In rheumatoid arthritis (RA), it's tough to tell foe from friend.

For starters, consider the red, hot, swollen, painful inflammation ofthose arthritic joints. Medical students memorize the cardinal signs ofinflammation by their Latin names _ rubor, calor, dolor, tumor.

It doesn't do RA sufferers much good to know that these four fiercehorsemen of their seemingly apocalyptic disease are simplyoverdoing a good thing. That is, acute inflammation is good for you.It provides early protection at the site of an infection or injury byrestricting tissue damage.

Chronic inflammation, when it attacks the synovial lining of thejoints, especially fingers, toes, arms and legs, as RA does, happensbecause the molecules that trigger inflammation don't know when tostop.

That trigger of RA's friendly fire consists of immune-systemantibodies that have forgotten how to tell "self" from "non-self"targets. That's why they are called rheumatoid factors, and why RA isan autoimmune disease.

A swarm of trigger-happy proteins called cytokines in turn activatethese rogue antibodies, mistaking them for good guys. Two of thesemolecular alleged perpetrators, in particular, interleukin 1 (IL-1) andtumor necrosis factor (TNF), have caught the attention ofimmunologists seeking ways to curb or cure the ravages ofrheumatoid arthritis.

In the U.S. alone, the Arthritis Foundation, based in Atlanta, counts2.1 million Americans afflicted with RA, two-thirds of them olderwomen.

At the University of North Carolina in Chapel Hill, microbiologistand immunologist John Schwab leads a multi-disciplinary team ofresearchers testing a novel form of gene therapy in rats, the preferredanimal model for RA.

Schwab is senior author of an interim report in the currentProceedings of the National Academy of Sciences (PNAS), datedJan. 9, 1996, and titled: "Suppression of experimental arthritis bygene transfer of interleukin 1 receptor antagonist cDNA."

When a sudden insult to the body, such as infection or injury, signalsthe immune system to take action, IL-1 is one of the molecularmessengers that carry this dispatch to start the counter-offensive.Then when the crisis is past, the cytokine's receptor antagonist _ IL-1ra _ catches up with its receptor, binds to it, and stops IL-1 in itstracks.

"That IL-1ra protein," Schwab said, "is probably functioning all thetime in the body at a very carefully regulated level, just to maintainIL-1's capacity to respond to the constant challenges the immunesystem is receiving."

It's this balancing act that goes awry in autoimmune diseases such asRA. Schwab's strategy is to plant the human gene that encodes IL-1rain the swollen joints of arthritic rats, and see if the swelling goesdown. In his PNAS-reported experiments, it did.

"We isolated synovial fibroblast cells from the inflamed rat joint," hetold BioWorld Today, "and put them in culture. Then we transfectedthose cells ex vivo with retroviral vectors containing the human IL-1ra cDNA along with a neo gene, which encodes the neomycinantibiotic resistance factor."

That neo gene, Schwab explained, enabled his group to select outthose cells that had successfully incorporated the IL-1ra gene in theirgenome, because they resisted a dose of the antibiotic.

"Then we take those synoviocytes that are actually expressing the IL-1ra protein," Schwab continued, "and inject them into two of the rats'ankle joints." Dummy vectors, containing irrelevant genes, go intothe other two limbs as controls.

"We found," his paper reported, that the gene transfer "significantlysuppressed the severity of recurrence of arthritis, as assessed bymeasuring joint swelling," and visual inspection. It "attenuated butdid not abolish erosion of cartilage and bone," which marks theprogression of crippling RA.

The transfected cells "continued to express transferred genes for atleast nine days after engraftment."

From Systemic Protein To Local Gene

Schwab undertook this gene-transfer approach after previouslytreating arthritic rats systemically with the protein that IL-1raexpresses. "It had a definite modifying effect," he observed, "but itdidn't cure them. So that is why we started this trial."

He estimates that the locally expressed IL-1ra recombinant protein"was about four orders of magnitude more therapeutically efficientthan the systemically administered protein of our previous trial."

Schwab added that "The recombinant IL-1ra protein has been used infield trials in humans, with results that are disappointing or at leastinconclusive."

He characterized as "interesting" results obtained by Immunex Corp.,of Seattle, in a 180-patient Phase II clinical trial of systemicallyadministered tumor necrosis factor receptor protein. (See BioWorldToday, Dec. 1, 1995, p. 1.)

Among the other genes for down-regulating molecules that Schwabplans to test, he said, "the obvious next one is the TNF bindingprotein gene." He envisages transferring its cDNA together with thatof IL-1ra, and opined that more than two genes at once "is almostcertainly the direction one would have to go, since no single regulatoror mediator of inflammation controls the entire process. That's forcertain."

Schwab said he is "nowhere near ready" to undertake clinical trials ofhis rat-proven gene therapy, but mentioned that "a group inPittsburgh is preparing one."

That group, at the University of Pittsburgh, is led by orthopedicsurgeon and molecular geneticist Christopher Evans. He toldBioWorld Today that he has just begun enrolling the first of ninepatients in a Phase I clinical trial "of the same IL-1ra gene thatSchwab used."

In his impending human study, Evans hopes to see "whether themethod we've developed for transferring these potentially anti-arthritic genes into the rabbit leg, which has been our model, alsoworks in humans."

Curiously, Evans saw results "similar but not identical to JohnSchwab's data. We don't see any reduction of swelling in our animalmodel, but we do see very good protection of the cartilage." n

-- David N. Leff Science Editor

(c) 1997 American Health Consultants. All rights reserved.