Vaccination as a modality to prevent Lyme disease. A status report

A brief history of OspA vaccines including their impact on diagnostic testing for Lyme disease

The only United States Food and Drug Administration approved vaccine preparation to prevent Lyme disease consisted of a single recombinant outer surface protein A (OspA), which was marketed for use from late 1998 until early 2002, with no vaccine currently available for humans for nearly 20 years. OspA vaccines generate an antibody-mediated, transmission blocking immunity, that prevents Borrelia burgdorferi from being transmitted during a tick bite. Although this OspA vaccine was safe and effective, it likely would have required booster doses to maintain immunity, and vaccination regularly caused false positive results on first-tier serologic testing for Lyme disease, when a whole cell-based enzyme immunoassay was used. Clinical trials are in progress to test a new multivalent OspA vaccine designed to prevent Lyme disease in both the United States and Europe.

Robust B Cell Responses Predict Rapid Resolution of Lyme Disease

Lyme disease (Borrelia burgdorferi infection) is increasingly recognized as a significant source of morbidity worldwide. Here, we show that blood plasmablasts and CD27⁻ memory B cells are elevated in untreated Lyme disease, with higher plasmablast levels associated with more rapid resolution of clinical symptoms. Stronger serum reactivity to surface proteins and peptides from B. burgdorferi was also associated with faster resolution of clinical symptoms. Through molecular identifier-enabled antibody heavy-chain sequencing of bulk B cells and single-cell paired-chain antibody sequencing of blood plasmablasts, we characterized immunoglobulin gene usage patterns specific to B. burgdorferi infection. Recombinantly expressed antibodies from expanded lineages bound B. burgdorferi antigens, confirming that these clones are driven by the infection. Furthermore, recombinant sequence-derived antibodies were functional, inhibiting growth of B. burgdorferi in vitro. Elevations and clonal expansion of blood plasmablasts were associated with rapid return to health, while poor plasmablast responses were associated with a longer duration of symptoms following treatment. Plasmablasts induced by B. burgdorferi infection showed preferential antibody gene segment usage, while bulk sequencing of total B cells revealed convergent CDR3 motifs specific to B. burgdorferi-infected patients. Our results show that robust plasmablast responses encoding Bb-static antibodies are associated with more rapid resolution of Lyme disease, and these antibodies could provide the basis for next-generation therapeutics for Lyme disease.

Identification of a defined linear epitope in the OspA protein of the Lyme disease spirochetes that elicits bactericidal antibody responses: Implications for vaccine development

The lipoprotein OspA is produced by the Lyme disease spirochetes primarily in unfed ticks. OspA production is down-regulated by the blood meal and it is not produced in mammals except for possible transient production during late stage infection in patients with Lyme arthritis. Vaccination with OspA elicits antibody (Ab) that can target spirochetes in the tick midgut during feeding and inhibit transmission to mammals. OspA was the primary component of the human LYMErix^™ vaccine. LYMErix^™ was available from 1998 to 2002 but then pulled from the market due to declining sales as a result of unsubstantiated concerns about vaccination induced adverse events and poor efficacy. It was postulated that a segment of OspA that shares sequence similarity with a region in human LFA-1 and may trigger putative autoimmune events. While evidence supporting such a link has not been demonstrated, most efforts to move forward with OspA as a vaccine component have sought to eliminate this region of concern. Here we identify an OspA linear epitope localized within OspA amino acid residues 221–240 (OspA_221–240) that lacks the OspA region suggested to elicit autoimmunity. A peptide consisting of residues 221–240 was immunogenic in mice. Ab raised against OspA_221–240 peptide surface labeled B. burgdorferi in IFAs and displayed potent Ab mediated-complement dependent bactericidal activity. BLAST analyses identified several variants of OspA_221–240 and a closely related sequence in OspB. It is our hypothesis that integration of the OspA_221–240 epitope into a multivalent-OspC based chimeric epitope based vaccine antigen (chimeritope) could result in a subunit vaccine that protects against Lyme disease through synergistic mechanisms.

Reinfection in Patients with Lyme Disease

Lyme disease is the most common tick-borne infection in the United States and Europe. A surprising number of patients experience a subsequent episode of Lyme disease after the first episode has resolved. Reinfection has been well-documented only after successfully treated early infection (nearly always erythema migrans) and can often be recognized clinically by the development of a repeat episode of erythema migrans occurring at a different location on the skin during months when the principal tick vectors are abundant in the environment. Limited data suggest that the clinical and laboratory manifestations of reinfection in patients with Lyme disease with erythema migrans are not very different from those of initial infection. Patients with recurrent infections afford an opportunity to study the role of the immune response in this illness. Because patients with early Lyme disease continue to remain at high risk for reinfection, this population should be targeted for education about prevention of Lyme disease.

[Lyme disease: basis for treatment strategy, primary preventive care and secondary preventive care]

Lyme disease is the most common tick borne disease and is caused by Borrelia burgdorferi sensu lato. Ticks of the genus Ixodes are the vectors that transmit the infection to host mammals in endemic foci. Ixodes is infected by Borrelia at larval stage when it feeds on infected mammals. Man is an occasional host. The infection risk is linked to interaction between human and the natural environment. Strategies for prevention are closely related to the enzootic cycle of the Ixodes tick. Environmental measures to reduced tick density or host mammals are expensive, need to be repeated annually and cannot be applied to large areas. The primary prevention could be reduced to personal preventive measures such as reducing the amount of exposed skin and frequent checking for ticks. The risk of Lyme disease transmission after a tick bite is relatively low, and remains under 4%. The transmission rate depends on the duration of feeding. A rapide tick removal with fine tweezers or preferably special forceps and disinfection of the bite site appear to be the best technique. The absence of scientific evidence, and the risk of adverse events does not lead to recommending antimicrobial prophylaxis. Follow-up and educating the patients on the disease, clinical manifestation, and later primary prevention should be undertaken.

Cost-effectiveness analysis of the Lyme disease vaccine

OBJECTIVE

A vaccine for Lyme disease was approved in 1998 for use in the US. Given the high cost of the vaccine, the low risk of Lyme disease in many areas, and the largely curable nature of the disease, the cost-effectiveness of the vaccine in various risk groups is uncertain. This study was undertaken to examine the cost-effectiveness of the Lyme disease vaccine and the factors that influence its cost-effectiveness.

METHODS

We constructed a Markov decision-analysis model to evaluate the clinical effectiveness and cost-effectiveness of the Lyme disease vaccine in populations at various levels of risk for the disease. The probabilities of clinical events and costs were estimated from reports in the literature. Sensitivity analyses assessed the impact of potential variations of parameters on model results.

RESULTS

At the average national incidence of Lyme disease (0.0067%), the incremental cost-effectiveness of vaccination was approximately $1,600,000 per case averted when a yearly booster was given for 10 years after the standard initial vaccination regimen of 3 inoculations at 0, 1, and 12 months. For populations with an annual Lyme disease incidence of 1% (the incidence in several well-defined geographical areas of the US), the incremental cost-effectiveness was approximately $9,900 per case averted. Disease incidence had to exceed 10% before vaccination with yearly boosters became both more effective and more cost saving than no vaccination.

CONCLUSION

The Lyme disease vaccine is cost-effective only for individuals who live in areas where Lyme disease is endemic and who are frequently exposed to ticks.

Prevention of tick-borne diseases

Ticks are a part of the landscape where humans live, work, and play. Because ticks carry a wide range of organisms that potentially can cause disease in humans, many studies have focused on ways to reduce risk of these diseases. Ticks have biologically complex interactions with microorganisms and with their vertebrate hosts, on whom they depend for blood meals and survival. To consider ways to reduce the burden of tick-borne diseases in humans, it is necessary to understand the biology and ecology of ticks and their interface with humans. In many areas, changes in land use, reforestation, and patterns of human settlements have led to more abundant tick populations, increasing rates of infections in ticks, and increasing contact with human populations. Warmer winter temperatures in temperate regions may extend the transmission season for some ticks and pathogens. Although much of the discussion in this article has focused on I. scapularis and the Lyme disease spirochete (because they have been studied extensively), other tick-pathogen pairs may differ in risk factors for infection and transmission dynamics. Interventions studied to reduce the burden of tick-borne diseases include changing the environment, controlling vertebrate hosts, killing ticks, altering the behavior of humans, treating tick bites, and trying to protect humans through immunologic means (vaccine). All of these approaches have limitations and drawbacks. From a public health perspective, a plan that employs multiple strategies may be most effective. This article has reviewed what is known about preventive interventions, including the vaccine.

Adjuvanted Lyme disease vaccine: a review of its use in the management of Lyme disease

Lyme disease is a potentially serious infection which is caused by the spirochaete Borrelia burgdorferi and is endemic in certain areas of North America, Europe and Asia. Lyme disease vaccine (LYMErix) is an adjuvanted formulation of the outer surface protein A (OspA) of the causative spirochaete. It acts by inducing high titres of anti-OspA antibodies (anti-OspA), which must be present in vaccinated individuals before exposure to B. burgdorferi to provide protection against Lyme disease. Lyme disease vaccine efficacy against Lyme disease was 80% for definite and asymptomatic cases and 76% for definite cases at year 2 using the recommended dosage regimen [30 microg at months 0, 1 and 12 (0, 1, 12 schedule)] in a randomised, double-blind, multicentre trial in 10,936 enrolled adult volunteers who resided in areas of the US endemic for Lyme disease. On the basis of an anti-OspA correlate of protection, Lyme disease vaccine 30 microg was equally effective when administered by a shorter schedule (0, 1, 6 schedule); > or = 90% of adult volunteers developed protective anti-OspA titres with this or the 0, 1, 12 schedule. Although published data are fewer, a 0, 1, 2 schedule has also shown promise in adults. In addition, virtually all children (aged 2 to 15 years) given Lyme disease vaccine 30 microg developed protective anti-OspA titres, but published data are also limited and results of a large paediatric trial are awaited with interest. Long term protection against Lyme disease appears to be possible with Lyme disease vaccine. Although anti-OspA titres decline rapidly after completion of the recommended schedule, booster doses of 30 microg of the vaccine induced protective anti-OspA titres in > or = 96% of adult volunteers when administered 12 and/or 24 months later. Lyme disease vaccine 30 microg is well tolerated: most vaccination-related adverse events were transient and mild or moderate in severity in clinical trials. The most common spontaneously reported adverse event was pain at the injection site in 24% of vaccine recipients (vs 7.6% of the placebo group). The incidence of spontaneously reported, early nonspecific systemic adverse events was <4% but was higher with the vaccine than with placebo for some events (e.g. myalgias, fever and chills but not arthralgia). There appeared to be no association between the vaccine and the incidence of arthritis or any late systemic adverse events. The tolerability profile of Lyme disease vaccine did not appear to vary with the schedule of administration, nor to differ between adults and children.

CONCLUSIONS

Lyme disease vaccine, an adjuvanted formulation of OspA, protects most adults against Lyme disease when administered by the recommended 0, 1, 12 schedule before disease exposure, and is well tolerated. The optimal schedule(s) of administration, duration of protection against Lyme disease, long term tolerability in adults and potential role in children are not fully defined for this vaccine. Lyme disease vaccine is indicated in North America for active immunisation of adults at moderate to high risk of contracting Lyme disease.

Vaccination against Lyme borreliosis

Lyme borreliosis is a worldwide family of tick-borne infections caused by the spirochete Borrelia burgdorferi sensu lato. It is the most common tick-borne human infection in the Western world. There are several subgroups of the spirochete. Two monovalent vaccines against this infection have been presented in the USA, both of which use the borrelial outer surface protein A (OspA) as antigen. The first of these vaccines has been released for general use. A European polyvalent vaccine using the antigen OspC is undergoing clinical trial in the Aland Islands in Finland. Lately, another antigen group, decorin-binding proteins (Dbp), has been considered for immunization purposes. A European vaccine must be effective against several subgroups of the borrelia spirochete, and this complicates the situation compared with that in the USA, where one spirochete subspecies dominates the scene.