Protective efficacy of four recombinant fimbrial proteins of virulent Aeromonas hydrophila strain ML09-119 in channel catfish

Abstract

Aeromonas hydrophila is a reemerging pathogen of channel catfish (Ictalurus punctatus); recent outbreaks from 2009 to 2014 have caused the loss of more than 12 million pounds of market size catfish in Alabama and Mississippi. Genome sequencing revealed a clonal group of A. hydrophila isolates with unique genetic and phenotypic features that is highly pathogenic in channel catfish. Comparison of the genome sequence of a representative catfish isolate (ML09-119) from this virulent clonal group with lower virulence A. hydrophila isolates revealed four fimbrial proteins unique to strain ML09-119. In this work, we expressed and purified four A. hydrophila fimbrial proteins (FimA, Fim, MrfG, and FimOM) and assessed their ability to protect and stimulate protective immunity in channel catfish fingerlings against A. hydrophila ML09-119 infection for vaccine development. Our results showed catfish immunized with FimA, Fim, FimMrfG, and FimOM exhibited 59.83%, 95.41%, 85.72%, and 75.01% relative percent survival, respectively, after challenge with A. hydrophila strain ML09-119. Bacterial concentrations in liver, spleen, and anterior kidney were significantly (p<0.05) lower in vaccinated fish compared to the non-vaccinated sham groups at 48h post-infection. However, only the Fim immunized group showed a significantly higher antibody titer in comparison to the non-vaccinated treatment group (p<0.05) at 21days post-vaccination. Altogether, Fim and FimMrfG recombinant proteins have potential for vaccine development against virulent A. hydrophila infection.

Comparative Genomics of Aeromonas hydrophila Secretion Systems and Mutational Analysis of hcp1 and vgrG1 Genes From T6SS

“…All fish experiments were conducted in accordance with a protocol approved by the Institutional Animal Care and Use Committee at Mississippi State University. Virulence of vAh Δ hcp1 and vAh Δ vgrG1 was compared to A. hydrophila wild-type (WT) strain ML09-119 by immersion route of exposure as described (Abdelhamed et al, 2016). Briefly, 120 6-month-old specific-pathogen-free (SPF) channel catfish fingerlings (18.10 ± 0.56 cm, 50.90± 3.76 g) were stocked into twelve 40-liter flow-through tanks (10 fish/tank) and acclimated for a week.…”

Characterization of Histopathological and Ultrastructural Changes in Channel Catfish Experimentally Infected with Virulent Aeromonas hydrophila

“…Bacterial bath challenge was conducted as described previously ( Abdelhamed et al, 2016 ). Briefly, the water level in each tank was dropped to 10 l, and 100 ml of overnight culture was added to each tank to yield approximately 4.3 × 10 10 CFU/ml water.…”

Recombinant ATPase of Virulent Aeromonas hydrophila Protects Channel Catfish Against Motile Aeromonas Septicemia

“…Several research groups have identified candidate DNA or recombinant protein vaccines for MAS (23–28), but to date, there is no protective vaccine available against MAS caused by vAh. Previously, we purified four fimbrial proteins (FimA, Fim, MrfG, and FimOM) and three outer membrane proteins (major outer membrane protein OmpA1, TonB-dependent receptor, and transferrin-binding protein A) and assessed their ability to stimulate protective immunity in channel catfish fingerlings against vAh infection (17, 29). In the present study, expression and purification of vAh ATPase protein in E. coli were successful, and purified ATPase protein was recovered from the inclusion body.…”

“…At 3 weeks post-immunization, catfish were experimentally infected by bath immersion with 2.8 × 10 10 CFU/ml of A. hydrophila ML09-119 for 6 h at 30°C (17). Bacterial infection dose was chosen based on previous experimental infection doses (8, 18).…”