A bovine viral diarrhea virus type 1a strain in China: isolation, identification, and experimental infection in calves

Pathogenicity assessment of a bovine viral diarrhea virus type 1l (BVDV-1l) strain in experimentally infected calves

Bovine viral diarrhea is a widespread and economically important viral disease for livestock which can cause clinically diverse manifestations. The number of established BVDV subgenotypes has increased, not only the serological relationships of recently described subgenotypes but virulence and pathogenic characteristics have not yet been mostly elaborated. The dominant BVDV subgenotype in Turkiye was elaborated to be BVDV-1l, that involves more than half of field strains and there is no scientific data to identify the pathogenicity of this strain so far. This study investigated the pathogenicity of a selected field strain (TR-72) from subgenotype BVDV-1l. Experimental infection was implemented by intranasal inoculation of the strain TR-72 (10 ×105.5) to four young calves which were previously not vaccinated and were free both for BVDV antibodies and antigens. Clinical changes as well as blood parameters, body temperature, and viremia were monitored for 14 days. Only mild clinical signs associated with respiratory signs of BVDV infection were observed. Detected clinical signs included nasal discharge, conjunctivitis, cough, fatigue, high rectal temperature reaching 40.7 ℃, and white blood cell counts depression started from the 2nd day and 40.4% decreased between the 12th and 14th days post-infection (poi). The presence of viremia was investigated by virus isolation, RT-PCR, and real-time RT-PCR from blood samples. The efficiency of experimental infection was established not only by observed clinical signs but also by virus isolation from blood leukocytes between the 5th and 8th days poi., virus detection was obtained by real-time PCR between the 3rd - 13th days poi. Besides, the recorded mild clinical signs, high fever, long duration of viremia , and high decrease in blood parameters obtained in this study, it was shown that the noncytopathogenic BVDV-1l strain TR-72 has a moderate virulence in naïve cattle.

Pestivirus A Bovine viral diarrhea virus type 1 species genotypes circulating in China and Turkey

Background

Pestivirus A Bovine viral diarrhea virus type 1 (BVDV-1) is a heterogeneous species within the genus, affecting cattle and other ruminants, with economic impact on livestock production.

Aim

The study aimed to update the taxonomy of the Pestivirus A, BVDV-1 species and to verify the clustering of the strains reported as genotype 1v, originating from different countries.

Methods

Recently deposited strains from China, Turkey, and Iran have been evaluated by the palindromic nucleotide substitutions (PNS) genotyping method.

Results

Based on secondary structure analysis of the 5'-UTR sequences, strains reported as 1v from China were clustered as sub genotype 1.7.3 (1o). Genotype 1.19 (1w) was restricted to China and genotype 1.21 (1v) was present only in Turkey and Iran.

Conclusion

The application of the PNS method clarified the taxonomical status of strains, revealing the homonymy of genetically different clusters. Furthermore, these observations indicated geographic segregation in the Pestivirus A species, and confirmed the occurrence of new atypical genetic variants, with potential implications on control and prophylaxis.

Isolation of BVDV-1a, 1m, and 1v strains from diarrheal calf in china and identification of its genome sequence and cattle virulence

Bovine viral diarrhea virus (BVDV) is an important livestock viral pathogen responsible for causing significant economic losses. The emerging and novel BVDV isolates are clinically and biologically important, as there are highly antigenic diverse and pathogenic differences among BVDV genotypes. However, no study has yet compared the virulence of predominant genotype isolates (BVDV-1a, 1b, and 1m) in China and the emerging genotype isolate BVDV-1v. The serological relationship among these genotypes has not yet been described. In this study, we isolated three BVDV isolates from calves with severe diarrhea, characterized as BVDV-1a, 1m, and novel 1v, based on multiple genomic regions [including 5-untranslated region (5'-UTR), Npro, and E2] and the phylogenetic analysis of nearly complete genomes. For the novel genotype, genetic variation analysis of the E2 protein of the BVDV-1v HB-03 strain indicates multiple amino acid mutation sites, including potential host cell-binding sites and neutralizing epitopes. Recombination analysis of the BVDV-1v HB-03 strain hinted at the possible occurrence of cross-genotypes (among 1m, 1o, and 1q) and cross-geographical region transmission events. To compare the pathogenic characters and virulence among these BVDV-1 genotypes, newborn calves uninfected with common pathogens were infected intranasally with BVDV isolates. The calves infected with the three genotype isolates show different symptom severities (diarrhea, fever, slowing weight gain, virus shedding, leukopenia, viremia, and immune-related tissue damage). In addition, these infected calves also showed bovine respiratory disease complexes (BRDCs), such as nasal discharge, coughing, abnormal breathing, and lung damage. Based on assessing different parameters, BVDV-1m HB-01 is identified as a highly virulent strain, and BVDV-1a HN-03 and BVDV-1v HB-03 are both identified as moderately virulent strains. Furthermore, the cross-neutralization test demonstrated the antigenic diversity among these Chinese genotypes (1a, 1m, and 1v). Our findings illustrated the genetic evolution characteristics of the emerging genotype and the pathogenic mechanism and antigenic diversity of different genotype strains, These findings also provided an excellent vaccine candidate strain and a suitable BVDV challenge strain for the comprehensive prevention and control of BVDV.

Non-structural proteins of bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) belongs to the family Flaviviridae genus pestivirus. The viral genome is a single-stranded, positive-sense RNA that encodes four structural proteins (i.e., C, Erns, E1, and E2) and eight non-structural proteins (NSPs) (i.e., Npro, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B). Cattle infected with BVDV exhibit a number of different clinical signs including diarrhea, abortion, and other reproductive disorders which have a serious impact on the cattle industry worldwide. Research on BVDV mainly focuses on its structural protein, however, progress in understanding the functions of the NSPs of BVDV has also been made in recent decades. The knowledge gained on the BVDV non-structural proteins is helpful to more fully understand the viral replication process and the molecular mechanism of viral persistent infection. This review focuses on the functions of BVDV NSPs and provides references for the identification of BVDV, the diagnosis and prevention of Bovine viral diarrhea mucosal disease (BVD-MD), and the development of vaccines.

Serological evidence of bovine viral diarrhea virus and peste des petits ruminants virus infection in alpacas (Vicugna pacos) in Shanxi Province, northern China

Bovine viral diarrhea virus (BVDV) and peste des petits ruminants virus (PPRV) are two important pathogens associated with a variety of disease syndromes that result in substantial financial losses in animal husbandry. This study was performed to assess the seroprevalence of antibodies to BVDV and PPRV among alpacas raised in Shanxi Province of northern China. Serum samples were obtained from 246 alpacas in Taiyuan (n=182), Xinzhou (n=31), and Jinzhong cities (n=33) of Shanxi Province, and serological testing was carried out using the competitive enzyme-linked immunosorbent assay. Overall seroprevalence to BVDV was 3.25% (95% CI 1.03-5.47), and seropositive alpacas were found only in Taiyuan City. The overall PPRV seroprevalence in alpacas was 28.86% (95% CI 23.20-34.52). While no PPRV-seropositive alpacas were found in Xinzhou City, the seroprevalence of PPRV was 90.91% (95% CI 81.10-100.72) in Jinzhong City and 22.53% (95% CI 16.46-28.60) in Taiyuan City, respectively, which showed a statistically significant difference. To our knowledge, the present work is the first report on seroprevalence of BVDV and PPRV in alpacas in China, which provides baseline information for the control of infection.

Molecular detection and genotyping of bovine viral diarrhea virus in Western China

BACKGROUND

Bovine viral diarrhea virus (BVDV) is an important global viral pathogen of cattle and other ruminants. To survey the infection rate and genetic diversity of BVDV in western China, a total of 1234 serum samples from 17 herds of dairy cattle, beef cattle and yak in 4 provinces were collected in 2019.

RESULTS

All the 1234 serum samples were screened individually for BVDV by RT-PCR. Our results demonstrated that the average positive rate of BVDV was 7.2% (89/1234) in animals and 82.4% (14/17) in herds. Thirteen BVDV strains were isolated from RT-PCR positive clinical samples and they were all NCP biotype. BVDV-1a and 1c subgenotypes were identified from 22 selected virus isolates in 14 BVDV-positive herds. These results confirmed that BVDV-1a and BVDV-1c were circulating in western China, similar to the BVDV epidemics in cattle in other regions of China.

CONCLUSIONS

This study provides data for monitoring and vaccination strategies of BVDV in western China.

Immunogenicity evaluation of recombinant Lactobacillus casei W56 expressing bovine viral diarrhea virus E2 protein in conjunction with cholera toxin B subunit as an adjuvant

BACKGROUND

Bovine viral diarrhea virus (BVDV) is one of the main causes of infectious diseases in cattle and causes large financial losses to the cattle industry worldwide. In this study, Lactobacillus casei strain W56 (Lc W56) was used as antigen deliver carrier to construct a recombinant Lactobacillus vaccine pPG-E2-ctxB/Lc W56 constitutively expressing BVDV E2 protein fused with cholera toxin B subunit (ctxB) as an adjuvant, and its immunogenicity against BVDV infection in mice model by oral route was explored.

RESULTS

Our results suggested that pPG-E2-ctxB/Lc W56 can effectively activate dendritic cells (DCs) in the Peyer's patches, up-regulate the expression of Bcl-6, and promote T-follicular helper (Tfh) cells differentiation, as well as enhance B lymphocyte proliferation and promote them differentiate into specific IgA-secreting plasma cells, secreting anti-E2 mucosal sIgA antibody with BVDV-neutralizing activity. Moreover, significant levels (p < 0.01) of BVDV-neutralizing antigen-specific serum antibodies were induced in the pPG-E2-ctxB/LC W56 group post-vaccination. The recombinant Lactobacillus vaccine can induce cellular immune responses, and significant levels (p < 0.01) of Th1-associated cytokines (IL-2, IL-12, and IFN-γ), Th2-associated cytokines (IL-4, IL-10) and Th17-associated cytokine (IL-17) were determined in the serum of vaccinated mice. Significantly, the recombinant Lactobacillus vaccine provides immune protection against BVDV infection, which can be cleared effectively by the vaccine post-challenge in orally vaccinated animals.

CONCLUSIONS

The genetically engineered Lactobacillus vaccine constructed in this study is immunogenic in mice and can induce mucosal, humoral, and cellular immune responses, providing effective anti-BVDV immune protection. It thus represents a promising strategy for vaccine development against BVDV.

Genetic Diversity of Bovine Pestiviruses Detected in Backyard Cattle Farms Between 2014 and 2019 in Henan Province, China

Bovine pestiviruses include Pestivirus A (BVDV-1), Pestivirus B (BVDV-2), and Pestivirus H, which was originally called HoBi-like pestivirus. We conducted an epidemiological investigation for pestiviruses circulating in backyard cattle farms in central China. RT-PCR assays and sequences analysis were conducted on 54 nasal swabs, 26 serum samples, and three lung samples from cattle with respiratory infections and identified 29 pestivirus strains, including 24 Pestivirus A and five Pestivirus H strains. Phylogenetic analysis based on partial 5'-UTR and Npro sequences showed that the genotypes of 24 Pestivirus A strains included Pestivirus A 1b (six isolates), Pestivirus A 1m (six isolates), Pestivirus A 1q (two isolates), Pestivirus A 1u (one isolates), and Pestivirus A 1o (nine isolates, a putative new sub-genotype). In addition, a single Pestivirus H agenotype included all five Pestivirus H strains. This study revealed extensive genetic variations within bovine pestivirus isolates derived from cattle in backyard farms in Central China, and this epidemiological information improves our understanding of the epidemics of bovine Pestiviruses, as well as will be useful in designing and evaluating diagnostic methods and developing more effective vaccines.

Genomic characteristics of classical swine fever virus strains of bovine origin according to primary and secondary sequence-structure analysis

Background:

Classical swine fever virus (CSFV), species member of the family Flaviviridae, is generally considered restricted to domestic and wild suids. The circulation of CFSV has been detected in cattle herds in China and India. Natural infection appeared associated with clinical signs in some cases.

Aim:

The secondary structures of the internal ribosome entry site in the 5′ untranslated region (UTR) were used for the genomic characterization of bovine strains.

Methods:

Sequences have been compared to the representative CSFV strains isolated from pigs, vaccines, and contaminants from porcine cell lines and an ovine strain isolated in Spain.

Results:

The observed sequences from cattle showed a genetic relatedness with live-attenuated vaccine strains used in pigs. Sequence characteristics of the Chinese strain S171 are genetically distant from the previously reported CSFV genotypes, suggesting a new outgroup in the species, described for the first time, and named CSFV-d. Other Chinese strains were genetically closely related to CSFV genotype a2 (Alfort type) pig strains. Indian strains, reported from the states of Tamil Nadu and Meghalaya, were genetically closely related to CSFV genotype a1 (Brescia type) and a5 pig strains, respectively.

Conclusion:

These preliminary observations are new and relevant in countries, where CSFV control and eradication strategies are applied.

Prevalence and genetic diversity of bovine viral diarrhea virus in dairy herds of China

To determine the nationwide prevalence and genetic diversity of bovine viral diarrhea virus (BVDV) in China, 92 dairy farms with more than 500 animals in 19 provinces of China were surveyed in 2017. At each farm, ear notch samples from calves less than six months old and bulk tank milk (BTM) samples were collected. A total of 901 ear notch samples and 329 BTM samples from 183 tanks were sampled. A total of 20 (20/901, 2.22 %) ear notch samples from 10 (10/92, 10.86 %) farms tested positive for BVDV by IDEXX Antigen Point-of-Care (POC) Test kit and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). In addition, 80 of 183 (80/183, 43.7 %) BTM samples from 43 (43/92, 46.7 %) farms were identified as positive by qRT-PCR. The RNA of positive and suspect samples identified by qRT-PCR was subjected to 5'- untranslated region (UTR) amplification by nested RT-PCR and then sequenced. A total of 119 sequences were obtained and phylogenetic analysis of these 5'-UTR sequences revealed the presence of eight different subgenotypes of BVDV-1 including 1a (n = 37, 31.09 %), 1b (n = 5, 4.20 %), 1c (n = 34, 28.57 %), 1d (n = 2, 1.68 %), 1m (n = 25, 21.01 %), 1q (n = 6, 5.04 %), and two unknown subgenotypes which were tentatively typed as "BVDV-1v" (n = 8, 6.72 %) and "BVDV-1w" (n = 2, 1.68 %), respectively. BVDV-1a, 1c, and 1m were the dominant strains, collectively accounting for 80.67 % (96/119) of all sequences. Phylogenetic analysis based on selected N-terminal autoprotease (N^pro) sequences confirmed the classification of the 5'-UTR sequences. In conclusion, the prevalence of BVDV persistent infection in dairy cattle was high and genetic diversity was high and increasing, revealing a serious threat to the health of cattle in China and highlighting the need for BVDV control.

Dendritic Cell Targeting of Bovine Viral Diarrhea Virus E2 Protein Expressed by Lactobacillus casei Effectively Induces Antigen-Specific Immune Responses via Oral Vaccination

Bovine viral diarrhea caused by bovine viral diarrhea virus (BVDV) is an important disease in cattle, resulting in significant economic losses to the cattle industry worldwide. In order to develop an effective vaccine against BVDV infection, we constructed a dendritic cell (DC)-targeting oral probiotic vaccine (pPG-E2-DCpep/LC W56) using Lactobacillus casei as antigen delivery carrier to express BVDV glycoprotein E2 fused with DC-targeting peptide, and the immunogenicity of orally administered probiotic vaccine was evaluated in mice model. Our results showed that after immunization with the probiotic vaccine, significantly levels of antigen-specific sera IgG and mucosal sIgA antibodies (p < 0.05) with BVDV-neutralizing activity were induced in vivo. Challenge experiment showed that pPG-E2-DCpep/LC W56 can provide effective immune protection against BVDV, and BVDV could be effectively cleared from the intestine of immunized mice post-challenge. Moreover, the pPG-E2-DCpep/LC W56 could efficiently activate DCs in the intestinal Peyer’s patches, and significantly levels of lymphoproliferative responses, Th1-associated IFN-γ, and Th2-associated IL-4 were observed in mice immunized with pPG-E2-DCpep/LC W56 (p < 0.01). Our results clearly demonstrate that the probiotic vaccine could efficiently induce anti-BVDV mucosal, humoral, and cellular immune responses via oral immunization, indicating a promising strategy for the development of oral vaccine against BVDV.

Who's who in the Bovine viral diarrhea virus type 1 species: Genotypes L and R

The bovine viral diarrhea virus type 1 species is responsible for cosmopolitan diseases affecting cattle and other ruminants, with relevant impact on animal production. The species presents high genomic heterogeneity, with implications on control and prophylactic programs. Genomic traits of different genetic groups are often related to geographic origin. Atypical sequences have been reported from Pestivirus isolates originated from cattle in Turkey. Based on phylogenetic analysis of 5' untranslated region and Npro and secondary structure analysis of the 5'-UTR RNA, Turkish isolates have been segregated in two distinct genotypes. Out of the twenty-three identified BVDV-1 genotypes, the Turkish clusters, named L and R or 1.16 and 1.14, according to palindromic nucleotide substitution genotyping method, represent genomic clusters so far, not described elsewhere, suggesting geographic segregation. In order to avoid confusion in the current taxonomy of the species, nomenclature of described homonymous genotypes, referred to different genomic clusters, should be corrected.

Bovine viral diarrhea virus type 1 current taxonomy according to palindromic nucleotide substitutions method

Pestivirus bovine viral diarrhea virus type 1 species is responsible for cosmopolitan diseases affecting cattle and other ruminants, presenting a wide range of clinical manifestations, with relevant impact on zootechnic production. Understanding genomic characteristic and virus taxonomy is fundamental in order to sustain control and prophylactic programs. Given the recent various studies reporting a relatively high number of new strains, in particular from Asian countries, in the present study, four hundred-eighty-two genomic sequences have been evaluated applying the palindromic nucleotide substitutions method for genotyping. Based on the secondary structure alignment and computing genetic distance among strains in the 5' untranslated region of Pestivirus RNA, the current taxonomy of the species was reviewed. Twenty-two genotypes have been identified, applying a nomenclature based on divergence in the genus.

In Vivo Characterisation of Five Strains of Bovine Viral Diarrhoea Virus 1 (Subgenotype 1c)

Bovine viral diarrhoea virus 1 (BVDV-1) is strongly associated with several important diseases of cattle, such as bovine respiratory disease, diarrhoea and haemoragic lesions. To date many subgenotypes have been reported for BVDV-1, currently ranging from subgenotype 1a to subgenotype 1u. While BVDV-1 has a world-wide distribution, the subgenotypes have a more restricted geographical distribution. As an example, BVDV-1 subgenotypes 1a and 1b are frequently detected in North America and Europe, while the subgenotype 1c is rarely detected. In contrast, BVDV-1 subgenotype 1c is by far the most commonly reported in Australia. Despite this, uneven distribution of the biological importance of the subgenotypes remains unclear. The aim of this study was to characterise the in vivo properties of five strains of BVDV-1 subgenotype 1c in cattle infection studies. No overt respiratory signs were reported in any of the infected cattle regardless of strain. Consistent with other subgenotypes, transient pyrexia and leukopenia were commonly identified, while thrombocytopenia was not. The quantity of virus detected in the nasal secretions of transiently infected animals suggested the likelihood of horizontal transmission was very low. Further studies are required to fully understand the variability and importance of the BVDV-1 subgenotype 1c.

Variability and Global Distribution of Subgenotypes of Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is a globally-distributed agent responsible for numerous clinical syndromes that lead to major economic losses. Two species, BVDV-1 and BVDV-2, discriminated on the basis of genetic and antigenic differences, are classified in the genus Pestivirus within the Flaviviridae family and distributed on all of the continents. BVDV-1 can be segregated into at least twenty-one subgenotypes (1a–1u), while four subgenotypes have been described for BVDV-2 (2a–2d). With respect to published sequences, the number of virus isolates described for BVDV-1 (88.2%) is considerably higher than for BVDV-2 (11.8%). The most frequently-reported BVDV-1 subgenotype are 1b, followed by 1a and 1c. The highest number of various BVDV subgenotypes has been documented in European countries, indicating greater genetic diversity of the virus on this continent. Current segregation of BVDV field isolates and the designation of subgenotypes are not harmonized. While the species BVDV-1 and BVDV-2 can be clearly differentiated independently from the portion of the genome being compared, analysis of different genomic regions can result in inconsistent assignment of some BVDV isolates to defined subgenotypes. To avoid non-conformities the authors recommend the development of a harmonized system for subdivision of BVDV isolates into defined subgenotypes.

Molecular Characterization of a Novel Bovine Viral Diarrhea Virus Isolate SD-15

As one of the major pathogens, bovine viral diarrhea virus caused a significant economic loss to the livestock industry worldwide. Although BVDV infections have increasingly been reported in China in recent years, the molecular aspects of those BVDV strains were barely characterized. In this study, we reported the identification and characterization of a novel BVDV isolate designated as SD-15 from cattle, which is associated with an outbreak characterized by severe hemorrhagic and mucous diarrhea with high morbidity and mortality in Shandong, China. SD-15 was revealed to be a noncytopathic BVDV, and has a complete genomic sequence of 12,285 nucleotides that contains a large open reading frame encoding 3900 amino acids. Alignment analysis showed that SD-15 has 93.8% nucleotide sequence identity with BVDV ZM-95 isolate, a previous BVDV strain isolated from pigs manifesting clinical signs and lesions resembling to classical swine fever. Phylogenetic analysis clustered SD-15 to a BVDV-1m subgenotype. Analysis of the deduced amino acid sequence of glycoproteins revealed that E2 has several highly conserved and variable regions within BVDV-1 genotypes. An additional N-glycosylation site (240NTT) was revealed exclusively in SD-15-encoded E2 in addition to four potential glycosylation sites (Asn-X-Ser/Thr) shared by all BVDV-1 genotypes. Furthermore, unique amino acid and linear epitope mutations were revealed in SD-15-encoded E^rns glycoprotein compared with known BVDV-1 genotype. In conclusion, we have isolated a noncytopathic BVDV-1m strain that is associated with a disease characterized by high morbidity and mortality, revealed the complete genome sequence of the first BVDV-1m virus originated from cattle, and found a unique glycosylation site in E2 and a linear epitope mutation in E^rns encoded by SD-15 strain. Those results will broaden the current understanding of BVDV infection and lay a basis for future investigation on SD-15-related pathogenesis.

Virulent Properties of Russian Bovine Viral Diarrhea Virus Strains in Experimentally Infected Calves

The results of experimental study of three noncytopathic and two cytopathic bovine viral diarrhea virus (BVDV) strains isolated from cattle in the Siberian region and belonging to the type 1 (subtypes 1a, 1b, and 1d) have been presented. All investigated strains caused the development of infectious process in the seronegative 4-6-month-old calves after aerosol challenge with the dose of 6 log10 TCID50. The greatest virulence had noncytopathic strain and cytopathic strain related to the subtypes 1d and 1b, respectively. All strains in infected calves caused some signs of moderate acute respiratory disease and diarrhea: depression 3-5 days postinfection (p.i.), refusal to food, severe hyperthermia to 41.9°С, serous exudate discharges from the nasal cavity and eyes, transient diarrhea with blood, leukopenia (up to 2700 cells/mm(3)), and macroscopic changes in the respiratory organs and intestine. The infected animals recovered from 12 to 15 days p.i. and in 90% cases formed humoral immune response 25 days p.i. (antibody titers to BVDV: 1 : 4-1 : 16). Our results confirmed the presence of virulent BVDV1 strains and showed the need for researches on the molecular epidemiology of the disease, development of more effective diagnostic systems, and optimization of control programs with use of vaccines.

Immunogenicity of an inactivated Chinese bovine viral diarrhea virus 1a (BVDV 1a) vaccine cross protects from BVDV 1b infection in young calves

Bovine viral diarrhea virus (BVDV) 1a and 1b strains are the predominant subgenotypes in China. Because of the genetic and antigenic variability among different BVDV strains, a vaccine effective in one region may fail to protect against infections caused by different virus strains in another region. No BVDV vaccine developed with the predominant strains in China are available. In this study, the immunogenicity of an inactivated Chinese BVDV 1a NM01 vaccine strain was evaluated by challenging with a Chinese BVDV 1b JL strain. Ten 2-4-month-old calves were intramuscularly vaccinated with a single dose of the vaccine strain and boosted with same dose three weeks after the first vaccination, with five mock immunized calves serving as a control group. The average titer of neutralization antibody to BVDV 1a and BVDV 1b of immunized calves reached 1:410 and 1:96, respectively, at 21 days post the second vaccination. Twenty-one days post the second vaccination, all calves were challenged with strain JL. The clinical signs, such as the temperature and leukopenia of the immunized calves and viral shedding, were significantly less than the mock immunized calves after challenging with the virulent BVDV 1b strain, indicating that the BVDV 1a vaccine strain elicited efficacious protection against the endemic BVDV 1b strain in China. To the best of our knowledge, this is the first report of an inactivated BVDV vaccine which demonstrated effective cross-protection against BVDV type 1b infection in China.