SAMHD1 and HIV-1 infection: While HIV-1 infection of these myeloid cells by cell-free viruses is known to be strongly restricted (28, 63), this new mechanism of virus spreading in myeloid cells by cell fusion escapes the restriction imposed by SAMHD1 and leads to the formation of highly virus-productive MGCs reminiscent of the infected MGCs originating from myeloid cells observed in vivo in infected patients and SIV-infected macaques.