Research team finds that humans produce multiple flu strain antibodies

A U.S. research team has added to the evidence that humans can and do produce antibodies for multiple flu strains, though the method for exploiting these findings in vaccines is yet to be found.

During an H5N1 flu vaccine study, researchers tested serum samples from participants and a commercial preparation of intravenous immunoglobulin. Both cases found that there were low levels of broadly neutralizing influenza A antibodies, which included antibodies that cover both of the major influenza A groups, CIDRAP News reports.

"These data—to our knowledge, for the first time—quantitatively show the presence, albeit at low levels, of two populations of heterosubtypic BnAbs [broadly neutralizing antibodies] against influenza A in human serum,” the report said, according to CIDRAP News.

Most current flu vaccines target the head of a flu virus’s hemagglutinin protein, which evolves rapidly to the immune system. Flu vaccine researchers hope to develop a vaccine that targets a more stable region of the virus that could last years without a vaccine needing to be reformulated.

The new study suggests that broadly targeted flu antibodies are part of the normal immune response to flu. Researchers found that some participants in the study had antibodies against flu subtypes they had never been exposed to.

"We show that prevaccination serum samples have baseline heterosubtypic HA Ab [antibody] binding activity to both group 1 and 2 HA subtypes including H5 and H7, to which these subjects are most likely unexposed because of their US geographic location," the report said, according to CIDRAP News.

The study has earned praise for its findings from various researchers involved in the virology field.

"The observation that neutralizing antibodies to epitopes presenting in multiple HA subtypes…are part of the normal human immune repertoire is auspicious for universal influenza vaccine development, because it implies that broad protection may be elicited by enhancing the immunodominance of epitopes [sites] on the stem of engineered HA antigens," Ruben O. Donis and Nancy J. Cox of the Center of Disease Control and Prevention wrote in an accompanying editorial to the study, according to CIDRAP News.