The emergence of human metapneumovirus G gene duplication in hospitalized patients with respiratory tract infection, India, 2016-2018.

Background: Human metapneumovirus (HMPV) belongs to the family Pneumoviridae. It is one of the emerging respiratory viruses causing both upper and lower respiratory tract illnesses. HMPV has two genotypes: A and B. These genotypes are classified into lineage A1, A2, B1 and B2. Lineage-A2 is further classified as A2a, A2b and A2c. Similarly, B2 is classified as B2a and B2b. Studies have shown the circulation of A2b, B1 and B2 lineages in India. However, a limited amount of data is available on the current circulating genotypes of HMPV in India.

Methods: Throat swab samples positive for HMPV by real-time RT- PCR, archived at Manipal Institute of Virology as a part of a hospital-based acute febrile illness surveillance study, was used from April 2016 to August 2018 by purposive sampling method. We performed the conventional reverse transcriptase-polymerase chain reaction for twenty samples targeting the G gene and then subjected them to sequencing. Phylogenetic analysis was done using MEGA X software by the Maximum Likelihood method.

Results: All the twenty sequences belonged to the A2c subgroup. Phylogenetic analysis showed that strains from the study have genetic relation with circulating strains in Japan, China and Croatia. Seven out of the twenty sequences showed 180-nucleotide duplication and eleven sequences showed 111-nucleotide duplication. Two sequences did not show any duplications.

Conclusion: In the current study, we report that A2c is the sub-lineage in India from April 2016 to August 2018. This study is the first retrospective study reporting the circulation of the A2c sub-lineage among adults in India with 180- and 111-nucleotide duplications in the G gene of human metapneumovirus.