Related Experiment Videos
Identification of residues in VP2 that contribute to poliovirus neutralization antigenic site 3B
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Abstract:
Amino acid substitutions were placed at residues 74, 243, and 246 in capsid protein VP2 of poliovirus serotype 1, using site-specific mutagenesis methods. The proximity of these residues to those previously identified in neutralization site 3B suggests that these residues may also contribute to neutralization site 3B and potentially be under antibody selective pressure to mutate. However, sequence analyses of independent serotype 1 isolates indicate high sequence conservation at these residues, suggesting selective pressures are present within the virus to maintain sequences within these loop regions. All viable mutants display partial or complete resistance to neutralization by the site 3B neutralizing monoclonal antibodies. Cross-neutralization data with the site-specifically generated viral mutants confirm that these residues do indeed contribute to forming neutralization site 3B and also identify the participation of a new loop region within site 3B. However, many amino acid substitutions generate nonviable virus mutants and even conservative amino acid substitutions produce growth-compromised virus mutants. These data suggest that previous definition of neutralization antigenic sites by isolation of neutralization resistant mutants favors detection of viable mutant viruses with more normal growth characteristics and is inherently biased against detection of neutralization antigenic sites formed by residues critical for other stages of virus replication.
Insights
Poliovirus capsid protein VP2 mutations reveal key residues in neutralization site 3B. Despite sequence conservation, these mutations confer antibody resistance, highlighting complex viral evolution and antigenic site identification challenges.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Neutralization antigenic sites are crucial for understanding virus-host interactions and vaccine development.
- Polio serotype 1 capsid protein VP2 contains neutralization site 3B, a target for antibodies.
- Previous studies identified some residues within neutralization site 3B.
Purpose of the Study:
- To investigate the role of residues 74, 243, and 246 in VP2 of poliovirus serotype 1 in neutralization site 3B.
- To determine if these residues are under antibody selective pressure.
- To identify new regions contributing to neutralization site 3B.
Main Methods:
- Site-specific mutagenesis was used to introduce amino acid substitutions at specific residues in VP2.
- Viable viral mutants were generated and tested for resistance to neutralization by monoclonal antibodies targeting site 3B.
- Cross-neutralization assays were performed using site-specifically generated viral mutants.
Main Results:
- All viable mutants exhibited partial or complete resistance to neutralization by site 3B monoclonal antibodies.
- Sequence analyses of poliovirus isolates showed high conservation at these residues, suggesting strong selective pressures to maintain them.
- The study confirmed the contribution of these residues to neutralization site 3B and identified a new loop region involved in this site.
- Many substitutions resulted in nonviable or growth-compromised virus mutants.
Conclusions:
- Residues 74, 243, and 246 in VP2 are critical components of poliovirus neutralization site 3B.
- Antibody selective pressure may not be the primary driver for mutations at these specific sites due to their essential role in virus viability.
- The methods used for defining antigenic sites can be biased against residues critical for other essential viral functions, potentially overlooking important antigenic regions.