Chlamydia psittaci infection increases mortality of avian influenza virus H9N2 by suppressing host immune response

Multiple infections secondary to immunosuppression after Chlamydia psittaci infection: a case report

This study presents the clinical profile of a 74-year-old male patient admitted to the hospital due to a 20-day history of coughing, chest tightness, and dyspnea. Upon admission, the patient presented with fever, tachycardia, and tachypnea. Clinical examination revealed evidence of lung infection, sepsis, and multi-organ dysfunction, alongside abnormal blood gas analysis and elevated C-reactive protein (CRP) levels. Pathogen testing confirmed Chlamydia psittaci (C. psittaci), infection. Throughout the treatment course, the patient developed concurrent fungal and viral infections, necessitating a comprehensive approach involving combined antibiotic and antifungal therapy. Despite encountering treatment-related complications, the patient demonstrated clinical improvement with aggressive management. This case underscores the importance of recognizing immune suppression subsequent to Chlamydia infection, emphasizing the critical role of early diagnosis, intervention, and standardized treatment protocols in enhancing patient prognosis.

The therapeutic efficacy of neem (Azadirecta indica) leaf extract against coinfection with Chlamydophila psittaci and low pathogenic avian influenza virus H9N2 in broiler chickens

Avian chlamydiosis is a serious avian infection that carries a significant zoonotic danger to the poultry industry. The respiratory co-infections caused by the low pathogenic avian influenza virus H9N2 (LPAIV H9N2) also cause significant financial losses in the poultry industry. The purpose of this study was to examine the pathogenicity of Chlamydophila psittaci, and LPAIV H9N2 individually and in combination in broiler chickens, as well as to determine whether or not aqueous neem (Azadirachta indica) leaf extract is effective against infections caused by these pathogens. Therefore, 120 broiler cobb chicks were equally divided into 4 groups (30 birds each) with triplicates with 10 birds. Broilers in group 1 (G1) were infected with only C. psittaci, broilers in group 2 (G2) were infected with only LPAIV H9N2, broilers in group 3 (G3) were infected with C. psittaci and LPAIV H9N2, and broilers in group 4 (G4) remained not challenged and non-treated with any therapeutic or preventive treatment (negative control). At 21 d postinfection (dpi), birds in G1, G2, and G3 were divided into 3 subgroups of 10 birds each: subgroup (A) remained infected and untreated (positive control), subgroup (B) infected and received oxytetracycline for 5 consecutive d, and subgroup (C) infected and received 8% aqueous neem leaf extract for 5 consecutive d. The multiplication of C. psittaci in birds in G1, in various tissues was evaluated using Giemsa staining and the data showed that multiplication was much higher in the lung, spleen, and liver from 6 h to 21 dpi, but low in the heart from 8 to 21 dpi. During simultaneous co-infection in G3, the birds developed significant clinical symptoms and postmortem lesions (PM). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect viral shedding from oropharyngeal and cloacal swabs between 2 dpi and 8 dpi, with cycle threshold (CT) values ranging from 22 to 24. In contrast, bacterial shedding began 6 h after infection and continued until 21 dpi, with CT values ranging from 23 to 26. Administration of an aqueous neem leaf extract at an 8% concentration (Group C) resulted in a numerical rise in average body weight across all treatment groups in the third and fourth week, as well as a reduction in LPAIV H9N2 and C. psittaci replication in the respiratory and gut of treated birds compared to those treated with oxytetracycline (Group B). Overall, respiratory co-infections pose a considerable risk to the poultry business, which is a big threat. To control C. psittaci and LPAIV H9N2 in broiler chickens, oral supplementation of 8% aqueous neem leaf extract is recommended. This treatment improves the birds' performance, as evidenced by an increase in their average body weight. In addition, the application of 8% aqueous neem leaf extract lowers C. psittaci replication within tissues and diminishes LPAIV H9N2 shedding.

Case Report: Pneumonia Caused by Chlamydia Psittaci and Cryptococcus Co-Infection

This study presents a rare case of pneumonia caused by a co-infection of Chlamydia psittaci and Cryptococcus, confirmed by metagenomic next-generation sequencing (mNGS). The patient, who had underlying chronic hepatitis B, had adopted a stray pigeon before the onset of the disease. The primary symptoms were fever, and a productive cough. The patient recovered following treatment with moxifloxacin and itraconazole. C. psittaci and Cryptococcus infections may both have been transmitted from the stray pigeon. This report highlights the potential for infections caused by multiple zoonotic pathogens and the value of mNGS for making the diagnosis of these infections.

Increased virulence due to multiple infection in Daphnia leads to limited growth in 1 of 2 co-infecting microsporidian parasites

Recent outbreaks of various infectious diseases have highlighted the ever-present need to understand the drivers of the outbreak and spread of disease. Although much of the research investigating diseases focuses on single infections, natural systems are dominated by multiple infections. These infections may occur simultaneously, but are often acquired sequentially, which may alter the outcome of infection. Using waterfleas (Daphnia magna) as a model organism, we examined the outcome of sequential and simultaneous multiple infections with 2 microsporidian parasites (Ordospora colligata and Hamiltosporidium tvaerminnensis) in a fully factorial design with 9 treatments and 30 replicates. We found no differences between simultaneous and sequential infections. However, H. tvaerminnensis fitness was impeded by multiple infection due to increased host mortality, which gave H. tvaerminnensis less time to grow. Host fecundity was also reduced across all treatments, but animals infected with O. colligata at a younger age produced the fewest offspring. As H. tvaerminnensis is both horizontally and vertically transmitted, this reduction in offspring may have further reduced H. tvaerminnensis fitness in co-infected treatments. Our findings suggest that in natural populations where both species co-occur, H. tvaerminnensis may evolve to higher levels of virulence following frequent co-infection by O. colligata.

TLR2 mediates autophagy through ERK signaling pathway in Chlamydia psittaci CPSIT_p7 protein-stimulated RAW264.7 cells

Chlamydia psittaci is a zoonotic pathogen found in birds and humans. Macrophages, major components of the innate immune system, can resist chlamydial infections and trigger adaptive immune responses. However, the molecular mechanisms underlying the action of macrophages against C. psittaci infection are not well understood. This study investigated the roles and mechanisms of plasmid-encoded protein CPSIT_p7 of C. psittaci in regulating autophagy in RAW264.7 cells. The results demonstrated that stimulation of RAW264.7 with C. psittaci plasmid protein CPSIT_p7 induced the expressions of the autophagy signaling primary regulators LC3 and Beclin1, which could also significantly induce the phosphorylation levels of ERK, JNK, p38, and Akt. Next, siRNA knockdown of TLR2 resulted in significant downregulation of CPSIT_p7-triggered autophagy in RAW264.7 cells. Moreover, the extracellular regulated protein kinase (ERK) inhibitor PD98059 markedly reduced autophagy in CPSIT_p7-stimulated macrophages. In summary, these results indicated that TLR2 plays an essential role in the induction of autophagy through the ERK signaling pathway in CPSIT_p7-stimulated RAW264.7 cells.

Case Report: Metagenomic next-generation sequencing applied in diagnosing psittacosis caused by Chlamydia psittaci infection

Background

Chlamydia psittaci is the causative agent of psittacosis in humans, while its rapid identification is hampered due to the lack of specificity of laboratory testing methods.

Case presentation

This study reports four cases of C. psittaci infection after contact with a domestic parrot, all belonging to the same family. Common manifestations like fever, cough, headache, nausea, and hypodynamia appeared in the patients. Metagenomic next-generation sequencing (mNGS) aided the etiological diagnosis of psittacosis, revealing 58318 and 7 sequence reads corresponding to C. psittaci in two cases. The detected C. psittaci was typed as ST100001 in the Multilocus-sequence typing (MLST) system, a novel strain initially reported. Based on the results of pathogenic identification by mNGS, the four patients were individually, treated with different antibiotics, and discharged with favorable outcomes.

Conclusion

In diagnosing psittacosis caused by a rare C. psittaci agent, mNGS provides rapid etiological identification, contributing to targeted antibiotic therapy and favorable outcomes. This study also reminds clinicians to raise awareness of psittacosis when encountering family members with a fever of unknown origin.

Case report: Clinical characteristics of two cases of pneumonia caused with different strains of Chlamydia psittaci

Background

With the development of metagenomic sequencing technologies, more and more cases of pneumonia caused with Chlamydia psittaci (C. psittaci) have been reported. However, it remains unknown about the characteristics of patients with pneumonia caused by different strains of C. psittaci. Here, we shared the clinical characteristics of two cases of pneumonia caused with C. psittaci strains SZ18-2 and SZ15 which were rarely identified in humans.

Case presentation

Case 1: A 69-year-old male farmer who fed ducks presented to hospital for cough, diarrhea and lethargy with the temperature of 39.8°C. Case 2: A 48-year-old male worker who slaughtered ducks was transferred to hospital for high fever, cough, myalgia, diarrhea and loss of appetite. Both patients did not take any protective measures (wearing face masks or gloves) while processing ducks. C. psittaci pneumonia was diagnosed by metagenomic next-generation sequencing and polymerase chain reaction. After treatment with doxycycline and azithromycin individually, they recovered well and discharged from hospital. Through OmpA sequencing, two different strains of SZ18-2 and SZ15 were identified in case 1 and case 2, respectively.

Conclusions

Patients infected with different strains of C. psittaci may own different clinical manifestations. C. psittaci infection should be suspected when pneumonia appears, accompanied by digestive symptoms and multiple organ dysfunction, especially under the exposure of specific birds.

The Origin of Internal Genes Contributes to the Replication and Transmission Fitness of H7N9 Avian Influenza Virus

H9N2 avian influenza viruses (AIVs) have donated internal gene segments during the emergence of zoonotic AIVs, including H7N9. We used reverse genetics to generate A/Anhui/1/13 (H7N9) and three reassortant viruses (2:6 H7N9) which contained the hemagglutinin and neuraminidase from Anhui/13 (H7N9) and the six internal gene segments from H9N2 AIVs belonging to (i) G1 subgroup 2, (ii) G1 subgroup 3, or (iii) BJ94 lineages, enzootic in different regions throughout Asia. Infection of chickens with the 2:6 H7N9 containing G1-like H9N2 internal genes conferred attenuation in vivo, with reduced shedding and transmission to contact chickens. However, possession of BJ94-like H9N2 internal genes resulted in more rapid transmission and significantly elevated cloacal shedding compared to the parental Anhui/13 H7N9. In vitro analysis showed that the 2:6 H7N9 with BJ94-like internal genes had significantly increased replication compared to the Anhui/13 H7N9 in chicken cells. In vivo coinfection experiments followed, where chickens were coinfected with pairs of Anhui/13 H7N9 and a 2:6 H7N9 reassortant. During ensuing transmission events, the Anhui/13 H7N9 virus outcompeted 2:6 H7N9 AIVs with internal gene segments of BJ94-like or G1-like H9N2 viruses. Coinfection did lead to the emergence of novel reassortant genotypes that were transmitted to contact chickens. Some of the reassortant viruses had a greater replication in chicken and human cells compared to the progenitors. We demonstrated that the internal gene cassette determines the transmission fitness of H7N9 viruses in chickens, and the reassortment events can generate novel H7N9 genotypes with increased virulence in chickens and enhanced zoonotic potential. IMPORTANCE H9N2 avian influenza viruses (AIVs) are enzootic in poultry in different geographical regions. The internal genes of these viruses can be exchanged with other zoonotic AIVs, most notably the A/Anhui/1/2013-lineage H7N9, which can give rise to new virus genotypes with increased veterinary, economic and public health threats to both poultry and humans. We investigated the propensity of the internal genes of H9N2 viruses (G1 or BJ94) in the generation of novel reassortant H7N9 AIVs. We observed that the internal genes of H7N9 which were derivative of BJ94-like H9N2 virus have a fitness advantage compared to those from the G1-like H9N2 viruses for efficient transmission among chickens. We also observed the generation of novel reassortant viruses during chicken transmission which infected and replicated efficiently in human cells. Therefore, such emergent reassortant genotypes may pose an elevated zoonotic threat.

Molecular Characterization Analysis of Prevalent Infectious Bronchitis Virus and Pathogenicity Assessment of Recombination Strain in China

Avian coronavirus infectious bronchitis virus (IBV) is a respiratory pathogen of chickens, resulting in severe economic losses in the poultry industry. This study aimed to monitor and isolate the molecular identity of IBV in broiler flocks with respiratory symptoms in eight provinces of China. In total, 910 samples (oropharyngeal and cloacal mixed swabs) from broiler flocks showed IBV positive rates of 17.6% (160/910) using PCR assay. Phylogenetic analysis of the complete S1 genes of 160 IBV isolates was performed and revealed that QX-type (GI-19), TW-type (GI-7), 4/91-type (GI-13), HN08-type (GI-22),TC07-2-type (GVI-1), and LDT3-type (GI-28) exhibited IBV positive rates of 58.15, 25, 8.12, 1.86, 5.62, and 1.25%. In addition, recombination analyses revealed that the four newly IBV isolates presented different recombination patterns. The CK/CH/JS/YC10-3 isolate likely originated from recombination events between strain YX10 (QX-type) and strain TW2575-98 (TW-type), the pathogenicity of which was assessed, comparing it with strain GZ14 (TW-type) and strain CK/CH/GD/JR07-7 (QX-type). The complete S1 gene data from these isolates indicate that IBV has consistently evolved through genetic recombination or mutation, more likely changing the viral pathogenicity and leading to larger outbreaks in chick populations, in China.

Molecular characterization of Chlamydia species in commercial and backyard poultry farms in Costa Rica

Outbreaks caused by Chlamydia psittaci and other chlamydial species have recently been reported in poultry farms worldwide, causing considerable economic losses. The objective of this study was to determine the presence of chlamydial species in these birds in Costa Rica. One hundred and fifty pools of lung tissue samples from industrial poultry with respiratory problems and 112 pools of tracheal swabs from asymptomatic backyard poultry were analysed by real-time quantitative polymerase chain reaction (qPCR), end-point PCR and sequencing. A total of 16.8% (44/262) samples were positive for Chlamydia spp., most of them detected in asymptomatic backyard poultry (28.6%, 32/112) and fewer in industrial poultry (8%, 12/150). Of these positive samples, 45.5% (20/44) were determined to be C. psittaci . For the first time C. psittaci genotype A is reported in poultry in Latin America. In addition, the presence of Chlamydia gallinacea in backyard poultry and of Chlamydia muridarum in industrial and backyard poultry is reported for the first time in Central America. In 40.9% (18/44) of the positive samples, it was not possible to identify the infecting chlamydial species. These findings reveal a zoonotic risk, particularly for poultry farm and slaughterhouse workers having direct contact with these birds.

Infectious Bronchitis Virus Infection Increases Pathogenicity of H9N2 Avian Influenza Virus by Inducing Severe Inflammatory Response

Infectious bronchitis virus (IBV) and H9N2 avian influenza virus (AIV) are frequently identified in chickens with respiratory disease. However, the role and mechanism of IBV and H9N2 AIV co-infection remain largely unknown. Specific-pathogen-free (SPF) chickens were inoculated with IBV 2 days before H9N2 virus inoculation (IBV/H9N2); with IBV and H9N2 virus simultaneously (IBV+H9N2); with H9N2 virus 2 days before IBV inoculation (H9N2/IBV); or with either IBV or H9N2 virus alone. Severe respiratory signs, pathological damage, and higher morbidity and mortality were observed in the co-infection groups compared with the IBV and H9N2 groups. In general, a higher virus load and a more intense inflammatory response were observed in the three co-infection groups, especially in the IBV/H9N2 group. The same results were observed in the transcriptome analysis of the trachea of the SPF chickens. Therefore, IBV might play a major role in the development of respiratory disease in chickens, and secondary infection with H9N2 virus further enhances the pathogenicity by inducing a severe inflammatory response. These findings may provide a reference for the prevention and control of IBV and H9N2 AIV in the poultry industry and provide insight into the molecular mechanisms of IBV and H9N2 AIV co-infection in chickens.

Genetic and phenotypic analysis of the pathogenic potential of two novel Chlamydia gallinacea strains compared to Chlamydia psittaci

Chlamydia gallinacea is an obligate intracellular bacterium that has recently been added to the family of Chlamydiaceae. C. gallinacea is genetically diverse, widespread in poultry and a suspected cause of pneumonia in slaughterhouse workers. In poultry, C. gallinacea infections appear asymptomatic, but studies about the pathogenic potential are limited. In this study two novel sequence types of C. gallinacea were isolated from apparently healthy chickens. Both isolates (NL_G47 and NL_F725) were closely related to each other and have at least 99.5% DNA sequence identity to C. gallinacea Type strain 08-1274/3. To gain further insight into the pathogenic potential, infection experiments in embryonated chicken eggs and comparative genomics with Chlamydia psittaci were performed. C. psittaci is a ubiquitous zoonotic pathogen of birds and mammals, and infection in poultry can result in severe systemic illness. In experiments with embryonated chicken eggs, C. gallinacea induced mortality was observed, potentially strain dependent, but lower compared to C. psittaci induced mortality. Comparative analyses confirmed all currently available C. gallinacea genomes possess the hallmark genes coding for known and potential virulence factors as found in C. psittaci albeit to a reduced number of orthologues or paralogs. The presence of potential virulence factors and the observed mortality in embryonated eggs indicates C. gallinacea should rather be considered as an opportunistic pathogen than an innocuous commensal.

Co-Infection of Escherichia coli, Enterococcus faecalis and Chlamydia psittaci Contributes to Salpingitis of Laying Layers and Breeder Ducks

Salpingitis is manifested as hemorrhagic follicular inflammation exudations and peritonitis, leading to reduced egg production and high culling of breeder flocks. From 2018 to 2021, increasing salpingitis during egg peak is threatening the poultry industry post-artificial insemination, both in breeder layers and breeder ducks across China. In our study, Escherichia coli (E. coli), Enterococcus faecalis(E. faecalis) and Chlamydia psittaci (C. psittaci) were isolated and identified from the diseased oviducts using biochemical tests and PCR. To identify and isolate pathogenicity, we inoculated the isolates into laying hens via an intravaginal route. Later, laying hens developed typical salpingitis after receiving the combination of the aforementioned three isolates (1 × 10⁵ IFU/mL of C. psittaci and 1 × 10⁶ CFU/mL of E. faecalis and E. coli, respectively), while less oviduct inflammation was observed in the layers inoculated with the above isolate alone. Furthermore, 56 breeder ducks were divided into seven groups, eight ducks per group. The birds received the combination of three isolates, synergic infection of E. coli and E. faecalis, and C. psittaci alone via vaginal tract, while the remaining ducks were inoculated with physiological saline as the control group. Egg production was monitored daily and lesions of oviducts and follicles were determined post-infection on day 6. Interestingly, typical salpingitis, degenerated follicles and yolk peritonitis were obviously found in the synergic infection of three isolates and the birds inoculated with C. psittaci alone developed hemorrhagic follicles and white exudates in oviducts, while birds with E. faecalis or E. coli alone did not develop typical salpingitis. Finally, higher E. coli loads were determined in the oviducts as compared to E. faecalis and C. psittaci infection. Taken together, the combination of E. coli and E. faecalis, and C. psittaci could induce typical salpingitis and yolk peritonitis both in laying hens and breeder ducks. Secondary infection of E. coli and E. faecalis via artificial insemination is urgently needed for investigation against salpingitis.

IL-10-/- Enhances DCs Immunity Against Chlamydia psittaci Infection via OX40L/NLRP3 and IDO/Treg Pathways

Chlamydia psittaci (C. psittaci) is a common zoonotic agent that affects both poultry and humans. Interleukin 10 (IL-10) is an anti-inflammatory factor produced during chlamydial infection, while dendritic cells (DCs) are powerful antigen-presenting cells that induce a primary immune response in the host. However, IL-10 and DCs regulatory mechanisms in C. psittaci infection remain elusive. In vivo and in vitro investigations of the regulatory mechanisms were performed. IL-10^−/− mice, conditional DCs depletion mice (zinc finger dendritic cell-diphtheria toxin receptor [zDC-DTR]), and double-deficient mice (DD, IL-10^−/−/zDC^DTR/DTR) were intranasally infected with C. psittaci. The results showed that more than 90% of IL-10^−/− mice, 70% of wild-type mice, and 60% of double-deficient mice survived, whereas all zDC-DTR mice died. A higher lymphocyte proliferation index was found in the IL-10 inhibitor mice and IL-10^−/− mice. Moreover, severe lesions and high bacterial loads were detected in the zDC-DTR mice compared with double-deficient mice. In vitro studies revealed increased OX40-OX40 ligand (OX40-OX40L) activation and CD4⁺T cell proliferation. Besides, the expression of indoleamine 2, 3-dioxygenase (IDO), and regulatory T cells were significantly reduced in the co-culture system of CD4⁺ T cells and IL-10^−/− DCs in C. psittaci infection. Additionally, the activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome increased to facilitate the apoptosis of DCs, leading to rapid clearance of C. psittaci. Our study showed that IL-10^−/− upregulated the function of deficient DCs by activating OX40-OX40L, T cells, and the NLPR3 inflammasome, and inhibiting IDO, and regulatory T cells. These effects enhanced the survival rate of mice and C. psittaci clearance. Our research highlights the mechanism of IL-10 interaction with DCs, OX40-OX40L, and the NLPR3 inflammasome, as potential targets against C. psittaci infection.

Intranasal immunization with inactivated chlamydial elementary bodies formulated in VCG-chitosan nanoparticles induces robust immunity against intranasal Chlamydia psittaci challenge

Vaccines based on live attenuated Chlamydia elementary bodies (EBs) can cause disease in vaccinated animals and the comparably safer inactivated whole EBs are only marginally protective. Recent studies show that a vaccine formulation comprising UV-inactivated EBs (EB) and appropriate mucosal delivery systems and/or adjuvants induced significant protective immunity. We tested the hypothesis that intranasal delivery of UV-inactivated C. psittaci EB formulated in Vibrio cholerae ghosts (VCG)-chitosan nanoparticles will induce protective immunity against intranasal challenge in SPF chickens. We first compared the impact of VCG and CpG adjuvants on protective immunity following IN mucosal and IM systemic delivery of EB formulated in chitosan hydrogel/microspheres. Immunologic analysis revealed that IN immunization in the presence of VCG induced higher levels of IFN-γ response than IM delivery or the CpG adjuvanted groups. Also, vaccine efficacy evaluation showed enhanced pharyngeal bacterial clearance and protection against lung lesions with the VCG adjuvanted vaccine formulation, thereby establishing the superior adjuvanticity of VCG over CpG. We next evaluated the impact of different concentrations of VCG on protective immunity following IN mucosal immunization. Interestingly, the adjuvanticity of VCG was concentration-dependent, since protective immunity induced following IN mucosal immunization showed dose-dependent immune responses and protection. These studies reveal that formulation of inactivated chlamydial antigens with adjuvants, such as VCG and chitosan increases their ability to induce protective immune responses against challenge.

Chlamydia psittaci Triggers the Invasion of H9N2 Avian Influenza Virus by Impairing the Functions of Chicken Macrophages

Simple Summary

Chlamydia psittaci, an obligate, intracellular, Gram-negative bacterium and economically relevant pathogen in poultry and pet bird, could cause psittacosis/ornithosis, and is also a human pathogen causing atypical pneumonia after zoonotic transmission. H9N2 influenza virus, a low pathogenic avian influenza viruses’ subtype, has become endemic in different types of domestic poultry in lots of countries, resulting in great economic loss due to reduced egg production or high mortality associated with coinfection with other pathogens. These two pathogens are easily mixed with other pathogens to aggravate the disease, and often cause mixed infection in clinics. Co-infection of C. psittaci with H9N2 commonly induces severe pneumonia and high mortality in specific pathogen-free (SPF) chickens. According to previous studies, we postulated that C. psittaci infection may beneficial for the replication of H9N2 in HD11. Consequently, in this study, we clarify the pathogenic mechanism of coinfection with C. psittaci and H9N2 in the chicken macrophage cell line HD11, which is the first study of the coinfection of C. psittaci and H9N2 in vitro.

Abstract

In a pilot study, simultaneous infection with Chlamydia psittaci (C. psittaci) and H9N2 virus induced 20% mortality and severe avian airsacculitis, shedding light on animal models of poultry respiratory diseases. However, the pathogenesis is still unclear. In the current study, we hypothesized that C. psittaci infection execrates macrophage function and facilitates H9N2 infection. To explore the potential mechanism, we studied the effect of C. psittaci and H9N2 on the functions of HD11 cells in vitro by simultaneous infection of C. psittaci and H9N2. At the same time, we used infection with C. psittaci or H9N2 alone as the control groups. The results showed that coinfection with C. psittaci and H9N2 could significantly aggravate the mortality of HD11 cells compared to C. psittaci or H9N2 infection alone. In addition, coinfection with C. psittaci and H9N2 did not induce high C. psittaci loads compared to C. psittaci infection alone at 12- and 24-hours post-inoculation (hpi), but coinfection with C. psittaci and H9N2 could increase the loads of H9N2 compared to H9N2 alone in HD11 cells at 12 hpi. More importantly, inducible nitric oxide synthase (iNOS) expression levels, enzyme activity, nitric oxide (NO) production, and phagocytosis were reduced significantly in the group with C. psittaci and H9N2 coinfection compared to those of H9N2 or C. psittaci alone at 24 hpi. Finally, C. psittaci infection induced robust expressions of type Th2 cytokines interleukin (IL)-4 and IL-10, while interferon gamma (IFN-γ) and tumor necrosis factor-α (TNF-α) displayed a significant decrease compared to H9N2 infection alone at 24 hpi. All the above data indicate that C. psittaci infection can facilitate H9N2 invasion and to aggravate severe avian airsacculitis by impairing macrophage functions.

Recombinant Lactococcus Lactis Expressing M1-HA2 Fusion Protein Provides Protective Mucosal Immunity Against H9N2 Avian Influenza Virus in Chickens

H9N2 subtype low pathogenicity avian influenza virus (LPAIV) is distributed worldwide and causes enormous economic losses in the poultry industry. Despite immunization of almost all chickens with inactivated vaccines, the disease still remains widespread. We speculated that improving mucosal or cellular immune responses could contribute to improved control of H9N2 viruses. In this study, we constructed a novel Lactococcus lactis (L. lactis) strain expressing a recombinant fusion protein consisting of the M1 and HA2 proteins derived from an antigenically conserved endemic H9N2 virus strain. The M1-HA2 fusion protein was cloned downstream of a gene encoding a secretory peptide, and we subsequently confirmed that the fusion protein was secreted from L. lactis by Western blotting. We assessed the immunogenicity and protective effects of this recombinant L. lactis strain. Eighty 1-day-old chickens were divided into four groups, and the experimental groups were orally vaccinated twice with the recombinant L. lactis strain. Fecal and intestinal samples, sera, and bronchoalveolar lavage fluid were collected at 7, 14, and 21 days post-vaccination (dpv). Chickens vaccinated with the recombinant L. lactis strain showed significantly increased levels of serum antibodies, T cell-mediated immune responses, and mucosal secretory IgA (SIgA). Following challenge with H9N2 virus at 21 dpv, chickens vaccinated with the recombinant L. lactis strain showed decreased weight loss, lower viral titers in the lung, and reduced lung pathological damage. In summary, our results demonstrated that a recombinant L. lactis strain expressing an H9N2 M1-HA2 fusion protein could induce protective mucosal and systemic immunity. This oral vaccine is H9N2 virus-specific and represents a significant design improvement compared with previous studies. Our study provides a theoretical basis for improving mucosal immune responses to prevent and control H9N2 virus infection.

Chlamydia psittaci PmpD-N Exacerbated Chicken Macrophage Function by Triggering Th2 Polarization and the TLR2/MyD88/NF-κB Signaling Pathway

The polymorphic membrane protein D (PmpD) is a highly conserved outer membrane protein which plays an important role in pathogenesis during Chlamydia psittaci infection. In this study, we evaluated the ability of the N-terminus of PmpD (PmpD-N) to modulate the functions of chicken macrophages and the signaling pathway(s) involved in PmpD-N-induced Toll-like receptors (TLRs), as well as interleukin (IL)-6 and IL-10 cytokine secretions. Thus, HD11 macrophages were treated with exogenous and intracellular PmpD-N of C. psittaci. The chlamydial growth was evaluated by enumeration of chlamydial loads in the infected macrophages. The phagocytic function of macrophages following PmpD-N treatment was detected by fluorescein-labeled Escherichia coli (E. coli). The concentration of nitric oxide (NO) secreted by HD11 macrophages was measured by the amount of NO₂^- in the culture supernatant using the Griess method. The cytokine secretions were assessed using multiplex cytokine ELISA kits. Expression levels of TLRs, myeloid differentiation factor 88 (MyD88), and nuclear factor kappa B (NF-κB) were analyzed by a Western blotting assay, as well as a luciferase assay, while NF-κB p65 nuclear translocation was assessed by confocal microscopy. The nuclear translocation of the transcription factor NF-κB was confirmed by evaluating its ability to combine with the corresponding promoter using the electrophoretic mobility shift assay (EMSA). After treatment with exogenous or endogenous PmpD-N, chlamydial loads and phagocytic functions were reduced significantly compared with those of the plasmid vector group, while NO secretions were reduced significantly compared with those of the lipopolysaccharide (LPS) treatment. Stimulation of HD11 cells with PmpD-N provoked the secretion of the Th2 cytokines, IL-6, and IL-10 and upregulated the expression of TLR2, TLR4, MyD88, and NF-κB. Furthermore, inhibition of TLR2, MyD88, and NF-κB in HD11 cells significantly decreased IL-6 and IL-10 cytokine levels, while NO production and phagocytosis increased significantly, strongly suggesting their involvement in PmpD-N-induced Th2 cytokine secretion and macrophage dysfunction. Our data indicate that C. psittaci PmpD-N inhibited macrophage functions by activating the Th2 immune response and the TLR2/MyD88/NF-κB signaling pathway.

Feed-borne Bacillus cereus exacerbates respiratory distress in chickens infected with Chlamydia psittaci by inducing haemorrhagic pneumonia

Chlamydia psittaci is an important zoonotic pathogen and its oral route of infection plays an important role in the transmission and persistence. Bacillus cereus (B. cereus) strain, a common contaminant of animal feed and feedstuffs, can cause severe diarrhoea and malnutrition in poultry. In our previous study, a B. cereus strain (Dawu C), isolated from the haemorrhagic lungs of infected chickens, was shown to harbour two virulence genes (hblC and cytk) and was able to induce haemorrhagic lesions in the lungs, as well as gizzard erosion and ulceration (GEU) syndrome in broilers. In the present study, we tested the hypothesis that B. cereus-induced GEU would aggravate C. psittaci infection. Our results showed that SPF chickens exposed to B. cereus developed a severe GEU syndrome. More interestingly, prior infection with B. cereus facilitated C. psittaci infection, and aggravated GEU and respiratory distress, which were accompanied by high chlamydial loads in the lungs and severe lesions in respiratory organs. Moreover, levels of local inflammatory cytokines were elevated and T cell responses were impaired in the infected birds. In conclusion, GEU caused by B. cereus may facilitate chlamydial transmission from the ventriculus to the lungs.RESEARCH HIGHLIGHTS Bacillus cereus contributes to the gizzard erosion and ulceration syndrome in chickens.Exposure to Bacillus cereus exacerbates pneumonia in birds following chlamydial infection.Bacillus cereus facilitates persistent chlamydial infection and exacerbates immune responses.

Simultaneous Intramuscular And Intranasal Administration Of Chitosan Nanoparticles-Adjuvanted Chlamydia Vaccine Elicits Elevated Protective Responses In The Lung

Background

Chlamydia psittaci is a zoonotic bacteria closely associated with psittacosis/ornithosis. Vaccination has been recognized as the best way to inhibit the spread of C. psittaci due to the majority ignored of infections. The optimal Chlamydia vaccine was obstructed by the defect of single immunization route and the lack of availability of nontoxic and valid adjuvants.

Methods

In this study, we developed a novel immunization strategy, simultaneous (SIM) intramuscular (IM) and intranasal (IN) administration of a C. psittaci antigens (Ags) adjuvanted with chitosan nanoparticles (CNPs). And SIM-CNPs-Ags were used to determine the different types of immune response and the protective role in vivo.

Results

CNPs-Ags with zeta-potential values of 13.12 mV and of 276.1 nm showed excellent stability and optimal size for crossing the mucosal barrier with high 71.7% encapsulation efficiency. SIM-CPN-Ags mediated stronger humoral and mucosal responses by producing meaningfully high levels of IgG and secretory IgA (sIgA) antibodies. The SIM route also led to Ags-specific T-cell responses and increased IFN-γ, IL-2, TNF-α and IL-17A in the splenocyte supernatants. Following respiratory infection with C. psittaci, we found that SIM immunization remarkably reduced bacterial load and the degree of inflammation in the infected lungs and made for a lower level of IFN-γ, TNF-α and IL-6. Furthermore, SIM vaccination with CNPs-Ags had obviously inhibited C. psittaci disseminating to various organs in vivo.

Conclusion

SIM immunization with CNPs-adjuvanted C. psittaci Ags may present a novel strategy for the development of a vaccine against the C. psittaci infection.

Contaminated feed-borne Bacillus cereus aggravates respiratory distress post avian influenza virus H9N2 infection by inducing pneumonia

Avian influenza virus subtype H9N2 is identified in chickens with respiratory disease while Bacillus cereus (B. cereus) has been frequently isolated from chicken feed in China. However, the roles of co-infection with these two pathogens remain unclear. In the present study, SPF chicks were intragastrically administered with 10⁸ CFU/mL of B. cereus for 7 days and then inoculated intranasally with 100 EID₅₀ of H9N2 three days later. Alternatively, chickens were initially inoculated with H9N2 and then with B. cereus for one week. Post administration, typical respiratory distress persisted for 5 days in both co-infection groups. Gizzard erosions developed in the groups B. cereus/H9N2 and B. cereus group on 7^th day while in group H9N2/B. cereus on 14^th day. More importantly, both air-sac lesions and lung damage increased significantly in the co-infection group. Significant inflammatory changes were observed in the B. cereus group from day 7 to day 21. Moreover, higher loads of H9N2 virus were found in the co-infected groups than in the H9N2 group. Newcastle Disease Virus (NDV) specific antibodies were decreased significantly in the H9N2/B. cereus group compared to the B. cereus and the B. cereus/H9N2 groups. Nonspecific IgA titers were reduced significantly in the B. cereus group and the H9N2/B. cereus group compared to the control group. In addition to this, lower lymphocyte proliferation was found in the con-infection groups and the H9N2 group. Hence, feed-borne B. cereus contamination potentially exacerbates gizzard ulceration and aggravates H9N2-induced respiratory distress by inhibiting antibody-mediated immunity and pathogen clearance. Thus controlling the B. cereus contamination in poultry feed is immediately needed.

Limited adaptation of chimeric H9N2 viruses containing internal genes from bat influenza viruses in chickens

Influenza virus-like sequences of H17N10 and H18N11 were identified in bats, despite there has been no live virus isolated. The genetic analysis indicated that they have distinct but relatively close evolutionary relationships to known influenza A viruses. However, the infectivity and adaptation of bat influenza viruses in avian species remain unclear. In this study, two modified bat influenza viruses cH9cN2/H17 and cH9cN2/H18 containing HA and NA coding regions replaced with those of H9N2 influenza A virus were generated in the background of the H17N10 or H18N11 viruses. These two modified viruses replicated less efficiently than wild type H9N2 virus in cultured chicken cells. The mini-genome assay showed that viral ribonucleoproteins (vRNPs) of H9N2 has significantly higher polymerase activity than that of bat influenza viruses in avian cells. In chicken study, compared with H9N2 virus, which replicated and transmitted efficiently in chickens, the cH9cN2/H17 and cH9cN2/H18 viruses only replicated in chicken tracheas with lower titers. Pathological examination showed that the H9N2 caused severer lesions in lung and trachea than the modified bat influenza viruses. Notably, the cH9cN2/H18 transmitted among chickens, but not cH9cN2/H17, and chicken IFN-β antagonism results showed that H18N11 NS1 protein inhibited chicken IFN-β response more efficiently than H17N10 NS1 protein in avian cells. Taken together, our data indicated that the internal genes of bat influenza viruses adapted poorly to chickens, while the internal genes of H18N11 seemed to adapt to chickens better than H17N10.

Study of the underlying mechanisms and consequences of pathogenicity differences between two in vitro selected G1-H9N2 clones originating from a single isolate

The G1-H9N2 avian influenza virus (AIV) has caused significant economic losses in the commercial poultry industry due to reduced egg production and increased mortality. The field observations have shown that H9N2 viruses circulate and naturally mix with other pathogens and these simultaneous infections can exacerbate disease. To avoid an incorrect virus characterization, due to co-infection, isolates were purified by in vitro plaque assays. Two plaque purified G1-H9N2 clones, selected on different cell types, named MDCK-and CEF-clone in regards to the cell culture used, were studied in vivo, revealing two different virulence phenotypes. Subsequently, the underlying mechanisms were studied. Specifically, the phenotypical outcome of SPF bird infection by the two clones resulted in completely different clinical outcomes. These differences in clinical outcome were used to study the factors behind this output in more detail. Further studies demonstrated that the more severe disease outcome associated with the MDCK-clone involves a strong induction of pro-inflammatory cytokines and a lack of type I interferon production, whereas the mild disease outcome associated with the CEF-clone is related to a greater antiviral cytokine response. The immunosuppressive effect of the MDCK-clone on splenocytes was further demonstrated via ChIFN-γ lack production after ex vivo mitogenic stimulation. Genome sequencing of the two clones identified only four amino acid differences including three in the HA sequence (HA-E198A, HA-R234L, HA-E502D-H9 numbering) and one in the NA sequence (NA-V33M). In the present study, valuable insights on the mechanisms responsible for AI pathogenicity and molecular mechanisms of H9N2 infections in chicken were obtained while highlighting the impact of the cells viruses are grown on their virulence.

A G1-lineage H9N2 virus with oviduct tropism causes chronic pathological changes in the infundibulum and a long-lasting drop in egg production

Since 1997, G1-lineage H9N2 avian influenza viruses have been circulating in Asia and later on in the Middle East, and they have been associated to mild respiratory disease, drops in egg production and moderate mortality in chickens, in particular in the presence of concurrent infections. In this study, we investigated the importance of the G1-lineage H9N2 A/chicken/Israel/1163/2011 virus as a primary pathogen in layers, analyzing its tropism and binding affinity for the oviduct tissues, and investigating the long-term impact on egg production. Besides causing a mild respiratory infection, the virus replicated in the oviduct of 60% of the hens causing different degrees of salpingitis throughout the organ, in particular at the level of the infundibulum, where the detection of the virus was associated with severe heterophilic infiltrate, and necrosis of the epithelium. Binding affinity assays confirmed that the infundibulum was the most receptive region of the oviduct. The drop in egg production was at its peek at 2 weeks post-infection (pi) (60% decrease) and continued up to 80 days pi (35% decrease). On day 80 pi, non-laying birds showed egg yolk peritonitis, and histopathological analyses described profound alteration of the infundibulum architecture, duct ectasia and thinning of the epithelium, while the rest of the oviduct and ovary appeared normal. Our results show that this H9N2 virus is a primary pathogen in layer hens, and that its replication in the infundibulum is responsible for acute and chronic lesions that limits the effective functionality of the oviduct, compromising the commercial life of birds.

Development and evaluation of novel recombinant adenovirus-based vaccine candidates for infectious bronchitis virus and Mycoplasma gallisepticum in chickens

Avian infectious bronchitis caused by the infectious bronchitis virus (IBV), and mycoplasmosis caused by Mycoplasma gallisepticum (MG) are two major respiratory diseases in chickens that have resulted in severe economic losses in the poultry industry. We constructed a recombinant adenovirus that simultaneously expresses the S1 spike glycoprotein of IBV and the TM-1 protein of MG (pBH-S1-TM-1-EGFP). For comparison, we constructed two recombinant adenoviruses (pBH-S1-EGFP and pBH-TM-1-EGFP) that express either the S1 spike glycoprotein or the TM-1 protein alone. The protective efficacy of these three vaccine constructs against challenge with IBV and/or MG was evaluated in specific pathogen free chickens. Groups of seven-day-old specific pathogen free chicks were immunized twice, two weeks apart, via the oculonasal route with the pBH-S1-TM-1-EGFP, pBH-S1-EGFP, or pBH-TM-1-EGFP vaccine candidates or the commercial attenuated infectious bronchitis vaccine strain H52 and MG vaccine strain F-36 (positive controls), and challenged with virulent IBV or MG two weeks later. Interestingly, by days 7 and 14 after the booster immunization, pBH-S1-TM-1-EGFP-induced antibody titre was significantly higher (P < 0.01) compared to attenuated commercial IBV vaccine; however, there was no significant difference between the pBH-S1-TM-1-EGFP and attenuated commercial MG vaccine groups (P > 0.05). The clinical signs, the gross, and histopathological lesions scores of the adenovirus vaccine constructs were not significantly different from that of the attenuated commercial IBV or MG vaccines (positive controls) (P > 0.05). These results demonstrate the potential of the bivalent pBH-S1-TM-1-EGFP adenovirus construct as a combination vaccine against IB and mycoplasmosis.

Co-infection of Chlamydia psittaci with H9N2, ORT and Aspergillus fumigatus contributes to severe pneumonia and high mortality in SPF chickens

Since 2007, most areas of China have seen outbreaks of poultry airsacculitis, which causes hugely economic losses to the poultry industry. However, there are no effective measures to combat the problem. In this study, 105 rations were collected to isolate Aspergillus spp. from the diseased farms. In subsequent experiments, SPF chickens were inoculated with Ornithobacterium rhinotracheale (ORT), Chlamydia psittaci (C. psittaci) and Aspergillus fumigatus (A. fumigatus), and mortality rate, body weight gain and lesion score were evaluated. Of these ration samples, 63 (60.0%) were A. fumigates, 21 (20.0%) were Aspergillus niger (A. niger) and 11 (10.5%) were Aspergillus candidus (A. candidus). Furthermore, SPF birds infected with C. psittaci, ORT, H9N2 virus and A. fumigatus conidia exhibited a mortality rate of 40%, while simultaneous co-infection with C. psittaci, ORT and A. fumigatus resulted in a mortality rate of 20%. The avian airsacculitis was manifested in the C. psittaci + ORT/A. fumigatus, C. psittaci + H9N2 + ORT/A. fumigatus and C. psittaci + H9N2/A. fumigatus groups while others had transient respiratory diseases without mortality. Our survey indicates that feed-borne A. fumigatus is prevalent in poultry rations. The combination of C. psittaci, ORT, H9N2 and A. fumigatus conidia contributes to the replication of avian airsacculitis by aggravating the severe damage to the air sacs and lungs of chickens.

Different breeds, different blood: Cytometric analysis of whole blood cellular composition in chicken breeds

While haematological variation is well known in birds, variation in avian breeds (distinct morphotypes of the same species) remains unexplored. Poultry breeds, in particular, may show interesting evolutionary patterns and economically-relevant physiological differences. We performed a comparative examination of blood cellular composition in five chicken (Gallus gallus domesticus) breeds: Araucana, Booted bantam, Czech, Minorca and Rosecomb bantam. In standard-environment-reared hens whole-blood flow cytometry revealed remarkable differences in most erythrocyte- and leukocyte-related parameters. We identified two extremes: Czech, a European breed, with a low heterophil/lymphocyte (H/L) ratio and high CD4⁺ levels, and Araucana, a South-American breed, with a high H/L ratio and high relative monocyte count. Such variation may reflect a combination of artificial and natural selection acting on health- and stress-related traits in domestic populations. Different breeds have evolved different immunological adaptations reflecting their original need to fight pathogens and physiological constraint resulting from dissimilar physiological trade-offs.