The flu kills over 250,000 people every year. Flu viruses change constantly, so they can evade our immune systems, the immune systems of other host species, and the vaccines we throw at them. Each seasonal vaccine can, at best, protect only against the current circulating strain of virus—but not emerging variants. (Just so we’re clear on this, YOU SHOULD STILL GET VACCINATED. Reread the first sentence.) And we currently have no way of knowing which strain might become a pandemic, or when or where such a strain might arise.
Making a universal vaccine, or at least one that could counter more than one subtype of the virus, is a priority. Efforts thus far have failed, because most of the proteins that are conserved between the different influenza subtypes are inside the virus rather than on its surface, which typically makes them tough for antibodies to access. But researchers have recently found a way to render one vaccine protective against a number of different subtypes.
Influenza variation graphic from Russell Kightley Media
This is all very well, and a brilliant exemplification of my adage that "Hypotheses are the refuge of the small-minded", aka "Discovery trumps hypotheses every time" – BUT I have a serious problem with the reasoning for why it works that is given in the article.
Diana Gitig says:
"Rapamycin suppressed class switching, so mice that got it along with their vaccine had more IgM class antibodies, many of which tended to be less specific to HKx31. Irony number three: these less specific antibodies might not bind as strongly to the HKx31, but it is precisely this reduced affinity that may allow them to bind to the equivalent protein on other flu strains."
Um. That flies in the face of all the immunology I have imbibed since 1976, and what I have taught since 1984 or so. That is, that B cell receptor / IgM/D binding affinity starts out low, then increases by hypermutation so that the eventual class-switched antigody has high binding affinity. Along with this, specificity starts out high – the antibodies bind only a narrow range of related epitopes – and becomes wider, as increased affinity allows binding to a wider range of related sequences / structures.
Thus, the statement that "… it is precisely this reduced affinity that may allow them to bind to the equivalent protein on other flu strains" is nonsense, as far as I am concerned: it is the fact that the antibodies have INCREASED affinity, AND are multivalent IgM, that allow them not only to bind to related sequences, but increase their neutralising ability relative to the equivalent IgG/A that would result from class-switching.
Am I wrong?
See on arstechnica.com