Public health concerns about the morbidity associated with Lyme borreliosis have stimulated efforts to develop an effective vaccine. Several
B. burgdorferi sensu lato proteins, OspA (
9,
20,
24), OspB (
9,
24), OspC (
11,
23,
24), and the 39-kDa protein (
27), are capable of inducing a protective antibody response. Of these, OspA has emerged as the leading Lyme borreliosis vaccine candidate (
29,
30). Two Lyme borreliosis vaccines based on rOspA have been shown to be protective in recent human clinical trials (
29,
30). In addition, an rOspA vaccine has been approved by the USDA for use in dogs. Undoubtedly, these vaccines will be widely used, particularly in regions in which Lyme borreliosis is endemic, such as the upper midwestern and northeastern United States (
7).
Although the Lyme borreliosis vaccines developed to date have been reported to be safe (
17), there are concerns that rOspA might induce adverse effects, such as arthritis (
5,
22,
29,
30). Akin et al. (
1) showed that the level of anti-OspA immunoglobulin G, especially that specific to the C-terminal epitope of OspA, correlated with maximum arthritis in naturally infected patients. In addition, the cellular immune response to OspA was elevated in genetically susceptible persons, particularly those with HLA-DR4 specificity (
14). These patients also had persistent arthritis despite treatment with antimicrobial agents. Furthermore, Gross et al. (
12) identified an immunodominant epitope of OspA for T cells that might be responsible for the induction of treatment-resistant Lyme arthritis. Collectively, these findings suggest that OspA is involved in the induction of arthritis in patients infected with
B. burgdorferi sensu lato.
In this study, we provided direct evidence that rOspA can induce arthritis. Hamsters vaccinated with rOspA in aluminum hydroxide (alum) developed swelling of the hind paws after infection with
B. burgdorferi isolate 297 or C-1-11. Arthritis was detected in the hind paws of all hamsters vaccinated with 30 or 60 μg of rOspA. Histopathologic examination of the swollen hind paws confirmed the development of severe destructive arthritis. In addition, we showed that a canine rOspA vaccine primed (vaccinated) hamsters for induction of arthritis upon challenge with
B. burgdorferi isolate 297. Fifty-seven percent of infected, canine rOspA-vaccinated hamsters developed arthritis. Furthermore, when aluminum hydroxide was incorporated into the canine rOspA vaccine, all hamsters developed arthritis after infection with
B. burgdorferi isolate 297. These results show that different preparations of rOspA can induce arthritis and that aluminum hydroxide augments the adverse response. The FDA-approved rOspA vaccine for humans contains aluminum hydroxide (
30).
In other studies, 50 and 100% of hamsters vaccinated with 120 μg of rOspA developed severe destructive arthritis when challenged with the infectious vaccine-specific isolate of
B. burgdorferi or another isolate of
B. burgdorferi (C-1-11), respectively. Previously, we showed that humans vaccinated with 30 μg of rOspA and a booster elicited a poor anti-OspA protective borreliacidal antibody response (
22) not only against the vaccine-specific agent but also against other isolates of
B. burgdorferi sensu lato. In addition, the anti-OspA borreliacidal antibody titer waned rapidly after vaccination. Although Sigal et al. (
29) and Steere et al. (
30) demonstrated that rOspA was protective in human field trials, neither the level of the anti-OspA borreliacidal antibody response nor its duration of protection against
B. burgdorferi isolates was reported. Lim et al. (
18) showed that vaccinated hamsters developed severe destructive arthritis before protective borreliacidal antibodies developed and after they waned when challenged with
B. burgdorferi or other isolates. Our results and those of Lim et al. (
18) and Padilla et al. (
22) suggest that rOspA primes subjects for induction of arthritis without inducing sustained high levels of anti-OspA borreliacidal antibodies. In support of this theory, several boosters of rOspA are required over a 2-year period to obtain 68 to 78% protection against infection with
B. burgdorferi (
29,
30). Patients received a total of 90 μg of rOspA (
30). Additional studies are needed in humans to determine the duration of the borreliacidal antibody response against both the vaccine-specific isolate and other isolates of
B. burgdorferi. These studies are necessary for defining the composition of the vaccine (number of rOspA molecules) along with the number and schedule of boosters for maintaining high levels of borreliacidal antibody to prevent potential adverse effects upon challenge with homologous or other isolates of
B. burgdorferi.
We used a challenge inoculum of approximately 10
6 viable
B. burgdorferi organisms to elicit severe destructive arthritis in rOspA-vaccinated hamsters. The major histopathologic findings of the joint and capsule, as well as the surrounding soft tissue, resulted in swelling, pain, deformity, and selective loss of movement for the hamster. When vaccinated hamsters were challenged with fewer (10
2 to 10
4)
B. burgdorferi cells, histopathologic responses that resulted in tenosynovitis were detected. This response in hamsters may be similar to the response that occurs in humans. Although vaccine-induced arthritis after natural infection of humans with
B. burgdorferi has not been reported (
29,
30), this does not rule out the possibility that rOspA is an arthritogenic agent. Repeated vaccinations of humans with rOspA in alum to maintain protection against infection with
B. burgdorferi may increase the number of vaccinees reporting symptoms of arthritis. The present phase III clinical trials did not report sufficient numbers of vaccinees challenged with
B. burgdorferi to determine whether rOspA induced arthritis. Human subjects afflicted with rOspA-related tenosynovitis before or after challenge with
B. burgdorferi should consult a clinician. These numbers of complaints need to be determined.
The immunologic mechanism(s) by which rOspA or whole cells of
B. burgdorferi (
18) induce arthritis is incompletely understood. We showed previously that both
B. burgdorferi-specific CD4
+ and CD8
+ T lymphocytes interacted with macrophages to induce severe destructive arthritis (
8). In addition, vaccinated hamsters treated with anti-CD4
+ antibody failed to develop severe destructive arthritis when infected with
B. burgdorferi (
19). Other investigators (
15,
16,
21) have also reported that T cells and their subsets can exert antagonistic influences on the induction of arthritis. Furthermore, rOspA may induce cross-reactive antibodies that initiate an autoimmune response. OspA has been shown to cause polyclonal activation of B cells (
33). These findings indicate that components of the anti-OspA response are T-cell dependent and play a key role in the induction of arthritis. Concomitantly, T-cell-independent responses that result in the production of polyreactive antibodies which cross-react with self-components also occur (
10,
28). Evidence, therefore, that several different epitopes of OspA are involved with the production of autoantibodies and protective anti-OspA borreliacidal antibodies and the induction of arthritis is accumulating. The epitopes of rOspA responsible for production of autoantibodies and arthritis must be eliminated before rOspA becomes a successful vaccine.
In conclusion, rOspA vaccination induces severe destructive Lyme arthritis. The present rOspA vaccines must be modified to eliminate potential side effects. The production of a nonarthritogenic rOspA vaccine can be readily determined by using the hamster model.