Increased mast cell density during the infection with velogenic Newcastle disease virus in chickens

Protective effects of rabbit sacculus-derived antimicrobial peptides on SPF chicken against infection with very virulent infectious bursal disease virus

Previous studies here have demonstrated that the rabbit sacculus rotundus-derived antimicrobial peptides (RSRP) could alter the intestinal mucosal immune responses in specific-pathogen-free (SPF) chickens, however, the protective effects of RSRP on chickens against infection remain questionable. In the present study, eighty SPF chickens were randomly divided into five groups and challenged with very virulent infectious bursal disease virus (vvIBDV) to determine the protective effects and its underlying mechanism of RSRP. Histopathology examination found that vvIBDV-infection caused severe damage in the bursa of Fabricius, especially the bursal lymphoid follicles underwent severe necrosis, depletion, hemorrhage, and edema. Unexpectedly, RSRP intervention significantly reduced the necrosis and depletion of lymphoid follicles in the vvIBDV-infected chickens. Moreover, RSRP treatment significantly decreased the expression of Bax (P < 0.01) as well as remarkably promoted the expression of Bcl-2 (P < 0.01), concomitantly alleviated the excessive apoptosis in the immune organs such as the bursa of Fabricius during vvIBDV infection. Notably, consistent with our previous reports that increased mast cell activation and degranulation in the bursa after vvIBDV infection, RSRP administration considerably reduced the mast cell density and the expression of tryptase, a marker for activated mast cells. Collectively, the present study indicates that rabbit sacculus rotundus-derived antimicrobial peptides could effectively protect the major immune organs including the bursa of Fabricius from the damage caused by vvIBDV infection, which provides the possibility and a promising perspective for the future application of antimicrobial peptides for poultry production.

Response of three local chicken ecotypes of Ghana to lentogenic and velogenic Newcastle disease virus challenge

This study was carried out to assess the response of three Ghanaian local chicken ecotypes to LaSota (lentogenic) and virulent field strains of Newcastle disease virus (NDV). Local chickens sampled from the Interior Savannah (IS), Forest (FO) and Coastal Savannah (CS) agro-ecological zones were bred and their offspring were challenged with LaSota NDV at 4 weeks of age. The LaSota challenge was replicated four times with different chicken groups. A total of 1438 chicks comprising 509 Coastal Savannah, 518 Forest and 411 Interior Savannah ecotypes were used. Pre- and post-challenge anti-NDV antibody titre levels were determined via ELISA assays. A second trial was conducted by introducing sick birds infected with virulent NDV to a flock of immunologically naïve chickens at 4 weeks old. Body weights were measured pre- and post-infection. Sex of the chickens was determined using a molecular method. In both trials, there was no significant difference among ecotypes in body weight and growth rate. In the LaSota trial, anti-NDV antibody titre did not differ by ecotype or sex. However, there was a positive linear relationship between body weight and antibody titre. In the velogenic NDV trial, survivability and lesion scores were similar among the three ecotypes. This study confirms that a relatively high dose of LaSota (NDV) challenge has no undesirable effect on Ghanaian local chicken ecotypes. All three Ghanaian local chicken ecotypes were susceptible to velogenic NDV challenge. Resistance to NDV by Ghanaian local chickens appears to be determined more by the individual's genetic makeup than by their ecotype.

Evaluation of chickens infected with a recombinant virulent NDV clone expressing chicken IL4

BACKGROUND

There is evidence that chicken IL4 (chIL4) functions similarly to its mammalian analogue by enhancing type 2 T helper (Th2) humoral immunity and promoting protection against parasitic infections; however, no studies have been performed to assess the effect of chIL4 on the pathogenesis of Newcastle disease (ND). To assess the role of chIL4 in velogenic NDV pathogenesis we created a vNDV infectious clone expressing chIL4. We hypothesized that co-expression of chIL4 during virus replication would result in decreased inflammation caused by the Th1 response and thereby increasing survival to challenge with vNDV.

METHODS

To evaluate the effect of chIL4 during early infection with velogenic Newcastle disease virus (NDV) in chickens, recombinant NDV clones expressing either chIL4 (rZJ1-IL4) or a control expressing green fluorescent protein (rZJ1-GFP) were created by inserting an expression cassette in an intergenic region of the NDV genome. The pathogenesis of rZJ1-IL4 was assessed in 4-week-old specific pathogen free chickens. The extent of virus replication was evaluated by titration in mucosal secretions and immunohistochemistry in multiple tissues. Expression of chIL4 was confirmed in tissues using immunohistochemistry.

RESULTS

Infection of birds with the rZJ1-IL4 resulted in successful viral replication in vivo and in vitro and generation of the chIL4 in tissues. All birds were clinically normal 2 DPI, with one bird in each group showing conjunctival swelling and enlarged spleens grossly. At 5 DPI, moderate or severe depression was observed in birds infected with rZJ1-GFP or rZJ1-IL4, respectively. Neurological signs and thymic atrophy were observed in one bird infected with rZJ1-IL4. Grossly, conjunctival swelling, mottled spleen and proventricular hemorrhages were observed at 5 DPI in one bird from each group. At 5 DPI, severe necrosis in the spleen, bursa and cecal tonsils were observed in birds infected with rZJ1-GFP, along with minimal evidence of chIL4 expression. In contrast, splenic atrophy, and moderate necrosis in the bursa and cecal tonsils were observed in birds infected with rZJ1-IL4. In addition, chIL4 signal was found in all tissues of rZJ1-IL4 birds at 5DPI.

CONCLUSIONS

The production of chIL4 by a recombinant NDV strain resulted in the activation of the positive feedback loop associated with IL4 production. Insertion of chIL4 into NDV may decrease necrosis to lymphoid organs while increasing the severity of lymphoid atrophy and prolonged disease. However, with a low number of birds it is difficult to determine whether these results are significant to disease outcome.

Molecular and pathological characterisation of genotype VII Newcastle disease virus on Egyptian chicken farms during 2016-2018

Newcastle disease virus (NDV) remains a constant threat to the poultry industry even with intensive vaccination programmes. In the present study, 40 samples were collected from farms showing high mortalities in some Egyptian governorates between 2016 and 2018. Tracheal samples were collected for virus isolation and confirmed by real-time RT-PCR. Molecular characterisation was performed by sequencing, followed by phylogenetic analysis of the novel sequences. Histopathological and immunohistochemical examinations were performed on different organs from NDV-infected broilers. The phylogenetic analysis revealed that the NDV isolates from different areas of Egypt were genetically closely related and all belonged to genotype VII. The histopathological hallmarks included haemorrhagic tracheitis, interstitial pneumonia with syncytia formation, haemorrhagic proventriculitis, necrotising pancreatitis, pan-lymphoid depletion, non-suppurative encephalitis and nephritis. Immunological detection of NDV antigen clarified the widespread presence of viral antigen in different organs with severe lesions. The present study confirmed that a virulent NDV of genotype VII became the predominant strain, causing severe outbreaks in poultry farms in Egypt. The presence of viral antigen in different organs indicates the pantropic nature of the virus. Immunohistochemistry was a very useful diagnostic tool for the detection of NDV antigen.

Physiological responses to central and peripheral injections of compound 48/80 and histamine in chicks

Mast cells are a type of immune cell widely distributed in the body of vertebrates. Mast cells have many granules that contain several bioactive molecules such as histamine, and these molecules are released through degranulation when the mast cell receives certain stimuli. Because the number of mast cells increases during infection in chickens (Gallus gallus), the activity of mast cells might be related to non-specific symptoms such as anorexia under an infectious condition. Therefore, the purpose of the present study was to investigate whether intraperitoneal (IP) and intracerebroventricular (ICV) injections of compound 48/80, which induces degranulation of mast cells, affects feeding, voluntary activity, cloacal temperature, and the concentrations of plasma corticosterone (CORT) and glucose in chicks. The effect of histamine, which is found in mast cell granules, on these parameters was also investigated. IP injection of compound 48/80 significantly decreased food intake, voluntary activity, and cloacal temperature, and increased plasma CORT concentration in the chicks. While ICV injection of compound 48/80 also decreased food intake, it increased cloacal temperature and plasma glucose concentration. Both IP and ICV injections of histamine significantly decreased food intake, cloacal temperature, and plasma CORT concentration. However, only IP injection of histamine significantly decreased voluntary activity and increased plasma glucose concentration. The results suggest that degranulation of mast cells is related to non-specific symptoms in chicks, although the mechanism seems to be different between peripheral and central tissues. In addition, the effect of peripherally-injected compound 48/80 may be partly mediated by histamine.

Mast Cells and Natural Killer Cells-A Potentially Critical Interaction

Natural killer (NK) cells play critical roles in host defense against infectious agents or neoplastic cells. NK cells provide a rapid innate immune response including the killing of target cells without the need for priming. However, activated NK cells can show improved effector functions. Mast cells are also critical for early host defense against a variety of pathogens and are predominately located at mucosal surfaces and close to blood vessels. Our group has recently shown that virus-infected mast cells selectively recruit NK cells and positively modulate their functions through mechanisms dependent on soluble mediators, such as interferons. Here, we review the possible consequences of this interaction in both host defense and pathologies involving NK cell and mast cell activation.

Compound 48/80 reduces the crop-emptying rate, likely through a histamine-associated pathway in chicks

Infectious conditions are associated with reduced food passage through the digestive tract in both mammals and chicks; however, the precise mechanism mediating this response in chicks remains unclear. The purpose of the present study was to determine if mast cells, a blood cell type which plays an important role in the immune system, might affect food passage through the digestive tract in chicks. Specifically, we performed intraperitoneal (IP) injections of compound 48/80, an inducer of mast cell degranulation, and measured crop emptying. The IP injection of compound 48/80 significantly reduced the crop-emptying rate, but it did not affect the proventriculus to small intestine transit rate or the number of defecations. We also found that IP-injected histamine, which is secreted by mast cells, also reduced the crop-emptying rate. In addition, IP injection of 2-pyridylethylamine (histamine H1 receptor agonist), but not dimaprit, (R)-(-)-α-methylhistamine, and VUF8430 (histamine H2, H3, and H4 receptor agonists, respectively), reduced the crop-emptying rate, implying that histamine reduces the crop emptying rate via the histamine H1 receptor. Finally, we found that IP injection of compound 48/80 reduced mRNA expression of histidine decarboxylase, a rate-limiting enzyme for histamine synthesis, in the esophagus and proventriculus at 1 h and the proventriculus and duodenum at 3 h after the injection. In sum, the present study suggests that the degranulation of mast cells causes a reduction in the crop-emptying rate, possibly via the histamine pathway in chicks.

The therapeutic effects of sodium cromoglycate against influenza A virus H5N1 in mice

Objectives

To identify the protective role of sodium cromoglycate in mice during influenza virus infection.

Design

H5N1 virus‐infected mice were treated with the mast cell stabilizer sodium cromoglycate (SCG) to investigate its therapeutic effect.

Sample

The nose, trachea and lungs from mice were collected.

Main outcome measures

Virus replication and host responses were determined by plaque assay, quantitative PCR, immunohistochemistry, and histology.

Results

SCG‐treated mice survived better than did PBS‐treated mice after H5N1 virus infection. Mild pathological changes with fewer inflammatory cell infiltration and fewer virus antigens were observed in the nose, trachea, and lungs of SCG‐treated mice on days 3 and 5 post‐infection. However, no significant changes in viral load in the lungs were detected between SCG‐ and PBS‐treated mice. Furthermore, significantly decreased expression of interleukin‐6, tumor necrosis factor‐a, Toll‐like receptor 3, and TIR‐domain‐containing adapter‐inducing interferon‐b was detected in the lungs of SCG‐treated mice, and no higher expression of interferon‐c was detected.

Conclusion

These results suggest that SCG has therapeutic roles in H5N1 virus‐infected mice by alleviating the inflammatory response rather than inhibition of viral replication in the lungs.

Vitamin A dietary supplementation reduces the mortality of velogenic Newcastle disease significantly in cockerels

This project was undertaken to find ways of reducing mortalities and economic losses due to velogenic Newcastle disease (VND) in areas where the disease is enzootic. Four groups of cockerels of 44 birds each were used for this experiment. The birds in groups 1 and 2 received no dietary vitamin A supplementation, whereas groups 3 and 4 received 300 iu and 600 iu of vitamin A per kilogram of commercial feed, respectively, from 1 week of age till the end of the experiment. At 6 weeks of age, the birds in groups 2, 3 and 4 were inoculated intraocularly with a VND virus (duck/Nigeria/Plateau/Kuru/113/1991). The birds in Group 1 were given phosphate-buffered saline intraocularly. Clinical signs appeared in Group 2 birds on day 3 PI and in groups 3 and 4 on day 5 PI. The clinical signs included a drop in feed and water consumption, depression, diarrhoea, torticollis and paralysis in all the infected groups. The average body weights of all groups were significantly different from one another on day 14 PI with Group 2 birds having the lowest body weight. Mortalities were highest in Group 2 birds (0%, 93.18%, 72.73% and 56.82% in groups 1, 2, 3 and 4 respectively). The antibody response in all the groups was significantly different from one another on days 14 and 21 PI. Group 2 birds had the lowest titres on those 2 days and showed more severe atrophy of the bursa, spleen, thymus and fibrin deposition in the spleen and thymus than the birds in groups 3 and 4. The above observations show that vitamin A dietary supplementation delayed the onset of clinical signs and significantly reduced body weight loss, atrophy of the bursa, spleen and thymus, and mortalities by 36%. It also significantly potentiated haemagglutination inhibition antibody response.

Hyperpigmentation Results in Aberrant Immune Development in Silky Fowl (Gallus gallus domesticus Brisson)

The Silky Fowl (SF) is known for its special phenotypes and atypical distribution of melanocytes among internal organs. Although the genes associated with melanocyte migration have been investigated substantially, there is little information on the postnatal distribution of melanocytes in inner organs and the effect of hyperpigmentation on the development of SF. Here, we analyzed melanocyte distribution in 26 tissues or organs on postnatal day 1 and weeks 2, 3, 4, 6, 10, and 23. Except for the liver, pancreas, pituitary gland, and adrenal gland, melanocytes were distributed throughout the body, primarily around blood vessels. Interaction between melanocytes and the tissue cells was observed, and melanin was transported by filopodia delivery through engulfed and internalized membrane-encapsulated melanosomes. SFs less than 10 weeks old have lower indices of spleen, thymus, and bursa of Fabricius than White Leghorns (WLs). The expression levels of interferon-γ and interlukin-4 genes in the spleen, and serum antibody levels against H5N1 and infectious bursal disease virus were lower in SF than in WL. We also found immune organ developmental difference between Black-boned and non-Black- boned chickens from SFs and WLs hybrid F2 population. However, degeneration of the thymus and bursa of Fabricius occurred later in SF than in WL after sexual maturity. Analysis of apoptotic cells and apoptosis-associated Bax and Bcl-2 proteins indicated that apoptosis is involved in degeneration of the thymus and bursa of Fabricius. Therefore, these results suggest that hyperpigmentation in SF may have a close relationship with immune development in SF, which can provide an important animal model to investigate the roles of melanocyte.

Mast cells and influenza a virus: association with allergic responses and beyond

Influenza A virus (IAV) is a widespread infectious agent commonly found in mammalian and avian species. In humans, IAV is a respiratory pathogen that causes seasonal infections associated with significant morbidity in young and elderly populations, and has a large economic impact. Moreover, IAV has the potential to cause both zoonotic spillover infection and global pandemics, which have significantly greater morbidity and mortality across all ages. The pathology associated with these pandemic and spillover infections appear to be the result of an excessive inflammatory response leading to severe lung damage, which likely predisposes the lungs for secondary bacterial infections. The lung is protected from pathogens by alveolar epithelial cells, endothelial cells, tissue resident alveolar macrophages, dendritic cells, and mast cells. The importance of mast cells during bacterial and parasitic infections has been extensively studied; yet, the role of these hematopoietic cells during viral infections is only beginning to emerge. Recently, it has been shown that mast cells can be directly activated in response to IAV, releasing mediators such histamine, proteases, leukotrienes, inflammatory cytokines, and antiviral chemokines, which participate in the excessive inflammatory and pathological response observed during IAV infections. In this review, we will examine the relationship between mast cells and IAV, and discuss the role of mast cells as a potential drug target during highly pathological IAV infections. Finally, we proposed an emerging role for mast cells in other viral infections associated with significant host pathology.

Highly pathogenic porcine reproductive and respiratory syndrome virus infection results in acute lung injury of the infected pigs

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) was firstly characterized in 2006 in China. The virus has caused great economic loss to the Chinese swine production during the past years. Herein, we experimentally infected SPF pigs using two strains of PRRSV with different pathogenicity and observed the lung pathological changes looking for new sights on the possible pathogenesis associated with the virulence of HP-PRRSV. The results indicated that the HP-PRRSV-infected pigs died and exhibited severe pathological changes of lungs featuring increased neutrophils, mast cells and mononuclear macrophages, compared with the pigs inoculated with low pathogenic (LP-) PRRSV. Furthermore, the pigs infected with HP-PRRSV showed the higher levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, interleukin (IL)-8 and histamine, leukotriene B4 (LTB4), platelet activation factor (PAF) in sera than those inoculated with LP-PRRSV. Additionally, the fibrosis of lung was observed in the HP-PRRSV-infected pigs. At present, our findings suggest that the aberrant immune responses triggered by HP-PRRSV infection are closely related to acute lung injury (ALI), and especially the pathological changes in lung vascular system are of particular significance. These associated pathological changes of lung are in part responsible for the additional morbidity and mortality observed in HP-PRRSV infection.

Detection of intestinal intraepithelial lymphocytes, goblet cells and secretory IgA in the intestinal mucosa during Newcastle disease virus infection

Newcastle disease, which is caused by Newcastle disease virus (NDV), is a highly contagious viral disease of poultry and other bird species. The mucosa is the first line of defence to invading pathogens, including NDV, and it has been confirmed that the mucosa can contribute to host protection. This study was conducted to evaluate the intestinal mucosal immunology in NDV infection. Forty specific-pathogen-free chickens were divided into two groups, 20 birds in each group. Group 1 was inoculated with NDV by the intravenous route. Group 2 was used as the control group and was given sterile phosphate-buffered saline by the same route. At 24, 48, 72, and 96 h post infection (h.p.i.), five chickens from each treatment were killed. Samples of the duodenum, jejunum, and ileum were collected to quantify intestinal intraepithelial lymphocytes (IEL), goblet cells and secretory IgA (sIgA) by cytochemistry and immunohistochemistry analysis. The results indicated that IEL were increased from 24 to 72 h.p.i. in the infected tissues, and were significantly higher than in the control group at 48 h.p.i. (P < 0.01). In contrast to IEL, goblet cell numbers were reduced dramatically from 24 to 96 h.p.i. in the infected birds (P < 0.01) Furthermore, the content of sIgA was significantly higher at 48 and 72 h.p.i. in the infected tissues (P < 0.01). sIgA positivity was observed in the epithelial lining of the intestinal mucosa. These data suggest that IEL, goblet cells, and sIgA were involved in the intestinal mucosal immunity against NDV infection.

Reduced mucosal injury of SPF chickens by mast cell stabilization after infection with very virulent infectious bursal disease virus

Recent studies here have demonstrated that increased mast cell populations and tryptase activity contribute to lesion formation in regions of immune organs in special-pathogen-free chickens after infection with very virulent infectious bursal disease virus (vvIBDV). Mast cells and their mediators have been implicated in acute inflammatory injury after vvIBDV infection, but their precise role in this process remains elusive. In this study, the role of mast cells in the vvIBDV infection process was examined using ketotifen, a mast cell membrane stabilizer. On days 1, 2, and 3 postinfection, the bursa of Fabricius (BFs) were collected to quantify mast cells, tryptase and histamine contents by cytochemistry, immunohistochemistry and fluorospectrophotometry analyses, respectively. The results showed that the mast cell populations, tryptase expression, and histamine released increased significantly in the BFs (p<0.01) of infected birds compared to controls, and acute inflammatory responses were observed in the former. In contrast, in infected chickens pretreated with ketotifen, mast cells, tryptase, and histamine were markedly decreased (p<0.01) and probably as a result, the BFs remitted significantly. The overall results suggest that mast cells are positively involved in BF injury induced by vvIBDV infection. Inhibition of mast cell degranulation and concurrent mediator release may represent a novel strategy to modulate this process. This study, thus, advances the understanding of the acute inflammatory injury mechanisms triggered by vvIBDV infection and the contribution of mast cell activity in this process.

Evidence for a role of mast cells in the mucosal injury induced by Newcastle disease virus

We have previously demonstrated that mast cells were significantly increased during Newcastle disease virus (NDV) infection, but their precise role in the process is unknown. In this study, we investigated the role of mast cells in this process by using ketotifen, a mast cell membrane stabilizer. A total of 60 specific-pathogen-free chickens were randomly divided into 3 groups of 20 birds each (NDV-infected group, ketotifen-pretreated group, and the control group). The ketotifen-pretreated group was administered orally with ketotifen before NDV infection. On 12, 24, and 48 h postinfection, 5 chickens from each treatment were killed. Tissues of proventriculus were collected to quantify mast cells, the content of tryptase and histamine by cytochemistry, immunohistochemistry, and fluorescence analysis, respectively. The results showed that the population of mast cells and the content of tryptase and histamine were increased significantly in the proventriculus (P < 0.01) of infected birds compared with the control group. An acute mucosal injury was observed in the infected chickens. In contrast, among chickens pretreated with ketotifen, followed by NDV infection, the mast cells number and the content of tryptase and histamine were decreased significantly (P < 0.01). Likely as a result, the mucosal injury was remitted remarkably. The overall results of this experiment suggest that mast cells are implicated in NDV-induced mucosal injury. Inhibition of mast cell mediator release may represent a novel strategy to modulate this process.