Abstract
Certain MHC class I (MHC-I) alleles (e.g. HLA-B*27) are enriched among HIV-1-infected individuals who suppress viremia without treatment (termed "elite controllers"; ECs). Likewise, Mamu-B*08 expression also predisposes rhesus macaques to control SIV replication. Given similarities between Mamu-B*08 and HLA-B*27, SIV-infected Mamu-B*08+ animals provide a model to investigate HLA-B*27-mediated elite control. We have recently shown that vaccination with three immunodominant Mamu-B*08-restricted epitopes (Vif RL8, Vif RL9, and Nef RL10) increased the incidence of elite control in Mamu-B*08+ macaques after challenge with the pathogenic SIVmac239 clone. Furthermore, a correlates analysis revealed that CD8+ T-cells targeting Nef RL10 correlated with improved outcome. Interestingly, this epitope is conserved between SIV and HIV-1 and exhibits a delayed and atypical escape pattern. These features led us to postulate that a monotypic vaccine-induced NefRL10-specific CD8+ T-cell response would facilitate the development of elite control in Mamu-B*08+ animals following repeated intrarectal challenges with SIVmac239. To test this, we vaccinated Mamu-B*08+ animals with nef inserts in which Nef RL10 was either left intact (Group 1) or disrupted by mutations (Group 2). Although monkeys in both groups mounted Nef-specific cellular responses, only those in Group 1 developed Nef RL10-specific CD8+ T-cells. These vaccine-induced effector memory CD8+ T-cells did not prevent infection. Escape variants emerged rapidly in the Group 1 vaccinees and, ultimately, the number of ECs was similar in Groups 1 and 2. High frequency vaccine-induced CD8+ T-cells focused on a single conserved epitope, therefore, did not prevent infection or increase the incidence of elite control in Mamu-B*08+ macaques.
IMPORTANCE:
Since elite control of chronic phase viremia is a classic example of an effective immune response against HIV/SIV, elucidating the basis of this phenomenon may provide useful insights as to how to elicit such responses by vaccination. We have previously established that vaccine-induced CD8+ T-cell responses against three immunodominant epitopes can increase the incidence of elite control in SIV-infected Mamu-B*08+ rhesus macaques-a model of HLA-B*27-mediated elite control. Here we investigated if a monotypic vaccine-induced CD8+ T-cell response targeting the conserved, "late-escaping" Nef RL10 epitope can increase the incidence of elite control in Mamu-B*08+ monkeys. Surprisingly, vaccine-induced Nef RL10-specific CD8+ T-cells selected for variants within days after infection and, ultimately, did not facilitate the development of elite control. Elite control is, therefore, likely to involve CD8+ T-cell responses against more than one epitope. Together, these results underscore the complexity and multi-dimensional nature of virologic control of lentivirus infection.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
AbstractCertain MHC class I (MHC-I) alleles (e.g. HLA-B*27) are enriched among HIV-1-infected individuals who suppress viremia without treatment (termed "elite controllers"; ECs). Likewise, Mamu-B*08 expression also predisposes rhesus macaques to control SIV replication. Given similarities between Mamu-B*08 and HLA-B*27, SIV-infected Mamu-B*08+ animals provide a model to investigate HLA-B*27-mediated elite control. We have recently shown that vaccination with three immunodominant Mamu-B*08-restricted epitopes (Vif RL8, Vif RL9, and Nef RL10) increased the incidence of elite control in Mamu-B*08+ macaques after challenge with the pathogenic SIVmac239 clone. Furthermore, a correlates analysis revealed that CD8+ T-cells targeting Nef RL10 correlated with improved outcome. Interestingly, this epitope is conserved between SIV and HIV-1 and exhibits a delayed and atypical escape pattern. These features led us to postulate that a monotypic vaccine-induced NefRL10-specific CD8+ T-cell response would facilitate the development of elite control in Mamu-B*08+ animals following repeated intrarectal challenges with SIVmac239. To test this, we vaccinated Mamu-B*08+ animals with nef inserts in which Nef RL10 was either left intact (Group 1) or disrupted by mutations (Group 2). Although monkeys in both groups mounted Nef-specific cellular responses, only those in Group 1 developed Nef RL10-specific CD8+ T-cells. These vaccine-induced effector memory CD8+ T-cells did not prevent infection. Escape variants emerged rapidly in the Group 1 vaccinees and, ultimately, the number of ECs was similar in Groups 1 and 2. High frequency vaccine-induced CD8+ T-cells focused on a single conserved epitope, therefore, did not prevent infection or increase the incidence of elite control in Mamu-B*08+ macaques.IMPORTANCE:Since elite control of chronic phase viremia is a classic example of an effective immune response against HIV/SIV, elucidating the basis of this phenomenon may provide useful insights as to how to elicit such responses by vaccination. We have previously established that vaccine-induced CD8+ T-cell responses against three immunodominant epitopes can increase the incidence of elite control in SIV-infected Mamu-B*08+ rhesus macaques-a model of HLA-B*27-mediated elite control. Here we investigated if a monotypic vaccine-induced CD8+ T-cell response targeting the conserved, "late-escaping" Nef RL10 epitope can increase the incidence of elite control in Mamu-B*08+ monkeys. Surprisingly, vaccine-induced Nef RL10-specific CD8+ T-cells selected for variants within days after infection and, ultimately, did not facilitate the development of elite control. Elite control is, therefore, likely to involve CD8+ T-cell responses against more than one epitope. Together, these results underscore the complexity and multi-dimensional nature of virologic control of lentivirus infection.Copyright © 2015, American Society for Microbiology. All Rights Reserved.
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