Comparative evaluation of lumpy skin disease virus-based live atenuated vaccines

Vaccines form the cornerstone of any control, eradication and preventative strategy and this is no different for lumpy skin disease. However, the usefulness of a vaccine is determined by a multiplicity of factors which include stability, efficiency, safety and ease of use, to name a few. Although the vaccination campaign in the Balkans against lumpy skin disease virus (LSDV) was successful and has been implemented with success in the past in other countries, data of vaccine failure have also been reported. It was therefore the purpose of this study to compare five homologous live attenuated LSDV vaccines (LSDV LAV) in a standardized setting. All five LSDV LAVs studied were able to protect against a challenge with virulent LSDV. Aside from small differences in serological responses, important differences were seen in side effects such as a local reaction and a Neethling response upon vaccination between the analyzed vaccines. These observations can have important implications in the applicability in the field for some of these LSDV LAVs.The Bill & Melinda Gates Foundation, the GALVmed project Nr CAO-R34A0856 on lumpy skin disease and the Belgian Federal Public Service of Health, Food Chain Safety and Environment through the contract RT 15/3 (LUMPY SKIN 1).http://www.mdpi.com/journal/vaccinespm2022Veterinary Tropical Disease

Virulence comparison and quantification of horizontal bovine viral diarrhoea virus transmission following experimental infection in calves

&lt;p&gt;Bovine viral diarrhoea virus (BVDV) causes persistent infections by infecting the fetus of susceptible animals during gestation. These persistently infected (PI) animals are important sources of infection. On the contrary, transiently infected (TI) animals are believed to be less important, but transient infections with a severe BVDV-2 strain can spread explosively. To assess the importance of TI cattle in the epidemiology of BVDV, two experimental infections were performed to determine basic reproduction ratios (R0). In each experiment three calves were infected via intranasal inoculation and housed together with seven susceptible animals. Two strains isolated in Belgium were used, a virulent BVDV-1b and a virulent BVDV-2a field isolate, resulting in an R0 of 0.25 (95% CI 0.01; 1.95) and 0.24 (95% CI 0.01; 2.11), respectively. A PI animal was then introduced to the remaining uninfected animals and produced an R of +∞ (95% CI 1.88; +∞). These results support the suggestion that TI animals, compared to PI animals, contribute only a limited amount to BVDV spread. Additionally, the severe clinical symptoms observed in the field with these isolates could not be reproduced during these experiments, suggesting that other factors besides strain virulence influence the clinical manifestations evoked by BVDV.&lt;/p&gt;</p

Age- and strain-dependent differences in the outcome of experimental infections of domestic pigs with wild boar pseudorabies virus isolates

Although pseudorabies virus (PRV) has been eradicated in domestic swine in many countries, its presence in wild boars remains a threat for a reintroduction into the currently unprotected swine population. To assess the possible impact of such a reintroduction in a naive herd, an in vivo infection study using two genetically characterized wild boar PRV isolates (BEL24043 and BEL20075) representative for wild boar strains circulating in south-western and central Europe and the virulent NIA3 reference strain was performed in 2- and 15-week-old domestic pigs. Our study revealed an attenuated nature of both wild boar strains in 15-week-old pigs. In contrast, it showed the capacity of strain BEL24043 to induce severe clinical symptoms and mortality in young piglets, thereby confirming that the known age dependency of disease outcome after PRV infection also holds for wild boar isolates. Despite the absence of clinical disease in 15-week-old sows, both wild boar PRV strains were able to induce seroconversion, but to a different extent. Importantly, differences in infection and transmission capacity of both strains were observed in 15-week-old sows. Strain BEL24043 induced a more prolonged and disseminated infection than strain BEL20075 and was able to spread efficiently to contact animals, indicative of its capacity to induce a sustained infection. In conclusion, it was shown that a reintroduction of a wild boar isolate into the domestic swine population could have serious economic consequences due to the induction of clinical symptoms in piglets and by jeopardizing the PRV-negative status

Towards the development of an effective vaccine against malignant catarrhal fever

peer reviewedAlcelaphine herpesvirus 1 (AlHV-1) persists in wildebeest asymptomatically but induces malignant catarrhal fever (MCF), a fatal lymphoproliferative disease upon transmission to several ruminants, including cattle. The significant socio-economic impact of MCF in East-Africa urges for the development of new vaccination strategies. We have previously shown using the experimental rabbit model that the latency-associated gene ORF73 was essential for MCF induction while a ORF73-deficient (ORF73−) strain C500 could induce sterile immunity against a wild-type (WT) challenge. In the present study, we first infected 4-month-old calves with WT or ORF73− virus. Intranasal infection with the WT virus induced typical MCF clinical signs and lesions. However, ORF73− virus did not cause any clinical sign but induced a complete protection against an intranasal challenge with the WT virus. These results were encouraging for future prospects of vaccination against MCF. However, AlHV-1 is highly cell-associated and viral titres remain low, potentially hampering effective vaccine production. Interestingly, attenuated strain WC11 of AlHV-1 displays increased viral growth and cell-free infectious particles. Whole-genome sequencing of strain WC11 revealed few genomic changes including full deletion of the gene A7. A7 is a positional homolog of Epstein-Barr virus (EBV) BZLF2 encoding the C-type lectin-like glycoprotein gp42. Gp42 is expressed in the envelope of EBV virions and mediates entry into B cells. Hence, we used the C500 BAC clone to generate an A7STOP recombinant strain. We observed that a lack of A7 expression resulted in significant increased viral growth in fibroblasts in vitro. Also, the plaque size over time and the morphology of the plaques were modified in absence of A7. Finally, infection of rabbits demonstrated that A7 is essential for the development of MCF. In conclusion, the lack of A7 significantly alters the replication of the virus in vitro and the development of MCF in rabbits. Thus, joined impairments of A7 and ORF73 could lead to an optimized vaccine

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

Wildebeest-Derived Malignant Catarrhal Fever: A Bovine Peripheral T Cell Lymphoma Caused by Cross-Species Transmission of <i>Alcelaphine Gammaherpesvirus 1</i>

Gammaherpesviruses (γHVs) include viruses that can induce lymphoproliferative diseases and tumors. These viruses can persist in the long term in the absence of any pathological manifestation in their natural host. Alcelaphine gammaherpesvirus 1 (AlHV-1) belongs to the genus Macavirus and asymptomatically infects its natural host, the wildebeest (Connochaetes spp.). However, when transmitted to several susceptible species belonging to the order Artiodactyla, AlHV-1 is responsible for the induction of a lethal lymphoproliferative disease, named wildebeest-derived malignant catarrhal fever (WD-MCF). Understanding the pathogenic mechanisms responsible for the induction of WD-MCF is important to better control the risks of transmission and disease development in susceptible species. The aim of this review is to synthesize the current knowledge on WD-MCF with a particular focus on the mechanisms by which AlHV-1 induces the disease. We discuss the potential mechanisms of pathogenesis from viral entry into the host to the maintenance of viral genomes in infected CD8+ T lymphocytes, and we present current hypotheses to explain how AlHV-1 infection induces a peripheral T cell lymphoma-like disease

Evidence of Lumpy Skin Disease Virus Transmission from Subclinically Infected Cattle by <i>Stomoxys calcitrans</i>

Lumpy skin disease virus (LSDV) is a vector-transmitted capripox virus that causes disease in cattle. Stomoxys calcitrans flies are considered to be important vectors as they are able to transmit viruses from cattle with the typical LSDV skin nodules to naive cattle. No conclusive data are, however, available concerning the role of subclinically or preclinically infected cattle in virus transmission. Therefore, an in vivo transmission study with 13 donors, experimentally inoculated with LSDV, and 13 naïve acceptor bulls was performed whereby S. calcitrans flies were fed on either subclinical- or preclinical-infected donor animals. Transmission of LSDV from subclinical donors showing proof of productive virus replication but without formation of skin nodules was demonstrated in two out of five acceptor animals, while no transmission was seen from preclinical donors that developed nodules after Stomoxys calcitrans flies had fed. Interestingly, one of the acceptor animals which became infected developed a subclinical form of the disease. Our results show that subclinical animals can contribute to virus transmission. Therefore, stamping out only clinically diseased LSDV-infected cattle could be insufficient to completely halt the spread and control of the disease

RNA-seq analysis of latently-infected CD8+ T lymphocytes during bovine malignant catarrhal fever reveals unconventional TCR cell activation

peer reviewedAlcelaphine herpesvirus 1 (AlHV-1) persists in wildebeest asymptomatically but induces malignant catarrhal fever (MCF) upon transmission to other ruminant species, including cattle. We have previously shown that MCF is a lethal disease resembling a peripheral T cell lymphoma (PTCL) and induced after ORF73-dependent latency establishment in CD8+ T lymphocytes. However, how AlHV-1 infection leads to CD8+ T lymphocyte proliferation and activation remains largely unknown. In this study, we investigated viral and cellular transcriptomes of bovine CD8+ T lymphocytes during MCF. Three groups of four 4-month-old calves were mock-infected or infected intranasally with 105 PFU of the virulent C500 wildtype (WT) strain or non-pathogenic ORF73-deficient (73null) AlHV-1 strain. At day 45 after infection (mock and 73null groups) or at time of MCF development (WT group), CD8+ T lymphocytes were isolated from peripheral blood to high purity before RNA extraction. Illumina Truseq stranded mRNA libraries were obtained and subjected to NextSeq500 sequencing. Transcriptomes were analysed for both viral and cellular transcripts. We took advantage of the non-pathogenic 73null strain to differentiate anti-viral effector/memory responses in CD8+ T cells from transcriptomics changes due to latent infection of these cells during MCF. While no viral transcripts could be detected in CD8+ T cells of mock or 73null-infected animals, expression of viral genes of interest in MCF-developing calves was detected including AlHV-1-specific semaphorin-like A3, undefined A4, bZIP protein A6, interleukin 4-like protein A9.5 and undefined glycoprotein A10. When analysing differential cellular gene expression (P < 10−4; change in expression of over fourfold), we observed upregulation of 151 (WT vs Mock) and 72 (WT vs 73null) genes, including Gzma, SerpinB9, Moxd1, Tox2, IL-10, and Cxcr3; and downregulation of 205 (WT vs Mock) and 271 (WT vs 73null) genes, including αv or β3 integrins. Intriguingly, while gene-set enrichment for TCR engagement was observed in CD8+ T cells from MCF-developing calves, supporting T cell activation, we also observed strong downregulation of gene transcripts normally involved in canonical TCR activation such as Cbl, Tec family tyrosine kinases Rlk, Tec, and Itk, and Syk. These data suggest unconventional TCR triggering and provide unprecedented mechanistic insights on how AlHV-1 could induce a PTCL-like disease. Future work should further determine the actual pathway(s) involved and which viral gene(s) drive T cell dysregulation

Evaluation of mycobacteria-specific gamma interferon and antibody responses before and after a single intradermal skin test in cattle naturally exposed to M-avium subsp paratuberculosis and experimentally infected with M-bovis

International audienceThis study reports on the diagnostic potential of IFN-gamma release assays and serology for Mycobacterium bovis in six naturally M. avium subsp. paratuberculosis (Map) exposed bulls of which four were intratracheally infected with a Belgian field strain of M. bovis. Heparinized blood, serum and fecal samples were collected at regular time intervals for mycobacteria-specific IFN-gamma release assays, antibody analysis and for Map culture respectively. Single intradermal skin test (SIT) with bovine tuberculin (PPD-B) was performed on day 115 and animals were sacrificed on day 133 after M. bovis infection. Organs were collected and stored for histopathological examination, modified Ziehl-Neelsen staining and bacteriological analysis of M. bovis and Map by culture and RT-PCR. Prior to infection five animals showed positive IFN-gamma responses to avian PPD (PPD-A) and four were positive in Map PCR (1S900) on faeces. Three M. bovis infected animals reacted as early as day 14 with sustained higher PPD-B than PPD-A specific IFN-gamma responses, whereas the fourth animal (with the strongest PPD-A response prior to infection) showed sustained higher PPD-B specific IFN-gamma levels only a day 56 after infection. Two of the infected animals had a sustained positive IFN-y response to the ESAT-6/CFP-10/TB7.7 (QuantiFERON(.)-TB Gold) peptide cocktail as early as day 14, among which the animal with the initial high PPD-A response. Later during infection, positive responses were found to ESAT-6 peptides in three infected bulls and to CFP-10 peptides in all four infected bulls. One of the control animals reacted intermittently to the ESAT-6/CFP10/TB7.7 cocktail. Prior to SIT, weak but positive MPB83/MBP70 specific antibody responses were detected in two of the infected bulls. All four M. bovis infected bulls reacted with a positive skin test and showed, as reported by others, increased mycobacteria specific IFN-gamma production and increased positive responses in MPB83/MBP70 specific serology after SIT. At autopsy, M. bovis lesions were detected in all four experimentally infected bulls. Our results indicate that in Map exposed cattle, M. bovis diagnosis using IFN-gamma assays needs a combination of PPD-B/A and ESAT-6/CFP10 for early and optimal sensitivity and that sensitivity of MPB83/MBP70 serodiagnosis is dramatically increased by prior skin testing. Map exposure did not interfere with the development of SIT in M. bovis infected animals, but resulted in a false positive M. bovis specific IFN-gamma and antibody response after SIT in one of the two control animals (which remained negative in skin-test)