On the Apr-Jun 2011 issue of The Vaccine Times we reported on a new flu shot being tested which could do away with our need for yearly flu shots. The vaccine candidate, called VAX102 is based on an antibody called F16 which can target a common protein shared by all Influenza A viruses which are the most virulent and the most prone to mutation influenza viruses.
Recently U.S. scientists are reporting the finding of a new antibody which can tackle 30 of the 36 known strains of H1N1 (a virus of the A type) flu virus. The newly discovered antibody, called CH65, can stick to the surface part of the flu virus known as hemagglutinin which mutates every season, forcing the formulation of a new vaccine every year.
It was found in cells from a human volunteer who was given the flu vaccine for 2007, said the study published in the Proceedings of the National academy of Sciences. The antibody neutralized H1N1 strains isolated as far back as 1986 covering 21+ years of antigenic drift, a remarkable feat given that current technology provides at best yearly protection. However, it failed to neutralize the most recent, 2009 pandemic strain.
We need to be careful with the reporting of this news however. Most news sources have been reporting this news as if only 36 strains of the flu virus exist of which this antibody would cover 30. In fact there are three types of influenza viruses: A, B and C. Influenza A subtypes are determined by its two surface proteins. According to Wikipedia (emphasis added):
Influenza type A viruses are categorized into subtypes based on the type of two proteins on the surface of the viral envelope:
- H = hemagglutinin, a protein that causes red blood cells to agglutinate.
- N = neuraminidase, an enzyme that cleaves the glycosidic linkages of the monosaccharide, neuraminic acid
Different influenza viruses encode for different hemagglutinin and neuraminidase proteins. For example, the H5N1 virus designates an influenza A subtype that has a type 5 hemagglutinin (H) protein and a type 1 neuraminidase (N) protein. There are 16 known types of hemagglutinin and 9 known types of neuraminidase, so, in theory, 144 different combinations of these proteins are possible.
The general categorization of flu viruses follows this template: Type->Subtype->Strain. The Types are A, B, and C. Type A has many subtypes depending on the combinations of Hemagglutinin and Neuraminidase. For example, H1N1, a.k.a. swine flu, is one such subtype, just one of the possible 144 combinations of H and N. Further, H1N1 subtype apparently has 36 known variations, or strains. Of this small subset, this new antibody can tackle 30. On the other hand, the F16 antibody discussed in the first paragraph, is reported to act against all subtypes of influenza A, which would make it a much better possibility that CH65. However, I have no access to the two studies published on VAX102, the vaccine based on the antibody F16, so given how the discovery of CH65 was reported, we will take those news reports with a grain of salt.
Influenza B and C are not categorized into subtypes. Influenza B is categorized by strains however. So as we can see, the totality of strains that can cause the flu is huge and this newly discovered antibody can only tackle a small portion of it. So while these two new discoveries might bring us a step closer to a universal flu shot, we’re still a long way from achieving that goal.