Cross-clade evaluation of nef-specific CTLs in HIV-1+individuals reveal breadth underestimation and discrepant patterns of T cell functionality.

GABRIELA TURK; MARÍA MAGDALENA GHERARDI; NATALIA LAUFER; PEDRO CAHN; JOSEPHINE H. COX; HORACIO SALOMÓN

Seattle, Washington, Estados Unidos

Conferencia; AIDS Vaccine 2007; 2007

Background: Due to the high HIV-1 genetic variability among isolates and the diversity of HLA alleles in the human population, screening of HIV-1 specific T cell responses constitutes a major goal in different settings. Here, we aimed to characterize HIV-1 Nef-specific T cell responses in patients infected with clade B or BF URFs and determine the patterns and quality of cross-reactive T cells. Methods: Sixteen HIV-1 patients were enrolled during acute infection. T cell responses were assessed in an Interferon-gamma (IFN-ƒÁ) based ELISPOT assay using overlapping peptides, from B and BF subtypes, arrayed in a matrix system and further confirmed at the single peptide level. The quality of positive responses were analyzed further by flow cytometry, measuring CD8+ T-cell degranulation and production of IFN-ƒÁ, MIP-1ƒÀ, TNF-ƒ¿, and IL-2. Results: Cross-clade T cell responses were found in patients infected with different clades. Responses in F patients were narrower than B patients but higher in magnitude. When analysing individual peptide recognition, 3 patterns were found: recognition of the autologous peptide only, cross-clade recognition and heterologous peptide only. If only the peptide pool corresponding to each individualLs infecting subtype had been used, an underestimation of up to 66% of the breadth of response would have been obtained. Quality of concordant and discordant responses was analyzed by flow cytometry revealing distinct patterns of magnitude and functionality, mainly attributed to peptide offsetting. Conclusion: The use of 2 different peptide sets enhanced the sensitivity of T cell response detection between 33 and 66%. The location of the minimal epitope within a given peptide also affected the effector functions of reactive T cells. This must be taken into account when choosing the best antigens to prime and then screen CTL responses.