CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

of zapped, untreated or control-treated CTL to inhibit viral replication, using CD8+ T cells from an HLA-B*27:05+ controller with the dominant B*27:05-Gag-KK10 response. We observe that untreated bulk and control-treated CD8+ T cells effectively inhibit viral replication, but zapped CTL lacking KK10-specific cells lose this suppressive capacity (Fig 1B).

Figure: (A) Representative FACS plots showing HLA-B*27:05-KK10+ CD8+ T cells in an HIV+ subject (left) and their elimination 48h after KK10-SAP treatment (right). Numbers indicate %liveCD3+CD8+tetramer+ cells. (B) Viral inhibition assay showing loss of the suppressive capacity by KK10-zapped cells. Conclusions: We have optimized a novel method to eliminate CTL of different specificities and thereby measure their individual contribution to viral suppression. This rapid, efficient, cost-saving method, applicable to any HLA type, will enable us to discriminate between the most efficacious and futile CTL responses in HIV infection and answer the long-standing question of the quality of different responses – the holy grail of a therapeutic HIV vaccine research. 363 Linking Pig-Tailed Macaque Major Histocompatibility Complex Class I Haplotypes and Cytotoxic T Lymphocyte Escape Mutations in SIV Infection Shayarana Gooneratne 1 ; Hamid Alinejad-Rokny 2 ; Diako Ebrahimi Mohammadi 2 ; Patrick Bohn 3 ; RogerWiseman 3 ; David O’Connor 3 ; Miles Davenport 2 ; Stephen Kent 1 1 University of Melbourne, Melbourne, Australia; 2 University of New South Wales, Kensington, Australia; 3 University of Wisconsin Madison, Madison, WI, US Background: Cytotoxic T lymphocytes select for virus escape mutants of HIV and SIV and this limits the effectiveness of vaccines and immunotherapies against these viruses. The influence of MHC-I alleles on HIV diversity has been well characterised in humans at the population level. MHC-I alleles likely affect viral diversity in the SIV-infected pig-tailed macaque ( M. nemestrina ) model, but this is poorly characterised. We studied the evolution of SIV in pig-tailed macaques with a range of MHC-I haplotypes. Methods: SIVmac251 genomes were amplified from the plasma of 44 pig-tailed macaques infected with SIVmac251 at 4-10 months after infection and characterized by Illumina deep sequencing. MHC-I typing was performed on cellular RNA using Roche/454 pyrosequencing. MHC-I haplotypes and viral sequence polymorphisms were linked using in-house bioinformatics pipelines, both at individual mutations and groups of mutations spanning 10 amino acid segments, since CTL escape can occur at different amino acids within the same epitope in different animals. Results: The approach successfully identified 6 known CTL escape mutations within 3 Mane-A1*084-restricted epitopes. The approach also identified over 70 new SIV polymorphisms linked to a variety of 32 MHC-I haplotypes. Using functional CD8 T cell assays we confirmed that one of these associations, a Mane-B028 haplotype-linked mutation in Nef, corresponded to a CTL epitope. We also identified mutations associated with the Mane-B017 haplotype that were previously described as CTL epitopes restricted by Mamu- B*017:01 in rhesus macaques. Conclusions: Patterns of immune escape variants are similar in HIV-1 infected human subjects that share the same MHC-I genes, but this has not been studied for SIV infection of macaques. By studying SIV sequence diversity in 44 MHC-typed SIV-infected pig-tailed macaques, we defined over 70 sites within SIV where mutations were common in macaques sharing particular MHC-I genes. Further, pig-tailed macaques sharing near-identical MHC-I genes with rhesus macaques responded to the same CTL epitope and forced immune escape. This allows many reagents developed to study rhesus macaque reagents to also be used to study pig-tailed macaques. Overall, our study defines sites of immune escape in SIV in pig-tailed macaques and this enables a more refined level of analysis of future vaccine design and treatment strategies for HIV. 364 HLA Class-II – Associated HIV Polymorphisms Predict Escape From CD4 T-Cell Responses Nathaniel B. Erdmann 1 ;Victor Du 1 ; Jonathan M. Carlson 2 ; John Sidney 3 ; LingYue 4 ; Susan Allen 4 ; Eric Hunter 4 ; Sonya L. Heath 1 ; Anju Bansal 1 ; Paul A. Goepfert 1 1 University of Alabama at Birmingham, Birmingham, AL, US; 2 Microsoft Research, Los Angeles, CA, US; 3 La Jolla Institute of Allergy and Immunology, La Jolla, CA, US; 4 Emory University, Atlanta, GA, US Background: Human immunodeficiency virus (HIV) can escape antiretroviral therapy, antibody and CD8 + T-cell pressure indicating these factors assist in viral control. The ability of CD4 + T-cells to force escape mutations and influence HIV-1 viral control remains unclear. Methods: We applied a computational approach to identify HIV polymorphisms (adaptations) in gag , pol , and nef disproportionately associated with specific HLA-II alleles in an African cohort of chronically infected individuals. Peptides including the predicted adaptation (AE) or a non-adapted version of the epitope (NAE) were synthesized and evaluated for immunogenicity. We applied a CD8 + -depleted interferon- γ ELISpot assay using PBMC obtained from chronically infected donors that were non-controllers (viral load >10,000 copies/mL), controllers (viral load <2,000 copies/mL) or acutely infected individuals. We determined the immunogenicity of predicted epitopes relative to dominant viral sequence in chronic infection, as well as transmitted founder virus (TFV) in acute HIV infection (AHI). Results: We identified 29 HLA class-II associated HIV adaptations, all of which were demonstrated to represent novel CD4 + T-cell epitopes. Consistent with a prior study, magnitude and breadth of HIV-specific CD4 + T-cell responses seen in controllers was higher as compared to non-controllers. The magnitude of responses to epitopes containing the adapted polymorphism (AE) was lower when compared to NAE (p=0.0009). Even when the dominant viral sequence matched the predicted AE in chronic infection, NAE were more immunogenic (p=0.01). We studied a cohort of individuals with AHI to more clearly delineate the epitope responsible for observed immune responses. We found a relative lack of AE-specific CD4 + T-cell responses (p=0.008) despite the TFV encoding equal numbers of AE and NAE. Longitudinal data from AHI individuals followed for 1-2 years off antiretroviral therapy demonstrated sequence changes at predicted epitopes that were biologically confirmed to represent CD4 + T-cell mediated escape. Conclusions: These data demonstrate the identification of HLA-II associated polymorphisms as a means to identify novel CD4 + epitopes. In addition, our studies in acute and chronic infection definitively characterize HIV escape from CD4 T-cell responses, a phenomenon that is more common than previously anticipated. Our findings emphasize the importance of inducing CD4 + T-cells along with CD8 + T-cells and antibodies as part of a comprehensive HIV vaccine strategy.

Poster Abstracts

274

CROI 2015