A milk protein lactoferrin enhances human T cell leukemia virus type I andsuppresses HIV-1 infection

Human T cell leukemia virus type I (HTLV-I) and HIV-1, causative agents of adult T cell leukemia/lymphoma and AIDS, respectively, are transmitted vert ically via breast milk. Here we demonstrate that lactoferrin, a milk protei n that has a variety of antimicrobial and immunomodulatory activities, faci litates replication of HTLV-1 in lymphocytes derived from asymptomatic HTLV -1 carriers and transmission to cord blood lymphocytes in vitro. Transient expression assays revealed that lactoferrin can transactivate HTLV-1 long t erminal repeat promoter. Tn contrast, lactoferrin inhibits HIV-1 replicatio n, at least in part, at the level of viral fusion/entry. These results sugg est that lactoferrin may have different effects on vertical transmission of the two milk-borne retroviruses.