Main characteristics of study mother-child couples, including 8 couples of HIV-1-infected mothers and their breastfed non HIV-infected babies (group I), and 6 couples of HIV-1-infected mothers and their breastfed HIV-1-infected babies (group II).

£World Health Organization (WHO) clinical staging of HIV/AIDS for adults and adolescent with established HIV infection according to the 2010-revised WHO recommendations for HIV care in in babies and children for resource-limited settings [31];$WHO clinical staging of HIV/AIDS for children with established HIV infection according to the 2010-revised WHO recommendations for HIV care in babies and children for resource-limited settings [30]; CD4 T cell count in infants were not available because the national AIDS programme has focused on universal treatment for infants less than 12 months, independently of their clinical or immunological status;*Plasma HIV-1 RNA load was measuredby the Generic HIV-1 RNA quantification assay (Biocentric, Bandol, France), which threshold of detectability is 300 copies/ml [35].The molecular diagnosis of HIV infection was carried out at time of sampling; the timing of HIV infection in study children could not be assessed.NA: Not applicable.