Fruit flies show salmonella process

Atlanta -- U.S. scientists say they have used a transgenic fruit fly model to track how salmonella bacteria escape multiple immune responses to cause infection.

Emory University researchers used drosophila to test a group of "effector proteins," also known as "virulence factors," secreted by invading organisms to usurp the host immune response for their own benefit.

They said they found one protein, AvrA, not only shuts down the key immune signaling pathways JNK and NF-kB, but also turns off the fail-safe system organisms that respond to irreversible threats. That defense, called apoptosis, eliminates invaders along with the infected cells through a system of programmed cell death.

Using a mouse model of salmonella infection, they discovered AvrA suppressed the same immune signaling pathways and apoptotic reaction as in the drosophila model, said Dr. Andrew Neish, a professor of pathology and the study's lead scientist. A mutant form of the salmonella-lacking AvrA caused an enhanced inflammatory immune response and markedly more cell death in the mouse intestine.

The details of the study that included Assistant Professor Kenneth Moberg, Kevin Moses, Rheinallt Jones, Huixia Wu, Christy Wentworth, Liping Luo and Lauren Collier-Hyams are reported in the journal Cell Host & Microbe.

Copyright 2008 by United Press International.