Enhanced resistancy of thioredoxin-transgenic mice against influenza virus-induced pneumonia

Thioredoxin (TRX) is a small redox-active protein with anti-oxidant effect and redox-regulating functions. Using TRX transgenic (Tg) mice in which human TRX is overexpressed systemically under the control of beta-actin promoter, the effects of influenza virus infection were examined in TRX Tg mice and wild type C57BL/6 mice. (1) Median lethal dose (LD50) against influenza virus infection in wild-type C57BL/6 mice was 10(-5.3) dilution, while that of TRX Tg mice was 10(-4.2) dilution. Thus, TRX Tg mice were more resistant against the virus infection than wild-type mice. (2) The body weights of wild-type mice 7 days after infection with a sublethal dose of the virus (10(-6) dilution) decreased significantly, whereas those of TRX Tg mice increased slightly. (3) Histopathology of the lung at 3 weeks after sublethal infection of influenza virus showed that severe alveolar or bronchiolar destruction was observed in wild-type mice, while mild viral pneumonia was seen in the TRX Tg mice. (4) Local (IgA) and systemic (IgG) antibody productions against influenza virus hemagglutinin in mice surviving 3 weeks after infection were similar between wild-type and TRX Tg mice. These results indicate that overexpression of TRX in Tg mice suppresses the inflammatory overshoot of viral pneumonia caused by influenza virus infection, resulting in the reduction of mortality without affecting the host's systemic immune responses to the infection. TRX may play some important roles in regulating the inflammatory process in the primary host defense against infection.