By David N. Leff

Science Editor

Eight female monkeys in Sweden are testing a vaccine against urinary tract infection (UTI) in women.

Their trial, at the Karolinska Institute, in Stockholm, began last February, co-sponsored by MedImmune Inc., of Gaithersburg, Md., which developed the vaccine.

"Four of the eight monkeys are receiving the vaccine," MedImmune's director of immunology and molecular genetics, Solomon Langermann, told BioWorld Today. "All eight had UTI induced by catheterization of Escherichia coli bacteria into their urinary bladders."

E. coli wears three hats: two white, one black.

Molecular biologists know the bug best as the founding microbe of genetic engineering, and as workhorse host organism for cloning recombinant proteins.

Physiologists recognize E. coli as a major member of the bacterial flora that colonize the mammalian gut. In human intestines, one subset of the microbe is known to promote synthesis of a blood-clotting protein, vitamin K, and thought to prevent superinfection by other bacteria that might be harmful.

One way E. coli itself becomes harmful is when feces, which it populates, make their way from the gut into the urethra, and thence enter the bladder to foment UTI, a.k.a. cystitis.

This disease, though rarely fatal, is widespread among women, in whom the urethral opening is anatomically adjacent to fecal discharge.

At least one American woman in two suffers the painful burning urination of a UTI bout at least once in her life. One in 10 have three to five recurrences per year. It accounts for 7 million to 8 million doctor visits or hospitalizations annually, at a cost exceeding $1 billion.

Langermann is lead author of a paper in today's Science, dated April 25, 1997, titled "Prevention of mucosal Escherichia coli infection by FimH-adhesin-based systemic vaccination." Its senior author, molecular microbiologist Scott Hultgren, of Washington University, in St. Louis, is on MedImmune's scientific advisory board.

Like many bacteria, E. coli microbes are covered with fine fuzz, or hairs, called pili. Hultgren showed that one of the proteins at the tip of this complex structure is an adhesin. These microbial surface antigens often take the form of filamentous projections. In the case of UTI, the E. coli adhesin binds very tightly to receptors on the epithelial cells that line the bladder's interior walls. Even a flood tide of urine can't wash them loose.

By removing the FimH gene from E. coli and inoculating this mutant microbe into mouse bladders, the researchers observed "little or no microbial colonization," the Science paper reported.

"Hultgren and Staffan Normark of the Karolinska," Langermann pointed out, "had originally shown that the FimH adhesin is an independent entity from the pilus organelle, and identified the whole assembly of the proteins. What Scott Hultgren has done subsequently in terms of our collaboration," he added, "is to purify these FimH proteins and provide them to us in various forms for testing as vaccine candidates."

Those candidates come in two versions, one long, one short, both synthesized naturally by the UTI bacteria.

"The first vaccine is a complex," Langermann explained, "made up of the adhesins, purified together with chaperone proteins. These allow the adhesin to fold into the conformation it would have in the normal functional proteins."

The shorter, or truncate, vaccine, he continued, "is normally a 29-kiloDalton protein, from which the bacterium has clipped off a portion by a mechanism that is not at all understood. We recovered this shorter form from the E. coli itself. It retains the portion that's critical for the binding functions."

Besides using cultured E. coli cell lines to generate UTI, the MedImmune team also tested the effect of their vaccines against UTI challenge by clinical isolates from the urine of human patients. "Vaccinated animals exhibited a 100-fold to 1,000-fold reduction in the number of organisms recovered from the bladders as compared with . . . controls."

"In rabbits too," Langermann said, "we've shown we can get an immune response to the protein, and that the antibodies we made in these animals were also able to block binding of the bacteria to human bladder cells."

In the ongoing monkey trials, he explained, "we introduce a fairly large inoculum of bacteria in order to be able to push the vaccine studies to the extreme. Therefore, the infection will persist for a longer period of time than under natural conditions in human patients.

Monkey Outcome Decisive To IND Filing

"Right now," he said, "we have immunized the monkeys, and are looking at the antibody responses. We hope to challenge them by the end of the summer, to look at the protective ability of the vaccines.

"Pending the outcome of those studies, we will be able to evaluate which of the candidate vaccines we would like to move forward on, in terms of filing an investigational new drug application. We hope to start Phase I human trials in 1998."

But beyond UTI, MedImmune and Washington University both foresee applying their vaccine rationale to other infectious diseases, such as middle-ear infection, pneumonia, meningitis and gonorrhea.

"Most if not all bacteria," Langermann pointed out, "make these pilus proteins on their surface. So the presumption would be that you could apply the same technology, purify away the adhesin from the rest of the molecule and * assuming that it's highly conserved, as we've seen with our FimH adhesin * be able to use that as a vaccine against infection caused by a wide array of these organisms." *