There are about 77 genetically distinct HRV-As, 60 HRV-Cs and 30 HRV-Bs - that's nearly 170 distinct viruses (includes serotypes and genotypes)! Imagine 170 distinct coronaviruses.
In the past they were classified by the type of cell they infected/receptor they used into major (most of them used ICAM-I as the receptor) and minor (the rest; use VLDL-R as the receptor) groups. Sequencing is the preferred method to classify them today.
The receptor for the HRV-Cs remains unknown and they do not grow in routine cell lines instead needing more advanced culture methods. Because of this, studies predating 1988 (the first published PCR primers) generally don't account for the HRV-Cs, even though they were there and causing infections.
A.Prof Eva Kathryn Miller and I recently reviewed the HRV-Cs in some detail. Around 70 distinct HRV genotypes can circulate at a single place over a year...depending on the population being studied. I and others have found that to be the case in both the community and in hospital-based populations.
A recent article from Yamaya and colleagues suggests that a mucolytic drug (stimulates surfactant production and release to help the airways clear themselves of gunk) might be of use in treating HRV infections in COPD patients at least.
Exacerbations, which are mostly due to viruses, are the main contributor to disease burden in patients suffering from COPD, as they are in those with asthma.
The drug, ambroxol hydrochloride is already thought to reduce the frequency of URT disease and may reduce ICAM-I expression. The authors tested this using a major group HRV, HRV-B14 and found reduced release of virus, ICAM-I levels and reduced viral RNA levels.
Prophylactic use may inhibit HRV-B14 infection and modulate the inflammatory response to infection. Many of the differences were moderate (mostly arithmetic rather than logarithmic), albeit statistically significant.
It would be interesting to see what effect the drug has on other major group HRVs, minor group HRVs and on the hard to culture HRV-Cs.
