HIV-1 Env glycoprotein and HLA-C associate and increase HIV-1 infectivity Serena Ziglio, Dalila Astone, Giulia Danesin, Pierpaolo Racchiolli, Almudena Blanco, Donato Zipeto Laboratory of Molecular Virology, Section of Biology and Genetics, Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134 Verona, Italy Introduction: HLA-C is selectively incorporated into HIV-1 envelope. We reported that viruses produced from HLA-C silenced cells are significantly less infectious and demonstrated a specific association between HLA-C and gp120. Our purpose is to unravel the HLA-C/gp120 association to reveal new targets for the development of neutralizing antibodies as well as new anti-HIV compounds. Methods: Fluorescent-tagged HLA-C and gp120 were prepared and used for bimolecular fluorescence complementation (BiFC) analysis to study their association into cellular compartments. To study the influence of HLA-C polymorphism on viral infectivity, HLA-C molecules corresponding to different alleles were tested for their ability to enhance gp120 fusion efficiency. To identify gp120 domains involved in the association with HLA-C, different gp120 deletion mutants are being constructed and tested. Results: A BiFC complementation signal between HLA-C and gp120 is detectable in the endoplasmic reticulum (ER), Golgi apparatus, late endosomes and on the cell membrane. Confocal microscopy does not show a co-localization signal between gp120 and β2-microglobulin (β2m). No significant differences were observed between HLA-C alleles in their ability to enhance virus infectivity. Discussion: The co-localization analysis shows that HLA-C, most likely as an open conformer, interacts with gp120 early in the ER and that they remain associated up to the cell membrane, travelling together trough the Golgi apparatus and late endosomes. No gp120 and β2m co-localization is evident, suggesting a competition between them for HLA-C binding. Preliminary results show no differences between HLA-C alleles suggesting that HLA-C polymorphism is unlikely to influence the association with gp120.
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