Investigators at the National Institute of Allergy and Infectious Diseases (NIAID) and the National Human Genome Research Institute (NHGRI) believe they have found the key to developing a universal vaccine for influenza.
published online on July 21 by the journal Cell
, the scientists identified 3 distinct types of vaccine-induced antibodies that can neutralize diverse strains of group 1 and group 2 influenza A viruses. For this project, they examined blood samples from 6 people who had received a vaccine against H5N1 influenza and found B cells that reacted to various subtypes of influenza virus. The study subjects had been enrolled in an H5N1 DNA/MIV-prime-boost influenza vaccine trial.
According to the authors of the Cell
paper, co-crystal structures with hemagglutinin revealed that each class of antibodies used characteristic “germline genes and convergent sequence motifs to recognize overlapping epitopes in the hemagglutinin stem.” They noted that all 6 study subjects had sequences from at least 1 multi-donor class. In half the subjects, multi-donor class sequences were recovered from >40% of cross-reactive B cells.
The researchers believe these findings demonstrate that vaccination with a divergent hemagglutinin can “increase the frequency of B cells encoding broad influenza A-neutralizing antibodies,” and they propose that the sequence signature-quantified prevalence of these B cells be used as a “metric to guide universal influenza A immunization strategies.”
At present, of course, the seasonal influenza vaccine must be updated each year to accommodate for influenza virus mutation. Although influenza virus mutates significantly from year to year, it is believed that the stem region of the virus typically remains unchanged. According to the authors of the Cell
paper, this makes the stem “an ideal target for antibodies” for a universal flu vaccine. Previously, scientists had only been able to identify broadly neutralizing antibodies targeting the flu virus stem.