Bacille Calmette-Guérin (BCG) has been used effectively to protect nonspecifically against bacterial infections and neoplasms, probably by enhancement of cell-mediated immunity. It has been suggested that cell-mediated immunity plays a role in the host defense against certain viral infections. In recent in vitro studies, macrophages from animals sensitized by BCG were more effective in lowering the titer of influenza virus than were macrophages from control animals. The purpose of this study was to investigate the in vivo effectiveness of nonspecific immune stimulation with BCG on influenza virus infection in mice. Immunization with BCG resulted in significant protection of mice. Also, the local (nasal) route of immunization was more effective than the systemic (intraperitoneal) route against the intranasal inoculum of virus, a finding which suggests that important role of local immunity, i.e., either earlier stimulation of secretory antibody or nonspecific cell-mediated immunity. The time course of the resistance ot infection suggests that interferon was not the protective mechanism.

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Guinea pigs were fed a vitamin C-deficient diet and at various time periods thereafter their peritoneal cells were tested for biological activity. The serum levels of vitamin C in the deficient animals indicated a progressive state of ascorbic acid deficiency with time and this correlated well with clinical signs and symptoms of scurvy. Fewer macrophages were obtained from the peritoneal cavities of deficient animals and in structural appearance under the phase contrast and light microscope they were smaller in size. They showed no significant impairment in phagocytosis of bacterial cells. The macrophages, however, exhibited significantly reduced migration on glass as compared to the normal cells. In vitro addition of vitamin C partially reversed this reduced migration.

The effects of a live attenuated influenza vaccine and subsequent challenge with virulent influenza virus on the delayed hypersensitivity skin test, and the in vitro response of lymphocytes were evaluated. Volunteers were skin tested before and after administration of vaccine or placebo and challenge with PPD (a purified protein derivative of Mycobacterium tuberculosis ), candida, mumps, and trichophytin, and their lymphocytes were tested for [ 3 H]thymidine uptake in response to phytohemagglutin. Of eight volunteers who showed evidence of viral replication after administration of the attenuated vaccine, four had a significant diminution in their skin test response, whereas 8 of 13 volunteers infected with virulent influenza virus showed a diminution. Of the 21 volunteers who were infected with either attenuated or virulent influenza virus, 12 showed suppression of their phytohemagglutin response. None of the volunteers who were given placebo vaccine, or who showed no evidence for viral replication after immunization or challenge, had a suppression of their skin test or phytohemagglutin responses. Although most of the infected volunteers demonstrated suppression of their T-cell function, there was no evidence of a similar suppression of B-cell function.