Researchers shed light on viral strains used to develop smallpox vaccine
Historically, smallpox has a 30 percent mortality rate. Survivors of smallpox lived with pox scars for the rest of their lives. Many times, doctors harmed more than helped their patients, as physicians poked patients with golden needles, bled them to remove impurities and quarantined them in overheated rooms while they suffered high fevers, among other techniques. Sometimes these treatments killed patients faster than smallpox did.
Edward Jenner, an English physician, was the first to make a smallpox vaccine using viral fluid taken from a dairymaid’s fresh pustules of cowpox. This vaccine succeeded the traditional variolation, which was more dangerous to patients. Controversy arose as some believed Jenner used a different virus in his vaccine, possibly horsepox virus. Smallpox eradication globally was achieved in 1980 using a variety of vaccinia viral strains.
To further understand the historical vaccine, scientists from Universidade Federal do Rio de Janeiro in Brazil collaborated with researchers in Germany and the U.S. to evaluate animal testing and genomic analyses with VACV-IOV, the strain of smallpox that was used in a vaccine to eliminate the virus in Brazil.
The teams cloned two of the vaccines, B141 and B388, then compared the immune response and virulence with similar VACV strains. Results suggest that these clones could not adequately protect people from smallpox.
"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,” Clarissa Damaso, who led the study, 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."