Figure 5. Cross-reactive ovine anti-HA pAbs do not exhibit neutralising capacity in vitro or protective capacity in vivo against a different influenza strain.

Purified ovine anti-HA pAbs were analysed for reactivity against PR8 H1N1 and A/PC H3N2 influenza strains via ELISA and haemagglutination inhibition (HAI) assays. Absorbance values from ELISA results (mean ± SEM; (a) were analysed via Mann-Whitney analysis. Endpoint HAI titres are depicted in (b); data are representative of one assay performed in duplicate. To determine in vivo protective capacity against A/PC influenza, mice were administered either control pAb (c) or anti-HA ovine pAb (d) IP (25 mg/kg) and 24 hours later infected intranasally (32 μl) with A/PC (3000 TCID₅₀). The mice were monitored closely and euthanized if 20% weight loss or a clinical score of 5 was achieved (indicated by arrowheads). Weight loss of individual mice (c,d) and group survival (e) are presented. Significance is denoted as thus: * = P < 0.05, ** = P < 0.01.