Immune responses to mucosal vaccination by the recombinant A1 and N proteins of infectious bronchitis virus

Development and Immunoprotection of Bacterium-like Particle Vaccine against Infectious Bronchitis in Chickens

Infectious bronchitis (IB) is a major threat to the global poultry industry. Despite the availability of commercial vaccines, the IB epidemic has not been effectively controlled. The exploration of novel IBV vaccines may provide a new way to prevent and control IB. In this study, BLP-S1, a bacterium-like particle displaying the S1 subunit of infectious bronchitis virus (IBV), was constructed using the GEM-PA surface display system. The immunoprotective efficacy results showed that BLP-S1 can effectively induce specific IgG and sIgA immune responses, providing a protection rate of 90% against IBV infection in 14-day-old commercial chickens. These results suggest that BLP-S1 has potential for the development of novel vaccines with good immunogenicity and immunoprotection.

Evaluation of protection and immunity induced by infectious bronchitis vaccines administered by oculonasal, spray or gel routes in commercial broiler chicks

Broiler chicks' responses following combined IBV live attenuated Massachusetts and 793B strains through gel, spray or oculonasal (ON) vaccination routes were cross-compared. Subsequently, the responses following IBV M41 challenge of the unvaccinated and vaccinated groups were also assessed. Post-vaccination humoral and mucosal immune responses, alongside viral load kinetics in swabs and tissues, were determined using commercial ELISA assays, monoclonal antibody-based IgG and IgA ELISA assays and qRT-PCR respectively. After challenged with IBV-M41 strain, humoral and mucosal immune responses, ciliary protection, viral load kinetics, and immune gene mRNA transcriptions between the three vaccination methods were examined and compared. Findings showed that post-vaccinal humoral and mucosal immune responses were similar in all three vaccination methods. Post vaccinal viral load kinetics is influenced by method of administration. The viral load peaked in the ON group within the tissues and the OP/CL swabs in the first and third weeks respectively. Following M41 challenge, ciliary protection and mucosal immune responses were not influenced by vaccination methods as all three methods offered equal ciliary protection. Immune gene mRNA transcriptions varied by vaccination methods. Significant up-regulation of MDA5, TLR3, IL-6, IFN-α and IFN-β genes were recorded for ON method. For both spray and gel methods, significant up-regulation of only MDA5 and IL-6 genes were noted. The spray and gel-based vaccination methods gave equivalent levels of ciliary protection and mucosal immunity to M41 virulent challenge comparable to those provided by the ON vaccination. Analysis of viral load and patterns of immune gene transcription of the vaccinated-challenged groups revealed high similarity between turbinate and choanal cleft tissues compared to HG and trachea. With regards to immune gene mRNA transcription, for all the vaccinated-challenged groups, similar results were found except for IFN-α, IFN-β and TLR3, which were up-regulated only in ON compared to gel and spray vaccination methods.

Protection against avian coronavirus conferred by oral vaccination with live bacteria secreting LTB-fused viral proteins

The devastating impact of infectious bronchitis (IB) triggered by the IB virus (IBV), on poultry farms is generally curbed by livestock vaccination with live attenuated or inactivated vaccines. Yet, this approach is challenged by continuously emerging variants and by time limitations of vaccine preparation techniques. This work describes the design and evaluation of an anti-IBV vaccine comprised of E. coli expressing and secreting viral spike 1 subunit (S1) and nucleocapsid N-terminus and C-terminus polypeptides fused to heat-labile enterotoxin B (LTB) (LS1, LNN, LNC, respectively). Following chicken oral vaccination, anti-IBV IgY levels and cellular-mediated immunity as well as protection against virulent IBV challenge, were evaluated 14 days following the booster dose. Oral vaccination induced IgY levels that exceeded those measured following vaccination with each component separately. Following exposure to inactivated IBV, splenocytes isolated from chicks orally vaccinated with LNN or LNC -expressing bacteria, showed a higher percentage of CD8⁺ cells as compared to splenocytes isolated from chicks vaccinated with wild type or LTB-secreting E. coli and to chicks subcutaneously vaccinated. Significant reduction in viral load and percent of shedders in the vaccinated chicks was evident starting 3 days following challenge with 10^7.5 EID₅₀/ml virulent IBV. Taken together, orally delivered LTB-fused IBV polypeptide-expressing bacteria induced virus-specific IgY antibody production and was associated with significantly shorter viral shedding on challenge with a live IBV. The proposed vaccine design and delivery route promise an effective and rapidly adaptable means of protecting poultry farms from devastating IB outbreaks.

Evaluation of viral load and transcriptome changes in tracheal tissue of two hybrids of commercial broiler chickens infected with avian infectious bronchitis virus: a comparative study

Infectious bronchitis virus (IBV) is one of the major threats to the poultry industry, with significant economic consequences. Despite strict measures, the disease is difficult to control worldwide. Experimental evidence demonstrates that the severity of IBV is affected by the genetic background of the chicken, and the selection of appropriate breeds can increase production efficiency. Therefore, the aim of the present study was to assess the strength of the immune response to IBV in tracheal tissues of Ross 308 and Cobb 500 broiler chickens by evaluating transcriptome changes, focusing on immune responses and the viral load in tracheal tissues two days after IBV infection. We identified 899 and 1350 differentially expressed genes (DEGs) in the Cobb 500 and Ross 308 experimental groups compared to their respective control groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated the involvement of signaling pathways (Toll-like receptor [TLR], NOD-like receptor [NLR], and RIG-I-like receptor [RLR] signaling pathways). Interestingly, the RLR signaling pathway appears to be affected only in the Cobb hybrid. Furthermore, the viral loads in tracheal samples obtained from the Ross challenged group were significantly higher than those of the Cobb challenged group. The results of this study indicated that the host transcriptional response to IBV infection as well as the viral load can differ by hybrid. Furthermore, genes such as TLR-3, ChIFN-α, MDA5, LGP2, IRF-7, NF-κB, and TRIM25 may interfere with IBV proliferation.

Infectious Bronchitis Virus (Gammacoronavirus) in Poultry Farming: Vaccination, Immune Response and Measures for Mitigation

Infectious bronchitis virus (IBV) poses significant financial and biosecurity challenges to the commercial poultry farming industry. IBV is the causative agent of multi-systemic infection in the respiratory, reproductive and renal systems, which is similar to the symptoms of various viral and bacterial diseases reported in chickens. The avian immune system manifests the ability to respond to subsequent exposure with an antigen by stimulating mucosal, humoral and cell-mediated immunity. However, the immune response against IBV presents a dilemma due to the similarities between the different serotypes that infect poultry. Currently, the live attenuated and killed vaccines are applied for the control of IBV infection; however, the continual emergence of IB variants with rapidly evolving genetic variants increases the risk of outbreaks in intensive poultry farms. This review aims to focus on IBV challenge-infection, route and delivery of vaccines and vaccine-induced immune responses to IBV. Various commercial vaccines currently have been developed against IBV protection for accurate evaluation depending on the local situation. This review also highlights and updates the limitations in controlling IBV infection in poultry with issues pertaining to antiviral therapy and good biosecurity practices, which may aid in establishing good biorisk management protocols for its control and which will, in turn, result in a reduction in economic losses attributed to IBV infection.

The COVID-19 Vaccines: Recent Development, Challenges and Prospects

The highly infectious coronavirus disease 2019 (COVID-19) associated with the pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread to become a global pandemic. At present, the world is relying mainly on containment and hygiene-related measures, as well as repurposed drugs to control the outbreak. The development of COVID-19 vaccines is crucial for the world to return to pre-pandemic normalcy, and a collective global effort has been invested into protection against SARS-CoV-2. As of March 2021, thirteen vaccines have been approved for application whilst over 90 vaccine candidates are under clinical trials. This review focuses on the development of COVID-19 vaccines and highlights the efficacy and vaccination reactions of the authorised vaccines. The mechanisms, storage, and dosage specification of vaccine candidates at the advanced stage of development are also critically reviewed together with considerations for potential challenges. Whilst the development of a vaccine is, in general, in its infancy, current progress is promising. However, the world population will have to continue to adapt to the "new normal" and practice social distancing and hygienic measures, at least until effective vaccines are available to the general public.

Factor Influences for Diagnosis and Vaccination of Avian Infectious Bronchitis Virus (Gammacoronavirus) in Chickens

Infectious bronchitis virus (IBV) is a major economic problem in commercial chicken farms with acute multiple-system infection, especially in respiratory and urogenital systems. A live-attenuated and killed vaccine is currently immunized to control IBV infection; however, repeated outbreaks occur in both unvaccinated and vaccinated birds due to the choice of inadequate vaccine candidates and continuous emergence of novel infectious bronchitis (IB) variants and failure of vaccination. However, similar clinical signs were shown in different respiratory diseases that are essential to improving the diagnostic assay to detect IBV infections. Various risk factors involved in the failure of IB vaccination, such as various routes of application of vaccination, the interval between vaccinations, and challenge with various possible immunosuppression of birds are reviewed. The review article also highlights and updates factors affecting the diagnosis of IBV disease in the poultry industry with differential diagnosis to find the nature of infections compared with non-IBV diseases. Therefore, it is essential to monitor the common reasons for failed IBV vaccinations with preventive action, and proper diagnostic facilities for identifying the infective stage, leading to earlier control and reduced economic losses from IBV disease.

SARS-CoV-2 Vaccine Development: Current Status

In the midst of the severe acute respiratory syndrome coronavirus 2 pandemic and its attendant morbidity and mortality, safe and efficacious vaccines are needed that induce protective and long-lived immune responses. More than 120 vaccine candidates worldwide are in various preclinical and phase 1 to 3 clinical trials that include inactivated, live-attenuated, viral-vectored replicating and nonreplicating, protein- and peptide-based, and nucleic acid approaches. Vaccines will be necessary both for individual protection and for the safe development of population-level herd immunity. Public-private partnership collaborative efforts, such as the Accelerating COVID-19 Therapeutic Interventions and Vaccines mechanism, are key to rapidly identifying safe and effective vaccine candidates as quickly and efficiently as possible. In this article, we review the major vaccine approaches being taken and issues that must be resolved in the quest for vaccines to prevent coronavirus disease 2019. For this study, we scanned the PubMed database from 1963 to 2020 for all publications using the following search terms in various combinations: SARS, MERS, COVID-19, SARS-CoV-2, vaccine, clinical trial, coronavirus, pandemic, and vaccine development. We also did a Web search for these same terms. In addition, we examined the World Health Organization, Centers for Disease Control and Prevention, and other public health authority websites. We excluded abstracts and all articles that were not written in English.

Efficacy of Infectious Bronchitis GI-13 (793B) Vaccine Candidate Tested According to the Current European Union Requirements and for Cross-Protection Against Heterologous QX-Like Challenge

Infectious bronchitis (IB) is a highly contagious viral disease of chickens, known to cause severe economic losses. Vaccination against IB virus (IBV) is an important control measure against the disease. The objective of the present study was to test Avishield IB GI-13, the vaccine candidate against IBV, strain V-173/11 (GI-13 genotype), according to European Pharmacopoeia (Ph. Eur.) efficacy requirements. Laboratory study on specific-pathogen-free (SPF) chickens showed 100% protection against challenge 10 days after vaccination of 1-7 day-old chickens by three recommended routes. Duration of immunity was shown to be at least 8 weeks after vaccination. Chickens with maternally derived antibodies (MDA) were 100% protected against challenge 21 and 35 days after vaccination. Testing of the vaccine candidate in field conditions on commercial broiler and layer farms showed 80-90% protection against homologous challenge after spray (broilers and layers) or oral (broilers) vaccine administration. Serum antibodies were monitored during the studies, and although good seroconversion was observed in MDA-positive chickens 34 days after vaccination or later, the data from SPF chickens indicate that non-humoral immunity is important in protection against challenge. Neutralizing antibodies in tears were detected, however, their level could not be fully linked with individual protection scores. A cross-protection study showed that administration of the combination of Avishield IB H120 vaccine and Avishield IB GI-13 vaccine candidate at day 1, confers good protection against heterologous QX-like challenge. Stability of the vaccine after reconstitution in 0.2% skimmed milk solution or distilled water at room temperature was confirmed over the period of 3 h. The vaccine candidate fully complied with Ph. Eur. requirements, with very good protection levels, indicating that it can be administered already at 1 day of age by spray at the hatchery or at 7 days of age by drinking water on the farm.

Pustulan Activates Chicken Bone Marrow-Derived Dendritic Cells In Vitro and Promotes Ex Vivo CD4+ T Cell Recall Response to Infectious Bronchitis Virus

Infectious bronchitis virus (IBV) is a highly contagious avian coronavirus. IBV causes substantial worldwide economic losses in the poultry industry. Vaccination with live-attenuated viral vaccines, therefore, are of critical importance. Live-attenuated viral vaccines, however, exhibit the potential for reversion to virulence and recombination with virulent field strains. Therefore, alternatives such as subunit vaccines are needed together with the identification of suitable adjuvants, as subunit vaccines are less immunogenic than live-attenuated vaccines. Several glycan-based adjuvants directly targeting mammalian C-type lectin receptors were assessed in vitro using chicken bone marrow-derived dendritic cells (BM-DCs). The β-1-6-glucan, pustulan, induced an up-regulation of MHC class II (MHCII) cell surface expression, potentiated a strong proinflammatory cytokine response, and increased endocytosis in a cation-dependent manner. Ex vivo co-culture of peripheral blood monocytes from IBV-immunised chickens, and BM-DCs pulsed with pustulan-adjuvanted recombinant IBV N protein (rN), induced a strong recall response. Pustulan-adjuvanted rN induced a significantly higher CD4⁺ blast percentage compared to either rN, pustulan or media. However, the CD8⁺ and TCRγδ⁺ blast percentage were significantly lower with pustulan-adjuvanted rN compared to pustulan or media. Thus, pustulan enhanced the efficacy of MHCII antigen presentation, but apparently not the cross-presentation on MHCI. In conclusion, we found an immunopotentiating effect of pustulan in vitro using chicken BM-DCs. Thus, future in vivo studies might show pustulan as a promising glycan-based adjuvant for use in the poultry industry to contain the spread of coronaviridiae as well as of other avian viral pathogens.

Production of Recombinant N Protein of Infectious Bronchitis Virus Using the Baculovirus Expression System and Its Assessment as a Diagnostic Antigen

The avian coronavirus-infectious bronchitis virus (AvCoV-IBV) is recognized as an important avian pathogen, and new viral variants are a continuous threat to the poultry industry worldwide. Sensitive diagnostics and efficacious vaccines are necessary to combat IBV infections in chickens. The aim of this study was to produce recombinant N protein of IBV in the baculovirus system to use in ELISA diagnostic tests in order to enable the assessment of the sero-prevalence and risk of IBV infections in chickens in Turkey. For this, the gene encoding the N protein of the Beaudette strain of IBV was expressed using a recombinant baculovirus expression system. The recombinant N protein was purified using Ni-NTA affinity chromatography. An estimated 50-kDa recombinant protein corresponding to the expected molecular weight of IBV N including the 6xHis tag was detected using an anti-His monoclonal antibody. Specific immunoreactivity of the recombinant protein was confirmed by Western blot using antiserum obtained from vaccinated and naturally infected chicken from Turkey as well as using a monoclonal antibody raised against the N protein of the IBV Massachusetts strain. The results obtained with the in-house ELISA had high agreement with a commercial ELISA. Immunoreactivity analysis using antisera in Western blotting and the in-house ELISA suggests that the recombinant IBV N protein could be broadly cross-reactive with antisera produced against different IBV strains. We conclude that the recombinant baculovirus expressed IBV N protein could serve as a useful diagnostic antigen for detection of IBV infections in chickens by ELISA.

Protection against Virulent Infectious Bronchitis Virus Challenge Conferred by a Recombinant Baculovirus Co-Expressing S1 and N Proteins

Avian infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis, which results in considerable economic losses. It is imperative to develop safe and efficient candidate vaccines to control IBV infection. In the current study, recombinant baculoviruses co-expressing the S1 and N proteins and mono-expressing S1 or N proteins of the GX-YL5 strain of IBV were constructed and prepared into subunit vaccines rHBM-S1-N, rHBM-S1 and rHBM-N. The levels of immune protection of these subunit vaccines were evaluated by inoculating specific pathogen-free (SPF) chickens at 14 days of age, giving them a booster with the same dose 14 days later and challenging them with a virulent GX-YL5 strain of IBV 14 days post-booster (dpb). The commercial vaccine strain H120 was used as a control. The IBV-specific antibody levels, as well as the percentages of CD4+ and CD8+ T lymphocytes, were detected within 28 days post-vaccination (dpv). The morbidity, mortality and re-isolation of the virus from the tracheas and kidneys of challenged birds were evaluated at five days post-challenge (dpc). The results showed that the IBV-specific antibody levels and the percentages of CD4+ and CD8+ T lymphocytes were higher in the rHBM-S1-N vaccinated birds compared to birds vaccinated with the rHBM-S1 and rHBM-N vaccines. At 5 dpc, the mortality, morbidity and virus re-isolation rate of the birds vaccinated with the rHBM-S1-N vaccine were slightly higher than those vaccinated with the H120 control vaccine but were lower than those vaccinated with the rHBM-S1 and rHBM-N vaccines. The present study demonstrated that the protection of the recombinant baculovirus co-expressing S1 and N proteins was better than that of recombinant baculoviruses mono-expressing the S1 or N protein. Thus, the recombinant baculovirus co-expressing S1 and N proteins could serve as a potential IBV vaccine and this demonstrates that the bivalent subunit vaccine including the S1 and N proteins might be a strategy for the development of an IBV subunit vaccine.

Heterologous live infectious bronchitis virus vaccination in day-old commercial broiler chicks: clinical signs, ciliary health, immune responses and protection against variant infectious bronchitis viruses

Groups of one-day-old broiler chicks were vaccinated via the oculo-nasal route with different live infectious bronchitis virus (IBV) vaccines: Massachusetts (Mass), 793B, D274 or Arkansas (Ark). Clinical signs and gross lesions were evaluated. Five chicks from each group were humanely killed at intervals and their tracheas collected for ciliary activity assessment and for the detection of CD4+, CD8+ and IgA-bearing B cells by immunohistochemistry (IHC). Blood samples were collected at intervals for the detection of anti-IBV antibodies. At 21 days post-vaccination (dpv), protection conferred by different vaccination regimes against virulent M41, QX and 793B was assessed. All vaccination programmes were able to induce high levels of CD4+, CD8+ and IgA-bearing B cells in the trachea. Significantly higher levels of CD4+ and CD8+ expression were observed in the Mass2 + 793B2-vaccinated group compared to the other groups (subscripts indicate different manufacturers). Protection studies showed that the group of chicks vaccinated with Mass2 + 793B2 produced 92% ciliary protection against QX challenge; compared to 53%, 68% and 73% ciliary protection against the same challenge virus by Mass1 + D274, Mass1 + 793B1 and Mass3 + Ark, respectively. All vaccination programmes produced more than 85% ciliary protection against M41 and 793B challenges. It appears that the variable levels of protection provided by different heterologous live IBV vaccinations are dependent on the levels of local tracheal immunity induced by the respective vaccine combination. The Mass2 + 793B2 group showed the worst clinical signs, higher mortality and severe lesions following vaccination, but had the highest tracheal immune responses and demonstrated the best protection against all three challenge viruses.

Protective efficacy and immune responses by homologous prime-booster immunizations of a novel inactivated Salmonella Gallinarum vaccine candidate

Purpose

Salmonella enterica serovar Gallinarum (SG) ghost vaccine candidate was recently constructed. In this study, we evaluated various prime-boost vaccination strategies using the candidate strain to optimize immunity and protection efficacy against fowl typhoid.

Materials and Methods

The chickens were divided into five groups designated as group A (non-immunized control), group B (orally primed and boosted), group C (primed orally and boosted intramuscularly), group D (primed and boosted intramuscularly), and group E (primed intramuscularly and boosted orally). The chickens were primed with the SG ghost at 7 days of age and were subsequently boosted at the fifth week of age. Post-immunization, the plasma IgG and intestinal secretory IgA (sIgA) levels, and the SG antigen-specific lymphocyte stimulation were monitored at weekly interval and the birds were subsequently challenged with a virulent SG strain at the third week post-second immunization.

Results

Chickens in group D showed an optimized protection with significantly increased plasma IgG, sIgA, and lymphocyte stimulation response compared to all groups. The presence of CD4⁺ and CD8⁺ T cells and monocyte/macrophage (M/M) in the spleen, and splenic expression of cytokines such as interferon γ (IFN-γ) and interleukin 6 (IL-6) in the immunized chickens were investigated. The prime immunization induced significantly higher splenic M/M population and mRNA levels of IFN-γ whereas the booster showed increases of splenic CD4⁺ and CD8⁺ T-cell population and IL-6 cytokine in mRNA levels.

Conclusion

Our results indicate that the prime immunization with the SG ghost vaccine induced Th1 type immune response and the booster elicited both Th1- and Th2-related immune responses.

Factors influencing the outcome of infectious bronchitis vaccination and challenge experiments

The factors influencing the outcome of infectious bronchitis vaccination and challenge experiments regarding the respiratory and renal systems are reviewed. Advantages and disadvantages of the available techniques for measuring protection against an infectious bronchitis virus challenge are discussed, including the definition of protection itself. Suggestions are made regarding some ways in which progress towards standardization of a recognized protocol for performing experimental challenge studies can be made and areas where more work is needed are indicated.

Immune Responses to Virulent and Vaccine Strains of Infectious Bronchitis Viruses in Chickens

Infectious bronchitis (IB) is an acute and highly contagious chicken viral disease, causing severe economic losses to poultry producers worldwide. In the last few decades, infectious bronchitis virus (IBV) has been extensively studied, but knowledge of immune responses to virulent or vaccine strains of IBVs remains limited. This review focuses on fundamental aspects of immune responses against IBV, including the role of pattern recognition receptors (PRRs) in identification of conserved viral structures and the role of different components of innate immunity (e.g., heterophils, macrophages, dendritic cells, acute phase protein, and cytokines). Studies on adaptive immune activation and the role of humoral and cellular immunity in IBV clearance are also reviewed. Multiple interlinking immune responses are essential for protection against virulent IBVs, including passive, innate, adaptive, and effector T cells active at mucosal surfaces. Although the development of approaches for chicken transcriptome and proteome analyses have greatly helped the understanding of the underlying genetic mechanisms for immunity, there are still major knowledge gaps, such as the role of mucosal and cellular responses to IBVs. In view of recent reports of emergent IBV variants in many countries, there is renewed interest in a more complete understanding of poultry immune responses to both virulent and vaccine strains of IBVs. This will be critical for developing new vaccine or vaccination strategies and other intervention programs.

Progress and challenges toward the development of vaccines against avian infectious bronchitis

Avian infectious bronchitis (IB) is a widely distributed poultry disease that has huge economic impact on poultry industry. The continuous emergence of new IBV genotypes and lack of cross protection among different IBV genotypes have been an important challenge. Although live attenuated IB vaccines remarkably induce potent immune response, the potential risk of reversion to virulence, neutralization by the maternal antibodies, and recombination and mutation events are important concern on their usage. On the other hand, inactivated vaccines induce a weaker immune response and may require multiple dosing and/or the use of adjuvants that probably have potential safety risks and increased economic burdens. Consequently, alternative IB vaccines are widely sought. Recent advances in recombinant DNA technology have resulted in experimental IB vaccines that show promise in antibody and T-cells responses, comparable to live attenuated vaccines. Recombinant DNA vaccines have also been enhanced to target multiple serotypes and their efficacy has been improved using delivery vectors, nanoadjuvants, and in ovo vaccination approaches. Although most recombinant IB DNA vaccines are yet to be licensed, it is expected that these types of vaccines may hold sway as future vaccines for inducing a cross protection against multiple IBV serotypes.

Detection of Avian coronavirus infectious bronchitis virus type QX infection in Switzerland

Infectious bronchitis, a disease of chickens caused by Avian coronavirus infectious bronchitis virus (IBV), leads to severe economic losses for the poultry industry worldwide. Various attempts to control the virus based on vaccination strategies are performed. However, due to the emergence of novel genotypes, an effective control of the virus is hindered. In 1996, a novel viral genotype named IBV-QX was reported for the first time in Qingdao, Shandong province, China. The first appearance of an IBV-QX isolate in Europe was reported between 2003 and 2004 in The Netherlands. Subsequently, infections with this genotype were found in several other European countries such as France, Italy, Germany, United Kingdom, Slovenia, and Sweden. The present report describes the use of a new set of degenerate primers that amplify a 636-bp fragment within the S1 gene by reverse transcription polymerase chain reaction to detect the occurrence of IBV-QX infection in Switzerland.