Objectives: HIV-exposed uninfected (HEU) infants have higher rates of severe and fatal infections compared with HIV-unexposed (HUU) infants, likely due to immune perturbations. We hypothesized that alterations in natural killer (NK) cell activity might occur in HEU infants and predispose them to severe infections. Design: Case-control study using cryopreserved peripheral blood mononuclear cells (PBMCs) at birth and 6 months from HEU infants enrolled from 2002 to 2009 and HUU infants enrolled from 2011 to 2013. Methods: NK cell phenotype and function were assessed by flow cytometry after 20-h incubation with and without K562 cells. Results: The proportion of NK cells among PBMCs was lower at birth in 12 HEU vs. 22 HUU (1.68 vs. 10.30%, p < 0.0001) and at 6 months in 52 HEU vs. 72 HUU (3.09 vs. 4.65%, p = 0.0005). At birth, HEU NK cells demonstrated increased killing of K562 target cells (p < 0.0001) and increased expression of CD107a (21.65 vs. 12.70%, p = 0.047), but these differences resolved by 6 months. Stimulated HEU NK cells produced less interferon (IFN)γ at birth (0.77 vs. 2.64%, p = 0.008) and at 6 months (4.12 vs. 8.39%, p = 0.001), and showed reduced perforin staining at 6 months (66.95 vs. 77.30%, p = 0.0008). Analysis of cell culture supernatants indicated that lower NK cell activity in HEU was associated with reduced interleukin (IL)-12, IL-15, and IL-18. Addition of recombinant human IL-12 to stimulated HEU PBMCs restored IFNγ production to that seen in stimulated HUU cultures. Conclusion: NK cell proportion, phenotype, and function are altered in HEU infants. NK cell cytotoxicity and degranulation are increased in HEU at birth, but HEU NK cells have reduced IFNγ and perforin production, suggesting an adequate initial response, but decreased functional reserve. NK cell function improved with addition of exogenous IL-12, implicating impaired production of IL-12 by accessory cells. Alterations in NK cell and accessory cell function may contribute to the increased susceptibility to infection in HEU infants.
Bibliographical noteFunding Information:
The authors would like to thank the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) International Site Development Initiative (NISDI) Longitudinal Study in Latin American Countries (LILAC) group for providing samples, statistical support, and funding for supplies and reagents. They would also like to thank Drs. Heather Haughen, Myron Levin, and Betsy McFarland for their critical review of this work. These data were presented in part at the 2016 American Association of Immunologists Annual Meeting, Seattle, WA, USA, and at IDWeek 2015, San Diego, CA, USA. This investigation was supported by NIH/NCATS Colorado CTSI (Grant Number UL1 TR001082). Contents are the authors' sole responsibility and do not necessarily represent official NIH views. Supported by NICHD Contracts N01-HD-3-3345 (2002-2007), HHSN267200800001C (2007-2012), and HHSN275201300003C (2012-2017). The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institutes of Health or the Department of Health and Human Services. CS was supported by the National Institutes of Health under the Ruth L. Kirschstein National Research Service Award (Grant Number T32AI007447-23) from the Colorado HIV-1 Research Training Program (PI Thomas Campbell). Research activities in Brazil were supported by the FAPESP (Fundação de Apoio à Pesquisa do Estado de São Paulo) (Grant Number 2010/19539-9 to MM-P).
© 2017 Smith, Jalbert, de Almeida, Canniff, Lenz, Mussi-Pinhata, Cohen, Yu, Amaral, Pinto, Alarcon, Siberry and Weinberg.
- K562 cells
- Natural killer cells
- Respiratory tract infections