CD4 and infection: However, the infection of CD4-negative cell lines have been described, leading to the identification of galactosylceramide (Galβ1-1′Cer, GalCer) [15,16,17,18,19,20], globotriaosylceramide (Gb3) and ganglioside GM3 [13,21,22,23] as alternate entry (co-)receptors and to the suggestion that GSL microdomains stabilize HIV-1 attachment to the cell surface and facilitate co-receptor recruitment [13,24,25].