Thomas Harrer

Although vigorous activated and memory CTL have been associated with HIV-1 infection, data are lacking regarding the breadth of epitopes recognized in a given individual and the relationship to the viral quasispecies present in vivo. In this study we performed a detailed analysis of the HIV-1-specific CTL response in a seropositive person with documented HIV-1 infection of 15 yr duration, stable CD4 counts above 500 cells/ml, and viral load persistently below 500 molecules of RNA/ml of plasma. Epitope mapping studies revealed the presence of HLA class I-restricted CTL responses to six different epitopes in p17, p24, RT, Env, and Nef, which conferred broadly cross-reactive recognition of reported HIV-1 variants. Sequence analysis of autologous viruses revealed the absence of immune escape variants within five of the six epitopes. Despite consistently low viral RNA levels in plasma and viral DNA levels in PBMC, in vivo-activated circulating CTL were detected against three of the epitopes. Five of the six epitopes, including the three dominant epitopes, have been detected in persons with progressive disease, suggesting that nonprogressors may not target unique epitopes. This study demonstrates that HIV-1-specific CTL can be highly activated and broadly directed in the setting of an extremely low viral load, and that neither high viral load nor antigenic diversity is required for the generation of a multispecific CTL response. Although the detection of strong CTL responses, low viral load, and lack of immune escape are consistent with the hypothesis that CTL may contribute to lack of disease progression in this individual, the contribution of these responses to maintenance of the asymptomatic state remains to be determined.

Human leukocyte antigen (HLA)-B27-positive subjects are uncommon in their ability to control infection with human immunodeficiency virus type 1 (HIV-1). However, late viral escape from a narrowly directed immunodominant Gag-specific CD8(+) T-lymphocyte (CTL) response has been linked to AIDS progression in these individuals. Identifying the mechanism of the immune-mediated control may provide critical insights into HIV-1 vaccine development. Here, we illustrate that the CTL escape mutation R(264)K in the HLA-B27-restricted KK10 epitope in the capsid resulted in a significant defect in viral replication in vitro. The R(264)K variant was impaired in generating late reverse transcription products, indicating that replication was blocked at a postentry step. Notably, the R(264)K mutation was associated in vivo with the development of a rare secondary mutation, S(173)A, which restored viral replication in vitro. Furthermore, infectivity of the R(264)K variant was rescued by the addition of cyclosporine A or infection of a cyclophilin A-deficient cell line. These data demonstrate a severe functional defect imposed by the R(264)K mutation during an early step in viral replication that is likely due to the inability of this variant to replicate efficiently in the presence of normal levels of cyclophilin A. We conclude that the impact of the R(264)K substitution on capsid structure constrains viral escape and enables long-term maintenance of the dominant CTL response against B27-KK10, providing an explanation for the protective effect of HLA-B27 during HIV infection.

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Many practical clinical questions regarding the management of human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) remain unanswered. We sought to identify and develop practical answers to key clinical questions in HAND management. Sixty-six specialists from 30 countries provided input into the program, which was overseen by a steering committee. Fourteen questions were rated as being of greatest clinical importance. Answers were drafted by an expert group based on a comprehensive literature review. Sixty-three experts convened to determine consensus and level of evidence for the answers. Consensus was reached on all answers. For instance, good practice suggests that all HIV patients should be screened for HAND early in disease using standardized tools. Follow-up frequency depends on whether HAND is already present or whether clinical data suggest risk for developing HAND. Worsening neurocognitive impairment may trigger consideration of antiretroviral modification when other causes have been excluded. The Mind Exchange program provides practical guidance in the diagnosis, monitoring, and treatment of HAND.