Both IgA and IgG antibodies are involved in the response against influenza. The constant heavy chain has long been thought to be determining the isotype only, but recently its effect on the variable regions has been discussed in literature. In this project the effect of an isotype switch, achieved via restriction cloning, of an anti-NA antibody has been characterized. Affinity, inhibition and effect on NA upon binding have been investigated. Literature has long focused on HA as the main influenza antigen, but emerging evidence of NA involvement at multiple steps of the viral cycle has increased the attention to it; its nature as an enzyme increases the inhibition strategies of anti-NA antibodies. ELISA assays indicate that the isotype switch to IgA retained the original affinity from IgG2a. The altered kinetics of NA, investigated by kinetic MUNANA assay, indicate that IgA retained the targeted epitope and the induced conformational change in the active site/substrate binding domain caused by IgG2a; this indicates the epitope being close to the active site. Steric inhibition remained the main inhibition mechanism, with comparable results in the ELLA assay; the dimerization of IgA was negligible due to epitope position. The viral lunge titre was also similar, indicating that NPR-05 does not rely on Fc interactions to inhibit IAVs. Overall, NPR-05 mechanism of action is isotype independent; the retained binding affinity and conformational change suggest a dynamic binding model, potentially preventing any changes caused by the isotype, due to the paratope adapting to the epitope upon binding.