HIV-1 assembly depends on its structural protein, Gag, which after synthesis on ribosomes, traffics to the late endosome/plasma membrane, associates with HIV Env glycoprotein, and forms infectious virions. While Env and Gag migrate to lipid microdomains, their stoichiometry and specificity of interaction are unknown. Pseudotyped viral particles can be made with one viral core surrounded by heterologous envelope proteins. Taking advantage of this property, we analyzed the association of HIV Env and Ebola glycoprotein (GP), with HIV-1 Gag coexpressed in the same cell. Though both viral glycoproteins were expressed, each associated independently with Gag, giving rise to distinct virion populations, each with a single glycoprotein type. Confocal imaging demonstrated that Env and GP localized to distinct lipid raft microdomains within the same cell where they associated with different virions. Thus, a single Gag particle associates "quantally" with one lipid raft, containing homogeneous trimeric viral envelope proteins, to assemble functional virions.

Phospholipase A 2 (PLA 2 ) proteins affect cellular activation, signal transduction, and possibly innate immunity. A specific secretory PLA 2 , sPLA 2 -X, is shown here to neutralize human immunodeficiency virus type 1 (HIV-1) through degradation of the viral membrane. Catalytic function was required for antiviral activity, and the target cells of infection were unaffected. sPLA 2 -X potently reduced gene transfer of HIV-1 Env-pseudotyped lentivirus vectors and inhibited the replication of both CCR5-and CXCR4-tropic HIV-1 in human CD4 ؉ T cells. Virions resistant to damage by antibody and complement were sensitive to lysis by sPLA 2 -X, suggesting a novel mechanism of antiviral surveillance independent of the acquired immune system.