Quantifying differences in the tempo of human immunodeficiency virus type 1 subtype evolution.

Area of Science:

• Virology
• Evolutionary Biology
• Genetics

Background:

• High genetic diversity of Human immunodeficiency virus type 1 (HIV-1) hinders vaccine development.
• Understanding evolutionary rate differences among HIV-1 subtypes is crucial but limited.
• Key epidemic subtypes and circulating recombinant forms (CRFs) include A1, B, C, D, G, 01_AE, and 02_AG.

Purpose of the Study:

• To investigate and compare the evolutionary rates of different HIV-1 subtypes and CRFs.
• To determine the factors contributing to observed differences in evolutionary rates, including selective pressures and replication dynamics.

Main Methods:

• Analysis of pol and env gene datasets from representative HIV-1 subtype samples.
• Bayesian Markov chain Monte Carlo relaxed-clock phylogenetic analysis.
• Application of a codon model to estimate nonsynonymous (dN) and synonymous (dS) substitution rates on phylogenetic trees.

Main Results:

• Significant variations in evolutionary rates were observed among different HIV-1 subtypes and CRFs.
• Differences in both dN (selective pressure) and dS (replication dynamics) rates contribute to overall evolutionary rate variations.
• CRF02_AG and subtype G exhibited higher evolutionary rates, while subtype D showed lower dN and dS rates. Subtype G had the lowest dN/dS ratio for the env gene.

Conclusions:

• HIV-1 subtype evolutionary rates are influenced by a combination of host-imposed selective pressures and intrinsic replication dynamics.
• Specific subtypes like CRF02_AG, G, and D display distinct evolutionary patterns.
• These findings have implications for understanding HIV-1 evolution and developing targeted therapeutic and preventative strategies, including vaccines.