Insights into immune evasion of human metapneumovirus: novel 180- and 111-nucleotide duplications within viral G gene throughout 2014-2017 seasons in Barcelona, Spain

BACKGROUND: Human metapneumovirus (HMPV) is an important aetiologic agent of respiratory tract infection (RTI). This study aimed to describe its genetic diversity and clinical impact in patients attended at a tertiary university hospital in Barcelona from the 2014-2015 to the 2016-2017 seasons, focusing on the emerging duplications in G gene and their structural properties. METHODS: Laboratory-confirmed HMPV were characterised based on partial-coding F and G gene sequences with MEGA.v6.0. Computational analysis of disorder propensity, aggregation propensity and glycosylation sites in viral G predicted protein sequence were carried out. Clinical data was retrospectively reviewed and further associated to virological features. RESULTS: HMPV prevalence was 3%. The 180- and 111-nucleotide duplications occurred in A2c lineage G protein increased in prevalence throughout the study, in addition to short genetic changes observed in other HMPV lineages. The A2c G protein without duplications was calculated to protrude over F protein in 23% of cases and increased to a 39% and a 46% with the 111- and 180-nucleotide duplications, respectively. Children did not seem to be more affected by these mutant viruses, but there was a strong association of these variants to LRTI in adults. DISCUSSION: HMPV presents a high genetic diversity in all lineages. Novel variants carrying duplications might present an evolutionary advantage due to an improved steric shielding, which would have been responsible for the reported increasing prevalence and the association to LRTI in adults.