By Sean Henahan, Access Excellence

Researchers at Johns Hopkins have identified a compound called hTAP(human tracheal antimicrobial peptide) that lung cells "squirt" on attacking bacteria. Significantly, studies of the lungs of patients with  lung damage from cystic fibrosis (CF) show that hTAP is disabled in these patients.

"People have always thought that the lungs only attacked infections via the classical immune system--B cells, T cells and other immune cells," says Pete Pedersen, Ph.D., Hopkins professor of biological chemistry. "But lung cells apparently have their own first-line defense mechanism--they shoot out one or more peptides that kill bacteria."

The first such compounds were identified in cells from frog skin and cow throats by researchers at other institutions Young Hee Ko, a research associate in Pedersen's lab, suspected that CF might be plugging up the "nozzle" on a similar bug spray in humans.

"That nozzle is a channel on the surface of lung cells called CFTR, and we already knew that CF disrupts it," says Ko.

Ko exposed two batches of lung cells, one from a normal patient and one from a CF patient, to Pseudomonas aeruginosa, a bacterium that causes repeated lung infections in CF patients.  The bacteria infected many CF cells while making little progress in the normal cells. Ko then searched for an antimicrobial compound similar to the one found in cow throats, and found hTAP.

Pedersen speculates that cells in other areas at high risk for infection, such as the eyes, the gut or the mouth, may secrete similar germ-fighting compounds. Because hTAP is disabled in CF patients, they have an increased vulnerability to lung infections. If  hTAP or similar compounds can be mass-produced, they may help fight lung infections in both CF patients and in the general population, where infectious lung diseases like tuberculosis kill more than 7 million people every year, said Pedersen.

The Hopkins CF studies were published recently in the journal FEBS (Federation of European Biochemical Societies) Letters.

CLONED SHEEP MILK

In related research, the British scientists who created Dolly the sheep clone announced they will begin testing a potential therapy for CF produced in the milk of genetically engineered sheep.

Twelve volunteers with CF will receive alpha-antitrypsin, a human protein produced by sheep in their milk. The researchers hope the therapy will relieve some of the debilitating symptoms of the disease by encouraging the patients' lungs to repair themselves.