD4⁻ T cells that are present before ART and amplified afterward. It is unclear if these cause immunopathology or reflect a high pathogen load.

Antiretroviral therapy-induced dominant interleukin-2 HIV-1 Gag CD4+ T cell response: evidence of functional recovery of HIV-1-specific CD4+ T cells

Prolonged antiretroviral treatment (ART) significantly changes the cytokine secretion capacities of HIV-1-specific T cells. However, it is unclear whether these changes result from decreased viremia or they correspond to true functional recovery of viral-specific immune response. To study this issue, we analysed the quantitative and qualitative differences of HIV-1-specific and polyclonal CD4+ and CD8+ T cells between 26 naive and 52 treated individuals. HIV-1 Gag and staphylococcal enterotoxin B (SEB)-reactive T cells were determined by flowcytometric intracellular secretion of IFN-γ or/and ΙL-2. ART resulted in increase of single IL-2 and decrease of single IFN-γ-secreting HIV-1 CD4+ T cells, while both cytokines secreting HIV-1 CD4+ T cells were presented in comparable frequencies in both groups. Viral loads correlated negatively with single IL-2 and positively with single IFN-γ-secreting HIV-1 CD4+ cells. Single IL-2 HIV-1 CD4+ T cells correlated positively with both cytokines secreting polyclonal CD8+ T cells. By qualitative analysis, a dominant IL-2 HIV-1 CD4+ T cell response (> 70% single IL-2) was identified only in ART suppressed patients, who also generated increased dual specific polyclonal CD8+ T cells. Polyfunctional HIV-1 CD4+ T cell responses were detected even in naive individuals with high viremia. In conclusion, the presence of dominant IL-2 HIV-1 CD4+ T cell response, associated with increased CD8+ T cells capable to produce IL-2, indicates that the recovery of HIV-1-specific CD4+ T cell functionality under ART is a feasible goal. Furthermore, polyfunctional HIV-1 CD4+ T cell responses seem not to be directly involved in viral replication control.

Multiple T-cell responses to human immunodeficiency virus type 1 are enhanced by dendritic cells

Human immunodeficiency virus type 1 (HIV-1)-specific T-cell reactivity has been related to protection from disease progression. Optimal T-cell reactivity to HIV-1 presumably requires antigen processing and presentation by professional antigen-presenting cells, particularly dendritic cells (DC). Here we examined whether multiple HIV-1-specific T-cell functions are enhanced by stimulation with HIV-1 peptide-loaded DC derived from HIV-1-infected subjects on antiretroviral therapy. We first found that mature DC increased the number of gamma interferon (IFN-gamma)-producing T cells detected by enzyme-linked immunospot assay to overlapping 15-mer peptides of HIV-1 Gag and Nef, compared to stimulation with peptide-loaded, immature DC or to peptides without DC. IFN-gamma production was lower in response to large pools of the Gag and Nef peptides, regardless of presentation by DC. We further observed that HIV-1 peptide-loaded, mature DC stimulated greater CD8(+) and CD4(+) T-cell proliferation than did the peptides without DC and that T-cell proliferation was lower in response to larger pools of the peptides. The lower T-cell IFN-gamma and proliferation responses to the larger peptide pools were related to lower T-cell viability. Finally, the number of polyfunctional CD8(+) and CD4(+) T cells stimulated by HIV-1 peptide-loaded, mature DC, defined as positive by intracellular staining for more than one immune mediator (IFN-gamma, interleukin 2, tumor necrosis factor alpha, macrophage inhibitory protein 1beta, or CD107a), was greater than that stimulated by the peptides alone. These results indicate that DC can enhance multiple types of HIV-1-specific T-cell functions.

Safety and immunogenicity of recombinant poxvirus HIV-1 vaccines in young adults on highly active antiretroviral therapy

A trial to evaluate the safety and immunogenicity of recombinant modified vaccinia Ankara (MVA) and fowlpox (FP) vectors expressing multiple HIV-1 proteins was conducted in twenty HIV-1 infected youth with suppressed viral replication on HAART. The MVA and FP-based multigene HIV-1 vaccines were safe and well tolerated. Increased frequencies of HIV-1 specific CD4+ proliferative responses and cytokine secreting cells were detected following immunization. Increased frequencies and breadth of HIV-1 specific CD8 T-cell responses were also detected. Plasma HIV-1-specific antibody levels and neutralizing activity were unchanged following vaccination. Poxvirus-based vaccines may merit further study in therapeutic vaccine protocols.

Chimpanzee CD4+ T cells are relatively insensitive to HIV-1 envelope-mediated inhibition of CD154 up-regulation

CD40-CD154 interaction forms a key event in regulation of crosstalk between dendritic cells and CD4 T cells. In human immunodeficiency virus (HIV)-1 infected patients CD154 expression is impaired, and the resulting loss of immune responsiveness by CD4+ T cells contributes to a progressive state of immunodeficiency in humans. Although chimpanzees are susceptible to chronic HIV-1/SIVcpz infection, they are relatively resistant to the onset of AIDS. This relative resistance is characterized by maintenance of CD4+ T cell populations and function, which is highly compromised in human patients. In our cohort of chronically HIV-1- and SIVcpz-infected chimpanzees, we demonstrated the capacity to produce IL-2, following CD3/CD28 stimulation, as well as preserved CD154 up-regulation. Cross-linking of CD4 with mAb was found to inhibit CD3/CD28-induced up-regulation of CD154 equally in chimpanzees and humans. However, specific cross-linking with trimeric recombinant HIV-1 gp140 revealed reduced sensitivity for inhibition of CD154 up-regulation in chimpanzees, requiring fourfold higher concentrations of viral protein. Chimpanzee CD4+ T cells are thus less sensitive to the immune-suppressive effect of low-dose HIV-1 envelope protein than human CD4+ T cells.

Immunogenicity in macaques of the clinical product for a clade B DNA/MVA HIV vaccine: elicitation of IFN-gamma, IL-2, and TNF-alpha coproducing CD4 and CD8 T cells

The clinical product for a clade B HIV DNA/MVA vaccine expressing Gag, Pol, and Env has been tested for immunogenicity in macaques. Responding T cells were at the threshold for detection following DNA priming at weeks 0 and 8 but underwent sharp expansions and contractions following MVA boosting at weeks 16 and 24. Both CD4 and CD8 T cell responses had high frequencies of cytokine coproducing cells with >50% of the memory cells coproducing multiple cytokines including IL-2. The highest responses were elicited to Gag, followed by Env and then Pol. In two of six macaques, the vaccine also elicited low levels of neutralizing Ab for easy to neutralize clade B isolates.

Human immunodeficiency virus type 1 controllers but not noncontrollers maintain CD4 T cells coexpressing three cytokines

Here, we evaluate the cytokine coexpression profiles of human immunodeficiency virus (HIV)-specific CD4 T cells for the expression of the cytokines gamma interferon (IFN-gamma), interleukin-2, and tumor necrosis factor alpha. In controllers, CD4 T cells producing three or two cytokines (triple producers and double producers, respectively) represented >50% of the total response. In contrast, in noncontrollers approximately 75% of responding cells produced only one cytokine (single producers), mostly IFN-gamma. Cells producing three cytokines were functionally superior to those producing single cytokines and showed an inverse correlation (P < 0.001) with viral load. These results demonstrate a strong association between the maintenance of highly functional CD4 T cells producing three cytokines and control of HIV-1.

Design and characterization of an HIV-1 Tat mutant: Inactivation of viral and cellular functions but not antigenicity

Among HIV-1 proteins, Tat is a promising antigen for consideration as a component of anti-HIV-1 vaccine formulations. Nevertheless, this viral protein is able to affect the expression of several cellular genes that are implicated in immune response. In this study, we designed and characterized a mutant form of Tat ("STLA Tat"), which is unable to transactivate viral transcription, and which has lost the deleterious effects on the expression of MHC I, IL-2, and CD25 genes compared with wild-type Tat, as observed in lymphoid Jurkat cells that stably express the tat genes. In vivo experiments in mice revealed that STLA Tat induces anti-Tat antibodies at the same titers as wild-type Tat, which recognize both autologous and heterologous Tat antigens. Finally, STLA Tat did not induce the immunosuppression observed after injection of wild-type Tat. Therefore, this STLA Tat mutant appears to be a safe and promising antigen for further evaluation in anti-HIV-1 vaccine strategies.