In agreement, immunohistochemical analyses performed in macaques infected with simian immunodeficiency viruses (SIVs) revealed the presence of infected tissue-resident and monocyte-derived macrophages in the lymph nodes, spleen, CNS, genital and gastrointestinal tracts, lungs, liver, and kidneys early after infection or under conditions of CD4+ T cell depletion, similar to what was observed at late stages of AIDS in HIV-1-infected patients [4,17,23,49,73,74,75,76,77,78]. Here, CD4 is linked to infection.