Anti-Metapneumovirus Monoclonal antibody, Clone INQW35

Human metapneumovirus (hMPV) is a newly described paramyxovirus that is an important cause of acute respiratory tract disease. We undertook to develop a small animal model of hMPV infection, pathogenesis, and protection. Hamsters, guinea pigs, cotton rats, and nine inbred strains of mice were inoculated intranasally with hMPV. The animals were sacrificed, and nasal and lung tissue virus yields were determined by plaque titration. None of the animals exhibited respiratory symptoms. The quantity of virus present in the nasal tissue ranged from 4.6 x 10(2) PFU/gram tissue (OH mice) to greater than 105 PFU/gram (hamster). The amount of virus in the lungs was considerably less than in nasal tissue in each species tested, ranging from undetectable (< 5 PFU/g; guinea pigs) to 1.8 x 10(5) PFU/gram (cotton rat). The peak virus titer in cotton rat lungs occurred on day 4 postinfection. hMPV-infected cotton rat lungs examined on day 4 postinfection exhibited histopathological changes consisting of peribronchial inflammatory infiltrates. Immunohistochemical staining detected virus only at the luminal surfaces of respiratory epithelial cells throughout the respiratory tract. hMPV-infected cotton rats mounted virus-neutralizing antibody responses and were partially protected against virus shedding and lung pathology on subsequent rechallenge with hMPV. Viral antigen was undetectable in the lungs on challenge of previously infected animals. This study demonstrates that the cotton rat is a permissive small animal model of hMPV infection that exhibits lung histopathology associated with infection and that primary infection protected animals against subsequent infection. This model will allow further in vivo studies of hMPV pathogenesis and evaluation of vaccine candidates.

Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) are paramyxoviruses that are responsible for substantial human health burden, particularly in children and the elderly. The fusion (F) glycoproteins are major targets of the neutralizing antibody response and studies have mapped dominant antigenic sites in F. Here we grafted a major neutralizing site of RSV F, recognized by the prophylactic monoclonal antibody palivizumab, onto HMPV F, generating a chimeric protein displaying epitopes of both viruses. We demonstrate that the resulting chimeric protein (RPM-1) is recognized by both anti-RSV and anti-HMPV F neutralizing antibodies indicating that it can be used to map the epitope specificity of antibodies raised against both viruses. Mice immunized with the RPM-1 chimeric antigen generate robust neutralizing antibody responses to MPV but weak or no cross-reactive recognition of RSV F, suggesting that grafting of the single palivizumab epitope stimulates a comparatively limited antibody response. The RPM-1 protein provides a new tool for characterizing the immune responses resulting from RSV and HMPV infections and provides insights into the requirements for developing a chimeric subunit vaccine that could induce robust and balanced immunity to both virus infections.