The Department of Microbiology and Immunology is proud to announce that Dr. Alex Kleinpeter, PhD, Assistant Professor in the Department of Microbiology and Immunology, has been awarded a research grant for his project titled: "Investigating a novel role for the C-terminus of capsid in HIV-1 maturation." This NIH award is sponsored by the University of Pittsburgh Center for HIV Protein Interactions (PCHPI) Collaboration Development Award.

Project Abstract: The pandemic caused by HIV/AIDS has caused the deaths of over 30 million people worldwide. Although currently available antiretroviral drugs are broadly effective in suppressing viral replication and preventing transmission and progression to AIDS, virologic failure due to the development of viral resistance remains a serious problem, particularly in resource-limited settings. These realities highlight the need for the continual development of novel HIV-1 inhibitors and a commitment to basic research aimed at understanding the underlying mechanisms driving HIV-1 replication. Recent years have seen a renewed appreciation for the role of the HIV-1 capsid as a key orchestrator of molecular events crucial for HIV-1 infection and replication. This escalation in our understanding of the multiple functions of the capsid has been accompanied by the development of Lenacapavir (LEN), the first capsid-targeting compound to be approved for use as an antiretroviral drug. This validation of the capsid as a target for antiretroviral development highlights the importance of elucidating the molecular mechanisms underlying its assembly and stability. The HIV-1 capsid assembles in virions and must remain stable and intact post-entry to perform its functions required for productive infection. Our recent work has resulted in the identification of a mutation in the C-terminus of the capsid protein (CA) that alters the assembly properties of CA in virions and in vitro. Notably, very little is known about the role of the C-terminus of CA in capsid assembly. Here we propose to fill this gap in knowledge by utilizing virological, biochemical, and structural approaches to determine how the CA C-terminus contributes to the assembly of the viral capsid. In Aim 1, we will propagate HIV-1 CA C-terminus mutants in T-cell lines to select for compensatory mutations and determine how HIV-1 adapts to these changes. In Aim 2, we will use in vitro assembly assays and cryo-electron microscopy and tomography (cryo-EM and cryo-ET) to evaluate the effects of CA C-terminus mutations, and the compensatory mutations identified in Aim 1 on capsid assembly and stability. These studies will define the role of the CA C-terminus in capsid assembly, structure, and function, and could inform the future development and optimization of capsid inhibitors.