Rates and dates of divergence between AIDS virus nucleotide sequences

Area of Science:

• Virology
• Molecular Evolution
• Epidemiology

Background:

• The human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS), a global pandemic.
• Understanding HIV's genetic mutation rate and spread patterns is crucial for developing effective treatments and vaccines.

Purpose of the Study:

• To develop a new model for estimating nucleotide substitution rates across the HIV genome.
• To analyze the evolutionary dynamics and historical spread of HIV.

Main Methods:

• A novel computational model was employed to estimate substitution rates in different HIV genomic regions.
• Nucleotide sequence data from HIV isolates were analyzed to infer evolutionary relationships.

Main Results:

• Nonsynonymous substitution rates varied significantly, with hypervariable envelope regions showing the highest rates (~14 x 10^-3/site/year) and capsid/reverse transcriptase regions the lowest (~1.7 x 10^-3/site/year).
• The average synonymous rate was ~10 x 10^-3/site/year, orders of magnitude higher than DNA genomes.
• Analysis suggested HIV existed in Central Africa before 1960 and spread to North America by the mid-1970s, with evidence of recombination between strains.

Conclusions:

• HIV's high mutation rate, especially in the envelope gene, drives rapid changes in viral antigenicity.
• The findings support the hypothesis that HIV originated in Central Africa and spread globally, with specific transmission routes inferred.
• The study provides critical insights into HIV evolution, aiding in the development of therapeutic and vaccine strategies.