To gain further insights into the genetic and immunological basis of natural resistance/susceptibility to infection, here we investigated the relationship between plasma cytokine levels, α-defensin levels, specific immunological (CD4+T cells, anti-Env binding and neutralizing antibodies) and virological (HIV DNA and RNA) parameters and MHC class I and II haplotypes in 21 MCM infected with SHIVSF162P4cy. Here, CD4 is linked to infection.