Selective Induction of CTL Helper Rather Than Killer Activity by Natural Epitope Variants Promotes Dendritic Cell–Mediated HIV-1 Dissemination

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Recall T cell responses to HIV-1 antigens are used as a surrogate for endogenous cellular immune responses generated during infection. Current methods of identifying antigen-specific T cell reactivity in HIV-1 infection use bulk peripheral blood mononuclear cells (PBMC) yet ignore professional antigen-presenting cells (APC) that could reveal otherwise hidden responses. In the present study, peptides representing autologous variants of major histocompatibility complex (MHC) class I-restricted epitopes from HIV-1 Gag and Env were used as antigens in gamma interferon (IFN-␥) enzyme-linked immunosorbent spot (ELISpot) and polyfunctional cytokine assays. Here we show that dendritic cells (DC) enhanced T cell reactivity at all stages of disease progression but specifically restored T cell reactivity after combination antiretroviral therapy (cART) to early infection levels. Type 1 cytokine secretion was also enhanced by DC and was most apparent late post-cART. We additionally show that DC reveal polyfunctional T cell responses after many years of treatment, when potential immunotherapies would be implemented. These data underscore the potential efficacy of DC immunotherapy that aims to awaken a dormant, autologous, HIV-1-specific CD8 ؉ T cell response. IMPORTANCEAssessment of endogenous HIV-1-specific T cell responses is critical for generating immunotherapies for subjects on cART. Current assays ignore the ability of dendritic cells to reveal these responses and may therefore underestimate the breadth and magnitude of T cell reactivity. As DC do not prime new responses in these assays, it can be assumed that the observed responses are not detected without appropriate stimulation. This is important because dogma states that HIV-1 mutates to evade host recognition and that CD8 ؉ cytotoxic T lymphocyte (CTL) failure is due to the inability of T cells to recognize the autologous virus. The results presented here indicate that responses to autologous virus are generated during infection but may need additional stimulation to be effective. Detecting the breadth and magnitude of HIV-1-specific T cell reactivity generated in vivo is of the utmost importance for generating effective DC immunotherapies.

Section: Production Of Multiple Cytokines By Cd8mentioning

confidence: 96%

Section: Fig 5 Dc-mediated Increase In Polyfunctional Cd8mentioning

confidence: 99%

Dendritic Cells Restore CD8⁺T Cell Reactivity to Autologous HIV-1

Smith

Mailliard

Larsen

et al. 2014

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“…These authors showed that dendritic cells can restore CD8 T cell reactivity to autologous HIV-1 in subjects on cART at all stages of disease progression and support the use of DC immunotherapy in subjects on cART. Moreover, Smith et al (30) argue that DC immunotherapy that uses an antigen that is similar to but not the exact antigen to which the subject's T cells were originally primed may not induce an effective cytotoxic T lymphocyte response and may actually hinder viral clearance (31). These results could be an explanation for the findings that, despite the fact that HIV-1-specific immune responses have been elicited in all DCbased vaccine clinical trials, a partial virological response has only been observed in the studies using autologous HIV antigens (32).…”

Section: Discussionmentioning

confidence: 99%

HIV-1 Reservoir Dynamics after Vaccination and Antiretroviral Therapy Interruption Are Associated with Dendritic Cell Vaccine-Induced T Cell Responses

Andrés

Plana

Guardo

et al. 2015

HIV-1-specific immune responses induced by a dendritic cell (DC)-based therapeutic vaccine might have some effect on the viral reservoir. Patients on combination antiretroviral therapy (cART) were randomized to receive DCs pulsed with autologous HIV-1 (n ‫؍‬ 24) (DC-HIV-1) or nonpulsed DCs (n ‫؍‬ 12) (DC-control). We measured the levels of total and integrated HIV-1 DNA in CD4 T cells isolated from these patients at 6 time points: before any cART; before the first cART interruption, which was at 56 weeks before the first immunization to isolate virus for pulsing DCs; before and after vaccinations (VAC1 and VAC2); and at weeks 12 and 48 after the second cART interruption. The vaccinations did not influence HIV-1 DNA levels in vaccinated subjects. After the cART interruption at week 12 postvaccination, while total HIV-1 DNA increased significantly in both arms, integrated HIV-1 DNA did not change in vaccinees (mean of 1.8 log 10 to 1.9 copies/10 6 CD4 T cells, P ‫؍‬ 0.22) and did increase in controls (mean of 1.8 log 10 to 2.1 copies/10 6 CD4 T cells, P ‫؍‬ 0.02) (P ‫؍‬ 0.03 for the difference between groups). However, this lack of increase of integrated HIV-1 DNA observed in the DC-HIV-1 group was transient, and at week 48 after cART interruption, no differences were observed between the groups. The HIV-1-specific T cell responses at the VAC2 time point were inversely correlated with the total and integrated HIV-1 DNA levels after cART interruption in vaccinees (r [Pearson's correlation coefficient] ‫؍‬ ؊0.69, P ‫؍‬ 0.002, and r ‫؍‬ ؊0.82, P < 0. 0001, respectively). No correlations were found in controls. HIV-1-specific T cell immune responses elicited by DC therapeutic vaccines drive changes in HIV-1 DNA after vaccination and cART interruption. (This study has been registered at ClinicalTrials.gov under registration no. NCT00402142.) IMPORTANCEThere is an intense interest in developing strategies to target HIV-1 reservoirs as they create barriers to curing the disease. The development of therapeutic vaccines aimed at enhancing immune-mediated clearance of virus-producing cells is of high priority. Few therapeutic vaccine clinical trials have investigated the role of therapeutic vaccines as a strategy to safely eliminate or control viral reservoirs. We recently reported that a dendritic cell-based therapeutic vaccine was able to significantly decrease the viral set point in vaccinated patients, with a concomitant increase in HIV-1-specific T cell responses. The HIV-1-specific T cell immune responses elicited by this therapeutic dendritic cell vaccine drove changes in the viral reservoir after vaccinations and significantly delayed the replenishment of integrated HIV-1 DNA after cART interruption. These data help in understanding how an immunization could shift the virus-host balance and are instrumental for better design of strategies to reach a functional cure of HIV-1 infection.

“…In some cases, variants were recognized with a lower functional avidity (e.g., N 242 in PIC68008), which may reflect a decrease in cytotoxic potential (64)(65)(66), and consequently, these variants may persist in the viral population due to weakened CTLmediated pressure. Recognition of epitope variants can also result from de novo responses to the same peptides as previously selected to confer escape (30,67).…”

Section: Discussionmentioning

confidence: 99%

Fitness-Balanced Escape Determines Resolution of Dynamic Founder Virus Escape Processes in HIV-1 Infection

Sunshine

Larsen

Maust

et al. 2015

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To understand the interplay between host cytotoxic T-lymphocyte (CTL) responses and the mechanisms by which HIV-1 evades them, we studied viral evolutionary patterns associated with host CTL responses in six linked transmission pairs. HIV-1 sequences corresponding to full-length p17 and p24 gag were generated by 454 pyrosequencing for all pairs near the time of transmission, and seroconverting partners were followed for a median of 847 days postinfection. T-cell responses were screened by gamma interferon/interleukin-2 (IFN-␥/IL-2) FluoroSpot using autologous peptide sets reflecting any Gag variant present in at least 5% of sequence reads in the individual's viral population. While we found little evidence for the occurrence of CTL reversions, CTL escape processes were found to be highly dynamic, with multiple epitope variants emerging simultaneously. We found a correlation between epitope entropy and the number of epitope variants per response (r ‫؍‬ 0.43; P ‫؍‬ 0.05). In cases in which multiple escape mutations developed within a targeted epitope, a variant with no fitness cost became fixed in the viral population. When multiple mutations within an epitope achieved fitness-balanced escape, these escape mutants were each maintained in the viral population. Additional mutations found to confer escape but undetected in viral populations incurred high fitness costs, suggesting that functional constraints limit the available sites tolerable to escape mutations. These results further our understanding of the impact of CTL escape and reversion from the founder virus in HIV infection and contribute to the identification of immunogenic Gag regions most vulnerable to a targeted T-cell attack. IMPORTANCERapid diversification of the viral population is a hallmark of HIV-1 infection, and understanding the selective forces driving the emergence of viral variants can provide critical insight into the interplay between host immune responses and viral evolution. We used deep sequencing to comprehensively follow viral evolution over time in six linked HIV transmission pairs. We then mapped T-cell responses to explore if mutations arose due to adaption to the host and found that escape processes were often highly dynamic, with multiple mutations arising within targeted epitopes. When we explored the impact of these mutations on replicative capacity, we found that dynamic escape processes only resolve with the selection of mutations that conferred escape with no fitness cost to the virus. These results provide further understanding of the complicated viral-host interactions that occur during early HIV-1 infection and may help inform the design of future vaccine immunogens. Exploring the dynamic interplay between human immune responses and the mechanisms by which HIV-1 evades these responses can help inform which types and specificity of immunity a vaccine should elicit. At peak viral load, the viral population is usually homogenous (1-3). In approximately 75% of HIV transmissions, a single variant (the "founder" virus) es...