REACTIONS OF MONKEYS TO EXPERIMENTALLY INDUCED INFLUENZA VIRUS A INFECTION : AN ANALYSIS OF THE RELATIVE ROLES OF...

1. Macaca mulatta monkeys on a normal diet have proved resistant to intranasal but not to intratracheal inoculation of influenza virus. 2. Neutralizing antibodies appeared 8 to 10 days after inoculation with either living or heat-inactivated virus. The antibodies were noted to be still present as long as 9 months after infection with living virus. 3. A specific granulopenic leucopenia characteristically followed primary influenza virus inoculation, regardless of altered conditions of diet, exposure, and route of inoculation, but it was not observed in monkeys previously infected with the same virus, all of which invariably survived. 4. Nutritional deficiency and exposure to cold increased the susceptibility of monkeys on intranasal instillation of the virus; the leucopenia was profound and fatalities frequently occurred even though neutralizing humoral antibodies developed as promptly and in relatively the same titer as under optimum nutritional conditions.