PASSIVE IMMUNITY TO WHITE SPOT SYNDROME VIRUS (WSSV) IN PENAEUS MONODON TREATED WITH MONOCLONAL ANTIBODIES OF THE HETEROLOGOUSLY PRODUCED VP28 VIRAL ENVELOPE PROTEIN

Abstract

White spot syndrome virus (WSSV) is a highly pathogenic and prevalent virus affecting shrimp culture worldwide including Taiwan. In the present study, the viral envelope protein, VP28, gene of the WSSV was cloned into a pET28a expression vector. VP28 was expressed as a protein with a 6-histidine tag in Escherichia coli and purified by a Ni-NTA column. Antiserum was raised against this recombinant VP28 protein in BALB/C mice, and it recognized the VP28 protein in purified virions and recombinant proteins. The antiserum was mixed with arginine (100 ppm), lysine (168 ppm), and phenylalanine (88 ppm), and the titer of the antibody was 20,000-fold/ml. A series of monoclonal antibodies was tested for their ability to neutralize WSSV infectivity by immersion and oral administration. Our results proved that the antibody developed against the VP28 protein could efficiently prevent or control WSSV infection in post-larval and juvenile stages by immersion and oral administration. Furthermore, the postlarvae obtained from the antibody-treated group had > 60% survival after 20 days of challenge, illustrating that the antibody produced from heterologously expressed VP28 may specifically provide passive immunity against the WSSV pathogen. Therapeutic studies illustrated that shrimp losses could be controlled within 5 days of infection using this monoclonal antibody. These results should be considered in the light of the potential application of anti-VP28 antibodies as a prophylactic drug in aquaculture.