UvA - DARE ( Digital Academic Repository ) Evolution of the HIV - 1 envelope glycoproteins with a disulfide bond between gp 120 and gp 41

Background: We previously described the construction of an HIV-1 envelope glycoprotein complex (Env) that is stabilized by an engineered intermolecular disulfide bond (SOS) between gp120 and gp41. The modified Env protein antigenically mimics the functional wild-type Env complex. Here, we explore the effects of the covalent gp120 – gp41 interaction on virus replication and evolution. Results: An HIV-1 molecular clone containing the SOS Env gene was only minimally replication competent, suggesting that the engineered disulfide bond substantially impaired Env function. However, virus evolution occurred in cell culture infections, and it eventually always led to elimination of the intermolecular disulfide bond. In the course of these evolution studies, we identified additional and unusual second-site reversions within gp41. Conclusions: These evolution paths highlight residues that play an important role in the interaction between gp120 and gp41. Furthermore, our results suggest that a covalent gp120 – gp41 interaction is incompatible with HIV-1 Env function, probably because this impedes conformational changes that are necessary for fusion to occur, which may involve the complete dissociation of gp120 from gp41. Background The trimeric HIV-1 envelope glycoprotein complex (Env) mediates viral entry into susceptible target cells. The surface subunit (SU; gp120) attaches to the receptor (CD4) and the coreceptor (CCR5 or CXCR4) on the cell surface, and subsequent conformational changes within the Env complex lead to membrane fusion mediated by the transmembrane subunit (TM; gp41) [1-4]. After intracellular cleavage of the precursor gp160 protein, three gp120 subunits stay non-covalently associated with three gp41 subunits. However, these non-covalent interactions are weak and gp120 dissociates easily from gp41, a process that, if it occurs spontaneously and prematurely, inactivates the Env complex and leads to the exposure of non-neutralizing, immune-decoy epitopes on both gp120 and gp41 [57]. HIV-1 vaccine strategies aimed at generating neutralizing antibodies have yielded various Env immunogens that have gp120 stably attached to gp41, usually by Published: 09 March 2004 Retrovirology 2004, 1:3 Received: 23 February 2004 Accepted: 09 March 2004 This article is available from: http://www.retrovirology.com/content/1/1/3 © 2004 Sanders et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. Retrovirology 2004, 1 http://www.retrovirology.com/content/1/1/3