Background: Quiescent CD4+ T lymphocytes are a reservoir for the human immunodeficiency virus type-1 (HIV-1) in adults treated with highly active antiretroviral therapy, and in whom HIV-1 cannot be isolated using standard culture techniques. A reservoir of latently infected, resting CD4+ T lymphocytes has not been reported in children.

Methods: A quantitative, microculture assay of highly purified(>99% purity) resting CD4+ T lymphocytes was used to measure the frequency of resting CD4+ T lymphocytes harboring replication competent virus in 14 children with perinatally acquired HIV-1 infection.

Results: The median age of the children studied was 9 years(range 3 -13 years). Thirteen of the fourteen children were receiving treatment with antiretroviral agents, four with combination therapy including a protease inhibitor, A 10 year old, asymptomatic child had not received antiretroviral therapy. The mean frequency of latently infected, resting CD4+ T lymphocytes harboring replication competent virus was 6.6 per 1 × 106 cells (range <1 to 2,503 per 1 × 106 cells). In 6 children with plasma RNA levels greater than 5,000 copies/ml (median number 36,351 copies/ml, range 20,713 to 615,000), the mean frequency of latently infected CD4+ T lymphocytes was 47 per 1 × 106 cells (<1 to 2,503 per 1× 106 cells). In 8 children with plasma RNA less than 5,000 copies/ml(median number 265 copies/ml, range <163 to 3,372), the mean frequency of latently infected resting CD4+ cells was lower at < 1.5 per 1 × 10 6 cells (p=0.02). In 4 children receiving combination therapy with a protease inhibitor and with undetectable levels of plasma RNA levels, the mean frequency of latently infected CD4+ T lymphocytes was < 1 per 1 × 106 cells. The frequency of latently infected, resting T lymphocytes correlated with HIV-1 RNA levels (r = 0.75) and inversely with percentage of CD4+ T lymphocytes (r = - 0.68).

Conclusions: The mean frequency of resting CD4+ T lymphocytes harboring replication competent virus in the blood of children with perinatally acquired HIV-1 infection is similar to that found in HIV-1 infected adults (adult mean = 7 per 1 × 10 6 cells). In children, the frequency of latently infected, resting CD4+ T lymphocytes correlated with plasma RNA levels. The lowest frequencies occurred in children with suppression of viral replication. Therapy with highly active antiretroviral agents may decrease the size of this reservoir in children with perinatally acquired HIV-1 infection.