Antibody titers to vaccination are not predictive of level of protection against a BVDV type 1b challenge in Bos indicus - Bos taurus steers

Effect of exogenous melatonin on the cellular response of Holstein heifer calves during vaccination

Despite rigorous vaccination protocols, calf morbidity is the primary contributor to economic loss in the calf sector of the dairy industry. Melatonin has modulated immune response in other mature animal species. We hypothesized that exogenous melatonin may improve the cellular response to vaccination in dairy calves. Our objective was to evaluate the effect of exogenous melatonin on polymorphonuclear leukocyte (PMN) function in Holstein heifer calves during immunization. Sixty neonatal Holstein heifers were enrolled by birth cohort (block) and randomized to one of four treatments: control (CON), vaccination of 0.5 mg ovalbumin on days 0 and 21 (VAC), implantation of 24 mg melatonin on day 0 (MEL), or both melatonin and vaccine treatments (MVAC). Jugular blood was collected on days 0, 21, 42, and 63 to measure circulating melatonin, anti-ovalbumin immunoglobulin-G, and PMN function. Calves implanted with melatonin had greater circulating melatonin than non-implanted on day 21 (P < 0.01). Anti-ovalbumin IgG was greater for vaccinated than non-vaccinated calves (P < 0.01). Anti-ovalbumin IgG was greater for MVAC than VAC calves on day 63. Percent of cells and mean florescence intensity of cells performing oxidative burst decreased from day 0 to day 63 (P < 0.01) but were not affected by treatment (P ≥ 0.26). There was a tendency (P = 0.10) for an interaction of melatonin, vaccination, and day for the mean florescence intensity of cells performing phagocytosis where MVAC was greater than all other treatments on d 42. Exogenous melatonin may alter PMN function of calves during vaccination. Further research is needed to define the effect of melatonin on development of antigen-specific IgG during programmed vaccination protocols.

Immune phenotype is differentially affected by changing the type of bovine respiratory disease vaccine administered at revaccination in beef heifers

During preconditioning, modified-live vaccines are frequently administered to beef calves before weaning. In this study, we began to characterize the immune phenotype of calves that received a modified-live vaccination at 3-4 months of age and then either received the same modified-live or an inactivated vaccine upon arrival at the feedlot (weaning) and 28 days post-arrival (booster). Innate and adaptive immune measures were assessed before revaccination and 14 and 28 days post. Heifers that received three doses of the modified-live vaccine exhibited a relatively balanced immune response based on increases in mean cytokine concentrations (IL-17, IL-21) and total immunoglobulin-G (IgG) and subsets IgG1 and IgG2, which are related to both arms of the adaptive immune system. Conversely, heifers that received one dose of modified live and two doses of the inactivated vaccine had a more robust neutrophil chemotactic response and greater serum-neutralizing antibody titers, resulting in an enhanced innate immune and a skewed proinflammatory response. These results indicate that the revaccination protocol used after initial vaccination with a modified-live vaccine differentially influences the immune phenotype of beef calves, with three doses of modified live inducing potentially immune homeostasis and a combination of modified live and inactivated vaccines inducing a skewed immune phenotype. However, more research is needed to determine the protective efficacy of these vaccination protocols against disease.

Lung Resident Memory T Cells Activated by Oral Vaccination Afford Comprehensive Protection against Pneumonic Yersinia pestis Infection

A growing body of evidence has shown that resident memory T (TRM) cells formed in tissue after mucosal infection or vaccination are crucial for counteracting reinfection by pathogens. However, whether lung TRM cells activated by oral immunization with Yptb1(pYA5199) play a protective role against pneumonic plague remains unclear. In this study, we demonstrated that lung CD4+ and CD8+ TRM cells significantly accumulated in the lungs of orally Yptb1(pYA5199)-vaccinated mice and dramatically expanded with elevated IL-17A, IFN-γ, and/or TNF-α production after pulmonary Yersinia pestis infection and afforded significant protection. Short-term or long-term treatment of immunized mice with FTY720 did not affect lung TRM cell formation and expansion or protection against pneumonic plague. Moreover, the intratracheal transfer of both lung CD4+ and CD8+ TRM cells conferred comprehensive protection against pneumonic plague in naive recipient mice. Lung TRM cell-mediated protection was dramatically abolished by the neutralization of both IFN-γ and IL-17A. Our findings reveal that lung TRM cells can be activated via oral Yptb1(pYA5199) vaccination, and that IL-17A and IFN-γ production play an essential role in adaptive immunity against pulmonary Y. pestis infection. This study highlights an important new target for developing an effective pneumonic plague vaccine.

The Effects of Respiratory Vaccine Type and Timing on Antibody Titers, Immunoglobulins, and Growth Performance in Pre- and Post-Weaned Beef Calves

In order to examine the effects of vaccine type and timing of crossbred beef calves (n = 151) were assigned to one of three BRD vaccination protocols stratified by breed of sire, sex, and date of birth, which included: (1) KM-a pentavalent killed viral (KV) vaccine at 2 to 3 months of age (D 0) and a pentavalent modified-live viral (MLV) vaccine at weaning (D 127); (2) MM-MLV on D 0 and revaccinated on D 127 or (3) WN-MLV at weaning and D 140. Vaccination treatment did not affect performance nor BRSV serum-neutralizing antibody titers. Serum-neutralizing antibody titers to BVDV-1 were greatest for the MM through D 154. However, following booster (KM) or initial vaccination (WN) at D 127, titers increased for the other treatment groups to higher values (KM) by the end of the study. Delay of initial vaccination until weaning may have delayed specific antibody response in the WN group and skewed the immune response towards a Th-1 or cell-mediated response. Overall, the inclusion of an MLV in the vaccine protocol resulted in a more robust antibody response, and the timing of vaccination may affect the onset of efficacious and robust vaccine responses.

One size does not fit all: Exploring the economic and non-economic outcomes of on-farm biosecurity for bovine viral diarrhoea virus in Australian beef production

Bovine viral diarrhoea virus (BVDV) is a disease of global importance, affecting the production and welfare of cattle enterprises through poor reproductive performance and calf mortality. In Australia, the prevention of BVDV introduction and spread is primarily achieved with on-farm biosecurity; however, the use of these practices can vary amongst producers. Economic utility is commonly identified as a contributor to the uptake of on-farm biosecurity, but other factors such as animal welfare, producer priorities and introduction risk also influence farmer behaviour. This study uses an individual-based, stochastic simulation model to examine the economic and non-economic value of 23 on-farm biosecurity combinations for the control of BVDV in Australian beef farms without (N0) and with (N1) a neighbouring population of persistently infected (PI) cattle. Combinations of quarantine of purchased bulls (Q), hygiene during herd health events (H), double-fencing adjacent boundaries with neighbouring farms (F) and vaccination against BVDV (V) were tested. This study is the first to simulate the use of strategic PI exposure (PI) as an alternative to V, a contentious practice performed by some Australian beef farmers. Introduction of BVDV into a naïve 300-breeder self-replacing beef herd was achieved through the purchase of PI bulls (N0 and N1 herds) and over-the-fence contact with neighbouring PI animals (N1 herds only). The predicted median cumulative loss due to BVDV over a 15-year period was AUD$172/breeder and AUD$453/breeder for an N0 and N1 herd, respectively. Early establishment of BVDV in the simulation period was found to be the primary factor contributing to economic loss. Consequently, the Q and QF combinations resulted in the highest predicted average annual cost-benefit for BVDV-free N0 and N1 herds. In the five years following establishment of BVDV, use of QP (N0 herds) and V (N1 herds) combinations were most cost-effective. Combinations that involved V and P (in conjunction with F in N1 herds) also resulted in the lowest number of PI animals sold to other farms or feedlots over the simulation period. However, in both N0 and N1 herds, P resulted in the highest number of infected cattle, which has implications for poor animal welfare and increased antimicrobial use on Australian beef farms. The outcomes reported in this study can guide decisions to prevent BVDV introduction and spread on extensive beef farms using on-farm biosecurity, based on the risk of BVDV exposure and the priorities of the individual farmer.

Vaccination of Sheep with Bovine Viral Diarrhea Vaccines Does Not Protect against Fetal Infection after Challenge of Pregnant Ewes with Border Disease Virus

Border Disease (BD) is a major sheep disease characterized by immunosuppression, congenital disorders, abortion, and birth of lambs persistently infected (PI) by Border Disease Virus (BDV). Control measures are based on the elimination of PI lambs, biosecurity, and frequent vaccination which aims to prevent fetal infection and birth of PI. As there are no vaccines against BDV, farmers use vaccines directed against the related Bovine Viral Diarrhea Virus (BVDV). To date, there is no published evidence of cross-effectiveness of BVDV vaccination against BDV infection in sheep. We tested three commonly used BVDV vaccines, at half the dose used in cattle, for their efficacy of protection against a BDV challenge of ewes at 52 days of gestation. Vaccination limits the duration of virus-induced leukopenia after challenge, suggesting partial protection in transient infection. Despite the presence of BDV neutralizing antibodies in vaccinated ewes on the day of the challenge, fetuses of vaccinated and unvaccinated sheep were, two months after, highly positive for BDV RNA loads and seronegative for antibodies. Therefore, BVDV vaccination at half dose was not sufficient to prevent ovine fetal infection by BDV in a severe challenge model and can only be reconsidered as a complementary mean in BD control.

Effects of Multivalent BRD Vaccine Treatment and Temperament on Performance and Feeding Behavior Responses to a BVDV1b Challenge in Beef Steers

This study examined the effects of multivalent respiratory vaccine treatment (VT) and animal temperament classification on feeding behavior traits, feed intake and animal performance in response to a bovine viral diarrhea virus (BVDV) challenge. Nellore-Angus crossbred steers (n = 360; initial body weight (BW) 330 ± 48 kg) were assigned to one of three vaccine treatments: non-vaccinated (NON), modified live (MLV) and killed (KV) regarding respiratory viral pathogens, and inoculated intranasally with the same BVDV1b strain. Cattle temperament categories were based on exit velocity. Overt clinical signs of respiratory disease were not observed, yet the frequency and duration of bunk visit events as well as traditional performance traits decreased (p < 0.01) following BVDV challenge and then rebounded in compensatory fashion. The reduction in dry matter intake (DMI) was less (p < 0.05) for MLV-vaccinated steers, and MLV-vaccinated steers had longer (p < 0.01) durations of bunk visit and meal events and slower (p < 0.01) eating rates compared with KV- and non-vaccinated steers following BVDV challenge. Greater differences in most feeding behavior traits due to VT existed within calm vs. excitable steers. Respiratory vaccination can reduce the sub-clinical feeding behavior and performance effects of BVDV in cattle, and the same impacts may not occur across all temperament categories.

Do modified live virus vaccines against bovine viral diarrhea induce fetal cross-protection against HoBi-like Pestivirus?

Bovine Pestivirus heterogeneity is a major challenge for vaccines against bovine viral diarrhea (BVD). In breeding herds, fetal protection is a high priority issue. To some degree, fetal infections in vaccinated heifers have been attributed to the antigenic diversity of bovine Pestiviruses. The purpose of this study was to assess fetal protection against a divergent bovine Pestivirus (Hobi-like Pestivirus, HoBiPeV) with a commercially available modified live vaccine (MLV) claiming fetal protection against BVDV 1 and BVDV 2 up to one year after the first inoculation. Five vaccinated and four unvaccinated heifers were challenged by intranasal inoculation with the HoBiPeV Italy-1/10-1 strain between 82 and 89 days after insemination, i.e. between 4 and 6 months after vaccination. At challenge, neutralizing antibody titers to HoBiPeV in vaccinated heifers were low or even undetectable. Of the four unvaccinated heifers, one control animal aborted (fetus not available) and the remaining three gave birth to HoBiPeV positive calves. Among the heifers of the vaccinated group, one aborted the fetus in the sixth month of pregnancy, which tested Pestivirus negative, while three others gave birth to healthy, HoBiPeV negative calves; the remaining heifer delivered one HoBiPeV positive calf. The results suggest that the BVDV vaccine might be able to elicit a partial fetal protection against HobiPeV, even in absence of a strong specific antibody response.

Vaccination Failure in Eradication and Control Programs for Bovine Viral Diarrhea Infection

Vaccination against bovine viral diarrhea (BVD) is one of the key elements to protect cattle herds from this economically important disorder. Bovine viral diarrhea virus (BVDV) is a pestivirus infecting animals at all ages with significant impact on reproductive, digestive, and respiratory systems. Financial burden caused by this pathogen prompts many farmers to introduce vaccination as the control and prophylactic measure especially when persistently infected (PI) individuals, being the main source of the virus in the herd, are removed after test-and-cull approach. The aim of the study was to compare the serological response in cattle herds where new PI calves were identified without prior removal of PI animals or despite their removal and after the introduction of whole herd vaccination against BVDV infection. Overall seroprevalence in 5 vaccinated herds was 91.7 and 83.3% using ELISA and virus neutralization test, respectively. Despite high titers for both vaccine and field strains of BVDV in analyzed herds the analysis of comparative strength of neutralization indicated that 41.4% of positive samples did not have a predominant titer against one specific subtype of BVDV. In 3 herds BVDV-1b subtype was identified while in 2 others it was BVDV-1d, while the vaccine used was based on BVDV-1a which was never identified in Poland so far. To increase the success of the BVDV eradication program, a careful approach is suggested when planning herd vaccination. Comparison of existing field strains and their similarity with vaccine strains at antigenic and genetic levels can be a useful approach to increase the effectiveness of vaccination and efficient protection of fetuses from persistent infection.

The Hendra virus vaccine: perceptions regarding the role of antibody titre testing

OBJECTIVES

To elucidate veterinarians' and horse owners' perceptions towards the use of Hendra virus (HeV) antibody titre testing and how it influences veterinary advice.

METHODS

Six semi-structured phone interviews were conducted with veterinarians who have submitted samples for HeV antibody titre testing. Interviews were recorded, transcribed and thematically analysed to identify and report common themes within the data.

RESULTS

Veterinarians are predominantly using the titre tests as an alternative to vaccination due to clients' fear of vaccine reactions. The high cost of titre testing, the difficulty interpreting titre results and a lack of titre test recognition by authorities were the major barriers reported to using this test. Some veterinarians detailed difficulties communicating titre test procedures and results to their clients. The majority of veterinarians accepted titres of 64 or greater as evidence of protective immunity and would rely on those results for 12 months. However, there was discrepancy of these values and the level of confidence veterinarians had in interpreting the results of HeV antibody titre tests varied.

CONCLUSION

This study has provided an overview of the attitudes of horse owners and veterinarians towards HeV antibody titre testing. Although evidence for HeV vaccination titres as an indication of protective immunity is still inadequate, it will assist veterinarians in interpreting and communicating titre results.

A novel MHC-II targeted BVDV subunit vaccine induces a neutralizing immunological response in guinea pigs and cattle

Bovine viral diarrhoea virus (BVDV) is a major cause of economic loss in the cattle industry, worldwide. Infection results in reduced productive performance, growth retardation, reduced milk production and increased susceptibility to other diseases leading to early culling of animals. There are two primary methods used to control the spread of BVDV: the elimination of persistently infected (PI) animals and vaccination. Currently, modified live or inactivated vaccines are used in BVDV vaccination programmes, but there are safety risks or insufficient protection, respectively, with these vaccines. Here, we report the development and efficacy of the first targeted subunit vaccine against BVDV. The core of the vaccine is the fusion of the BVDV structural protein, E2, to a single-chain antibody, APCH, together termed, APCH-E2. The APCH antibody targets the E2 antigen to the major histocompatibility type II molecule (MHC-II) present on antigen-presenting cells. Industrial production of the vaccine is carried out using the baculovirus expression vector system (BEVS) using single-use manufacturing technologies. This new subunit vaccine induces strong BVDV-specific neutralizing antibodies in guinea pigs and cattle. Importantly, in cattle with low levels of natural BVDV-specific neutralizing antibodies, the vaccine induced strong neutralizing antibody levels to above the protective threshold, as determined by a competition ELISA. The APCH-E2 vaccine induced a rapid and sustained neutralizing antibody response compared with a conventional vaccine in cattle.

Mosaic Bovine Viral Diarrhea Virus Antigens Elicit Cross-Protective Immunity in Calves

Bovine Viral Diarrhea Virus (BVDV) is an important pathogen that plays a significant role in initiating Bovine Respiratory Disease Complex (BRDC) in cattle. The disease causes multi-billion dollar losses globally due to high calf mortality and increased morbidity leading to heavy use of antibiotics. Current commercial vaccines provide limited cross-protection with several drawbacks such as safety, immunosuppression, potential reversion to virulence, and induction of neonatal pancytopenia. This study evaluates two prototype vaccines containing multiple rationally designed recombinant mosaic BVDV antigens for their potential to confer cross-protection against diverse BVDV strains. Genes encoding three novel mosaic antigens, designated E2¹²³, NS2-3¹, and NS2-3², were designed in silico and expressed in mammalian cells for the formulation of a prototype protein-based vaccine. The mosaic antigens contain highly conserved protective epitopes from BVDV-1a, -1b, and -2, and included unique neutralizing epitopes from disparate strains to broaden coverage. We tested immunogenicity and protective efficacy of Expi293^TM-expressed mosaic antigens (293F-E2¹²³, 293F-NS2-3¹, and 293F-NS2-3²), and baculovirus-expressed E2¹²³ (Bac-E2¹²³) mosaic antigen in calves. The Expi293^TM-expressed antigen cocktail induced robust BVDV-specific cross-reactive IFN-γ responses, broadly neutralizing antibodies, and following challenge with a BVDV-1b strain, the calves had significantly (p < 0.05) reduced viremia and clinical BVD disease compared to the calves vaccinated with a commercial killed vaccine. The Bac-E2¹²³ antigen was not as effective as the Expi293^TM-expressed antigen cocktail, but it protected calves from BVD disease better than the commercial killed vaccine. The findings support feasibility for development of a broadly protective subunit BVDV vaccine for safe and effective management of BRD.

Modelling the economics of bovine viral diarrhoea virus control in pastoral dairy and beef cattle herds

Bovine viral diarrhoea virus (BVDV) is a prevalent pathogen in the New Zealand cattle industries, yet few studies to date have evaluated the economics of BVDV in pastoral dairy and beef herds to help inform management decisions. To address this knowledge gap, we developed stochastic individual-based simulation models to represent the transmission dynamics of BVDV in typical spring-calving dairy and beef farms in New Zealand. The models conservatively estimated the direct losses due to a BVDV outbreak at NZ$ 22.22 and NZ$ 41.19 per mixed-age cow per year for a naïve dairy and beef farm, respectively, over a 5-year period. The greatest economic impacts for the dairy farm occurred when persistently infected replacement heifers joined the lactating cow group and caused transient infection of cows to drop in milk production, whereas the greatest impacts for the beef farm was through the loss of fattening stock for sale due to lowered pregnancy rates. Various combinations of diagnostic testing, vaccination, and biosecurity measures were then explored to evaluate the cost-efficiency of different strategies for controlling BVDV at the farm-level. Providing farmers with the estimates of economic impacts of BVDV in their herds may further encourage the uptake of control measures, but close collaboration with a veterinarian to determine the optimal strategy for their unique farm circumstances is still required.

Bovine viral diarrhea virus: An updated American College of Veterinary Internal Medicine consensus statement with focus on virus biology, hosts, immunosuppression, and vaccination

Control of bovine viral diarrhea virus (BVDV) in cattle populations across most of the world has remained elusive in spite of advances in knowledge about this viral pathogen. A central feature of virus perseverance in cattle herds is the unique mechanism of persistent infection. Managing BVDV infection in herds involves controlling persistently infected carrier animals using a multidimensional approach of vaccination, biosecurity, and identification of BVDV reservoirs. A decade has passed since the original American College of Veterinary Internal Medicine consensus statement on BVDV. While much has remained the same with respect to clinical signs of disease, pathogenesis of infection including persistent infection, and diagnosis, scientific articles published since 2010 have led to a greater understanding of difficulties associated with control of BVDV. This consensus statement update on BVDV presents greater focus on topics currently relevant to the biology and control of this viral pathogen of cattle, including changes in virus subpopulations, infection in heterologous hosts, immunosuppression, and vaccination.

Hydrostatic Filtration Enables Large-Scale Production of Outer Membrane Vesicles That Effectively Protect Chickens against Gallibacterium anatis

Gallibacterium anatis is a Gram-negative opportunistic avian pathogen representing an emerging threat to poultry meat and egg production worldwide. To date, no vaccine able to effectively prevent the morbidity associated with G. anatis infections has been developed yet. Our group previously reported that inoculation of different combinations of G. anatis outer membrane vesicles (OMVs), FlfA and GtxA-N proteins is effective in preventing lesions caused by G. anatis infections in layer chickens. Here we report the testing of the efficacy as vaccine prototypes of G. anatis OMVs isolated by hydrostatic filtration, a simple technique that allows the cost-effective isolation of high yields of OMVs. Layer chickens were immunized with OMVs alone or in combination with FlfA and/or GtxA-N proteins. Subsequent challenge with a heterologous G. anatis strain showed that immunization with OMVs alone could significantly reduce the lesions following a G. anatis infection. A second study was carried out to characterize the dose-response (0.25, 2.5 and 25 µg) relationship of G. anatis OMVs as immunogens, showing that 2.5 μg of OMVs represent the optimal dose to elicit protection in the immunized animals after a similar challenge. Additionally, administration of ≥2.5 μg of G. anatis OMVs induced specific IgY titers and possibly vertical transfer of immunity.

Feed Intake and Weight Changes in Bos indicus-Bos taurus Crossbred Steers Following Bovine Viral Diarrhea Virus Type 1b Challenge Under Production Conditions

Bovine viral diarrhea virus (BVDV) has major impacts on beef cattle production worldwide, but the understanding of host animal genetic influence on illness is limited. This study evaluated rectal temperature, weight change and feed intake in Bos indicus crossbred steers (n = 366) that were challenged with BVDV Type 1b, and where family lines were stratified across three vaccine treatments of modified live (MLV), killed, (KV) or no vaccine (NON). Pyrexia classification based on 40.0 °C threshold following challenge and vaccine treatment were investigated for potential interactions with sire for weight change and feed intake following challenge. Pyrexia classification affected daily feed intake (ADFI, p = 0.05), and interacted with day (p < 0.001) for ADFI. Although low incidence of clinical signs was observed, there were marked reductions in average daily gain (ADG) and cumulative feed intake during the first 14 day post-challenge; ADG (CV of 104%) and feed efficiency were highly variable in the 14-day period immediately post-challenge as compared to the subsequent 14-day periods. A sire × vaccine strategy interaction affected ADFI (p < 0.001), and a sire by time period interaction affected ADG (p = 0.03) and total feed intake (p = 0.03). This study demonstrates that different coping responses may exist across genetic lines to the same pathogen, and that subclinical BVDV infection has a measurable impact on cattle production measures.

Eradication of bovine viral diarrhea virus in Germany-Diversity of subtypes and detection of live-vaccine viruses

Bovine viral diarrhea (BVD) causes high economic losses in the cattle population worldwide. In Germany, an obligatory control program with detection and removal of persistently infected animals is in force since 2011. For molecular tracing of virus transmission, a comprehensive sequence data base of the currently circulating BVD viruses was established. Partial sequences of 1007 samples collected between 2008 and 2016 were generated. As dominant viruses, subtypes 1b (47.0%) and 1d (26.5%) could be identified with no marked geographic or sampling year effect, a much higher amount of BVDV-2c was detected in 2013 compared to other years, predominantly in Western Germany. In addition, subtypes 1a, 1e, 1f, 1h, 1g, 1k, and 2a were found. Interestingly, besides field-viruses, two different live-vaccine viruses were detected in tissue samples of newborn calves (n=37) whose mothers were immunized during pregnancy.

Selection and characterization of specific nanobody against bovine virus diarrhea virus (BVDV) E2 protein

Bovine viral diarrhea-mucosal disease (BVD-MD) is caused by bovine viral diarrhea virus (BVDV), and results in abortion, stillbirth, and fetal malformation in cows. Here, we constructed the phage display vector pCANTAB 5E-VHH and then transformed it into Escherichia coli TG1-competent cells, to construct an initial anti-BVDV nanobody gene library. We obtained a BVDV-E2 antigen epitope bait protein by prokaryotic expression using the nucleotide sequence of the E2 gene of the BVDV-NADL strain published in GenBank. Phage display was used to screen the anti-BVDV nanobody gene library. We successfully constructed a high quality phage display nanobody library, with an initial library capacity of 4.32×105. After the rescue of helper phage, the titer of the phage display nanobody library was 1.3×1011. The BVDV-E2 protein was then expressed in Escherichia coli (DE3), and a 49.5 kDa band was observed with SDS-PAGE analysis that was consistent with the expected nanobody size. Thus, we were able to isolate one nanobody that exhibits high affinity and specificity against BVDV using phage display techniques. This isolated nanobody was then used in Enzyme Linked Immunosorbent Assay and qRT-PCR, and ELISA analyses of BVDV infection of MDBK cells indicated that the nanobodies exhibited good antiviral effect.

Comparison of humoral and T-cell-mediated immune responses to a single dose of Bovela® live double deleted BVDV vaccine or to a field BVDV strain

The objective of this study was to determine and compare the humoral and cellular immune responses of calves exposed to a single dose of Bovela^® bovine viral diarrhea virus (BVDV) live double deleted vaccine or a field strain virus (FSV) of BVDV type 2 (strain 890). Thirty seronegative, colostrum-deprived 5 month-old Holstein steer calves that tested negative for persistent BVDV by ear notch immunohistochemistry and seronegative to BVDV types 1 and 2 were used. Calves were screened by multi-parameter flow cytometry (MP-FCM) 1 week before vaccination to ensure that they were negative for T cell responses to the BVDV types 1 and 2 viruses in the Bovela^® vaccine. Calves were assigned to 3 treatment groups: control (PBS), FSV inoculated, and Bovela^® vaccinated. The humoral response was tested by standard serum virus neutralization (SVN) test to BVDV types 1 (Singer strain) and 2 (strain 125). The response by CD4, CD8, and gamma delta (γδ TCR) T cells was evaluated by MP-FCM using individual BVDV types 1 and 2 from Bovela^® vaccine as recall antigens at 5, 6, and 7 weeks after vaccination. Activation markers used were upregulation of surface CD25 (IL-2R), intracellular interferon gamma (IFNγ) and intracellular interleukin 4 (IL-4). Each T cell subset was evaluated for increased expression of each activation marker compared to non-antigen stimulated cells of the same animal. All Bovela^® vaccinated and FSV inoculated calves produced SVN antibodies to both BVDV types 1 and 2 while control animals remained seronegative throughout the study. The mean (weeks 5, 6, and 7) T cell recall responses to Bovela^® BVDV type 1 and type 2 recall antigens were numerically higher in all three T cell subsets (CD4, CD8, and γδ TCR) for all three activation markers (CD25, IFNγ, and IL-4) when compared to either the control animals or to the FSV inoculated animals. These differences were often, but not always, statistically significant (P<0.05).