Historical vaccine research sheds light on smallpox
The researchers used two clones of VACV-IOC, the smallpox vaccine strain used to eradicate smallpox in Brazil, and compared their virulence and immune response to other VACV strains, including ACAM2000, the second-generation vaccine currently produced in the U.S.
A better understanding of how the strains relate to each other will facilitate the development of updated smallpox vaccines, which are necessary due to the rising concern of the smallpox virus being weaponized.
Conflicting information about the origin of the original smallpox vaccine exists; however, using data from the study and historical accounts, the researchers were able to determine that the VACV-IOC strain is related to Cantagalo virus (CTGV), a vaccinia strain that infects dairy cattle and milkers in Brazil.
"Our historical research indicates that the CTGV virus is a feral VACV strain that escaped to nature from a sample imported from France to Rio de Janeiro in 1887, known as the Beaugency strain," Lead Researcher Clarissa Damaso, of the Universidade Federal do Rio de Janeiro in Brazil, said. "We found historical records on vaccinated cows in Rio de Janeiro that were transported everywhere in the country, which may have created the opportunity for the virus to escape to nature. Also, records from the beginning of the 20th century report on the transmission of the vaccinia virus in dairy cattle from vaccinees."
Full details of the study will be released in the October issue of the Journal of Virology.