Photo Credit – CDC PHIL
In January of 2011 we saw a report out of Emory University and the University of Chicago that found that some people infected with the 2009 H1N1 virus appeared to have developed antibodies against other flu strains as well (see H1N1 And The Road To A Universal Flu Vaccine).
An unusual and unexpected result, leading researchers to wonder if receiving the inactivated H1N1 vaccine (as opposed to being infected with the virus) produced a similar response.
Yesterday, the results of another study (from the same researcher centers) were published in PNAS that looked at the B cell responses of 24 healthy adults immunized with the inactivated pandemic 2009 H1N1 vaccine.
And much like the earlier study, they found that a majority of vaccinated subjects had produced broadly cross-reactive B cells (antibodies).
First a link to the study and abstract, followed by excerpts from the press release.
Pandemic H1N1 influenza vaccine induces a recall response in humans that favors broadly cross-reactive memory B cells
Gui-Mei Li, Christopher Chiu, Jens Wrammert, Megan McCausland, Sarah F. Andrews, Nai-Ying Zheng, Jane-Hwei Lee, Min Huang, Xinyan Qu, Srilatha Edupuganti, Mark Mulligan, Suman R. Das, Jonathan W. Yewdell, Aneesh K. Mehta, Patrick C. Wilson, and Rafi Ahmed
Public release date: 21-May-2012
Discovery brings researchers closer to goal of 'universal' flu vaccine
The pandemic 2009 H1N1 vaccine can generate antibodies in vaccinated individuals not only against the H1N1 virus, but also against other influenza virus strains including H5N1 and H3N2. This discovery adds an important new dimension to the finding last year that people infected with pandemic 2009 H1N1 virus produced high levels of antibodies that were broadly cross-reactive against a variety of flu strains.
The researchers analyzed B cell (antibody) responses in 24 healthy adults immunized with the inactivated pandemic 2009 H1N1 vaccine. Vaccination caused a rapid increase in production of monoclonal antibodies that were capable of neutralizing multiple flu strains. Three of the antibody types also were able to stick to the "stalk" region of the virus that does not change as much as other regions and thus could provide a basis for a vaccine with broader and more reliable protection.
Antibodies that are broadly reactive against multiple influenza strains are rarely seen in people after infection or vaccination with seasonal flu, the authors note. In the 24 vaccinated individuals in the current study, the majority of flu antibodies neutralized more than one influenza strain and also seemed to be the result of B-cell memory resulting from previous exposure to other flu strains.
The generation of broadly cross-reactive antibodies after either infection with, or vaccination against, the 2009 H1N1 virus is an unusual outcome and scientists are working to determine exactly why this occurred.
Although flu viruses mutate constantly, it is known that there are parts of the flu virus (notably in the `stalk’) that change little over the years and are common across multiple strains.
One of the strategies being employed in the creation of a universal vaccine is to target these stable regions of the virus, and hopefully create protection against a wide range of flu strains over multiple years with just one shot.
According to an MSNBC report, researchers involved in this study speculate that because H1N1 was such a "new" strain of flu, it forced the body to activate a rare type of B cell that produced antibodies that targeted this stable region in the `stalk’ of the virus.
While test subjects showed signs of antibody cross-reactivity against H1N1, H3N2, and even H5N1, it isn’t certain whether these antibody responses are vigorous enough to prevent infection or illness, or how long they may last.
Still, one can’t help but wonder if the relatively mild flu season of 2011-12 might not have been due - at least in part – to some lingering levels of protection derived from the 2009 H1N1 pandemic vaccine or virus.
No doubt fodder for another study as scientists continue to work to understand the mysteries of influenza.
While the goal of creating a universal flu vaccine is still a ways off, it is hoped that these latest results will one day assist in the development of that holy grail of influenza virology.