Tracking viruses outside the respiratory tract

Vaccine and Infectious Disease Division

Tracking viruses outside the respiratory tract

Respiratory viruses can cause severe disease or even death in stem cell transplant recipients, because their immune systems are severely depressed.  While past studies, including those by VIDI scientists, have looked at the incidence rates of various respiratory viruses in this patient population, few data exist on the amount of virus present in the recipients’ lungs or detection of virus outside of the respiratory tract in the blood.  Correlating viral load with disease outcome is important in this population, as higher viral loads have been shown to predict more serious disease for other viruses, such as cytomegalovirus.  Additionally, detection of viral RNA outside of the respiratory tract may also correlate with disease severity and poor outcomes.

VIDI clinical research associate Dr. Angela Campbell, along with colleagues, including VIDI member Dr. Michael Boeckh and co-director Dr. Larry Corey, performed a study looking at the links between respiratory viral load in bronchoalveolar lavage (lung wash) sample or presence of respiratory virus RNA in serum,  and disease outcome in stem cell transplant recipients at the Hutchinson Center.  The researchers identified 104 past recipients who had had viral pneumonia following their transplants, and tested serum or lung wash samples previously donated by the patients for the presence and levels of five different viruses, including influenza and the viruses responsible for the common cold. They then looked through the patients’ medical histories to correlate their data on viruses with clinical disease.

The scientists did not find any correlation between amount of virus in lung washes and lymphopenia (low white blood cell levels), presence of other pathogens, or survival rates in the months following pneumonia.  However, they did find a significant link between presence of virus in serum samples and an increased risk of death within one month of pneumonia diagnosis.  In healthy people, respiratory viruses rarely traffic outside the lungs; their presence in the blood stream is usually a bad sign.  Of the six patients with virus present in both serum and lung wash samples, five died within one week from when the positive sample was taken. 

“The unique aspect of this paper is that we detected respiratory virus nucleic acid in the serum of patients with severe pneumonia, and no one has reported that before for most of these viruses,” Campbell said.   “As for what it means, we’re still planning to investigate that further.  It seems that our finding is associated with severe disease, and if that’s the case, it’s worth exploring because it might have important implications for treatment.”

Respiratory virus pneumonia after hematopoietic cell transplantation (HCT): associations between viral load in bronchoalveolar lavage samples, viral RNA detection in serum samples, and clinical outcomes of HCT.  Campbell AP, Chien JW, Kuypers J, Englund JA, Wald A, Guthrie KA, Corey L, Boeckh M.  J Infect Dis. 2010 May 1;201(9):1404-13.