Alloantibodies against MHC class I: a novel mechanism of neonatal pancytopenia linked to vaccination

Bovine Pestivirus Heterogeneity and Its Potential Impact on Vaccination and Diagnosis

Bovine Pestiviruses A and B, formerly known as bovine viral diarrhoea viruses (BVDV)-1 and 2, respectively, are important pathogens of cattle worldwide, responsible for significant economic losses. Bovine viral diarrhoea control programmes are in effect in several high-income countries but less so in low- and middle-income countries where bovine pestiviruses are not considered in disease control programmes. However, bovine pestiviruses are genetically and antigenically diverse, which affects the efficiency of the control programmes. The emergence of atypical ruminant pestiviruses (Pestivirus H or BVDV-3) from various parts of the world and the detection of Pestivirus D (border disease virus) in cattle highlights the challenge that pestiviruses continue to pose to control measures including the development of vaccines with improved cross-protective potential and enhanced diagnostics. This review examines the effect of bovine pestivirus diversity and emergence of atypical pestiviruses in disease control by vaccination and diagnosis.

Spatial distribution and incidence of bovine neonatal pancytopenia in Bavaria, Germany

BACKGROUND

Bovine neonatal pancytopenia (BNP) is a haemorrhagic disease of neonatal calves. BNP was first described in Germany in 2009, later on also in other European countries, and in New Zealand in 2011. The disease is characterised by spontaneous bleeding, pancytopaenia in the bone marrow, and a high case fatality ratio. The causal role of a specific bovine viral diarrhoea virus (BVDV) vaccine (PregSure®BVD, then Pfizer Animal Health, now Zoetis, Berlin, Germany) has been established over the last years, causing the production of alloantibodies in some vaccinated cattle, which in the case of pregnant cattle, are transferred to the newborn calf via the colostrum. However, striking regional differences in the incidence of the disease were observed within Germany and other countries, but as the disease was not notifiable, no representative data on the spatial distribution are available. In this study, we address the spatial distribution and incidence of BNP using the results of two representative surveys amongst cattle practitioners in Bavaria, Germany. The surveys, asking about the occurrence of BNP, were conducted in 2009 and 2010. Answers were analysed spatially by testing for clusters using space-time models. Practitioners were also asked how many cows they serve in their practice and this number was used to estimate the incidence of BNP. Furthermore, in the survey of 2010, practitioners were also asked about usage of vaccine against BVDV.

RESULTS

From the results of the surveys, three clusters were identified in Bavaria. These clusters also coincided with the usage of the specific BVDV vaccine as indicated by the veterinary practices. Furthermore, the representative surveys allow the estimation of the incidence of BNP to be in the order of 4 cases per 10,000 calves at risk.

CONCLUSIONS

The study is the only representative survey conducted on BNP. Despite the fact that BNP is a non-infectious disease, regional clusters were identified.

A Functionally Different Immune Phenotype in Cattle Is Associated With Higher Mastitis Incidence

A novel vaccine against bovine viral diarrhea (BVD) induced pathogenic antibody production in 5-10% of BVD-vaccinated cows. Transfer of these antibodies via colostrum caused Bovine neonatal pancytopenia (BNP) in calves, with a lethality rate of 90%. The exact immunological mechanisms behind the onset of BNP are not fully understood to date. To gain further insight into these mechanisms, we analyzed the immune proteome from alloreactive antibody producers (BNP cows) and non-responders. After in vitro stimulation of peripheral blood derived lymphocytes (PBL), we detected distinctly deviant expression levels of several master regulators of immune responses in BNP cells, pointing to a changed immune phenotype with severe dysregulation of immune response in BNP cows. Interestingly, we also found this response pattern in 22% of non-BVD-vaccinated cows, indicating a genetic predisposition of this immune deviant (ID) phenotype in cattle. We additionally analyzed the functional correlation of the ID phenotype with 10 health parameters and 6 diseases in a retrospective study over 38 months. The significantly increased prevalence of mastitis among ID cows emphasizes the clinical relevance of this deviant immune response and its potential impact on the ability to fight infections.

Bovine Neonatal Pancytopenia-Associated Alloantibodies Recognize Individual Bovine Leukocyte Antigen 1 Alleles

Bovine neonatal pancytopenia (BNP) was a vaccine-induced alloimmune disease observed in young calves and characterized by hemorrhages, pancytopenia, and severe destruction of the hematopoietic tissues. BNP was induced by alloreactive maternal antibodies present in the colostrum of certain cows vaccinated with a highly adjuvanted vaccine against bovine viral diarrhea. Bioprocess impurities, originating from the production cell line of the vaccine, are likely to have induced these alloreactive antibodies. One prominent alloantigen recognized by vaccine-induced alloantibodies is highly polymorphic bovine major histocompatibility complex class I antigen (bovine leukocyte antigen 1-BoLA I). Aim of this study was to define the fine specificity of BNP-associated anti-BoLA I alloantibodies. In total, eight different BoLA I alleles from the production cell line were identified. All genes were cloned and recombinantly expressed in murine cell lines. Using these cells in a flow cytometric assay, the presence of BoLA I specific alloantibodies in BNP dam sera was proven. Three BoLA I variants were identified that accounted for the majority of vaccine-induced BoLA I reactivity. By comparing the sequence of immunogenic to non-immunogenic BoLA I variants probable minimal epitopes on BoLA I were identified. In general, dams of BNP calves displayed high levels of BoLA I reactive alloantibodies, while vaccinated cows delivering healthy calves had significantly lower alloantibody titers. We identified a subgroup of vaccinated cows with healthy calves displaying very high alloantibody titers. Between these cows and BNP dams no principle difference in the BoLA I reactivity pattern was observed. However, with a limited set of dam-calf pairs it could be demonstrated that serum from these cows did not bind to BoLA I expressing leukocytes of their offspring. By contrast, when testing cells from surviving BNP calves with the corresponding dam's serum there was significant binding. We therefore conclude that predominantly highly alloreactive cows are at risk to induce BNP and it depends on the paternally inherited BoLA I whether or not the calf develops BNP.

Herd-level animal management factors associated with the occurrence of bovine neonatal pancytopenia in calves in a multi-country study

Since 2007, mortality associated with a previously unreported haemorrhagic disease has been observed in young calves in several European countries. The syndrome, which has been named ‘bovine neonatal pancytopenia’ (BNP), is characterised by thrombocytopenia, leukocytopenia and a panmyelophthisis. A herd-level case-control study was conducted in four BNP affected countries (Belgium, France, Germany and the Netherlands) to identify herd management risk factors for BNP occurrence. Data were collected using structured face-to-face and telephone interviews of farm managers and their local veterinarians. In total, 363 case farms and 887 control farms were included in a matched multivariable conditional logistic regression analysis. Case-control status was strongly associated with the odds of herd level use of the vaccine PregSure® BVD (PregSure, Pfizer Animal Health) (matched adjusted odds ratio (OR) 107.2; 95% CI: 41.0–280.1). This was also the case for the practices of feeding calves colostrum from the calf’s own dam (OR 2.0; 95% CI: 1.1–3.4) or feeding pooled colostrum (OR 4.1; 95% CI: 1.9–8.8). Given that the study had relatively high statistical power and represented a variety of cattle production and husbandry systems, it can be concluded with some confidence that no other herd level management factors are competent causes for a sufficient cause of BNP occurrence on herd level. It is suggested that genetic characteristics of the dams and BNP calves should be the focus of further investigations aimed at identifying the currently missing component causes that together with PregSure vaccination and colostrum feeding represent a sufficient cause for occurrence of BNP in calves.

Priming Cross-Protective Bovine Viral Diarrhea Virus-Specific Immunity Using Live-Vectored Mosaic Antigens

Bovine viral diarrhea virus (BVDV) plays a key role in bovine respiratory disease complex, which can lead to pneumonia, diarrhea and death of calves. Current vaccines are not very effective due, in part, to immunosuppressive traits and failure to induce broad protection. There are diverse BVDV strains and thus, current vaccines contain representative genotype 1 and 2 viruses (BVDV-1 & 2) to broaden coverage. BVDV modified live virus (MLV) vaccines are superior to killed virus vaccines, but they are susceptible to neutralization and complement-mediated destruction triggered by passively acquired antibodies, thus limiting their efficacy. We generated three novel mosaic polypeptide chimeras, designated N^proE2¹²³; NS²³¹; and NS²³², which incorporate protective determinants that are highly conserved among BVDV-1a, 1b, and BVDV-2 genotypes. In addition, strain-specific protective antigens from disparate BVDV strains were included to broaden coverage. We confirmed that adenovirus constructs expressing these antigens were strongly recognized by monoclonal antibodies, polyclonal sera, and IFN-γ-secreting T cells generated against diverse BVDV strains. In a proof-of-concept efficacy study, the multi-antigen proto-type vaccine induced higher, but not significantly different, IFN-γ spot forming cells and T-cell proliferation compared to a commercial MLV vaccine. In regards to the humoral response, the prototype vaccine induced higher BVDV-1 specific neutralizing antibody titers, whereas the MLV vaccine induced higher BVDV-2 specific neutralizing antibody titers. Following BVDV type 2a (1373) challenge, calves immunized with the proto-type or the MLV vaccine had lower clinical scores compared to naïve controls. These results support the hypothesis that a broadly protective subunit vaccine can be generated using mosaic polypeptides that incorporate rationally selected and validated protective determinants from diverse BVDV strains. Furthermore, regarding biosafety of using a live vector in cattle, we showed that recombinant human adenovirus-5 was cleared within one week following intradermal inoculation.

Bovine Neonatal Pancytopenia - correlation between clinical symptoms, hematological parameters and lifespan

OBJECTIVE

To compare the hematological parameters and clinical symptoms between Bovine Neonatal Pancytopenia (BNP) diseased calves dying before and after 14 days of life.

MATERIAL AND METHODS

Clinical observations included 47 calves from dams which underwent a 3-year vaccination program with the inactivated PregSure^® BVD vaccine. In 25 of these 47 BNP affected calves blood examinations were performed and in 22 dead calves diagnosis was mainly based on post-mortem findings.

RESULTS

Cutaneous bleeding was the predominant clinical manifestation in 32 from 47 calves (68.1%). Seven from 47 calves (14.9%) developed cutaneous bleeding as the only symptom and 17 from 47 calves (36.2%) demonstrated these alterations in combination with hemorrhagic lesions of the oral mucosa. In 66.0% (31/47) of calves petechiae of the oral mucosa were seen and petechiation without any other BNP related symptoms occurred in eight from 47 calves (17.0%). The hematological analysis revealed thrombocytopenia in all 25 cases (n = 23: PLT < 60 x 10⁹/l, n = 2: PLT 139-164 x 10⁹/l). Nineteen from 25 calves (76.0%) developed thrombocytopenia and leukocytopenia (WBC < 3.5 x 10⁹/l). In nine of them a decrease of erythrocyte count (RBC < 4.5 x 10⁹/l), hemoglobin concentration (Hb < 8 g/dl) and packed cell volume (PCV < 24%) was measured. Three BNP affected calves without clinical symptoms were identified by hematological examination. The average life time of BNP affected calves was 14.7 ± 6.2 days. Clinical findings, especially multifocal cutaneous hemorrhages were more frequently recognized in calves living longer than 14 days.

CONCLUSION AND CLINICAL RELEVANCE

At the time of falling ill with BNP, older calves displayed more numerous symptoms, especially bleeding in the skin. Thrombocytopenia and erythropenia occur as well as a decreased hemoglobin concentration and a low PCV. The time between outbreak of symptoms and death of calves which fell ill later, did not differ from the survival time of BNP calves, which displayed symptoms at a younger age. A decrease of thrombocytes was the cardinal laboratory finding.

The risks of using allogeneic cell lines for vaccine production: the example of Bovine Neonatal Pancytopenia

INTRODUCTION

Bovine neonatal pancytopenia (BNP) is a hemorrhagic disease that emerged in calves across Europe in 2007. Its occurrence is attributed to immunization of the calf's mother with a vaccine produced using an allogeneic cell line. Vaccine-induced alloantibodies specific for major-histocompatibility class I antigens are transferred from the mother to the calf via colostrum, leading to profound depletion of peripheral blood and bone marrow cells that is often fatal. Areas covered: Pubmed and Web of Science were used to search for literature relevant to BNP and the use of allogeneic vaccine cell lines. Following a review of the pathology and pathogenesis of this novel condition, we discuss potential risks associated with the use of allogeneic vaccine cell lines. Expert commentary: Although BNP is associated with a specific vaccine, it highlights safety concerns common to all vaccines produced using allogeneic cell lines. Measures to prevent similar vaccine-induced alloimmune-mediated adverse events in the future are discussed.

Existence of bovine neonatal pancytopenia before the year 2005? Retrospective evaluation of 215 cases of haemorrhagic diathesis in cattle

Haemorrhagic diathesis (HD) in cattle is a relatively rare syndrome that can have many different causes. With the occurrence of bovine neonatal pancytopenia (BNP) in 2007, the number of cases of HD in cattle has increased. This led to an enhanced interest in diseases presenting with bleeding disorders. The possible causes of HD in cattle, the clinical findings, and the course of various diseases are described and evaluated. Furthermore, we determined whether cases of BNP occurred before the introduction of the vaccine Pregsure BVD since its widespread use was associated with the syndrome. Records of 215 cases of HD in cattle that had been referred to the Clinic for Ruminants with Ambulatory and Herd Health Services at the Centre for Clinical Veterinary Medicine, Ludwig Maximilian University, Munich, between 1982 and 2014 were evaluated. The two most commonly diagnosed diseases were BNP (n = 95) and septicaemia (n = 35), with fatality rates of 82% and 66%, respectively. In 27 (13%) cases, no clear cause for the HD could be designated. Statistically significant differences were found with regard to the course of the various disorders and the clinical findings. A receiver operating characteristic analysis of thrombocyte counts of affected animals at the time of arrival at the clinic did not provide any predictive information on disease outcome. Two cases of HD occurred before the introduction of Pregsure BVD (1989, 1991). In both cases, clinical, haematological, and pathological findings were identical to BNP. The cause of HD in these two cases could not be determined retrospectively.

A novel RNAseq-assisted method for MHC class I genotyping in a non-model species applied to a lethal vaccination-induced alloimmune disease

Background

MHC class I genotyping is essential for a wide range of biomedical, immunological and biodiversity applications. Whereas in human a comprehensive MHC class I allele catalogue is available, respective data in non-model species is scarce in spite of decades of research.

Results

Taking advantage of the new high-throughput RNA sequencing technology (RNAseq), we developed a novel RNAseq-assisted method (RAMHCIT) for MHC class I typing at nucleotide level. RAMHCIT is performed on white blood cells, which highly express MHC class I molecules enabling reliable discovery of new alleles and discrimination of closely related alleles due to the high coverage of alleles with reads. RAMHCIT is more comprehensive than previous methods, because no targeted PCR pre-amplification of MHC loci is necessary, which avoids preselection of alleles as usually encountered, when amplification with MHC class I primers is performed prior to sequencing. In addition to allele identification, RAMHCIT also enables quantification of MHC class I expression at allele level, which was remarkably consistent across individuals.

Conclusions

Successful application of RAMHCIT is demonstrated on a data set from cattle with different phenotype regarding a lethal, vaccination-induced alloimmune disease (bovine neonatal pancytopenia), for which MHC class I alleles had been postulated as causal agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2688-0) contains supplementary material, which is available to authorized users.

Pregnancy boosts vaccine-induced Bovine Neonatal Pancytopenia-associated alloantibodies

Although maternal vaccination is generally considered to be safe, the occurrence of Bovine Neonatal Pancytopenia (BNP) in cattle shows that maternal vaccination may pose a risk to the offspring. Pregsure BVD-induced maternal alloantibodies cause BNP in newborn calves. The occurrence of BNP years after last Pregsure BVD vaccination indicates that alloantibody levels may remain high in dams. Since pregnancy induces alloantibodies we hypothesized that pregnancy boosts the vaccine-induced alloantibody response. Alloantibody levels in Pregsure BVD-vaccinated dams increased from conception towards the end of gestation and declined after parturition. In parallel, BVDV-antibody levels remained constant, indicating that there is specific boosting of alloantibodies. Since the rise in alloantibodies coincides with pregnancy and other alloantigen sources were excluded, we concluded that fetal alloantigens expressed during pregnancy boost the alloimmune response in the dam. These results help explain why BNP cases occur even years after Pregsure BVD has been taken off the market.

Pathogenicity of Bovine Neonatal Pancytopenia-associated vaccine-induced alloantibodies correlates with Major Histocompatibility Complex class I expression

Bovine Neonatal Pancytopenia (BNP), a fatal bleeding syndrome of neonatal calves, is caused by maternal alloantibodies absorbed from colostrum and is characterized by lymphocytopenia, thrombocytopenia and bone marrow hypoplasia. An inactivated viral vaccine is the likely source of alloantigens inducing BNP-associated alloantibodies in the dam. In this study the specificity of BNP alloantibodies was assessed and was linked to the pathology of BNP. We demonstrated that Major Histocompatibility Complex class I (MHC I) and Very Late Antigen-3, an integrin α3/β1 heterodimer, were the major targets of BNP alloantibodies. However, alloantibody binding to various bovine cell types correlated with MHC I expression, rather than integrin β1 or α3 expression. Likewise, alloantibody-dependent complement-mediated cell lysis correlated strongly with MHC I expression. Examination of several tissues of third trimester bovine foetuses revealed that cells, shown to be affected in calves with BNP, were characterized by high MHC class I expression and high levels of alloantibody binding. We conclude that in spite of the heterogeneous specificity of BNP associated maternal alloantibodies, MHC I-specific antibodies mediate the pathogenicity of BNP in the calf and that cells with high MHC I expression were preferentially affected in BNP.

Haematopoietic depletion in vaccine-induced neonatal pancytopenia depends on both the titre and specificity of alloantibody and levels of MHC I expression

Bovine Neonatal Pancytopenia (BNP) is a disease of calves characterised by haematopoietic depletion, mediated by ingestion of alloantibodies in colostrum. It has been linked epidemiologically to vaccination of the dams of affected calves with a particular vaccine (Pregsure) containing a novel adjuvant. Evidence suggests that BNP-alloantibodies are directed against MHC I molecules, induced by contaminant bovine cellular material from Madin-Darby Bovine Kidney (MDBK) cells used in the vaccine's production. We aimed to investigate the specificity of BNP-alloantibody for bovine MHC I alleles, particularly those expressed by MDBK cells, and whether depletion of particular cell types is due to differential MHC I expression levels. A complement-mediated cytotoxicity assay was used to assess functional serum alloantibody titres in BNP-dams, Pregsure-vaccinated dams with healthy calves, cows vaccinated with an alternative product and unvaccinated controls. Alloantibody specificity was investigated using transfected mouse lines expressing the individual MHC I alleles identified from MDBK cells and MHC I-defined bovine leukocyte lines. All BNP-dams and 50% of Pregsure-vaccinated cows were shown to have MDBK-MHC I specific alloantibodies, which cross-reacted to varying degrees with other MHC I genotypes. MHC I expression levels on different blood cell types, assessed by flow cytometry, were found to correlate with levels of alloantibody-mediated damage in vitro and in vivo. Alloantibody-killed bone marrow cells were shown to express higher levels of MHC I than undamaged cells. The results provide evidence that MHC I-specific alloantibodies play a dominant role in the pathogenesis of BNP. Haematopoietic depletion was shown to be dependent on the titre and specificity of alloantibody produced by individual cows and the density of surface MHC I expression by different cell types. Collectively, the results support the hypothesis that MHC I molecules originating from MDBK cells used in vaccine production, coupled with a powerful adjuvant, are responsible for the generation of pathogenic alloantibodies.

Bovine Neonatal Pancytopenia is a heritable trait of the dam rather than the calf and correlates with the magnitude of vaccine induced maternal alloantibodies not the MHC haplotype

Bovine Neonatal Pancytopenia (BNP), a bleeding syndrome of neonatal calves, is caused by alloantibodies absorbed from the colostrum of particular cows. A commercial BVD vaccine is the likely source of alloantigens eliciting BNP associated alloantibodies. We hypothesized that the rare occurrence of BNP in calves born to vaccinated dams could be associated with genetic differences within dams and calves. We found that the development of BNP within calves was a heritable trait for dams, not for calves and had a high heritability of 19%. To elucidate which genes play a role in the development of BNP we sequenced candidate genes and characterized BNP alloantibodies. Alloantigens present in the vaccine have to be presented to the dam’s immune system via MHC class II, however sequencing of DRB3 showed no differences in MHC class II haplotype between BNP and non-BNP dams. MHC class I, a highly polymorphic alloantigen, is an important target of BNP alloantibodies. Using a novel sequence based MHC class I typing method, we found no association of BNP with MHC class I haplotype distribution in dams or calves. Alloantibodies were detected in both vaccinated BNP and non-BNP dams and we found no differences in alloantibody characteristics between these groups, but alloantibody levels were significantly higher in BNP dams. We concluded that the development of BNP in calves is a heritable trait of the dam rather than the calf and genetic differences between BNP and non-BNP dams are likely due to genes controlling the quantitative alloantibody response following vaccination.

Colostrum from cows immunized with a vaccine associated with bovine neonatal pancytopenia contains allo-antibodies that cross-react with human MHC-I molecules

In 2006, a new haemorrhagic syndrome affecting newborn calves, Bovine Neonatal Pancytopenia (BNP), was reported in southern Germany. It is characterized by severe bleeding, destruction of the red bone marrow, and a high case fatality rate. The syndrome is caused by alloreactive, maternal antibodies that are ingested by the calf with colostrum and result from a dam vaccination with one particular vaccine against Bovine-Viral-Diarrhoea-Virus. Because bovine colostrum is increasingly gaining interest as a dietary supplement for human consumption, the current study was initiated to elucidate whether BNP alloantibodies from BNP dams (i.e. animals that gave birth to a BNP-affected calf) cross-react with human cells, which could pose a health hazard for human consumers of colostral products. The present study clearly demonstrates that BNP alloantibodies cross-react with human lymphocytes in vitro. In agreement with previous reports on BNP, the cross-reactive antibodies are specific for MHC-I molecules, and sensitize opsonised human cells for in vitro complement lysis. Cross-reactive antibodies are present in serum and colostrum of individual BNP dams. They can be traced in commercial colostrum powder manufactured from cows immunized with the vaccine associated with BNP, but are absent from commercial powder manufactured from colostrum excluding such vaccinated cows. In humans alloreactive, MHC-I specific antibodies are generally not believed to cause severe symptoms. However, to minimize any theoretical risk for human consumers, manufacturers of bovine colostrum for human consumption should consider using only colostrum from animals that have not been exposed to the vaccine associated with BNP.

Evidence of a high incidence of subclinically affected calves in a herd of cattle with fatal cases of Bovine Neonatal Pancytopenia (BNP)

Background

Bovine Neonatal Pancytopenia (BNP) is a disease of calves characterised by bone marrow trilineage hypoplasia, mediated by ingestion of alloantibodies in colostrum. Suspected subclinical forms of BNP have been reported, suggesting that observed clinical cases may not represent the full extent of the disease. However to date there are no objective data available on the incidence of subclinical disease or its temporal distribution. This study aimed to 1) ascertain whether subclinical BNP occurs and, if so, to determine the incidence on an affected farm and 2) determine whether there is evidence of temporal clustering of BNP cases on this farm. To achieve these aims, haematological screening of calves born on the farm during one calving season was carried out, utilising blood samples collected at defined ages. These data were then analysed in comparison to data from both known BNP-free control animals and histopathologically confirmed BNP cases. An ordinal logistic regression model was used to create a composite haematology score to predict the probabilities of calves being normal, based on their haematology measurements at 10–14 days old.

Results

This study revealed that 15% (21 of 139) of the clinically normal calves on this farm had profoundly abnormal haematology (<5% chance of being normal) and could be defined as affected by subclinical BNP. Together with clinical BNP cases, this gave the study farm a BNP incidence of 18%. Calves with BNP were found to be distributed throughout the calving period, with no clustering, and no significant differences in the date of birth of cases or subclinical cases were found compared to the rest of the calves. This study did not find any evidence of increased mortality or increased time from birth to sale in subclinical BNP calves but, as the study only involved a single farm and adverse effects may be determined by other inter-current diseases it remains possible that subclinical BNP has a detrimental impact on the health and productivity of calves under certain circumstances.

Conclusions

Subclinical BNP was found to occur at a high incidence in a herd of cattle with fatal cases of BNP.

Characterization of an experimental vaccine for bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) and human respiratory syncytial virus (HRSV) are major causes of respiratory disease in calves and children, respectively, and are priorities for vaccine development. We previously demonstrated that an experimental vaccine, BRSV-immunostimulating complex (ISCOM), is effective in calves with maternal antibodies. The present study focuses on the antigenic characterization of this vaccine for the design of new-generation subunit vaccines. The results of our study confirmed the presence of membrane glycoprotein (G), fusion glycoprotein (F), and nucleoprotein (N) proteins in the ISCOMs, and this knowledge was extended by the identification of matrix (M), M2-1, phosphoprotein (P), small hydrophobic protein (SH) and of cellular membrane proteins, such as the integrins αVβ1, αVβ3, and α3β1. The quantity of the major protein F was 4- to 5-fold greater than that of N (∼77 μg versus ∼17 μg/calf dose), whereas G, M, M2-1, P, and SH were likely present in smaller amounts. The polymerase (L), M2-2, nonstructural 1 (NS1), and NS2 proteins were not detected, suggesting that they are not essential for protection. Sera from the BRSV-ISCOM-immunized calves contained high titers of IgG antibody specific for F, G, N, and SH. Antibody responses against M and P were not detected; however, this does not exclude their role in protective T-cell responses. The absence of immunopathological effects of the cellular proteins, such as integrins, needs to be further confirmed, and their possible contribution to adjuvant functions requires elucidation. This work suggests that a combination of several surface and internal proteins should be included in subunit RSV vaccines and identifies absent proteins as potential candidates for differentiating infected from vaccinated animals.

Bovine neonatal pancytopenia (BNP): novel insights into the incidence, vaccination-associated epidemiological factors and a potential genetic predisposition for clinical and subclinical cases

Bovine neonatal pancytopenia (BNP) is a haemorrhagic disease of newborn calves elicited by colostrum from specific cows. Two studies have indicated that BNP-inducing colostrum might be associated with alloantibodies directed against MHC class I in response to vaccination with a distinct inactivated viral vaccine. However, the proportion of alloantibody-producing individuals by far exceeds the proportion of clinical BNP cases in the vaccinated population. This raises the question about the incidence of subclinical, unrecognised cases and also suggests further factors involved in BNP pathogenesis, e.g., genetic predisposition. Our results on neonatal calves from a closely monitored resource population confirmed the hypothesis of a genetic predisposition for clinical BNP and suggest that the predisposition is also involved in subclinical BNP-cases. No indication was obtained for a higher frequency of subclinical BNP-cases compared with clinical cases. Neither time point nor frequency of vaccination was a relevant factor for BNP in our resource population.

Calf-level factors associated with bovine neonatal pancytopenia--a multi-country case-control study

Bovine neonatal pancytopenia (BNP), a high fatality condition causing haemorrhages in calves aged less than 4 weeks, was first reported in 2007 in Germany and subsequently observed at low incidence in other European countries and New Zealand. A multi-country matched case-control study was conducted in 2011 to identify calf-level risk factors for BNP. 405 BNP cases were recruited from 330 farms in Belgium, France, Germany and the Netherlands by laboratory confirmation of farmer-reported cases. Up to four calves of similar age from the same farm were selected as controls (1154 calves). Risk factor data were collected by questionnaire. Multivariable modelling using conditional logistic regression indicated that PregSure®BVD (PregSure, Pfizer Animal Health) vaccination of the dam was strongly associated with BNP cases (adjusted matched Odds Ratio - amOR 17.8 first lactation dams; 95% confidence interval – ci 2.4, 134.4; p = 0.005), and second or more lactation PregSure-vaccinated dams were more likely to have a case than first lactation vaccinated dams (amOR 2.2 second lactation; ci 1.1, 4.3; p = 0.024; amOR 5.3 third or more lactation; ci 2.9, 9.8; p = <0.001). Feeding colostrum from other cows was strongly associated with BNP if the dam was not PregSure-vaccinated (amOR 30.5; ci 2.1, 440.5; p = 0.012), but the effect was less if the dam was PregSure-vaccinated (amOR 2.1; ci 1.1, 4.0; p = 0.024). Feeding exclusively dam’s milk was a higher risk than other types of milk (amOR 3.4; ci 1.6, 7.5; p = 0.002). The population attributable fractions were 0.84 (ci 0.68, 0.92) for PregSure vaccination, 0.13 (ci 0.06, 0.19) for feeding other cows’ colostrum, and 0.15 (ci 0.08, 0.22) for feeding dam’s milk. No other calf-level factors were identified, suggesting that there are other important factors that are outside the scope of this study, such as genetics, which explain why BNP develops in some PregSure-colostrum-exposed calves but not in others.

Monitoring the immune response to vaccination with an inactivated vaccine associated to bovine neonatal pancytopenia by deep sequencing transcriptome analysis in cattle

Bovine neonatal pancytopenia (BNP) is a new fatal, alloimmune/alloantibody mediated disease of new-born calves induced by ingestion of colostrum from cows, which had been vaccinated with a specific vaccine against the Bovine Virus Diarrhoea Virus (BVDV). The hypothesis of pathogenic MHC class I molecules in the vaccine had been put up, but no formal proof of specific causal MHC class I alleles has been provided yet. However, the unique features of the vaccine obviously result in extremely high specific antibody titres in the vaccinated animals, but apparently also in further molecules inducing BNP. Thus, a comprehensive picture of the immune response to the vaccine is essential. Applying the novel approach of next generation RNA sequencing (RNAseq), our study provides a new holistic, comprehensive analysis of the blood transcriptome regulation after vaccination with the specific BVDV vaccine. Our RNAseq approach identified a novel cytokine-like gene in the bovine genome that is highly upregulated after vaccination. This gene has never been described before in any other species and might be specific to ruminant immune response. Furthermore, our data revealed a very coordinated immune response to double-stranded (ds) RNA or a dsRNA analogue after vaccination with the inactivated single-stranded (ss) RNA vaccine. This would suggest either a substantial contamination of the vaccine with dsRNA from host cells after virus culture or a dsRNA analogue applied to the vaccine. The first option would highlight the potential risks associated with virus culture on homologous cells during vaccine production; the latter option would emphasise the potential risks associated with immune stimulating adjuvants used in vaccine production.

Bovine neonatal pancytopenia--comparative proteomic characterization of two BVD vaccines and the producer cell surface proteome (MDBK)

Background

Bovine neonatal pancytopenia (BNP) is a disease syndrome in newborn calves of up to four weeks of age, first observed in southern Germany in 2006. By now, cases have been reported in several countries around the globe. Many affected calves die within days due to multiple haemorrhages, thrombocytopenia, leukocytopenia and bone marrow depletion. A certain vaccine directed against Bovine Virus Diarrhoea Virus (BVDV) was recently shown to be associated with BNP pathogenesis. Immunized cows develop alloantibodies that are transferred to newborn calves via colostrum intake. In order to further elucidate BNP pathogenesis, the purpose of this study was to characterize and compare the protein composition of the associated vaccine to another vaccine directed against BVDV not related to BNP and the cell surface proteome of MDBK (Madin-Darby Bovine Kidney) cells, the cell line used for production of the associated vaccine.

Results

By SDS-PAGE and mass spectrometry, we were able to detect several coagulation-related and immune modulatory proteins, as well as cellular and serum derived molecules being shared between the associated vaccine and MDBK cells. Furthermore, the number of proteins identified in the BNP related vaccine was almost as high as the number of surface proteins detected on MDBK cells and exceeded the amount of proteins identified in the non-BNP related vaccine over 3.5 fold. The great amount of shared cellular and serum derived proteins confirm that the BNP associated vaccine contained many molecules originating from MDBK cells and vaccine production.

Conclusions

The respective vaccine was not purified enough to prevent the development of alloantibodies. To narrow down possible candidate proteins, those most likely to represent a trigger for BNP pathogenesis are presented in this study, giving a fundament for further analysis in future research.

Reproduction of bovine neonatal pancytopenia (BNP) by feeding pooled colostrum reveals variable alloantibody damage to different haematopoietic lineages

Bovine neonatal pancytopenia (BNP) is a recently described haemorrhagic disease of calves characterised by thrombocytopenia, leucopenia and bone marrow depletion. Feeding colostrum from cows that have previously produced a BNP affected calf has been shown to induce the disease in some calves, leading to the hypothesis that alloantibodies in colostrum from dams of affected calves mediate destruction of blood and bone marrow cells in the recipient calves. The aims of the current experimental study were first to confirm the role of colostrum-derived antibody in mediating the disease and second to investigate the haematopoietic cell lineages and maturation stages depleted by the causative antibodies. Clinical, haematological and pathological changes were examined in 5 calves given a standardised pool of colostrum from known BNP dams, and 5 control calves given an equivalent pool of colostrum from non-BNP dams. All calves fed challenge colostrum showed progressive depletion of bone marrow haematopoietic cells and haematological changes consistent with the development of BNP. Administration of a standardised dose of the same colostrum pool to each calf resulted in a consistent response within the groups, allowing detailed interpretation of the cellular changes not previously described. Analyses of blood and serial bone marrow changes revealed evidence of differential effects on different blood cell lineages. Peripheral blood cell depletion was confined to leucocytes and platelets, while bone marrow damage occurred to the primitive precursors and lineage committed cells of the thrombocyte, lymphocyte and monocyte lineages, but only to the more primitive precursors in the neutrophil, erythrocyte and eosinophil lineages. Such differences between lineages may reflect cell type-dependent differences in levels of expression or conformational nature of the target antigens.

Demonstration of early functional compromise of bone marrow derived hematopoietic progenitor cells during bovine neonatal pancytopenia through in vitro culture of bone marrow biopsies

Background

Bovine neonatal pancytopenia (BNP) is a syndrome characterised by thrombocytopenia associated with marked bone marrow destruction in calves, widely reported since 2007 in several European countries and since 2011 in New Zealand. The disease is epidemiologically associated with the use of an inactivated bovine virus diarrhoea (BVD) vaccine and is currently considered to be caused by absorption of colostral antibody produced by some vaccinated cows (“BNP dams”). Alloantibodies capable of binding to the leukocyte surface have been detected in BNP dams and antibodies recognising bovine MHC class I and β-2-microglobulin have been detected in vaccinated cattle. In this study, calves were challenged with pooled colostrum collected from BNP dams or from non-BNP dams and their bone marrow hematopoietic progenitor cells (HPC) cultured in vitro from sternal biopsies taken at 24 hours and 6 days post-challenge.

Results

Clonogenic assay demonstrated that CFU-GEMM (colony forming unit-granulocyte/erythroid/macrophage/megakaryocyte; pluripotential progenitor cell) colony development was compromised from HPCs harvested as early as 24 hour post-challenge. By 6 days post challenge, HPCs harvested from challenged calves failed to develop CFU-E (erythroid) colonies and the development of both CFU-GEMM and CFU-GM (granulocyte/macrophage) was markedly reduced.

Conclusion

This study suggests that the bone marrow pathology and clinical signs associated with BNP are related to an insult which compromises the pluripotential progenitor cell within the first 24 hours of life but that this does not initially include all cell types.

Effect of the vaccination scheme on PregSure® BVD induced alloreactivity and the incidence of Bovine Neonatal Pancytopenia

Bovine Neonatal Pancytopenia (BNP) is a new neonate-maternal incompatibility phenomenon caused by vaccine-induced, maternal alloantibodies. The syndrome affects newborn calves at the approximate age of ten days and is characterized by spontaneous bleeding, severe anemia with an almost complete destruction of the red bone marrow. During the past two years the causal role of bioprocess impurities in PregSure(®)BVD, a strongly adjuvanted, inactivated vaccine against Bovine Virus Diarrhoea (BVD), in the induction of BNP causing alloantibodies has clearly been established. Despite intensive research efforts that have elucidated the basic principles of the BNP immunopathology still a number of questions remain open. In the current manuscript we address the puzzling observation that BNP incidences vary widely between different regions: as an example we compare the BNP incidences in the German Federal States of Bavaria and Lower Saxony. In Bavaria the BNP-incidence reaches 100 cases per 100,000 doses PregSure(®)BVD, while in Lower Saxony the incidence is as low as 6 cases per 100,000 doses. In Bavaria the vaccine has always been used according to the instructions for use. By contrast, in Lower Saxony BVD-immunization was performed according to a two-step vaccination protocol including a first immunization with an inactivated BVD-vaccine followed by booster immunizations with a live-attenuated BVD-vaccine. As a consequence, those cattle that received PregSure(®)BVD received in general more than two doses in Bavaria, while in Lower Saxony cows received at maximum one dose. By experimental immunization we can show that the two-step regimen including PregSure(®)BVD as a priming vaccine results in significantly lower alloantibody titers as compared to repetitive immunizations with the inactivated vaccine. The lower alloantibody titer after two-step vaccination explains the lower BNP-incidence in Lower Saxony and - generally speaking - indicates that variations in the vaccination regimen have a great influence on the induction of adverse reactions through bioprocess impurities.

Immunophenotyping and characterization of BNP colostra revealed pathogenic alloantibodies of IgG1 subclass with specifity to platelets, granulocytes and monocytes of all maturation stages

Bovine neonatal pancytopenia (BNP) is mainly characterized by multiple haemorrhages, thrombocytopenia and leukocytopenia as a result of bone marrow depletion. BNP can be induced in healthy calves through application of colostrum from BNP donors, proofing that BNP is mediated to maternal alloantibodies. Alloantibody binding to bovine blood cells is present in sera and colostra of BNP donors and is probably initialized by vaccination with a certain BVD vaccine. To understand etiology and pathomechanisms of BNP, we closely characterized disease inducing antibodies regarding immunoglobulin subclass and binding specificities to peripheral blood derived leukocytes and platelets. By exact phenotyping the targeted blood cell subsets, including platelets for the first time, we investigated that BNP alloantibodies are exclusively of IgG1 subclass. Interestingly, IgG1 of BNP colostra bound to 70% leukocytes and 100% platelets irrespective of different bovine breeds and cellular maturity of all specimens tested. Furthermore, staining pattern on platelets as well as leukocyte subsets by BNP-IgG1 alloantibody exposed 100% reactivity to platelets, granulocytes and monocytes. Interestingly, the main part of T-helper cells was not bound by colostral alloantibodies. Our results point to a crucial role of IgG1 antibodies in BNP and to a target antigen that is expressed by all cells of myeloid lineage, but only partially by the lymphoid lineage.