Factors influencing the interaction of herpes simplex virus glycoprotein C with the third component of complement

The factors influencing the interaction of herpes simplex virus (HSV) glycoprotein C (gC) with the third component of complement (C3) were investigated in this study. The ability of gC of HSV type 1 (gC-1) to bind to the C3b fragment of C3 was found to be influenced by cell specific processing of gC-1 in a different manner, binding being remarkably enhanced in some cell lines following removal of sialic acid residues. Testing several intertypic recombinants of HSV we found that only strains expressing gC-1 exhibited binding to C3b, even though their genome consisted mainly of HSV-2 sequences in some recombinants. Expression of type-2 glycoproteins gB, gD, gE, gG, gH, and gI did not alter the ability of gC-1 to bind to C3b. Rosetting of HSV-1 infected Vero cells with C3b-coated red blood cells (EAC) was found to be temperature dependent and could be inhibited with purified C3b and anti-C3 antibodies. Polyanions like heparin or dextran sulfate were also inhibitory in a dose dependent manner, whereas C3d, neomycin and other aminoglycoside antibiotics failed to block. As the tested polyanions are also known to inhibit the infectivity of HSV, it could be speculated, that the complement binding function and the heparin-binding/attachment function of gC might be related.