Development of a lateral flow test for the rapid detection of Avibacterium paragallinarum in chickens suspected of having infectious coryza

Background

Infectious coryza (IC) is an acute respiratory disease of growing chickens and layers caused by Avibacterium paragallinarum. The development of tools that allow rapid pathogen detection is necessary in order to avoid disease dissemination and economic losses in poultry. An Av. paragallinarum-specific Ma-4 epitope of the TonB-dependent transporter (TBDT) was selected using bioinformatic tools in order to immunize a BalbC mouse and to produce monoclonal antibodies to be used in a lateral flow test (LFT) developed for Av. paragallinarum detection in chicken nasal mucus samples.

Results

The 1G7G8 monoclonal antibody was able to detect TBDT in Av. paragallinarum cultures (serogroups: A, B and C) by Western blot and indirect ELISA assay. Consequently, we developed a self-pairing prototype LFT. The limit of detection of the prototype LFT using Av. paragallinarum cultures was 1 × 10⁴ colony-forming units (CFU)/mL. Thirty-five nasal mucus samples from chickens suspected of having infectious coryza were evaluated for the LFT detection capacity and compared with bacterial isolation (B.I) and polymerase chain reaction (PCR). Comparative indicators such as sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive values (NPV) and the kappa index (K) were obtained. The values were 100.0% Se, 50% Sp, 65.4% PPV, 100% NPV, and 0.49 K and 83.9% Se, 100% Sp, 100% PPV, 44.4% NPV, and 0.54 K for the comparison of the LFT with B.I and PCR, respectively. Additionally, the LFT allowed the detection of Av. paragallinarum from coinfection cases of Av. paragallinarum with Gallibacterium anatis.

Conclusions

The results indicate that the self-pairing prototype LFT is suitable for the detection of TBDT in Av. paragallinarum cultures as well as in field samples such as nasal mucus from Av. paragallinarum-infected chickens. Therefore, this prototype LFT could be considered a rapid and promising tool to be used in farm conditions for Av. paragallinarum diagnosis.

Production and evaluation of a panel of monoclonal antibodies against Haemophilus paragallinarum

We report on the production and characterisation of monoclonal antibodies (MAbs) against Haemophilus paragallinarum, the causative agent of infectious coryza. A bank of 8 MAbs were produced by traditional techniques - four against the reference strain for Page serovar A (0083) and four against the reference strain for Page serovar C (Modesto). Seven of the eight MAbs were shown to be IgG(1) with one being nontypable. None of the MAbs had HI activity and none gave any detectable reaction when examined by Western blotting. None of the MAbs gave a positive reaction in the indirect ELISA with any of the eight type strains of Pasteurella species or sub-species. None of our 8 MAbs gave serovar specific reactions when used in an indirect ELISA format. There was a trend for the serovar A MAbs to give a higher titre with serovar A isolates/strains and a similar trend for the serovar C MAbs to give higher titres with the serovar C isolates/strains.

Relation between antigen release and immune response of oil adjuvanted vaccines in chickens

The relationship between release properties of the model antigen, bovine serum albumin (BSA), from formulations in vitro and immune response after administration of various oil adjuvanted vaccines containing liquid paraffin was examined in chickens. The vaccine prepared at an hydrophile-lipophile-balance (HLB) number of 4.8 showed slower release of BSA and higher immune response on injected chickens than that with an HLB number of 6.0. Decreases of aqueous volume ratio in the formulation also led to slower release of BSA and higher immune response. The slower release rate of BSA showed higher ELISA antibody titer even at 20 weeks after vaccination. The ELISA antibody titer inversely was related to the constant release rate, k, calculated from the in vitro release test. The correlation coefficient was 0.863. The immune response of oil adjuvanted vaccines containing Haemophilus paragallinarum agreed well with these results with BSA. Our results indicated that a stronger and more prolonged immune response of oil adjuvanted vaccines was achieved by slower release rate of antigen from the formulation. In addition, there was a good correlation between immune response and the value of k.