Evaluation of protein-A linked monoclonal antibody latex agglutination test for diagnosis of nuclear polyhedrosis virus (BmNPV) of silkworm Bombyx mori L.

The symptomology of BmNPV infection in Bombyx mori L depends on the stages of infection. Discernible symptoms develop at later stages of infection, which leads to improper diagnosis and poor crop yield with sericulturists. In the present study development of direct and protein-A linked monoclonal antibody latex (PALMAL) agglutination test for the detection of BmNPV infection in silkworm is described. Latex beads were precoated with protein-A and then sensitised with monoclonal antibody MA-231 (125 micrograms/ml). PALMAL test could detect 1 x 10(5) nuclear polyhedra/test and is ten times more sensitive than the direct agglutination test employing purified polyclonal antibodies. No agglutination was observed in presence of B. thuringiensis, S. marcescens, N. bombycis, group-A streptococci, Staphylococcus aureus, E. coli and normal haemolymph protein indicating the specificity of the test. Fifty haemolymph samples collected from the field were evaluated by PALMAL test. Twenty one samples having infection other than BmNPV, failed to show positive agglutination. Twenty five samples having > or = 5 x 10(6) BmNPV/ml showed positive agglutination. However, 4 samples having < 5 x 10(6) BmNPV/ml failed to show positive agglutination thereby indicating the limit of sensitivity of the assay.