Secretory anti-human immunodeficiency virus (HIV) antibodies in colostrum and breast milk are not a major determinant of the protection of early postnatal transmission of HIV.

The immune response to human immunodeficiency virus (HIV) type 1 was evaluated in breast milk from HIV-infected African mothers who had transmitted and those who had not transmitted HIV to their children through breast-feeding. The levels, specific activities against gp160 and 2 HIV-derived peptides from gp41 and gp120 (V3 loop), and inhibitory activity toward viral transcytosis in vitro of secretory IgA (S-IgA) and IgG purified from breast milk were investigated in 8 transmitting mothers and 18 nontransmitting mothers. S-IgA and IgG antibodies to gp160 and to peptides were found in all breast milk samples. The specific activities of S-IgA and IgG to gp160 and peptides were similar between transmitting and nontransmitting mothers. No difference of the capacity of S-IgA and IgG to block HIV transcytosis in vitro was found between the 2 groups. These results suggest that humoral mucosal immunity to HIV does not appear as a predominant factor for protection against viral transmission through breast milk.