During HIV-1 infection, the envelope protein (Env) is presented to the immune system in many forms. In the currently accepted model, the functional form of Env is a trimeric complex of gp120/gp41 heterodimers. Examples of non-functional forms of Env include monomeric gp120, uncleaved gp160 precursor and gp41 from which gp120 has dissociated. The functional trimer has evolved to be a compact structure; indeed, while most monoclonal antibodies (mAbs) recognize only non-functional forms of Env, neutralizing mAbs appear to also bind the functional Env trimer. Env fragments released from particles and infected cells have been considered responsible for the generally poor quality neutralizing response to HIV-1 infection. However, new evidence suggests that infectious HIV-1 particles also bear non-functional forms of Env. In pursuing the goal of developing an HIV-1 vaccine able to elicit potent neutralizing antibodies, we have chosen HIV-1 pseudovirions as model immunogens.
In Specific Aim 1, we will use a comprehensive set of techniques in an attempt to generate pseudovirions that exclusively bear functional trimers that are only recognized by neutralizing mAbs. Given the compact, antibody-resistant nature of the trimeric complex, we will expand our studies in Specific Aim 2 to include the receptor-engaged form of Env as an alternative neutralization target. Env-receptor binding induces exposure of otherwise cryptic structures. Although these structures are only transiently exposed in natural infection, they are plausible neutralization targets recognized by well-characterized neutralizing mAbs, exemplified by 2F5. To this end, we have generated a pseudovirion mutant that attaches to susceptible cells but only fuses in a redox-dependent manner. Using this model, we will investigate post-attachment neutralization in HIV-I+ serum.
In Specific Aim 3, we will test the immunogenicity of i) pseudovirions bearing only functional trimers and ii) receptor-engaged pseudovirions attached to autologous macaque lymphocytes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI058763-02
Application #
6889527
Study Section
AIDS Immunology and Pathogenesis Study Section (AIP)
Program Officer
Ahlers, Jeffrey D
Project Start
2004-05-01
Project End
2008-04-30
Budget Start
2005-05-01
Budget End
2006-04-30
Support Year
2
Fiscal Year
2005
Total Cost
$454,680
Indirect Cost
Name
Torrey Pines Institute for Molecular Studies
Department
Type
DUNS #
605758754
City
Port St. Lucie
State
FL
Country
United States
Zip Code
34987
Crooks, Ema T; Osawa, Keiko; Tong, Tommy et al. (2017) Effects of partially dismantling the CD4 binding site glycan fence of HIV-1 Envelope glycoprotein trimers on neutralizing antibody induction. Virology 505:193-209
Crooks, Ema T; Tong, Tommy; Chakrabarti, Bimal et al. (2015) Vaccine-Elicited Tier 2 HIV-1 Neutralizing Antibodies Bind to Quaternary Epitopes Involving Glycan-Deficient Patches Proximal to the CD4 Binding Site. PLoS Pathog 11:e1004932
Tong, Tommy; Crooks, Ema T; Osawa, Keiko et al. (2014) Multi-parameter exploration of HIV-1 virus-like particles as neutralizing antibody immunogens in guinea pigs, rabbits and macaques. Virology 456-457:55-69
Tong, Tommy; Crooks, Ema T; Osawa, Keiko et al. (2014) Multi-Parameter Exploration of HIV-1 Virus-Like Particles as Neutralizing Antibody Immunogens in Guinea Pigs, Rabbits and Macaques. Virology 456-457:55-69
Gach, Johannes S; Quendler, Heribert; Tong, Tommy et al. (2013) A human antibody to the CD4 binding site of gp120 capable of highly potent but sporadic cross clade neutralization of primary HIV-1. PLoS One 8:e72054
Tong, Tommy; Osawa, Keiko; Robinson, James E et al. (2013) Topological analysis of HIV-1 glycoproteins expressed in situ on virus surfaces reveals tighter packing but greater conformational flexibility than for soluble gp120. J Virol 87:9233-49
Tong, Tommy; Crooks, Ema T; Osawa, Keiko et al. (2012) HIV-1 virus-like particles bearing pure env trimers expose neutralizing epitopes but occlude nonneutralizing epitopes. J Virol 86:3574-87
Melchers, Mark; Bontjer, Ilja; Tong, Tommy et al. (2012) Targeting HIV-1 envelope glycoprotein trimers to B cells by using APRIL improves antibody responses. J Virol 86:2488-500
Crooks, Ema T; Tong, Tommy; Osawa, Keiko et al. (2011) Enzyme digests eliminate nonfunctional Env from HIV-1 particle surfaces, leaving native Env trimers intact and viral infectivity unaffected. J Virol 85:5825-39
Binley, James M; Ban, Yih-En Andrew; Crooks, Emma T et al. (2010) Role of complex carbohydrates in human immunodeficiency virus type 1 infection and resistance to antibody neutralization. J Virol 84:5637-55

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