Reduced protection of RIPK3-deficient mice against influenza by matrix protein 2 ectodomain targeted active and passive vaccination strategies

RIPK3 partially protects against disease caused by influenza A virus (IAV) infection in the mouse model. Here, we compared the immune protection of active vaccination with a universal influenza A vaccine candidate based on the matrix protein 2 ectodomain (M2e) and of passive immunization with anti-M2e IgG antibodies in wild type and Ripk3(-/-) mice. We observed that the protection against IAV after active vaccination with M2e viral antigen is lost in Ripk3(-/-) mice. Interestingly, M2e-specific serum IgG levels induced by M2e vaccination were not significantly different between wild type and Ripk3(-/-) vaccinated mice demonstrating that the at least the humoral immune response was not affected by the absence of RIPK3 during active vaccination. Moreover, following IAV challenge, lungs of M2e vaccinated Ripk3(-/-)mice revealed a decreased number of immune cell infiltrates and an increased accumulation of dead cells, suggesting that phagocytosis could be reduced in Ripk3(-/-) mice. However, neither efferocytosis nor antibody-dependent phagocytosis were affected in macrophages isolated from Ripk3(-/-) mice. Likewise following IAV infection of Ripk3(-/-) mice, active vaccination and infection resulted in decreased presence of CD8+ T-cells in the lung. However, it is unclear whether this reflects a deficiency in vaccination or an inability following infection. Finally, passively transferred anti-M2e monoclonal antibodies at higher dose than littermate wild type mice completely protected Ripk3(-/-) mice against an otherwise lethal IAV infection, demonstrating that the increased sensitivity of Ripk3(-/-) mice could be overcome by increased antibodies. Therefore we conclude that passive immunization strategies with monoclonal antibody could be useful for individuals with reduced IAV vaccine efficacy or increased IAV sensitivity, such as may be expected in patients treated with future anti-inflammatory therapeutics for chronic inflammatory diseases such as RIPK inhibitors.

Automated summary

RIPK3 partially protects against disease caused by influenza A virus infection in mice. Active vaccination with M2e viral antigen provides protection against IAV, but this protection is lost in Ripk3(-/-) mice.