THE STABILITY OF VARIOLA VIRUS PROPAGATED IN EMBRYONATED EGGS

Area of Science:

• Virology
• Immunology
• Pathogen Research

Background:

• Variola virus, the causative agent of smallpox, has a complex relationship with host species.
• Previous research explored viral adaptation through animal passage, with limited success in maintaining distinct strains.

Purpose of the Study:

• To investigate the viability and genetic stability of variola virus strains after prolonged passage in embryonated eggs and subsequent animal (rabbit testis) inoculation.
• To assess whether animal passage influences the species identity or behavior of variola virus, particularly in relation to variola-vaccinia transformation.

Main Methods:

• Serial passage of two distinct variola virus strains (Chinese and Minnesota) in embryonated eggs.
• Inoculation of established variola virus strains into rabbit testes for serial passage.
• Monitoring viral behavior and species identity throughout the passage process.

Main Results:

• A Chinese variola virus strain was successfully established and maintained for 11 passages in rabbit testes.
• Rabbit testicular passage did not induce significant alterations in the species identity of the established variola virus strain.
• A Minnesota variola virus strain, despite extensive egg passage, could not be maintained through serial testicular passage in rabbits.

Conclusions:

• Prolonged embryonated egg passage can prepare variola virus for limited adaptation to rabbit testicular tissue.
• Animal passage, specifically in rabbit testes, does not appear to alter the fundamental species identity of variola virus.
• These findings provide insights into viral adaptation and host-specific behavior, with implications for understanding variola-vaccinia virus relationships.