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Articles by Enrique J. Leon
Total Records ( 2 ) for Enrique J. Leon
  John T. Loffredo , Alex T. Bean , Dominic R. Beal , Enrique J. Leon , Gemma E. May , Shari M. Piaskowski , Jessica R. Furlott , Jason Reed , Solomon K. Musani , Eva G. Rakasz , Thomas C. Friedrich , Nancy A. Wilson , David B. Allison and David I. Watkins
  Certain major histocompatibility complex (MHC) class I alleles are strongly associated with control of human immunodeficiency virus and simian immunodeficiency virus (SIV). CD8+ T cells specific for epitopes restricted by these molecules may be particularly effective. Understanding how CD8+ T cells contribute to control of viral replication should yield important insights for vaccine design. We have recently identified an Indian rhesus macaque MHC class I allele, Mamu-B*08, associated with elite control and low plasma viremia after infection with the pathogenic isolate SIVmac239. Here, we infected four Mamu-B*08-positive macaques with SIVmac239 to investigate why some of these macaques control viral replication. Three of the four macaques controlled SIVmac239 replication with plasma virus concentrations below 20,000 viral RNA copies/ml at 20 weeks postinfection; two of four macaques were elite controllers (ECs). Interestingly, two of the four macaques preserved their CD4+ memory T lymphocytes during peak viremia, and all four recovered their CD4+ memory T lymphocytes in the chronic phase of infection. Mamu-B*08-restricted CD8+ T-cell responses dominated the acute phase and accounted for 23.3% to 59.6% of the total SIV-specific immune responses. Additionally, the ECs mounted strong and broad CD8+ T-cell responses against several epitopes in Vif and Nef. Mamu-B*08-specific CD8+ T cells accounted for the majority of mutations in the virus at 18 weeks postinfection. Interestingly, patterns of viral variation in Nef differed between the ECs and the other two macaques. Natural containment of AIDS virus replication in Mamu-B*08-positive macaques may, therefore, be related to a combination of immunodominance and viral escape from CD8+ T-cell responses.
  Nicholas J. Maness , Levi J. Yant , Chungwon Chung , John T. Loffredo , Thomas C. Friedrich , Shari M. Piaskowski , Jessica Furlott , Gemma E. May , Taeko Soma , Enrique J. Leon , Nancy A. Wilson , Helen Piontkivska , Austin L. Hughes , John Sidney , Alessandro Sette and David I. Watkins
  The association between particular major histocompatibility complex class I (MHC-I) alleles and control of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication implies that certain CD8+ T-lymphocyte (CD8-TL) responses are better able than others to control viral replication in vivo. However, possession of favorable alleles does not guarantee improved prognosis or viral control. In rhesus macaques, the MHC-I allele Mamu-B*17 is correlated with reduced viremia and is overrepresented in macaques that control SIVmac239, termed elite controllers (ECs). However, there is so far no mechanistic explanation for this phenomenon. Here we show that the chronic-phase Mamu-B*17-restricted repertoire is focused primarily against just five epitopes—VifHW8, EnvFW9, NefIW9, NefMW9, and envARFcRW9—in both ECs and progressors. Interestingly, Mamu-B*17-restricted CD8-TL do not target epitopes in Gag. CD8-TL escape variation occurred in all targeted Mamu-B*17-restricted epitopes. However, recognition of escape variant peptides was commonly observed in both ECs and progressors. Wild-type sequences in the VifHW8 epitope tended to be conserved in ECs, but there was no evidence that this enhances viral control. In fact, no consistent differences were detected between ECs and progressors in any measured parameter. Our data suggest that the narrowly focused Mamu-B*17-restricted repertoire suppresses virus replication and drives viral evolution. It is, however, insufficient in the majority of individuals that express the "protective" Mamu-B*17 molecule. Most importantly, our data indicate that the important differences between Mamu-B*17-positive ECs and progressors are not readily discernible using standard assays to measure immune responses.
 
 
 
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