Speaker
Description
The measles virus, renamed Morbillivirus hominis in 2023 (Paramyxoviridae), is subjected to a global elimination program established by the World Health Organization since 2012. However, despite these efforts, two significant epidemic resurgences occurred in France (2008-2012 ; 2017-2019). Based on a rich collection of samples, this work illuminates the evolutionary dynamics of Morbillivirus hominis over thirteen years.
To achieve this, a retrospective study was conducted on a selection of 1,253 over 12,604 samples received at the French National Reference Center for measles between January 1, 2010, and December 31,2022. . Genomes were sequenced using the MiSeq (©Illumina) following an in-house library preparation protocol and were analyzed using Bayesian phylogenetics, statistical methods, as well as custom R and BASH scripts.
The analyses reveal a global substitution rate per site per year of 4,03.10-4 (HPD: 3,08.10-4 – 5,90.10-4), along with a high intra-genotypic diversity observed over the 13-year period, involving eight different genotypes. The dominant genotype from 2010 to 2012 was D4, followed by a shift in favor of D8 in 2013. Phylogenetic analyses demonstrate a gradual lineage evolution, with D8 exhibiting significant diversification and the apparent extinction of D4 in 2015. Two major D8 subclades co-circulated between 2013 and 2022. Additionally, low diversity lineages under strong selective pressure directly fueled the two recent major epidemic outbreaks in France. Indeed, all genes of the D4 genotype were under strong positive selection pressure during the 2008-2012 outbreak and just before its extinction. Regarding genotypes B3 and D8, genes involved in immune response evasion or interaction with cellular receptors were under purifying or diversifying selection pressures during the 2017-2019 outbreak, with variations observed among these two genotypes.
These results illuminate the evolutionary dynamics of the Morbillivirus hominis and the factors contributing to its resurgence, highlighting its heterogeneity with a high genotypic diversity and selection of genes involved in virus-host interactions.
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