Individual HIV Type 1 Envelope-Specific T Cell Responses and Epitopes Do Not Segregate by Virus Subtype

HIV-1 vaccines are often designed to target one or several virus subtype(s). They therefore include antigens(e.g., env or env/gag/pol) from each targeted subtype to elicit subtype-directed immunity. To determine if individual T cells respond to HIV-1 antigens in a subtype-directed manner, we selected four T cell hybridomas, each representative of a different immunodominant response toward a subtype B envelope. Hybridomas were tested for responses toward 20 subtype B envelope proteins and one protein each from subtypes A, C, and D. None of the hybridomas cross-reacted with all subtype B envelopes, yet three responded to a non-B protein. Core epitopes and flanking regions affected responsiveness. This lack of subtype-directed activity was corroborated by analyses of the Los Alamos database; like immune responses, epitope distributions were not dictated by subtype. Results highlight the difficulty of predicting immune responses based on subtype alone and encourage considerations of antigenic disparity in addition to subtype disparity during HIV-1 vaccine design.