Breadth of Neutralizing Antibodies Elicited by Stable, Homogeneous Clade A and Clade C HIV-1 gp140 Envelope Trimers in Guinea Pigs

Abstract

The native envelope (Env) spike on the surface of human immunodeficiency virus type 1 (HIV-1) is trimeric, and thus trimeric Env vaccine immunogens are currently being explored in preclinical immunogenicity studies. Key challenges have included the production and purification of biochemically homogeneous and stable trimers and the evaluation of these immunogens utilizing standardized virus panels for neutralization assays. Here we report the binding and neutralizing antibody (NAb) responses elicited by clade A (92UG037.8) and clade C (CZA97.012) Env gp140 trimer immunogens in guinea pigs. These trimers have been selected and engineered for optimal biochemical stability and have defined antigenic properties. Purified gp140 trimers with Ribi adjuvant elicited potent, cross-clade NAb responses against tier 1 viruses as well as detectable but low-titer NAb responses against select tier 2 viruses from clades A, B, and C. In particular, the clade C trimer elicited NAbs that neutralized 27%, 20%, and 47% of tier 2 viruses from clades A, B, and C, respectively. Heterologous DNA prime, protein boost as well as DNA prime, recombinant adenovirus boost regimens expressing these antigens, however, did not result in an increased magnitude or breadth of NAb responses in this system. These data demonstrate the immunogenicity of stable, homogeneous clade A and clade C gp140 trimers and exemplify the utility of standardized tier 1 and tier 2 virus panels for assessing the NAb responses of candidate HIV-1 Env immunogens.The development and evaluation of novel HIV-1 Env immunogens are critical priorities of the HIV-1 vaccine field (2, 10, 25). The major antigenic target for neutralizing antibodies (NAbs) is the trimeric Env glycoprotein on the virion surface (4, 18, 30). Monomeric gp120 immunogens have not elicited broadly reactive NAbs in animal models (5, 13, 28, 29) or humans (16, 31), and thus several groups have focused on generating trimer immunogens that better mimic the native Env spike found on virions (3,7,14,15,20,22,27). It has, however, proven difficult to produce stable and conformationally homogeneous Env trimers. Strategies to modify Env immunogens have therefore been explored, including the removal of the cleavage site between gp120 and gp41 (3,7,23,39,40), the incorporation of an intramolecular disulfide bond to stabilize cleaved gp120 and gp41 moieties (6), and the addition of trimerization motifs such as the T4 bacteriophage fibritin "fold-on" (Fd) domain (8,17,39).Preclinical evaluation of candidate Env immunogens is critical for concept testing and for the prioritization of vaccine candidates. Luciferase-based virus neutralization assays with TZM.bl cells (21, 24) have been developed as high-throughput assays that can be standardized (26). However, the optimal use of this assay requires the generation of standardized virus panels derived from multiple clades that reflect both easy-to-neutralize (tier 1) and primary isolate (tier 2) viruses (21, 24). A tiered approach for the evaluation of novel Env immunogens ...

Influences on the Design and Purification of Soluble, Recombinant Native-Like HIV-1 Envelope Glycoprotein Trimers

“…1. The CZA97.012 and 92UG037.8 env gene sequences and plasmids expressing the gp140 UNC -Fd-His proteins were obtained from B. Chen (Harvard University) and are the basis of the uncleaved gp140 proteins described in multiple publications (2,4,34,42,43). In some reports, the same genes or proteins have sometimes been referred to as C97ZA012, 97ZA012, UG037, UG37, etc.…”

“…Often, a trimerization domain is added to the C terminus of gp41 ECTO , most commonly a Foldon (Fd) moiety (2,4,14,15,(30)(31)(32)(33)(34). The resulting uncleaved gp140 (gp140 UNC ) proteins can be purified as entities that contain three gp120 subunits and three gp41 ECTO subunits (2,4,14,15,(32)(33)(34)(35)(36). However, a variety of assays show that these gp140 UNC proteins do not adopt or retain a native-like structure (19,30,33,(37)(38)(39).…”

“…An alternative approach widely used over the past 20 years has been to eliminate the natural cleavage site between gp120 and gp41 ECTO , such that the two subunits remain covalently linked. Often, a trimerization domain is added to the C terminus of gp41 ECTO , most commonly a Foldon (Fd) moiety (2,4,14,15,(30)(31)(32)(33)(34). The resulting uncleaved gp140 (gp140 UNC ) proteins can be purified as entities that contain three gp120 subunits and three gp41 ECTO subunits (2,4,14,15,(32)(33)(34)(35)(36).…”

Broad Neutralizing Antibodies to HIV Env and Other Complex Viral Antigens from Vaccinated Cows

“…Our experience with HIV Env antibodies suggests potent neutralizing IgG antibodies required a relatively long maturation time when produced by pregnant cows [40]. Furthermore, the large body mass of the cows may require much more vaccine compared to other animals [40,[100][101][102]. Additionally, highest concentrations of colostrum antibody are found in the first colostrum and this must be collected immediately after the unpredictable event of calving.…”

Immunotherapies and Vaccines

“…The HIV envelope is trimeric on the surface of the virus particle. Studies using trimeric envelope immunogens have been used to improve the humoral responses (Nkolola, Peng et al 2010;Sundling, Forsell et al 2010;Sundling, O'Dell et al 2010). Also, the recent vaccine trial in Thailand, has provided some data to support the possibility that humoral responses may be the HIV correlate of protection (Rerks-Ngarm, Pitisuttithum et al 2009).…”