Homologous and heterologous Borrelia burgdorferi challenge of infection-derived immune rabbits using host-adapted organisms

We have recently found that strain B31 infection-immune rabbits are complet ely protected against homologous challenge with large numbers (>10(6)) of h ost-adapted Borrelia burgdorferi (HAB) (E. S. Shang, C. I. Champion, X. Wu, J. T. Skare, D. B. Bianco, J. N. Miller, and M. A Lovett, Infect. Immun. 6 8:4189-4199, 2000). In this study, we have extended these findings to deter mine whether B31 strain infection-immune rabbits are also protected against heterologous HAB challenge. Infection-immune rabbits challenged with large numbers (>106) of homologous HAB strain B31 were completely protected from erythema migrans (EM) and skin and disseminated infection. In contrast, in fection-immune rabbits challenged with heterologous HAB strains N40 and Sh- 2-82 were completely susceptible to EM and skin and disseminated infection; challenge with strain 297 also resulted in EM and infection of the skin an d viscera, but clearance of infection occurred 3 weeks postchallenge. These findings confirm that immunity elicited in rabbits by B31 strain infection confers complete protection against large-dose homologous HAB challenge bu t not against a heterologous strain.