Researchers have identified a bacterial protein that may be useful in creating a vaccine against Neisseria gonorrhoeae, the microbe responsible for the notorious sexually transmitted disease. A vaccine incorporating this protein protected against infection in mice.

There is currently no vaccine against gonorrhea, notes Dr. Cynthia Nau Cornelissen of the Medical College of Virginia Campus of Virginia Commonwealth University in Richmond.

Unlike its cousin N. meningitides, Nau points out, N. gonorrhoeae has no capsule, so efforts to develop a vaccine have focused on targeting the bacterium’s surface proteins.

These efforts have been hampered by the organism’s ability to rapidly vary its surface structures.

As reported in the journal Infection and Immunity, Cornelissen and her team sought to determine whether the transferrin binding proteins (Tbp), which N. gonorrhoeae uses to “hijack” its host’s iron stores, would be a feasible vaccine target. In contrast to the surface structures mentioned, Tbps do not vary much between different strains of the microbe.

The researchers administered one of two Tbp forms, either A or B, to mice and then evaluated the animals’ immune response. These proteins were given alone or coupled with a deactivated toxin designed to enhance the immune response further.

Both forms produced an immune response against N. gonorrhoeae. The bacteria-killing effects were greatest when TbpA or B was coupled with the toxin. Of the two forms, TbpA showed the strongest bacterial killing ability.

Another benefit to TbpA, Cornelissen told Reuters Health, is that it is more conserved from strain to strain than TbpB. “It might actually be the more stable target and easier to hit,” she said.

SOURCE: Infection and Immunity, July 2005.