Continued...


HIV and breast feeding

HIV is transmitted by breast milk as proved by many studies. Firstly HIV has been isolated from human breast milk. Transmission to child is shown to occur from mother infected with HIV post-natally and who breast fed the infant. Lastly studies done on HIV women who became pregnant have compared rate of vertical transmission in those babies who were breast fed compared to those who were exclusively top fed and showed that there is 14% extra risk related to breast feeding over and above other factors.

HIV in human breast milk

Earliest study by Thiry et al in 1985 showed presence of HIV in cell free part of breast milk by viral cultures from samples of breast milk obtained 1-5 months after delivery in 3 asymptomatic HIV mothers. Subsequently many studies have confirmed presence of HIV in human milk. Bucens et al demonstrated HIV in histiocytic cells of human milk as well as cell free component of breast milk and demonstrated it by EM studies. Raff et al demonstrated presence of HIV by PCR. It was shown that presence of P24 antigen in breast milk did not correlate with CD4 cell count or B2 microglobulin levels or clinical status of mother. HIV has been shown in high titers in colostrum as well as in breast milk for first 4 days after delivery. Some have shown it to be present for as long as 4-6 months or even beyond that after delivery. Vitamin A deficiency in mother leads to increased titers of HIV in breast milk. Other conditions like breast abscess, mastitis or sore nipple can lead to contamination of breast milk with mother's blood.

Free HIV can infect CD4+ cells lining the GI tract of baby. Infected maternal mononuclear cells present in breast milk can pass through mucous membranes of baby and infect the baby.

As against this there are some protective factors present in human milk that protect the baby against HIV infection. Goldman et al have shown presence of glycoproteins and other substances like mucins, lysozymes, lactoferrins, T cells, complements and secretory leucocyte protease inhibitor (SLIP) etc that decrease binding of pathogenic organisms to GI tract epithelial cells and decrease chances of transmission via BM, including that of HIV. Presence of anti-HIV antibodies especially anti-gp120, anti-gp40, IgG as well as anticore IgM and IgA antibodies in human milk have been shown by Western Blot technique. This can also decrease the infection of baby.

Post natal HIV infection of mothers

Earliest report described a mother who was HIV negative till delivery and became HIV positive through blood transfusion given to mother post delivery. She breast fed her child and later on child also become HIV positive. It was presumed to be via breast milk. Since then more than 8 such cases have been reported. Subsequently studies have reviewed these cases and concluded that breast milk was the cause of transmission in most of these cases including a case of HIV transmission by an HIV infected wet nurse. The risk of transmission in such cases was 25-30% which is high because the mothers were recently infected and had high viral load and low levels of antibodies to be transferred via breast milk

Other evidence of transmission via breast milk comes from studies done in Australia and Africa where they followed up mothers who were HIV negative at delivery who were subsequently followed up for long term. Some of them became HIV positive through heterosexual route. All of them breast fed their babies for as long as 6-24 months. The overall rate of transmission in these babies was found to be 29%, which is again high due to recent conversion in these mothers with high viral load.

Overall both these types of reports of individual cases as well as the long term followed studies of post natal HIV in mothers have proved definite transmission of HIV via breast milk with 30% rate of transmission.