Introduction: CC and CXC chemokines may play a role in mother-to-child HIV-1 transmission by blocking HIV-1 binding to chemokine receptors and impeding viral entry into cells. Methods: To define correlates of breastmilk chemokines and associations with infant HIV-1 acquisition, chemokines in breastmilk and infant HIV-1 infection risk were assessed in an observational, longitudinal cohort study. We measured MIP-1α, MIP-1β, RANTES, and SDF-1 in month 1 breastmilk specimens from HIV- 1-infected women in Nairobi and HIV-1 viral load was calculated in maternal plasma and breastmilk at delivery and 1 month postpartum. Infant infection status was determined at birth and months 1, 3, 6, 9, and 12. Results: Among 281 breastfeeding women, 60 (21%) of their infants acquired HIV-1 during follow-up, 39 (65%) of whom became infected intrapartum or after birth. MIP-1α, MIP-1β, RANTES, and SDF-1 were all positively correlated with breastmilk HIV-1 RNA (P < 0.0005). Women with clinical mastitis had 50% higher MIP-1α and MIP-1β levels (P < 0.001 and P=0.006, respectively) and women with subclinical mastitis (breastmilk Na+/K+ > 1) had ∼70% higher MIP-1α, MIP-1β and RANTES (P < 0.002 for all) compared to women without mastitis. Independent of breastmilk HIV-1, increased MIP-1? and SDF-1 were associated with reduced risk of infant HIV-1 (RR=0.4; 95% CI 0.2-0.9; P=0.03 and RR=0.5; 95% CI=0.3-0.9; P=0.02, respectively) and increased RANTES was associated with higher transmission risk (RR=2.3; 95% CI 1.1- 5.3; P=0.04). Conclusions: These observations suggest a complex interplay between virus levels, breastmilk chemokines, and mother-to-child HIV-1 transmission and may provide insight into developing novel strategies to reduce infection across mucosal surfaces.
Keywords: mip, rantes, sdf, chemokines, mother-to-child hiv transmission, breastmilk