Live, Attenuated Venezuelan Equine Encephalomyelitis Virus Vaccine

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Abstract
Summary During the course of a study designed to evaluate the clinical syndrome produced in man by immunization with the attenuated strain of Venezuelan equine encephalomyelitis virus, the opportunity was taken to study, in a prospective manner, whole-blood amino acids and the applicability of fluorescent-antibody techniques to the diagnosis of infection following immunization with live, viral vaccine. Twenty healthy men were immunized at 0800 hours on day 0 by subcutaneous injection; another 20, at 2000 hours. The quantity of virus utilized for immunization in both groups was 5,000 guinea-pig intraperitoneal immunizing doses50 of live, attenuated VEE virus vaccine. Whole-blood amino acids and fluorescent-antibody studies were performed upon specimens obtained at 0800 and 2000 hours daily. A significant serologic response verifying infection was demonstrated in each vaccinated man. The number immunized at 0800 hours who became ill was not statistically different from those immunized at 2000 hours. Likewise, no statistical difference was noted in the duration or severity of illness between the two groups. The normal amino-acid diurnal periodicity was changed after immunization in every man regardless of time of inoculation. This disturbed rhythm was noted on days 1 through 4 in the group inoculated at 0800 hours and on days 2 through 8 in the group immunized at 2000 hours. In addition, significant increases in proline and glutamic acid and decreases in glutamine were noted in samples obtained from men immunized at 2000 hours. The presence of fluorescing particles in white blood cells was demonstrated in 85% of those vaccinated. The presence of these particles reached a peak in specimens obtained on day 2 after immunization in the group inoculated at 0800 hours and on day 6 in the group immunized at 2000 hours. The more pronounced changes manifested by the group immunized at 2000 hours suggest that the greater or lesser effect of an infectious micro-organism upon the human host may be dependent to some degree upon the time of exposure. The significance of these findings in relation to the pathogenesis of this viral disease is discussed.