Proline-Rich Hypervariable Region of Hepatitis E Virus: Arranging the Disorder

Area of Science:

• Virology
• Genetics
• Molecular Biology

Background:

• The hepatitis E virus (HEV) hypervariable region (HVR), also known as the polyproline region (PPR), exhibits significant genomic divergence.
• HEV genotype 3 (HEV-3) displays variable PPR lengths due to genetic rearrangements like insertions, duplications, and deletions.

Purpose of the Study:

• To analyze the structural variations within the PPR of HEV-3 sequences.
• To identify specific rearrangement sites, patterns, and novel genetic elements within the HEV-3 PPR.
• To investigate the impact of these variations on amino acid composition and potential functional sites.

Main Methods:

• Analysis of 723 PPR-HEV sequences, including 137 HEV-3 sequences from clinical samples via Sanger sequencing.
• Examination of eight swine stool/liver samples for HEV-3 PPR characterization.
• Comparative analysis of PPR sequences across different HEV genotypes.

Main Results:

• HEV-3 PPR contains a higher proline percentage (30.4%) compared to other genotypes.
• Specific rearrangement sites (1-14) within the HEV-3 PPR were identified, with duplications often at sites 11 and 12.
• A novel insertion homologous to apolipoprotein C1 was discovered, alongside an increased frequency of N-glycosylation sites and altered amino acid composition due to duplications.

Conclusions:

• The study details the specific structural features and variability of the HEV-3 PPR, contributing to a deeper understanding of HEV evolution.
• Identified rearrangements and novel insertions provide insights into the genetic plasticity of HEV-3.
• Findings highlight the importance of the PPR in HEV genetic diversity and potential functional implications.