CD4 and AIDS: To explain the differences between Indian and Chinese RM with respect to how SIV infection affects the dynamics of CD4 + CCR5+ T cells, Monceaux et al. proposed that since the drastic decline of the pool of CD4 + CCR5+ T cells in Indian RM is a key factor for the rapid disease progression during both acute and chronic infection, the direct effect of virus replication[12] might be the major determinant of the immune dysfunction that implicates the disease progression to AIDS and death.