VANGUARD®crLyme: A next generation Lyme disease vaccine that prevents B. burgdorferi infection in dogs

Fourteen anti-tick vaccine targets are variably conserved in cattle fever ticks

BACKGROUND

Rhipicephalus (Boophilus) microplus causes significant cattle production losses worldwide because it transmits Babesia bovis and B. bigemina, the causative agents of bovine babesiosis. Control of these ticks has primarily relied on treatment of cattle with chemical acaricides, but frequent use, exacerbated by the one-host lifecycle of these ticks, has led to high-level resistance to multiple classes of acaricides. Consequently, new approaches for control, such as anti-tick vaccines, are critically important. Key to this approach is targeting highly conserved antigenic epitopes to reduce the risk of vaccine escape in heterologous tick populations.

METHODS

We evaluated amino acid conservation within 14 tick proteins across 167 R. microplus collected from geographically diverse locations in the Americas and Pakistan using polymerase chain reaction (PCR) amplicon sequencing and in silico translation of exons.

RESULTS

We found that amino acid conservation varied considerably across these proteins. Only the voltage-dependent anion channel (VDAC) was fully conserved in all R. microplus samples (protein similarity 1.0). Four other proteins were highly conserved: the aquaporin RmAQP1 (0.989), vitellogenin receptor (0.985), serpin-1 (0.985), and subolesin (0.981). In contrast, the glycoprotein Bm86 was one of the least conserved (0.889). The Bm86 sequence used in the original Australian TickGARD vaccine carried many amino acid replacements compared with the R. microplus populations examined here, supporting the hypothesis that this vaccine target is not optimal for use in the Americas. By mapping amino acid replacements onto predicted three-dimensional (3D) protein models, we also identified amino acid changes within several small-peptide vaccines targeting portions of the aquaporin RmAQP2, chitinase, and Bm86.

CONCLUSIONS

These findings emphasize the importance of thoroughly analyzing protein variation within anti-tick vaccine targets across diverse tick populations before selecting candidate vaccine antigens. When considering protein conservation alone, RmAQP1, vitellogenin receptor, serpin-1, subolesin, and especially VDAC rank as high-priority anti-tick vaccine candidates for use in the Americas and perhaps globally.

Novel recombinant vaccinia virus-vectored vaccine affords complete protection against homologous Borrelia burgdorferi infection in mice

The rising prevalence of Lyme disease (LD) in North America and Europe has emerged as a pressing public health concern. Despite the availability of veterinary LD vaccines, no vaccine is currently available for human use. Outer surface protein C (OspC) found on the outer membrane of the causative agent, Borrelia burgdorferi, has been identified as a promising target for LD vaccine development due to its sustained expression during mammalian infection. However, the efficacy and immunological mechanisms of LD vaccines solely targeting OspC are not well characterized. In this study, we developed an attenuated Vaccinia virus (VV) vectored vaccine encoding type A OspC (VV-OspC-A). Two doses of the VV-OspC-A vaccine conferred complete protection against homologous B. burgdorferi challenge in mice. Furthermore, the candidate vaccine also prevented the development of carditis and lymph node hyperplasia associated with LD. When investigating the humoral immune response to vaccination, VV-OspC-A was found to induce a robust antibody response predominated by the IgG2a subtype, indicating a Th1-bias. Using a novel quantitative flow cytometry assay, we also determined that elicited antibodies were capable of inducing antibody-dependent cellular phagocytosis in vitro. Finally, we demonstrated that VV-OspC-A vaccination generated a strong antigen-specific CD4+ T-cell response characterized by the secretion of numerous cytokines upon stimulation of splenocytes with OspC peptides. This study suggests a promising avenue for LD vaccine development utilizing viral vectors targeting OspC and provides insights into the immunological mechanisms that confer protection against B. burgdorferi infection.

A single immunization of Borreliella burgdorferi-infected mice with Vanguard crLyme elicits robust antibody responses to diverse strains and variants of outer surface protein C

Lyme disease, caused by Borreliella burgdorferi and related species, is a growing health threat to companion animals across North America and Europe. Vaccination is an important preventive tool used widely in dogs living in, or near, endemic regions. In this report, we assessed anti-outer surface protein (Osp) A and anti-OspC antibody responses in B. burgdorferi-infected and -naïve mice (C3H/HeN) after immunization with a murine-optimized single dose of the Lyme disease subunit vaccine, Vanguard crLyme. crLyme is comprised of OspA and an OspC chimeritope-based immunogen designated as CH14. Mice that were infected and immunized developed higher levels of anti-OspC antibodies (Abs) than those infected only or that received one vaccine dose. The anti-OspC Abs that developed in the infected/immunized mice bound to all OspC variants tested (n = 22), whereas OspC Abs in serum from infected mice bound predominantly to the OspC variant (type A) produced by the infecting B. burgdorferi strain. Consistent with the absence of OspA expression in infected mammals, none of the infected mice developed Abs to OspA and did not develop anti-OspA Abs after single dose immunization. Lastly, serum from infected/immunized mice displayed significantly higher and broader killing activity than serum from non-immunized infected mice. The results of this study demonstrate that a single vaccination of actively infected mice results in strong anti-OspC Ab responses. This study contributes to our understanding of Ab responses to vaccination in actively infected mammals.

2022 AAHA Canine Vaccination Guidelines (2024 Update)

Vaccination is a cornerstone of canine preventive healthcare and one of the most cost-effective ways of maintaining a dog's health, longevity, and quality of life. Canine vaccination also serves a public health function by forming a barrier against several zoonotic diseases affecting dogs and humans. Canine vaccines are broadly categorized as containing core and noncore immunizing antigens, with administration recommendations based on assessment of individual patient risk factors. The guidelines include a comprehensive table listing canine core and noncore vaccines and a recommended vaccination and revaccination schedule for each vaccine. The guidelines explain the relevance of different vaccine formulations, including those containing modified-live virus, inactivated, and recombinant immunizing agents. Factors that potentially affect vaccine efficacy are addressed, including the patient's prevaccination immune status and vaccine duration of immunity. Because animal shelters are one of the most challenging environments for prevention and control of infectious diseases, the guidelines also provide recommendations for vaccination of dogs presented at or housed in animal shelters, including the appropriate response to an infectious disease outbreak in the shelter setting. The guidelines explain how practitioners can interpret a patient's serological status, including maternally derived antibody titers, as indicators of immune status and suitability for vaccination. Other topics covered include factors associated with postvaccination adverse events, vaccine storage and handling to preserve product efficacy, interpreting product labeling to ensure proper vaccine use, and using client education and healthcare team training to raise awareness of the importance of vaccinations.

Development of novel multi-protein chimeric immunogens that protect against infection with the Lyme disease agent, Borreliella burgdorferi

Lyme disease is the most common tick-borne disease in North America. A vaccine for use in humans is not available. Here, we detail the development of two chimeric vaccine antigens, BAF and Chv2M. BAF elicits Abs that target proteins and protein variants produced by Borreliella species in ticks (OspB and OspA) and mammals (FtlA/B). OspB serves as the backbone structure for the BAF chimeric. Two OspA221-240 epitope-containing domain (ECD) variants (#A1 and #A15) were inserted into a loop in OspB. The N-terminal region of the FtlA protein was joined to the C-terminus of the chimeric. The second chimeric, Chv2M, consists of L5 (loop 5) and H5 (helix 5) ECDs derived from diverse OspC proteins. Borreliella species produce OspC upon exposure to the bloodmeal and during early infection in mammals. Here, we demonstrate that BAF and Chv2M are potent immunogens that elicit Abs that bind to each component protein (FtlA, FtlB, OspB, and multiple OspA and OspC variants). Anti-BAF and anti-Chv2M Abs kill Borreliella burgdorferi strains through Ab-mediated complement-dependent and complement-independent mechanisms. Eighty percent (32/40) of mice that received a three-dose vaccine regimen were protected from infection with B. burgdorferi B31. Efficacy increased to 90% (18/20) when the amount of Chv2M was increased in the third vaccine dose. Readouts for infection were flaB PCR and seroconversion to VlsE. This study establishes proof of principle for a chimeric immunogen vaccine formulation that elicits Abs to multiple targets on the B. burgdorferi cell surface produced during tick and mammalian stages of the enzootic cycle.IMPORTANCELyme disease is a growing public health threat across parts of the Northern Hemisphere. Regions that can support sustained tick populations are expanding, and the incidence of tick-borne diseases is increasing. In light of the increasing risk of Lyme disease, effective preventive strategies are needed. Most vaccine development efforts have focused on outer surface protein A, a Borreliella burgdorferi protein produced only in ticks. Herein, we describe the development of a novel vaccine formulation consisting of two multivalent chimeric proteins that are immunogenic and elicit antibodies with bactericidal activity that target several cell surface proteins produced by the Lyme disease spirochetes in feeding ticks and mammals. In a broader sense, this study advances efforts to develop custom-designed vaccinogens comprised of epitope-containing domains from multiple proteins.

Current and emerging approaches for eliminating Borrelia burgdorferi and alleviating persistent Lyme disease symptoms

Lyme disease is the most prevalent tick-borne infection caused by Borrelia burgdorferi bacteria in North America. Other Borrelia species are predominately the cause of this disease in Eurasia with some distinct and various overlapping manifestations. Consequently, caution must be exercised when comparing the disease and its manifestations and treatment regimens in North America and Europe. Diagnosis of the early Lyme disease remains difficult using the currently FDA approved serological tests in the absence of a reported tick bite or of erythema migrans in many individuals, non-specific initial symptoms, and the absence of detectable anti-Borrelia antibodies in the prepatent period of infection. Furthermore, it is difficult to distinguish persistence of infection and disease versus reinfection in the endemic regions of Lyme disease by serological assays. If early infection remains untreated, spirochetes can disseminate and could affect various organs in the body with a variety of disease manifestations including arthralgias and musculoskeletal pain, neurologic symptoms and anomalies, and acrodermatitis chronicum atrophicans (ACA) in Europe. Although most patients recover after antibiotic treatment, an estimated ∼10-20% patients in the United States show persistence of symptoms known as post-treatment Lyme disease syndrome (PTLDS). The causes and biomarkers of PTLDS are not well-defined; however, several contributing factors with inconsistent degree of supporting evidence have been suggested. These include antigenic debris, dysregulation of immunological response, bacterial persisters, or combination of these features. This review highlights currently employed treatment approaches describing different antimicrobials used, and vaccine candidates tried to prevent B. burgdorferi infection.

Borreliella burgdorferi factor H-binding proteins are not required for serum resistance and infection in mammals

The causative agent of Lyme disease (LD), Borreliella burgdorferi, binds factor H (FH) and other complement regulatory proteins to its surface. B. burgdorferi B31 (type strain) encodes five FH-binding proteins (FHBPs): CspZ, CspA, and the OspE paralogs OspEBBN38, OspEBBL39, and OspEBBP38. This study assessed potential correlations between the production of individual FHBPs, FH-binding ability, and serum resistance using a panel of infectious B. burgdorferi clonal populations recovered from dogs. FHBP production was assessed in cultivated spirochetes and by antibody responses in naturally infected humans, dogs, and eastern coyotes (wild canids). FH binding specificity and sensitivity to dog and human serum were also assessed and compared. No correlation was observed between the production of individual FHBPs and FH binding with serum resistance, and CspA was determined to not be produced in animals. Notably, one or more clones isolated from dogs lacked CspZ or the OspE proteins (a finding confirmed by genome sequence determination) and did not bind FH derived from canines. The data presented do not support a correlation between FH binding and the production of individual FHBPs with serum resistance and infectivity. In addition, the limited number and polymorphic nature of cp32s in B. burgdorferi clone DRI85A that were identified through genome sequencing suggest no strict requirement for a defined set of these replicons for infectivity. This study reveals that the immune evasion mechanisms employed by B. burgdorferi are diverse, complex, and yet to be fully defined.

The Development of a Rabies Virus-Vectored Vaccine against Borrelia burgdorferi, Targeting BBI39

Lyme disease (LD) is the most common tick-borne illness in the United States (U.S.), Europe, and Asia. Borrelia burgdorferi, a spirochete bacterium transmitted by the tick vector Ixodes scapularis, causes LD in the U.S. If untreated, Lyme arthritis, heart block, and meningitis can occur. Given the absence of a human Lyme disease vaccine, we developed a vaccine using the rabies virus (RABV) vaccine vector BNSP333 and an outer surface borrelial protein, BBI39. BBI39 was previously utilized as a recombinant protein vaccine and was protective in challenge experiments; therefore, we decided to utilize this protective antigen in a rabies virus-vectored vaccine against Borrelia burgdorferi. To incorporate BBI39 into the RABV virion, we generated a chimeric BBI39 antigen, BBI39RVG, by fusing BBI39 with the final amino acids of the RABV glycoprotein by molecular cloning and viral recovery with reverse transcription genetics. Here, we have demonstrated that the BBI39RVG antigen was incorporated into the RABV virion via immunofluorescence and Western blot analysis. Mice vaccinated with our BPL inactivated RABV-BBI39RVG (BNSP333-BBI39RVG) vaccine induced high amounts of BBI39-specific antibodies, which were maintained long-term, up to eight months post-vaccination. The BBI39 antibodies neutralized Borrelia in vaccinated mice when challenged with Borrelia burgdorferi by either syringe injection or infected ticks and they reduced the Lyme disease pathology of arthritis in infected mouse joints. Overall, the RABV-based LD vaccine induced more and longer-term antibodies compared to the recombinant protein vaccine. This resulted in lower borrelial RNA in RABV-based vaccinated mice compared to recombinant protein vaccinated mice. The results of this study indicate the successful use of BBI39 as a vaccine antigen and RABV as a vaccine vector for LD.

The leptospiral OmpA-like protein (Loa22) is a surface-exposed antigen that elicits bactericidal antibody against heterologous Leptospira

Leptospirosis is the most widespread zoonosis, affecting over 1 million humans each year, with more than 60,000 deaths worldwide. Leptospirosis poses a significant health threat to dogs, horses, cattle, and wildlife. The disease may be self-limiting or progress to a life-threatening multi-system disorder affecting the kidneys, liver, and lungs. Currently, bacterin vaccine formulations that consist of one or more laboratory-cultivated strains are used for prevention. However, the antibody response elicited by these vaccines is directed primarily at lipopolysaccharide and is generally serovar-specific. The development of broadly protective subunit vaccines for veterinary and human applications would be a significant step forward in efforts to combat this emerging and antigenically variable pathogen. This study assessed the properties and potential utility of the Leptospira Loa22 (Leptospira OmpA-like 22 kDa protein) protein as a vaccine antigen. Loa22 is a virulence factor that is predicted to transverse the outer membrane and present its N-terminal domain on the cell surface. This report demonstrates that diverse Leptospira strains express Loa22 in vitro and that the protein is antigenic during infection in dogs. Immunoblot and size exclusion chromatography revealed that Loa22 exists in monomeric and trimeric forms. Immunization of rats with recombinant Loa22 elicited bactericidal antibodies against diverse Leptospira strains. The immunodominant bactericidal epitopes were localized within the N-terminal domain using protein-blocking bactericidal assays. This study supports the utility of Loa22, or subfragments thereof, in developing a multivalent chimeric subunit vaccine to prevent leptospirosis and sheds new light on the cellular localization of Loa22.

Efficacy and Immune Correlates of OMP-1B and VirB2-4 Vaccines for Protection of Dogs from Tick Transmission of Ehrlichia chaffeensis

Ehrlichia chaffeensis, an obligatory intracellular bacterium, causes human monocytic ehrlichiosis, an emerging disease transmitted by the Lone Star tick, Amblyomma americanum. Here, we investigated the vaccine potential of OMP-1B and VirB2-4. Among the highly expressed and immunodominant E. chaffeensis porin P28s/OMP-1s, OMP-1B is predominantly expressed by E. chaffeensis in A. americanum ticks, whereas VirB2-4 is a pilus protein of the type IV secretion system essential for E. chaffeensis infection of host cells. Immunization with recombinant OMP-1B (rOMP-1B) or recombinant VirB2-4 (rVirB2-4) protected mice from E. chaffeensis infection as effectively as Entry-triggering protein of Ehrlichia immunization. Dogs vaccinated with a nanoparticle vaccine composed of rOMP-1B or rVirB2-4 and an immunostimulating complex developed high antibody titers against the respective antigen. Upon challenge with E. chaffeensis-infected A. americanum ticks, E. chaffeensis was undetectable in the blood of rOMP-1B or rVirB2-4 immunized dogs on day 3 or 6 post-tick attachment and for the duration of the experiment, whereas dogs sham-vaccinated with the complex alone were persistently infected for the duration of the experiment. E. chaffeensis exponentially replicates in blood-feeding ticks to facilitate transmission. Previously infected ticks removed from OMP-1B-immunized dogs showed significantly lower bacterial load relative to ticks removed from sham-immunized dogs, suggesting in-tick neutralization. Peripheral blood leukocytes from rVirB2-4-vaccinated dogs secreted significantly elevated amounts of interferon-γ soon after tick attachment by ELISpot assay and reverse transcription-quantitative PCR, suggesting interferon-γ-mediated Ehrlichia inhibition. Thus, Ehrlichia surface-exposed proteins OMP-1B and VirB2-4 represent new potential vaccine candidates for blocking tick-borne ehrlichial transmission. IMPORTANCE Ehrlichia are tick-borne pathogens that cause a potentially fatal illness-ehrlichiosis-in animals and humans worldwide. Currently, no vaccine is available for ehrlichiosis, and treatment options are limited. Ticks are biological vectors of Ehrlichia, i.e., Ehrlichia exponentially replicates in blood-sucking ticks before infecting animals. Ticks also inoculate immunomodulatory substances into animals. Thus, it is important to study effects of candidate vaccines on Ehrlichia infection in both animals and ticks and the immune responses of animals shortly after infected tick challenge. Here, we investigated the efficacy of vaccination with functionality-defined two surface-exposed outer membrane proteins of Ehrlichia chaffeensis, OMP-1B and VirB2-4, in a mouse infection model and then in a dog-tick transmission model. Our results begin to fill gaps in our understanding of Ehrlichia-derived protective antigens against tick-transmission and immune correlates and mechanisms that could help future development of vaccines for immunization of humans and animals to counter tick-transmitted ehrlichiosis.

Past, present, and future of Lyme disease vaccines: antigen engineering approaches and mechanistic insights

INTRODUCTION

Transmitted by ticks, Lyme disease is the most common vector-borne disease in the Northern hemisphere. Despite the geographical expansion of human Lyme disease cases, no effective preventive strategies are currently available. Developing an efficacious and safe vaccine is therefore urgently needed. Efforts have previously been taken to identify vaccine targets in the causative pathogen (Borrelia burgdorferi sensu lato) and arthropod vector (Ixodes spp.). However, progress was impeded due to a lack of consumer confidence caused by the myth of undesired off-target responses, low immune responses, a limited breadth of immune reactivity, as well as by the complexities of the vaccine process development.

AREA COVERED

In this review, we summarize the antigen engineering approaches that have been applied to overcome those challenges and the underlying mechanisms that can be exploited to improve both safety and efficacy of future Lyme disease vaccines.

EXPERT OPINION

Over the past two decades, several new genetically redesigned Lyme disease vaccine candidates have shown success in both preclinical and clinical settings and built a solid foundation for further development. These studies have greatly informed the protective mechanisms of reducing Lyme disease burdens and ending the endemic of this disease.

FtlA and FtlB Are Candidates for Inclusion in a Next-Generation Multiantigen Subunit Vaccine for Lyme Disease

Lyme disease (LD) is a tick-transmitted bacterial infection caused by Borreliella burgdorferi and other closely related species collectively referred to as the LD spirochetes. The LD spirochetes encode an uncharacterized family of proteins originally designated protein family twelve (PF12). In B. burgdorferi strain B31, PF12 consists of four plasmid-carried genes, encoding BBK01, BBG01, BBH37, and BBJ08. Henceforth, we designate the PF12 proteins family twelve lipoprotein (Ftl) A (FtlA) (BBK01), FtlB (BBG01), FtlC (BBH37), and FtlD (BBJ08). The goal of this study was to assess the potential utility of the Ftl proteins in subunit vaccine development. Immunoblot analyses of LD spirochete cell lysates demonstrated that one or more of the Ftl proteins are produced by most LD isolates during cultivation. The Ftl proteins were verified to be membrane associated, and nondenaturing PAGE revealed that FtlA, FtlB, and FtlD formed dimers, while FtlC formed hexamers. Analysis of serum samples from B. burgdorferi antibody (Ab)-positive client-owned dogs (n = 50) and horses (n = 90) revealed that a majority were anti-Ftl Ab positive. Abs to the Ftl proteins were detected in serum samples from laboratory-infected dogs out to 497 days postinfection. Anti-FtlA and FtlB antisera displayed potent complement-dependent Ab-mediated killing activity, and epitope localization revealed that the bactericidal epitopes reside within the N-terminal domain of the Ftl proteins. This study suggests that FtlA and FtlB are potential candidates for inclusion in a multivalent vaccine for LD.

2022 AAHA Canine Vaccination Guidelines

These guidelines are an update and extension of previous AAHA peer-reviewed canine vaccination guidelines published in 2017. Vaccination is a cornerstone of canine preventive healthcare and one of the most cost-effective ways of maintaining a dog's health, longevity, and quality of life. Canine vaccination also serves a public health function by forming a barrier against several zoonotic diseases affecting dogs and humans. Canine vaccines are broadly categorized as containing core and noncore immunizing antigens, with administration recommendations based on assessment of individual patient risk factors. The guidelines include a comprehensive table listing canine core and noncore vaccines and a recommended vaccination and revaccination schedule for each vaccine. The guidelines explain the relevance of different vaccine formulations, including those containing modified-live virus, inactivated, and recombinant immunizing agents. Factors that potentially affect vaccine efficacy are addressed, including the patient's prevaccination immune status and vaccine duration of immunity. Because animal shelters are one of the most challenging environments for prevention and control of infectious diseases, the guidelines also provide recommendations for vaccination of dogs presented at or housed in animal shelters, including the appropriate response to an infectious disease outbreak in the shelter setting. The guidelines explain how practitioners can interpret a patient's serological status, including maternally derived antibody titers, as indicators of immune status and suitability for vaccination. Other topics covered include factors associated with postvaccination adverse events, vaccine storage and handling to preserve product efficacy, interpreting product labeling to ensure proper vaccine use, and using client education and healthcare team training to raise awareness of the importance of vaccinations.

Vaccines for Lyme Borreliosis: Facts and Challenges

Lyme borreliosis (LB) is a multisystem infectious disease abundant in the northern countries of the world and is caused by Borrelia species. Vaccination against LB is an effective way to prevent and reduce the number of diseases in endemic areas. Several vaccines have been developed and tested in the past, but no human LB vaccine is currently available on the market. This review aims to uncover and delineate various strategies and diverse technological approaches related to vaccine production. Furthermore, we characterize already tested vaccines, possibilities for their future development, and reasons for their failure.

Recent Progress in Lyme Disease and Remaining Challenges

Lyme disease (also known as Lyme borreliosis) is the most common vector-borne disease in the United States with an estimated 476,000 cases per year. While historically, the long-term impact of Lyme disease on patients has been controversial, mounting evidence supports the idea that a substantial number of patients experience persistent symptoms following treatment. The research community has largely lacked the necessary funding to properly advance the scientific and clinical understanding of the disease, or to develop and evaluate innovative approaches for prevention, diagnosis, and treatment. Given the many outstanding questions raised into the diagnosis, clinical presentation and treatment of Lyme disease, and the underlying molecular mechanisms that trigger persistent disease, there is an urgent need for more support. This review article summarizes progress over the past 5 years in our understanding of Lyme and tick-borne diseases in the United States and highlights remaining challenges.

Comparative analysis of antibody responses to outer surface protein (Osp)A and OspC in dogs vaccinated with Lyme disease vaccines

Lyme disease (LD), the most common tick-borne disease of canines and humans in N. America, is caused by the spirochete Borreliella burgdorferi. Subunit and bacterin vaccines are available for the prevention of LD in dogs. LD bacterin vaccines, which are comprised of cell lysates of two strains of B. burgdorferi, contain over 1000 different proteins and cellular constituents. In contrast, subunit vaccines are defined in composition and consist of either outer surface protein (Osp)A or OspA and an OspC chimeritope. In this study, we comparatively assessed antibody responses to OspA and OspC induced by vaccination with all canine bacterin and subunit LD vaccines that are commercially available in North America. Dogs were administered a two-dose series of the vaccine to which they were assigned (3 weeks apart): Subunit-AC, Subunit-A, Bacterin-1, and Bacterin-2. Antibody titers to OspA and OspC were determined by ELISA and the ability of each vaccine to elicit antibodies that recognize diverse OspC proteins (referred to as OspC types) assessed by immunoblot. While all of the vaccines elicited similar OspA antibody responses, only Subunit-AC triggered a robust and broadly cross-reactive antibody response to divergent OspC proteins. The data presented within provide new information regarding vaccination-induced antibody responses to key tick and mammalian phase antigens by both subunit and bacterin LD canine vaccine formulations.

The Leptospiral General Secretory Protein D (GspD), a secretin, elicits complement-independent bactericidal antibody against diverse Leptospira species and serovars

Leptospirosis, the most common zoonotic infection worldwide, is a multi-system disorder affecting the kidney, liver, and lungs. Infections can be asymptomatic, self-limiting or progress to multi-organ system failure and pulmonary hemorrhage. The incidence of canine and human leptospirosis is steadily increasing worldwide. At least sixty-four Leptospira species and several hundred lipopolysaccharide-based serovars have been defined. Preventive vaccines are available for use in veterinary medicine and limited use in humans in some countries. All commercially available vaccines are bacterin formulations that consist of a combination of laboratory cultivated strains of different lipopolysaccharide serotypes. The development of a broadly protective subunit vaccine would represent a significant step forward in efforts to combat leptospirosis in humans, livestock, and companion animals worldwide. Here we investigate the potential of General secretory protein D (GspD; LIC11570), a secretin, to serve as a possible antigen in a multi-valent vaccine formulation. GspD is conserved, expressed in vitro, antigenic during infection and elicits antibody with complement independent bactericidal activity. Importantly, antibody to GspD is bactericidal against diverse Leptospira species of the P1 subclade. Epitope mapping localized the bactericidal epitopes to the N-terminal N0 domain of GspD. The data within support further exploration of GspD as a candidate for inclusion in a next generation multi-protein subunit vaccine.

Human and Veterinary Vaccines for Lyme Disease

Lyme disease (LD) is an emerging zoonotic infection that is increasing in incidence in North America, Europe, and Asia. With the development of safe and efficacious vaccines, LD can potentially be prevented. Vaccination offers a cost-effective and safe approach for decreasing the risk of infection. While LD vaccines have been widely used in veterinary medicine, they are not available as a preventive tool for humans. Central to the development of effective vaccines is an understanding of the enzootic cycle of LD, differential gene expression of Borrelia burgdorferi in response to environmental variables, and the genetic and antigenic diversity of the unique bacteria that cause this debilitating disease. Here we review these areas as they pertain to past and present efforts to develop human, veterinary, and reservoir targeting LD vaccines. In addition, we offer a brief overview of additional preventative measures that should employed in conjunction with vaccination.