Influence of N-Linked Glycans in V4-V5 Region of Human Immunodeficiency Virus Type 1 Glycoprotein gp160 on Induction of a Virus-Neutralizing Humoral Response

Abstract

One of the functions of N-linked glycans of viral glycoproteins is protecting otherwise accessible neutralization epitopes of the viral envelope from neutralizing antibodies. The aim of the present study was to explore the possibility to obtain a more broadly neutralizing immune response by immunizing guinea pigs with gp160 depleted of three N-linked glycans in the CD4-binding domain by site-directed mutagenesis. Mutant and wild type gp160 were formulated into immunostimulating complexes and injected s.c. into guinea pigs. Both preparations induced high serum antibody response to native gp120 and V3 peptides. Both preparations also induced antibodies that bound equally well to the V3 loop or the CD4-binding region, as determined by a competitive enzyme-linked immunosorbent assay (ELISA). The sera from animals, immunized with mutated glycoprotein, did not neutralize nonrelated HIV strains better than did sera from animals, immunized with wild type glycoprotein. Instead, a pattern of preferred homologous neutralization was observed, i.e., sera from animals, immunized with mutant gp160, neutralized mutant virus better than wild type virus, and vice versa. These data indicated that elimination of the three N-linked glycans from gp160 resulted in an altered local antigenic conformation but did not uncover hidden neutralization epitopes, broadening the immune response.

Localization of CD4+T cell epitope hotspots to exposed strands of HIV envelope glycoprotein suggests structural influences on antigen processing

“…In support of this theory, antibodies and CD4 ϩ T cells have been shown to recognize epitopes on the HIV env V2, V3, and V4 loops. However, the exposed loops of V1 and V5 regions of HIV env are also known to elicit antibody responses (50)(51)(52), yet neither contributed to the T h -epitope panel defined here. The question of a role, or otherwise, for antibody binding as a determinant of CD4 ϩ T cell responsiveness could be addressed experimentally by repeating the present analysis in IgϪ͞Ϫ MT mice.…”

N-Linked Glycosylation of the HIV Type-1 gp120 Envelope Glycoprotein as a Major Determinant of CCR5 and CXCR4 Coreceptor Utilization

“…Additionally, with simian immunodeficiency virus it has been shown that de-glycosylation events within the V1 region of the envelope result in a virus with increased antibody neutralization potential (61). With HIV-1, the N-linked glycosylation pattern has also been shown to have a varied effect on the induction of neutralizing antibodies (44,(62)(63)(64)(65)(66)(67). It is therefore possible that the selection of viruses with different coreceptor utilization patterns and replication phenotypes, based upon altered envelope glycosylation events, may be aided by the escape from a neutralizing antibody response.…”

ISCOMs: an adjuvant with multiple functions

“…These include guinea pig [127,128], turkey [129,130], cat [47,58], rabbit [39,41,43,131], dog [132], seal [133], sheep [134][135][136], pig [137], cow [138,139], and horse [140,141]. Of particular interest with regard to human applications is the ability of ISCOMs to induce strong immune responses in monkeys.…”