CD209 x gp41

Some dendritic cells (DC) express a cell‐surface lectin called ‘dendritic cell‐specific intracellular adhesion molecule 3 (ICAM‐3)‐grabbing non‐integrin’ (DC‐SIGN). DC‐SIGN has been shown to mediate a type of infection called ‘trans’ infection, where DC bind human immunodeficiency virus (HIV) and efficiently transfer the virus to T cells. We investigated the possibility that mannose‐binding lectin (MBL), a soluble lectin that functions as a recognition molecule in innate immunity and that binds to HIV, could block trans infection mediated by DC‐SIGN. Binding studies with glycoprotein (gp)120/gp41‐positive and ‐negative virus preparations suggested that DC‐SIGN and MBL bind primarily to glycans on gp120/gp41, as opposed to glycans on host‐cell‐derived proteins, indicating a close overlap in the binding site of the two lectins and supporting the notion that MBL could prevent binding of HIV to DC‐SIGN. Preincubation of X4, R5 or dual‐tropic HIV strains with MBL prevented DC‐SIGN‐mediated trans infection of T cells. The mechanism of MBL blocking trans infection of T cells was at least partly caused by blocking of virus binding to DC‐SIGN positive cells. This study shows that MBL prevents DC‐SIGN‐mediated trans infection of T cells in vitro and suggests that in infected persons, MBL may inhibit DC‐SIGN‐mediated uptake and spread of HIV.

Molecularly derived HIV proteins fail to induce broadly neutralizing antibodies (NAB) and cytotoxic T cell (CTL) responses, which are considered necessary for any effective vaccination. Natural virion proteins of the primary isolates of HIV-1 (pi-HIV), grown in human peripheral blood mononuclear cells (PBMC) followed by viral inactivation and pooling to reflect the antigenic diversity of the prevalent strains in a given population, would provide a novel polyvalent HIV vaccine (HIVAX) capable of inducing both HIV-NAB and CTL. Proven technologies are harnessed to provide a framework for advancing human blood-derived HIVAX. Fresh leukocytes, recovered by gravity flow elution from leukocyte depletion blood filters, or "buffy coats", routinely removed in preparing blood components for transfusion, provide an abundant and safe cell substrate following ficoll-separation of viable PBMC. The low content of wild-type HIV (wt-HIV) in infected plasma can be chaperoned by dendritic cells through their DC-SIGN receptor for gp120 and efficiently expanded in co-culture with CD4-enriched cell substrate in a medium containing human AB serum as a substitute for foetal calf serum. Dimethyl methylene blue (DMMB), ethylene diiimine (EDI), or psoralens can be used to inactivate the virion RNA selectively and the unbound chemicals and their products are removable by molecular sieving. Additional inactivation by physical methods would include proven hydrostatic pressure cycling technology (PCT) and flash pasteurization at 60 degrees C for less than 10 minutes to totally inactivate infectivity of the virions. Our empirical strategy is to pool five different HIV isolates of the prevalent subtype B (U.S.A.) or C (Southern Africa), augmented by other subtypes A, C/B, D, E, and 'X' (new emerging subtypes), to provide a polyvalent HIV vaccine (HIVAX). Immunochemical quantification of the gp120, gp41, p24 and p31 antigen content of HIVAX ensures consistency of the product, and safety is ensured by failure to amplify HIV nucleic acid sequences by RT-PCR and to demonstrate infectivity in animal models. Ultimate efficacy HIVAX must be shown by human clinical trials in the high-risk populations.