Galveston study results in possible plague vaccines

The plague doesn’t evoke the terror it once did, but Galveston researchers concerned about potential use by terrorists and an increasing number of global cases have developed new vaccine candidates for the killer disease.

More than six centuries after the Black Death wiped out more than a third of the population of Europe, a University of Texas Medical Branch at Galveston team recently has shown that in experiments with rodents, their three vaccines effectively protected against the infection that causes the disease. Just as important, they did not cause side effects.

“If this research is borne out, a vaccine like this could negate future epidemics and pandemics,” said Ashok Chopra, a UTMB professor of microbiology and immunology and the study’s principal investigator. “Given the increasing threat, the optimal strategy for protecting people is through vaccination.”

The plague, caused by the bacterium Yersinia pestis, can be cured with antibiotics if drugs are started soon after infection. Without prompt treatment — initial symptoms can resemble the flu — it is nearly always fatal.

In an online paper last month in the journal NPJ Vaccines, Chopra’s team reported on the vaccines’ use against pneumonic plague, the most virulent type of the disease and the one that spreads through airborne transmission. Chopra said they also work against bubonic plague, the type most associated with the 14th century pandemic that killed an estimated 50 million people.

There are few thousand human plague cases reported annually around the world — only an average of seven in the U.S. — including in places, such as India and Mozambique, where it hadn’t been seen in decades. The World Health Organization has categorized Y. pestis as a re-emerging pathogen because of the increased cases.

There have been plague vaccines developed in the past, but those using a dead bacterium typically protect only against bubonic plague and those using a live bacterium that protects against pneumonic plague have generated severe side effects. Currently, there are no Food and Drug Administration-licensed plague vaccines available in the U.S

The Galveston team deleted and modified specific genes of a live bacterium so it doesn’t cause disease but still stimulates an immune response. Between 80 to 100 percent of mice and rats given two doses of the vaccines and later infected with pneumonic vaccine survived.

Chopra said the next step will be to test the vaccines in nonhuman primates, such as monkeys.