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Thirty guinea pigs were immunized with 40 microgram of bovine parathyroid hormone, bPTH(1-84), and divided into 6 groups with a similar primary response. Each group was boosted twice with a different dose of antigen (0.04 to 40 microgram). The titer (30% binding of tracer) and affinity (% displacement with 320 pg of bPTH(1-84) were studied. The primary response was maximal at 61 days; titers were 1 x 10(-4) or less and affinity was low. The response was maximal 25 days after each booster. After the first, the highest titers, 5.2 +/- 2.6 x 10(-4) (mean +/- S.D.) were seen in the 40 microgram group and a positive correlation was observed between the dose of antigen and the titer (r = .7386, p less than 0.001) for doses greater than 0.6 microgram. This remained true after the second booster although titers were lower in all groups. Affinity was greater after the first booster (35.85 +/- 20.38%, n = 30) than after the second (23.24 +/- 20.73, n = 30, p less than 0.0025), but was similar in all groups. Selected antisera reacted with antigenic determinants in regions 1-34, 53-84 and 35-53 of the bPTH molecule. Cross-reactivity with human PTH(1-84) was maximal in the 53-84 region. In conclusion, antibodies against all regions of bPTH can be raised in the guinea pig. Once a primary response is elicited, best titers are achieved by boosting with high doses of antigen without any detrimental effect on antisera affinity.

Sensitive techniques were used to detect e antigen and the corresponding antibody (anti-e) among 368 voluntary blood donors positive for hepatitis B surface antigen in the Montreal area and 310 people living in close contact with them. Neither e nor anti-e was found in the absence of markers of hepatitis B virus (HBV). Among the blood donors e antigen was detected in 23 and anti-e in 313, and 32 were negative for both markers. Of the 368 blood donors 330 were of French origin and 38 from other ethnic groups. The 23 e-positive subjects were unequally distributed among the ethnic groups: only 14 (4.2%) were recruited among the French group while 9 (23.7%) were recruited among other ethnic groups (P less than 0.001). This differences among ethnic groups might be related to the vertical or horizontal mode of dissemination of HBV infection.