Rapid cloning of high-affinity human monoclonal antibodies against influenza virus

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Abstract
The use of antibody therapy has been limited in part because fully human monoclonal antibodies (mAbs) targeting specific antigens are difficult to generate. Now by identifying a time window in which the body's immune response to a particular pathogen is at its peak, Wrammert et al. have developed a new technique for the efficient generation of high-affinity human mAbs. In individuals given a booster vaccination against influenza, the number of influenza specific IgG+ antibody-secreting cells in the bloodstream peaks a week after vaccination, accounting for about 6% of all peripheral B cells. By harvesting B cells during this time window, it was possible to produce more than 50 human mAbs that bound to the three target influenza strains with high affinity. The whole procedure took less than a month, which is much quicker that than conventional methods of producing mAbs. The technique should be applicable to any infectious disease for which vaccines are available. This paper demonstrates the efficient generation of high-affinity human monoclonal antibodies after booster vaccination with a conventional influenza vaccine. Pre-existing neutralizing antibody provides the first line of defence against pathogens in general. For influenza virus, annual vaccinations are given to maintain protective levels of antibody against the currently circulating strains. Here we report that after booster vaccination there was a rapid and robust influenza-specific IgG+ antibody-secreting plasma cell (ASC) response that peaked at approximately day 7 and accounted for up to 6% of peripheral blood B cells. These ASCs could be distinguished from influenza-specific IgG+ memory B cells that peaked 14–21 days after vaccination and averaged 1% of all B cells. Importantly, as much as 80% of ASCs purified at the peak of the response were influenza specific. This ASC response was characterized by a highly restricted B-cell receptor (BCR) repertoire that in some donors was dominated by only a few B-cell clones. This pauci-clonal response, however, showed extensive intraclonal diversification from accumulated somatic mutations. We used the immunoglobulin variable regions isolated from sorted single ASCs to produce over 50 human monoclonal antibodies (mAbs) that bound to the three influenza vaccine strains with high affinity. This strategy demonstrates that we can generate multiple high-affinity mAbs from humans within a month after vaccination. The panel of influenza-virus-specific human mAbs allowed us to address the issue of original antigenic sin (OAS): the phenomenon where the induced antibody shows higher affinity to a previously encountered influenza virus strain compared with the virus strain present in the vaccine1. However, we found that most of the influenza-virus-specific mAbs showed the highest affinity for the current vaccine strain. Thus, OAS does not seem to be a common occurrence in normal, healthy adults receiving influenza vaccination.