Dear Sir,

See this file may be useful for you.

Without any antiretorviral therapy for the mother or infant, roughly 25% of infants are infected at birth.  With good antiretroviral therapy the percentage infected can be reduced to less than 1%.  Viral load in the mother during the last month of pregnancy is sure to correlate to some degree with infant infections, but viral load in the mother is not all about the "immune strength" of the mother, it also has a lot to do with length of time the mother has been infected, and many other factors.  Although very good antiretorviral therapies have only been available sine 1997 or so, adequate treatments to prevent most mother-to-infant transmissions were available by 1990 or so, and it would not be ethical to study untreated mothers and infants.

The genotype of mother and child will also influence the risk of transmission and progression to infection: if the mother has a protective HLA genotype, that may lower their virus load and reduce the chance of transmission; and a protective HLA genotype in the child may do the same (although less likely due to immaturity of the immune system). If you want to read more about HLA-HIV interactions, try these: http://link.springer.com/article/10.1007/s00430-013-0314-1  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4716577/

http://www.sciencedirect.com/science/article/pii/S0966842X14002650

Yes, because when the immune system chut down, HIV viral load arise therethore the transmission risk to child take a jump.

Dear Chinwe, 

Maternal immune system is an important determinant of vertical transmission whether in - utero, at the time of delivery or during breastfeeding. An HIV infected mother with advanced disease and not on ART has a higher risk of transmission because her immunity as a function of CD4 cell count and function is defective.  The viral load is thus not under control. It is well established that uncontrolled VL, low CD4 and not taking ARV therapy are potent risk factors for MTCT in pregnancy, during labour and during breastfeeding. Please check earlier WHO publications ànd guidelines for more details.