BS1 antigen was prepared from stable B. subtilis L-forms
grown in LPB and harvested (2000 g, 4 C, 10 min) in a
High Speed 18 Centrifuge (MSE, Crawley, UK). The pellet
was resuspended in 5 ml phosphate solution (0145 mol
l
ÿ1 NaCl, 001 mol l
ÿ1 phosphate, pH 71; Nairn 1976) and
sonicated (Soniprep 150 Ultrasonic Disintegrator; MSE)
six times until the L-forms were totally disrupted. Preimmune
blood samples were withdrawn via the marginal
ear vein from two New Zealand White rabbits prior to the
®rst injection. BS1 antigen, prepared with Freund's incomplete
adjuvant, was injected intramuscularly at two sites. A
further seven booster injections were administered over a
24-week period and ser