r-bZP3 was arsanilated using a modification of the procedure of Nisnoff (1967). Briefly, arsanilic acid (100 mg) was dissolved in 5 ml of I M HCI. A IO ml stock of NaN02 (10 mg/ml) was also prepared fresh and added dropwise to the arsanilic acid solution while vortexing. Activation of arsanilic acid was checked on starch-KI paper. The ice cold activated arsanilic acid solution was added dropwise to the protein solution (5 mg of r-bZP3 in 100 mM PB, pH 7.4) stirring constantly in an ice water bath, while pH was maintained between 9.0 and 9.5 with 10 N NaOH. The protein solution was dialyzed extensively against I 00 mM PB having 4 M urea. Arsanilation of r-bZP3 was checked by ELISA using ars-r-bZP3 for coating ( 1 flg/well) and using a 1:100 dilution of murine anti-ars MAb, R 16.7 (Durdik et al., 1 989). Bound Ab was revealed using anti-mouse HRPO conjugate (I :5000). Three monkeys previously immunized with r-bZP3-DT conjugate (MRA-375, MRA-640 and MRA-672) and 2 naive monkeys (MRA-446 and MRA-670) were immunized at 2 intramuscular sites with 250 flg of ars-bZP3 conjugate using Squalene:Arlacel A ( 4: 1) as an adjuvant. Boosters were administered at intervals of 20 days and bleeds were collected I 0 days post immunization. Bleeds were analyzed by ELISA using r-bZP3 and ars-BSA for coating to determine anti-bZP3 and anti-ars Ab titres as described earlier.

Arsanilation of r-bZP3