Abstract

Evidence of the selective increase in pre-NK cells and depletion of mature NK cells contributing to natural control of HIV-1 infection in treatment-naive children

J.R. Romeiro, M.L. Silva, S.M. Elói-Santos, J.A. Pinto

Federal University of Minas Gerais, Belo Horizonte, Brazil

Background: NK cells constitute an important component of innate immune response and have an important role in viral infections. Recent studies show that NK cells may be involved in the control of HIV-1 virus infection. We assessed the NK cells phenotypic profile in a group of long term nonprogressor (LTNP) HIV-1 vertically infected children, which exhibit low viral replication and normal T CD4⁺ lymphocytes counts in the absence of antiretroviral treatment (ART). This context offers a unique opportunity to investigate the immunological characteristics of natural control of HIV-1 infection
Methods: Cross-sectional study carried out in 28 HIV vertically infected children, older than six years. Children were classified as: LTNP (ART naive; CD4 ≥ 25% and/or ≥ 500 cells/mm3; Viral Load < 25.000 copies); immunological failure/virological failure IF/VF (failing ART); immunological success/virological success IS/VS (effective response to ART). Data on uninfected children (NI) were used as controls.
Results: We did not find significant differences in the NK cell counts among the groups assessed (median: 9.08, 10.52, 10.04, 11.61; for LTNP, IF/VF, IS/VS and NI, respectively, p>0.05). NK cells subtypes were also evaluated. Despite the presence of higher percentage of pre-NK cells (CD3^-CD16⁺CD56^-) (median: 1.98, 0.99, 0.50, 0.45), LTNP children presented a reduced percentage of mature NK cells (CD3^-CD16⁺CD56⁺) (median: 1.51, 1.21, 1.80, 2.70). No difference was seen in the percentage of activated NK cells (CD3⁺CD16^-CD56⁺) (median: 0.62, 1.12, 1.04, 0.48). In LTNP children as well as in NI children, pre-NK cell count were positively correlated to CD4⁺T cell count (r=0.70, p=0.03; r=0.69, p=0.02), but did not show any correlation with viral load.
Conclusions: These findings suggest that pre-NK cells may contribute to the mechanism of natural control of HIV-1 infection in children.