Developing Broadly Neutralizing MAbs for an HIV Vaccine

DESCRIPTION (provided by applicant): Eliciting broadly neutralizing antibodies to prevent HIV-1 infection from a large diversity of primary isolates is a top priority in the development of an effective HIV/AIDS vaccine. Several MAbs isolated from HIV infected humans including lgG1b12, 2G12, 2F5 and 4E10 have broad neutralizing activity, but such potent MAbs have yet to be developed in animals. The MAb 2G12 recognizes the high mannose glycans on gp120, specifically a cluster of several Manalpha1, 2-Man structures. Such terminal alpha1,2-linked mannoses on Man8 and Man9 glycans are also the high affinity binding sites for a potent inhibitor of HIV, cyanovirin-N. High mannose glycans are highly conserved on the gp120 env protein of all HIV-1 primary isolates, and are used by all tested HIV-1, HIV-2, SIV and SHIV strains to bind dendritic cells. Therefore, the high mannose glycans could be novel targets for developing broadly HIV-1 neutralizing antibodies. HYPOTHESES: Converting all of the glycans on gp120 to Man8 and Man9 will significantly increase the number of Manalpha1, 2-Man epitopes, and create a more diverse array of conformational epitopes consisting of two or more high-mannose glycans. This novel form of antigen has a greater potential to stimulate Manalpha1, 2-Man-specific antibodies. After a series of screenings, MAbs that are able to neutralize a large diversity of HIV-1 isolates will be developed. SPECIFIC AIMS: (1) Produce HIV-1 gp120s that contain mainly Man8 and Man9, confirm the type of carbohydrate and compare their antigenicity with gp120 from mammalian cells. (2) Prepare gp120-tetanus toxoid conjugates, immunize mice and screen immune sera for cross-reactive antibodies to gp120s from different subtypes, examine inhibition of gp120-DC-SIGN binding, and measure neutralizing activities. (3) Develop Manalpha1, 2-Man-specific MAbs that recognize gp120 proteins from different clades and potently neutralize a broad range of HIV-1 primary isolates. After completion of this study we will have conclusively validated the novel antigens. If successful, the antigen would be a novel HIV vaccine candidate and the MAbs would signify a milestone in HIV vaccine design. They will further lead to the development of an efficient vaccine against numerous HIV-1 primary isolates for use in the general population globally.