Influence of pigeon interferon alpha (PiIFN-α) on pigeon circovirus (PiCV) replication and cytokine expression in Columba livia

The pigeon circovirus evolution, epidemiology and interaction with the host immune system under One Loft Race rearing conditions

This study was aimed to investigate the frequency of PiCV recombination, the kinetics of PiCV viremia and shedding and the correlation between viral replication and host immune response in young pigeons subclinically infected with various PiCV variants and kept under conditions mimicking the OLR system. Fifteen racing pigeons originating from five breeding facilities were housed together for six weeks. Blood and cloacal swab samples were collected from birds every seven days to recover complete PiCV genomes and determine PiCV genetic diversity and recombination dynamics, as well as to assess virus shedding rate, level of viremia, expression of selected genes and level of anti-PiCV antibodies. Three hundred and eighty-eight complete PiCV genomes were obtained and thirteen genotypes were distinguished. Twenty-five recombination events were detected. Recombinants emerged during the first three weeks of the experiment which was consistent with the peak level of viremia and viral shedding. A further decrease in viremia and shedding partially corresponded with IFN-γ and MX1 gene expression and antibody dynamics. Considering the role of OLR pigeon rearing system in spreading infectious agents and allowing their recombination, it would be reasonable to reflect on the relevance of pigeon racing from both an animal welfare and epidemiological perspective.

Investigating pigeon circovirus infection in a pigeon farm: molecular detection, phylogenetic analysis and complete genome analysis

BACKGROUND

Pigeon circovirus infections in pigeons (Columba livia domestica) have been reported worldwide. Pigeons should be PiCV-free when utilized as qualified experimental animals. However, pigeons can be freely purchased as experimental animals without any clear guidelines to follow. Herein, we investigated the status quo of PiCV infections on a pigeon farm in Beijing, China, which provides pigeons for experimental use.

RESULTS

PiCV infection was verified in at least three types of tissues in all forty pigeons tested. A total of 29 full-length genomes were obtained and deposited in GenBank. The whole genome sequence comparison among the 29 identified PiCV strains revealed nucleotide homologies of 85.8-100%, and these sequences exhibited nucleotide homologies of 82.7-98.9% as compared with those of the reference sequences. The cap gene displayed genetic diversity, with a wide range of amino acid homologies ranging from 64.5% to 100%. Phylogenetic analysis of the 29 full-genome sequences revealed that the PiCV strains in this study could be further divided into four clades: A (17.2%), B (10.4%), C (37.9%) and D (34.5%). Thirteen recombination events were also detected in 18 out of the 29 PiCV genomes obtained in this study. Phylogenetic research using the rep and cap genes verified the recombination events, which occurred between clades A/F, A/B, C/D, and B/D among the 18 PiCV strains studied.

CONCLUSIONS

In conclusion, PiCV infection, which is highly genetically varied, is extremely widespread on pigeon farms in Beijing. These findings indicate that if pigeons are to be used as experimental animals, it is necessary to evaluate the impact of PiCV infection on the results.

Pigeon Rotavirus A as the cause of systemic infection in juvenile pigeons (young pigeon disease)

Recent investigations suggested pigeon associated Rotavirus Typ A genotype G18P[17] (RVA) as a causative agent of the classical 'young pigeon disease' (YPD). YPD was first described in the late 1980 s as an acute, mainly seasonally recurring disorder of mostly juvenile domestic pigeons (Columba livia) with clinical signs such as anorexia, dairrhea, vomiting, congested crops, weight loss and occasionally mortality. Various studies in the past indicated a multifactorial nature of YPD. Several pathogens, such as pigeon circovirus 1, avian adenoviruses and Escherichia coli were also suggested, but none of these could reproduce the disease experimentally. However, the impact of other pathogens on the clinical development of YPD cannot be excluded and requires further investigation. This present review summarizes available information on RVA-induced disease in pigeons, its association with YPD, the transmission, and diagnosis of the infection, and on prophylactic strategies to prevent RVA outbreaks.

Pigeon Circovirus over Three Decades of Research: Bibliometrics, Scoping Review, and Perspectives

The pigeon circovirus (PiCV), first described in the literature in the early 1990s, is considered one of the most important infectious agents affecting pigeon health. Thirty years after its discovery, the current review has employed bibliometric strategies to map the entire accessible PiCV-related research corpus with the aim of understanding its present research landscape, particularly in consideration of its historical context. Subsequently, developments, current knowledge, and important updates were provided. Additionally, this review also provides a textual analysis examining the relationship between PiCV and the young pigeon disease syndrome (YPDS), as described and propagated in the literature. Our examination revealed that usages of the term 'YPDS' in the literature are characterizations that are diverse in range, and neither standard nor equivalent. Guided by our understanding of the PiCV research corpus, a conceptualization of PiCV diseases was also presented in this review. Proposed definitions and diagnostic criteria for PiCV subclinical infection (PiCV-SI) and PiCV systemic disease (PiCV-SD) were also provided. Lastly, knowledge gaps and open research questions relevant to future PiCV-related studies were identified and discussed.

Molecular detection and phylogenetic analysis of pigeon circovirus from racing pigeons in Northern China

Background

Pigeon circovirus (PiCV) infections in pigeons (Columba livia) have been reported worldwide. Currently, pigeon racing is becoming increasingly popular and considered to be a national sport in China, and even, the greatest competitions of racing pigeons are taking place in China. However, there are still no epidemiologic data regarding PiCV infections among racing pigeons in China. The purpose of our study was to provide information of prevalence, genetic variation and evolution of PiCV from racing pigeons in China.

Results

To trace the prevalence, genetic variation and evolution of PiCV in sick and healthy racing pigeons, 622 samples were collected from 11 provinces or municipalities in China from 2016 to 2019. The results showed that the positive rate of PiCV was 19.3% (120/622) at the sample level and 59.0% (23/39) at the club level, thus suggesting that the virus was prevalent in Chinese racing pigeons. A sequence analysis revealed that the cap genes of the PiCV strains identified in our study displayed a high genetic diversity and shared nucleotide homologies of 71.9%–100% and amino acid homologies of 71.7%–100%. 28 and 36 unique amino acid substitutions were observed in the Cap and Rep proteins derived from our PiCV strains, respectively. A cladogram representation of PiCV strains phylogeny based on 90 cap gene sequences showed that the strains in this study could be further divided into seven clades (A, B, C, E, G, H, and I) and some of them were closely related to worldwide strains from different types of pigeons. A large number of recombination events (31 events) were also detected in the PiCV genomes from Chinese racing pigeons.

Conclusions

These findings indicate that PiCV strains circulating in China exhibit a high genetic diversity and also contribute to information of prevalence, genetic variation and evolution of PiCV from racing pigeons in China.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08425-8.

Characterization of agapornis fischeri interferon gamma and its activity against beak and feather disease virus

This study sought to clone and sequence the interferon-γ (IFN-γ) gene of the Fischer's lovebird parrot (Agapornis fischeri). Raw264.7 cells treated with the expressed IFN-γ protein exhibited an upregulation in inducible nitric oxide synthase protein expression and nitric oxide (NO) production coupled with increases in phagocytosis and pinocytosis, as well as an induction of interferon-stimulated genes through the activation of the NF-κB factor, all of which are indicators of the innate immune responses of the activated macrophages. Similar to the IFN-γ protein of other species, the NO production activity of the parrot IFN-γ protein decreased by 80% after exposure at 60 °C for 4 min. Additionally, only half of the NO production activity of the parrot IFN-γ protein remained upon exposure to HCl for 30 min. These findings suggested that the parrot IFN-γ protein was heat-labile and sensitive to acidic conditions. Therefore, all of these effects contributed to the blockage of the uptake of BFDV virus-like particles (VLPs) by cells, the nuclear entry of the Cap protein of BFDV VLPs, and the clearance of the virus from BFDV-infected parrots by the IFN-γ protein of Agapornis fischeri. This study is the first to describe the cloning of the IFN-γ gene of Agapornis fischeri and characterize the anti-beak and feather disease virus activity of the IFN-γ protein of Agapornis fischeri.

Transcriptome Analysis Revealed Potential Mechanisms of Resistance to Trichomoniasis gallinae Infection in Pigeon (Columba livia)

Trichomoniasis gallinae (T. gallinae) is one of the most pathogenic parasites in pigeon, particularly in squabs. Oral cavity is the main site for the host-parasite interaction. Herein, we used RNA-sequencing technology to characterize lncRNA and mRNA profiles and compared transcriptomic dynamics of squabs, including four susceptible birds (S) from infected group, four tolerant birds (T) without parasites after T. gallinae infection, and three birds from uninfected group (N), to understand molecular mechanisms underlying host resistance to this parasite. We identified 29,809 putative lncRNAs and characterized their genomic features subsequently. Differentially expressed (DE) genes, DE-lncRNAs and cis/trans target genes of DE-lncRNAs were further compared among the three groups. The KEGG analysis indicated that specific intergroup DEGs were involved in carbon metabolism (S vs. T), metabolic pathways (N vs. T) and focal adhesion pathway (N vs. S), respectively. Whereas, the cis/trans genes of DE-lncRNAs were enriched in cytokine-cytokine receptor interaction, toll-like receptor signaling pathway, p53 signaling pathway and insulin signaling pathway, which play crucial roles in immune system of the host animal. This suggests T. gallinae invasion in pigeon mouth may modulate lncRNAs expression and their target genes. Moreover, co-expression analysis identified crucial lncRNA-mRNA interaction networks. Several DE-lncRNAs including MSTRG.82272.3, MSTRG.114849.42, MSTRG.39405.36, MSTRG.3338.5, and MSTRG.105872.2 targeted methylation and immune-related genes, such as JCHAIN, IL18BP, ANGPT1, TMRT10C, SAMD9L, and SOCS3. This implied that DE-lncRNAs exert critical influence on T. gallinae infections. The quantitative exploration of host transcriptome changes induced by T. gallinae infection broaden both transcriptomic and epigenetic insights into T. gallinae resistance and its pathological mechanism.

Development and Validation of KASP Assays for the Genotyping of Racing Performance-Associated Single Nucleotide Polymorphisms in Pigeons

Pigeon racing's recent upturn in popularity can be attributed in part to the huge prize money involved in these competitions. As such, methods to select pigeons with desirable genetic characteristics for racing or for selective breeding have also been gaining more interest. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for genotyping-specific genes is one of the most commonly used molecular techniques, which can be costly, laborious and time consuming. The present study reports the development of an alternative genotyping method that employs Kompetitive Allele Specific Polymerase Chain Reaction (KASP) technology with specifically designed primers to detect previously reported racing performance-associated polymorphisms within the LDHA, MTYCB, and DRD4 genes. To validate, KASP assays and PCR-RFLP assays results from 107 samples genotyped for each of the genes were compared and the results showed perfect (100%) agreement of both methods. The developed KASP assays present an alternative rapid, reliable, and cost-effective method to identify polymorphisms in pigeons.

Immunogenicity and Protective Activity of Pigeon Circovirus Recombinant Capsid Protein Virus-Like Particles (PiCV rCap-VLPs) in Pigeons (Columba livia) Experimentally Infected with PiCV

Pigeon circovirus (PiCV) is the most recurrent virus diagnosed in pigeons and is among the major causative agents of young pigeon disease syndrome (YPDS). Due to the lack of an established laboratory protocol for PiCV cultivation, development of prophylaxis is hampered. Alternatively, virus-like particles (VLPs), which closely resemble native viruses but lack the viral genetic material, can be generated using a wide range of expression systems and are shown to have strong immunogenicity. Therefore, the use of VLPs provides a promising prospect for vaccine development. In this study, transfected human embryonic kidney (HEK-293) cells, a mammalian expression system, were used to express the PiCV capsid protein (Cap), which is a major component of PiCV and believed to contain antibody epitopes, to obtain self-assembled VLPs. The VLPs were observed to have a spherical morphology with diameters ranging from 12 to 26 nm. Subcutaneous immunization of pigeons with 100 µg PiCV rCap-VLPs supplemented with water-in-oil-in-water (W/O/W) adjuvant induced specific antibodies against PiCV. Observations of the cytokine expression and T-cell proliferation levels in spleen samples showed significantly higher T-cell proliferation and IFN- γ expression in pigeons immunized with VLPs compared to the controls (p < 0.05). Experimentally infected pigeons that were vaccinated with VLPs also showed no detectable viral titer. The results of the current study demonstrated the potential use of PiCV rCap-VLPs as an effective vaccine candidate against PiCV.

Probiotic supplementation containing Bacillus velezensis enhances expression of immune regulatory genes against pigeon circovirus in pigeons (Columba livia)

AIMS

In this study, we aimed to isolate and evaluate the efficacy of Bacillus velezensis as a probiotic and to assess its activity towards pigeons infected with pigeon circovirus (PiCV).

METHODS AND RESULTS

Bacillus velezensis, isolated from pigeon faeces, was orally administered to pigeons for 60 days. After pigeons were challenged with PiCV, the PiCV viral load and expression of indicator genes for innate immunity were detected in spleen tissue and faeces of pigeons. Bacillus velezensis significantly reduced the PiCV viral load in the faeces and spleen of pigeons 5 days post-challenge (dpc). The mRNA expression levels of treated pigeons showed that interferon-gamma (IFN-γ), myxovirus resistance 1 (Mx1), and signal transducers and activators of transcription 1 (STAT1) genes were upregulated, whereas no expression of interleukin-4 (IL-4) was detected. Moreover, toll-like receptor 2 (TLR2) and 4 (TLR4) were significantly upregulated in probiotic-treated pigeons (P < 0·05).

CONCLUSIONS

This is the first report showing that probiotic supplementation can effectively enhance the T-helper type 1 immune response and decrease the PiCV viral loads in pigeons.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study proposes that the administration of a probiotic strain, B. velezensis, to pigeons can protect against PiCV infection.

Common bacterial, viral, and parasitic diseases in pigeons (Columba livia): A review of diagnostic and treatment strategies

Pigeons (Columba livia) have been associated with humans for a long time now. They are raised for sport (pigeon race), exhibition (display of fancy breeds), food, and research. Most of the pigeons kept are Racing Homers, trained to compete in the pigeon race. Other breeds, such as Rollers, Nose Divers, Doneks are bred for their aerial abilities. Incorporation of a good preventive medicine program is one of the most critical factors in averting infectious diseases in pigeon flocks. This review summarizes the common bacterial, viral, and parasitic infections in pigeons. The different clinical signs, symptoms, diagnostic strategies, prevention, and treatments were described in this review. Current researches, molecular diagnostic assays, and treatment strategies such as vaccines and drug candidates were included. The information found in this review can provide insights for veterinarians and researchers studying pigeons to develop effective and efficient immunoprophylactic and diagnostic tools for pigeon diagnosis and therapeutics.