BK virus antigenic variants: sequence analysis within the capsid VP1 epitope

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• BK virus (BKV) is a human polyomavirus.
• The VP1 gene encodes the major capsid protein, influencing BKV's antigenic properties and variability.
• Antigenic variability among BKV isolates complicates classification and understanding of immune responses.

Purpose of the Study:

• To determine the DNA sequences of the VP1 gene for seven BKV isolates.
• To correlate VP1 sequence variations with previously established antigenic groupings of BKV.
• To identify specific regions within the VP1 protein responsible for serotypic differences.

Main Methods:

• DNA sequencing of the VP1 gene from seven BKV isolates.
• Analysis of sequence differences and comparison with haemagglutination inhibition typing data.
• Amino acid sequence analysis, including hydropathy plots, focusing on specific residue clusters.
• Examination of sequence identity within the critical region across multiple clones from a single isolate.

Main Results:

• VP1 gene sequence differences were observed among BKV isolates, correlating with four distinct antigenic groups.
• Amino acid alterations were concentrated in residues 61 to 83, with each antigenic group exhibiting a characteristic sequence in this region.
• Despite minor variations in restriction enzyme digestion patterns, clones from a single isolate showed identical sequences between residues 61 and 83.
• Hydropathy plot analysis identified two highly antigenic hydrophilic regions, with residues 61-83 corresponding to one of these.

Conclusions:

• The VP1 gene sequences of BKV isolates exhibit variations that define antigenic groups.
• Residues 61 to 83 of the VP1 protein contain characteristic amino acid sequences specific to each antigenic group.
• This region (residues 61-83) is postulated to be the primary epitope responsible for the serotypic diversity observed among BK virus isolates.