HIV-specific CTL Research Articles

Simulation and forecasting CTLs response effectualness against global dynamics of SARS-CoV-2/HIV coinfection

Quantifying the dynamical traits and harshness of SARS-CoV-2/HIV coinfection, a modified deterministic seven compartmental mathematical model is framed at cellular level encapsulating the interrelationships between epithelial cells (predominant target cells of COVID-19 infection), CD4+ T cells (target cells of HIV/AIDS infection), SARS-CoV-2 virions, HIV virions and HIV-specific CTL response. As a way to comprehend the kinetics of SARS-CoV-2/HIV coinfection and to provide prediction of model outcomes, the positivity, boundedness and existence conditions of the biologically feasible equilibrium points have been studied. The criteria of local stability and global stability of the coinfection system around the non-negative equilibrium points have been investigated and the analytical results are enhanced numerically. To measure the influence of the model parameters in SARS-CoV-2/HIV transmission dynamics, sensitivity analysis has been performed. Semi-relative sensitivity analysis demonstrates the maximum deviation of the concentration of infected epithelial cells due to changes in the model parameters and states that six parameters are most sensitive. The numerical simulation stipulates that the COVID-19 infection is likely to be died out from a HIV patient body by increasing the apoptosis of infected epithelial cells and that is possible through the proliferation of the CD4+ T cells count of an individual living with HIV via antiretroviral therapy (ART). Additionally, elevated concentration of CD4+ T cells in people living with HIV assists in heightening the CTLs response to combat COVID-19 and other opportunistic infections.

OP 4.6 – 00185 No associations between magnitudes of HIV-specific CTL responses on stable art and subsequent decay of intact proviruses or cell-associated HIV mRNA

OP 4.6 – 00185 No associations between magnitudes of HIV-specific CTL responses on stable art and subsequent decay of intact proviruses or cell-associated HIV mRNA

Selective miRNA inhibition in CD8+ cytotoxic T lymphocytes enhances HIV-1 specific cytotoxic responses.

miRNAs dictate relevant virus-host interactions, offering new avenues for interventions to achieve an HIV remission. We aimed to enhance HIV-specific cytotoxic responses—a hallmark of natural HIV control— by miRNA modulation in T cells. We recruited 12 participants six elite controllers and six patients with chronic HIV infection on long-term antiretroviral therapy ("progressors"). Elite controllers exhibited stronger HIV-specific cytotoxic responses than the progressors, and their CD8+T cells showed a miRNA (hsa-miR-10a-5p) significantly downregulated. When we transfected ex vivo CD8+ T cells from progressors with a synthetic miR-10a-5p inhibitor, miR-10a-5p levels decreased in 4 out of 6 progressors, correlating with an increase in HIV-specific cytotoxic responses. The effects of miR-10a-5p inhibition on HIV-specific CTL responses were modest, short-lived, and occurred before day seven after modulation. IL-4 and TNF-α levels strongly correlated with HIV-specific cytotoxic capacity. Thus, inhibition of miR-10a-5p enhanced HIV-specific CD8+ T cell capacity in progressors. Our pilot study proves the concept that miRNA modulation is a feasible strategy to combat HIV persistence by enhancing specific cytotoxic immune responses, which will inform new approaches for achieving an antiretroviral therapy-free HIV remission.

PP 3.5 - HIV-infected cells that survive co-culture with HIV-specific CTL exhibit distinctive viral messenger RNA transcript profiles

PP 3.5 - HIV-infected cells that survive co-culture with HIV-specific CTL exhibit distinctive viral messenger RNA transcript profiles

BCL-2 Antagonism Sensitizes CTL-Resistant HIV Reservoirs to Elimination Ex Vivo

Curing HIV infection will require the elimination of a reservoir of infected CD4+ T-cells that persists despite HIV-specific CTL responses. While viral latency is a critical factor in this persistence, recent evidence also suggests a role for intrinsic resistance of reservoir-harboring cells to CTL killing. We explored the hypothesis that this resistance is mediated by BCL-2 family proteins, which can antagonize CTL-induced apoptosis. We show that the reactivatable HIV reservoir is disproportionately present in BCL-2hi CD4+ T-cells, which are relatively resistant to CTL. BCL-2/BCL-XL antagonists were sufficient for inducing the elimination of HIV-infected cells from a primary-cell model of latency, but did not drive reductions in ex vivo viral reservoirs when tested either alone or with a latency reversing agent (LRA). The triple combination of LRAs, HIV-specific T-cells, and a BCL-2 antagonist uniquely enabled depletions in ex vivo viral reservoirs, providing rationale for novel therapeutic approaches targeting HIV cure.

OR21 HLA-C downregulation by HIV adapts to host HLA genotype

Aim It was recently found that HIV can downregulate HLA-C on infected cells. This is mediated by the viral protein Vpu, and is in addition to the downregulation of HLA-A/B by Nef. The magnitude of HLA-C downregulation varies widely between primary HIV viruses, but the selection pressures resulting in either HLA-C downregulation or preservation are not clear. Methods To better understand viral immune evasion targeting HLA-C, we have characterized HLA-C downregulation by a range of primary HIV-1 viruses. Results 100 replication competent viral isolates, from limiting dilution outgrowth assays of 20 individuals with effective anti-retroviral therapy, show a substantial minority of individuals harbor reservoir virus which strongly downregulates HLA-C. 20 longitudinal samples from 4 untreated individuals demonstrate no changes in HLA-C downregulation during acute infection, but show variation between viral quasispecies that can persist in chronic infection. 200 Vpu molecules cloned from plasma of treatment naive individuals in chronic infection, show that downregulation of HLA-C adapts to host HLA genotype. HLA-C alleles differ in the pressure they exert for viral downregulation of HLA-C, and individuals with higher levels of HLA-C expression favour greater viral downregulation of HLA-C. Studies of primary and mutant molecules show the transmembrane regions of both Vpu and HLA are responsible for their interaction when removing HLA-C from the cell surface. Conclusions Finding that reservoir virus can downregulate HLA-C could have implications for HIV cure therapy approaches in some individuals. The adaptation of HLA-C downregulation to host HLA genotype which is observed, indicates a subset of HLA-C alleles restrict HIV-specific CTL responses which are subverted by viral downregulation of HLA-C. Differential viral modulation of HLA-C, compared to HLA-A/B, can be used to understand differences in the biological roles of these HLA molecules in HIV infection.

PP5.7 - Functional profiling of HIV-specific CTL clonotypes and their ability to reduce HIV reservoir

PP5.7 - Functional profiling of HIV-specific CTL clonotypes and their ability to reduce HIV reservoir

Compartmentalization of simian immunodeficiency virus replication within secondary lymphoid tissues of rhesus macaques is linked to disease stage and inversely related to localization of virus-specific CTL.

We previously demonstrated that HIV replication is concentrated in lymph node B cell follicles during chronic infection and that HIV-specific CTL fail to accumulate in large numbers at those sites. It is unknown whether these observations can be generalized to other secondary lymphoid tissues or whether virus compartmentalization occurs in the absence of CTL. We evaluated these questions in SIVmac239-infected rhesus macaques by quantifying SIV RNA(+) cells and SIV-specific CTL in situ in spleen, lymph nodes, and intestinal tissues obtained at several stages of infection. During chronic asymptomatic infection prior to simian AIDS, SIV-producing cells were more concentrated in follicular (F) compared with extrafollicular (EF) regions of secondary lymphoid tissues. At day 14 of infection, when CTL have minimal impact on virus replication, there was no compartmentalization of SIV-producing cells. Virus compartmentalization was diminished in animals with simian AIDS, which often have low-frequency CTL responses. SIV-specific CTL were consistently more concentrated within EF regions of lymph node and spleen in chronically infected animals regardless of epitope specificity. Frequencies of SIV-specific CTL within F and EF compartments predicted SIV RNA(+) cells within these compartments in a mixed model. Few SIV-specific CTL expressed the F homing molecule CXCR5 in the absence of the EF retention molecule CCR7, possibly accounting for the paucity of F CTL. These findings bolster the hypothesis that B cell follicles are immune privileged sites and suggest that strategies to augment CTL in B cell follicles could lead to improved viral control and possibly a functional cure for HIV infection.

Do HIV-specific CTL continue to have an antiviral function during antiretroviral therapy? If not, why not, and what can be done about it?

Pharmacological reactivation of human immunodeficiency virus (HIV) expression from latent proviruses coupled with fully suppressive antiretroviral therapy (ART) has been suggested as a strategy to eradicate HIV infection. In order for this strategy to be effective, latently infected cells must be killed either by the cytopathic effect of reactivated HIV gene expression, or by HIV-specific cytotoxic T lymphocyte (CTL). However, a review of current data reveals little evidence that CTL retain an antiviral effector capacity in patients on fully suppressive ART, implying that the HIV-specific CTL present in these patients will not be able to eliminate HIV-infected CD4+ T cells effectively. If this is due to functional impairment or a quantitative deficit of HIV-specific CTL during ART, then therapeutic vaccination may improve the prospects for eradicating latent reservoirs. However, data from the macaque simian immunodeficiency virus (SIV) model indicate that in vivo, SIV-specific CTL are only effective during the early stages of the viral replication cycle, and this constitutes an alternative explanation why HIV-specific CTL do not appear to have an impact on HIV reservoirs during ART. In that case, immunotoxins that target HIV-expressing cells may be a more promising approach for HIV eradication.

Driving HIV-specific vaccine responses in immune suppressed recipients (113.20)

Abstract Malaria, TB and HIV-1 remain tremendous disease burdens in much of the world’s population. Vaccines for these diseases are desperately needed. However, vaccine efficacy is likely to be compromised due to the systemic Th2 biasing and immune suppression caused by infection with parasitic helminthes. Our lab and others have shown that helminth infection suppresses Th1-type vaccine-specific responses. Although Sub-Saharan populations will benefit most from these vaccines, a large percentage of these populations live in helminth endemic regions. A goal of our research is to find vaccine vectors that drive significant HIV-specific immune responses in helminth infected recipients, despite the immune status of the individual. In the current study, we demonstrate that administration of an HIV vaccine (Listeria expressing HIV-1 gag protein) drives significant HIV-specific CTL and Th1 responses in mice chronically infected with the helminth parasite Schistosoma mansoni. These results suggest that Listeria vector vaccines likely will drive HIV-specific responses in helminth-infected human populations. Kinetic studies show that the HIV-vaccine-specific responses generated in schistosome infected mice are durable and capable of inducing CD4+ and CD8+ T cell memory. Further, Listeria vectors should be considered in the development of new generation HIV-1, malaria or TB vaccines to be administered to populations in sub-Saharan Africa where helminth infection is endemic.

Newborn mice vaccination with BCG.HIVA²²² + MVA.HIVA enhances HIV-1-specific immune responses: influence of age and immunization routes.

We have evaluated the influence of age and immunization routes for induction of HIV-1- and M. tuberculosis-specific immune responses after neonatal (7 days old) and adult (7 weeks old) BALB/c mice immunization with BCG.HIVA222 prime and MVA.HIVA boost. The specific HIV-1 cellular immune responses were analyzed in spleen cells. The body weight of the newborn mice was weekly recorded. The frequencies of HIV-specific CD8+ T cells producing IFN-γ were higher in adult mice vaccinated intradermally and lower in adult and newborn mice vaccinated subcutaneously. In all cases the IFN-γ production was significantly higher when mice were primed with BCG.HIVA222 compared with BCGwt. When the HIV-specific CTL activity was assessed, the frequencies of specific killing were higher in newborn mice than in adults. The prime-boost vaccination regimen which includes BCG.HIVA222 and MVA.HIVA was safe when inoculated to newborn mice. The administration of BCG.HIVA222 to newborn mice is safe and immunogenic and increased the HIV-specific responses induced by MVA.HIVA vaccine. It might be a good model for infant HIV and Tuberculosis bivalent vaccine.

Enhanced induction of HIV-specific CTL by dendritic cell-targeted delivery of SOCS-1 siRNA

Background Dendritic cells (DC) are potent antigen-presenting cells that play a critical role in the activation of T cells. Antigen-loaded dendritic cell-based vaccines have been used for immunotherapy of human cancers and chronic infections, but only with limited success. RNAi-mediated silencing of negative immunoregulatory molecules expressed by DCs may provide a strategy to enhance the potency of DC-based vaccines and immunotherapy.

Discordant immunodominant patterns of HIV-specific CD8 T cells defined by cytokine production or proliferative capacity in HIV elite controllers (39.4)

Abstract Several studies suggest that CTL proliferation is one of the functions specifically associated with elite control of HIV, but IFN-γ is generally used to define HIV epitope-specific CTL immunodominance. We performed multi-dimensional intra-donor analysis of HIV CTL-specific cytokine production and proliferation against panels of HLA-matched optimal epitopes. 9 elite controllers (EC) and 8 subjects with progressive infection (CP) were studied. Our analysis revealed two main immunodominance patterns defined by either predominant IFN-γ production or proliferative capacity with very different hierarchies of responses. In the EC, 40% of epitope-specific CTL that produced IFN-γ after 6 h stimulation did not proliferate whereas 47% of CTL with strong proliferative capacity did not produce IFN-γ after 6h stimulation. The contrasting patterns of immunodominance were associated with different phenotypes of memory and exhaustion markers. HIV CP usually had little HIV-specific proliferative capacity as compared to EC (21% vs 7% of tested epitopes, p=0.009). Our data indicate that immunodominance patterns of HIV-specific CD8 T cell responses differ markedly based on an IFN-γ read out assay compared to functional proliferation. The intra-individual heterogeneity of HIV-specific CTL responses shows that not all epitope specific responses are functionally similar. Assessing CTL functions at the single epitope level can facilitate identification of features critical for antiviral function.

Characterization of an HLA‐C‐restricted CTL response in chronic HIV infection

HIV-specific CTL play an important role in the host control of HIV infection. HIV-nef may facilitate escape of HIV-infected cells from CTL recognition by selectively downregulating the expression of HLA-A and HLA-B molecules, while surface expression of HLA-C is unaffected. The HLA-C-restricted CTL responses have previously been largely ignored and poorly characterized. We examined the frequency, function, and phenotype of HLA-C-restricted CTL in ten antiretroviral therapy-naïve Caucasian and African individuals with chronic HIV-1 infection (for at least 8 years; CD4 cell counts in the range of 50-350) who carried the HLA-Cw04 allele. HLA-Cw04-restricted CTL that recognize a conserved epitope within HIV-1 envelope (aa 375-383 SF9) were analyzed using IFN-gamma ELISPOT assays and phenotypic analysis was carried out by flow cytometry. HLA-C-restricted CTL play an important role in the HIV-specific response, and can account for as much as 54% of the total response. HLA-C-restricted CTL are functionally and phenotypically identical to HLA-A- and HLA-B-restricted CTL. HLA-C-restricted CTL in chronic HIV infection are memory cells of an intermediate phenotype, characterized by high CD27 and low CD28 expression and lack of perforin production.

Dynamics and Consequences of IL-21 Production in HIV-Infected Individuals: A Longitudinal and Cross-Sectional Study

IL-21 is a relatively newly discovered immune-enhancing cytokine that plays an essential role in controlling chronic viral infections. It is produced mainly by CD4(+) T cells, which are also the main targets of HIV-1 and are often depleted in HIV-infected individuals. Therefore, we sought to determine the dynamics of IL-21 production and its potential consequences for the survival of CD4(+) T cells and frequencies of HIV-specific CTL. For this purpose, we conducted a series of cross-sectional and longitudinal studies on different groups of HIV-infected patients and show in this study that the cytokine production is compromised early in the course of the infection. The serum cytokine concentrations correlate with CD4(+) T cell counts in the infected persons. Among different groups of HIV-infected individuals, only elite controllers maintain normal production of the cytokine. Highly active antiretroviral therapy only partially restores the production of this cytokine. Interestingly, HIV infection of human CD4(+) T cells inhibits cytokine production by decreasing the expression of c-Maf in virus-infected cells, not in uninfected bystander cells. We also show that the frequencies of IL-21-producing HIV-specific, but not human CMV-specific, Ag-experienced CD4(+) T cells are decreased in HIV-infected viremic patients. Furthermore, we demonstrate in this study that recombinant human IL-21 prevents enhanced spontaneous ex vivo death of CD4(+) T cells from HIV-infected patients. Together, our results suggest that serum IL-21 concentrations may serve as a useful biomarker for monitoring HIV disease progression and the cytokine may be considered for immunotherapy in HIV-infected patients.

P16-25. HIV specific CTL from elite controllers have a unique survival advantage

P16-25. HIV specific CTL from elite controllers have a unique survival advantage

P09-18. Cw*0303/0304 HIV specific CTL response toward GagYL9 select for HIV escape variants with low fitness that is compensated by intra-codon variation

P09-18. Cw*0303/0304 HIV specific CTL response toward GagYL9 select for HIV escape variants with low fitness that is compensated by intra-codon variation

P19-56 LB. Priming with SOCS-1 silenced Dendritic cells induces robust HIV-specific CTL response in a novel HLA-A2 transgenic humanized mouse model

Results Targeted silencing of SOCS-1 in human DCs a) enhanced their cytokine responses to LPS and stimulated a strong mixed lymphocyte reaction in vitro, b) elicited a strong primary in vitro response to HLA-A2-restricted Melan-A/ MART-1 and HIV Gag SL9 epitope in naive CD8+ T cells from healthy donors and c) increased the HIV gag-specific cytokine response in CD8 T cells from seropositive subjects. More importantly, in HLA-A2 transgenic NOD/ SCID-iL2rγ-/mice reconstituted with CD34 HSC from HLA-A2 donors, injection of SOCS-1 silenced DCs pulsed with HIV A2-restricted gag peptides, but not the irrelevant flu peptide, gave rise to a robust HIV specific CD8 T cell response which protected effectively against lethal challenge with recombinant HIV Gag-vaccinia.

Impact of Intrinsic Cooperative Thermodynamics of Peptide-MHC Complexes on Antiviral Activity of HIV-Specific CTL

The antiviral activity of HIV-specific CTL is not equally potent but rather is dependent on their specificity. But what characteristic of targeted peptides influences CTL antiviral activity remains elusive. We addressed this issue based on HLA-B35-restricted CTLs specific for two overlapping immunodominant Nef epitopes, VY8 (VPLRPMTY) and RY11 (RPQVPLRPMTY). VY8-specific CTLs were more potently cytotoxic toward HIV-infected primary CD4(+) cells than RY11-specific CTLs. Reconstruction of their TCR revealed no substantial difference in their functional avidity toward cognate Ags. Instead, the decay analysis of the peptide-MHC complex (pMHC) revealed that the VY8/HLA-B35 complex could maintain its capacity to sensitize T cells much longer than its RY11 counterpart. Corroboratively, the introduction of a mutation in the epitopes that substantially delayed pMHC decay rendered Nef-expressing target cells more susceptible to CTL killing. Moreover, by using differential scanning calorimetry and circular dichroism analyses, we found that the susceptible pMHC ligands for CTL killing showed interdependent and cooperative, rather than separate or sequential, transitions within their heterotrimer components under the thermally induced unfolding process. Collectively, our results highlight the significant effects of intrinsic peptide factors that support cooperative thermodynamics within pMHC on the efficient CTL killing of HIV-infected cells, thus providing us better insight into vaccine design.

HIV infection in India: Epidemiology, molecular epidemiology and pathogenesis

The year 1986 saw first case of HIV infection as well as first report of AIDS case in India. Since then the epidemic has spread throughout the country.In the recent years there is evidence of epidemic being stabilized with decrease in new infections reported from some parts of the country. The absolute number of HIV infections in the country is expected to be close to 2.5 million and National AIDS Control Programme, phase III is geared to contain the epidemic. HIV viruses circulating in India predominantly belong to HIV-1 subtype C. However, there have been occasional reports of HIV-1 subtype A and B. Matter of concern is reports of A/C and B/C mosaic viruses that are being reported from different parts of the country. The data on HIV drug resistance from India is rather limited. Most of the studies have shown that the virus strains from drug naive patients do not show significant level of drug resistance mutations. The few immunological studies in Indian patients show that the Indian HIV infected patients show both HIV-specific CTL responses as well as neutralizing antibody response. Mapping of CTL epitopes showed that while Indian patients identify same regions of Gag antigen as recognized by South African subtype C infected patients, some regions are uniquely recognized by Indian patients. There are very few studies on host genetic factors in India in context with HIV infection.However there are evidences reported of association of host genetic factors such as HLA types and haplotypes and HIV disease.