Phylogenetic analysis of small ruminant lentiviruses

Area of Science:

• Veterinary Virology
• Molecular Evolution
• Bioinformatics

Background:

• Small ruminant lentiviruses (SRLV) cause significant economic losses in sheep and goats.
• Understanding SRLV genetic diversity and evolution is crucial for disease control.

Purpose of the Study:

• To establish a comprehensive phylogeny of SRLV using multiple genetic fragments and phylogenetic methods.
• To investigate the evolutionary relationships and potential for cross-species transmission among SRLV strains.

Main Methods:

• Phylogenetic reconstruction using maximum likelihood, neighbor-joining, and minimum evolution techniques.
• Analysis of env, pol, gag, and LTR gene fragments.
• Estimation of phylogenetic parameters including base composition, divergence, and codon-specific substitution rates.

Main Results:

• Divergence rates varied across gene fragments, with LTR showing the highest divergence (35%).
• Evidence of both negative and positive Darwinian selection was observed in SRLV genes.
• Phylogenetic trees revealed at least six distinct clades, with no clear separation between caprine and ovine strains, indicating extensive interspecies transmission.

Conclusions:

• SRLV evolution is complex, with significant genetic exchange and cross-species transmission between sheep and goats.
• Current classification may not fully capture the evolutionary dynamics of SRLV.
• The findings highlight the epidemiological importance of SRLV interspecies transmission.