Natural Killer Cells Are Dispensable for Virus Control in <i> Rag2 ^−/− </i> Mice During Primary RSV Infection

Respiratory syncytial virus (RSV) is one of the major causes of severe lower respiratory tract infections, especially in children, the elderly, and immunocompromised individuals. Complications arising from viral infections in these age groups can present therapeutic challenges, as most of these individuals have impaired adaptive immunity. Using the T- and B cell-deficient Rag2^-/- mice, the mechanisms that mediate protection in immunocompromised hosts during RSV infection can be investigated. RSV-infected Rag2^-/- mice showed no symptoms of disease or chronic inflammation in the lungs and airways despite the presence of infectious virus in their lungs several months after infection. Interestingly, Natural Killer (NK) cells, the main innate cells with anti-viral cytotoxic effector functions, were recruited 2 days earlier in the lungs of Rag2^-/- mice compared with wildtype mice, resulting in early production of IFN-γ. However, depletion of NK cells did not affect disease severity or viral load. Together, these results suggest that the NK cells are largely dispensable for virus control during primary RSV infection in Rag2^-/- mice.