Table 2.

Spirochete number and OspC production within ticks feeding on mice treated with OspA antiseruma

OspA antiserum dilutionMean no. of borreliae per tick (SD)bNo. of spirochetes producing OspC/total (%)
1:1012,100 (6,087)1/54 (2)
1:2554,900 (5,948)* 12/73 (16)
1:50107,300 (8,928)* 26/62 (42)
1:200172,000 (20,736)38/70 (54)
  • a Groups of four mice were passively administered hyperimmune OspA antiserum at different dilutions as described in Table 1, footnote a . Twenty-four hours after passive immunization, B. burgdorferi-infected nymphal ticks were placed on the mice and allowed to feed. Sixty hours into the blood meal, 20 feeding nymphs were removed from the mice in each group, homogenized, and prepared for staining with fluorescently labeled antibodies to count the mean number of spirochetes per nymph. The proportion of spirochetes in each group producing OspC was determined by performing double-labeling immunofluorescence with an OspC antiserum and an antiserum developed against whole spirochetes. In each group, 50 to 75 individual spirochetes staining with the B. burgdorferi antiserum (FITC channel) were examined for labeling with the OspC antiserum (rhodamine channel) to determine the percentage of spirochetes producing OspC.

  • b The mean numbers of spirochetes in the two groups marked with asterisks are significantly different from one another (Student’s t test, P < 0.05).