HUMAN METAPNEUMOVIRUS INFECTION: IMMUNOPATHOGENESIS, COINFECTION DYNAMICS, AND ADVANCES IN VACCINE DEVELOPMENT

Human metapneumovirus (hMPV), a worldwide important respiratory pathogen that causes significant morbidity, especially a widespread problem in pediatrics, geriatrics. The hMPV has been recognized as clinically significant and the epidemiological burden of hMPV rivals the respiratory syncytial virus. Although it offers transient protection against repeated infections throughout life, it exhibits an intricate interaction with the host immune system, especially the inhibition of interferon responses, activation or suppression of both innate and adaptive immunity and overexpression of extreme inflammatory responses that cause severe disease. The virus does not induce sustainable immunity in the event of natural infection. The further complication of clinical outcomes occurs when hMPV co-infects other respiratory viruses because of immune dysregulation and viral interference. No licensed antivirals or vaccines were produced hitherto, but new technologies in molecular virology, immunopathogenesis, and vaccine systems, including live attenuated, recombinant, virus like particles, and mRNA based vaccines, hold new opportunities. This review represents a synthesis of the existing information on the immunobiology of the hMPV, the interaction of coinfection, and new preventive and curative strategies, showing some significant gaps according to which future research and the conversion of clinical practice need to be oriented.