Table 3. Stabilized OspA monomers are protective in a mouse model using B. afzelii infected ticks for challenge.
| Treatment | Infected/Totala | ||
| Immunogen | Dose | Vaccine | Placebo |
| OspA2-His | 5.0 µg | 1/25*** | 20/23 |
| M2-His | 5.0 µg | 8/16n.s. | 13/15 |
| M2A-His | 5.0 µg | 4/27*** | 20/23 |
| M2B-His | 5.0 µg | 1/25*** | 20/23 |
| M2C-His | 5.0 µg | 1/21*** | 20/23 |
| M2D-His | 5.0 µg | 2/11** | 7/8 |
| M2E-His | 5.0 µg | 4/26*** | 20/23 |
Immunized mice were challenged with ticks harboring B. afzelii and the infectious status was determined six weeks later by screening for the presence of spirochete specific antibodies (VlsE ELISA) and DNA (nested PCR targeting the 16S–23S intergenic spacer), using terminal sera and ear tissue respectively. Mice were regarded as infected when at least one of the two methods was positive.
a
Data from four experiments following the same protocol have been combined and only data from mice where at least one fully fed tick was collected are presented. The p-values were calculated with Fisher’s exact test (two tailed); ** p<0.01, *** p<0.001 and n.s. not significant.