Anti-Idiotype Vaccine Provides Protective Immunity Against Vibrio Harveyi in Grouper (Epinephelus Coioides)

Abstract

Since anti-idiotype antibodies (anti-Id Abs) can display internal images similar to the epitopes of the original antigens, we aimed to produce an effective vaccine based on anti-Id Abs to protect grouper from Vibrio harveyi. Anti-Id IgG showing V. harveyi-like internal images was produced from rabbits immunized with the Id portion of grouper anti-V. harveyi antibodies and its Fab portion, anti-Id IgG (Fab), was then prepared to use as the anti-Id vaccine. The resulting anti-Id IgG (Fab) was intraperitoneally injected twice at a 21-day interval into grouper to evaluate its ability to induce effective anti-V. harveyi immunity and protection, in comparison with inactivated V. harveyi bacteria. We found that administration of grouper with anti-Id IgG (Fab) resulted in enhanced V. harveyi-specific serum titers, as well as lymphocyte proliferation. In addition, three weeks after boosting, 90% (18/20) of fish immunized with anti-Id IgG (Fab) survived at least 28 days after a lethal challenge of the heterologous, virulent strain of V. harveyi. The capability of this anti-Id IgG (Fab) to imitate the epitopes of V. harveyi antigens and effectively induce protective immunity would be advantageous for its application in developing an efficacious vaccine against V. harveyi for future farm use in fish.

Protective Immunity against Vibrio harveyi in Grouper Induced by Single Vaccination with Poly (Lactide-co-glycolide) Microparticles Releasing Pleurocidin Peptide and Recombinant Glyceraldehyde-3-phosphate Dehydrogenase

“…The Vh MML-1 strain of V. harveyi was isolated from diseased grouper collected from a fish farm (22 • 26 N, 120 • 30 E) in southern Taiwan. The virulence of Vh MML-1 strain had been determined to be a highly virulent strain because 100% mortality rate in grouper by 11 days could be achieved by peritoneal infection with 1.2 × 10 6 CFU (colony-forming unit) of V. harveyi (Vh MML-1), which is an amount two times higher than LD 50 (6 × 10 5 CFU) [8,27]. V. harveyi was cultured in tryptic soy broth (TSB; BD, Franklin Lakes, NJ, USA) with 2% NaCl at 25 • C for 18 h to mid-logarithmic phase [8,27].…”

“…The inactivated V. harveyi bacteria were prepared according to our previous studies [8,27]. The highly virulent Vh MML-1 strain of V. harveyi was grown overnight on tryptic soy agar (TSA) with 2% NaCl at 25 • C. V. harveyi single colony was then picked up from the agar plate and cultured in 5 mL of TSB with 2% NaCl at 25 • C for 18 h. Afterwards, further expand culture to an OD 600 of 1 was undertaken in 500 mL of TSB with 2% NaCl.…”

“…The bacterial lysate was produced from the highly virulent Vh MML-1 strain of V. harveyi as described previously [8,27]. V. harveyi (Vh MML-1) was grown in 50 mL of TSB with 2% NaCl at 25 • C to an OD 600 of 1.…”

“…Twelve weeks after peritoneal vaccination, three grouper from each group were euthanized to collect head kidney lymphocytes as described previously [8,27]. Then, 2 × 10 5 lymphocytes suspended in 200 µL of L-15 culture medium (CM) were seeded in each well of 96-well culture plates, stimulated with V. harveyi lysate (20 µg/mL) and then incubated for 72 h at 25 • C as described previously [8,27]. In addition, Con A (10 µg/mL)and CM-treated cultures were respectively conducted to use as positive and negative controls.…”

“…Then, the BrdU (5-bromo-2 -deoxyuridine) Colorimetric Cell Proliferation ELISA Kit (Roche, Basel, Switzerland) was utilized to measure grouper lymphocyte proliferation according to the manufacturer's instructions. Finally, the stimulation index (SI = OD 450 values from lysate-treated culture or Con A-treated cultures OD 450 values from CM-treated cultures ) for each group was counted as described previously [8,27].…”