Blog

The purified, recombinant Env proteins (BG505 SOSIP.664 or FVCENV SOSIP.664) were complexed to the purified 2dCD4 proteins (2dCD4WT or 2dCD4S60C) by overnight incubation at 4C using a 3-collapse molar excess of the soluble 2dCD4 proteins. KX2-391 2HCl the presence of neutralizing antibodies against a panel of 17 pseudoviruses. Results: Both BG505 SOSIP.664-2dCD4S60C and FVCEnv SOSIP.664-2dCD4S60C elicited a potent, HIV-specific response in rabbits with antibodies having substantial potency and breadth (70.5% and 76%, respectively) when tested against a global panel of 17 pseudoviruses mainly composed of harder-to-neutralize multiple clade tier-2 pseudoviruses. Summary: BG505 SOSIP.664-2dCD4S60C and FVCEnvSOSIP.664-2dCD4S60C are highly immunogenic and elicit potent, broadly neutralizing antibodies, the extent of which has never been KX2-391 2HCl reported previously for SOSIP.664 trimers. Adding to our previous results, the ability to consistently elicit these types of potent, cross-neutralizing antibody reactions is dependent on novel epitopes exposed following a covalent binding of Env (self-employed of sequence and conformation) to 2dCD4S60C. These findings justify further expense into study exploring revised open, CD4-bound Env conformations as novel vaccine immunogens. Keywords: HIV-1 vaccine immunogens, Envelope glycoprotein trimers, Covalent complexes, Broadly neutralizing antibodies, New Zealand White colored rabbits, Immunogen design Intro The HIV/AIDS pandemic has now continued for four decades, with approximately 37. 7 million individuals living with HIV globally, and 1.5 million new infections reported in 2020 [1]. While these figures possess vastly decreased from 1997 when the new infections peaked at 2.9 million [1], a decisive halt to this spread can only be achieved with an effective prophylactic vaccine. The broad diversity of HIV-1 offers contributed to the difficulty in identifying an Env-based vaccine immunogen capable of inducing immunity against all circulating HIV-1 organizations and clades. To address viral diversity, experts have tried to design immunogens that direct the immune reactions towards regions of the viral envelope glycoprotein (Env) that are highly conserved, such as the CD4 receptor binding site (CD4bs), the gp120-gp41 interface, the V1V2 trimer apex, and the membrane proximal external region (MPER) [2]. A number of broadly neutralizing antibodies (bnAbs) that target these conserved sites have been isolated from HIV-infected individuals thereby showing the possibility of their induction in humans. However, if HIV-infected individuals develop bnAbs, it is too late to impact on disease progression. By contrast, their neutralizing potential, and their ability to protect against illness in animal challenge models has also been analyzed [3], [4], [5], providing evidence of the importance of preexisting CD3E humoral immune responses in avoiding transmission. In an effort to improve immunogens, the HIV-1 vaccine study field has made use of multiple techniques such as mutations, cleavage site disruption and the intro of trimerization domains to produce stabilized, recombinant HIV-1 Env trimers [6], [7]. This offered rise to SOSIP trimers, the 1st Env-based immunogens with antigenic and topological constructions that best symbolize the native HIV-1 virion trimeric spike [7], [8], [9]. When assessed in rabbits, the stabilized SOSIP trimers induce autologous neutralizing antibodies as well as neutralization of the more sensitive Tier-1 viruses [10]. Env trimers can be stabilized in the closed, prefusion conformation or the open, post-CD4 engaged state. These different Env conformations expose varied epitopes and ultimately effect the elicitation of neutralizing antibodies, relevant for HIV-1 vaccine design [10], [11]. Some of the broadest and most potent antibodies characterized from HIV-infected individuals target epitopes offered in the closed, prefusion conformation, when the trimer is in its quaternary fold. As a result, the majority of trimer and immunogen design attempts have been directed towards fastening the Env in the closed conformation, with studies on SOSIP trimers becoming the most advanced. However, not much study has been directed towards the use of SOSIP trimers in the CD4-bound, open conformation. It is believed that sites of vulnerability of HIV-1 may KX2-391 2HCl be contextual and that the different Env conformations (i.e., prefusion, CD4-bound intermediates, pre-hairpin intermediate, and postfusion) structurally expose different epitopes for antibodies to target [2]. The CD4-bound conformation seems to consist of less neutralization epitopes than the closed, prefusion conformation of Env, evidenced from the fewer quantity of antibodies recognized from natural illness that specifically.