: Human CD300a is known to promote the infection by dengue and other enveloped viruses and is overexpressed on CD4 T cells from HIV-1-infected patients. We found that infected CD4+RA- T cells from untreated HIV-1-infected patients were mostly CD300a+. Furthermore, CD300a expressing CD4+RA- T cells from healthy donors were significantly more infected by HIV-1 in vitro than CD300a- cells. CD300a might represent a biomarker of susceptibility to HIV-1 infection on memory CD4 T lymphocytes.