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Biased Nucleotide Composition and Differential Codon Usage Pattern in HIV-1 and HIV-2
K K Vidyavijayan1, Sameer Hassan2, Lucia K Precilla1
11 Department of HIV/AIDS, National Institute for Research in Tuberculosis (ICMR) , Chennai, India .
AIDS Research and Human Retroviruses
|September 8, 2016
Summary
Human Immunodeficiency Virus type 2 (HIV-2) shows lower pathogenicity than HIV-1, potentially due to differential codon usage in viral genes like tat, influencing protein expression and disease progression.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Human Immunodeficiency Virus type 1 (HIV-1) and HIV-2 are related retroviruses with distinct pathogenicity and global distribution.
- HIV-2 infection typically presents with slower disease progression, reduced viral loads, and a lower likelihood of developing Acquired Immunodeficiency Syndrome (AIDS) compared to HIV-1.
Purpose of the Study:
- To comparatively analyze HIV-2 and HIV-1 genes and genomes.
- To investigate the role of differential codon usage in the diminished pathogenicity of HIV-2.
Main Methods:
- Comparative analysis of the effective number of codons (ENC) across nine genes of HIV-1 and HIV-2.
- Examination of GC3 composition in regulatory genes of both viral types.
- Genomic and genetic sequence comparison between HIV-1 subtypes and HIV-2.
Main Results:
- The tat gene in HIV-2 exhibited a higher ENC value than in HIV-1 tat, indicating lower tat gene expression in HIV-2.
- GC3 composition of HIV-2 regulatory genes was ≥50%, suggesting adaptation for evolutionary survival.
- Differential codon usage patterns were observed between HIV-1 and HIV-2.
Conclusions:
- Lower expression of the tat protein in HIV-2 may contribute to reduced viral load, lower viral set point, and delayed disease progression.
- Differential codon usage is hypothesized as a contributing factor to the reduced pathogenicity of HIV-2 compared to HIV-1.
- These findings offer insights into the molecular mechanisms underlying the varying virulence of HIV-1 and HIV-2.
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