Diversity among bovine pestiviruses

Analysis for codon usage bias in membrane anchor of nonstructural protein 5A from BVDV

The nonstructural protein 5A (NS5A) of the bovine viral diarrhea virus (BVDV) is a monotopic membrane protein. This protein can anchor to the cell membrane by an in-plane amphipathic ⍺-helix, which participates in the viral replication complex. In this study, the effects of synonymous codon usage pattern of NS5A and the overall transfer RNA (tRNA) abundance in cells on the formation of the in-plane membrane anchor of NS5A were analyzed, based on NS5A coding sequences of different BVDV genotypes. BVDV NS5A coding sequences represent the most potential for BVDV genotyping. Moreover, the nucleotide usage of BVDV NS5A dominates the genotype-specific pattern of synonymous codon usage. There is an obvious relationship between synonymous codon usage bias and the spatial conformation of the in-plane membrane anchor. Furthermore, the overall tRNA abundance profiling displays that codon positions with a high level of tRNA abundance are more than ones with a low level of tRNA abundance in the in-plane membrane anchor, implying that high translation speed probably acts on the spatial conformation of in-plane membrane anchor of BVDV NS5A. These results give a new opinion on the effect of codon usage bias in the formation of the in-plane membrane anchor of BVDV NS5A.

Long-term acute infections during a bovine viral diarrhea virus (BVDV) outbreak in dairy farm from Galicia (NW Spain)

An observational study describes an outbreak of bovine viral diarrhea virus (BVDV) in a dairy herd in Spain. The herd was subjected to a voluntary control program. In a sampling carried out in June 2020, bulk tank milk antibody levels increased compared to the previous sampling. Additionally, serum samples from 4 young heifers also tested positive for antibodies. Since the results were consistent with a recent infection, we proceeded to detect possible persistently infected (PI) animals using antigen ELISA (on serum/ear-notch samples), following the program guidelines. From this moment on, 42 animals tested positive for BVDV antigen, of which 17 were under typical acute infection (AI), 13 were deemed as PI, and eight died early on the farm before having information to determine their status. The remaining 4 showed intriguing test results consistent with a long-term AI since they tested BVDV positive in at least two antigen tests more than 3 weeks apart. Thus, one animal was positive until 80 days of age in serum, and others even for longer periods in ear-notch samples, until they finally tested negative for BVDV. Based on these results, longer follow-up may be necessary in BVDV positive animals to accurately confirm persistent infection.

Temporal and geographic dynamics of bovine viral diarrhea virus in American countries

Bovine viral diarrhea virus (BVDV) is a worldwide distributed pathogen of livestock classified into three species, BVDV-1 (Pestivirus A), BVDV-2 (Pestivirus B), and HoBi-like pestivirus (HoBiPeV; Pestivirus H). Despite being considered endemic in several regions of the Americas, the spatiotemporal distribution of BVDV is scarcely known. This study aimed to reconstruct the population dynamics of BVDV in American countries. The analyses performed with the partial 5´UTR gene showed that BVDV-1 and -2 would have started their diversification in the 1670s and 1790s in the United States, whereas HoBiPeV probably emerged in the 1980s in Brazil. No evident geographic clustering was observed in the Bayesian trees, which may indicate that multiple introductions events would have occurred following the first introduction. This study provides new insights into BVDV dynamics, although further analyses including sequences from other American countries and continents will help to expand the knowledge of BVDV evolution and transmission.

Temporal analysis of bovine pestivirus diversity in Brazil

In this study, phylogenetic and evolutionary analyses of cattle pestiviruses (BVDV-1, 2 and HoBiPeV) originating in Brazil were used to investigate the temporal diversification of subgenotypes in the country. Inferred dated phylogeny and time of the most recent common ancestor (tMRCA) demonstrated that some BVDV subgenotypes (1a, 1b, 1d, 1e, and 2b) and HoBi-like sequences clustered according to the region in which they were collected and that the diversification of subgenotypes appears to have occurred around the introduction of first Bos taurus and then Bos indicus, followed by expansion to form the adapted Brazilian breeds. The present results help to elucidate the temporal facts that led to diversification of ruminant pestiviruses in cattle in Brazil.

Congenital Cataracts and Microphakia with Retinal Dysplasia and Optic Nerve Hypoplasia in a Calf

Case Description. A two-month-old, female, Aberdeen-Angus calf was presented for congenital cataracts and blindness in both eyes (OU). The dam had a reported history of visual defects (not specified) and had produced other affected calves (per owner history). Ophthalmic examination revealed mature bilateral cataracts, attenuation of the iridic granules, persistent pupillary membranes, and dyscoric pupils. Additionally, the calf had a poor body condition, prognathism, dome-shaped head, excessive nasal drainage, limb contracture, and fever. Histopathology of both eyes revealed lenticular degeneration (congenital cataracts), retinal dysplasia, and optic nerve hypoplasia. BVDV IHC detected antigen within only the left eye (OS), consisting of intrahistiocytic and endothelial immunoreactivity within the ciliary body, iris, and choroid. No BVDV immunoreactivity could be detected in the right eye (OD). This case highlights the unique ocular changes present in in utero BVDV infection of cattle with a different immunohistochemical staining profile than previously described.

Clinical Analysis for Long-Term Sporadic Bovine Viral Diarrhea Transmitted by Calves with an Acute Infection of Bovine Viral Diarrhea Virus 2

Bovine viral diarrhea virus (BVDV) is a viral pathogen associated with serious problems in the cattle industry. Cattle persistently infected (PI) with BVDV are mild or asymptomatic; however, they become a source of BVDV transmission to other cattle. Hence, it is important to rapidly identify and remove the PI animals from cattle herds. Whereas cattle acutely infected (AI) with BVDV have various symptoms, yet they generally recover within 3 weeks. However, there is a paucity of information concerning clinical characteristics of AI cattle. Further accumulation of information would be required to accurately diagnose AI cattle with BVDV. Here, we attempted to obtain valuable information via various analyses using a case report of BVD outbreak that occurred for approximately four months in Iwate Prefecture in 2017. Using eight calves and multiple tests (real-time RT-PCR, virus isolation, enzyme-linked immunosorbent assay, and virus neutralization assay) over 6 weeks, we diagnosed the continuous BVD outbreak as an acute infection and not a persistent one. Additionally, we revealed that the sporadic case was caused by low pathogenic BVDV2 via BVDV genotyping and phylogenetic analysis. The data suggest that BVDV2 AI animals might also be a source of transmission to susceptible calves; hence, it might persist for a long period owing to multiple AI animals. These findings provide useful information to diagnose AI and PI cattle with BVDV in the field.

Border disease in cattle

Within the family Flaviviridae, viruses within the genus Pestivirus, such as Border disease virus (BDV) of sheep, can cause great economic losses in farm animals. Originally, the taxonomic classification of pestiviruses was based on the host species they were isolated from, but today, it is known that many pestiviruses exhibit a broad species tropism. This review provides an overview of BDV infection in cattle. The clinical, hematological and pathological-anatomical findings in bovines that were transiently or persistently infected with BDV largely resemble those in cattle infected with the closely related pestivirus bovine viral diarrhoea virus (BVDV). Accordingly, the diagnosis of BDV infection can be challenging, as it must be differentiated from various pestiviruses in cattle. The latter is very relevant in countries with control programs to eradicate BVDV in Bovidae, as in most circumstances, pestivirus infections in sheep, which act as reservoir for BDV, are not included in the eradication scheme. Interspecies transmission of BDV between sheep and cattle occurs regularly, but BDV in cattle appears to be of minor general importance. Nevertheless, BDV outbreaks at farm or local level can be very costly.

Prevalence and genome characteristics of atypical porcine pestivirus in southwest China

Atypical porcine pestivirus (APPV) causes congenital tremor (CT) in piglets and has a wide geographical distribution. In this study, we evaluated APPV prevalence using 165 piglet sera from southwest China. Viral RNA was detectable by qRT-PCR in 43.6 % (17/39, 95 % CI 27.8-60.4 %) of piglets with CT, while viral RNA was not detected in the sera of any healthy piglets. The seven complete APPV genomes were obtained from distinct farms and were 11 269-11 459 nucleotides in length. The genomes of the seven strains shared 82.8-98 % identity with the APPV reference strains. Phylogenetic analysis of the complete genomes as well as E2 and Nrpo sequences revealed that the seven APPVs clustered into two groups: four strains belonged to genogroups A and D and three strains belonged to a novel APPV genotype, tentatively called genogroup E. This study provides important insights into the epidemiological features and genetic diversity of APPV.

Characterization of thymus-associated lymphoid depletion in bovine calves acutely or persistently infected with bovine viral diarrhea virus 1, bovine viral diarrhea virus 2 or HoBi-like pestivirus

Naïve pregnant cattle exposed to pestiviruses between 40-125 days of gestation can give birth to persistently infected (PI) calves. Clinical presentation and survivability, in PI cattle, is highly variable even with the same pestivirus strain whereas the clinical presentation in acute infections is more uniform with severity of symptoms being primarily a function of virulence of the infecting virus. The aim of this study was to compare thymic depletion, as measured by comparing the area of the thymic cortex to the medulla (corticomedullary ratio), in acute and persistent infections of the same pestivirus isolate. The same general trends were observed with each pestivirus isolate. Thymic depletion was observed in both acutely and persistently infected calves. The average thymic depletion observed in acutely infected calves was greater than that in age matched PI calves. PI calves, regardless of infecting virus, revealed a greater variability in amount of depletion compared to acutely infected calves. A trend was observed between survivability and depletion of the thymus, with PI calves surviving less than 5 weeks having lower corticomedullary ratios and greater depletion. This is the first study to compare PI and acutely infected calves with the same isolates as well as to evaluate PI calves based on survivability. Further, this study identified a quantifiable phenotype associated with potential survivability.

Failed detection of Bovine viral diarrhea virus 2 subgenotype a (BVDV-2a) by direct fluorescent antibody test on tissue samples due to reduced reactivity of field isolates to raw anti-BVDV antibody

Bovine viral diarrhea virus 1 (BVDV-1) is associated with mild or subclinical infections, whereas BVDV-2 is frequently implicated in outbreaks of severe thrombocytopenia and acute fatal disease. In the present study, the carcass of a beef breed cow and tissue samples of a beef calf were received for laboratory diagnosis. Both animals exhibited severe clinical signs compatible with thrombocytopenia or hemorrhagic syndrome. Direct fluorescent antibody test (DFAT) failed to detect BVDV antigen in the tissue specimens of both cases. However, immunohistochemistry (IHC) revealed the presence of BVDV antigen in oral and esophageal mucosa and Peyer patches of the beef breed cow. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR) detected BVDV-2 in selected tissues of both animals. Subsequently, BVDV was isolated from both cases and subjected to genetic and serologic characterizations. Mutations in the 5'-untranslated genomic region (5'-UTR) primer and probe binding sites and the E2 gene were associated with reduced efficiency of an established real-time RT-PCR assay and amino acid alterations in the E2 glycoprotein, respectively. Both viral isolates were classified by real-time RT-PCR and phylogenetic analysis as BVDV-2 subgenotype a. Unlike BVDV reference strains Singer and 125c, the isolates cross-reacted with anti-BVDV-1 and anti-BVDV-2 reference sera, indicating antigenic variations in field isolates. The isolates also showed reduced reactivity to porcine anti-BVDV antiserum (the raw serum used to produce BVDV DFA conjugate). In summary, data from the present investigation indicated that genetic and antigenic variations affected the performance of detection assays, especially DFAT, highlighting the need for regular evaluation and modification of BVDV tests.

Genetic diversity of bovine viral diarrhea viruses from the Galicia region of Spain

This study examined the frequency and diversity of bovine viral diarrhoea viruses (BVDVs) infecting cattle in Galicia (northwestern Spain). A total of 86 BVDV strains were typed in samples of serum from 79 persistently infected animals and 3 viraemic animals and of abomasal fluid from 4 fetuses. Samples came from 73 farms participating in a voluntary BVDV control programme. Typing was based on a 288-bp sequence from the 5′ untranslated region amplified using primers 324 and 326. Of the 86 strains, 85 (98.8 per cent) belonged to species BVDV-1 and 1 (1.2 per cent) belonged to BVDV-2; 73 strains (84.9 per cent) were typed as BVDV-1b, 2 as BVDV-1e and 6 as BVDV-1d. One strain each was typed as belonging to 1a, 1h, 1k and 1l. The sole BVDV-2 strain was classified as 2a. These results identify BVDV-1b as the predominant species, and they indicate the presence of viral types not previously described anywhere in Spain. This is also the first report of BVDV-2 in Galicia and only the second report of BVDV-2 in Spain.

Genetic Variability of Bovine Viral Diarrhea Virus and Evidence for a Possible Genetic Bottleneck during Vertical Transmission in Persistently Infected Cattle

Bovine viral diarrhea virus (BVDV), a Pestivirus in the family Flaviviridae, is an economically important pathogen of cattle worldwide. The primary propagators of the virus are immunotolerant persistently infected (PI) cattle, which shed large quantities of virus throughout life. Despite the absence of an acquired immunity against BVDV in these PI cattle there are strong indications of viral variability that are of clinical and epidemiological importance. In this study the variability of E2 and NS5B sequences in multiple body compartments of PI cattle were characterized using clonal sequencing. Phylogenetic analyses revealed that BVDV exists as a quasispecies within PI cattle. Viral variants were clustered by tissue compartment significantly more often than expected by chance alone with the central nervous system appearing to be a particularly important viral reservoir. We also found strong indications for a genetic bottleneck during vertical transmission from PI animals to their offspring. These quasispecies analyses within PI cattle exemplify the role of the PI host in viral propagation and highlight the complex dynamics of BVDV pathogenesis, transmission and evolution.

The Molecular Biology of Pestiviruses

Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.

First detection of bovine viral diarrhoea virus type 2 in cattle in Spain

BACKGROUND

Bovine viral diarrhoea virus (BVDV) is a member of the genus Pestivirus that belongs to the family Flaviviridae. BVDV is found worldwide in cattle population and causes significant economic losses to the dairy and beef industries. Two distinct genotypes of BVDV exist: BVDV type 1 (BVDV-1) and BVDV type 2 (BVDV-2).

OBJECTIVE

The aim of the present study was to investigate retrospectively the presence of BVDV-2 in Spain.

RESULTS

With this objective, 47 blood samples that had tested positive in an ELISA for BVDV antigen were selected. Samples had been submitted by practitioners to the Diagnostic Service of NEIKER. The 18 herds of origin were all located in the northern half of Spain. BVDV positive samples were genotyped by reverse transcription-PCR. BVDV-1 was detected with the highest frequency (46/47), in contrast to BVDV-2 (2/47). In one blood sample, both pestivirus genotypes, BVDV-1 and BVDV-2, were detected. Sequencing of a viral genomic region, 5' untranslated region, confirmed the identity of the BVDV-2 isolate.

CONCLUSIONS

So far as the authors know, this is the first reported presence of BVDV-2 in cattle herds in Spain. This finding may have important implications for the epidemiology, diagnosis and control of BVDV infection in the country.

Metadata beyond the sequence enables the phylodynamic inference of bovine viral diarrhea virus type 1a isolates from Western Canada

Bovine viral diarrhea virus (BVDV) has been recognized as an important pathogen of livestock in Canada. The high mutation rate of this virus leads to a great degree of diversity between isolates resulting in the ability to infer precise evolutionary relationships. Many studies have attempted to elucidate the regional and global evolution of BVDV, but so far few have applied Bayesian methods to this end. We aimed to describe the molecular epidemiology and phylodynamics of BVDV 1a isolates in Western Canada using 5'UTR and E1-E2 sequence data, collection dates and locations. Sequences were obtained from isolates submitted to a diagnostic laboratory in Saskatoon, Canada. Path sampling and stepping stone model testing were employed to identify the model that best fit the data. We found that these Western Canadian isolates share a most recent common ancestor dated near 1909. Furthermore, the E1-E2 region shows a median substitution rate about ten times greater than the 5'UTR. It was also noted that caution should be exercised when inferring phylogenetic relationships using the 5'UTR alone, as it becomes difficult to resolve relationships within major clades. Phylogeographic and population size fluctuation estimates require more thorough sampling than was performed here to be reliable. We have found that there are significant gains to be made by utilizing a Bayesian analysis and by incorporating additional types of data beyond the sequence. These include the estimation of most common recent ancestor dates and the precise inference of transmission routes. Future work will expand upon these findings by more thoroughly sampling BVDV isolates spatially and temporally and further refining the Bayesian model employed here.

First finding of genetic and antigenic diversity in 1b-BVDV isolates from Argentina

Infection with Bovine Viral Diarrhea Viruses (BVDV) in cattle results in a wide range of clinical manifestations, ranging from mild respiratory disease to fetal death and mucosal disease, depending on the virulence of the virus and the immune and reproductive status of the host. In this study 30 Argentinean BVDV isolates were characterized by phylogenetic analysis. The isolates were genotyped based on comparison of the 5' untranslated region (5' UTR) and the E2 gene. In both phylogenetic trees, 76% of the viruses were assigned to BVDV 1b, whereas BVDV 1a, 2a and 2b were also found. Eight of the BVDV 1b isolates were further characterized by cross-neutralization tests using guinea pig antisera and sera from bovines vaccinated with two different commercial vaccines. The results demonstrated the presence of a marked antigenic diversity among Argentinean BVDV isolates and suggest the need to incorporate BVDV 1b isolates in diagnostic strategies.

Pestiviruses

Pestiviruses cause economically important diseases among domestic ruminants and pigs, but they may also infect a wide spectrum of wild species of even-toed ungulates (Artiodactyla). Bovine viral diarrhea virus (BVDV) and Border disease virus of sheep infect their hosts either transiently or persistently. Cellular and humoral immunotolerance to the infecting strain is a unique feature of persistent infection (PI) by ruminant pestiviruses. Persistence, caused by transplacental infection early in fetal development, depends on virally encoded interferon antagonists that inactivate the host's innate immune response to the virus without globally interfering with its function against other viruses. At epidemiological equilibrium, approximately 1-2% of animals are PI. Successful BVDV control programs show that removal of PI animals results in viral extinction in the host population. The nucleotide sequences of ruminant pestiviruses change little during persistent infection. Nevertheless, they display large heterogeneity, pointing to a long history of virus-host coevolution in which avirulent strains are more successful.

Expression of type I interferon-induced antiviral state and pro-apoptosis markers during experimental infection with low or high virulence bovine viral diarrhea virus in beef calves

The objective of this study was to compare the mRNA expression of host genes involved in type-I interferon-induced antiviral state (IFN-α, IFN-β, Mx-1, PKR, OAS-1 and ISG-15), and apoptosis (caspase-3, -8, and -9), after experimental infection of beef calves with low or high virulence noncytopathic (ncp) bovine viral diarrhea virus (BVDV) strains. Thirty BVDV-naïve, clinically normal calves were randomly assigned to three groups. Calves were intranasally inoculated with low (LV; n=10, strain SD-1) or high (HV; n=10, strain 1373) virulence ncp BVDV or BVDV-free cell culture medium (Control, n=10). Quantitative RT-PCR was used to determine the target gene expression in tracheo-bronchial lymph nodes and spleen 5 days after infection. Interferon-α and -β mRNA levels were up-regulated in tracheo-bronchial lymph nodes (P<0.05) in the HV group, but not in the LV group, compared with the control group. There was an up-regulation of type I interferon-induced genes in spleen and tracheo-bronchial lymph nodes of HV and LV groups, compared with the control group (P<0.01). mRNA levels of OAS-1 and ISG-15 were significantly higher in LV than HV calves (P<0.05). A significant up-regulation of caspase-8 and -9 was observed in tracheo-bronchial lymph nodes in the LV group (P=0.01), but not in the HV group. In conclusion, experimental infection with either high or low virulence BVDV strains induced a significant expression of the type I interferon-induced genes in beef calves. There was a differential expression of some interferon-induced genes (OAS-1 and ISG-15) and pro-apoptosis markers based on BVDV virulence and genotype.

Bovine Viral Diarrhea Virus Cyclically Impairs Long Bone Trabecular Modeling in Experimental Persistently Infected Fetuses

Persistent infection (PI) with bovine viral diarrhea virus (BVDV) has been associated with osteopetrosis and other long bone lesions, most commonly characterized as transverse zones of unmodeled metaphyseal trabeculae in fetuses and calves. This study was undertaken to characterize the morphogenesis of fetal long bone lesions. Forty-six BVDV-naïve pregnant Hereford heifers of approximately 18 months of age were inoculated with noncytopathic BVDV type 2 containing media or media alone on day 75 of gestation to produce PI and control fetuses, respectively, which were collected via cesarean section on days 82, 89, 97, 192, and 245 of gestation. Radiographic and histomorphometric abnormalities were first detected on day 192, at which age PI fetal long bone metaphyses contained focal densities (4 of 7 fetuses) and multiple alternating transverse radiodense bands (3 of 7 fetuses). Day 245 fetuses were similarly affected. Histomorphometric analysis of proximal tibial metaphyses from day 192 fetuses revealed transverse zones with increased calcified cartilage core (Cg.V/BV, %) and trabecular bone (BV/TV, %) volumes in regions corresponding to radiodense bands ( P < .05). Numbers of tartrate resistant acid phosphatase positive osteoclasts (N.Oc/BS, #/mm2) and bone perimeter occupied (Oc.S/BS, %) were both decreased ( P < .05). Mineralizing surface (MS/BS, %), a measure of tissue level bone formation activity, was reduced in PI fetuses ( P < .05). It is concluded that PI with BVDV induces cyclic abnormal trabecular modeling, which is secondary to reduced numbers of osteoclasts. The factors responsible for these temporal changes are unknown but may be related to the time required for osteoclast differentiation from precursor cells.

Inactivation at various temperatures of bovine viral diarrhea virus in beef derived from persistently infected cattle

Bovine viral diarrhea virus (BVDV) is a pestivirus that is enzootic in most cattle populations throughout the world. This virus is present throughout the body of persistently infected (PI) cattle. Previous research has not assessed the cooking temperature at which BVDV in meat from PI cattle can be inactivated. Therefore, muscle tissue from 6 PI cattle was harvested, refrigerated, frozen, and heated to various internal temperatures. The concentration of virus present was determined by virus isolation. Average cell culture infective doses (50% endpoint; CCID(50)) of BVDV per gram of frozen, uncooked meat from PI cattle were 10(5.85) CCID(50)/g of whole cuts and 10(6.02) CCID(50)/g of ground meat. The virus in whole and ground meat was consistently inactivated when cooked to temperatures greater than or equal to 75°C. A second objective of this research was to thoroughly reassess if Vero cells were permissive to BVDV infection in our laboratory to provide further indication of whether primates, including humans, might be susceptible to BVDV. Vero cells were not permissive to infection with any of 43 different strains of BVDV that readily replicated in Madin Darby bovine kidney cells. In conclusion, this bovine pathogen, which is not considered to be a human pathogen, can be inactivated by cooking ground or whole cuts of meat to 75°C or higher. Care should be taken to ensure that susceptible hosts such as pigs are not fed improperly cooked meat, meat by-products, or waste food originating from PI cattle.

Cytopathic bovine viral diarrhea viruses (BVDV): emerging pestiviruses doomed to extinction

Bovine viral diarrhea virus (BVDV), a Flaviviridae pestivirus, is arguably one of the most widespread cattle pathogens worldwide. Each of its two genotypes has two biotypes, non-cytopathic (ncp) and cytopathic (cp). Only the ncp biotype of BVDV may establish persistent infection in the fetus when infecting a dam early in gestation, a time point which predates maturity of the adaptive immune system. Such fetuses may develop and be born healthy but remain infected for life. Due to this early initiation of fetal infection and to the expression of interferon antagonistic proteins, persistently infected (PI) animals remain immunotolerant to the infecting viral strain. Although only accounting for some 1% of all animals in regions where BVDV is endemic, PI animals ensure the viral persistence in the host population. These animals may, however, develop the fatal mucosal disease, which is characterized by widespread lesions in the gastrointestinal tract. Cp BVD virus, in addition to the persisting ncp biotype, can be isolated from such animals. The cp viruses are characterized by unrestrained genome replication, and their emergence from the persisting ncp ones is due to mutations that are unique in each virus analyzed. They include recombinations with host cell mRNA, gene translocations and duplications, and point mutations. Cytopathic BVD viruses fail to establish chains of infection and are unable to cause persistent infection. Hence, these viruses illustrate a case of "viral emergence to extinction" - irrelevant for BVDV evolution, but fatal for the PI host.

Analysis of Bovine Viral Diarrhea Viruses-infected monocytes: identification of cytopathic and non-cytopathic biotype differences

Background

Bovine Viral Diarrhea Virus (BVDV) infection is widespread in cattle worldwide, causing important economic losses. Pathogenesis of the disease caused by BVDV is complex, as each BVDV strain has two biotypes: non-cytopathic (ncp) and cytopathic (cp). BVDV can cause a persistent latent infection and immune suppression if animals are infected with an ncp biotype during early gestation, followed by a subsequent infection of the cp biotype. The molecular mechanisms that underscore the complex disease etiology leading to immune suppression in cattle caused by BVDV are not well understood.

Results

Using proteomics, we evaluated the effect of cp and ncp BVDV infection of bovine monocytes to determine their role in viral immune suppression and uncontrolled inflammation. Proteins were isolated by differential detergent fractionation and identified by 2D-LC ESI MS/MS. We identified 137 and 228 significantly altered bovine proteins due to ncp and cp BVDV infection, respectively. Functional analysis of these proteins using the Gene Ontology (GO) showed multiple under- and over- represented GO functions in molecular function, biological process and cellular component between the two BVDV biotypes. Analysis of the top immunological pathways affected by BVDV infection revealed that pathways representing macropinocytosis signalling, virus entry via endocytic pathway, integrin signalling and primary immunodeficiency signalling were identified only in ncp BVDV-infected monocytes. In contrast, pathways like actin cytoskeleton signalling, RhoA signalling, clathrin-mediated endocytosis signalling and interferon signalling were identified only in cp BDVD-infected cells. Of the six common pathways involved in cp and ncp BVDV infection, acute phase response signalling was the most significant for both BVDV biotypes. Although, most shared altered host proteins between both BVDV biotypes showed the same type of change, integrin alpha 2b (ITGA2B) and integrin beta 3 (ITGB3) were down- regulated by ncp BVDV and up- regulated by cp BVDV infection.

Conclusions

This study shows that, as we expected, there are significant functional differences in the host proteins that respond to cp or ncp BVDV infection. The combined use of GO and systems biology network modelling facilitated a better understanding of host-pathogen interactions.

Electroporation enhances immune responses and protection induced by a bovine viral diarrhea virus DNA vaccine in newborn calves with maternal antibodies

Bovine viral diarrhea virus (BVDV) is one of the major pathogens in cattle. In this study, newborn calves with maternal antibodies were vaccinated with a BVDV DNA vaccine, either by conventional intramuscular (IM) injection or with the TriGrid™ Delivery System for IM delivery (TDS-IM). The calves vaccinated with the TDS-IM developed more rapidly and effectively BVDV-specific humoral and cell-mediated immune responses in the presence of maternal antibodies. Overall, the immune responses induced by delivery with the TDS-IM remained stronger than those elicited by conventional IM injection of the BVDV DNA vaccine. Accordingly, electroporation-mediated delivery of the BVDV DNA vaccine resulted in close to complete protection from clinical signs of disease, while conventional IM administration did not fully prevent morbidity and mortality following challenge with BVDV-2. These results demonstrate the TDS-IM to be effective as a delivery system for a BVDV DNA vaccine in newborn calves in the presence of maternal antibodies, which supports the potential of electroporation as a delivery method for prophylactic DNA vaccines.

Molecular characterization of Bovine virus diarrhea viruses species 2 (BVDV-2) from cattle in Turkey

Five BVDV species 2 (BVDV-2) isolates were detected from cattle in Turkey. Phylogenetic analysis was performed based on the 5' untranslated regions (UTRs) and E2 coding gene regions, respectively. The isolates were closely related to BVDV-2a strains from North America and Canada used as references. This is the first report of the detection of BVDV-2 in naturally infected Turkish cattle. It is important to consider BVDV-2 for planning future BVDV control and vaccination programs in Turkey.

Atypical 'HoBi'-like pestiviruses--recent findings and implications thereof

In 2004, an atypical pestivirus named D32/00_'HoBi', isolated from foetal calf serum (FCS) originating from Brazil, was described (Schirrmeier et al., 2004). A few years later, a closely related virus (Th/04_KhonKaen) was detected in serum from a calf in Thailand, indicating that this group of atypical pestiviruses already is spread in cattle populations in various regions of the world. At the Friedrich-Loeffler-Institute, Insel Riems, Germany, FCS batches are regularly tested for pestivirus contamination, in general with positive PCR results, and in some cases the contaminants have been typed as 'HoBi'-like. At the National Veterinary Institute (SVA) in Uppsala, Sweden, a recent event with contaminated FCS ruined much of the ongoing cell culture work. From the FCS and the contaminated cells we were able to amplify and sequence nucleic acid from three different pestivirus strains, including BVDV-1, -2 and 'HoBi'-like; this in a commercial FCS that had been tested free from pestivirus by the manufacturer. In this short communication we review the current status of atypical 'HoBi'-like pestiviruses, describe recent findings and discuss the implications thereof.

Acute non-cytopathic bovine viral diarrhea virus infection induces pronounced type I interferon response in pregnant cows and fetuses

Bovine viral diarrhea virus (BVDV) infection occurs in the cattle population worldwide. Non-cytopathic (ncp) BVDV strains cause transient infection (TI) or persistent infection (PI) depending on the host's immune status. Immunocompetent adult animals and fetuses in late gestation resolve the infection. Fetal infection in early gestation results in PI with chronic viremia and life-long viral shedding, ensuring virus perpetuation in the population. Eighteen pregnant heifers, divided into three groups, were intranasally inoculated with ncp BVDV2 virus early (day 75) and late (day 175) in gestation, or kept BVDV-naïve. Fetuses were retrieved on day 190. Antiviral activity in blood of dams and fetuses, maternal expression of interferon (IFN) stimulated gene 15kDa (ISG15), virological and serological status of heifers and fetuses, and fetal growth were studied. A pronounced antiviral activity in blood of heifers and TI fetuses during acute BVDV infection was accompanied by drastic up-regulation of ISG15 mRNA in maternal blood. Only one PI fetus expressed low IFN response 115 days post inoculation despite high BVDV antigen and RNA levels. PI fetuses presented with growth retardation. Infection of pregnant heifers with ncp BVDV2 early in gestation adversely affects fetal development and antiviral responses, despite protective immune responses in the dam.

Natural infection of cattle with an atypical `HoBi'-like pestivirus – Implications for BVD control and for the safety of biological products

During a study on Bovine Viral Diarrhoea (BVD) epidemiology in Thailand, a pestivirus was detected in serum from a calf. Comparative nucleotide sequence analysis showed that this virus was closely related to a recently described atypical pestivirus (D32/00_'HoBi') that was first isolated from a batch of foetal calf serum collected in Brazil. The results from virus neutralisation tests performed on sera collected from cattle in the herd of the infected calf, showed that these cattle had markedly higher antibody titres against the atypical pestivirus 'HoBi' than against Bovine Viral Diarrhoea Virus types 1 and 2, or Border Disease Virus. The results also supported, consequently, the results from the molecular analysis, and demonstrated that a 'HoBi'-like pestivirus had been introduced to, and was now circulating in the herd. This study is the first to report a natural infection in cattle with a virus related to this atypical pestivirus, and it suggests that this group of pestiviruses may already be spread in cattle populations. The findings have implications for BVD control and for the biosafety of vaccines and other biological products produced with foetal calf serum. Consequently, these atypical pestiviruses should be included in serological assays, and any diagnostic assay aimed at detection of pestiviruses in biological products or animals should be tested for its ability to detect them.

RT-PCR em pools de soros sangüíneos para o diagnóstico da infecção aguda e de animais persistentemente infectados pelo vírus da diarréia viral bovina

Utilizou-se a técnica da RT-PCR para a detecção da região 5' UTR do genoma do vírus da diarréia viral bovina (BVDV) em pools de soros sangüíneos provenientes de um rebanho, constituído por 226 animais, que apresentava distúrbios da reprodução. A partir das amostras individuais de soro e de acordo com a categoria dos animais e o número de animais por categoria foram formados 10 pools (A a J) de soros. A primeira avaliação revelou a amplificação de um produto com 290pb nas reações referentes aos grupos D (35 vacas) e H (25 bezerros lactentes) que, após o desmembramento em amostras individuais, resultou na identificação de 11 vacas lactantes e 12 bezerros em amamentação positivos. Para a identificação de animais persistentemente infectados (PI) entre os 23 positivos na primeira avaliação, realizou-se a segunda colheita de soros sangüíneos, três meses após. A RT-PCR das amostras individuais de soro revelou resultado positivo em cinco bezerros. Em dois, foi possível isolar o BVDV em cultivo de células MDBK. A especificidade das reações da RT-PCR foi confirmada pelo seqüenciamento dos produtos amplificados a partir do soro de uma vaca com infecção aguda, de um bezerro PI e das duas amostras do BVDV isoladas em cultivo celular. A utilização da RT-PCR em pools de soros sangüíneos demonstrou ser uma estratégia rápida de diagnóstico etiológico e de baixo custo tanto para a detecção de infecção aguda quanto de animais PI.

Bovine viral diarrhoea virus (BVDV) diversity and vaccination. A review

BVDV is associated with a range of economically important clinical diseases including reproductive disorders and acute fatal haemorrhagic disease in cattle industry. Vaccination is still the most important control strategy for controlling BVDV infections in many countries of the world. The existence of great genetic and antigenic diversity of BVDV isolates is very important concern for BVDV vaccine development and protective efficacy of current vaccines. In this review, the protective efficacies of the selected examples of BVDV vaccines with regard to BVDV diversity and the novel marker vaccine development studies are discussed.

Genetic characterization of Brazilian bovine viral diarrhea virus isolates by partial nucleotide sequencing of the 5'-UTR region

Nineteen isolates of bovine viral diarrhea virus (BVDV) from Brazil were genetically characterized through partial nucleotide sequencing and analysis of the 5'UTR region. The isolates were grouped as BVDV-1 (11/19), BVDV-2 (6/19) or "atypical" pestivirus (2/19). Among the BVDV-1, eight isolates were classified as subgenotype BVDV-1a, whereas most (4 out of 6) BVDV-2 belonged to subgenotype 2b. Two isolates from aborted fetuses were not classified into any genetic group, being considered atypical BVDVs. Genetic diversity among Brazilian BVDV isolates may be responsible for vaccination and diag-nostic failure and therefore may influence the control strategies for BVDV infection in the country.

Analysis of variation of bovine viral diarrhoea virus E2 sequence following transplacental infection of cattle

The genetic and antigenic diversity observed in field isolates of bovine viral diarrhoea virus (BVDV) is thought to occur during acute infection because of the genetic stability observed in BVDV throughout the lifetime of persistently infected (PI) cattle. In this study, 15 cows in early pregnancy were inoculated with identical challenge doses obtained from a single infectious inoculum of the virologically cloned isolate Pe515nc. In order to examine the diversity that may develop in utero in the PI foetus, the variable E2 sequence of the virus isolated directly from the serum of each PI calf was compared. A high degree of sequence similarity was demonstrated, with 0-4 nucleotide differences out of 608 bases compared. Thus, the virus showed relatively few genomic changes in any of the PI calves, although we observed that the in utero environment did provide some opportunity for genetic variation to become established.

Homologous recombination in bovine pestiviruses. Phylogenetic and statistic evidence

Bovine pestiviruses (Bovine Viral Diarrea Virus 1 (BVDV 1) and Bovine Viral Diarrea Virus 2 (BVDV 2)) belong to the genus Pestivirus (Flaviviridae), which is composed of positive stranded RNA viruses causing significant economic losses world-wide. We used phylogenetic and bootstrap analyses to systematically scan alignments of previously sequenced genomes in order to explore further the evolutionary mechanisms responsible for variation in the virus. Previously published data suggested that homologous crossover might be one of the mechanisms responsible for the genomic rearrangements observed in cytopathic (cp) strains of bovine pestiviruses. Nevertheless, homologous recombination involves not just homologous crossovers, but also replacement of a homologous region of the acceptor RNA. Furthermore, cytopathic strains represent dead paths in evolution, since they are isolated exclusively from the fatal cases of mucosal disease. Herein, we report evidence of homologous inter-genotype recombination in the genome of a non-cytopathic (ncp) strain of Bovine Viral Diarrea Virus 1, the type species of the genus Pestivirus. We also show that intra-genotype homologous recombination might be a common phenomenon in both species of Pestivirus. This evidence demonstrates that homologous recombination contribute to the diversification of bovine pestiviruses in nature. Implications for virus evolution, taxonomy and phylogenetics are discussed.

Innate immune responses of calves during transient infection with a noncytopathic strain of bovine viral diarrhea virus

In this study, six immunocompetent calves were experimentally infected with a noncytopathic strain of bovine viral diarrhea virus (BVDV), and the effects of the viral infection on parameters of the innate immune response of the host were analyzed. Clinical and virological data were compared with the temporal activation of the alpha/beta interferon-regulated Mx gene in white blood cells (WBC) and skin as well as the upregulation of the acute-phase serum proteins haptoglobin (Hp) and serum amyloid A (SAA). The viral strain used did provoke transient health impairment, namely, fever and leukopenia that were associated with viremia, viral shedding with nasal secretions, and antiviral seroconversion. Complete recovery was observed within 3 weeks. Elevated levels of SAA and Hp were apparent from days 4 to 13 and 8 to 11, respectively. In WBC, the levels of Mx mRNA and Mx protein were elevated from days 2 to 15. In the context of this study with BVDV, the level of Mx protein expression in WBC provided the most telling diagnostic window to monitor the host's ongoing innate immune response.

Distribution of Viral Antigen and Tissue Lesions in Persistent and Acute Infection with the Homologous Strain of Noncytopathic Bovine Viral Diarrhea Virus

Viral distribution and lesions were compared between calves born with persistent infection (PI) and calves acutely infected with the same bovine viral diarrhea virus (BVDV) isolate. Two PI calves from 1 dairy herd were necropsied. The PI viruses from these calves were isolated, characterized by sequencing, and found to be identical. This virus strain, designated BVDV2-RS886, was characterized as a noncytopathic (ncp) type 2 BVDV. To establish acute infections, BVDV2-RS886 was used to inoculate clinically healthy, seronegative calves which were 3 weeks to 3 months old. Nine calves received 106–107 tissue culture infective dose of BVDV2-RS886 intranasally. Four additional age-matched animals served as noninfected controls. Infected calves were necropsied at 3, 6, 9, or 13 days postinoculation (dpi). Viral antigen was detected by immunohistochemistry in frozen sections, and lesions were evaluated in hematoxylin eosin–stained paraplast sections. In the PI calves, a wide distribution of viral antigen was found in all tissues and was not associated with lesions. In the acutely infected calves, viral antigen was widespread in lymphoid tissues at 6 dpi but had been mostly eliminated at 9 and 13 dpi. Depletion of lymphoid tissues was seen at 6, 9, and 13 dpi and repopulation at 9 and 13 dpi. In 1 of the calves at 13 dpi, severe arteritis was present in lymph nodes and myocardium. This comparison shows that an ncp BVDV strain that causes no lesions in PI animals is able to induce marked depletion of lymphoid tissues in calves with acute infection. Therefore, the failure to eliminate PI cattle from a herd causes problems not only in pregnant cattle but may also affect other age groups.

Origination and consequences of bovine viral diarrhea virus diversity

The potential consequences of BVDV genetic and antigenic diversity are far ranging. The complexity of clinical presentations associated with BVDV likely arises from factors encoded by the virus genome. More importantly,prevention and control of BVDV may be complicated by diagnostic and immunization failure resulting from virus diversity. Evolutionary pressures will continue to drive further diversity, making control of BVDV challenging. Current and the potential for future BVDV strain diversity should be considered when designing BVDV control programs both at the individual farm and national herd level.

Fusion to C3d enhances the immunogenicity of the E2 glycoprotein of type 2 bovine viral diarrhea virus

The use of DNA and protein subunit vaccines in animals provides an opportunity to introduce vaccines that are arguably the safest that can be developed. For that reason, considerable effort is under way to devise methods of enhancing the immunogenicity of such vaccines. Seven years ago it was shown that fusing complement fragment C3d to hen egg lysozyme (HEL) enhanced the immunogenicity of HEL 10,000-fold. Based on this observation, we decided to evaluate the effect of C3d on the immunogenicity of the E2 protein of bovine viral diarrhea virus (BVDV). E2 is the major target of neutralizing antibody during BVDV infection. To test the effect of C3d on E2 immunogenicity, expression cassettes encoding a secreted form of E2 alone (E2s) or E2 fused to three copies of murine C3d (E2s-C3d) were constructed. The proteins were purified from the supernatants of transfected cells and used to immunize mice. The immune response was monitored by an enzyme-linked immunosorbent assay (ELISA) for E2s-specific antibody and by a virus neutralization test. The ELISA results indicated that the E2s-C3d protein is 10,000-fold more immunogenic than the E2s protein alone. The maximum primary immune response was elicited with <0.1 microg of E2s-C3d protein without an adjuvant. In addition, we have shown for the first time that high levels of anti-E2s and neutralizing antibodies can be elicited when this same low concentration of E2s-C3d is used to both prime and boost the immune response. We conclude that the E2s-C3d fusion protein has significant potential as a subunit vaccine against BVDV infection.

Genetic heterogeneity of bovine viral diarrhoea virus in Italy

The genetic characteristics, of 38 field isolates of bovine viral diarrhoea virus (BVDV) collected in 1999 from sick or healthy and persistently infected cattle of dairy farms situated in northern Italy, were investigated. A partial 5'-untranslated region (5'-UTR) sequence of each isolate was determined and a phylogenetic analysis was performed. All the isolates were classified as belonging to the BVDV-1 genotype and could be assigned to different BVDV-1 groups, namely BVDV-1b (n = 20), BVDV-1d (n = 6) and BVDV-1e (n = 10). Two remaining isolates could be classified as BVDV-1f and BVDV-1h, respectively. These results provided evidence for genetic heterogeneity of BVDV in Italy, and contribute to a better knowledge of the circulation of BVDV strains, and to their classification.

The live attenuated bovine viral diarrhea virus components of a multi-valent vaccine confer protection against fetal infection

Fetal infection with bovine virus diarrhea virus (BVDV) causes severe economic loss and virus spread in cattle. This study investigated the ability of modified live BVDV I and II components of a commercially available modified live virus (MLV) vaccine (Breed-Back FP 10, Boehringer Ingelheim Vetmedica Inc.) to prevent fetal infection and abortion, and therefore the birth of persistently infected animals. Heifers immunized with vaccine 4-8 weeks before insemination showed no adverse effects. All vaccinated animals had seroconverted to BVDV 4 weeks after immunization. Pregnant heifers were divided into two vaccination and two control groups and challenged with type I or II BVDV on days 60-90 of gestation. Seroconversion, clinical signs, immunosuppression, viremia, mortality, abortion rate, and fetal infection were studied. Post-challenge, 6/11 (type I challenged) and 8/11 (type II challenged) vaccinated heifers were free from clinical signs of BVD. Post-challenge clinical signs noted in the vaccinated groups were mild to moderate, while all unvaccinated controls had clinical signs ranging from moderate to severe. Viremia was not detected post-challenge in any of the vaccinated heifers. However, 100% of the controls were BVDV viremic on at least 1 day post-challenge. One of 22 vaccinated heifers had transient leukopenia, whereas 2/8 and 6/7 unvaccinated heifers in control groups I and II, respectively, had transient leukopenia. Type II BVDV infection led to abortion or death in 86% of unvaccinated heifers. The corresponding vaccinated group showed no deaths or abortions. All control group fetuses were infected with BVDV. The test vaccine gave 91% (type I BVDV challenged) and 100% (type II BVDV challenged) protection from fetal infection. This vaccine is safe and effective against fetal infection, abortion (type II BVDV) and the birth of persistently infected animals.

Bovine viral diarrhea virus genomic associations in mucosal disease, enteritis and generalized dermatitis outbreaks in Argentina

The objective of the present work is the description outbreaks caused by bovine viral diarrhea virus (BVDV) in commercial beef cattle ranches in Argentina. Genetic affiliation and their association with the clinical manifestation were carried out with five BVDV isolates from an outbreak of mucosal disease (MD) (Outbreak #1), acute enteritis (Outbreaks #2 and #3) and generalized dermatitis (Outbreaks #4 and #5). Upon genetic analysis CP BVDV isolate of Outbreak #1 clustered to closely to BVDV Oregon (Genotype 1). BVDV isolates from the outbreaks of generalized dermatitis (Outbreaks #4 and #5) were located close to BVDV Osloss within Genotype 1. The identification by immunohistochemistry of BVDV in exudative dermatitis indicates the epithelial cell tropism of the virus. Phylogenic characterization of BVDV from Outbreaks #2 and #3 locate them as BVDV-2. 5'UTR sequence of these viruses revealed a homology of 88 and 90% to BVDV-890 (Genotype 2) and a 77 and 75% to BVDV-SD1 (Genotype 1), respectively. The association of BVDV-2 with severe disease indicates the presence of highly virulent strains. Data from natural outbreaks where BVDV-1 and BVDV-2 were isolated revealed that pathology overlaps and not clearly allows the differentiation between genotypes based on gross or microscopic lesions. Thus, for a definitive diagnosis, further virology and molecular studies are necessary. Additionally, the results of this work focused on the origin and consequences of genetic variations of BVDV with regard to pathogenesis and suggest the association between genotype and a defined clinical syndrome.

Expression of the genomic form of the bovine viral diarrhea virus E2 ORF in a bovine herpesvirus-1 vector

Bovine viral diarrhea virus (BVDV) is a ubiquitous pathogen of cattle with a world-wide distribution. Recently, the possibility of using recombinant virus vectors to immunize cattle against selected BVDV genes has gained widespread interest. Among the virus vectors tested, bovine herpesvirus-1 (BHV1) provides many unique advantages. However, results of recent studies have raised the possibility that the codon usage pattern required for optimal expression in a BHV1-infected cell may be incompatible with the codon usage pattern of BVDV. If true, use of BHV1 to express BVDV proteins would require construction of synthetic BVDV genes that have been modified to resemble the codon pattern of BHV1. To explore this possibility, we constructed a BHV1 recombinant containing the genomic form of the BVDV (NADL) E2 ORF and compared expression of the E2 protein with that of the endogenous BHV1 gD protein. We observed that E2 was expressed at a significant rate compared to that of the gD protein. We conclude that codon usage problems are unlikely to constitute a serious problem for expression of BVDV proteins in BHV1 vectors.

A hepadnavirus regulatory element enhances expression of a type 2 bovine viral diarrhea virus E2 protein from a bovine herpesvirus 1 vector

Recently, the possibility of using virus vectors to immunize cattle against selected bovine viral diarrhea virus (BVDV) genes has gained widespread interest. However, when we attempted to express the E2 protein from type 2 (890 strain) BVDV in a bovine herpesvirus 1 (BHV1) vector, we observed that expression was poor. This often happens when genes from a cytoplasmic virus are expressed in the cell nucleus. To counter this effect, we attempted to enhance expression by a strategy employed by viruses. RNAs of retroviruses and hepadnaviruses contain cis-acting elements that facilitate expression of RNAs that otherwise are degraded or retained within the nucleus. In Mason-Pfizer monkey virus, the required RNA sequence element is known as a constitutive transport element (CTE). A related element from woodchuck hepatitis virus is known as the woodchuck posttranscriptional regulatory element (WPRE). We tested the ability of the CTE, the WPRE, and introns to enhance expression of E2. All three elements stimulated expression of E2 from plasmids. The combination of the WPRE and an intron yielded the highest level of E2 expression in plasmids. However, when E2 was expressed from a BHV1 vector, the presence of an intron was inhibitory. In contrast, the WPRE was very efficient at stimulating E2 expression from a BHV1 vector. This result represents the first expression of a type 2 BVDV E2 protein from a mammalian virus vector and raises the possibility that the WPRE may provide a general method of enhancing foreign gene expression from BHV1 and other herpesvirus vectors.

Differential effects of bovine viral diarrhoea virus on monocytes and dendritic cells

Various pathogens have been shown to infect antigen-presenting cells and affect their capacity to interact with and stimulate T-cell responses. We have used an antigenically identical pair of non-cytopathic (ncp) and cytopathic (cp) bovine viral diarrhoea virus (BVDV) isolates to determine how the two biotypes affect monocyte and dendritic cell (DC) function. We have shown that monocytes and DCs are both susceptible to infection with ncp BVDV and cp BVDV in vitro. In addition, monocytes infected with ncp BVDV were compromised in their ability to stimulate allogeneic and memory CD4(+) T cell responses, but DCs were not affected. This was not due to down-regulation of a number of recognized co-stimulatory molecules including CD80, CD86 and CD40. Striking differences in the response of the two cell types to infection with cytopathic virus were seen. Dendritic cells were not susceptible to the cytopathic effect caused by cp BVDV, whereas monocytes were killed. Analysis of interferon (IFN)-alpha/beta production showed similar levels in monocytes and DCs exposed to cp BVDV, but none was detected in cells exposed to ncp BVDV. We conclude that the prevention of cell death in DCs is not associated with enhanced production of IFN-alpha/beta, as proposed for influenza virus, but is by a distinct mechanism.

Lesions and tissue distribution of viral antigen in severe acute versus subclinical acute infection with BVDV2

Differences in the distribution and spread of viral antigen, development of lesions and correlation between presence of viral antigen and lesions were compared between a low and highly virulent strain of BVDV2. Two groups of two-week- to two-month-old colostrum-deprived calves were inoculated intranasally with the naturally occurring low virulent BVDV2 strain 28508-5 or the highly virulent strain 1373. To study the sequence of virus spread and lesion development, calves were necropsied at days three, six, eight-nine and 12 to 14 post inoculation (pi). Viral antigen was detected by the indirect immunoperoxidase method in cryostat sections and lesions were evaluated in H&E-stained paraffin sections. Clinical signs and changes in lymphocyte and thrombocyte numbers confirmed the difference in virulence between the two strains. Both strains showed comparable initial infection and spread at day three pi. At day six pi, they were found widespread in lymphoid tissues and multifocally in intestinal mucosa. Lesions were very mild despite the large amount of antigen in the lymphoid tissues. After day six pi, differences between the low and highly virulent strains became more prominent. The strain of low virulence was cleared from the tissues, but there was a transient phase of depletion. The highly virulent strain continued to spread to different organs and there was severe depletion of lymphoid tissues without recovery.

Bovine viral diarrhoea virus infections and its control. A review

Infections with bovine viral diarrhoea virus continue to plague the cattle industry worldwide. The wish to control the negative effects of the virus has lead to the development of numerous vaccines, but also of eradication schemes. In this paper, a comprehensive overview on BVDV is given: the virus and its clinical manifestations, its occurrence and economic impact, the different routes of transmission, as well as diagnostic methods and objectives. Furthermore, the two major options for BVDV control--eradication and vaccination--are discussed as well as the risk for reintroduction of BVDV after eradication.

Distribution of viral antigen and development of lesions after experimental infection with highly virulent bovine viral diarrhea virus type 2 in calves

OBJECTIVE

To correlate tissue distribution with development of lesions after experimental infection with a virulent strain of noncytopathic bovine viral diarrhea virus (BVDV) type 2 in calves.

ANIMALS

Ten 14-day-old and two 2-month-old colostrum-deprived calves.

PROCEDURE

Calves were intranasally inoculated with BVDV type-2 strain 1373 from an outbreak of clinically severe bovine viral diarrhea (BVD). Two 14-day-old calves served as noninfected controls. Two calves each were euthanatized on postinoculation days 3, 6, and 12, and 1 each on days 8, 9, 13, and 14. Tissues were collected for immunohistologic and histologic examination.

RESULTS

Inoculated calves developed nonspecific clinical signs characterized by high fever and decreased numbers of leukocytes and thrombocytes. Viral antigen was detected focally in lymphoid tissues on day 3. On days 6, 8, 9, 12, and 14, viral antigen became increasingly widespread throughout organs and tissues. Viral antigen in lymphoid tissues was associated with severe depletion of all compartments. Lesions in other tissues were not well correlated with distribution of viral antigen. Depletion of lymphoid tissues was observed in a calf on day 13, but viral antigen had been cleared from most tissues and was detected in vascular walls only.

CONCLUSIONS AND CLINICAL RELEVANCE

Infection with a virulent BVDV strain resulted in wide dissemination of viral antigen in host tissues. Severe lymphoid depletion developed in lymphoid tissues, whereas viral antigen was generally not associated with lesions in other tissues. Findings suggest that development of lesions in acute BVD is not solely a function of viral replication and is also attributable to host reaction to infection.

Serologic evaluation of five unvaccinated heifers to detect herds that have cattle persistently infected with bovine viral diarrhea virus

OBJECTIVE

To determine whether serologic evaluation of 5 unvaccinated 6- to 12-month-old heifers is a valid method for identifying herds that contain cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV).

ANIMALS

14 dairy herds with a history of BVDV infection, with health problems consistent with BVDV infection, or at risk for contracting BVDV infection.

PROCEDURE

5 unvaccinated 6- to 12-month-old heifers were randomly selected from each herd. Neutralizing antibody titers for type-I and -II BVDV were determined. A herd was classified as likely to contain PI cattle when at least 3/5 heifers had antibody titers > or = 128. Virus isolation was performed on all cattle to identify PI cattle. Genotype of isolated viruses was determined by nested multiplex polymerase chain reaction.

RESULTS

6 of 14 herds contained PI cattle. Sensitivity and specificity of serologic evaluation of 5 heifers for identifying these herds were 66 and 100%, respectively. In herds that contained PI cattle, the predominant BVDV titer in the tested heifers corresponded to the genotype of the isolated virus.

CONCLUSIONS AND CLINICAL RELEVANCE

Serologic evaluation of unvaccinated 6- to 12- month-old heifers is an accurate method for identifying herds containing PI cattle. Both type-I and -II BVDV antibody titers should be determined to prevent herd misclassification. The genotype of BVDV found in PI cattle can be predicted by the predominant neutralizing antibody titers found in tested heifers. Serologic evaluation of 5 unvaccinated heifers can be used to determine whether a herd is likely to contain PI cattle.

Virus neutralising antibodies against 22 bovine viral diarrhoea virus isolates in vaccinated calves

Seven of nine colostrum deprived calves, free from bovine viral diarrhoea virus (BVDV), were vaccinated with a commercially available vaccine containing two inactivated strains of BVDV, an inactivated strain of bovine herpesvirus-1 and modified-live strains of bovine respiratory syncytial virus and para-influenza-3 virus. The two other calves were kept as controls. The virus neutralising (VN) antibodies induced by vaccination were tested against 22 antigenically diverse BVDV isolates, including reference strains and field isolates, both cytopathic and non-cytopathic, as well as genotypes I and II. The strains were isolated in Belgium, France, Germany, the United Kingdom and the USA. While there were variations in the VN titres of the individual calves against all the strains, serum from the seven animals neutralised 20 or more of the strains tested. From the results, it can be concluded that the vaccine can stimulate the production of VN antibodies capable of neutralising a wide range of European and American isolates of BVDV, including genotypes I and II.