Introducing a Weaker Strain

The Black Death, a killer disease that wiped out nearly a third of the population of 14th century Europe, has recently been re-emerging. Cases of the plague have been reported from the USA, Peru, and Africa. The Journal of Infectious Diseases & Preventive Medicine writes that there are about 1,000 to 2,000 cases of the plague reported each year to the World Health Organization.

Developments from researchers from The University of Texas Medical Branch at Galveston bring forth new potential vaccines to protect against the plague, as reported in NPJ Vaccines.

A team of microbiology and immunology experts modified genes of the Yersinia pestis, the bacteria responsible for the plague, in order to construct a weaker strain that can be introduced to patients to build up their resistance to the bacteria. Three vaccines were developed and tested to trigger an immune response in animals against the pneumonic strain of Y. pestis, the airborne form of the plague and the most dangerous.

Mice were given two doses each of the three vaccines. Four months after vaccination, they were infected with pneumonic plague. All vaccines effected long-lasting immune responses that allowed the mice to survive the plague.

Concerns of Safety

Y. pestis has been classified by the Centers for Disease Control and Prevention as a Tier-1 select agent. This indicates that the bacteria poses the greatest threat to public health and safety. Concerns have been brought up that when the antibiotic-resistant bacteria strain is separated from plague patients, it can be engineered as a bioweapon.

Ashok Chopra, UTMB professor of microbiology and immunology claimed that there were no adverse side-effects with the vaccine. "In addition to how well a vaccine works to protect against disease, safety is another important aspect for vaccine development," said Chopra. "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."

While the natural world is every changing in many respects, for better or worse, some things never do. A disease that literally plagued the world centuries ago is continuing to do damage. Thankfully, humans have evolved to be capable of science. It is amazing to see the difference medical science had made, even if we're just looking at this one disease.

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