How can Breast Milk Transmit HIV

Abstract:

HIV (Human Immunodeficiency Virus) is a virus belonging to the retrovirus group. It infects cells expressing the CD4 antigen. These cells include T helper cells, monocytes, macrophages, Langerhan’s cells and dendritic cells.

HIV (Human Immunodeficiency Virus) is a virus belonging to the retrovirus group. It infects cells expressing the CD4 antigen. These cells include T helper cells, monocytes, macrophages, Langerhan’s cells and dendritic cells. The immune system gets progressively damaged and the CD4 positive cells count declines steadily. As a result the cells mediated immune response is lost, so the host becomes immuno-compromised. When the CD4+ cell count drops below a critical level, the patient is said to have AIDS (Acquired Immune Deficiency Syndrome). This favors infections with various opportunistic organisms. The AIDS patients die not due to the HI virus, but due to serious infections caused by other organisms.

HIV is transmitted from an infected person to another through body fluids like, blood, semen, vaginal secretions and breast milk, because these body fluids contain the virus. When an HIV infected woman gets pregnant, the next problem she faces is “Will my child also get HIV?” The child can acquire HIV from the mother during second or third trimesters of pregnancy, during delivery, or during breast feeding. There are successful intervention methods that can prevent vertical transmission of HIV during pregnancy and labour, but unfortunately we still do not have an effective way to prevent transmission during breast feeding.

The exact mechanism by which breast milk transmit HIV is not known, but  scientists have found out that the breast milk contains the virus. The breast milk contains both the cell free virus and the cell associated virus, but which of these is important in infecting the child is not known. The plasma virus concentration that is required for it to appear in the breast milk is also yet to be studied.

When the child drinks the mother’s milk, the virus enters the child’s gut, but the mechanism by which they cross the mucosa is not well understood. The virus can penetrate the mucosa especially when there is a breach in the submucosa. Trancytosis through M cells and enterocytes with specific receptors can also occur. Tonsils are the next place where the virus can enter the blood stream. As the frequency and duration of the breast feeding increases, the risk of the child to acquire the infection also increases.

If the mother has mastitis, there is a higher chance for the virus to appear in large numbers in the breast milk. This occurs as a result of vasodilatation of the blood vessels. As a result the child is exposed to a higher number of virus, making him more viable to acquire the infection.

As discussed above HIV infected mothers can transmit the virus to their children during breast feeding. Therefore, reduction of HIV infected females in the reproductory age group in is very essential.  

Sources: Medical Microbiology 2nd edition (Mims)
www.unfpa.org/.../276_filename_HIV_PREV_BF_GUIDE_ENG.pdf