Estimating the stoichiometry of human immunodeficiency virus entry

Area of Science:

• Virology
• Biophysics
• Computational Biology

Background:

• Human immunodeficiency virus (HIV) entry into target cells involves envelope glycoprotein trimers interacting with CD4 and chemokine coreceptors.
• The precise number of these interactions, or the stoichiometry of entry, required for infection is not well understood.
• Previous studies used pseudotyped virions with mixed trimers to investigate entry requirements.

Purpose of the Study:

• To develop and apply mathematical models to infer the stoichiometry of HIV entry.
• To estimate the number of trimer-receptor interactions necessary for viral infection.
• To identify limitations in current knowledge and experimental approaches for determining entry stoichiometry.

Main Methods:

• Development of mathematical models to analyze in vitro infectivity assay data.
• Fitting a simple model to previously published experimental data.
• Consideration of extended models to account for data deviations.

Main Results:

• The simplest model estimated approximately eight trimer-receptor interactions for HIV entry, exceeding prior estimates.
• Extended models produced a wide range of stoichiometry estimates, from 2 to 19 interactions.
• Systematic deviations in data suggest limitations of the simplest model.

Conclusions:

• Reliable estimation of HIV entry stoichiometry is currently not feasible with existing data and models.
• Further definition of key parameters is necessary to accurately determine the stoichiometry of HIV entry.
• The study highlights the complexity of viral entry mechanisms and the need for refined modeling approaches.