HMPV/RSV Co-Infection: Effects on Replication and Viral Spread

Specific Aims Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) are important respiratory viruses which cause significant morbidity and mortality, particularly in pediatric, elderly and immunocompromised patients. Newer, more sensitive molecular techniques show that patients with respiratory infections are frequently infected with more than one viral pathogen. In the case of RSV and HMPV co-infections, some studies have suggested no impact or limited impact while other research strongly indicates that RSV-HMPV co-infection has a deleterious effect on the course of disease and severity of symptoms. Thus, the impact of RSV/HMPV co-infections remains a critical area for continued study, but relatively little is known about the mechanisms by which co-infections may affect the steps of the viral lifecycle. Viral interference through triggering of innate immunity and competition for cellular resources have been studied for their roles in co-infection, and very recent work suggests that hybrid viral particles. Our preliminary studies of HMPV/RSV co-infection demonstrate that IBs in co-infected cells can contain both RSV and HMPV genomes, indicating a shared replication compartment. Our overall hypothesis is that HMPV/RSV co-infection affects both virus replication and virus spread. To test this, we will pursue two Specific Aims, using a range of experimental approaches. First, we will dissect the effect of HMPV/RSV co- infection on IB formation, dynamics and viral replication, including careful analysis of IBs over the course of infection and analysis of viral transcription and replication at the global and single cell level. Second, we will determine the effect of HMPV/RSV co-infection on potential hybrid virus particle formation and multi-virus cell- cell spread. These important experiments may elucidate new molecular consequences of viral co-infection, providing insight that may inform studies of additional respiratory viruses.