T-lymphocyte subsets in HIV-infected and high-risk HIV-uninfected adolescents - Retention of naive T lymphocytes in HIV-infected adolescents

Background: The capacity of the immune system of adolescents to generate an d repopulate naive and memory cell populations under conditions of normal h omeostasis and human immunodeficiency virus (HIV) infection is largely unkn own. Objective: To assess lymphocyte subsets in HIV-infected and high-risk HIV-n egative adolescents. Design: The Reaching for Excellence in Adolescent Care and Health Project o f the Adolescent Medicine HIV/AIDS Research Network recruits a cohort of HI V-infected and high-risk HIV-uninfected adolescents, aged 13 to 18 years 36 4 days, into a study of biomedical and behavioral features of HIV infection as seen in the context of full availability of primary care and HIV-relate d consultative services. Lymphocyte phenotypes were determined using standa rd 3-color flow cytometry. Setting: The Reaching for Excellence in Adolescent Care and Health Project is carried out at 16 clinical sites in 13 urban areas. Participants: T-lymphocyte subsets are reported in 192 HIV-positive and 78 HIV-negative youths. Results: For HIV-positive subjects, the total CD4(+) cell count and the per centage of CD4(+) cells are decreased when compared with those of the HIV-n egative controls (P<.001). The reduction in total CD4(+) cells reflects a l oss of naive, and memory, CD4(+) cells compared with HIV-negative youths. H uman immunodeficiency virus-infected adolescents, many of whom have been in fected recently (ie, those with CD4(+) cell counts greater than or equal to 0.500 x 10(9)/L [500/mu L]), have a significant increase in naive CD8(+) c ells compared with HIV-negative youths (P<.01). There also is a significant increase in memory CD8(+) cells at all strata of total CD4(+) cells compar ed with HIV-negative youths (P<.01). The increase in naive CD8(+) cells in those subjects with CD4(+) cell counts of 0.500 x 10(9)/L or greater is a u nique finding in this cohort. Conclusions: This study demonstrates high levels of naive CD8(+) cells in r esponse to HIV infection in adolescents with CD4(+) cell counts of 0.500 x 10(9)/L or greater. The presence of high levels of naive CD8(+) cells sugge sts functioning thymic tissue;in some adolescents infected with HIV. Furthe rmore, the normal level of naive CD4(+) cells in adolescents with CD4(+) le vels of 0.500 x 10(9)/L or greater provides additional support for the conc ept of a more robust immune system in HIV-infected adolescents compared wit h HIV-infected adults. These observations suggest that the immune system of HIV-infected adolescents may he capable of better responses to neoantigens and cytotoxic T-lymphocyte responses to HIV than the immune system of infe cted children or adults. Human immunodeficiency virus-infected adolescents may have an immune system that is capable of reconstitution following highl y active antiretroviral therapy.