by
James E. Voss;
Matthew S. Macauley;
Kenneth A. Rogers;
Francois Villinger;
Lijie Duan;
Liang Shang;
Elizabeth A. Fink;
Raiees Andrabi;
Arnaud D. Colantonio;
James E. Robinson;
Robert Johnson;
Dennis R. Burton;
Ashley T. Haase
Vaccination with SIV mac239 δnef provides robust protection against subsequent challenge with wild-type simian immunodeficiency virus (SIV), but safety issues have precluded designing an HIV-1 vaccine based on a live-attenuated virus concept. Safe immunogens and adjuvants that could reproduce identified immune correlates of SIV mac239 δnef protection therefore offer an alternative path for development of an HIV vaccine. Here we describe SIV envelope trimeric gp41 (gp41t) immunogens based on a protective correlate of antibodies to gp41t concentrated on the path of virus entry by the neonatal Fc receptor (FcRn) in cervical vaginal epithelium. We developed a gp41t immunogen-monophosphoryl lipid A adjuvant liposomal nanoparticle for intramuscular (i.m.) immunization and a gp41t-Fc immunogen for intranasal immunization for pilot studies in mice, rabbits, and rhesus macaques. Repeated immunizations to mimic persistent antigen exposure in infection elicited gp41t antibodies in rhesus macaques that were detectable in FcRn cervical vaginal epithelium, thus recapitulating one key feature of SIV mac239 δnef vaccinated and protected animals. Although this strategy did not reproduce the system of local production of antibody in SIV mac239 δnef-vaccinated animals, passive immunization experiments supported the concept that sufficiently high levels of antibody can be concentrated by the FcRn at mucosal frontlines, thus setting the stage for assessing protection against vaginal challenge by gp41t immunization.
Two urea transporters, UT-A1 and UT-A3, are expressed in the kidney terminal inner medullary collecting duct (IMCD) and are important for the production of concentrated urine. UT-A1, as the largest isoform of all UT-A urea transporters, has gained much attention and been extensively studied; however, the role and the regulation of UT-A3 are less explored. In this study, we investigated UT-A3 regulation by glycosylation modification. A site-directed mutagenesis verified a single glycosylation site in UT-A3 at Asn279. Loss of the glycosylation reduced forskolin-stimulated UT-A3 cell membrane expression and urea transport activity. UT-A3 has two glycosylation forms, 45 and 65 kDa. Using sugar-specific binding lectins, the UT-A3 glycosylation profile was examined. The 45-kDa form was pulled down by lectin concanavalin A (Con A) and Galant husnivalis lectin (GNL), indicating an immature glycan with a high amount of mannose (Man), whereas the 65-kDa form is a mature glycan composed of acetylglucosamine (GlcNAc) and poly-N-acetyllactosame (poly-LacNAc) that was pulled down by wheat germ agglutinin (WGA) and tomato lectin, respectively. Interestingly, the mature form of UT-A3 glycan contains significant amounts of sialic acid. We explored the enzymes responsible for directing UT-A3 sialylation. Sialyltransferase ST6GalI, but not ST3GalIV, catabolizes UT-A3 α2,6-sialylation. Activation of protein kinase C (PKC) by PDB treatment promoted UT-A3 glycan sialylation and membrane surface expression. The PKC inhibitor chelerythrine blocks ST6GalI-induced UT-A3 sialylation. Increased sialylation by ST6GalI increased UT-A3 protein stability and urea transport activity. Collectively, our study reveals a novel mechanism of UT-A3 regulation by ST6GalI-mediated sialylation modification that may play an important role in kidney urea reabsorption and the urinary concentrating mechanism.