A group of children who had cystic fibrosis and received annual influenza vaccines developed lower cross-reactive virus-specific CD8+ T-cell responses than unvaccinated children, according to a study by Rogier Bodewes, DVM, and colleagues from the Erasmus Medical Center in Rotterdam.
The researchers collected blood samples from 14 Dutch children with cystic fibrosis who were vaccinated and from 27 healthy control children who were not vaccinated, and they tested both sets of blood samples for the presence of virus-specific killer T cells.
In unvaccinated children, the number of virus-specific T cells rises with age, whereas such an increase was absent in children vaccinated annually, the researchers said, adding that vaccination appeared to interfere with induction of such killer T cells.
“In unvaccinated children, an age-dependent increase in the frequency of virus-specific CD8 T cells, which was not observed in vaccinated children with [cystic fibrosis], was detected,” the researchers wrote. “It has been demonstrated previously that the majority of influenza A virus-specific CD8 T cells is directed to conserved viral proteins. This indicates that memory CD8 T cells provoked against seasonal influenza A viruses will cross-react with other influenza A viruses, even with those of other subtypes. Thus, vaccinated children with [cystic fibrosis] will develop lower cross-reactive virus-specific CD8 T-cell responses than unvaccinated children.”
The data suggest that although influenza vaccines are effective against seasonal influenza, vaccines could leave patients more vulnerable to novel pandemics, as induction of virus-specific killer T cells caused by childhood influenza infection may reduce morbidity and mortality rates from pandemic influenza viruses.
Referring to the paper in a press release, Bodewes said the findings “highlight the need for the development and use of universal influenza A virus vaccines for children, especially in light of the pandemic threat of avian influenza A/H5N1.”
Nonetheless, Bodewes said efforts to develop such vaccines have for several decades been stymied by the sheer complexity of targeting inner proteins.
Source: Pediatric Supersite, 7th December 2011.