Molecular mechanism by which residues at position 481 and 546 of measles virus hemagglutinin protein define CD46 receptor binding using a molecular docking approach.

The hemagglutinin (H) protein of measles viruses (MeV) mediates binding to the cellular receptors, CD46,human signaling lymphocyte activation molecule and nectin-4. Vaccine strains primarily contain H-proteins possessing MeV-H: Y481 and can utilize CD46. Reports suggest that a single amino acid change in MeV-H at position 481 in wild type strains renders them inefficient in utilizing CD46. The in-depth molecular mechanism by which substitutions at 481 and another reported critical residue position 546 affects CD46 binding affinity however remains elusive. We used molecular docking studies of CD46 with MeV-H possessing Y481 N/D to understand the in-depth molecular mechanism involved. It was found that loss in either of the hydrogen bond (H-bond) contacts (MeV-H:481-CD46:65, MeV-H:546-CD46:63) in the central contact region prevented efficient CD46 binding. Y481 N could form the specific H-bond, while G546S H-bond could be formed only in conjunction with Y481, revealing the significance of these residues in determining CD46 receptor binding potential. Elucidating the underlying molecular mechanism of receptor usage by the MeV has implications to understanding cellular tropism, viral pathogenesis and therapy.

Global spatiotemporal transmission dynamics of measles virus clade D genotypes in the context of the measles elimination goal 2020 in India.

Measles viruses (MeV) circulating in India mainly belong to genoypes D4 and D8 of clade D. In the context of measles elimination goal 2020 in India, molecular clock and phylogeography studies would help to identify the timescales of evolution and track the transmission pathways of MeV. We used nucleoprotein gene sequences (n = 756) from GenBank, representing 86 countries (1973-2016), to study the spatiotemporal transmission dynamics of clade D. Genotype D4 was introduced into India around 1991 and genotype D8 around 1994. Recent transmissions of the D4 genotype of measles virus (MeV) were noted from India to the United States of America and East Asia region while D8 genotype importations from North America were noted in recent years.