ERVW-1 and HIV-1 infection: Several early studies showed that a polyvalent vaccine, comprising a combination of multiple Env proteins, was better at eliciting broader immune responses than monovalent Env in both rabbits and macaques [5–7], while a clinical phase 2b trial of HVTN505 combining three envelope glycoproteins from clade A, B, and C env genes did not reduce either the rate of acquisition or set point viral load of new HIV-1 infections [7].