Coreceptor switching in HIV-1 subtype B and subtype C

Area of Science:

• Virology
• Immunology
• Mathematical Modeling

Background:

• HIV-1 exhibits tropism for CCR5 (R5) or CXCR4 (X4) coreceptors.
• Coreceptor switching from R5 to X4 is common in HIV-1 subtype B but rare in subtype C.
• Understanding factors influencing coreceptor tropism is crucial for HIV pathogenesis and treatment.

Purpose of the Study:

• To identify key factors governing the delayed or rare coreceptor switch in HIV-1 subtype C.
• To elucidate the role of immune responses and host cell availability in HIV-1 tropism.
• To compare coreceptor switching kinetics between HIV-1 subtypes B and C.

Main Methods:

• Development and analysis of a mathematical model simulating HIV-1 infection dynamics.
• Inclusion of target cell populations (macrophages, lymphocytes) for R5 and X4 tropic viruses.
• Incorporation of lytic and non-lytic immune responses.
• Sensitivity analysis to determine critical model parameters.

Main Results:

• A persistent and efficient lytic immune response suppresses CXCR4-tropic (X4) virus, preventing phenotypic switching.
• Efficient non-lytic immune responses are less effective in preventing coreceptor switch.
• Macrophage availability and enhanced viral kinetics favor the dominance of CCR5-tropic (R5) strains.
• Model simulations predict distinct coreceptor switching patterns between HIV-1 subtypes.

Conclusions:

• Persistent, efficient lytic immunity is key to preventing X4 virus emergence in HIV-1 subtype C.
• Host environment, potentially altered by immune activation, influences differential coreceptor switching kinetics between HIV-1 subtypes.
• Mathematical modeling provides insights into complex HIV-1 dynamics and tropism determination.