Alterations in HIV-1 gp120 V3 region are necessary but not sufficient for coreceptor switching in CRF07_BC in China

Inducing CCR5Δ32/Δ32 Homozygotes in the Human Jurkat CD4+ Cell Line and Primary CD4+ Cells by CRISPR-Cas9 Genome-Editing Technology

C-C chemokine receptor type 5 (CCR5) is the main co-receptor for HIV entry into the target CD4+ cells, and homozygous CCR5Δ32/Δ32 cells are resistant to CCR5-tropic HIV infection. However, the CCR5Δ32/Δ32 homozygous donors in populations are rare. Here we developed a simple approach to induce CCR5Δ32/Δ32 homozygotes through CRISPR-Cas9 genome-editing technology. Designing a pair of single-guide RNA targeting the flank region of the CCR5Δ32 mutation locus, we applied the CRISPR-Cas9 and lentiviral packaging system to successfully convert wild-type CCR5 into CCR5Δ32/Δ32 homozygotes in the human Jurkat CD4+ cell line and primary CD4+ cells, exactly the same as the naturally occurring CCR5Δ32/Δ32 mutation. The successful rate is up to 20% in Jurkat cells but less in primary CD4+ cells. The modified CCR5Δ32/Δ32 CD4+ cells are resistant to CCR5-tropic HIV infection. Whole-genome sequencing revealed no apparent off-target sites. This approach has the promise to promote HIV/AIDS therapy from the only cured unique Berlin patient to a routine autologous cell-based therapy.

Effect of Amino Acid Substitutions Within the V3 Region of HIV-1 CRF01_AE on Interaction with CCR5-Coreceptor

Specific amino acids within the V3 loop of HIV-1 CRF01_AE envelope glycoprotein that are involved in the interaction with CCR5/CXCR4 coreceptors, are not well characterized. We generated V3 mutants using polymerase chain reaction (PCR)-based site-directed mutagenesis of HIV-1 CRF01_AE R5-env plasmids at specific positions. Mutant viruses were produced by env-pseudotyped virus assay, tested for coreceptor usage using U373.R5 and U373.X4 cells, and viral entry was assessed with luciferase activity measurement. All viruses, harboring either single or double mutations, used the CCR5 coreceptor. However, those containing a single substitution at positions 7, 11, 18, and 32 and those with mutations at positions 5/32 and 18/32 had reduced infectivity. Only virus with arginine substitution at position 11 seemed to be involved in CXCR4 coreceptor usage. Our results suggest that some V3 positions may be necessary for the binding to coreceptor, but not for the switch of coreceptor usage.

Position 22 of the V3 loop is associated with HIV infectivity

Human immunodeficiency virus subtype 1B (HIV-1B) binds to the CD4 receptor and co-receptor CCR5 or CXCR4 to enter T lymphocytes. The amino acid sequence of the HIV envelope glycoprotein V3 region determines the co-receptor tropism, thereby influencing the infectivity of the virus. Our research group previously found that the amino acid at position 22 of the V3 region may affect the infectivity of the virus, and in this study, we tested this hypothesis. We constructed pseudoviruses by changing the amino acids at position 22 of the V3 region in CCR5-tropic and CXCR4-tropic viruses and tested their infectivity. When the amino acid at V3 position 22 was altered in the CCR5- and CXCR4-tropic viruses, their ability to infect cells decreased to 20.6% and 17.14%, respectively. Therefore, we propose that residue 22 in the V3 region of subtype HIV-1B significantly influences the infectivity of the virus.