The Chimpanzee SIV Envelope Trimer: Structure and Deployment as an HIV Vaccine Template

Andrabi, Raiees; Pallesen, Jesper; Allen, Joel D.; Song, Ge; Zhang, Jinsong; de Val, Natalia; Gegg, Gavin; Porter, Katelyn; Su, Ching-Yao; Pauthner, Matthias; Newman, Amanda; Bouton-Verville, Hilary; Garces, Fernando; Wilson, Ian A.; Crispin, Max; Hahn, Beatrice H.; Haynes, Barton F.; Verkoczy, Laurent; Ward, Andrew B.; Burton, Dennis R.

To compare the nature of the glycan shield on SIVcpzPtt Env and HIV Env, we performed site-specific glycan analysis of the MT145K trimer. The overall oligomannose content of the MT145K trimer is similar to HIV Env (Figures 3A and 3B) (Panico et al., 2016; Pritchard et al., 2015) . However, although the distributions differ from the HIV clade A strain BG505, which is dominated by Man 9 GlcNAc 2 oligomannose-type glycans, MT145K is predominantly Man 8 GlcNAc 2 . In addition, further processing was evident in the MT145K trimer, which showed elevated Man 6-7 GlcNAc 2 structures ( Figure 3B ). The outer domain of gp120 presents a high density of oligomannose glycans that form the intrinsic mannose patch (Bonomelli et al., 2011) , which is a highly conserved feature across the two viral species. The apex of the MT145K trimer possesses oligomannose-type glycans at N160 that correspond to the trimer-associated mannose patch (TAMP) also observed on HIV Env (Behrens et al., 2017) . As for HIV, glycans at the base of the trimer at N88 and on gp41 of the MT145K trimer are extensively processed ( Figures 3A and 3C ).