Infrequent detection of HIV-1-specific, but not cytomegalovirus-specific, CD8⁺ T cell responses in young HIV-1-infected infants

Early potent combination antiretroviral therapies (ART) for HIV-1 infection can preserve or restore immune function, but control of viral replication early in infection may interfere with the development of HIV-1-specific immune responses. Using an IFN-γ ELISPOT assay, we evaluated the breadth and intensity of HIV- 1-specific CD8⁺ T cell responses in 17 vertically infected infants who began ART at 1-23 mo of age. CMV-specific responses were also characterized in three infants coinfected with HIV-1 and CMV. Before ART, HIV-1-specific CD8⁺ T cell responses were detected in two of 13 (15%) infants <6 mo of age. HIV-1 -specific CD8⁺ T cells became undetectable in these two infants after the control of viral replication. Intermittent HIV-1 -specific responses were noted in six infants who did not experience durable control of viral replication. In contrast, HIV-1-specific responses were detected before ART in four of four infants >6 mo of age and became persistently undetectable in only one child. CMV-specific CD8⁺ T cell responses were persistently detected in all HIV-1 and CMV coinfected infants. In conclusion, HIV-1-specific CD8⁺ T cell responses were less commonly detected before therapy in young infants than in older infants. Suppression of viral replication appeared to interfere with the development and maintenance of HIV-1-specific CD8⁺ T cell responses. The detection of CMV-specific responses in HIV-1 and CMV coinfected infants suggests a selective defect in the generation or maintenance of HIV-1-specific CD8⁺ T cell responses. Therapeutic HIV-1 vaccine strategies in young infants may prolong the clinical benefit of ART by expanding the HIV-1-specific CD8⁺ T cell pool.