TABLE 5

Protection against a B. burgdorferi challenge by infected tick bitea

ImmunogenChallenge strainNo. of tissue samples culture positive/totalNo. of mice protected/total
PBS-NMSB. burgdorferi B31-A315/250/4b
Δp66 bacteriaB. burgdorferi B31-A30/25c5/5d
p66cp bacteriaB. burgdorferi B31-A30/25c5/5d
PBS-NMSB. burgdorferi N40 D10/E918/251/5
Δp66 bacteriaB. burgdorferi N40 D10/E90/25c5/5e
p66cp bacteriaB. burgdorferi N40 D10/E90/25c5/5e
  • a All mice were immunized four times and challenged with Borrelia-infected nymphal ticks 4 weeks after the last immunization. Five ticks were placed on each mouse for the challenge. Mice were euthanized 2 weeks after the tick challenge. In each group, Δp66- or p66cp-immunized mice were compared to the PBS-NMS-treated controls with Fisher's exact test in GraphPad Prism.

  • b One mouse was not infected in this group. This was probably due to the low infectivity rate of the unfed ticks. Replete ticks recovered from one mouse in this group did not show infection upon culture. Thus, we could not conclude that this mouse was actually exposed to infectious organisms able to be transmitted via tick bite. We therefore excluded this mouse from the denominator.

  • c P < 0.0001.

  • d P < 0.01.

  • e P < 0.05.