Serotype independent protection induced by a vaccine based on the IgM protease of Streptococcus suis and proposal for a new immunity-based classification system.

The IgM protease (IdeSsuis gene; Gene ID 8153996) of Streptococcus suis is a putative virulence factor that has been shown to be a protective vaccine antigen for pigs (Seele et al. Vaccine 33:2207-12, 2015). To assess its potential as a cross-protective antigen, the amino acid variability among prevalent clinical isolates in various regions and among various serotypes was investigated. Multi-sequence alignment of full-length amino acid sequences of S. suis IgM protease, available in the public domain (status Jan-2022) supplemented with in-house sequences, i.e. a total of 1999 sequences, revealed that the IgM protease of S. suis clusters into three main evolutionary distinct branches: groups A, B and C. Group A, 82% of the sequences in the database, was associated with clinical isolates of various serotypes. Group B, 6% of the strains in the database, was associated with clinical isolates mainly in the EU and mainly belonging to serotype (st) 9. Group C, 12% of the strains in the database, was largely associated with healthy carrier isolates, i.e. nose or tonsil isolates of various serotypes but in particular with st9 and un-typable strains. Within the groups A, B and C, high levels of amino acid identity were observed (> 75%), whereas between groups A and B, the percentage amino acid identity was approximately 30% and between groups A and C approximately 55%. Experimental Escherichia coli expressed recombinant subunit vaccines based on the IgM protease group A sequence of st1 strain B10-99, st2 strain 10 or st7 strain 14009-1, induced serotype independent protection in pigs against challenge with all group A strains tested, i.e. strains of different parts of the phylogenetic tree and of different serotypes including st1, 2, 9 and 14. Protection was observed after vaccination of piglets at 3 and 5 weeks of age and subsequent challenge at 7 weeks but also after vaccination of gilts at 6 and 2 weeks before anticipated parturition and challenge of the offspring up to at least 8 weeks of age. No protection was observed against challenge with st9 strain SZ2000-6264 having group B IgM protease. A recombinant subunit vaccine based on the group B IgM protease sequence, also did not protect against challenge with the homologous group B st9 challenge strain. The results indicate that a vaccine based on a group A IgM protease induces protection against all S. suis strains that express the group A IgM protease. Depending on the geographical region such a vaccine is expected to protect against 60-100% of the virulent S. suis strains. Since the novel proposed IgM protease classification is highly relevant, a PCR was developed and validated, to be able to classify clinical isolates into IgM protease groups A, B and C and predict the cross-protection that can be expected from a group A based IgM protease vaccine.

The steroid catabolic pathway of the intracellular pathogen Rhodococcus equi is important for pathogenesis and a target for vaccine development.

Rhodococcus equi causes fatal pyogranulomatous pneumonia in foals and immunocompromised animals and humans. Despite its importance, there is currently no effective vaccine against the disease. The actinobacteria R. equi and the human pathogen Mycobacterium tuberculosis are related, and both cause pulmonary diseases. Recently, we have shown that essential steps in the cholesterol catabolic pathway are involved in the pathogenicity of M. tuberculosis. Bioinformatic analysis revealed the presence of a similar cholesterol catabolic gene cluster in R. equi. Orthologs of predicted M. tuberculosis virulence genes located within this cluster, i.e. ipdA (rv3551), ipdB (rv3552), fadA6 and fadE30, were identified in R. equi RE1 and inactivated. The ipdA and ipdB genes of R. equi RE1 appear to constitute the α-subunit and ß-subunit, respectively, of a heterodimeric coenzyme A transferase. Mutant strains RE1ΔipdAB and RE1ΔfadE30, but not RE1ΔfadA6, were impaired in growth on the steroid catabolic pathway intermediates 4-androstene-3,17-dione (AD) and 3aα-H-4α(3'-propionic acid)-5α-hydroxy-7aß-methylhexahydro-1-indanone (5α-hydroxy-methylhexahydro-1-indanone propionate; 5OH-HIP). Interestingly, RE1ΔipdAB and RE1ΔfadE30, but not RE1ΔfadA6, also displayed an attenuated phenotype in a macrophage infection assay. Gene products important for growth on 5OH-HIP, as part of the steroid catabolic pathway, thus appear to act as factors involved in the pathogenicity of R. equi. Challenge experiments showed that RE1ΔipdAB could be safely administered intratracheally to 2 to 5 week-old foals and oral immunization of foals even elicited a substantial protective immunity against a virulent R. equi strain. Our data show that genes involved in steroid catabolism are promising targets for the development of a live-attenuated vaccine against R. equi infections.

A novel method to generate unmarked gene deletions in the intracellular pathogen Rhodococcus equi using 5-fluorocytosine conditional lethality.

A novel method to efficiently generate unmarked in-frame gene deletions in Rhodococcus equi was developed, exploiting the cytotoxic effect of 5-fluorocytosine (5-FC) by the action of cytosine deaminase (CD) and uracil phosphoribosyltransferase (UPRT) enzymes. The opportunistic, intracellular pathogen R. equi is resistant to high concentrations of 5-FC. Introduction of Escherichia coli genes encoding CD and UPRT conferred conditional lethality to R. equi cells incubated with 5-FC. To exemplify the use of the codA::upp cassette as counter-selectable marker, an unmarked in-frame gene deletion mutant of R. equi was constructed. The supA and supB genes, part of a putative cholesterol catabolic gene cluster, were efficiently deleted from the R. equi wild-type genome. Phenotypic analysis of the generated DeltasupAB mutant confirmed that supAB are essential for growth of R. equi on cholesterol. Macrophage survival assays revealed that the DeltasupAB mutant is able to survive and proliferate in macrophages comparable to wild type. Thus, cholesterol metabolism does not appear to be essential for macrophage survival of R. equi. The CD-UPRT based 5-FC counter-selection may become a useful asset in the generation of unmarked in-frame gene deletions in other actinobacteria as well, as actinobacteria generally appear to be 5-FC resistant and 5-FU sensitive.

Efficacy of a novel intradermal Lawsonia intracellularis vaccine in pigs against experimental infection and under field conditions.

BACKGROUND: The efficacy of a novel inactivated intradermal Lawsonia intracellularis vaccine, Porcilis® Lawsonia ID, was evaluated in two experimental vaccination-challenge studies and under field conditions on a farm with a history of recurrent acute ileitis. In addition, the efficacy of the vaccine was compared to that of a commercially available live attenuated vaccine. The novel inactivated vaccine consists of a freeze-dried antigen fraction that is dissolved just prior to use in either the adjuvant or in Porcilis® PCV ID; an existing intradermal vaccine against porcine Circovirus type 2. In the two experimental vaccination-challenge studies, groups of 25 piglets were vaccinated once at 3 weeks of age or left unvaccinated as challenge control. Vaccines tested were Porcilis® Lawsonia ID as standalone (study 1) or in associated mixed use with Porcilis® PCV ID (study 2) and an orally administered commercially available live vaccine (study 1). The pigs were challenged with virulent L. intracellularis at 4 weeks (study 1) or 21 weeks (study 2) after vaccination. Post-challenge, the pigs were evaluated for clinical signs, average daily weight gain, shedding and macroscopic as well as microscopic immuno-histological ileum lesion scores. In the field study, the mortality and key performance parameters were evaluated over a period of 8 months. RESULTS: The results of the two experimental vaccination-challenge studies showed that Porcilis® Lawsonia ID as single vaccine or in associated mixed use with Porcilis® PCV ID, induced statistically significant protection against experimental L. intracellularis infection, 4 weeks or 21 weeks after vaccination. This was demonstrated by lower clinical scores, improved weight gain, reduction of L. intracellularis shedding and reduction of macroscopic as well as microscopic ileum lesion scores when compared to the controls. The protection induced was superior to that of the commercially available live vaccine. In the field study Porcilis® Lawsonia ID was highly efficacious in reducing L. intracellularis associated mortality and improving key production parameters. CONCLUSION: The results support that this new intradermal vaccine is efficacious against L. intracellularis and may be used in associated mixed use with Porcilis® PCV ID.

Efficacy of a novel inactivated Lawsonia intracellularis vaccine in pigs against experimental infection and under field conditions.

The efficacy of a novel inactivated Lawsonia intracellularis vaccine, Porcilis® Lawsonia, was compared to that of a commercially available live attenuated vaccine in three experimental vaccination-challenge studies in pigs. The efficacy of the new vaccine was further tested under field conditions on a farm with a history of acute ileitis. The novel inactivated vaccine consists of a freeze-dried antigen fraction that is dissolved just prior to use in either the adjuvant or in Porcilis® PCV M Hyo; an existing combination vaccine against porcine circovirus type 2 and Mycoplasma hyopneumoniae. The three experimental vaccination-challenge trials had a similar design and for each trial 75 piglets were used, randomly allotted to three groups of 25 piglets. The pigs were vaccinated at 4 or 5 weeks of age with either Porcilis® Lawsonia in adjuvant or in associated mixed use with Porcilis® PCV M Hyo (group 1), with the live vaccine (group 2), or left as unvaccinated controls (group 3). The pigs were challenged with virulent Lawsonia intracellularis 3, 4 or 17 weeks after vaccination. Post-challenge the pigs were evaluated for clinical signs, average daily weight gain, shedding and macroscopic as well as microscopic immuno-histological ileum lesion scores. In the field study, the mortality and key performance parameters were evaluated over a period of 8 months. The results of all three experimental vaccination-challenge trials showed that Porcilis® Lawsonia induced statistically significant protection against experimental Lawsonia intracellularis infection. This was demonstrated by lower clinical scores, improved weight gain, reduction of Lawsonia intracellularis shedding and reduction of macroscopic as well as microscopic ileum lesion scores when compared to the controls. The protection induced was superior to that of the commercially available live vaccine. In the field study, Porcilis® Lawsonia proved to be highly efficacious; reducing Lawsonia associated mortality to zero and improving key production parameters.

Compatibility of a bivalent modified-live vaccine against Bordetella bronchiseptica and CPiV, and a trivalent modified-live vaccine against CPV, CDV and CAV-2.

Eight puppies (group 1) were vaccinated once with a bivalent modified-live vaccine against infectious tracheobronchitis by the intranasal route and at the same time with an injectable trivalent vaccine against canine parvovirus, canine distemper virus and canine adenovirus; a second group of eight puppies (group 2) was vaccinated only with the intranasal bivalent vaccine, and a further eight puppies (group 3) were vaccinated only with the injectable trivalent vaccine. Three weeks later they were all challenged with wildtype Bordetella bronchiseptica and canine parainfluenza virus by the aerosol route, and their antibody responses to the five vaccine organisms were determined. Oronasal swabs were taken regularly before and after the challenge for the isolation of bacteria and viruses, and the puppies were observed for clinical signs for three weeks after the challenge. There were no significant differences in the puppies' titres against canine parvovirus, canine distemper virus and canine adenovirus type 2 between the groups vaccinated with or without the bivalent intranasal vaccine. After the challenge the mean clinical scores of the two groups vaccinated with the intranasal vaccine were nearly 90 per cent lower (P=0.001) than the mean score of the group vaccinated with only the trivalent injectable vaccine, and the puppies in this group all became culture-positive for B bronchiseptica and canine parainfluenza virus. There were only small differences between the rates of isolation of B bronchiseptica from groups 1, 2 and 3, but significantly lower yields of canine parainfluenza virus were isolated from groups 1 and 2 than from group 3.

Protection of dogs for 13 months against Bordetella bronchiseptica and canine parainfluenza virus with a modified live vaccine.

Twelve specific pathogen-free (spf) puppies were vaccinated intranasally with a bivalent, modified live vaccine against infectious tracheobronchitis (group 1) and six puppies of the same age and from the same source served as unvaccinated controls (group 2). Both groups were challenged with wild-type Bordetella bronchiseptica and canine parainfluenza virus by the aerosol route 56 weeks after group 1 had been vaccinated, and at the same time six 10-week-old spf puppies from the same source (group 3) were also challenged. Oronasal swabs were taken regularly before and after the challenge, for the isolation of bacteria and viruses, and the dogs were observed for clinical signs for three weeks after the challenge. The control dogs became culture-positive for B bronchiseptica and canine parainfluenza virus, but the isolation yields from the vaccinated group were significantly lower (P<0.05). The mean clinical scores of the vaccinated group were 61 per cent lower than the scores of group 2 (P=0.009), and 90 per cent lower than the scores of group 3 (P=0.001).

Safety and efficacy of a new octavalent combined Erysipelas, Parvo and Leptospira vaccine in gilts against Leptospira interrogans serovar Pomona associated disease and foetal death.

The safety and protective efficacy of a new octavalent combination vaccine containing inactivated Erysipelothrix rhusiopathiae, Parvovirus, and Leptospira interrogans (sensu lato) serogroups Canicola, Icterohaemorrhagiae, Australis (Bratislava), Grippotyphosa, Pomona and Tarassovi - Porcilis(®) Ery+Parvo+Lepto - was evaluated in laboratory studies and under field conditions. The safety (2× overdose and repeated dose) was tested in 26 gilts. In this study, neither vaccine related temperature increase nor other systemic reactions were observed after intramuscular vaccination. No local reactions were observed except for one animal that had a small local reaction (2cm diameter) that lasted for 5 days after the third vaccination. Efficacy was tested in 40 gilts. A group of 20 gilts was vaccinated at 20 and 24 weeks of age with Porcilis(®) Ery+Parvo+Lepto and a group of 20 age- and source-matched animals served as the control group. The gilts were inseminated at 41 weeks or 66 weeks of age and were challenged with serovar Pomona 10 weeks after insemination, corresponding to 6 months (n=2×10) and 12 months (n=2×10) after the last vaccination. After both the 6- and 12-month challenges the control animals developed clinical signs (fever, lethargy and anorexia) and leptospiraemia as determined by positive blood culture. In addition, both the 6- and 12-month challenges resulted in death of 21% and 27% of the total number of foetuses in the control groups, respectively. Clinical signs and leptospiraemia were statistically significantly lower in vaccinated gilts after both the 6- and 12-month challenges. In addition, foetal death was statistically significantly lower (3% and 2%, respectively) in vaccinated gilts after both the 6- and 12 month challenges. The vaccine was tested further under field conditions on a Portuguese farm with a history of an increasing abortion rate associated with a Leptospira serovar Pomona infection (confirmed by PCR and serology). This study was designed as an observational-longitudinal field study. At the start of the study, all breeding sows and replacement gilts on the farm were vaccinated twice with Porcilis(®) Ery+Parvo+Lepto at an interval of 4 weeks. Starting six months after the primary vaccination schedule, the animals were re-vaccinated during the second week of every subsequent lactation. New replacement gilts were vaccinated using the same schedule. After vaccination, the abortion rate reduced rapidly from 12.6% in winter months of 2012 (December 2011 to March 2012) to 0.5% in winter months of 2013, a statistical significant decrease of 96%. The total number of abortions on the farm decreased from 55 in 2012 to 6 in 2013. Thereafter, the abortion rate remained stable and in the period December 2013 to April 2014 was still low (0.6%). In conclusion, the present studies demonstrate that the octavalent Porcilis(®) Ery+Parvo+Lepto vaccine can be safely used in gilts and sows and induces significant protection, for the duration of at least one year, against serovar Pomona induced clinical signs, leptospiraemia and foetal death. Protection against Pomona associated reproductive failure was confirmed under field conditions where a significant reduction in abortion rate was observed.

Studies of the efficacy of a novel intranasal vaccine against feline bordetellosis.

A novel intranasal vaccine against disease caused by Bordetella bronchiseptica in cats was tested in a series of three experiments. In the first experiment a vaccinated group and an unvaccinated control group of kittens were challenged by the aerosol route with virulent B bronchiseptica three weeks after they had been vaccinated. The control kittens developed upper respiratory tract signs typical of feline B bronchiseptica infection, including rhinitis, a serous ocular and nasal discharge, fever, sneezing and coughing. The mean (sd) clinical score for the cats in the unvaccinated control group was 19.5 (5.4) compared with 1.53 (1.9) for the vaccinated group. In the second experiment vaccinated kittens were challenged with virulent B bronchiseptica 72 hours after they were vaccinated. Their mean clinical score was 2.76 (2.62) compared with 13.4 (3.33) for the control group. In the final experiment, vaccinated and unvaccinated control cats were challenged after six or 12 months. After six months the mean clinical scores were 13.9 (4.7) for the control group, compared with 1.33 (1.56) for the vaccinated group, and after 12 months the scores were 9.92 (5.79) for the control group compared with 0.92 (0.89) for the vaccinated group.

Seroepidemiological survey of Bordetella bronchiseptica and canine parainfluenza-2 virus in dogs in Sweden.

The prevalence of antibodies against Bordetella bronchiseptica and canine parainfluenza-2 virus (CPiV-2) was investigated in a population of 302 pet dogs in Sweden. Sera were analysed for B bronchiseptica-specific immunoglobulin G by means of an ELISA, and for CPiV-2 specific neutralising antibody by means of a haemagglutination inhibition test. B bronchiseptica had a seroprevalence of 22 per cent and CPiV-2 had a seroprevalence of 28 per cent. The two pathogens did not appear to circulate together. The crowding of dogs together was significantly associated with the seroprevalence of CPiV-2, but not with the seroprevalence of B bronchiseptica. The dogs' ages, gender or their Fédération Cynologique Internationale breed group affiliation was not correlated with the seroprevalence of either pathogen.