A new strategy to eliminate HIV-1-infected cells by unlocking the Env trimer

Project Abstract The difficulty in eliminating HIV-1-infected cells is a major roadblock in eradication strategies. This is due to several factors which includes the occlusion of vulnerable HIV-1 envelope glycoprotein (Env) epitopes that can be recognized by antibodies (Abs) capable of potent Fc-effector functions such as Antibody-Dependent Cellular Cytotoxicity (ADCC). With this application we propose to engineer Abs specific for highly conserved CD4 induced (CD4i) Env epitopes to overcome these obstacles and facilitate the elimination of HIV-1 infected cells via ADCC. Accordingly, our central hypothesis is that CD4i therapeutic Abs (tAbs) will be capable of more effective elimination of infected primary CD4+ cells in the presence of HIV+ plasma than the best in class broadly neutralizing Abs (bnAbs) and can thus be developed into a new family of tAb that will be effective in decreasing and ultimately eliminating the viral reservoir in people living with HIV-1 (PLWH). The proposed research builds upon our successful development of new Ab-CD4 hybrids from weakly neutralizing or CD4i Abs specific for the coreceptor binding site (CoRBS) or highly conserved, non-neutralizing gp120 inner domain Cluster A region. Our lead CoRBS and Cluster A Ab-CD4 hybrids efficiently eliminate cells infected with primary HIV-1 isolates both in vitro and ex vivo, demonstrating that they can circumvent the occlusion of epitopes on infected cells and virions. Furthermore, they are also able to harness the ADCC activity of Abs present in HIV+ plasma, further enhancing ADCC. Finally, an anti-Cluster A Ab-CD4 hybrid (e.g., A32-CD4) also inhibited viral rebound in hu-mice and led to a significant reduction in integrated HIV DNA in an Fc-dependent manner. In the proposed project, we will engineer Ab-CD4s of other CD4i specificities and also replace the CD4 moiety with potent small molecule CD4 mimetic compounds (CD4mc). These next generation Ab-CD4mc conjugates will efficiently sensitize HIV-1 infected cells to ADCC-mediated killing, providing a new tool to decrease the HIV-1-infected cell reservoir in PLWH. Aim 1 is designed to prepare Ab-CD4 hybrids of other CD4i specificities including the Cluster A, C11- like and the gp41 Principal Immunodominant regions. Aim 2 will develop Ab-CD4mc conjugates in which the CD4 moiety of the Ab-CD4 will be replaced by a new generation of small compound CD4mcs including BNM-III- 170 and/or more active CD4mcs. The CD4mc will be attached to the Ab through a PEG linker using a novel tRNA suppressor system. Ab-CD4/CD4mcs will be evaluated in vitro and ex-vivo for their ability to neutralize primary viruses and eliminate HIV-1-infected cells alone or synergistically with HIV+ plasma, both in vitro and ex-vivo. Aim 3 will test the capacity of the best engineered variants to reduce the size of viral reservoir in humanized mice engrafted with PBMC from PLWH. This final aim will evaluate the capacity of the most promising engineered variants to eliminate infected cells in vivo and delay viral rebound. Overall, the project will generate a new family of potent tAbs able to eliminate HIV-1 infected cells to add new weapons to the growing arsenal aimed at achieving a functional cure of HIV-1.