Serotypic evolution of measles virus is constrained by multiple co-dominant B cell epitopes on its surface...

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Measles virus (MeV) remains a global health concern despite widespread vaccination efforts.
• The emergence of MeV genotypes capable of evading vaccine-induced immunity has not been observed.
• Understanding the evolutionary constraints on MeV is crucial for predicting its future behavior.

Purpose of the Study:

• To investigate the evolutionary constraints on measles virus (MeV) hemagglutinin (H) glycoprotein.
• To determine the impact of mutations on MeV's ability to evade serum neutralization.
• To assess the likelihood of MeV evolving to escape vaccine-induced immunity.

Main Methods:

• Systematic introduction of mutations into the H glycoprotein of an attenuated MeV strain.
• Assaying serum neutralization of mutant MeV strains.
• Analyzing the role of co-dominant antigenic sites on the H glycoprotein.
• Identifying critical binding sites for SLAMF1 and nectin-4 receptors.

Main Results:

• The MeV H glycoprotein possesses numerous co-dominant antigenic sites that severely constrain virus evolution.
• Some antigenic sites are critical for binding to the SLAMF1 and nectin-4 receptors.
• Protective neutralizing antibodies in serum target co-dominant fusion (F) glycoprotein epitopes.
• Mutant MeV viruses retaining even one co-dominant antigenic site showed minimal reduction in serum neutralization.

Conclusions:

• The extensive network of co-dominant antigenic sites on the MeV H and F glycoproteins significantly limits its evolutionary potential.
• The inability of MeV to readily evolve escape mutants suggests a low likelihood of pathogenic measles virus emerging that can evade vaccine-induced immunity.
• Current vaccination strategies remain robust against measles virus immune escape.