Why do we get repeated colds?
Although a number of different viruses cause “colds”, rhinoviruses are one of the most frequent sources. And although there are many serotypes of rhinovirus, they total number may not be enough to account for all the colds you get during your lifetime. A recent paper suggests that rhinoviruses are able to direct antibody responses away from the critical areas on the outside of the virus particle which give a neutralizing response towards internal regoins of the virus capsid not exposed to antibodies.
Misdirected antibody responses against an N-terminal epitope on human rhinovirus VP1 as explanation for recurrent RV infections. (2012) FASEB J. 26(3): 1001-1008
Rhinoviruses (RVs) are the primary cause of upper respiratory tract infections, generally known as the common cold. Moreover, RV infections can trigger severe exacerbations of asthma and chronic obstructive pulmonary disease (COPD). We expressed the 4 major RV capsid proteins, VP1-VP4, in Escherichia coli and used these proteins as well as recombinant and synthetic VP1 fragments to study and map antibody responses in RV-infected humans. VP1, which on infection binds to ICAM 1, was identified as a major target for the memory immune response, residing in the IgG1 subclass and IgA class. Interestingly, this response was mainly directed against an N-terminal 20mer peptide in VP1, P1a, which becomes exposed on intact RV only when it docks to its receptor ICAM 1. Molecular modeling using the 3-dimensional RV capsid structures revealed that P1a was localized inside the capsid and outside the areas involved in receptor binding or RV neutralization. Our results suggest misdirection of antibody responses against a nonprotective epitope as a mechanism how RV escapes immunity and causes recurrent infections. Based on these findings, it may be possible to design vaccines against RV infections and RV-induced respiratory diseases.