Neutralization of diverse human immunodeficiency virus type 1 variants by an anti-V3 human monoclonal antibody

Neutralization of diverse human immunodeficiency virus type 1 variants by an anti-V3 human monoclonal antibody. were observed in sc-gp140s with linkers of 6 or more residues, with a linker length of 15 residues exhibiting especially promising traits. Overall, flexible linkages between gp120 and gp41 in BG505.SOSIP can thus substitute for cleavage, and sc-gp140s that closely mimicked the vaccine-preferred mature closed state of Env could be obtained. IMPORTANCE The trimeric HIV-1 envelope glycoprotein (Env) is the sole target of virus-directed neutralizing antibody responses and a primary focus of vaccine design. Soluble mimics of Env have proven challenging to obtain and have been thought to require proteolytic cleavage into two-component subunits, gp120 and gp41, to achieve structural and antigenic mimicry of mature Env spikes on virions. Here we show that replacement of the cleavage site between gp120 and gp41 in a lead soluble gp140 construct, BG505.SOSIP, with flexible linkers can result in molecules that do not require cleavage to fold efficiently into the mature closed state. Our results provide insights into the impact of cleavage on HIV-1 Env folding. In some contexts such as genetic immunization, optimized cleavage-independent soluble gp140 constructs may have utility over the parental BG505.SOSIP, as they would not require furin cleavage to achieve mimicry of mature Env spikes on CEP33779 virions. INTRODUCTION Efforts to design an effective vaccine against HIV-1 have so far met with limited success (1, 2). With the discovery and characterization of a multitude of effective antibodies that are capable of neutralizing HIV-1 (3,C13) and that have shown substantial promise for immunotherapy and protection (14,C17), interest has focused on antibody-based vaccines (18,C20). Vaccine strategies have been based on different components or subunits of the Env glycoprotein, which is found on the surface of HIV-1 virions and is the target of broadly neutralizing antibody responses (21,C27). Env is a trimer of heterodimers, with each heterodimer consisting of a gp120 molecule and a gp41 molecule. Like other type I fusion proteins, Env requires proteolytic cleavage (specifically at the gp120-gp41 junction) to allow movement of the fusion peptide and possibly to induce rearrangements of the structure of the protein that can allow for interactions with host receptors and virus-host membrane fusion (28). The degree of structural rearrangements varies for different type I fusion proteins, ranging from, for example, rearrangements localized to the region around the cleavage site in the case of influenza virus hemagglutinin (28,C30) to major overall structural changes in the case of the fusion glycoprotein of respiratory syncytial virus (31, 32). The precise structural effects of cleavage are unclear in the case of HIV-1 Env; CEP33779 however, it has been shown that uncleaved Env binds to both poorly and broadly neutralizing antibodies, whereas fully cleaved Env preferentially binds to broadly neutralizing antibodies (33, 34). Antigenicity profiling is thus often used CEP33779 for evaluation of native spike mimicry by Env-derived constructs in HIV-1 vaccine design (35, 36). In addition to changes resulting from gp120-gp41 cleavage, the mature HIV-1 Env undergoes a number of conformational and large-scale structural changes upon interaction with its sponsor major receptor and coreceptor and in transitioning from prefusion to postfusion areas (37,C39). Because the prefusion shut conformation of mature Env, noticed before receptor relationships, exposes neutralizing but hides nonneutralizing antibody epitopes, it really is a primary focus on in current vaccine style attempts. Trimeric Env-based immunogens are of unique interest because of the potential capability to screen antibody epitopes inside a framework similar compared to that CEP33779 observed in practical Env on virions, without revealing extra nonneutralizing decoy epitopes (36, 40). Soluble gp140 substances in particular have experienced a recently Rabbit Polyclonal to KNG1 (H chain, Cleaved-Lys380) available surge in curiosity, particularly with advancements in our knowledge of Env framework in the atomic level which have allowed logical structure-based immunogen CEP33779 style (41,C43). Developing soluble gp140s that may become antigenic and structural mimics from the shut condition of mature prefusion Env, however, has tested difficult. The existing greatest soluble gp140 molecule, called BG505.SOSIP, is a derivative from the clade A HIV-1 stress BG505, with several stabilizing mutations that enable proper structural and antigenic mimicry from the closed condition of mature prefusion Env (35, 36, 44, 45). Particularly, BG505.SOSIP.