Resistance of mice to reinfection after E-aminocaproic acid treatment of primary influenza virus infection.

The effect of proteolysis inhibitors on the formation of resistance to virus challenge has been studied in experimental influenza of mice. E-aminocaproic acid (E-ACA) when used in the treatment of influenza decreased the virus reproduction in lungs and also enhanced the humoral immune response. The antibody titre on days 14 to 21 post infection (p.i.) was significantly higher in the treated animals. On day 30 after challenge with the homologous strain (H3N2) the virus reproduced to low levels in the lungs of untreated convalescent mice, but no virus was detected in the lungs of mice which had been treated with E-ACA during primary infection. Marked increase of the antibody level was found in such mice. Upon challenge with lethal doses of the virulent strain (H1N1), the protection was significantly higher among animals treated with E-ACA during primary infection with a sublethal virus dose. We believe that the immunomodulatory action of E-ACA may play an important role in the increased resistance to challenge exhibited by such treatment.