Researchers Testing 3 New Vaccines Against 'Black Death' Plague

Plague is an old disease that is still considered deadly to this day. The difference is, however, now, researchers are developing new vaccines that could possibly protect animals against the bacteria that causes the deadly plague.

According to Medical Xpress, researchers in the new study tested three vaccines that were specially created to protect people against infection from the bacteria called Yersinia pestis, which is known to cause plague. The Black Death infamy had struck fear in people in the Middle- Ages. However, the World Health Organization has categorized the bacteria-causing plague as a re-emerging pathogen because of the increasing number of human plague cases worldwide. The bacteria have been revealed to cause three different kinds of plague, bubonic, septicemic and pneumonic.

To make the vaccines, researchers from The University of Texas Medical Branch at Galveston, altered several genes of the bacteria so they won't be able to cause disease, but would most likely trigger an immune response in animals. The vaccines were specially designed to prevent people from getting infected with the bacteria that cause pneumonic plague, the most serious form of plague and the only type that spreads through airborne transmission.

For the study, mice and rats were given two doses of each of the three vaccines. The researchers then infected the animals with pneumonic plague four months (120 days) after they were vaccinated. In another experiment, it was found that between 80 and 100 percent of the animals that were vaccinated survived the plague, reported Eurekalert.  

Unfortunately, antibiotic-resistant Y. pestis strains have been separated from plague patients and can be engineered as a bioweapon, which is concerning since Y. pestis has been classified by the Centers for Disease Control and Prevention as a Tier-1 select agent. The said agents have been identified by the federal government as agents that can possibly be used in biological terrorism or warfare. The select agents that pose the greatest threat to public health and safety are labeled as Tier 1.

The new study showed that all three vaccines stimulated an immune response in the animals that was capable of protecting them from developing a pneumonic plague infection, the researchers said. Live Science recently reported that there was previously a vaccine that protected against bubonic plague (another form of plague that causes swollen lymph nodes, called buboes), but this older vaccine did not prevent pneumonic plague and was discontinued by its manufacturer, according to information about the vaccine from the U.S. Navy. 

"The optimal strategy for protecting people and animals against this deadly disease would be through vaccination, but there are no FDA-licensed plague vaccines available in the U.S.," said Ashok Chopra, UTMB professor of microbiology and immunology. "We've been working to develop a vaccine that will generate long-term immunity and protection against the plague."

Chopra also said that in addition to how well a vaccine works to protect against disease, safety is another important aspect of vaccine development. "We have shown that our mutants (versions of the bacteria) are safe vaccine candidates as our detailed analyses showed no sign of damage to bodily tissues in the vaccinated animals," he said.