Taken together, the generation of HOCl-modified serum albumins is very simple, cost effective and needs no highly specialized laboratory equipment. We suggest that HIV-1 neutralization by HOCl-modified serum albumins is the result of masking the gp120 molecule. We have shown that the CD4 binding site and other regions, like the V3 loop, are partially masked by HOCl-modified serum albumins. Masking the viral gp120/gp41 envelope complex might be a simple but promising strategy to inactivate HIV-1 and therefore prevent infection when applied, for example, as a topical microbicide. Human Pregnancy Specific Beta-1-Glycoprotein 1 (PSG1) Has a Potential Role in Placental Vascular Morphogenesis Previous studies suggest that human pregnancy specific beta-1-glycoproteins (PSGs) play immunomodulatory roles during pregnancy; however, other possible functions of PSGs have yet to be explored. We have observed that PSGs induce transforming growth factor beta 1 (TGFB1), which among its other diverse functions inhibits T-cell function and has proangiogenic properties. The present study investigates a potential role for PSG1, the most abundant PSG in maternal serum, as a possible inducer of proangiogenic growth factors known to play an important role in establishment of the vasculature at the maternal-fetal interface. To this end, we measured TGFB1, vascular endothelial growth factors (VEGFs) A and C, and placental growth factor (PGF) protein levels in several cell types after PSG1 treatment. In addition, tube formation and wound healing assays were performed to investigate a possible direct interaction between PSG1 and endothelial cells. PSG1 induced up-regulation of both TGFB1 and VEGFA in human monocytes, macrophages, and two human extravillous trophoblast cell lines. We did not observe induction of VEGFC or PGF by PSG1 in any of the cells tested. PSG1 treatment resulted in endothelial tube formation in the presence and absence of VEGFA. Site-directed mutagenesis was performed to map the essential regions within the N-domain of PSG1 required for functional activity. We found that the aspartic acid at position 95, previously believed to be required for binding of PSGs to cells, is not required for PSG1 activity but that the amino acids implicated in the formation of a salt bridge within the N-domain are essential for PSG1 function. Pregnancy specific beta-1-glycoproteins (PSGs)-previously known as SP1-are members of the carcinoembryonic antigen (CEA) family and are highly glycosylated proteins secreted by the placenta [1] . Human PSGs have been detected in the maternal serum as early as 3 days postfertilization, coinciding with the attachment of the blastocyst to the uterine wall [2] . Previous studies have reported abnormal levels of PSGs in complicated pregnancies and have shown their importance for the maintenance of a successful pregnancy [3] .