Vaccination approaches to combat human metapneumovirus lower respiratory tract infections.

Human metapneumovirus (hMPV) was discovered in 2001 as a causative agent of respiratory disease in young children, immunocompromised individuals and the elderly. Clinical signs of hMPV infection range from mild respiratory illness to bronchiolitis and pneumonia. Two main genetic lineages of hMPV that circulate worldwide were found to be antigenically different, but antibodies against the F protein, the major determinant of protection, were shown to be cross-protective. Since the discovery of hMPV in 2001, several research groups have developed vaccine candidates that may be used to protect different risk groups against hMPV-induced respiratory disease. The studies in rodent and non-human primate models look promising, but none of the vaccine candidates has been tested yet in human volunteers. Here we give an overview of the immunogenicity and protective efficacy of a variety of live attenuated, virus vectored, inactivated virus and subunit vaccines that have been tested in animal models.