Re: SARS and AIDS: >>This is an extremely important point. Yesterday's Washington Post (http://www.washingtonpost.com/wp-dyn/articles/A50579- 2003Apr28.html) described suggestions that infants and young children do not seem to be as severely affected by SARS. Do these stories have anything in common with suspicion that SARS may also be more severely impacting Asian countries?
Distribution of a genetic polymorphism (variant R131/H131 to be specific) of the Fcgamma receptor (CD32) may have implications for disease susceptibility if cirulating IgG2 is involved. It turns out that the spike glycoprotein of some coronaviruses might in fact have such activity.
The H131/R131 polymorphism is known to be an important outcome predictor in other diseases like bacterial respiratory infections, meningococcal infection, malaria, Dengue Hemorrhagic Fever, SLE, and Kaposi sarcoma. The H131 version has a high affinity for IgG2, while the R131 version of the receptor only binds IgG2 weakly.
More importantly, the H131 version is present in 61% of ethnic Chinese, 50% of Japanese, while only 23% of Caucasians or Asian Indians have the high affinity H131 CD32 receptor.
This suggests as a working hypothesis that SARS may provoke a cascade, via CD32-binding and downstream activation of NF-kB and other inflammatory pathways. Immune suppression could reduce the number of circulating CD32+ cells. Certainly infants have lower levels and activity of CD32+ cells, since it would be counterproductive to circulating maternal antibody levels.<<
sarswatch.org |
