We conducted studies with mice, rats, and monkeys which demonstrated the ability of glucan to induce either nonspecific or specific enhancement of host resistance to infectious diseases. Intravenous pretreatment of mice with glucan significantly enhanced the survival of mice challenged with either Venezuelan equine encephalomyelitis (VEE) virus or Rift Valley fever virus. Pretreatment was beneficial when initiated 3 days before challenge with VEE virus and 7 days before challenge with Rift Valley fever virus. Treatment of mice after VEE challenge did not increase their survival compared with controls. Glucan pretreatment of rats provided increased resistance to both intraperitoneal and low-dose aerosol challenges with virulent Francisella tularensis when the glucan was given intravenously, but not when it was administered intranasally. In contrast, intranasal glucan pretreatment enhanced the survival of mice when they were challenged by aerosol with Pseudomonas pseudomallei, whereas intravenous glucan pretreatment did not increase survival. mice given glucan combined with a marginally immunogenic dose of VEE vaccine were more resistant to homologous virus challenge than were mice given either Freund complete adjuvant plus vaccine or vaccine alone. Similarly, both primary and secondary VEE antibody titers in cynomolgus monkeys given glucan with VEE vaccine were significantly greater than titers in vaccine controls.

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Two groups of rhesus monkeys were inoculated with either 10(5) (group 1) or 10(3) (group 2) plaque-forming units of Machupo virus, the etiologic virus of Bolivian hemorrhagic fever. The monkeys were observed for clinical signs; body temperatures, viremias, hematologic changes, and virus-neutralizing antibody were measured. The onset of clinical signs for groups 1 and 2 occurred on days 4-6 and 7-10, respectively, with fever, anorexia, and depression. These and other signs became more severe, and all of the monkeys died; the respective mean times to death for groups 1 and 2 were 14.3 and 19.5 days. Hematocrit, neutrophil, and lymphocyte values decreased in both groups until a few days before death and then increased slightly. Viremias in the two groups peaked on days 13 and 16, respectively, and persisted until death; the sole exception was one monkey in group 2 that developed neutralizing antibody by day 21. The response of the rhesus monkey to Machupo virus thus provides a useful model for the study of Bolivian hemorrhagic fever.

A subhuman primate model was developed for study of the pathogenesis of infection with Coxiella burnetii. Cynomolgus monkeys (Macaca fascicularis) that were exposed to 10(5) mouse median infectious intraperitoneal doses of C. burnetii in a small-particle aerosol developed clinical signs of illness and pathologic changes characteristic of Q fever infection in humans. All monkeys had radiologic evidence of pneumonia by day 9. Antibodies to C. burnetii were detectable by the indirect fluorescent antibody test by day 7. These data indicate that the cynomolgus monkey is a suitable model for study of the pathogenesis of Q fever infection and may prove valuable in the evaluation of C. burnetii vaccines.

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