In vitro efficiency of intra- and extracellular immunization with mouse anti-YGNNV antibody against yellow grouper nervous necrosis virus

Mouse monoclonal antibody (MAb-18) against yellow grouper nervous necrosis virus (YGNNV) coat protein was developed and assayed for its neutralization ability. In the present study, we cloned and sequenced the cDNAs encoding heavy (γ) and light (κ) chains by constructing a cDNA library of the MAb-18 hybridoma. Three expression vectors, pCMV-NNV-18H (γ), pCMV-NNV-18L (κ), and pCMV-NNV-18HL (both γ and κ chains) were constructed and successfully expressed in grouper brain (GB) cells. Western blotting results indicated the secretion of antibody in to the medium with successful folding. Extracellular antibodies secreted by the pCMV-NNV-18HL transfected GB cells, neutralized well with YGNNV and showed the highest neutralization index (log₁₀ of NI) value 4. A significant reduction of titre (99.9%) was observed, when the intracellularly immunized GB cells were propagated with the YGNNV. These preliminary demonstrations suggest the immunoprophylactic use of plasmid constructs encoding the genes of mouse MAbs and the possibility of producing transgenic pathogen-free spawners and larvae, which contain freely available MAbs against pathogen in the circulation.