Virus meningo-encephalitis in Austria. III. Pathogenic and immunological properties of the virus

Area of Science:

• Virology
• Neuroscience
• Epidemiology

Background:

• An epidemic of encephalomyelitis occurred in Austria.
• Two fatal human cases provided samples for virus isolation.

Purpose of the Study:

• To isolate and characterize the virus responsible for the human encephalomyelitis outbreak.
• To determine the susceptibility of different animal models to the isolated virus.
• To investigate the pathological effects and serological responses related to the virus.

Main Methods:

• Virus isolation from human central nervous system samples.
• Inoculation of various animal models (monkeys, mice, rabbits, guinea-pigs) and chick embryos.
• Pathological examination of infected tissues in monkeys.
• Detection of viraemia in experimentally infected monkeys.
• Serological tests (neutralizing and complement-fixing antibodies) on patient sera.

Main Results:

• Two virus strains were successfully isolated.
• Monkeys, mice, and chick embryos were susceptible; rabbits and guinea-pigs were refractory.
• Experimental disease in monkeys manifested as acute meningo-encephalomyelitis, primarily affecting the brain stem, cerebellum, medulla, and spinal cord.
• Discrete lesions were observed on the chorioallantoic membrane of chick embryos.
• Viraemia was present in monkeys 6-8 days prior to clinical illness.
• The virus showed a close relationship to the Russian spring-summer encephalitis virus.
• Antibodies were detected in patients' sera.

Conclusions:

• A novel virus, closely related to Russian spring-summer encephalitis virus, was identified as the causative agent of the Austrian encephalomyelitis outbreak.
• The virus exhibits neurotropic properties and causes significant pathology in susceptible animal models.
• The findings contribute to understanding the epidemiology and pathogenesis of tick-borne encephalitis viruses.