March 1, 2011

Viral Infection and Lung Disease

(Ivanhoe Newswire) -- Acute viral infection doesn't seem to be the primary cause of heightened idiopathic pulmonary fibrosis (IPF), a progressive, deadly disease resulting in thickening and scarring of the lungs, according to this study. This was a contradiction to previous research indicating viral infection does cause exacerbation of lung disease.

"The etiology of acute exacerbation of IPF remains unknown and occult viral infection has been proposed as one possible cause," Harold Collard, MD, director of the Interstitial Lung Disease Program at the University of California, San Francisco, was quoted as saying. "The results of this study suggest that the majority of cases of acute exacerbation of IPF are not due to viral infection."

Researchers enrolled 43 patients with acute exacerbation of IPF between 2206 and 2009. In addition, 69 patients with either stable IPF or acute lung injury (ALI) were enrolled as control subjects. In all cases, bronchoscopy was performed as part of patients' clinical evaluations. Lung fluid and blood samples were collected and analyzed using three separate, highly sensitive viral DNA detection techniques to test for the presence of both known and unknown viruses.
The tests revealed evidence of viral infection in 33 percent of the patients with heightened IPF, only four of whom had evidence of common respiratory viral infections. No viruses were detected in the lung fluid from stable patients.

"The presence of respiratory viral infections in these four IPF patients suggests that a small minority of acute exacerbations of IPF may be caused by occult infection with common respiratory viruses," said Dr. Collard, who is also an assistant clinical professor of medicine at UCSF.

Unexpectedly, the researchers also found lung fluid samples from 28 percent of patients in the acute exacerbation group and 24 percent in the ALI control group tested positive for torque teno virus (TTV), a common virus that usually causes no symptoms in healthy individuals and which often appears in individuals with hepatitis. TTV was not found in stable IPF controls.

Dr. Collard said the presence of TTV in the lung fluid of patients with acute exacerbation of IPF was unexpected and its significance is unclear.

"The fact that a similar percentage of lung fluid samples from patients with ALI also were TTV positive suggests, however, that the presence of this virus may be a marker of lung injury but not causative," Dr. Collard explained. "It will be important to clarify the role of TTV in acute exacerbation of IPF in future studies."

"This study uses the most current genomics-based technologies to investigate the possible infectious etiology of acute exacerbations of idiopathic pulmonary fibrosis, and the majority of cases in this study demonstrate no evidence of viral infection when subjected to these technologies," Dr. Collard said. "Future research into the etiology of acute exacerbation of IPF should confirm these findings, further investigate the role of TTV and consider other possible complications, such as aspiration, that may cause acute respiratory worsening in these patients."

SOURCE: American Journal of Respiratory and Critical Care Medicine, published online February 25, 2011