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Mutations in a dominant Nef epitope of simian immunodeficiency virus diminish TCR:epitope peptide affinity but not epitope peptide:MHC class I binding.

ABSTRACT: Viruses like HIV and SIV escape from containment by CD8(+) T lymphocytes through generating mutations that interfere with epitope peptide:MHC class I binding. However, mutations in some viral epitopes are selected for that have no impact on this binding. We explored the mechanism underlying the evolution of such epitopes by studying CD8(+) T lymphocyte recognition of a dominant Nef epitope of SIVmac251 in infected Mamu-A*02(+) rhesus monkeys. Clonal analysis of the p199RY-specific CD8(+) T lymphocyte repertoire in these monkeys indicated that identical T cell clones were capable of recognizing wild-type (WT) and mutant epitope sequences. However, we found that the functional avidity of these CD8(+) T lymphocytes for the mutant peptide:Mamu-A*02 complex was diminished. Using surface plasmon resonance to measure the binding affinity of the p199RY-specific TCR repertoire for WT and mutant p199RY peptide:Mamu-A*02 monomeric complexes, we found that the mutant p199RY peptide:Mamu-A*02 complexes had a lower affinity for TCRs purified from CD8(+) T lymphocytes than did the WT p199RY peptide:Mamu-A*02 complexes. These studies demonstrated that differences in TCR affinity for peptide:MHC class I ligands can alter functional p199RY-specific CD8(+) T lymphocyte responses to mutated epitopes, decreasing the capacity of these cells to contain SIVmac251 replication.

SUBMITTER: Cale EM

PROVIDER: S-EPMC3175636 | biostudies-other | 2011 Sep

REPOSITORIES: biostudies-other

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Mutations in a dominant Nef epitope of simian immunodeficiency virus diminish TCR:epitope peptide affinity but not epitope peptide:MHC class I binding.

Cale Evan M EM Bazick Heidi S HS Rianprakaisang Tony A TA Alam S Munir SM Letvin Norman L NL

Journal of immunology (Baltimore, Md. : 1950) 20110812 6

Viruses like HIV and SIV escape from containment by CD8(+) T lymphocytes through generating mutations that interfere with epitope peptide:MHC class I binding. However, mutations in some viral epitopes are selected for that have no impact on this binding. We explored the mechanism underlying the evolution of such epitopes by studying CD8(+) T lymphocyte recognition of a dominant Nef epitope of SIVmac251 in infected Mamu-A*02(+) rhesus monkeys. Clonal analysis of the p199RY-specific CD8(+) T lymph ...[more]

PMID: 21841125

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Project description:CD8+ T cells that bind different regions of proteins derived from a virus are often present at different frequencies. It is thought that those virus-specific CD8+ T cells that are present at the highest frequency are predominantly responsible for control of viral infections. While the number of virus-specific CD8+ T cells is undoubtedly important, the functionality of these cells may also play a role in their anti-viral capacity. It was not known if virus-specific CD8+ T cells present at high frequencies are more functionally effective against viral infection than those present at low frequencies. In this study, we characterized the functional differences between the SIV-specific cells present at high frequencies to those present at low frequencies in the blood of rhesus monkeys infected with simian immunodeficiency virus (SIV). We found that the high-and low-frequency SIV-specific cells had different functional capacities both during acute and chronic SIV infection. We also found that the strength with which a cell interacts with the proteins derived from the virus may contribute to the functional differences between the high- and low-frequency cells. These findings further our understanding of anti-viral responses and may inform HIV vaccine design. Peripheral blood was collected on days 14, 21, 28, 35, 42, 56, 70, and and 210 after inoculation with SIVmac251. Plasma viral RNA from these samples was measured using an ultra-sensitive branched DNA amplification assay (Siemens Diagnostics, Berkeley, CA). PBMC were stained with p11C and p54AS tetramers and CD3 and CD8 antibodies at 4°C. Tetramer-positive single CD3+CD8+ lymphocytes were sorted to greather than 95% purity into RNAprotect (Qiagen) at 4°C. RNA was isolated using a Trizol (Invitrogen) extraction protocol. Briefly, 0.8 ml of Trizol were added to the cell pellet and incubated for 5 minutes at room temperature and 0.16 ml of chloroform were added, shaken vigorously by hand for 15 seconds, incubated at room temperature for 2-3 minutes and centrifuged at 13,000 rpm for 15 minutes at 4ºC. The colorless upper aqueous phase was carefully collected and transferred to a new tube containing 2 ?l of linear acrylamide for mixing. An equal volume of isopropyl alcohol was then added and mixed. The mixture was incubated at room temperature for 10 minutes and centrifuged at 13,000 rpm for 10 minutes at 4ºC. The supernatant was collected and the RNA was washed with 1 ml of 70% ethanol and centrifuged at 10,500 rpm for 5 minutes at 4ºC. The supernatant was completely removed and the RNA pellet was allowed to air-dry. The RNA was then resuspended in RNase-free water and stored at -80ºC. RNA integrity was tested using an Agilent Bioanalyzer. RNA was then amplified using the TargetAmp 2-Round Biotin-aRNA Amplification Kit 3.0 (Epicentre Biotechnologies) according the manufacturer’s instructions. Amplified biotinylated antisense-RNA (aRNA) was resuspended in RNase-free water and stored at -80ºC. Nanodrop ND-1000 was used to determine the biotinylatedaRNA concentration and an Agilent Bioanalyzer was used to determine its integrity.Amplified aRNA was hybridized to Illumina Human HT-12 Expression BeadChips according to the manufacturer instructions and was stained with Streptavidin Cy3 for detection (Illumina, San Diego, CA, USA).

Project description:The nef gene of the human and simian immunodeficiency viruses (HIV and SIV) is dispensable for viral replication in T-cell lines; however, it is essential for high virus loads and progression to simian AIDS (SAIDS) in SIV-infected adult rhesus macaques. Nef proteins from HIV type 1 (HIV-1), HIV-2, and SIV contain a proline-Xaa-Xaa-proline (PxxP) motif. The region of Nef with this motif is similar to the Src homology region 3 (SH3) ligand domain found in many cell signaling proteins. In virus-infected lymphoid cells, Nef interacts with a cellular serine/threonine kinase, designated Nef-associated kinase (NAK). In this study, analysis of viral clones containing point mutations in the nef gene of the pathogenic clone SIVmac239 revealed that several strictly conserved residues in the PxxP region were essential for Nef-NAK interaction. The results of this analysis of Nef mutations in in vitro kinase assays indicated that the PxxP region in SIV Nef was strikingly similar to the consensus sequence for SH3 ligand domains possessing the minus orientation. To test the significance of the PxxP motif of Nef for viral pathogenesis, each proline was mutated to an alanine to produce the viral clone SIVmac239-P104A/P107A. This clone, expressing Nef that does not associate with NAK, was inoculated into seven juvenile rhesus macaques. In vitro kinase assays were performed on virus recovered from each animal; the ability of Nef to associate with NAK was restored in five of these animals as early as 8 weeks after infection. Analysis of nef genes from these viruses revealed patterns of genotypic reversion in the mutated PxxP motif. These revertant genotypes, which included a second-site suppressor mutation, restored the ability of Nef to interact with NAK. Additionally, the proportion of revertant viruses increased progressively during the course of infection in these animals, and two of these animals developed fatal SAIDS. Taken together, these results demonstrated that in vivo selection for the ability of SIV Nef to associate with NAK was correlated with the induction of SAIDS. Accordingly, these studies implicate a role for the conserved SH3 ligand domain for Nef function in virally induced immunodeficiency.

Project description:UnlabelledCertain major histocompatibility complex class I (MHC-I) alleles (e.g., HLA-B*27) are enriched among human immunodeficiency virus type 1 (HIV-1)-infected individuals who suppress viremia without treatment (termed "elite controllers" [ECs]). Likewise, Mamu-B*08 expression also predisposes rhesus macaques to control simian immunodeficiency virus (SIV) replication. Given the 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 correlate analysis revealed that CD8(+) T cells targeting Nef RL10 was 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 Nef RL10-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 numbers of ECs were similar in groups 1 and 2. High-frequency vaccine-induced CD8(+) T cells focused on a single conserved epitope and therefore did not prevent infection or increase the incidence of elite control in Mamu-B*08(+) macaques.ImportanceSince 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 into 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 whether 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 multidimensional nature of virologic control of lentivirus infection.

Dataset Information

Mutations in a dominant Nef epitope of simian immunodeficiency virus diminish TCR:epitope peptide affinity but not epitope peptide:MHC class I binding.

Publications

Mutations in a dominant Nef epitope of simian immunodeficiency virus diminish TCR:epitope peptide affinity but not epitope peptide:MHC class I binding.

Similar Datasets

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