The procedure was based on the assay of Engwall and Perlmann
(1972). The standard curve was prepared using purified LV. Nunc-
Immunoplate Polisorp microtiter plates were loaded with 50 lL/
well of the LV standard (0–120 ng) dissolved in a buffer containing
15 mM sodium carbonate, 35 mM sodium bicarbonate, pH 9.6
(coating buffer). Samples of hemolymph, ovary, hepatopancreas
and eggs were diluted with the coating buffer. Aliquots of 50 lL
were pipeted into the wells and incubated at 37 C for 90 min.
The antigen solutions were then shaken out, and each well was
filled with 300 lL of PBS, pH 7.4, containing 3% (w/v) non-fat dry
milk. The plates were incubated at room temperature for 2 h and
subsequently washed three times with 0.05% (v/v) Tween in PBS.
The anti-LV rabbit serum diluted in PBS-Tween (1:1000) containing
3% non fat dry milk was poured into each well, and plates were
incubated overnight at 4 C and washed three times as above
indicated.