A new study has found an unexpected number of viruses and viral subtypes in patients with respiratory tract infections (RTIs). The technique used in the study may help identify new viruses associated with human diseases.
The study is published in the September 15 issue of The Journal of Infectious Diseases, now available online.
RTIs, such as the common cold, are associated with some of the most common viral infections, and increase the risk of an asthma attack in those with the condition. Fifty to 80 percent of asthma exacerbations are precipitated by viral upper RTIs, and yet these viruses are still poorly understood.
The Virochip technique, a DNA microarray or genome chip developed by researchers at the University of California, San Francisco, uses the most conserved sequences of all known viruses of humans, animals, plants, and microbes for its detection system. The new study is the first to employ this strategy to investigate the viruses associated with RTIs in people with and without asthma.
The study, conducted by Amy Kistler, PhD, and colleagues in California, Illinois, and Missouri, used several methods to test 53 asthmatic and 30 non-asthmatic adults for viruses at various stages of health. Compared to the conventional methods of viral culture and the highly sensitive polymerase chain reaction (PCR) method, the Virochip had excellent agreement in terms of identifying viral pathogens, and proved to be both highly sensitive and specific.
The method “detected remarkable and unanticipated diversity” of viruses linked with RTIs and identified “a wholly new branch of the phylogenetic tree,” for the human rhinovirus, one of the causative agents of the common cold virus, Dr. Kistler notes, showing that even with a small test group the Virochip enabled detection of new viruses that were not possible to culture. The researchers also detected 30 distinct known species of rhinoviruses and found that only one of the two coronaviruses thought to be responsible for up to 15 percent of all colds in the United States was detectable in this study population. Instead, two newly described strains of coronaviruses dominated.
These findings are particularly important given the poor understanding of the role of viral diversity in RTIs and in asthma exacerbations. As a next step, Kistler suggested that future groups use the Virochip to continue to accumulate knowledge about such viruses. “The range and depth of viral detection [using the Virochip] is significant, since gaining a comprehensive understanding of the viral pathogen diversity associated with asthma exacerbations may enable the development of specific strategies for treating or preventing asthma exacerbations caused by viral respiratory infection.”
In an accompanying editorial, James E. Gern, MD and William W. Busse, MD of the University of Wisconsin School of Medicine and Public Health agreed that the Virochip assay could prove an excellent new tool for future studies looking to detect and understand novel viruses associated with respiratory illnesses.