Grouper nervous
necrosis virus (GNNV)
infection causes mass grouper mortality, leading to substantial economic loss in Taiwan. Traditional methods of controlling GNNV
infections involve the challenge of controlling
disinfectant doses; low doses are ineffective, whereas high doses may cause environmental damage. Identifying potential methods to safely control GNNV
infection to prevent viral outbreaks is essential. We engineered a virus-binding bacterium expressing a myxovirus resistance (
Mx) protein on its surface for GNNV removal from
phosphate-buffered saline (PBS), thus increasing the survival of grouper fin (GF-1) cells. We fused the grouper
Mx protein (which recognizes and binds to the coat
protein of GNNV) to the C-terminus of outer membrane
lipoprotein A (lpp-Mx) and to the N-terminus of a bacterial
autotransporter adhesin (Mx-AIDA); these constructs were expressed on the surfaces of Escherichia coli BL21 (BL21/lpp-Mx and BL21/Mx-AIDA). We examined bacterial surface expression capacity and GNNV binding activity through
enzyme-linked
immunosorbent assay; we also evaluated the GNNV removal efficacy of the bacteria and viral cytotoxicity after bacterial adsorption treatment. Although both constructs were successfully expressed, only BL21/lpp-Mx exhibited GNNV binding activity; BL21/lpp-Mx cells removed GNNV and protected GF-1 cells from GNNV
infection more efficiently. Moreover, salinity affected the GNNV removal efficacy of BL21/lpp-Mx. Thus, our GNNV-binding bacterium is an efficient microparticle for removing GNNV from 10‰ brackish water and for preventing GNNV
infection in groupers.