Mouse model mimics real-world plague infection.

2004 APR 14 - (NewsRx.com & NewsRx.net) -- An experimental plague vaccine proved 100% effective when tested in a new mouse model for plague infection developed by scientists at Rocky Mountain Laboratories (RML), part of the National Institute of Allergy and Infectious Diseases (NIAID) of the U.S. National Institutes of Health.

The scientists developed their model to mimic the natural transmission route of bubonic plague through the bites of infected fleas. The flea-to-mouse model provides a more realistic test setting than previously used methods, enabling a better assessment of a vaccine's ability to protect against a real-world challenge.

The new report, authored by lead researcher and RML plague expert B. Joseph Hinnebusch, PhD, appears in the April 2004 edition of Infection and Immunity. Collaborators included Clayton O. Jarrett, MS, and Florent Sebbane, PhD, of RML in Hamilton, Montana; and Jeffrey J. Adamovicz, PhD, and Gerard P. Andrews, PhD, of the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), where the recombinant plague vaccine tested in the model was made.

"Replicating the natural transmission of plague from flea to host in this model is tedious and unusual work," noted NIAID Director Anthony S. Fauci, MD. "This creative approach, however, brings researchers much closer to answers to real-life questions."

In their study, the RML scientists first infected fleas by letting them feed on blood containing a virulent strain of Yersinia pestis, the bacterial agent of plague. The infected fleas then fed on 15 mice that had been inoculated with the experimental vaccine containing an adjuvant (an immune booster). For comparison, the researchers let infected fleas also feed on a second group of 15 mice that had received only the adjuvant.

Although all 15 vaccinated mice remained symptom-free even after multiple feedings by the fleas, plague occurred in 14 of the 15 mice that had received the adjuvant alone.

"This research shows that the vaccine worked in a real-world context," Hinnebusch said. "The vaccine had prior successes in rodents and nonhuman primates, but in those experiments, the animals received laboratory-grown plague bacteria and were artificially exposed to it by needle and syringe."