Efficacy of a multivalent DAPPi-Lmulti canine vaccine against mortality, clinical signs, infection, bacterial excretion, renal carriage and renal lesions caused by Leptospira experimental challenges

Study on the interference of vaccine antibodies with the serological diagnosis of leptospirosis in cattle

A simple IgG-specific ELISA for Leptospira spp. was compared with the microscopic agglutination test (MAT) to detect IgG antibody responses to a commercial vaccine in cattle. We used an enzyme-linked immunosorbent assay (ELISA) with sonicated Leptospira interrogans serovar copenhageni M 20. After initial vaccination, specific antibodies against Leptospira spp. were detected in 90 % of the animals by IgG-ELISA and 60 % by MAT, while after booster, antibodies were detected in 100 % and 80 % of the animals by IgG-ELISA and MAT, respectively. Both serological MAT and ELISA tests revealed interferences of vaccine antibodies. Disease diagnosis with ELISA and MAT methods should be made two and a half months and four months, respectively, after vaccination to avoid interference of vaccine antibodies. On the other hand, our results suggest that IgG-ELISA may be a useful method to assess the development of IgG antibodies induced by Leptospira vaccine.

Field assessment of potential exposure of dogs to leptospirosis by measuring antibody titers in dogs: a multisite study in five geographic regions of the United States

Leptospirosis vaccine for dogs in the United States is considered a lifestyle or non-core vaccine, making individual veterinary practitioners responsible for determining if vaccination is necessary for their patients. Veterinary professionals often base their vaccination decisions on local rates of clinical cases. However, even subclinical leptospirosis infections have zoonotic potential. The microscopic agglutination test (MAT) is effective for screening unvaccinated animals, but previous vaccination can lead to inconsistent results and variable MAT titers over time. This prospective research survey evaluated if local experience was sufficient to justify selective vaccination for leptospirosis. MAT analyses were performed on sera collected from well-cared-for, unvaccinated dogs residing in five different geographies across the United States: South-Central (East Texas), New England, the Mid-Atlantic (North Carolina and Virginia), Midwest (Wisconsin/northern Illinois), and Southwest (southern California). Thirty-eight clinics participated, submitting a total of 1345 qualified samples from unvaccinated dogs over 1 year of age. 11.6% of these unvaccinated dogs had MAT titers for one or more serogroups of Leptospira. While seropositivity does not necessarily indicate that disease will result or that a specific serovar is involved, these MAT-positive cases do indicate that the potential for exposure exists and clinical signs or a carrier-state could result from infection. These survey results would indicate that a more aggressive vaccination protocol for leptospirosis should be considered.

Immune response at a vaccine-challenge study using beagle dogs and locally isolated Leptospira spp

Determination of the immune response of dogs by measuring the antibody levels (utilizing MAT) and levels of cytokines (TNF-α, IL-4 and IFN-γ) post-vaccination with locally produced killed whole-celled Leptospiral vaccine and post-challenge with a locally isolated Leptospira icterohaemorrhagiae Copenhageni strain. For assessment of immunity of the vaccine serum antibodies were detected before and after vaccination and challenge in three studies. The effects of the challenge were determined by a variety of parameters including reisolation of the challenge Leptospira spp. via blood, urine, and kidney samples. The challenge strain did not produce generalised infection but elevated circulating antibody levels in both the control and vaccinated dogs in any of the three studies, however leptospires were reisolated from the urine of the control dogs but not the vaccinated dogs. Cytokine levels (TNF-α, IFN-γ and IL-4) were detected post-challenge in the vaccinated dogs to determine the immune profile response. The whole-killed cell vaccine in this study did not prevent leptospireamia but prevented leptospiruria in vaccinated dogs after a challenge with a live Leptospira icterohaemorrhagiea Copenhageni. The vaccine-challenge showed increased antibody (MAT) levels due to vaccination and infection (through challenge). Cytokine production (TNF-α, IFN-γ and IL-4) by the host immune system was observed post-challenge with live leptospires.

An Assessment and Comparison of the Efficacy of Two Licensed Tetravalent Leptospira Vaccines for Dogs Using an Improved Challenge Model

An objective of the present studies was to compare the protective effects of two European licensed canine tetravalent leptospirosis vaccines, Nobivac L4 and Versican Plus L4. Four similar challenge studies in beagle dogs were performed. In each study the dogs were assigned to one of three treatment groups as follows: group 1, Nobivac L4; group 2, Versican Plus L4; group 3, non-vaccinated control group. Two vaccinations were followed by a Leptospira challenge. Strains of the following serogroups were used for challenge: study 1, Grippotyphosa; study 2, Icterohaemorrhagiae; study 3, Canicola; study 4, Australis. Parameters of efficacy were antibody titres; body temperature; clinical signs; cultures of Leptospira bacteria from the blood, urine, kidney and liver; rapid urinalysis; macroscopic and histopathological examination at necropsy. It was concluded that compared to vaccination with Versican Plus L4, vaccination with Nobivac L4 resulted in generally better control of leptospirosis disease parameters after the challenge including a complete prevention of the clinical signs following a Grippotyphosa and Icterohaemorrhagiae challenge. In contrast, vaccination with Versican Plus L4 only prevented infection by Australis and shedding by Grippotyphosa and Australis but it did not lead to any statistically significant reduction of either infection or shedding following an Icterohaemorrhagiae challenge.

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.

Compatibility Between A Rabies Vaccine and Two Canine Combined Vaccines Against Canine Distemper, Adenovirosis, Parvovirosis, Parainfluenza Virus Disease and Leptospirosis, With or without Canine Coronavirus

In many countries, vaccination programs still require dogs to be vaccinated against rabies in addition to Canine distemper virus (CDV), adenovirus (CAV), parvovirus (CPV), parainfluenza virus (CPiV), Leptospira (L) or Canine coronavirus (CCV= Cv). Few vaccines containing all these antigens are commercially available and, unless compatibility between the vaccines was demonstrated, concurrent administration of a DAPPi-L(Cv) vaccine and a vaccine against rabies should not be recommended. This may be of concern for practitioners who wish to vaccinate dogs with all components on the same day. This study aimed at evaluating immunological compatibility between a monovalent rabies vaccine (Rabisin™) and two large combination vaccines against CDV, CAV, CPV, CPiV with 2 leptospira components +Cv (Recombitek® C6/Cv) or with 4 Leptospira components (Recombitek® C8), when injected concomitantly at two separate injection sites.

Fourteen days after administration of the rabies vaccine, with or without concomitant administration of combo vaccines, all dogs had seroconverted against rabies and maintained protective titers over the duration of the study. In addition, 100% of the puppies vaccinated with one or the other combo vaccines seroconverted against CDV, CAV, CPV, CPiV (CCV) and Leptospira, whatever the vaccination group. Lack of immunological interference between Rabisin™ and all components of the Recombitek® C6/Cv or Recombitek® C8 Combo vaccines was demonstrated by non-inferiority analysis, except for CDV in the Recombitek®C8+ Rabisin™ group. Based on these results, a concomitant administration of Rabisin™ with Recombitek® C6/Cv or Recombitek® C8 can be recommended in daily practice, which can be essential for facilitating vaccination compliance.

Quantitative Real-Time PCR Assays for the Detection of Pathogenic Leptospira Species in Urine and Blood Samples in Canine Vaccine Clinical Studies: a Rapid Alternative to Classical Culture Methods

Leptospirosis is a vaccine-preventable bacterial zoonotic disease caused by pathogenic Leptospira species. The efficacy of Leptospira canine vaccines is assessed by challenging vaccinated and control dogs with virulent serovars of Leptospira, followed by detection of Leptospira in blood and urine. We assessed the consistency between results obtained for urine and blood samples from clinical studies with species-specific real-time quantitative PCR (qPCR) targeting the lipL32 gene and those obtained with the reference culture method. The specificity of the qPCR assay was confirmed by negative results for nonpathogenic Leptospira and for several canine viruses, bacteria, and parasites. The results from the two methods were compared using McNemar’s test, kappa coefficient (κ), and percentage of agreement analyses. The results for numbers of positive and negative dogs were similar, with no false-negative results with the qPCR assay. For both blood and urine, there was strong agreement between the culture method and qPCR results (κ = 0.68 [95% confidence interval (CI), 0.62 to 0.74] and κ = 0.65 [95% CI, 0.59 to 0.71], respectively). However, there was a statistically significant difference between blood samples (P < 0.001) and urine samples (P = 0.028). The negative percentage agreements were 97% and 84% and the positive percentage agreements were 68% and 83% for blood and urine samples, respectively. Although the cell culture method is the recommended gold standard, our results show that qPCR assay is a valid alternative method for the rapid and specific detection of pathogenic Leptospira spp. in urine and blood samples during vaccine efficacy studies, without loss of sensitivity.

A canine vaccine against Leptospira serovars Icterohaemorrhagiae, Canicola and Grippotyphosa provides cross protection against Leptospira serovar Copenhageni

Efficacy of the Leptospira components of multivalent vaccine DAPPi-L was previously demonstrated against virulent challenge with three serovars of Leptospira interrogans (Canicola, Icterohaemorrhagiae and Grippotyphosa) carried out 14 days after primary vaccination. In this study we demonstrate that this vaccine provides, two weeks after vaccination, an additional protection (prevention of mortality, clinical signs, renal infection, bacterial excretion, renal carriage and renal lesions) against fatal leptospirosis due to Leptospira interrogans serovar Copenhageni (serovar of major medical importance).

Development of antibody ELISA specific of Leptospira interrogans serovar Grippotyphosa, Canicola, and Icterohaemorrhagiae to monitor vaccine immunogenicity

The antibody response after primary vaccination and annual revaccination with a multivalent DAPPi-L vaccine was assessed respectively in SPF dogs and in client owned dogs against the Grippotyphosa (Lg), Canicola (Lc) and Icterohaemorrhagiae (Li) Leptospira serovars. To overcome limitations of the microscopic agglutination test (MAT), we developed serovar-specific and sensitive blocking ELISA assays. Serovar-specific antibodies against Lg, Lc and Li were detected in 100%, 45% and 91% of dogs, respectively, after the first dose of vaccine, and in 100% of dogs for all serovars after the second dose. In addition, mean ELISA antibody titers increased 14 days after annual revaccination with most dogs remaining ELISA antibody positive against Lg (85.3%), Lc (90%) and Li (100%). Parallel testing of sera from the annual revaccination study in the MAT and ELISA assays resulted in an overall agreement of 72%, 67%, 77% of samples for Lg, Lc and Li serovars, respectively. More sera tested positive by ELISA than by MAT, suggesting that the ELISA assay is more sensitive than the MAT. These three new antibody-based assays are the first suitable and reliable ELISA assays for the assessment of the canine antibody response following vaccination and an attractive alternative to the MAT.

Compatibility between a rabies vaccine and a combined vaccine against canine distemper, adenovirosis, parvovirosis, parainfluenza virus and leptospirosis

In many cicumstances, veterinarians are requiring to be able to administer rabies vaccine in dogs at the same time as vaccinating against canine distemper, adenovirus, parvovirus, parainfluenza virus and leptospirosis. The aim of this study was to assess the compatibility between a multivalent vaccine and a rabies vaccine when injected at two separate sites. Lack of interference was assessed by comparing serological response to viral components during one year following primary vaccination with vaccines administered alone or concomitantly. Antibody response to all tested components was comparable, irrespective of whether vaccines were administered individually or concurrently. Notably, the rabies vaccine induced very strong and protective seroconversion in dogs, whether it was administered concomitantly with the combo vaccine or not. This facilitates administration of rabies vaccine, which is a key factor for controlling the disease.

Multivariate analysis of the immune response to a vaccine as an alternative to the repetition of animal challenge studies for vaccines with demonstrated efficacy

The assessment of vaccine combinations, or the evaluation of the impact of minor modifications of one component in well-established vaccines, requires animal challenges in the absence of previously validated correlates of protection. As an alternative, we propose conducting a multivariate analysis of the specific immune response to the vaccine. This approach is consistent with the principles of the 3Rs (Refinement, Reduction and Replacement) and avoids repeating efficacy studies based on infectious challenges in vivo. To validate this approach, a set of nine immunological parameters was selected in order to characterize B and T lymphocyte responses against canine rabies virus and to evaluate the compatibility between two canine vaccines, an inactivated rabies vaccine (RABISIN^®) and a combined vaccine (EURICAN^® DAPPi-Lmulti) injected at two different sites in the same animals. The analysis was focused on the magnitude and quality of the immune response. The multi-dimensional picture given by this 'immune fingerprint' was used to assess the impact of the concomitant injection of the combined vaccine on the immunogenicity of the rabies vaccine. A principal component analysis fully discriminated the control group from the groups vaccinated with RABISIN^® alone or RABISIN^®+EURICAN^® DAPPi-Lmulti and confirmed the compatibility between the rabies vaccines. This study suggests that determining the immune fingerprint, combined with a multivariate statistical analysis, is a promising approach to characterizing the immunogenicity of a vaccine with an established record of efficacy. It may also avoid the need to repeat efficacy studies involving challenge infection in case of minor modifications of the vaccine or for compatibility studies.