Hybridoma-based generation of a functional IgM antibody targeting the 160-loop of influenza B virus haemagglutinin.

Although most available therapeutic antibodies are immunoglobulin (Ig) G, their limited access at mucosal sites has prompted increasing interest in alternative isotypes, such as IgM. Therapeutic IgM antibodies have primarily been obtained from patient sera; however, methods for generating IgM antibodies that specifically target antigenic regions remain poorly established. In the present study, we aimed to generate IgM antibodies recognising the 160-loop region of haemagglutinin (HA) of influenza B virus using peptide immunisation. BALB/c mice were subcutaneously immunised with a synthetic peptide corresponding to the HA 160-loop region. As a result, 666 hybridomas were established, from which 20 peptide-reactive and 8 HA-reactive IgM antibodies were obtained. The most effective clone, BHA177, exhibited a concentration-dependent neutralising activity against the parental IBV strain, achieving 40% neutralisation at 50 μg/mL. These findings indicate that peptide immunisation can elicit functional IgM antibodies recognising the HA 160-loop region and provide a proof-of-concept for further optimisation of peptide-based IgM generation strategies.