Safety, immunogenicity and duration of immunity elicited by an inactivated bovine ephemeral fever vaccine

Development of two competitive ELISAs based on monoclonal antibodies for the serological detection of Bovine ephemeral fever virus

Bovine ephemeral fever virus (BEFV) is a member of the genus Ephemerovirus in the family Rhabdoviridae. It is an arthropod-borne virus transmitted by many species of midges and mosquitoes. It can cause severe economic consequences due to losses in milk production and the general condition of cattle and water buffalo. BEF occurs in some tropical, subtropical and warm temperate regions of Africa, Australia, the Middle East and Asia with seasonal outbreaks, but its possible spread to other areas (e.g. Europe) cannot be excluded. Therefore, using and developing rapid diagnostic methods with optimal performance is essential for identifying emerging pathogens and their control. In the present study, we developed two competitive serological ELISAs based on monoclonal antibodies (mAbs), designed by using BEFV inactivated antigen and the BEF recombinant nucleoprotein (N), respectively. A panel of 77 BEF-positive and 338 BEF-negative sera was used to evaluate the two tests. With a diagnostic sensitivity of 97.4 % using the inactivated virus and 98.7 % using the recombinant N, and a diagnostic specificity of 100 % using both antigens, our results suggest that these tests are suitable for the serological diagnosis of BEF.

Bovine Ephemeral Fever Viruses in Israel 2014-2023: Genetic Characterization of Local and Emerging Strains

Bovine ephemeral fever (BEF) is an arthropod-borne viral disease, which frequently causes significant epizootics in susceptible water buffalo and cattle in Africa, Australia, Asia and the Middle East. In the current study, a two-stage protocol for BEFV viral isolation was developed. Data on the clinical signs, geographic distribution and phylogenetic analysis of BEFV strains isolated in Israel in 2015, 2018, 2021 and 2023 were summarized. It was found that during 2015-2021, all BEF outbreaks were caused by local BEFV strains, whereas the epizootic of BEFV in 2023 was caused by a new "Mayotte-like" BEFV strain. A comparison of bluetongue (BT) and BEF outbreaks during 2023 in Israel demonstrated that the incidence of BEFV was 2.21 times higher and its pathogenicity was more serious for the cattle population compared to that caused by BTVs. A phylogenetic analysis of Israeli and global BEFV revealed the emergence of non-local strains in new areas. This finding suggests that BEFV can no longer be classified based only upon geographic distribution. Considering a phylogenetic, genetic and proteomic analysis of all available BEFV strains, we suggest classifying them as a single serotype, which includes four lineages.

The combination of vaccines and adjuvants to prevent the occurrence of high incidence of infectious diseases in bovine

As the global population grows, the demand for beef and dairy products is also increasing. The cattle industry is facing tremendous pressures and challenges. The expanding cattle industry has led to an increased risk of disease in cattle. These diseases not only cause economic losses but also pose threats to public health and safety. Hence, ensuring the health of cattle is crucial. Vaccination is one of the most economical and effective methods of preventing bovine infectious diseases. However, there are fewer comprehensive reviews of bovine vaccines available. In addition, the variable nature of bovine infectious diseases will result in weakened or even ineffective immune protection from existing vaccines. This shows that it is crucial to improve overall awareness of bovine vaccines. Adjuvants, which are crucial constituents of vaccines, have a significant role in enhancing vaccine response. This review aims to present the latest advances in bovine vaccines mainly including types of bovine vaccines, current status of development of commonly used vaccines, and vaccine adjuvants. In addition, this review highlights the main challenges and outstanding problems of bovine vaccines and adjuvants in the field of research and applications. This review provides a theoretical and practical basis for the eradication of global bovine infectious diseases.

Effectiveness of the strain 919 bovine ephemeral fever virus vaccine in the face of a real-world outbreak: A field study in Israeli dairy herds

Bovine ephemeral fever virus (BEFV) is a globally spread arthropod-borne RNA virus that has significant economic impacts on the cattle industry. A live attenuated commercial BEF vaccine, based on the Australian BEFV strain 919, is widely used in Israel and other countries. A previous study has suggested the high effectiveness of this vaccine (ULTRAVAC BEF VACCINE™ from Zoetis®), but anecdotal reports of high BEF morbidity among vaccinated dairy herds in Israel casted doubt on these findings. To resolve this uncertainty, a randomized controlled field vaccine effectiveness study was conducted in Israel during a BEF outbreak which occurred in 2021. Eleven dairy herds were enrolled and monitored for BEF-associated morbidity and rumination alteration patterns using electronic monitoring tags (HR Tags, SCR® Dairy, Netanya, Israel). Four of the herds were naturally infected with BEFV during the outbreak, resulting in a total of 120 vaccinated and 311 unvaccinated subjects that were included in the effectiveness study. A mixed-effect Cox proportional hazard regression model was used to calculate the overall hazard ratio between vaccinated and unvaccinated cattle. This analysis demonstrated an average vaccine effectiveness of 60 % (95 % CI = 38 %-77 %) for preventing clinical disease. In addition, a non-statistically significant trend (p = 0.1) towards protection from mortality was observed, with no observation of mortality among the vaccinated groups compared to 2.61 % mortality (7/311) among the unvaccinated subjects. One hundred and thirty vaccinated and unvaccinated calves from affected and non-affected herds and with different status of morbidity were sampled and analysed by serum-neutralization test. The highest titers of BEFV-neutralizing antibodies were found in subjects that were both vaccinated and clinically affected, indicating a booster effect after vaccination. The results of the study provide evidence for the moderate effectiveness of the ULTRAVAC BEF VACCINE™ for the prevention of BEF.

Duration of Immunity Induced after Vaccination of Cattle with a Live Attenuated or Inactivated Lumpy Skin Disease Virus Vaccine

Vaccines have proven themselves as an efficient way to control and eradicate lumpy skin disease (LSD). In addition to the safety and efficacy aspects, it is important to know the duration for which the vaccines confer protective immunity, as this impacts the design of an efficient control and eradication program. We evaluated the duration of immunity induced by a live attenuated vaccine (LSDV LAV) and an inactivated vaccine (LSDV Inac), both based on LSDV. Cattle were vaccinated and challenged after 6, 12 and 18 months for LSDV LAV or after 6 and 12 months for the LSDV Inac. The LSDV LAV elicited a strong immune response and protection for up to 18 months, as no clinical signs or viremia could be observed after a viral LSDV challenge in any of the vaccinated animals. A good immune response and protection were similarly seen for the LSDV Inac after 6 months. However, two animals developed clinical signs and viremia when challenged after 12 months. In conclusion, our data support the annual booster vaccination when using the live attenuated vaccine, as recommended by the manufacturer, which could potentially even be prolonged. In contrast, a bi-annual vaccination seems necessary when using the inactivated vaccine.

Evaluation of antibody response to inactivated bovine ephemeral fever virus vaccine for Japanese Black calves in the field

The purpose of this study was to investigate the antibody response to the bovine ephemeral fever virus (BEFV) vaccine in Japanese Black calves. Twenty-eight Japanese Black calves, which were raised on an ordinal farm, were divided into two groups. Fifteen calves received the inactivated BEFV vaccine at 12 and 16 weeks of age (vaccination group), and 13 calves did not receive the vaccine (non-vaccination group). Blood samples were obtained at 0, 4, 8, 12, 16, 20, 24, 28, and 32 weeks of age. As the results, in the vaccination group, the antibody titers at 16, 20, 24, 28, and 32 weeks of age were significantly higher than those at 0, 4, 8, and 12 weeks of age (p < 0.01). Additionally, antibody titer in the vaccination group increased after 16 weeks of age and showed a significantly higher level than that in the non-vaccination group throughout the remaining experimental period (p < 0.01). These results might be helpful in establishing a vaccination program against BEFV in calves.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

Epizootic congenital abnormalities caused by Akabane, Aino, and Chuzan viruses have damaged the reproduction of domestic ruminants in East Asia for many years. In the past, large outbreaks of febrile illness related to bovine ephemeral fever and Ibaraki viruses severely affected the cattle industry in that region. In recent years, vaccines against these viruses have reduced the occurrence of diseases, although the viruses are still circulating and have occasionally caused sporadic and small-scaled epidemics. Over a long-term monitoring period, many arboviruses other than the above-mentioned viruses have been isolated from cattle and Culicoides biting midges in Japan. Several novel arboviruses that may infect ruminants (e.g., mosquito- and tick-borne arboviruses) were recently reported in mainland China based on extensive surveillance. It is noteworthy that some are suspected of being associated with cattle diseases. Malformed calves exposed to an intrauterine infection with orthobunyaviruses (e.g., Peaton and Shamonda viruses) have been observed. Epizootic hemorrhagic disease virus serotype 6 caused a sudden outbreak of hemorrhagic disease in cattle in Japan. Unfortunately, the pathogenicity of many other viruses in ruminants has been uncertain, although these viruses potentially affect livestock production. As global transportation grows, the risk of an accidental incursion of arboviruses is likely to increase in previously non-endemic areas. Global warming will also certainly affect the distribution and active period of vectors, and thus the range of virus spreads will expand to higher-latitude regions. To prevent anticipated damages to the livestock industry, the monitoring system for arboviral circulation and incursion should be strengthened; moreover, the sharing of information and preventive strategies will be essential in East Asia.

Adjuvants: What a Difference 15 Years Makes!

Vaccination is a critical tool in modern animal production and key to maintaining animal health. Adjuvants affect the immune response by increasing the rate, quantity, or quality of the protective response generated by the target antigens. Although adjuvant technology dates back to the nineteenth century, there was relatively little improvement in adjuvant technology before the late twentieth century. With the discovery of molecular pathways that regulate the timing, quantity, and quality of the immune response, new technologies are focused on bringing safer, more effective, and inexpensive adjuvants to commercial use.

Immunogenicity and protective efficacy of recombinant proteins consisting of multiple epitopes of foot-and-mouth disease virus fused with flagellin

Many recent studies have shown that flagellin fused to heterologous antigens can induce significantly enhanced humoral and cellular immune responses through its adjuvant activity. Therefore, in this study, two key B cell epitopes and a truncated VP1 (ΔVP1) protein from foot-and-mouth disease virus (FMDV) were expressed as flagellin fusion proteins in different patterns. Specifically, ΔVP1 and two duplicates of two key B cell epitopes (2×B1B2) were fused separately to the C-terminus of flagellin with a universal exogenous T cell epitope to construct FT (Flagellin-Truncated VP1) and FME (Flagellin-Multiple Epitopes). In addition, the D3 domain of flagellin was replaced by ΔVP1 in FME, yielding FTME (Flagellin-Truncated VP1-Multiple Epitopes). The immunogenicity and protective efficacy of the three fusion proteins as novel FMDV vaccine candidates were evaluated. The results showed that FT, FME, and FTME elicited significant FMDV-specific IgG responses at 10 μg/dose compared with the mock group (P < 0.05), with FTME producing the highest response. No significant differences in the antibody response to FTME were observed between different immunization routes or among adjuvants (ISA-206, poly(I·C), MPLA, and CpG-ODN) in mice. In addition, at 30 μg/dose, all three fusion proteins significantly induced neutralizing antibody production and upregulated the levels of some cytokines, including TNF-α, IFN-γ, and IL-12, in guinea pigs. Importantly, all three fusion proteins provided effective protective immunity against FMDV challenge in guinea pigs, though different protection rates were found. The results presented in this study indicate that the FTME fusion protein is a promising novel vaccine candidate for the future prevention and control of foot-and-mouth disease.

Immunogenicity of a plasmid DNA vaccine encoding G1 epitope of bovine ephemeral fever virus G glycoprotein in mice

The aim of this study was to investigate the immunogenicity of a plasmid deoxyribonucleic acid (DNA) vaccine encoding the G1 epitope of bovine ephemeral fever virus (BEFV) G glycoprotein in mice. A plasmid DNA carrying the G1 gene was constructed and designated as pcDNA3.1-G1. The expression of the target gene was confirmed in human embryonic kidney 293 (HEK 293) cells transfected with pcDNA3.1-G1 by indirect immunofluorescent staining. Immunisation experiments were intramuscularly carried out by vaccinating 6-week-old female mice in four groups, including the pcDNA3.1-G1 construct, pcDNA3.1 (+) plasmid alone, BEF-inactivated vaccine and phosphate-buffered saline (PBS) (1X) three times with 2-week intervals. Fourteen days after the last immunisation, the animals were bled and the resulting sera were tested for anti-G1-specific antibodies by immunoblotting analysis, indirect enzyme-linked immunosorbent assay (ELISA) and virus neutralisation (VN) test. Serological assays showed that the pcDNA3.1-G1 construct expressing G1 protein was able to elicit specific antibodies against this antigen. Virus neutralisation test showed that pcDNA3.1-G1 could induce anti-BEFV-neutralising antibodies in mice. Our findings indicated that a new dimension can be added to vaccine studies for bovine ephemeral fever (BEF) using eukaryotic expression plasmids encoding the G1 antigen in the future.

The serological response against foot and mouth disease virus elicited by repeated vaccination of dairy cattle

In Israel, cattle are annually vaccinated against foot and mouth disease (FMD). If infections with FMD virus occur in dairy farms it mainly involves heifers and calves, while older dairy cows seldom become infected. We hypothesized that this difference in susceptibility between adult cows and the young heifers and calves is due to stronger and more stable immune response elicited by multiple vaccinations. In order to test this hypothesis, 99 dairy cattle, divided into six groups according to number of prior vaccinations, were annually vaccinated with a trivalent vaccine (A, O and Asia-1) and followed during two consecutive years. In total 988 sera were sampled at 11 time points. Virus neutralization tests (VNT) were performed in order to determine the neutralizing antibody titers (NAT) against the vaccine homologous serotypes: O-4625, O-Manisa, Asia-1-Shamir and the heterologous serotype A-Turkey-20/2006. A similar NAT pattern was observed to all serotypes and therefore statistical analysis was restricted to O-4625 serotype. In the 'high vaccination' groups (cows that were vaccinated at least four times before the study), high NAT were found on the beginning of the trial and no or only a mild increase of NAT was observed following further vaccinations. Additionally, in the 'high vaccination' groups, the percentage of cows that had a NAT higher than 2.0 (log10) by the end of the 1st year was significantly higher than in the 'low vaccination' groups (cows vaccinated only three times or less before the study). We conclude that starting from the 5th vaccination, the NAT increase following vaccination is mild and NAT are persistent, suggesting reduction of the frequency of routine vaccination after multiple vaccinations is possible.

Kinetics of selected plasma cytokines during innate-adaptive immune response transition in adult cattle infected with the bovine ephemeral fever virus

While virus neutralizing antibodies are known to be variably protective against bovine ephemeral fever (BEF) virus (BEFV) infections, the cytokine events that mediate the nascent adaptive immune response have not been defined in cattle. This study determined the plasma kinetics of IL-2, IFN-γ, IL-6, and IL-10 during the period of innate-immune response transition and evaluated the relationship between the virus neutralizing antibody response and viraemia in BEFV-infected cattle. Plasma from four virus-infected and uninfected negative control animals was tested by cytokine-specific immunoenzymatic assays, viraemia monitored by qRT-PCR, and virus neutralizing antibody titres determined using a standard protocol. Unlike the negative controls, plasma IL-6 and IL-10 were increased in all the virus-infected animals starting several days prior to initiation of viraemia. In one animal, plasma IL-2 and IFN-γ were consistently higher than in the other three virus-infected animals and the negative control mean. The animal with the strongest IL-2 and IFN-γ responses had the shortest viraemia while the heifer with the lowest IL-2/IFN-γ indices demonstrated the longest viraemia. Evidently, increase in plasma IL-6 and IL-10 precedes seroconversion during BEFV infections in cattle suggesting the two cytokines may influence immunological events that pave way to B-cell activation and seroconversion. While there is remarkable variability in IL-2 and IFN-γ expression amongst BEFV-infected animals, increased plasma levels of the two cytokines appear to be associated with a shorter viraemia. Ongoing studies will help define the precise role of T cells in anti-BEFV adaptive immune responses.

Experimental infection with bovine ephemeral fever virus and analysis of its antibody response cattle

Bovine ephemeral fever (BEF) is an arthropod-borne viral disease that occurs throughout mainland China. LS11 obtained in the 2011 BEF epidemic was a wild strain, and its virulence and antibody response have never been studied in China. Therefore, the issues were investigated in this work. Experimental cattle were intravenously infected with different doses of BEF virus, and some non-infected cattle were simultaneously monitored. Blood and serum samples were collected from all animals over the course of our study. Infected cattle were challenged for a second time with BEF virus to determine protective period of the antibodies. BEF virus was detected in blood samples from infected cattle, but not in monitored cattle. The neutralizing antibodies (nAbs) against BEFV were easier to be detected and persisted for longer periods in cattle infected with higher doses of BEFV than in those infected with lower doses. When the titer of nAbs was equal to 5 or 6, re-infected cattle still could mount a challenge against BEFV. However, after 3 or 6months, when nAbs were no longer apparent, re-infected cattle displayed typical symptoms of BEF. Our findings indicated that vaccination should be performed once the titer of nAb decreased to 5 or 6.

Epidemiology and control of bovine ephemeral fever

Bovine ephemeral fever (or 3-day sickness) is an acute febrile illness of cattle and water buffaloes. Caused by an arthropod-borne rhabdovirus, bovine ephemeral fever virus (BEFV), the disease occurs seasonally over a vast expanse of the globe encompassing much of Africa, the Middle East, Asia and Australia. Although mortality rates are typically low, infection prevalence and morbidity rates during outbreaks are often very high, causing serious economic impacts through loss of milk production, poor cattle condition at sale and loss of traction power at harvest. There are also significant impacts on trade to regions in which the disease does not occur, including the Americas and most of Europe. In recent years, unusually severe outbreaks of bovine ephemeral fever have been reported from several regions in Asia and the Middle East, with mortality rates through disease or culling in excess of 10–20%. There are also concerns that, like other vector-borne diseases of livestock, the geographic distribution of bovine ephemeral fever could expand into regions that have historically been free of the disease. Here, we review current knowledge of the virus, including its molecular and antigenic structure, and the epidemiology of the disease across its entire geographic range. We also discuss the effectiveness of vaccination and other strategies to prevent or control infection.

Kinetics of pro-inflammatory cytokines, interleukin-10, and virus neutralising antibodies during acute ephemeral fever virus infections in Brahman cattle

While fever and inflammation are hallmark features of bovine ephemeral fever (BEF), the cytokine networks that underlie the acute phase of the disease have not been empirically defined in cattle. This study characterised the plasma kinetics of proinflammatory cytokines (IL-1β, IL-6, TNF-α) and IL-10 during acute BEF and elucidated on the relationship between the onset of the virus neutralizing antibody response and resolution of viraemia in natural BEF virus (BEFV) infections in cattle. Plasma from three BEFV-infected and three uninfected cattle was tested for the study cytokines by a cELISA, viraemia monitored by qRT-PCR, and virus neutralizing antibody titres determined using a standard protocol. Unlike the negative controls, plasma concentrations of IL-1β, TNF-α, IL-6, and IL-10 were consistently increased in the three virus-infected animals. Two of the infected heifers were recumbent and pyrexic on the first day of monitoring and increased cytokine production was already in progress by the time viraemia was detected in all the three infected animals. In all the virus-infected heifers, IL-1β was the most strongly expressed cytokine, IL-6 and IL-10 manifested intermediate plasma concentrations while TNF-α was the least expressed and demonstrated bi-phasic peaks three and five days after the onset of pyrexia. In two of the BEFV-infected heifers, viraemia resolved on the day of seroconversion while in the other infected animal, viral RNA was detectable up to three days after seroconversion. The present data document variable increase in plasma IL-1β, IL-6, TNF-α, and IL-10 during natural BEFV infections and the fact that upregulation of all but TNF-α precedes seroconversion. In addition to virus neutralising antibodies, it is likely that cytokine-mediated cellular mechanisms may be required for resolution of viraemia in BEF. Considering the anti-inflammatory properties of IL-10, its upregulation may potentially antagonise the fever response in BEFV-infected cattle.