Abstract We analyzed role of individual variable heavy (FdVH) and variable light (FdVL) domains in comparison with VH+VL pair (scFv) originating from a polyspecific bovine IgM, with an exceptionally long CDR3H (61 amino acids), and a monospecific IgG1 antibody in antigen (Ag) recognition and virus neutralization functions. To this end, recombinant FdVH, FdVL and scFv were constructed and expressed in Pichia pastoris from bovine polyspecific IgM and IgG1 encoding cDNA. The scFv1H12 showed polyspecific antigen recognition similar to parent IgM antibody with minor differences. Unlike variable light domain FdVL1H12, variable heavy domain FdVH1H12 recognized multiple antigens that differed from scFv1H12 and the parent IgM antibody. Nevertheless, role of FdVL1H12 in providing structural support to FdVH in antigen recognition is noted. By contrast, the individual FdVH073 and FdVL074, originating from induced BoHV-1 neutralizing IgG1 antibody, recognized target epitope on BoHV-1 relatively weakly when compared to VH+VL pair as scFv3-18L. Both VH and VL domains of induced IgG antibody are required to achieve BoHV-1 neutralization function. To conclude, there exist subtle functional differences in relative contribution of VH and VL from polyspecific IgM and monospecific IgG antibodies in antigen recognition and virus neutralization functions. [Supportd by NSERC Canada]