Structure and design of broadly-neutralizing antibodies against HIV

Increased vaccine tolerability and protection via NF-κB modulation

Improving adjuvant responses is a promising pathway to develop vaccines against some pathogens (e.g., HIV or dengue). One challenge in adjuvant development is modulating the inflammatory response, which can cause excess side effects, while maintaining immune activation and protection. No approved adjuvants yet have the capability to independently modulate inflammation and protection. Here, we demonstrate a method to limit inflammation while retaining and often increasing the protective responses. To accomplish this goal, we combined a partial selective nuclear factor kappa B (NF-kB) inhibitor with several current adjuvants. The resulting vaccines reduce systemic inflammation and boost protective responses. In an influenza challenge model, we demonstrate that this approach enhances protection. This method was tested across a broad range of adjuvants and antigens. We anticipate these studies will lead to an alternative approach to vaccine formulation design that may prove broadly applicable to a wide range of adjuvants and vaccines.

Conformational epitope consisting of the V3 and V4 loops as a target for potent and broad neutralization of simian immunodeficiency viruses

Inducing neutralizing antibodies (NAb) is the key to developing a protective vaccine against human immunodeficiency virus type 1 (HIV-1). To clarify the neutralization mechanism of simian immunodeficiency virus (SIV), we analyzed NAb B404, which showed potent and broad neutralizing activity against various SIV strains. In 4 SIVsmH635FC-infected macaques, B404-like antibodies using the specific VH3 gene with a long complementarity-determining region 3 loop and λ light chain were the major NAbs in terms of the number and neutralizing potency. This biased NAb induction was observed in all 4 SIVsmH635FC-infected macaques but not in 2 macaques infected with a SIV mix, suggesting that induction of B404-like NAbs depended on the inoculated virus. Analysis using Env mutants revealed that the V3 and V4 loops were critical for B404 binding. The reactivity to the B404 epitope on trimeric, but not monomeric, Env was enhanced by CD4 ligation. The B404-resistant variant, which was induced by passages with increasing concentrations of B404, accumulated amino acid substitutions in the C2 region of gp120. Molecular dynamics simulations of the gp120 outer domains indicated that the C2 mutations could effectively alter the structural dynamics of the V3/V4 loops and their neighboring regions. These results suggest that a conformational epitope consisting of the V3 and V4 loops is the target for potent and broad neutralization of SIV. Identifying the new neutralizing epitope, as well as specifying the VH3 gene used for epitope recognition, will help to develop HIV-1 vaccines.

Structural insights into key sites of vulnerability on HIV-1 Env and influenza HA

Human immunodeficiency virus-1 (HIV-1) envelope protein (Env) and influenza hemagglutinin (HA) are the surface glycoproteins responsible for viral entry into host cells, the first step in the virus life cycle necessary to initiate infection. These glycoproteins exhibit a high degree of sequence variability and glycosylation, which are used as strategies to escape host immune responses. Nonetheless, antibodies with broadly neutralizing activity against these viruses have been isolated that have managed to overcome these barriers. Here, we review recent advances in the structural characterization of these antibodies with their viral antigens that defines a few sites of vulnerability on these viral spikes. These broadly neutralizing antibodies tend to focus their recognition on the sites of similar function between the two viruses: the receptor-binding site and membrane fusion machinery. However, some sites of recognition are unique to the virus neutralized, such as the dense shield of oligomannose carbohydrates on HIV-1 Env. These observations are discussed in the context of structure-based design strategies to aid in vaccine design or development of antivirals.