Breast Milk of African Green Monkeys Immunodeficiency Virus Variants in the Transient Compartmentalization of Simian

ostnatal human immunodeficiency virus type 1 (HIV-1)transmission via breast-feeding results in nearly half of the330,000 infant infections occurring annually (1). Interruption ofthis mode of infant HIV-1 transmission is key to achieving anHIV-free generation. Interestingly, natural primate hosts of sim-ian immunodeficiency virus (SIV), who coevolved with the virusforthousandsofyearsandsustainanonpathogenicinfection,ap-pear to transmit the virus to their infants postnatally only rarely(2–6). This negligible rate of SIV transmission via breast-feedingin natural SIV hosts contrasts with that of nonnatural SIV hosts,rhesus macaques, who transmit SIV via breast-feeding at a highrate (7). Understanding the mechanisms underlying the rarity ofbreast milk transmission in natural hosts of SIV could guide thedevelopment of interventions to impede postnatal HIV-1 trans-mission.In humans, high plasma and milk viral loads are associatedwiththeriskofbreastmilktransmissionofHIV(8).However,innatural SIV hosts, African green monkeys (AGMs) (