Oral vaccination with an attenuated Salmonella typhimurium strain expressing Borrelia burgdorferi OspA prevents murine Lyme borreliosis

Genetically Engineered Microorganisms and Their Impact on Human Health

The emergence of antibiotic-resistant strains, the decreased effectiveness of conventional therapies, and the side effects have led researchers to seek a safer, more cost-effective, patient-friendly, and effective method that does not develop antibiotic resistance. With progress in synthetic biology and genetic engineering, genetically engineered microorganisms effective in treatment, prophylaxis, drug delivery, and diagnosis have been developed. The present study reviews the types of genetically engineered bacteria and phages, their impacts on diseases, cancer, and metabolic and inflammatory disorders, the biosynthesis of these modified strains, the route of administration, and their effects on the environment. We conclude that genetically engineered microorganisms can be considered promising candidates for adjunctive treatment of diseases and cancers.

A review on edible vaccines and their prospects

For a long time, vaccines have been the main mode of defense and protection against several bacterial, viral, and parasitic diseases. However, the process of production and purification makes them expensive and unaffordable to many developing nations. An edible vaccine is when the antigen is expressed in the edible part of the plant. This reduces the cost of production of the vaccine because of ease of culturing. In this article, various types of edible vaccines that include algal and probiotics in addition to plants are discussed. Various diseases against which research has been carried out are also reviewed. This article focused on the conception of edible vaccines highlighting the various ways by which vaccines can be delivered.

Engineering of a rough auxotrophic mutant Salmonella Typhimurium for effective delivery

Live Salmonella vaccine vectors offer a remarkable platform for delivering immunogens and therapeutic molecules by mimicking natural intracellular infections; however, pre-existing anti-vector immunity can impede effective deployment. Measures to alleviate pre-existing immunity include the use of heterologous vectors, development of highly attenuated strain enabling greater payload, removal of major immunoreactive components from the vector, and/or augmentation of delivered antigens via increased presentation in antigen presenting cells. Here we report a Salmonella Typhimurium (ST) vector-JOL1800 that embodies these requisite properties. JOL1800 is a highly attenuated, auxotrophic, and O-antigen deficient rough-mutant strain. Heterologous bacterial and viral antigens were expressed and delivered using JOL1800 in mice, irrespective of the inoculation route successful inductions of the mucosal and systemic humoral responses were observed. Compared to smooth LPS vector delivery, we observed an increased fraction of delivered-antigen presenting dendritic cells and a higher frequency of delivered-antigen displayed per macrophage. Upon post-priming with JOL1800 delivery, efficacy of the delivery was minimally affected as indicated by insignificant decrease in colonization, humoral and cellular responses. Our results show that the generated vector is capable of remote antigen delivery, manifests higher antigen presentation, is Differentiating Infected from Vaccinated Animals (DIVA) capable, evades normal pre-existing immunity, and can be deployed for effective delivery.

Reductions in human Lyme disease risk due to the effects of oral vaccination on tick-to-mouse and mouse-to-tick transmission

Vaccinating wildlife is becoming an increasingly popular method to reduce human disease risks from pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. To successfully limit human disease risk, vaccines targeting the wildlife reservoirs of B. burgdorferi must be easily distributable and must effectively reduce pathogen transmission from infected animals, given that many animals in nature will be infected prior to vaccination. We assessed the efficacy of an easily distributable oral bait vaccine based on the immunogenic outer surface protein A (OspA) to protect uninfected mice from infection and to reduce transmission from previously infected white-footed mice, an important reservoir host of B. burgdorferi. Oral vaccination of white-footed mice effectively reduces transmission of B. burgdorferi at both critical stages of the Lyme disease transmission cycle. First, oral vaccination of uninfected white-footed mice elicits an immune response that protects mice from B. burgdorferi infection. Second, oral vaccination of previously infected mice significantly reduces the transmission of B. burgdorferi to feeding ticks despite a statistically nonsignificant immune response. We used the estimates of pathogen transmission to and from vaccinated and unvaccinated mice to model the efficacy of an oral vaccination campaign targeting wild white-footed mice. Projection models suggest that the effects of the vaccine on both critical stages of the transmission cycle of B. burgdorferi act synergistically in a positive feedback loop to reduce the nymphal infection prevalence, and thus human Lyme disease risk, well below what would be expected from either effect alone. This study suggests that oral immunization of wildlife with an OspA-based vaccine can be a promising long-term strategy to reduce human Lyme disease risk.

Reservoir targeted vaccine for lyme borreliosis induces a yearlong, neutralizing antibody response to OspA in white-footed mice

Lyme disease is caused by the spirochete Borrelia burgdorferi. The enzootic cycle of this pathogen requires that Ixodes spp. acquire B. burgdorferi from infected wildlife reservoirs and transmit it to other uninfected wildlife. At present, there are no effective measures to control B. burgdorferi; there is no human vaccine available, and existing vector control measures are generally not acceptable to the public. However, if B. burgdorferi could be eliminated from its reservoir hosts or from the ticks that feed on them, the enzootic cycle would be broken, and the incidence of Lyme disease would decrease. We developed OspA-RTV, a reservoir targeted bait vaccine (RTV) based on the immunogenic outer surface protein A (OspA) of B. burgdorferi aimed at breaking the natural cycle of this spirochete. White-footed mice, the major reservoir species for this spirochete in nature developed a systemic OspA-specific IgG response as a result of ingestion of the bait formulation. This immune response protected white-footed mice against B. burgdorferi infection upon tick challenge and cleared B. burgdorferi from the tick vector. In performing extensive studies to optimize the OspA-RTV for field deployment, we determined that mice that consumed the vaccine over periods of 1 or 4 months developed a yearlong, neutralizing anti-OspA systemic IgG response. Furthermore, we defined the minimum number of OspA-RTV units needed to induce a protective immune response.

Adjuvant effects for oral immunization provided by recombinant Lactobacillus casei secreting biologically active murine interleukin-1{beta}

Vaccine delivery systems using lactic acid bacteria are under development, but their efficiency is insufficient. Autologous cytokines, such as interleukin-1beta (IL-1beta), are potential adjuvants for mucosal vaccines and can be provided by recombinant lactic acid bacteria. The aim of this study was the construction and evaluation of recombinant Lactobacillus casei producing IL-1beta as an adjuvant delivery agent. The recombinant strain was constructed using an expression/secretion vector plasmid, including a mature IL-1beta gene from mouse. The biological activity of the cytokine was confirmed by IL-8 production from Caco-2 cells. In response to the recombinant L. casei secreting IL-1beta, expression of IL-6 was detected in vivo using a ligated-intestinal-loop assay. The release of IL-6 from Peyer's patch cells was also detected in vitro. Intragastric immunization with heat-killed Salmonella enterica serovar Enteritidis (SE) in combination with IL-1beta-secreting lactobacilli resulted in relatively high SE-specific antibody production. In this study, it was demonstrated that recombinant L. casei secreting bioactive murine IL-1beta provided adjuvant effects for intragastric immunization.

Strategies for successful recombinant expression of disulfide bond-dependent proteins in Escherichia coli

Bacteria are simple and cost effective hosts for producing recombinant proteins. However, their physiological features may limit their use for obtaining in native form proteins of some specific structural classes, such as for instance polypeptides that undergo extensive post-translational modifications. To some extent, also the production of proteins that depending on disulfide bridges for their stability has been considered difficult in E. coli.

Both eukaryotic and prokaryotic organisms keep their cytoplasm reduced and, consequently, disulfide bond formation is impaired in this subcellular compartment. Disulfide bridges can stabilize protein structure and are often present in high abundance in secreted proteins. In eukaryotic cells such bonds are formed in the oxidizing environment of endoplasmic reticulum during the export process. Bacteria do not possess a similar specialized subcellular compartment, but they have both export systems and enzymatic activities aimed at the formation and at the quality control of disulfide bonds in the oxidizing periplasm.

This article reviews the available strategies for exploiting the physiological mechanisms of bactera to produce properly folded disulfide-bonded proteins.

Differential expression of the Bhmp39 major outer membrane proteins of Brachyspira hyodysenteriae

The enteric, anaerobic spirochete Brachyspira hyodysenteriae is the causative agent of swine dysentery, a severe mucohemorrhagic diarrheal disease of pigs that has economic significance in every major pork-producing country. Recent investigation into potential vaccine candidates has focused on the outer membrane proteins of B. hyodysenteriae. Bhmp39 (formerly Vsp39) is the most abundant surface-exposed outer membrane protein of B. hyodysenteriae; its predicted gene sequence has previously been shown to share sequence similarity to eight genes divided evenly between two paralogous loci. The peptide sequence suggested that Bhmp39 is encoded by one of these genes, bhmp39h. The biological significance of maintaining eight homologous bhmp39 genes is unclear, though it has been proposed that this may play a role in antigenic variation. In this study, real-time, reverse transcription-PCR was used to demonstrate that bhmp39f and bhmp39h were the transcripts most abundantly expressed by B. hyodysenteriae strain B204 cultured under in vitro growth conditions. Mass spectrometry data of the purified 39-kDa membrane protein showed that both Bhmp39f and Bhmp39h were present. Northern blot analysis across predicted Rho-independent terminators demonstrated that the genes of the bhmp39efgh locus result in monocistronic transcripts.

Protective efficacy of an oral vaccine to reduce carriage of Borrelia burgdorferi (strain N40) in mouse and tick reservoirs

Lyme disease is caused by the spirochete Borrelia burgdorferi, which is transmitted through the bite of infected Ixodes ticks. Vaccination of mice with outer surface protein A (OspA) of B. burgdorferi has been shown to both protect mice against B. burgdorferi infection and reduce carriage of the organism in feeding ticks. Here we report the development of a murine-targeted OspA vaccine utilizing Vaccinia virus to interrupt transmission of disease in the reservoir hosts, thus reducing incidence of human disease. Oral vaccination of mice with a single dose of Vaccinia expressing OspA resulted in high antibody titers to OspA, 100% protection of vaccinated mice from infection with B. burgdorferi, and significant clearance of B. burgdorferi from infected ticks fed on vaccinated animals. The results indicate the vaccine is effective and may provide a manner to reduce incidence of Lyme disease.

Oral vaccine that breaks the transmission cycle of the Lyme disease spirochete can be delivered via bait

Borrelia burgdorferi causes Lyme disease, a potentially debilitating human disease for which no vaccine is currently available. We developed an oral bait delivery system for an anti-B. burgdorferi vaccine based in OspA. Mice were immunized orally via gavage and bait feeding. Challenge was performed via Ixodes scapularis field nymphs carrying multiple B. burgdorferi strains. Vaccination protected 89% of the mice and the systemic immune response was skewed toward IgG2a/2b production. Moreover, this oral vaccine reduced the pathogen in the tick vector by eight-fold. We conclude that this oral vaccine induces a protective systemic immune response against a variety of infectious B. burgdorferi strains found in nature and therefore it can eliminate this zoonotic pathogen from its major host reservoirs. Because we observed elimination of the spirochete from the tick vector, a broad delivery of this oral vaccine to wildlife reservoirs is likely to disrupt the transmission cycle of this pathogen.

Salmonella: immune responses and vaccines

Salmonella infections are a serious medical and veterinary problem world-wide and cause concern in the food industry. Vaccination is an effective tool for the prevention of Salmonella infections. Host resistance to Salmonella relies initially on the production of inflammatory cytokines leading to the infiltration of activated inflammatory cells in the tissues. Thereafter T- and B-cell dependent specific immunity develops allowing the clearance of Salmonella microorganisms from the tissues and the establishment of long-lasting acquired immunity to re-infection. The increased resistance that develops after primary infection/ vaccination requires T-cells cytokines such as IFNgamma TNFalpha and IL12 in addition to opsonising antibody. However for reasons that are not fully understood seroconversion and/or the presence of detectable T-cell memory do not always correlate with the development of acquired resistance to infection.Whole-cell killed vaccines and subunit vaccines are used in the prevention of Salmonella infection in animals and in humans with variable results. A number of early live Salmonella vaccines derived empirically by chemical or u.v. mutagenesis proved to be immunogenic and protective and are still in use despite the need for repeated parenteral administration. Recent progress in the knowledge of the genetics of Salmonella virulence and modern recombinant DNA technology offers the possibility to introduce multiple defined attenuating and irreversible mutations into the bacterial genome. This has recently allowed the development of Salmonella strains devoid of significant side effects but still capable of inducing solid immunity after single oral administration. Live attenuated Salmonella vaccines have been used for the expression of heterologous antigens/proteins that can be successfully delivered to the immune system. Furthermore Salmonella can transfer plasmids encoding foreign antigens under the control of eukaryotic promoters (DNA vaccines) to antigen-presenting cells resulting in targeted delivery of DNA vaccines to these cells. Despite the great recent advances in the development of Salmonella vaccines a large proportion of the work has been conducted in laboratory rodents and more research in other animal species is required.

Elicitation of predictable immune responses by using live bacterial vectors

There is an increasing need for novel vaccines able to stimulate efficient and long-lasting responses, which have also low production costs. To confer protective immunity following vaccination, the adequate type of response should be elicited. Vaccines based on attenuated bacterial carriers have contained production and delivery costs, and are able to stimulate more potent immune responses than non-replicating formulations. The improved knowledge on carrier physiology and host response, the availability of different mutants and highly sophisticated expression tools, and the possibility of co-administering modulators enable to trigger predictable responses according to the specific needs. Recent studies support the use of attenuated bacteria not only as conventional carriers, but also as a delivery system for DNA vaccines against infectious agents and tumors. In this review we discuss the most widely used bacterial carrier systems for either antigens or nucleic acid vaccines, and the strategies which have been successfully exploited to modulate the immune responses elicited.

Use of live bacterial vaccine vectors for antigen delivery: potential and limitations

Most infectious agents are restricted to the mucosal membranes or their transit through the mucosa constitutes a critical step in the infection process. Therefore, the elicitation of an efficient immune response, not only at systemic, but also at mucosal level, after vaccination is highly desirable, representing a significant advantage in order to prevent infection. This goal can be only achieved, when the vaccine formulation is administered by the mucosal route. However, soluble antigens given by this route are usually poorly immunogenic. Among the available approaches to stimulate efficient mucosal responses, the use of bacterial carriers to deliver vaccine antigens, probably, constitutes one of the most successful strategies. The potential and limitations of the most extensively studied bacterial carrier systems will be discussed.

Surface-displayed viral antigens on Salmonella carrier vaccine

We have developed a recombinant live oral vaccine using the ice-nucleation protein (Inp) from Pseudomonas syringae to display viral antigens on the surface of Salmonella spp. Fusion proteins containing viral antigens were expressed in the oral vaccine strain, Salmonella typhi Ty21a. Surface localization was verified by immunoblotting and fluorescence-activated cell sorting. The immunogenicity of surface-displayed viral antigens on the recombinant live vaccine strain was assessed in mice inoculated intranasally and intraperitoneally. Inoculation resulted in significantly higher serum antibody level than those induced by viral antigens expressed intracellularly. Thus, this multivalent mucosal live vaccine may provide an effective means for inducing mucosal or systemic immune responses against multiple viral antigens.

Murine immune responses to mucosally delivered Salmonella expressing Lassa fever virus nucleoprotein

Arenaviruses are emerging pathogens known to infect via the mucosa, however no formal attempts to make mucosal vaccines have been undertaken. Here we describe a recombinant aroA attenuated Salmonella typhimurium that expresses the nucleoprotein (NP) gene of Lassa fever virus (LAS). The complete NP gene was cloned downstream of the bacterial groEL promotor and integrated into the aroA locus of S. typhimurium. Lassa NP protein was detected in whole cell extracts from the recombinant Salmonella by immunoblot analysis with serum from Lassa-infected people. Mice were inoculated by intragastric intubation with 5 x 10(9) S. typhimurium and boosted with the same recombinant Salmonella 21 days after the primary inoculation. Both local mucosal IgA and serum immunoglobulins against Lassa NP were observed. Splenic cytotoxic T-lymphocyte responses to LAS NP were detected after the boost and they cross-reacted with target cells infected with the related arenavirus, lymphocytic choriomeningitis virus. Recombinant Salmonella elicits humoral and cell mediated immune responses against Lassa fever virus in mice and should be considered as a potential vaccine strategy in man.

Recombinant, attenuated Salmonella typhimurium stimulate lymphoproliferative responses to SIV capsid antigen in rhesus macaques

Recombinant bacteria are useful vectors for delivering foreign antigens to mucosal surfaces and may elicit immune protection against sexually-transmitted pathogens. Recombinant, attenuated Salmonella typhimurium expressing the Simian Immunodeficiency Virus capsid protein (p27) were given to rhesus macaques by intragastric intubation. This route of immunization was compared with intramuscular injection of soluble p27 in adjuvant, and with immunization protocols that combined intragastric and intramuscular antigen exposures. Recombinant Salmonella stimulated p27-specific lymphoproliferative responses that were present transiently in peripheral blood, and were recalled easily by booster immunizations. Intramuscular p27 injection elicited strong serum antibody responses, but only low level capsid-specific proliferative responses. Recombinant Salmonella immunization elicited low levels of p27-specific antibodies in serum and did not suppress subsequent responses to parenteral immunization. Intragastric immunization of macaques with recombinant Salmonella typhimurium was safe and induced immune responses specific for the expressed, foreign antigen.

A new membrane-bound OprI lipoprotein expression vector. High production of heterologous fusion proteins in gram (-) bacteria and the implications for oral vaccination

We have previously described the development of cloning vectors for the production of OprI-based outer membrane fusion proteins in E. coli (Cornelis et al., 1996) and now describe the construction of a new vector, containing a lacI(q) gene, resulting in tight repression of the promotor and allowing its use in other Gram (-) bacteria. The new pVUB3 expression vector encodes a truncated but active LacI(q)(341) repressor which binds to the single operator in the vector. A high repression of the trc promotor was observed, resulting in a very low basal leakage of expression and very high production levels of OprI or derivatives after IPTG induction in E. coli. Bacterial viability was not affected under uninduced conditions, but the number of viable cell counts decreased after production of large amounts of the outer membrane-bound OprI lipoprotein and its derivatives, both in E. coli and Salmonella typhimurium. This highly repressible system allows us to extend the use of OprI vectors in other Gram (-) bacteria, resulting in the production of outer membrane-bound lipid-modified molecules, opening the possibility for its application in the design of potential live Salmonella-based subunit vaccines.

Immunisation with live attenuated Salmonella dublin expressing a sporozoite protein confers partial protection against Theileria parva

Cattle immunised with a recombinant form of p67, the major surface antigen of Theileria parva sporozoites, have been shown to be protected against parasite challenge. In an attempt to simplify the immunisation procedure live attenuated Salmonella strains expressing p67 have been constructed and used to induce anti-p67 immune responses in cattle. All animals immunised with these strains developed strong antibody responses to p67. Specific T cell responses could be detected in the majority of immunised cattle. Challenge with T. parva sporozoites revealed a significant level of protection in immunised calves compared to naive control animals or animals inoculated with non-recombinant attenuated Salmonella.

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.

Oral delivery of purified lipoprotein OspA protects mice from systemic infection with Borrelia burgdorferi

The lipoprotein outer surface protein A (OspA) of the Lyme disease agent. Borrelia burgdorferi, has provided protection to mice and other animals against systemic infection when delivered orally as a recombinant protein in Escherichia coli, bacille Calmette. Guerin or Salmonella typhimurium. In the present study purified recombinant strain B31 OspA or outer surface protein D (OspD), another lipoprotein of B. burgdorferi, were administered either subcutaneously (s.c.) or orally without cell carrier or adjuvant to mice. In comparison to the OspD preparation, the OspA protein was 256-fold more resistant to trypsin. Whereas OspA in the suspension was in regular complexes of 17-25 nm in size, OspD formed amorphous globules of different sizes. Animals received a primary immunization and at least one booster. Mice immunized s.c. with either OspA or OspD had detectable antibodies to B. burgdorferi by enzyme-linked immunosorbent assay (ELISA), growth inhibition assay (GIA) and immunoblot. Delivered orally, OspA but not OspD elicited a specific antibody response, including IgA, as determined by these assays. The geometric mean titre of sera from mice who received 4 micrograms of OspA orally on days 1, 2, 4, 21 and 22 was 1470 by Ig ELISA, 320 by IgA ELISA and 128 by GIA. In infectious challenge experiments with B. burgdorferi strain Sh2-2-82 (OspA+ OspD- ) inoculated intradermally at 100 x the ID 50 all eight mice immunized with the 4 micrograms dose of OspA were protected, none of the mice immunized with the 4 micrograms dose of OspD were protected (P < 0.001 by Fisher exact test). These studies indicate that the lipoprotein OspA provides protection against systemic B. burgdorferi infection when delivered orally as a purified protein.

Display of heterologous proteins on the surface of microorganisms: from the screening of combinatorial libraries to live recombinant vaccines

In recent years there has been considerable progress towards the development of expression systems for the display of heterologous polypeptides and, to a lesser extent, oligosaccharides on the surface of bacteria or yeast. The availability of protein display vectors has in turn provided the impetus for a range of exciting technologies. Polypeptide libraries can be displayed in bacteria and screened by cell sorting techniques, thus simplifying the isolation of proteins with high affinity for ligands. Expression of antigens on the surface of nonvirulent microorganisms is an attractive approach to the development of high-efficacy recombinant live vaccines. Finally, cells displaying protein receptors or antibodies are of use for analytical applications and bioseparations.

Immunity to Lyme disease: protection, pathology and persistence

Persistence of the Lyme disease spirochete, Borrelia burgdorferi, in the presence of an active immune response has been well documented. Evidence from the past year indicates that modulation of surface antigens by the spirochete may be a major mechanism for evading the immune response.

Outer surface protein C (OspC), but not P39, is a protective immunogen against a tick-transmitted Borrelia burgdorferi challenge: evidence for a conformational protective epitope in OspC

Outbred mice were immunized with the soluble fraction of a crude Escherichia coli lysate containing either recombinant outer surface protein C (OspC or P39 of Borrelia burgdorferi B31 (low passage). Following seroconversion, the mice were challenged with an infectious dose of B. burgdorferi B31 via the natural transmission mode of tick bite. Three mice immunized with P39 were not protected; however, all 12 of the recombinant OspC-immunized mice were protected from infection as assayed by culture and serology. Although OspC has been shown to be a protective immunogen against challenge with in vitro-cultured borrelia administered by needle, this study is the first to demonstrate OspC effectiveness against tick-borne spirochetes. Following feeding, all ticks still harbored B. burgdorferi, suggesting that the mechanism of protection is not linked to destruction of the infectious spirochete within the tick. In a separate experiment, groups of four mice were immunized with protein fractions from B. burgdorferi B31 purified by preparative gel electrophoresis in an attempt to identify potential protective antigens. Many of these mice developed high-titer-antibody responses against OspC, but curiously the mice were susceptible to B. burgdorferi infection via tick bite. These results suggest that the protective epitope(s) on OspC is heat sensitive/conformational, a finding which has implications in vaccine development.

Experimental immunization against Lyme borreliosis with recombinant Osp proteins: an overview

Interest in human and veterinary vaccines against Lyme borreliosis is growing. Both whole cell immunization and subunit vaccines can protect against infection with Borrelia burgdorferi. For development of a human vaccine the focus has been on a subunit vaccine. The most promising candidate is OspA, a major outer membrane lipoprotein of B. burgdorferi sensu lato. Of Osp proteins A through D, OspA shows the least variability between strains in its sequence and in the level of its expression. Borreliae in ticks express OspA. Antibodies to OspA kill borreliae in vitro and provide passive protection in mice. Active immunization of mice with OspA provides protection against challenge by syringe inoculation or tick bite. The lipid moiety of the OspA is necessary for immunogenicity in the absence of a potent adjuvant. A recombinant OspA-based vaccine is already in clinical trials. Although there is compelling evidence that immunization with OspA will provide protection, questions remain regarding the duration of protection from such immunization, the necessity to have a minimum level of neutralizing antibodies at all times for protection, and the relationship of an immune response to OspA and autoimmune features of Lyme borreliosis. The experimental aspects of immunization with Osp-A based constructs and other Lyme vaccine candidates are reviewed and discussed.

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.