Vaccines against infectious coryza

Veterinary Autogenous Vaccines for Poultry in Europe-Many Ways to Crack an Egg

In the past decade, European animal farming has increasingly used autogenous vaccines for the prevention of nonnotifiable diseases. In Europe, these vaccines are exclusively inactivated bacterial and viral vaccines, with a set of specific regulations that differentiate them from conventional vaccines. The highest number of applications most likely occurs in poultry, as these animal species are farmed in the highest numbers compared with other types of food-producing animals. In 2019, autogenous vaccines came within the scope of harmonized European regulation for the first time, although many important aspects are still missing and need to be further developed. Consequently, several important legal provisions remain in national legislations and can vary tremendously between different member states of the European Union. The inclusion of autogenous vaccines in the management of certain diseases of poultry is justified by the nonavailability of licensed vaccines and the evolution and diversity of antigens in the field that are not covered by licensed vaccines. In addition, these vaccines aid in reducing the use of antibiotics. The methods for isolating and typing pathogenic isolates to obtain relevant antigens are pathogen specific and require a careful approach based on clinical evidence. Manufacturing processes are optimized according to regulatory standards, and they represent the most critical factor influencing the quality of autogenous vaccines and their placement on the market. This review presents the important requirements for manufacturing autogenous vaccines for poultry in addition to the relevant regulatory considerations. The results from a survey of several European Union member states regarding specific provisions within their national legislations are also presented.

Assessment of antigenic specificity of polyclonal antisera raised against Avibacterium paragallinarum by ELISA

Lack of availability of commercial antibodies against whole-cell antigen or an antigenic epitope of Avibacterium paragallinarum (Av. paragallinarum) has hindered the development of novel immunoassays for the diagnose infectious coryza (IC). In this study, we raised polyclonal antisera against Av. paragallinarum and evaluated its antigenic-specificity using enzyme linked immunosorbent assay (ELISA). We standardized antigen coating concentration(s), antibody detection limit, and optimal range of dilutions of primary antisera and secondary conjugated antibody. Our results show the development of antigen-specific antibody response in rabbits following repeated antigenic exposure with 0.5% formalinized antigen over a period of four weeks. Further, we showed its possible applicability in detection of pathogens in tissues by immunohistochemistry for confirmatory disease diagnosis and disease pathogenetic study.

Characterization of an Outbreak of Infectious Coryza (Avibacterium paragallinarum) in Commercial Chickens in Central California

In 2017, the Turlock branch of the California Animal Health & Food Safety laboratory system received a significant increase in infectious coryza (IC) necropsy cases, with a total of 54 submissions originating from commercial broilers (n = 40), commercial layers (n = 11), and backyard chickens (n = 3). Layer flocks positive for IC were distributed within the adjacent counties of Merced and Stanislaus, while broiler flocks were concentrated within Merced County. The backyard flocks were located in Alameda and Sacramento counties. The clinical and pathologic presentation was consistent with IC, although septicemic lesions were also noticed. Avibacterium paragallinarum was isolated and identified by PCR from the respiratory tract as well as from extrarespiratory sites. Polymicrobial infections involving other viral (infectious bronchitis virus, infectious bursal disease virus) and bacterial (Mycoplasma spp., Escherichia coli, Ornithobacterium rhinotracheale, Gallibacterium anatis biovar haemolytica) agents were commonly reported. Thirteen selected Av. paragallinarum isolates were successfully characterized as serovar C (Page scheme) and serovar C2 (Kume scheme). They shared a unique enterobacterial repetitive intergenic consensus (ERIC) PCR, differing from the four reference strains, and showed consistent high minimum inhibitory concentration values for tetracycline, suggesting a common origin from a single clone. Based on these results, high biosecurity standards and proper immunization of susceptible, multi-age flocks should always be implemented and adjusted as needed. The importance of backyard flocks should not be underestimated due to their unique epidemiologic role.

The current epidemiological status of infectious coryza and efficacy of PoulShot Coryza in specific pathogen-free chickens

Infectious coryza (IC) is an infectious disease caused by Avibacterium (Av.) paragallinarum. IC is known to cause economic losses in the poultry industry via decreased egg production in layers. Between 2012 and 2013, Av. paragallinarum was isolated from seven chicken farms by Chungbuk National University. We identified Av. paragallinarum, the causative pathogen of IC by polymerase chain reaction (PCR) and serovar serotype A, by multiplex PCR. Antibiotic sensitivity tests indicated that a few field-isolated strains showed susceptibility to erythromycin, gentamicin, lincomycin, neomycin, oxytetracycline, spectinomycin, and tylosin. A serological survey was conducted to evaluate the number of flocks that were positive for Av. paragallinarum by utilizing a HI test to determine the existence of serovar A. Serological surveys revealed high positivity rates of 86.4% in 2009, 78.9% in 2010, 70.0% in 2011, and 69.6% in 2012. We also challenged specific pathogen-free chickens with isolated domestic strains, ADL121286 and ADL121500, according to the measured efficacy of the commercial IC vaccine, PoulShot Coryza. We confirmed the effectiveness of the vaccine based on relief of clinical signs and a decreased re-isolation rate of ADL121500 strain. Our results indicate IC is currently prevalent in Korea, and that the commercial vaccine is effective at protecting against field strains.

Protection Conferred by Infectious Coryza Vaccines Against Emergent Avibacterium paragallinarum Serovar C-1

Infectious coryza is an upper respiratory disease of chickens caused by Avibacterium paragallinarum. Outbreaks of infectious coryza caused by Av. paragallinarum serovar C-1 isolates in coryza-vaccinated flocks in Ecuador and Mexico have been reported. In the current study, the protection conferred by four commercially available, trivalent infectious coryza vaccines in chickens challenged with a serovar C-1 isolate from an apparent coryza vaccine failure in a layer flock in Mexico was evaluated. Only one infectious coryza vaccine provided a good protection level (83%) in vaccinated chickens. These results might explain the infectious coryza outbreaks in vaccinated flocks that have been observed in the field.

Transcriptional profiling of chicken immunity-related genes during infection with Avibacterium paragallinarum

Avibacterium paragallinarum is the causative agent of Infectious Coryza (IC), which is an upper respiratory tract disease in chickens. The occurrence of outbreaks has emphasized the significance of the disease globally in the chicken industry. Studies have demonstrated that early immune responses are critical in defining the severity and physiological outcome of an infection. This prompted the need to investigate the regulation of immune functions by the number of genes that are expressed during the chickens' response to A. paragallinarum serovar C3 insult. This study consisted of 15 male leghorn birds that were scored into groups (score 1, 2, 3) according to severity of symptoms after they were challenged. Expression patterns of immunity-related genes were followed as symptoms progressed from a disease score of 1 to 3. The data proposed that initial pathogen recognition was either through Toll-like receptors 2 or 4. Unique expression patterns were observed such as the up-regulation of TLR7 which recognizes viral-like particles. This substantiated the presence of prophages reported in the genome of A. paragallinarum. Significant down-regulation of metabolic pathways was observed, which led us to hypothesize that the host may rely on an oxidative stress response as initial immune response. The data sheds light onto the mechanisms that govern the immune system towards infection and/or towards the initial response to infections with highly virulent A. paragallinarum.

Safety and efficacy studies on trivalent inactivated vaccines against infectious coryza

The safety and efficacy of an inactivated oil-emulsion infectious coryza vaccine containing three Avibacterium paragallinarum isolates (one each of Page serovars A, B, and C) was evaluated. The safety of six batches of the vaccine was confirmed by testing with chickens vaccinated with a single large dose or vaccinated repeatedly with a normal dose. Efficacy tests were carried out on three batches of vaccine using both specific pathogen free (SPF) chickens and conventional chickens. In SPF chickens given a single vaccination at 42 days of age, the protection rate against all three serovars of Av. paragallinarum was at least 80% at 30 days post vaccination. The conventional chickens, which were immunized at 42 and 110 days of age, were challenged at 9 months post the second vaccination and the protection rate was at least 80% for all three serovars. The effect of storage on the vaccine was evaluated in SPF chickens using three batches of vaccine stored at 4-8°C for 1 year. The protection rate against challenge from all three serovars (single vaccination at 42 days of age and challenge at 30 days post-vaccination) was at least 80%.

Monoclonal antibody characterization of reference isolates of different serogroups of Haemophilus paragallinarum

Previously, a panel of five monoclonal antibodies (Mabs) was used to study the antigens of strains 0083, 0222 and Modesto of Haemophilus paragallinarum and marked antigenic differences were noted. To establish if these differences were serogroup specific, more reference strains were examined with these Mabs. It was not possible to detect any relationship between the antigens recognized by the Mabs and the serogroup of the reference strain. None of the Mabs produced reacted with the haemagglutinins of the reference strains. The F1 Mab detected an outer membrane protein of 39 kDa, while the V1 Mab detected a lipopolysaccharide of between 13.8 to 14 kDa. Mabs VF1 and VF2 both recognized antigens of 39 kDa of unknown chemical nature and with extremely low frequency of occurrence among strains and isolates. The VF3 Mab detected a lipopolysaccharide with multiple bands at 37 to 39 kDa, which broke down after freezing and thawing to multiple bands of 29 to 32 kDa. These results imply that the haemagglutinins, which are the major typing and protective antigens remain undetected by this panel of Mabs.

Membrane vesicles released by Avibacterium paragallinarum contain putative virulence factors

Avibacterium paragallinarum, the causative agent of infectious coryza, releases extracellular membrane vesicles (MVs), containing immunogenic proteins, proteases, putative RTX proteins, haemagglutinin, and nucleic acids, into the medium. MVs ranging 50-300 nm in diameter were observed by electron microscopy. They contained immunogenic proteins in the range of 20-160 kDa, detected using vaccinated or experimentally infected chicken sera raised against Av. paragallinarum, but not in pooled sera from specific pathogen-free chickens. Proteolytic activity was not detected in MVs through zymograms; however, immune recognition of high molecular mass bands was observed by Western blotting using an antiprotease serum against Actinobacillus pleuropneumoniae serotype 1 purified protease, suggesting its presence. MVs agglutinated glutaraldehyde-fixed chicken red blood cells indicating the presence of haemagglutinating antigens. Nucleic acids were also detected inside MVs. Avibacterium paragallinarum releases MVs containing putative virulence factors, which could be important in the pathogenesis of infectious coryza.

Protection Conferred by Bivalent and Trivalent Infectious Coryza Bacterins Against Prevalent Serovars of Avibacterium (Haemophilus) paragallinarum in Mexico

The protection and level of hemagglutination-inhibition (HI) antibodies conferred in infectious coryza bivalent- and trivalent-immunized chickens against Avibacterium (Haemophilus) paragallinarum field isolates of the prevalent serovars in Mexico (A-1, A-2, B-1, and C-2) were investigated. The bivalent bacterin (A-1 and C-1) conferred significant protection and increased HI antibodies against isolates of serovars A-1, A-2, and C-2, but not against a serovar B-1 isolate. The trivalent bacterin (A-1, B-1, and C-2) conferred protection and increased HI antibodies against all four of the isolates. The results confirmed that in poultry areas where serovar B-1 is prevalent, the inclusion of this serovar in bacterins is needed to confer protection against infectious coryza caused by A. (H.) paragallinarum isolates of serovar B-1.

Cross-protection study of the nine serovars of Haemophilus paragallinarum in the Kume haemagglutinin scheme

The cross-protection and haemagglutination-inhibition antibodies present in chickens vaccinated with one of the nine currently recognized Kume haemagglutinin serovars of Haemophilus paragallinarum were investigated. The results confirmed the widely accepted dogma that serogroups A, B, and C represent three distinct immunovars. Within Kume serogroup A, there was generally good cross-protection among all four serovars. However, within Kume serogroup C, there was evidence of a reduced level of cross-protection between some of the four serovars. The haemagglutination-inhibition antibody levels generally showed the same trend as with the cross-protection results. This study suggests that some apparent field failures of infectious coryza vaccines may be due to a lack of cross-protection between the vaccine strains and the field strains. Our results will help guide the selection of strains for inclusion in infectious coryza vaccines.

Infectious coryza: overview of the disease and new diagnostic options

Infectious coryza is a well-recognized and commonly encountered upper respiratory tract disease of chickens that is caused by the bacterium Haemophilus paragallinarum. The occurrence of recent outbreaks in North America has emphasized that the disease can be significant in meat chickens as well as layer chickens. In developing countries, coryza is commonly complicated by the presence of a range of other infections, resulting in severe disease and significant economic losses. Unusual forms of the disease, involving arthritis and septicemia, again associated with the presence of other pathogens, have been found in South America. Newly recognized bacteria such as Ornithobacterium rhinotracheale and phenotypic variant forms of both H. paragallinarum and close relatives (variant in that they no longer require V-factor for growth in vitro) have increased the difficulty associated with diagnosing the disease. There have been suggestions in both South America and South Africa that new serovars or serovar variants, associated with unusual clinical manifestations and causing vaccine failures, are emerging. Definitive evidence to confirm or deny the role of these "variants" in vaccine failures is currently not available. A new DNA-based diagnostic technique, involving PCR, has been recently described and will greatly assist in the diagnosis of infectious coryza.