Infectious Bursal Disease Virus Vaccine Research Articles

Isolation and molecular characterization of very virulent infectious bursal disease virus from Egypt

In Egypt, the poultry industry is plagued by the significant economic losses caused by the infectious bursal disease virus (IBDV). In the present study, a total of 30 diseased commercial chicken flocks aged 23–41 days old in three Egyptian governorates (Fayoum, Beni-Suef, and Minya) having symptoms consistent with IBDV were examined. The collected bursal samples (n=30, ten pooled bursae for each flock) were screened by RT-PCR to amplify the IBDV VP2 gene. Results revealed that 20 out of 30 samples were positive, as indicated by the amplification of 620 bp of the VP2 gene. The twenty positive samples were inoculated into specific pathogen-free embryonated chicken eggs (SPF-ECEs) via the chorioallantoic-membrane (CAM) route to isolate the suspected virus. Eight samples were successfully isolated and were subjected to a partial sequence of VP2 (targeting the HVR). The nucleotide sequences and phylogenetic analysis revealed that the examined isolates exhibited amino acids A222, I256, I294, and S299, which are extremely conserved among very virulent (vv)IBDV. The amino acid sequence analysis of the eight isolates revealed a high degree of similarity (97-100%) in between and 90-100% similarity compared to other Egyptian vvIBDV strains. In contrast, lower similarity was observed with attenuated IBDV vaccine strains D78, Lukert, and Bursavac (91-93%, 91-93%, and 92-94%, respectively). In conclusion, this study underscores the importance of ongoing surveillance of the IBDV situation in the field, as well as the need for further research to investigate the efficacy of current vaccination strategies to curb IBDV infection.

Effects of ultra-filtration purification of infectious bursal disease virus on immune responses and cytokine activation in specific pathogen free chickens.

Purification is an important step in the production of viral vaccines that strongly affects product recovery and subsequent immune responses. The present study was carried out with the aim of improving the purification of infectious bursal disease virus (IBDV) by the tangential flow filtration (TFF) method. Then, the effect of the purified virus on the induction of immune responses against IBDV in specific pathogen free (SPF) chickens was investigated. The IBD07IR strain was propagated in embryonated SPF eggs. The virus was purified using a 100 kDa cassette. The quality of the recovered viruses was evaluated by titration. A total number of 60 SPF chickens were randomly divided into three groups (n = 20) and received the concentrated viral antigen, commercial live IBDV vaccine and phosphate-buffered saline at the age of 3 weeks by eye drop method. The bursa of Fabricius was examined histopathologically for possible changes. Sera were collected at 1-week intervals from day 0 until the end of 6 weeks after vaccination. The IBDV-specific antibody levels, induction of cell-mediated immunity and mRNA expression levels of cytokines were evaluated. The results showed that despite a relative raise in virus titer from 7.66 to 8.17 embryo infectious dose (EID)50 mL-1 following purification, both the purified IBDV and commercial vaccine are able to induce strong immune responses against the virus. Within a context of egg-based IBDV vaccine production, a single-step TFF can be applied for the relatively purification. This platform requires a further study in the selection of multiple membranes to optimize the operating conditions and final product.

Stress-induced immunosuppression inhibits immune response to infectious bursal disease virus vaccine partially by miR-27b-3p/SOCS3 regulatory gene network in chicken

Stress-induced immunosuppression inhibits immune response to infectious bursal disease virus vaccine partially by miR-27b-3p/SOCS3 regulatory gene network in chicken

Overexpression of glutathione synthetase gene improving redox homeostasis and chicken infectious bursal disease virus propagation in chicken embryo fibroblast DF-1

Infectious bursal disease (IBD) of chickens is an acute, high-contact, lytic infectious disease caused by infectious bursal disease virus (IBDV). The attenuated inactivated vaccine produced by DF-1 cells is an effective control method, but the epidemic protection demands from the world poultry industry remain unfulfilled. To improve the IBDV vaccine production capacity and reduce the economic losses caused by IBDV in chicken, cellular metabolic engineering is performed on host cells. In this study, when analyzing the metabolomic after IBDV infection of DF-1 cells and the exogenous addition of reduced glutathione (GSH), we found that glutathione metabolism had an important role in the propagation of IBDV in DF-1 cells, and the glutathione synthetase gene (gss) could be a limiting regulator in glutathione metabolism. Therefore, three stable recombinant cell lines GSS-L, GSS-M, and GSS-H (gss gene overexpression with low, medium, and high mRNA levels) were screened. We found that the recombinant GSS-M cell line had the optimal regulatory effect with a 7.19 ± 0.93-fold increase in IBDV titer. We performed oxidative stress and redox status analysis on different recombinant cell lines, and found that the overexpression of gss gene significantly enhanced the ability of host cells to resist oxidative stress caused by IBDV infection. This study established a high-efficiency DF-1 cells system for IBDV vaccine production by regulating glutathione metabolism, and underscored the importance of moderate gene expression regulation on the virus reproduction providing a way for rational and precise cell engineering.Graphical

Immunization and Host Responses to MB-1, a Live Hatchery Vaccine against Infectious Bursal Disease.

MB-1 is an attenuated infectious bursal disease virus vaccine. Previously, we observed a temporal delay of vaccine virus replication in the bursae of chicks due to maternally derived antibodies (MDAs). The mechanism that allowed its survival despite MDA neutralization remained unclear. We hypothesized that after vaccination at 1 day of age (DOA), the MB-1 virus penetrates and resides in local macrophages that are then distributed to lymphoid organs. Furthermore, MB-1's ability to survive within macrophages ensures its survival during effective MDA protection. PCR analysis of lymphoid organs from chicks with MDA, vaccinated on 1 DOA, demonstrated that the MB-1 virus was identified at low levels solely in the spleen pre-14 days of age. Fourteen days after vaccination, the virus was identified using PCR in the bursa, with viral levels increasing with time. The possible delay in viral colonization of the bursa was attributed to the presence of anti-IBDV capsid VP2 maternal IgA and IgY in the bursa interstitium. These indicate that during the period of high MDA levels, a small but viable MB-1 viral reservoir was maintained in the spleen, which might have served to colonize the bursa after MDA levels declined. Thereafter, individual immunization of chicks against Gumboro disease was achieved.

Studies on immunopathological changes induced by commercial IBD live vaccines in poultry birds

Intermediate plus live strain infectious bursal disease virus (IBDV) vaccines are used to control IBDV endemic infections in India. In the present study, immunopathological changes induced by commercial infectious bursal disease live vaccines with different immunization regimes were compared. A total of days old 108 Cobb broiler chicks were randomly divided into five groups with 24 chicks each in groups I, II, III and 18 chicks each in group IV and V. Group I served as control I (no immunization) and group II and III chicks were immunized with a single dose of vaccines 1 and 2 on 17th day of age (DOA), respectively. The group IV and V chicks were immunized with vaccines 1 and 2, respectively with primary dose on 17th DOA followed by booster dose on 24th DOA. Both intermediate plus live vaccines produced gross and histopathological lesions in lymphoid organs (bursa of Fabricius, thymus, spleen and caecal tonsils). Increased CD4 + , CD8 + T cells in affected bursa of Fabricius was evidenced by immunohistochemistry. Further, up-regulation in relative mRNA expression of IFN-γ, IL-1β and IL-6 were observed in bursa of Fabricius of treated birds, with maximum alteration particularly on 14th day post single immunization and 7th day post booster immunization. The findings suggest that single immunization regime on the 17th day of age showed immunization equivalent to booster immunization with lesser lesions, therefore, may be practiced and promoted in the field conditions for the better economic returns and animal welfare.

Genetic Insight into the Interaction of IBDV with Host-A Clue to the Development of Novel IBDV Vaccines.

Infectious bursal disease virus (IBDV) is an immunosuppressive pathogen causing enormous economic losses to the poultry industry across the globe. As a double-stranded RNA virus, IBDV undergoes genetic mutation or recombination in replication during circulation among flocks, leading to the generation and spread of variant or recombinant strains. In particular, the recent emergence of variant IBDV causes severe immunosuppression in chickens, affecting the efficacy of other vaccines. It seems that the genetic mutation of IBDV during the battle against host response is an effective strategy to help itself to survive. Therefore, a comprehensive understanding of the viral genome diversity will definitely help to develop effective measures for prevention and control of infectious bursal disease (IBD). In recent years, considerable progress has been made in understanding the relation of genetic mutation and genomic recombination of IBDV to its pathogenesis using the reverse genetic technique. Therefore, this review focuses on our current genetic insight into the IBDV's genetic typing and viral genomic variation.

Circular RNA circAKIRIN2 participates in the process of stress-induced immunosuppression affecting immune response to infectious bursal disease virus vaccine in chicken

At present, stress-induced immunosuppression is still a hidden threat that leads to immunization failure and outbreaks of poultry diseases, and causes huge economic losses to the modern poultry industry. However, the molecular mechanisms of stress-induced immunosuppression affecting viral vaccine immunity are still poorly understood. Here, we identified circAKIRIN2 as a conserved circular transcript in chicken, and explored its expression patterns in different immune states by quantitative real-time PCR (qRT-PCR), then conducted bioinformatics analysis. The results showed that circAKIRIN2 actively participated in the process of stress-induced immunosuppression affecting the immune response to infectious bursal disease virus (IBDV) vaccine. The key time points for circAKIRIN2 involving in the process were 2 day post immunization (dpi), 5 dpi, and 28 dpi, especially at the acquired immune stage. The important tissues that responded to the process included the heart, liver, and lung, all of which changed significantly. In addition, circAKIRIN2 as a competing endogenous RNA (ceRNA) sponging zinc finger and BTB domain containing 20 (ZBTB20) was a potential molecular mechanism for regulating immune functions in the process. In conclusion, circAKIRIN2 is a key regulatory factor for stress-induced immunosuppression affecting the IBDV vaccine immune response, and this study can provide a new perspective for exploring the molecular regulatory mechanisms of stress-induced immunosuppression affecting immune response.

Efficacy of different live infectious bursal disease vaccines on antibodies to infectious bursal disease virus and Newcastle disease vaccine La Sota in ISA brown chicks

Aim: In this study, the efficacy of five commercial live infectious bursal disease (IBD) vaccines on antibody (Ab) decay and response to a very virulent IBD virus (vvIBDV) and Newcastle disease (ND) vaccine La Sota in ISA Brown chicks were assessed. Methods: Seven groups of chickens (A, B, C, D, E, F, and G) comprising 50 chicks each were used for the study. Groups A, B, C, D, and E were vaccinated with Bur-706, MB-Strain, B87-Strain, Bursa-B2K, and HIPRA live IBD vaccines, respectively, at 14 and 28 days of age (doa), and challenged with a vvIBDV at 35 doa. Groups F and G served as positive and negative controls, respectively. At 42 doa, all groups were vaccinated with ND vaccine La Sota. Blood was collected at 1, 7, 14, 21, 28, 35, 42, and 49 doa, and serum was harvested. The serum was analyzed for IBD virus (IBDV) Ab titres using enzyme-linked immunosorbent assay (ELISA) and ND Ab titres using a haemagglutination inhibition (HI) test. Results: Results revealed significantly (p < 0.05) higher ELISA IBDV Ab titres in groups A to E than in F from 21 to 49 doa, with the highest in group D. At 49 doa, there was significantly (p < 0.05) higher HI Ab titre in groups A to E than in F with the highest in group D. In conclusion, the live IBDV vaccines were immunogenic following vaccination. The vaccines decreased the decay of IBDV Ab and mitigated the decreased response to ND vaccine La Sota in the chicks following the vvIBDV challenge, with more effects induced by Bursa-B2K. Conclusion: The live vaccines (Bur-706, MB-Strain, B87-Strain, Bursa-B2K, and HIPRA) were immunogenic following vaccination.

Modeling Infectious Bursal Disease Virus (IBDV) Antigenic Drift In Vitro

Infectious bursal disease virus (IBDV) vaccines do not induce sterilizing immunity, and vaccinated birds can become infected with field strains. Vaccine-induced immune selection pressure drives the evolution of antigenic drift variants that accumulate amino acid changes in the hypervariable region (HVR) of the VP2 capsid, which may lead to vaccine failures. However, there is a lack of information regarding how quickly mutations arise, and the relative contribution different residues make to immune escape. To model IBDV antigenic drift in vitro, we serially passaged a classical field strain belonging to genogroup A1 (F52/70) ten times, in triplicate, in the immortalized chicken B cell line, DT40, in the presence of sub-neutralizing concentrations of sera from birds inoculated with IBDV vaccine strain 2512, to generate escape mutants. This assay simulated a situation where classical strains may infect birds that have suboptimal vaccine-induced antibody responses. We then sequenced the HVR of the VP2 capsid at passage (P) 5 and 10 and compared the sequences to the parental virus (P0), and to the virus passaged in the presence of negative control chicken serum that lacked IBDV antibodies. Two escape mutants at P10 had the same mutations, D279Y and G281R, and a third had mutations S251I and D279N. Furthermore, at P5, the D279Y mutation was detectable, but the G281R mutation was not, indicating the mutations arose with different kinetics.

Comparative Safety, Immunogenicity, and Efficacy of CEF Cell-Based and DF-1 Cell Line Adapted Infectious Bursal Disease Vaccines in Specific-Pathogen-Free Chickens.

Infectious bursal disease (IBD) is an immunosuppressive and economically important disease of young chickens caused by infectious bursal disease virus (IBDV). The National Veterinary Institute (Bishoftu, Ethiopia) produces intermediate IBDV vaccine using primary chicken embryo fibroblast (CEF) cells, a method with technical and economical cumbersome. This study assessed the safety, immunogenicity, and efficacy of DF-1 cell line-adapted IBDV LC–75 vaccine strain in reference to the CEF-based vaccine. Confluent monolayer of DF-1 cells was infected with IBDV and cells with cytopathic effects were passaged until 3rd passage. Viral growth was confirmed using a one-step RT-PCR targeting IBDV VP2 gene. Viral titer increased from 1st passage through 3rd passage. Safety was assessed in 30 specific-pathogen-free chickens (15 chickens/group) injected with 10-fold field dose of each vaccine intraocularly and monitored for 21 days. For immunogenicity and efficacy, 60 specific-pathogen-free chickens were grouped into 3 (20 chickens/group). First and 2nd group received DF-1 cell and CEF-based IBDV vaccines, respectively. The 3rd group served as unvaccinated control. Antibody response was measured using iELISA. Chickens were challenged 4 weeks postvaccination with very virulent IBDV (vvIBDV) intraocularly and followed-up for 10 days. Vaccination did not cause any adverse reactions during the 21 days of follow-up. In addition, both vaccines induced higher antibody titer 14 and 24 days-post-vaccination as compared to unvaccinated controls (p < 0.05). Moreover, DF-1 and CEF-based IBDV LC–75 vaccines rendered a complete protection against vvIBDV. Contrarily, morbidity and mortality in unvaccinated chickens was 50% and 30%, respectively. The results indicated that DF-1 and CEF cell-based IBDV vaccines are comparably immunogenic and efficacious. Therefore, DF-1 cell-line can be considered an affordable and convenient alternative to the CEF-based approach. The suitability of DF-1 cells to grow other IBDV strains and safety of these vaccines on bursa of Fabricius should further be investigated.

A Walk through Gumboro Disease

Infectious bursal disease (IBD), caused by an Avibirnavirus, belonging to the family Birnaviridae, is an immunosuppressive disease that affects 3–6-week-old chickens, resulting in clinical or subclinical infection. Although clinical disease occurs in chickens, turkeys, ducks, guinea fowl, and ostriches can be also infected. IBD virus (IBDV) causes lymphoid depletion of the bursa, which is responsible for the severe depression of the humoral antibody response, primarily if this occurs within the first 2 weeks of life. IBD remains an issue in chicken meat production due to economic losses caused by the spread of variants or subtypes, resistant to the most common vaccines, responsible for a subclinical disease characterized by reduced growth performance and increased susceptibility to secondary infections. Very virulent strains of classical serotype 1 are also common in several countries and can cause severe disease with up to 90% mortality. This review mainly focuses on the immunosuppressive effect of the IBDV and potential vaccination strategies, capable of overcoming challenges associated with the optimal time for vaccination of offspring, which is dependent on maternal immunity and IBDV variant occurrence.

Efficacy of live attenuated, vector and immune complex infectious bursal disease virus (IBDV) vaccines in preventing field strain bursa colonization: A European multicentric study.

Infectious bursal disease virus (IBDV) is among the most relevant and widespread immunosuppressive agents, which can severely damage poultry farming by causing direct losses, predisposing the host to secondary diseases and reducing the efficacy of vaccination protocols against other infections. IBDV has thus been the object of intense control activities, largely based on routine vaccination. However, the need for protecting animals from the infection in the first period of the production cycle, when the bursa susceptibility is higher, clashes with the blanketing effect of maternally derived antibodies. To overcome this issue, other strategies have been developed besides live attenuated vaccines, including vector vaccines and immune complex (icx) ones. The present study aims to investigate, in field conditions, the efficacy of these approaches in preventing IBDV infection in laying chickens vaccinated with either live attenuated, vector or immune complex (icx) vaccines. For this purpose, a multicentric study involving 481 farms located in 11 European countries was organized and IBDV infection diagnosis and strain characterization was performed at 6 weeks of age using a molecular approach. Vaccine strains were commonly detected in flocks vaccinated with live or icx vaccines. However, a significantly higher number of field strains (characterized as very virulent IBDVs) was detected in flocks vaccinated with vector vaccines, suggesting their lower capability of preventing bursal colonization. Different from vector vaccines, live and icx ones have a marked bursal tropism. It can thus be speculated that vaccine virus replication in these sites could limit vvIBDV replication by direct competition or because of a more effective activation of innate immunity. Although such different behavior doesn't necessarily affect clinical protection, further studies should be performed to evaluate if vvIBDV replication could still be associated with subclinical losses and/or for viral circulation in a “vaccinated environment” could drive viral evolution and favor the emergence of vaccine-escape variants.

Commercial vaccines used in China do not protect against a novel infectious bursal disease virus variant isolated in Fujian.

Since 2018, atrophy of the bursa has been found among vaccinated chickens with high antibody titres against infectious bursal disease virus (IBDV) in Fujian, China, suggesting poor vaccine efficacy against circulating IBDV strains. Novel IBDV strains were isolated, and vp2 and vp1 genes were sequenced and used to carry out phylogenetic analysis. Pathogenicity was investigated using 21-day-old specific pathogen-free (SPF) chickens. In addition, the effectiveness of current commercial vaccines used in China was evaluated against the isolated novel IBDV strains. Six IBDV isolates were successfully obtained, which formed an independent cluster and belonged to genotype A2dB1, based on phylogenetic analysis of the vp2 and vp1 genes. The pathogenicity of the novel IBDV FJ2019-01 isolate in 21-day-old SPF chickens was characterised by severe atrophy of the bursa and a largely decreased number of lymphocytes, atrophy of the follicle and broadening of mesenchyme in the bursa 3-23 days after infection. Unfortunately, all vaccinated chickens with high antibody titres against IBDV also developed atrophy and largely decreased lymphocytes in the bursa, as in the unvaccinated birds challenged with FJ2019-01. Furthermore, high viral loads of FJ2019-01 were detected in the bursa of all vaccinated chickens. These findings suggest that current commercial IBDV vaccines used in China did not provide protection against novel IBDV variants.

A novel inactivated bivalent vaccine for chickens against emerging hepatitis-hydropericardium syndrome and infectious bursal disease

The emerging hepatitis-hydropericardium syndrome (HHS) caused by the novel genotype of fowl adenovirus 4 (FAdV-4) and the infectious bursal disease (IBD) caused by the infectious bursal disease virus (IBDV) are important avian diseases, both cause huge economic losses to the poultry industry. Therefore, it is necessary to develop an efficient and convenient FAdV-4/IBDV bivalent vaccine to prevent the spread of FAdV-4 and IBDV infections. Given that VP2 is the main structural protein and protective antigen of IBDV, we constructed a recombinant FAdV-4 expressing IBDV VP2 in our previous study. In the current study, an inactivated bivalent FAdV-4/IBDV vaccine was developed from the recombinant strain. The inactivated bivalent vaccine elicited effective and specific neutralizing antibodies against both FAdV-4 and IBDV in specific-pathogen-free chickens. Furthermore, the novel vaccine not only protected chickens from death caused by FAdV-4 and the very virulent IBDV (vvIBDV) infection, but also ameliorated target organ damage and reduced viral load. The FAdV-4-vectored vaccine developed in this study provides new options for the development of avian polyvalent inactivated vaccines and is a powerful tool for the prevention of both emerging HHS and IBD.

Molasses, Antox® and EN-FLORAX® decreased antibody decay rate and enhanced response to a very virulent infectious bursal disease virus and Newcastle disease vaccine La Sota in ISA Brown chicks

ABSTRACT This study evaluated the effects of molasses, Antox® and EN-FLORAX® on antibody (Ab) decay and response to a very virulent IBD virus (vvIBDV) and ND vaccine La Sota (NDVLS) in ISA Brown chicks. Five groups, (A, B, C, D and E) of 50 chicks each were used for the study. Groups A, B and C were supplemented with molasses, Antox® and EN-FLORAX®, respectively, orally from 1 to 49 days, and inoculated with a vvIBDV at 28 days of age. Groups D, and E were positive, and negative controls, respectively. At 35 days of age, all groups were vaccinated with NDVLS. Antibody (Ab) titers to vvIBDV, and NDV, were determined by indirect enzyme linked immunosorbent assay (I-ELISA), and hemagglutination-inhibition (HI) tests, respectively. Results revealed significantly (P < .05) decreased Ab decay rates in supplemented groups (A, B, and C) compared to controls (D and E) up to day 28. There were significantly (P < .05) higher mean IBDV and ND HI Ab titers in supplemented groups compared to D with the highest in A up to day 49. Molasses, Antox®, and EN-FLORAX® decreased rate of Ab decay, elicited stronger Ab response against vvIBDV and production of protective NDVLS HI Ab titers.

Detection and molecular characterization of a new genotype of infectious bursal disease virus in Portugal

ABSTRACT Infectious bursal disease virus (IBDV) is an immunosuppressive pathogen with a bi-segmented, double-stranded RNA genome. Two serotypes, named 1 and 2, are recognized, and serotype 1 is traditionally divided into classical, variant and very virulent strains. Despite having great practical relevance, this classification lacks standardization and may therefore generate confusion. The widespread adoption of molecular techniques, which allow direct assessment of either pathogenicity or antigenicity, further complicates this scenario. Recently, two phylogeny-based classification methods have been proposed to obtain informative and standardized results. The first is based on the analysis of the capsid protein VP2 gene, considered as the main determinant of virulence, while the other one considers both VP2 and RNA polymerase VP1, located in different genome segments. The latter approach is therefore better suited to detect reassortment events, which play a significant role in IBDV evolution. This work reports the detection of eight strains in Portuguese broiler farms that diverged from all available IBDV sequences. Subsequent analyses of VP1 and VP2 sequences confirmed that these strains form a new genotype having segment A of a new genogroup and segment B of classical-like genogroup. No recombination events were identified, while several unique amino acid changes were found in key positions within the VP2. This discovery emphasizes the importance of steady and attentive monitoring of IBDV epidemiology. Further research efforts will be devoted to characterizing the novel genotype, by isolating new strains, assessing their pathogenicity and determining the level of protection ensured by commonly administered IBDV vaccines. RESEARCH HIGHLIGHTS Eight IBDV strains with unique VP2 features were detected in Portugal. Based on two distinct classification methods, the strains belong to a new genotype.

Effect of mori folium and eucommiae cortex oral solution on immune function of chicken infected with IBDV

Sangdu oral liquid (MFEC), a kind of traditional Chinese medicine, is used as a new immune enhancer for veterinary drugs or vaccines. In current study, we aimed to evaluate the effect and mechanism of MFEC on improving the immune response of B87 vaccine. Eighty SPF chickens were divided into blank control group (BC group), infectious bursal disease virus (IBDV) group (IBDV group), vaccine group (B87+IBDV group) and vaccine and Sangdu oral liquid combination group (MFEC+B87+IBDV group). In addition to the BC group, all other groups were infected with IBDV to establish immunosuppressive model. Chickens in both B87+IBDV and MFEC+B87+IBDV groups were immunized with B87 vaccine. Chickens in MFEC+B87+IBDV group were given MFEC for 7 days. Compared with B87+IBDV group, there were significantly lower morbidity and mortality, higher level of antibody, less tissue damage, lower expression of Bax and higher expression of Bcl-2 of MFEC+B87+IBDV group (P < 0.05). In MFEC+B87+IBDV group, the expression of IBDV-VP2, IL-6 and IFN-γ mRNA in bursal tissue was significantly lower than that in B87+IBDV group (P < 0.05). MFEC can effectively improve the immune response to B87 vaccine, and resist the invasion and replication of IBDV to avoid the tissue damage and apoptosis caused by IBDV infection.

Stress-induced immunosuppression increases levels of certain circulating miRNAs and affects the immune response to an infectious bursal disease virus vaccine in chickens

Stress-induced immunosuppression can affect the immune effect of vaccine. However, the mechanism of stress-induced immunosuppression affecting immune response to infectious bursal disease virus (IBDV) vaccine in chicken is still unclear. In this study, thirteen IBDV related circulating miRNAs were selected to study their expressions, possible functions and mechanisms in dexamethasone (Dex)-induced immunosuppressed chicken vaccinated with IBDV attenuated vaccine. The experiment aimed to explore the relationship between the expressions of IBDV related circulating miRNAs and stress-induced immunosuppression. The quantitative real-time PCR (qRT-PCR) results showed that Dex-induced immunosuppression could induce the differential expressions of the candidate serum circulating miRNAs, especially on the 2nd, 5th, 7th and 28th day after dexamethasone treatment. Dex-induced immunosuppression could affect the immune response to the IBDV vaccine, which was possibly achieved by partially regulating the differential expressions of the IBDV related circulating miRNAs. Bioinformatics analysis showed that the candidate miRNAs could regulate the immune function mainly through targeting genes (such as CREB1 and MAPK1) in TGF-β and MAPK signaling pathways. This study can provide a preliminary reference for further studying the function and mechanism of circulating miRNAs in immune regulation.

Effects of Lactobacillus salivarius supplementation on the growth performance, liver function, meat quality, immune responses and Salmonella Pullorum infection resistance of broilers challenged with Aflatoxin B1

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins. It has been reported that dietary exposure to AFB1 is related to the low growth performance, immunosuppression, and high susceptibility to infectious diseases of chickens. The aim of the present study was to evaluate the protective effects of Lactobacillus salivarius on broiler chickens challenged with AFB1. First, AFB1 degradation ability of Lactobacillus salivarius was measured by a high-performance liquid chromatography (HPLC) method. Then, the Arbor Acres broiler chickens were randomly assigned to experimental groups. The effects of Lactobacillus salivarius supplementation on the growth performance, liver function, and meat quality were measured, and immune response was also determined after vaccination with attenuated infectious bursal disease virus (IBDV) vaccine of broilers challenged with AFB1. Besides, resistance to Salmonella Pullorum infection along with AFB1 exposure was determined in broilers. The results showed that Lactobacillus salivarius could effectively degrade AFB1. Lactobacillus salivarius supplementation improved growth performance, liver function, and meat quality of broilers challenged with AFB1. In addition, Lactobacillus salivarius supplementation resulted in enhanced specific antibody and IFN-γ production, and lymphocyte proliferation in broilers challenged with AFB1 after IBDV vaccine immunization. Furthermore, Lactobacillus salivarius supplementation enhanced Salmonella Pullorum infection resistance in broilers challenged with AFB1. Our results revealed a tremendous potential of Lactobacillus salivarius as feed additive to degrading AFB1 and increasing broilers production performance in poultry production.