Recombinant HIV type 2 Glycoprotein 36 [His]

Objective: The ability to induce neutralizing antibodies may be the most important feature of an antiretroviral vaccine, preventing infection of target cells and subsequent integration of the virus into the cellular genome where the virus may persist. Broadly neutralizing antibodies directed against conserved epitopes in the membrane proximal external region (MPER) of the transmembrane envelope (TM) protein gp41 of HIV-1 such as the monoclonal antibodies (mAb) 2F5 and mAb 4E10 have been found in infected individuals; however, all attempts to induce such antibodies failed. In individuals infected with HIV-2 such antibodies were not yet reported. Methods: Two recombinant proteins corresponding to the ectodomain of the TM protein gp36 of HIV-2 were produced, rats were immunized and sera were analyzed for binding and neutralizing antibodies. Results: Although binding antibodies were induced, none of the sera neutralized HIV-2. Most interestingly, epitope mapping showed specific binding of the antibodies to the MPER of gp36, to a region homologous to the binding site of the mAb 4E10 in gp41 of HIV-1. Conclusions: Although MPER-specific antibodies were induced by vaccination with gp36, these antibodies did not neutralize HIV-2. This is similar to the situation with HIV-1, but in contrast to that with gammaretroviruses. Copyright (C) 2011 S. Karger AG, Basel

Proteolytic activation of the precursor envelope glycoproteins gp160 of human immunodeficiency virus type 1 (HIV-1) and gp140 of HIV-2, a prerequisite for viral infection, results in the formation of gp120/gp41 and gp125/gp36, respectively. Cleavage is mediated by cellular proteases. Furin, a member of the eukaryotic subtilisin family, has been shown to be an activating protease for HIV. Here, we compared the presence of furin and other mammalian subtilisins in lymphatic cells and tissues. Northern blot analyses revealed that furin and the recently discovered protease LPC/PC7 were the only subtilisin-like enzymes transcribed in such cells. Furin was identified as an enzymatically active endoprotease present in different lymphocytic, as well as monocytic, cell lines. When expressed from vaccinia virus vectors, the proprotein convertases were correctly processed, transported, and secreted into the media and enzymatically active. Coexpression of different subtilisins with the HIV envelope precursors revealed that furin and LPC/PC7 are able to cleave HIV-1 gp160. Moreover, both enzymes proteolytically processed the envelope precursor of HIV-2. gp140 was also cleaved to some extent by PC1, which is not, however, present in lymphatic cells. Furin- and LPC/PC7-catalyzed cleavage of HIV-1 gp160 resulted in biologically active envelope protein. In conclusion, among the known members of the subtilisin family, only furin and LPC/PC7 fulfill the requirements of a protease responsible for in vivo activation of HIV envelope glycoproteins.