Characterization of the protective antibody response to Borrelia burgdorferi in experimentally infected LSH hamsters

Development of Organoids to Study Infectious Host Interactions

Emerging organoid research is paving way for studies in infectious diseases. Described here is a technique for the generation of stem-cell derived organoids for human small intestine and lung together with methods to infect such organoids with a mock pathogen (Cryptosporidium parvum). Such systems are amenable to imaging and processing for molecular biological analyses. It is the intent of this chapter to provide a simple, routine organoid procedure so that in vitro studies with Borrelia such as cell invasion and dissemination can be conducted.

Metamorphoses of Lyme disease spirochetes: phenomenon of Borrelia persisters

The survival of spirochetes from the Borrelia burgdorferi (sensu lato) complex in a hostile environment is achieved by the regulation of differential gene expression in response to changes in temperature, salts, nutrient content, acidity fluctuation, multiple host or vector dependent factors, and leads to the formation of dormant subpopulations of cells. From the other side, alterations in the level of gene expression in response to antibiotic pressure leads to the establishment of a persisters subpopulation. Both subpopulations represent the cells in different physiological states. “Dormancy” and “persistence” do share some similarities, e.g. both represent cells with low metabolic activity that can exist for extended periods without replication, both constitute populations with different gene expression profiles and both differ significantly from replicating forms of spirochetes. Persisters are elusive, present in low numbers, morphologically heterogeneous, multi-drug-tolerant cells that can change with the environment. The definition of “persisters” substituted the originally-used term “survivors”, referring to the small bacterial population of Staphylococcus that survived killing by penicillin. The phenomenon of persisters is present in almost all bacterial species; however, the reasons why Borrelia persisters form are poorly understood. Persisters can adopt varying sizes and shapes, changing from well-known forms to altered morphologies. They are capable of forming round bodies, L-form bacteria, microcolonies or biofilms-like aggregates, which remarkably change the response of Borrelia to hostile environments. Persisters remain viable despite aggressive antibiotic challenge and are able to reversibly convert into motile forms in a favorable growth environment. Persisters are present in significant numbers in biofilms, which has led to the explanation of biofilm tolerance to antibiotics. Considering that biofilms are associated with numerous chronic diseases through their resilient presence in the human body, it is not surprising that interest in persisting cells has consequently accelerated. Certain diseases caused by pathogenic bacteria (e.g. tuberculosis, syphilis or leprosy) are commonly chronic in nature and often recur despite antibiotic treatment. Three decades of basic and clinical research have not yet provided a definite answer to the question: is there a connection between persisting spirochetes and recurrence of Lyme disease in patients?

Persistent Borrelia Infection in Patients with Ongoing Symptoms of Lyme Disease

INTRODUCTION

Lyme disease is a tickborne illness that generates controversy among medical providers and researchers. One of the key topics of debate is the existence of persistent infection with the Lyme spirochete, Borreliaburgdorferi, in patients who have been treated with recommended doses of antibiotics yet remain symptomatic. Persistent spirochetal infection despite antibiotic therapy has recently been demonstrated in non-human primates. We present evidence of persistent Borrelia infection despite antibiotic therapy in patients with ongoing Lyme disease symptoms.

METHODS

In this pilot study, culture of body fluids and tissues was performed in a randomly selected group of 12 patients with persistent Lyme disease symptoms who had been treated or who were being treated with antibiotics. Cultures were also performed on a group of ten control subjects without Lyme disease. The cultures were subjected to corroborative microscopic, histopathological and molecular testing for Borrelia organisms in four independent laboratories in a blinded manner.

RESULTS

Motile spirochetes identified histopathologically as Borrelia were detected in culture specimens, and these spirochetes were genetically identified as Borreliaburgdorferi by three distinct polymerase chain reaction (PCR)-based approaches. Spirochetes identified as Borrelia burgdorferi were cultured from the blood of seven subjects, from the genital secretions of ten subjects, and from a skin lesion of one subject. Cultures from control subjects without Lyme disease were negative for Borrelia using these methods.

CONCLUSIONS

Using multiple corroborative detection methods, we showed that patients with persistent Lyme disease symptoms may have ongoing spirochetal infection despite antibiotic treatment, similar to findings in non-human primates. The optimal treatment for persistent Borrelia infection remains to be determined.

Hamster and murine models of severe destructive Lyme arthritis

Arthritis is a frequent complication of infection in humans with Borrelia burgdorferi. Weeks to months following the onset of Lyme borreliosis, a histopathological reaction characteristic of synovitis including bone, joint, muscle, or tendon pain may occur. A subpopulation of patients may progress to a chronic, debilitating arthritis months to years after infection which has been classified as severe destructive Lyme arthritis. This arthritis involves focal bone erosion and destruction of articular cartilage. Hamsters and mice are animal models that have been utilized to study articular manifestations of Lyme borreliosis. Infection of immunocompetent LSH hamsters or C3H mice results in a transient synovitis. However, severe destructive Lyme arthritis can be induced by infecting irradiated hamsters or mice and immunocompetent Borrelia-vaccinated hamsters, mice, and interferon-gamma- (IFN-γ-) deficient mice with viable B. burgdorferi. The hamster model of severe destructive Lyme arthritis facilitates easy assessment of Lyme borreliosis vaccine preparations for deleterious effects while murine models of severe destructive Lyme arthritis allow for investigation of mechanisms of immunopathology.

Ineffectiveness of tigecycline against persistent Borrelia burgdorferi

The effectiveness of a new first-in-class antibiotic, tigecycline (glycylcycline), was evaluated during the early dissemination (1 week), early immune (3 weeks), or late persistent (4 months) phases of Borrelia burgdorferi infection in C3H mice. Mice were treated with high or low doses of tigecycline, saline (negative-effect controls), or a previously published regimen of ceftriaxone (positive-effect controls). Infection status was assessed at 3 months after treatment by culture, quantitative ospA real-time PCR, and subcutaneous transplantation of joint and heart tissue into SCID mice. Tissues from all saline-treated mice were culture and ospA PCR positive, tissues from all antibiotic-treated mice were culture negative, and some of the tissues from most of the mice treated with antibiotics were ospA PCR positive, although the DNA marker load was markedly decreased compared to that in saline-treated mice. Antibiotic treatment during the early stage of infection appeared to be more effective than treatment that began during later stages of infection. The viability of noncultivable spirochetes in antibiotic-treated mice (demonstrable by PCR) was confirmed by transplantation of tissue allografts from treated mice into SCID mice, with dissemination of spirochetal DNA to multiple recipient tissues, and by xenodiagnosis, including acquisition by ticks, transmission by ticks to SCID mice, and survival through molting into nymphs and then into adults. Furthermore, PCR-positive heart base tissue from antibiotic-treated mice revealed RNA transcription of several B. burgdorferi genes. These results extended previous studies with ceftriaxone, indicating that antibiotic treatment is unable to clear persisting spirochetes, which remain viable and infectious, but are nondividing or slowly dividing.

Human Lyme disease vaccines: past and future concerns

The development of a vaccine for Lyme disease was intensely pursued in the 1990s. However, citing a lack of demand, the first human Lyme disease vaccine was withdrawn from the market less than 5 years after its approval. The public's concerns about the vaccine's safety also likely contributed to the withdrawal of the vaccine. Nearly a decade later, no vaccine for human Lyme disease exists. The expansion of Lyme disease's endemic range, as well as the difficulty of diagnosing infection and the disease's steady increase in incidence in the face of proven preventative measures, make the pursuit of a Lyme disease vaccine a worthwhile endeavor. Many believe that the negative public perception of the Lyme disease vaccine will have tarnished any future endeavors towards its development. Importantly, many of the drawbacks of the Lyme disease vaccine were apparent or foreseeable prior to its approval. These pitfalls must be confronted before the construction of a new, effective and safe human Lyme disease vaccine.

Anti-CD25 antibody treatment of mice vaccinated and challenged with Borrelia spp. does not exacerbate arthritis but inhibits borreliacidal antibody production

CD4(+) CD25(+) T cells are a population of regulatory T cells responsible for the modulation of the immune response in several autoimmune and infectious disease models. We previously showed that adoptive transfer of enriched CD4(+) CD25(+) T cells also plays a major role in the prevention of arthritis in Borrelia-vaccinated (Borrelia burgdorferi isolate 297) and -challenged (B. bissettii) mice. Here, we present evidence that administration of anti-CD25 antibody at the time of challenge or at later intervals fails to enhance the development of severe destructive osteoarthropathy in Borrelia-vaccinated C57BL mice. However, Borrelia-vaccinated and -challenged mice receiving anti-CD25 antibody developed decreased borreliacidal antibody titers compared to vaccinated and challenged controls. These findings suggest that additional mechanisms besides CD4(+) CD25(+) T cells are involved in the regulation of the immune response to Borrelia infection following vaccination.

The versatile roles of antibodies in Borrelia infections

Antibodies are the primary weapons of the mammalian immune system that are used against the tick-borne borreliae, the causative agents of relapsing fever and Lyme disease worldwide. Some antibody responses have 'traditional' functions, whereas others are more versatile and have novel functions and modes of action. At a time when the multiple functions of antibodies are being increasingly recognized and passive immunization is being revived as therapy for infectious and other diseases, the versatile nature of the antibody response to the borreliae fits well with this antibody renaissance.

Destructive arthritis in vaccinated interferon gamma-deficient mice challenged with Borrelia burgdorferi: modulation by tumor necrosis factor alpha

We found that Borrelia burgdorferi-vaccinated gamma interferon-deficient (IFN-gamma(0)) mice challenged with B. burgdorferi developed prominent chronic destructive osteoarthropathy. When these mice were treated with anti-tumor necrosis factor alpha (TNF-alpha) antibody, the severity of the destructive osteoarthritis was enhanced and affected the mobility of the animals. In addition, extensive swelling of the hind paws occurred. In contrast, treatment of B. burgdorferi-vaccinated, challenged IFN-gamma(0) mice with recombinant TNF-alpha (rTNF-alpha) inhibited the development of arthritis, including swelling of the hind paws. Moreover, treatment of vaccinated, challenged IFN-gamma(0) mice with anti-TNF-alpha inhibited fourfold the production of an antibody that kills B. burgdorferi, while treatment of vaccinated, challenged IFN-gamma(0) mice with rTNF-alpha slightly elevated the level of the borreliacidal antibody. These results suggest that the level of TNF-alpha directly or indirectly regulates the production of borreliacidal antibody and the development of vaccine-induced destructive Lyme osteoarthritis. Studies are in progress to determine the mechanism by which TNF-alpha-dependent cytokines generate the destructive arthritis.

Gamma interferon inhibits production of Anti-OspA borreliacidal antibody in vitro

The ability of a Lyme borreliosis vaccine to induce and maintain sustained levels of borreliacidal antibody is necessary for prolonged protection against infection with Borrelia burgdorferi. Vaccination against infection with B. burgdorferi could be improved by determining the mechanism(s) that influences the production of protective borreliacidal antibody. Borreliacidal antibody was inhibited in cultures of lymph node cells obtained from C3H/HeJ mice vaccinated with formalin-inactivated B. burgdorferi and cultured with macrophages and B. burgdorferi and treated with recombinant gamma interferon (rIFN-gamma). The suppression of production of outer surface protein A (OspA) borreliacidal antibody by rIFN-gamma was not affected by the time of treatment. In addition, treatment with rIFN-gamma inhibited the production of other anti-B. burgdorferi antibodies. By contrast, treatment of cultures of immune lymph node cells with anti-IFN-gamma marginally increased the production of borreliacidal antibody and enhanced the production of other antibodies directed against B. burgdorferi. These results show that IFN-gamma does not play a major role in the production of anti-OspA borreliacidal antibody. Additional studies are needed to determine which cytokine(s) will enhance production of borreliacidal antibody.

Specific immune response to a synthetic peptide derived from outer surface protein C of Borrelia burgdorferi predicts protective borreliacidal antibodies

In a previous study, we described the development of a new specific serodiagnostic test for Lyme disease involving enzyme-linked immunosorbent assay and a synthetic peptide, OspC-I. The OspC-I peptide is derived from part of the outer surface protein C (OspC) amino acid sequence of Borrelia burgdorferi and is located in the region conserved among B. burgdorferi sensu stricto or sensu lato isolates. In this study, we demonstrate that sera containing antibodies against OspC-I from patients with early Lyme disease had borreliacidal activity against isolates of three genospecies of Lyme disease spirochete, B. burgdoreferi B31, B. garinii HPI and B. afzelii HT61. However, the borreliacidal activity against B. burgdorferi, which has not been isolated in Japan, was weaker than that against the other species. Vaccination of mice with OspC-I induced the production of anti-OspC-I antibodies in serum with borreliacidal activity. The immune mouse serum had significantly higher levels of borreliacidal activity against HP1 and HT61, than against B31. Neutralization of borreliacidal activity with anti-IgM antibodies showed that the borreliacidal activity of anti-OspC-I antibodies in serum was due to IgM. Furthermore. mice vaccinated with OspC-I were protected against challenge with HPI and HT61. but not fully protected against infection with B31. These results suggest that OspC-I is not only a specific antigen for use in serodiagnostic tests for Lyme disease, but is also a potential candidate for a Lyme disease vaccine in Japan.

Specificity of infection-induced immunity among Borrelia burgdorferi sensu lato species

The specificity of infection-induced immunity in mice infected with cultured or host-adapted Borrelia burgdorferi sensu lato, the agent of Lyme disease, was examined. Sera obtained from mice following infection with high and low doses of cultured B. burgdorferi sensu stricto, transplantation of infected tissue (host-adapted spirochetes), or tick-borne inoculation all showed protective activity in passive immunization assays. Infection and disease were similar in mice infected with cultured spirochetes or by transplantation. Thus, the adaptive form of inoculated spirochetes did not influence the immune response during active infection. Mice infected with B. burgdorferi sensu stricto and then cured of infection with an antibiotic during early or late stages of infection were resistant to challenge with high doses of homologous cultured spirochetes for up to 1 year. In contrast, actively immune mice infected with different Borrelia species (B. burgdorferi sensu lato, B. burgdorferi sensu stricto cN40, Borrelia afzelii PKo, and Borrelia garinii PBi) and then treated with an antibiotic were resistant to challenge with cultured homologous but not heterologous spirochetes. Similar results were achieved for actively immune mice challenged by transplantation and by passive immunization with sera from mice infected with each of the Borrelia species and then challenged with cultured spirochetes. Arthritis and carditis in mice that had immunizing infections with B. afzelii and B. garinii and then challenged by transplantation with B. burgdorferi sensu stricto were equivalent in prevalence and severity to those in nonimmune recipient mice. These results indicate that protective immunity and disease-modulating immunity that develop during active infection are universal among species related to B. burgdorferi sensu lato but are species specific.

Inhibition of the production of anti-OspA borreliacidal antibody with T cells from hamsters vaccinated against Borrelia burgdorferi

The serious morbidity associated with Lyme borreliosis has focused considerable effort on the development of a comprehensive vaccine for protection against infection with Borrelia burgdorferi. Induction of borreliacidal antibody by vaccination or infection has been shown to correlate with protection of humans and animals against infection with the Lyme spirochete. In this report, we showed that high levels of borreliacidal antibody (titer of 1,280) were produced in vitro when T and B cells from hamsters 14 days after vaccination were incubated with macrophages and B. burgdorferi. By contrast, T and B cells from hamsters 7 or 21 days after vaccination failed to initiate production of borreliacidal activity. Furthermore, the T cells from hamsters 7 or 21 days after vaccination inhibited the in vitro production of borreliacidal antibody when cocultured with T and B cells obtained from hamsters 14 days after vaccination. When cell-free supernatants from the suspensions of T and B cells from hamsters 14 days after vaccination were absorbed with recombinant OspA, they lost nearly all borreliacidal activity. The removal of anti-OspA antibody resulted in a decrease in borreliacidal titer from 1,280 to less than 4. These results demonstrate that T cells from vaccinated animals can prevent a sustained production of protective borreliacidal antibody.

Accelerated infectivity of tick-transmitted Lyme disease spirochetes to vector ticks

We determined whether the span of infectivity of Lyme disease spirochetes (Borrelia burgdorferi) to vector ticks varies with the mode of infection in laboratory mice. Noninfected larval deer ticks were permitted to feed on two strains of spirochete-infected mice that had been naturally (via tick bite) and parenterally (via needle injection) infected with B. burgdorferi 2, 4, or 8 weeks earlier, and engorged ticks were dissected and examined for spirochetes by direct immunofluorescence microscopy. After initial infection, spirochetal infectivity to ticks was less efficient in needle-infected mice than in mice infected via tick bites. Tick-transmitted spirochetes develop more rapidly from the skin of infected mice and do not induce a strong antispirochete antibody response during the early stage of infection.

Complement evasion by the Lyme disease spirochete Borrelia burgdorferi grown in host-derived tissue co-cultures: role of fibronectin in complement-resistance

The effectiveness of complement-mediated killing of Borrelia burgdorferi, the causative agent of Lyme disease, in the presence of host-derived tissues was studied. Second and high passage forms of B. burgdorferi 297 isolate were grown in a LEW/N rat joint tissue co-culture system and in artificial BSK medium. Guinea pig complement and third week immune serum from hamsters with experimental Lyme disease were added to the cultures. Both high and low passage borrelia grown in BSK medium died and did not revive after 3 weeks incubation in BSK medium. However, 5-12% of tissue co-cultured borrelia survived the first complement-mediated lysis. Repeated re-growth and lysis cycles in tissue co-culture resulted in isolation of an 85% complement-resistant population of B. burgdorferi. Joint tissue culture supernatant collected on the third day of tissue culture, and fibronectin (25 micrograms/ml), also protected spirochetes from complement-mediated lysis in contrast to BSK or fresh co-culture medium. Complement-mediated lysis may not be an effective mechanism in eradication of borrelia, and the chronicity of Lyme disease may be due to resistance of B. burgdorferi variants to host immune defense mechanisms in the presence of host-derived tissues.

Detection of anti-Borrelia burgdorferi antibody responses with the borreliacidal antibody test, indirect fluorescent-antibody assay performed by flow cytometry, and western immunoblotting

Borreliacidal antibodies participate in the resolution of Lyme disease by clearing Borrelia burgdorferi sensu lato from the host. Detection of borreliacidal antibodies is also valuable for determination of the specific serodiagnosis of Lyme disease. We show in this work that antibody detected by the borreliacidal antibody test did not correlate with antibody detected by the indirect fluorescent-antibody assay or Western immunoblotting. Detection of borreliacidal antibody decreased with elimination of the spirochete from the host in the presence or absence of therapy. By contrast, the antibody responses detected by the indirect fluorescent-antibody assay or Western immunoblotting remained elevated or continued to expand, respectively. This suggests that the borreliacidal antibody test is a prognostic indicator for clearance of the spirochete. Additional investigations with humans are needed to confirm the prognostic potential of the borreliacidal antibody test.

Involvement of CD4+ T lymphocytes in induction of severe destructive Lyme arthritis in inbred LSH hamsters

We determined that Borrelia burgdorferi-specific CD4+ T lymphocytes are responsible for the development of severe destructive Lyme arthritis and affect the production of borreliacidal antibody. Severe destructive Lyme arthritis was readily evoked in immunocompetent inbred LSH hamsters vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant when challenged with B. burgdorferi sensu stricto isolate 297. When vaccinated hamsters were depleted of CD4+ T lymphocytes by the administration of monoclonal antibody GK1.5 and challenged, they failed to develop severe destructive arthritis. Similarly, nonvaccinated hamsters with or without the depletion of CD4+ T lymphocytes failed to develop severe destructive arthritis. In addition, depleting CD4+ T lymphocytes impaired the development of borreliacidal antibody in vaccinated and nonvaccinated hamsters challenged with the Lyme borreliosis spirochete. These findings show that CD4+ T lymphocytes are important for the recognition of arthritogenic and protective antigens of B. burgdorferi sensu lato isolates. Additional studies are needed to define the mechanisms responsible for the development of severe destructive Lyme arthritis and the production of borreliacidal antibody.

Differential spirochetal infectivities to vector ticks of mice chronically infected by the agent of Lyme disease

We determined whether the infectivity of the Lyme disease spirochete (Borrelia burgdorferi) to vector ticks varies with the duration of infection in laboratory mice. Thus, noninfected nymphal deer ticks were permitted to feed on two strains of early (2 months after infection) and late (8 months after infection) spirochete-infected mice. The attached ticks were removed from their hosts at specified time intervals and were thereafter examined for spirochetes by direct immunofluorescence microscopy. Spirochetes can be acquired by nymphal ticks as fast as 8 h after attachment. More than 80% of the attached ticks acquired spirochetal infection within 48 h after feeding on early spirochete-infected mice. In contrast, spirochetal infectivity to ticks was less than 50% after feeding on late spirochete-infected mice. The overall infectivity of spirochete-infected mice to ticks correlated with the duration of tick attachment. In addition, there was no adverse effect on the spirochetal infectivity to ticks by high levels of host antibody against spirochetes, and no obvious differences in infectivity to ticks was observed by the site of tick feeding. We conclude that the span of spirochetal infectivity to ticks varies with the duration of infection in mice and suggest that spirochetes may persist and may be evenly distributed in the skin of infected hosts, regardless of prominent host immunity.

Sera from OspA-vaccinated dogs, but not those from tick-infected dogs, inhibit in vitro growth of Borrelia burgdorferi

Dogs were challenged with Borrelia burgdorferi by exposure to ticks, with or without prior protection from infection by recombinant OspA (rOspA) vaccination. Sera from these dogs were tested for their capability to inhibit the growth of B. burgdorferi in vitro. Bacterial growth was detected by a color change in the culture medium, and the optical density was measured with a spectrophotometer in microtiter plates. By growth inhibition, which was complement dependent, the color change was lacking after 5 days of incubation. Over a 1-year study, nonvaccinated dogs infected by exposure to ticks showed high antibody titers to B. burgdorferi by kinetic enzyme-linked immunosorbent assay (KELA). The same sera did not inhibit spirochetal growth or did so only at a low dilution. These results corresponded to the lack of OspA and OspB antibodies seen in Western blots (immunoblots), and these dogs were not protected from infection or disease. In contrast, dogs immunized with rOspA prior to challenge with infected ticks produced high antibody titers, as determined by KELA, but their sera also had high growth-inhibiting antibody titers. Western blot analysis showed a strong band in the 32-kDa region when the sera of these dogs were tested. When adjuvant was administered with rOspA, antibody titers by both KELA and growth inhibition were higher and persisted longer in the immunized dogs. All dogs immunized with rOspA were protected from infection and disease.

Antibody response of the mouse reservoir of Borrelia burgdorferi in nature

To determine whether the white-footed mouse reservoir host (Peromyscus leucopus) of the agent of Lyme disease (Borrelia burgdorferi) naturally mounts an immune response against the full range of antigens expressed by this zoonotic pathogen, we analyzed the pattern of immunoreactivity of these rodents at sites in which the intensity of transmission differs. Although the incidence of seroconversion within the reservoir population relates proportionally to the density of subadult deer ticks (Ixodes dammini), seroprevalence appears constant. About a fifth as many juvenile mice recognize spirachete antigens as do adult mice. Virtually all reservoir mice in nature recognize the p20, p35.5, p39, and p58 antigens, regardless of the intensity of transmission. Seropositive mice retain reactivity to a wide range of spirochetal antigens. Few mice recognize flagellin, OspB, and OspC. Although a third of serum samples include reactivity to a 31-kDa band, this reaction is irregular and may represent an uncharacterized antigen that comigrates with OspA. Mice captured where transmission is intense recognize the same spectrum of antigens as do mice captured where vector ticks are scarce.

Single exposure of mice to Borrelia burgdorferi elicits immunoglobulin G antibodies characteristic of secondary immune response without production of interleukin-4 by immune T cells

Borrelia burgdorferi antigen can elicit immunoglobulins (Igs) characteristic of the primary and secondary immune responses without the contribution of an interleukin-4-producing helper T-cell population. Single exposure of mice to soluble B. burgdorferi antigen elicited both Th1-type and Th2-type antispirochete antibodies. Production of the Ig classes showed different patterns with increasing time postinjection (IgM levels decreased; IgG1, IgG2a, IgG2b, and IgG3 levels increased; IgE was not detected), and Ig patterns were similar to those produced in infected mice. Upon infectious challenge, immunized mice achieved maximal titers of all antispirochete IgG subclasses more quickly than unimmunized mice did. In contrast to the antibody responses which showed both Th1- and Th2-type patterns, T-cell immune response to either immunization or infection was characterized by interleukin-2 and gamma interferon production; interleukin-4 and interleukin-5 were undetectable. Injection with whole spirochetes induced a pattern of antibodies and cytokine production similar to those obtained by injection with soluble antigen. In addition, mouse strains of different major histocompatibility complex backgrounds produced similar patterns of Ig in response to immunization. None of the various parameters of immunization tested resulted in detectable interleukin-4 production by primary or secondary immune T cells. The production of both IgM and IgG1 at early times following a single exposure to spirochete antigen clearly differs from immune responses to haptens or model protein antigens. Production of similar Ig classes in infected and immune mice implies that antigen-specific antibody is responsible for passive immunizing activity found in immune sera.

Early and late antibody responses to full-length and truncated constructs of outer surface protein A of Borrelia burgdorferi in Lyme disease

The immunoglobulin G (IgG) antibody response to outer surface protein A (OspA) of Borrelia burgdorferi has been reported to occur late in the course of Lyme disease. To learn when reactivity to particular epitopes of OspA develops and whether the strength of particular responses correlates with the duration of arthritis and HLA-DR specificities, we determined the IgM and IgG responses by enzyme-linked immunosorbent assay in 128 patients with various manifestations of Lyme disease to full-length recombinant OspA and three OspA fragments which divided the protein approximately into thirds. Among the 10 patients who were followed serially, an early IgM response was often found to epitopes in all three fragments of OspA, sometimes accompanied by a weak IgG response, primarily to an epitope in the middle third of the protein. Months to years later, the seven patients who had prolonged or moderate episodes of arthritis developed strong IgG responses to OspA, especially to epitopes in the N-terminal and C-terminal fragments, that paralleled the course of the arthritis. In single serum samples from 128 patients, a similar pattern of IgM and IgG reactivity with OspA epitopes was seen in patients with early or late manifestations of the illness. Of the 80 patients with arthritis, 62 (78%) had IgG responses to OspA, usually with the strongest reactivity to the C-terminal fragment. In these patients, the strength of the IgG response to OspA correlated with the duration of arthritis; in HLA-DR4-positive patients, most of whom had chronic arthritis, this association was attributable to reactivity with the C-terminal fragment. Thus, patients with Lyme disease often have early responses to OspA, but those with prolonged arthritis do not develop IgG responses to certain epitopes of the protein until late in the illness. In patients with HLA-DR4, the strength of IgG reactivity with one or more epitopes in the C-terminal fragment of OspA correlates with the duration of arthritis.

Abilities of OspA proteins from different seroprotective groups of Borrelia burgdorferi to protect hamsters from infection

The ability of vaccination with recombinant OspA from six seroprotective groups of Borrelia burgdorferi sensu lato to induce protection against infection with homologous and other Lyme spirochetes was examined in hamsters. Antisera generated against the OspA proteins of B. burgdorferi sensu stricto S-1-10 and C-1-11 (seroprotective groups 1 and 2, respectively), Borrelia afzelii BV1 (seroprotective group 4), and Borrelia garinii LV4 (seroprotective group 5) were able to kill the homologous spirochete in vitro but not other isolates. Surprisingly, antisera against B. afzelii PKo (seroprotective group 6) and B. burgdorferi sensu lato LV5 (seroprotective group 3) OspA proteins were unable to kill the homologous organism, although LV5 OspA antisera killed the heterologous isolates S-1-10 and LV4. In vivo vaccination studies supported the in vitro findings, confirming that vaccination with a single OspA protein does not provide complete protection against challenge with all Lyme disease spirochetes. In addition, OspA antibodies from some isolates may not protect against the homologous isolate. The induction of protective antibodies against other B. burgdorferi proteins may be necessary to insure a comprehensive Lyme disease vaccine.

Borrelia burgdorferi-specific T lymphocytes induce severe destructive Lyme arthritis

This is the first documentation that Borrelia burgdorferi-specific T lymphocytes are involved in the pathogenesis of Lyme arthritis. We present direct evidence that T lymphocytes obtained from inbred LSH hamsters vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant conferred on naive recipient hamsters the ability to develop severe destructive arthritis when challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297. By contrast, recipients infused with normal T lymphocytes and challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297 failed to develop severe destructive arthritis. The T lymphocytes transferred were obtained from the lymph nodes of vaccinated and nonvaccinated hamsters by depleting B lymphocytes by using monoclonal antibody 14-4-4s (< 1% B lymphocytes by flow cytometric analysis). The enriched T lymphocytes showed enhanced proliferation to stimulation with concanavalin A and failed to respond to lipopolysaccharide. Moreover, only the enriched T lymphocytes from vaccinated hamsters proliferated on exposure to a whole-cell preparation of B. burgdorferi sensu stricto isolate C-1-11 in the presence of mitomycin-treated syngeneic antigen-presenting cells. These results demonstrate that B. burgdorferi-specific T lymphocytes primed by vaccination with a whole-cell preparation of inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant are involved in the development of severe destructive arthritis. Additional experiments are needed to define the precise mechanism(s) responsible for the development of Lyme arthritis.

Differential immune responses to Borrelia burgdorferi in European wild rodent species influence spirochete transmission to Ixodes ricinus L. (Acari: Ixodidae)

Immune responses to Borrelia burgdorferi and their influence on spirochete transmission to Ixodes ricinus were analyzed in the natural European reservoir hosts; i.e., the mouse species Apodemus flavicollis (yellow-necked mouse) and Apodemus sylvaticus (wood mouse) and the vole species Clethrionomys glareolus (bank vole), and, in addition, in the laboratory mouse strain NMRI. Naive and preimmunized rodents were infected either by artificially infected I. ricinus larvae or by intradermal injection of spirochetes. Independent of the species, all animals developed antibodies to various spirochetal antigens. However, antibodies to the outer surface proteins A (OspA) and B (OspB) were not found in recipients infected via ticks. Rodents of the genus Apodemus and of the NMRI strain showed higher levels of B. burgdorferi-specific antibodies than those of the species C. glareolus. The rate of spirochete transmission to noninfected ticks correlated with both the quality and quantity of spirochete-specific antibodies generated in the various species: high levels of spirochete-specific immunoglobulins correlated with low transmission rates. Furthermore, lower transmission rates were observed with rodents expressing antibodies to OspA and OspB (i.e., intradermally infected or immunized) than with those lacking these specificities (i.e., infected via ticks). The study provides evidence that transmission of B. burgdorferi from natural hosts to ticks is controlled by the specificity and quantity of spirochete-reactive antibodies and suggests that immunity to B. burgdorferi in natural reservoir hosts is an important regulatory factor in the horizontal transmission of B. burgdorferi in nature.

Induction of experimental allergic arthritis with outer surface proteins of Borrelia burgdorferi

OBJECTIVE

The arthritogenic potential of the cationic outer surface proteins (Osp) from Borrelia burgdorferi was tested in rats.

METHODS

Water-soluble Osps were prepared by butanol extraction and were administered by intraarticular injection. Tissue injury was assessed by scintigraphy and histology.

RESULTS

A mild arthritis was seen in naive rats. Preimmunized animals had more severe, longer lasting bouts of inflammation.

CONCLUSION

The Osps of Borrelia burgdorferi are potent arthritogens in rats. These immunodominant antigens may play a role in the development of Lyme arthritis in humans.

Development of destructive arthritis in vaccinated hamsters challenged with Borrelia burgdorferi

We present the first direct evidence that adverse effects, particularly severe destructive arthritis, can develop in vaccinated hamsters after challenge with Borrelia burgdorferi sensu lato isolates. Hamsters were vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant. A severe destructive arthritis was readily evoked in vaccinated hamsters challenged with the homologous B. burgdorferi sensu stricto isolate C-1-11 before high levels of protective borreliacidal antibody developed. Once high levels of C-1-11 borreliacidal antibody developed, hamsters were protected from homologous challenge and development of arthritis. Vaccinated hamsters, however, still developed severe destructive arthritis when challenged with other isolates of the three genomic groups of B. burgdorferi sensu lato (B. burgdorferi sensu stricto isolate 297, Borrelia garinii isolate LV4, and Borrelia afzelii isolate BV1) despite high levels of C-1-11 specific borreliacidal antibody. Vaccines that contained whole spirochetes in adjuvant induced destructive arthritis, but this effect was not dependent on the isolate of B. burgdorferi sensu lato or the type of adjuvant. These studies demonstrate that caution is necessary when employing whole spirochetes in adjuvant for vaccination to prevent Lyme borreliosis. Additional studies are needed to identify the antigen(s) responsible for the induction and activation of arthritis and to define the immune mechanisms involved.

A bactericidal antibody to Borrelia burgdorferi is directed against a variable region of the OspB protein

Borrelia burgdorferi, an agent of Lyme disease, is killed by some monoclonal antibodies in the absence of complement or phagocytes. In the present study, the bactericidal action of monoclonal antibodies against B. burgdorferi and B. hermsii, a cause of relapsing fever, was further characterized. H6831, an antibody recognizing the OspB proteins of some B. burgdorferi strains, and H4825, an antibody specific for one serotype of B. hermsii, were purified, and Fab fragments of the antibodies were prepared. In time-kill studies, more than 99.9% of strain B31 B. burgdorferi cells were killed after 30 min of exposure to H6831 Fab fragments. The MBC of the Fab fragments was 10 micrograms/ml. Electron microscopy revealed that the bactericidal Fab fragments produced numerous blebs and cell lysis of the borrelias for which they were specific. To identify the epitope for H6831, the OspB sequences of H6831-susceptible and -resistant strains and mutants were determined. The deduced OspB proteins of all H6831-resistant strains and mutants differed from the strain B31 OspB at residue 253. Murine antisera raised against a 21-mer synthetic peptide representing the region around residue 253 were specific for strain B31 by Western blot (immunoblot) and growth inhibition assays. Furthermore, the antipeptide serum inhibited the binding of H6831 to whole borrelias. These findings indicated that the linear component of the bactericidal antibody's epitope was located at or near residue 253.

Ability of canine Lyme disease vaccine to protect hamsters against infection with several isolates of Borrelia burgdorferi

We used flow cytometry to determine levels of borreliacidal antibodies in hamsters after vaccination with a commercially available canine Lyme disease vaccine. In addition, we evaluated the ability of vaccinated hamsters to resist infection with several isolates of Borrelia burgdorferi. Borreliacidal antibodies could be detected 1 week after a primary vaccination, peaked at weeks 3 to 5, and then rapidly declined. One week after a booster vaccination, borreliacidal activity was detected at a dilution of 1:10,240, and it decreased fourfold by week 10 after the booster vaccination. Vaccinated hamsters were protected against infection with < or = 10(6) B. burgdorferi 297 organisms during the peak borreliacidal response (5 weeks after primary vaccination or 2 weeks after booster vaccination). However, hamsters were not fully protected from development of Lyme arthritis when the titer of borreliacidal antibodies was < 1:5,120. In addition, no significant borreliacidal activity was induced against B. burgdorferi C-1-11, LV4, or BV1, which belong to three other seroprotective groups. These studies demonstrate that vaccination with the canine Lyme disease vaccine induces protective antibodies against B. burgdorferi 297. However, significant levels of borreliacidal antibodies are not produced until 5 weeks after vaccination, and protection is short-lived. In addition, no borreliacidal activity was induced against other isolates of B. burgdorferi. Because of this, the incorporation of multiple isolates or protein subunits may be necessary to increase the effectiveness of future vaccines.

Differentiation of borreliacidal activity caused by immune serum or antimicrobial agents by flow cytometry

We demonstrated that borreliacidal activity caused by immune serum and complement can easily be differentiated by flow cytometry from killing activity caused by antimicrobial agents that are commonly used for the treatment of Lyme disease. Assay suspensions containing normal or immune serum were incubated with Borrelia burgdorferi in the presence or absence of ceftriaxone, doxycycline, penicillin, and phosphomycin for 2, 8, 16, and 24 h. Samples containing killing activity were identified by using flow cytometry and acridine orange. In 30 min, the effects of immune serum and complement were easily distinguished from the killing of spirochetes by antimicrobial agents by adding fluorescein isothiocyanate-conjugated goat anti-hamster immunoglobulin. This simple procedure greatly enhanced the usefulness of the borreliacidal assay by eliminating a major source of false-positive reactions.

Lyme disease: laboratory diagnosis and serologic testing

Although identified less than 20 years ago, Lyme disease has proved to be the most common tick-borne disease in the United States: some 10,000 cases were reported in 1992. In some cases the disease may be transitory and of little consequence but in others it may become chronic and severely disabling. Accurate diagnosis is, therefore, of great importance but, as this article shows, laboratory testing techniques still need improvement.

Antigenic stability of Borrelia burgdorferi during chronic infections of immunocompetent mice

Mice were actively immunized by intradermal inoculation with 10(4) cloned Borrelia burgdorferi bacteria and then cured of the B. burgdorferi infection with an antibiotic after 90 days. They were resistant to intradermal 10(2)- or 10(4)-bacterium challenge infection with either the original cloned B. burgdorferi or B. burgdorferi isolated from each punch biopsies at 90 days of infection (prior to antibiotic treatment), including autologous B. burgdorferi isolates. In contrast, sham-infected (nonimmune) mice were susceptible to challenge infection with both early and late B. burgdorferi isolates. Since there was a potential for in vitro modification of the spirochetes during the 2-week culture period which would obscure results, an alternate means of challenge infection, using tissue transplants, was implemented. By using the same approach, mice were immunized by infection, treated with antibiotics, but challenged by subcutaneous transplantation of ear skin pieces biopsied and frozen prior to antibiotic treatment. Mice were infected for 15, 90, or 180 days before biopsy and antibiotic treatment and then transplant challenged with autologous infected tissue. Sham-immunized mice received infected tissue, and immune mice received uninfected tissue as controls. Mice infected for only 15 days, but not mice infected for 90 or 180 days, could be reinfected by autografts, whereas nonimmune mice became infected with tissues collected at each of these intervals and immune mice transplanted with normal skin were uninfected. These results indicate that immunity to B. burgdorferi is effective against the original inoculum, late isolates of the spirochete, or infected tissues collected at intervals of up to 180 days, suggesting that there is no significant antigenic change in B. burgdorferi during chronic infection.

Passive immunizing activity of sera from mice infected with Borrelia burgdorferi

A single injection of serum from C3H mice at 90 days after intradermal inoculation with 10(4) Borrelia burgdorferi spirochetes protected naive mice when administered subcutaneously at -18 h relative to intradermal challenge inoculation with 10(4) B. burgdorferi spirochetes. When immune serum was given at intervals (-18, 0, +24, +48, and +96 h) relative to intradermal challenge with 10(4) B. burgdorferi spirochetes, it was protective if given before or at the time of challenge but not at later times. Protection with 90-day serum given at -18 h was effective at dilutions up to 1:32, but not 1:64, on the basis of culture or disease at either 5 or 15 days after challenge. Passive immunizing activity was also present in sera from mice at 21 days after intradermal challenge with 10(4), 10(2), or 10(1) spirochetes, indicating that the immunizing component was not dose dependent and probably not related to antibody to outer surface protein A. Passive immunizing titers of sera from mice at days 1, 15, 30, 90, 180, and 360 after intradermal B. burgdorferi inoculation appeared as early as day 15, were highest on day 30, and then declined progressively on days 90, 180, and 360. Immunizing titers of sera from mice at 360 days after intradermal B. burgdorferi inoculation were identical in passively immunized mice challenged with the original inoculum or with B. burgdorferi isolated at 360 days after inoculation, suggesting that there was no antigenic discrimination between the original inoculum and late isolates. These results suggest that protective antibody is produced early in the course of B. burgdorferi infection and is unrelated to antibody to outer surface protein A. In addition, the decline of protective serum titers over time despite persistent infection suggests that the antigens eliciting the protective response are either modified or suppressed, but antigenic modification could not be demonstrated.

The 39-kilodalton protein of Borrelia burgdorferi: a target for bactericidal human monoclonal antibodies

Three human monoclonal immunoglobulin M antibodies against Borrelia burgdorferi, obtained from in vitro-stimulated peripheral blood lymphocytes, reacted in Western blots (immunoblots) with a prominent 39-kDa peptide and a faint band of approximately 66 kDa. Two of these antibodies showed bactericidal activity without addition of complement. All three antibodies were reactive in an enzyme immunoassay with cloned P39 (W.J. Simpson, M.E. Schrumpf, and T.G. Schwan, J. Clin. Microbiol. 28:1329-1337, 1990), suggesting that the target molecule of these antibodies is identical to the P39 protein. In addition, the majority of supernatants from human lymphocytes stimulated in vitro with crude B. burgdorferi antigen reacted in this assay, demonstrating that P39, although a minor component of B. burgdorferi, is an immunodominant antigen in these spirochetes. A fourth monoclonal antibody, reacting with OspA, also exhibited bactericidal activity.

Seroprotective groups among isolates of Borrelia burgdorferi

We demonstrated that different seroprotective groups exist among isolates of Borrelia burgdorferi and Borrelia garinii. The major group was composed of isolates 297, B31, S-1-10, MMTI, IPT, and ATCC 35211 and 21 isolates obtained from California, Illinois, New York, Texas, and Wisconsin. A second group was composed of European isolates PBi and G25. A third group was composed of a single isolate, C-1-11. These groupings were supported by Western immunoblot findings. In addition, the seroprotective groups were confirmed by passive transfer of immune sera and challenge of recipient hamsters with the homologous isolate or other isolates of B. burgdorferi or B. garinii. These studies demonstrate that a monovalent vaccine will not provide complete protection against infection with all isolates of B. burgdorferi.

Rapid dissemination by the agent of Lyme disease in hosts that permit fulminating infection

We determined whether the agent of Lyme disease (Borrelia burgdorferi) disseminates more rapidly following deposition in hosts that permit fulminating infection than in hosts in which infection is relatively benign. Thus, individual infected nymphal deer ticks (Ixodes dammini) were permitted to engorge on the ears of C3H mice, and the site of attachment was excised at intervals thereafter. Infection in each mouse was determined by serology and by examining previously noninfected ticks that had engorged on these mice. These results were compared with data obtained similarly by using the CD-1 strain of mice in which the agent is relatively nonpathogenic. When the site of inoculation was ablated within 2 days after the infected tick became replete, dissemination was aborted. Spirochetemia could not be demonstrated in any of these mice. We conclude that Lyme disease spirochetes disseminate from the feeding lesion of an infecting tick more rapidly in certain highly spirochete-susceptible mice than in others in which pathogenesis is less severe.

Experimental Borrelia burgdorferi infection of outbred mice

Infectivity of Borrelia burgdorferi strain 297 in normal outbred ddY mice was examined. Strain 297 was inoculated intraperitoneally in 3-week-old outbred ddY mice. B. burgdorferi was routinely cultured from the heart and urinary bladder 5 to 84 days postinoculation. The combined isolation rate from both heart and urinary bladder was significantly higher than the rate from spleen, kidney, liver, urine, and blood samples. Three- and 10-week-old mice were infected with inocula of 10(4) and 10(5) or more, respectively. Passive transfer of undiluted and 10-fold-diluted anti-297 rabbit serum and active immunization of 50 to 100 micrograms of lyophilized whole cells completely protected mice from infection with B. burgdorferi. These results suggest that the outbred mouse is a convenient model for experimental infection with B. burgdorferi.

Antibody-resistant mutants of Borrelia burgdorferi: in vitro selection and characterization

We used polyclonal antisera and monoclonal antibodies (mAbs) to inhibit the growth of clonal populations of two strains of Borrelia burgdorferi, the Lyme disease agent, and thereby select for antibody-resistant mutants. mAbs were directed at the outer membrane proteins, OspA or OspB. Mutants resistant to the growth-inhibiting properties of the antibodies were present in the populations at frequencies ranging from 10(-5) to 10(-2). The several escape variants that were examined were of four classes. Class I mutants were resistant to all mAbs; they lacked OspA and OspB and the linear plasmid that encodes them. Two other proteins were expressed in larger amounts in class I mutants; mAbs to these proteins inhibited the mutant but not the wild-type cells. Class II mutants were resistant to some but not all mAbs; they had truncated OspA and/or OspB proteins. Class III mutants were resistant only to the selecting mAb; they had full-length Osp proteins that were not bound by the selecting antibody in Western blots. In two class III mutants resistant to different anti-OspA mAbs, missense mutations were demonstrated in the ospA genes. Class IV mutants were likewise resistant only to selecting antibody, but in this case the selecting antibody still bound in Western blots.

Differences of two Borrelia burgdorferi strains in complement activation and serum resistance

Complement activation and serum resistance of the Borrelia burgdorferi strains B31 (American strain) and PKo (European strain) were compared. In 25% (v/v) normal human serum (NHS) free of B. burgdorferi-specific antibodies the cells of the PKo strain were high activators of complement as indicated by rapid and strong C9 consumption, by deposition of up to 336763 C9 molecules per cell and by the formation of the terminal complement complex on the cell surface. By comparison, complement activation by the B31 strain was low with 5.4-fold less C9 deposited per cell. The addition of B. burgdorferi-specific antibodies to NHS either as purified IgG or heat-inactivated patient sera, had no influence on the results with both strains. After an incubation period of 2h at 37 degrees C in 25% (v/v) NHS most cells of the PKo strain had lost their viability as indicated by cell immobilization and failure to multiply in subcultures. In addition, extensive cell fragmentation and bleb formation were observed in the electron microscope. In contrast, the B31 strain remained alive and morphologically intact after the same incubation with NHS. We conclude from our results that complement activation and serum resistance are properties which differ considerably between isolated strains of B. burgdorferi.

Immunoglobulin G2 confers protection against Borrelia burgdorferi infection in LSH hamsters

We showed that immune serum and its immunoglobulin fractions, specifically immunoglobulin G2 (IgG2), could confer complete protection to irradiated hamsters challenged with the Lyme disease spirochete. Immune serum and its immunoglobulin fractions also killed Borrelia burgdorferi in vitro. Depletion of complement in vivo abrogated the ability of IgG2 to confer complete protection against B. burgdorferi. Furthermore, the majority of antibody reactivity directed against B. burgdorferi was found in the IgG2 fraction. These findings demonstrate that IgG2 plays an important role in acquired resistance against infection with B. burgdorferi. Additional studies are needed to determine the mechanism(s) by which B. burgdorferi evades host defenses despite the development of an effective borreliacidal antibody response.

Detection of borreliacidal antibodies in hamsters by using flow cytometry

Flow cytometry can be used to detect antibody that kills Borrelia burgdorferi. Borreliacidal activity was detected within 3 h of incubating B. burgdorferi with immune serum and complement. Right-angle light scatter and propidium iodide fluorescence were the cytometric parameters which correlated best with in vitro killing of B. burgdorferi. Flow cytometry is a rapid method for determining the presence of borreliacidal activity and may lead to a better serodiagnostic test for the detection of Lyme disease.

Nucleotide sequence of the ospAB operon of a Borrelia burgdorferi strain expressing OspA but not OspB

The nucleotide sequence of a 1.6-kb clone containing the gene for outer surface protein A (OspA) of a German strain (GO2) of Borrelia burgdorferi was determined. The deduced amino acid sequence showed a homology of 82% to the OspA molecules from three other B. burgdorferi strains. The best-conserved region was recognized at the 36-amino-terminal amino acids of OspA. OspB could not be identified in the strain investigated, probably because the nucleotide sequence of the ospAB operon prevented expression of the OspB gene.

Long-term protection of mice from Lyme disease by vaccination with OspA

Mice vaccinated with recombinant outer surface protein A (OspA) have been shown to be protected from infection with Borrelia burgdorferi, the agent of Lyme disease, when sacrificed 14 days after challenge with an intradermal inoculum of the spirochete. To determine whether infection was not merely delayed and that protection was long-lasting, we sacrificed vaccinated mice 60, 120, and 180 days after challenge; and to determine whether vaccinated mice retained their immune state over long periods, we challenged mice with B. burgdorferi 60, 90, 120, and 150 days after vaccination. The results of both groups of experiments show that the mice remained free from infection and disease and extend the usefulness of OspA as a vaccine candidate for Lyme borreliosis.

Depletion of complement and effects on passive transfer of resistance to infection with Borrelia burgdorferi

When irradiated hamsters are passively immunized with immune serum before challenge with Borrelia burgdorferi, they are completely protected from arthritis and infection. The complement dependency of this protection was addressed by treating hamsters with cobra venom factor. Depletion of complement abrogated the ability of immune serum obtained 1 and 10 weeks after infection to confer complete protection. By contrast, depletion of complement had no effect on the ability of 3-week immune serum to confer protection. These results suggest that complement-dependent, and possibly complement-independent, antibodies are important for preventing the induction of Lyme arthritis.

Lyme disease assay which detects killed Borrelia burgdorferi

We developed an in vitro assay showing that Borrelia burgdorferi organisms were killed by serum from patients with Lyme disease. Twenty of 20 Lyme disease serum samples caused B. burgdorferi killing in a range of 36 to 99% compared with the mean number of viable spirochetes when sera from 10 healthy individuals were used. The percentage of killing of B. burgdorferi increased with convalescent serum from patients with early Lyme disease. The borreliacidal activity was detectable in some sera diluted 640-fold and was abrogated after treatment with anti-human immunoglobulin G. In contrast, pooled or individual normal human serum did not cause a decrease in the number of viable B. burgdorferi. Borreliacidal activity was also not detected in sera from patients with relapsing fever, rocky mountain spotted fever, syphilis, mononucleosis, rheumatoid factor, or DNA antibodies. Our results show that borreliacidal activity can be used as a specific serodiagnostic test for detecting Lyme disease.

Borreliacidal activity of sera from hamsters infected with the Lyme disease spirochete

An in vitro borreliacidal assay that accurately reflects the levels of protective antibody determined by passive transfer of immunity studies was developed. Borreliacidal antibody in sera obtained from normal hamsters infected with Borrelia burgdorferi was readily detected. When immune serum containing complement was incubated with B. burgdorferi organisms, spirochetes were killed within 2 h. Treating immune serum with anti-hamster immunoglobulin G abrogated the borreliacidal activity. Killing of B. burgdorferi in serum was detected 1 week after infection; it peaked at week 3 and gradually declined. Relatively high levels of borreliacidal antibody were found, especially in week 3 immune serum, which could be diluted 1,280-fold. The decrease in borreliacidal antibody after infection may account for occurrences of reinfection and the remitting course of Lyme disease.