HIV glycomics and glycoproteomics

Bonomelli, Camille, Crispin, Matthew, Scanlan, Chris N. and Doores, Katie J. (2014) HIV glycomics and glycoproteomics. In, Pantophlet, R. (ed.) HIV Glycans in Infection and Immunity. New York. Springer, pp. 1-25. (doi:10.1007/978-1-4614-8872-9_1).

Abstract

The HIV-1 surface glycoprotein, gp120, is made of a rapidly mutating protein core, encoded by the viral genome, and an extensive carbohydrate shield which is synthesized by the host cell. HIV gp120 is a highly glycosylated protein, with an average of 25 potential N-linked glycosylation sites (PNGS). Determination of the site occupancy, microheterogeneity, and chemical structure of glycans attached to the potential glycosylation sites on gp120 have been performed on recombinant gp120 and gp140 by site analysis of glycosylation involving a combination of chromatography and mass spectrometry techniques. These studies were complemented by lectin-binding studies, and finally by mass spectrometric glycosylation analysis of gp120 isolated directly from infectious virions produced in peripheral blood mononuclear cells (PBMCs). In contrast to host cell glycoproteins, gp120 was shown to contain a population of incompletely processed oligomannose-type glycans that interact with host lectins, promote HIV infection, and alter cell signaling. These glycans also form the basis of the epitopes of several highly potent HIV broadly neutralizing antibodies isolated from HIV-infected individuals, making them a key feature for immunogen design. Furthermore, an elevated level of oligomannose-type glycans was evidenced on gp120 isolated from HIV-1 virions produced in PBMCs, compared to recombinant material, along with a subset of highly processed and sialylated, bi-, tri-, and tetra-antennary complex-type glycans. The effect of variation in viral production systems has also been reported, with envelope glycoprotein derived from pseudoviral particles produced in human embryonic kidney (HEK) 293T cells exhibiting predominantly an oligomannose population, compared to gp120 isolated from a single-plasmid infectious molecular clone. The gp120 glycan profile is remarkably similar across primary viral isolates from Africa, Asia, and Europe and consequently represents an attractive target for vaccine development. Finally, glycan remodeling and mutagenesis can also be employed for pseudoviral particle production and recombinant protein expression, to probe broadly neutralizing antibody specificity, structural analysis, and immunogen design.

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Contributors

Author: Matthew Crispin

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