The atomic resolution structures of the human immunodeficiency virus type 1 (HIV-1) Gag lattice have revealed critical molecular contacts that stabilize the HIV-1 immature particle structure and have informed HIV- 1 proteolytic cleavages and Gag lattice disassembly. In order to gain a fundamental understanding of retrovirus assembly and maturation, atomic resolution maps of immature particles for the Orthoretrovirinae are required. Here we propose a strategy, i.e., cryo-electron tomography (cryo-ET) guided single particle reconstruction (SPR), to achieve atomic resolution reconstruction maps of retrovirus immature particles. We will use human immunodeficiency virus type 2 (HIV-2) as the basis for implementation of this image processing strategy. We will then apply the method to the study of other retrovirus immature particle structures, e.g., human T-cell leukemia virus type 1 (HTLV-1), and conduct comparative studies about the conservation of key molecular interactions in HIV-1, HIV-2 and HTLV-1 Gag lattice structures. We will also apply this approach for the study of membrane anchored HIV-1 envelope protein structure. This proposed hybrid image processing method takes advantage of the strengths of both cryo-EM imaging methods (i.e. cryo-ET and SPR) and overcomes the computation challenges that each method bears when processing images of retrovirus immature particles.
Lentivirus maturation has been one major therapeutic intervention target for preventing virus infection. The atomic resolution structures of the HIV-1 Gag lattice have revealed molecular contacts critical for immature particle assembly and disassembly. A feasible computation method will allow resolving the immature particle structure at atomic resolutions for all Orthoretrovirinae, which will enhance our understanding of lentiviral maturation and inform intervention strategies.
