HIV‐1–Specific Cytotoxic T Lymphocytes and Breast Milk HIV‐1 Transmission

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Abstract
BackgroundBreast-feeding by infants exposed to human immunodeficiency virus type 1 (HIV-1) provides an opportunity to assess the role played by repeated HIV-1 exposure in eliciting HIV-1–specific immunity and in defining whether immune responses correlate with protection from infection MethodsBreast-feeding infants born to HIV-1–seropositive women were assessed for HLA-selected HIV-1 peptide–specific cytotoxic T lymphocyte interferon (IFN)–γ responses by means of enzyme-linked immunospot (ELISpot) assays at 1, 3, 6, 9, and 12 months of age. Responses were deemed to be positive when they reached ⩾50 HIV-1–specific sfu/1×106 peripheral blood mononuclear cells (PBMCs) and were at least twice those of negative controls ResultsA total of 807 ELISpot assays were performed for 217 infants who remained uninfected with HIV-1 at ∼12 months of age; 101 infants (47%) had at least 1 positive ELISpot result (median, 78–170 sfu/1×106 PBMCs). The prevalence and magnitude of responses increased with age (P=.01 and P=.007, respectively); the median log10 value for HIV-1–specific IFN-γ responses increased by 1.0 sfu/1×106 PBMCs/month (P<.001) between 1 and 12 months of age. Of 141 HIV-1–uninfected infants with 1-month ELISpot results, 10 (7%) acquired HIV-1 infection (0/16 with positive vs. 10/125 [8%] with negative ELISpot results; P=.6). Higher values for log10 HIV-1–specific spot-forming units at 1 month of age were associated with a decreased risk of HIV-1 infection, adjusted for maternal HIV-1 RNA level (adjusted hazard ratio, 0.09 [95% confidence interval, 0.01–0.72]) ConclusionsBreast-feeding HIV-1–exposed uninfected infants frequently had HIV-1–specific IFN-γ responses. Greater early HIV-1–specific IFN-γ responses were associated with decreased HIV-1 acquisition

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