Comparative evaluation of lumpy skin disease virus-based live attenuated 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

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

Japanese Encephalitis virus persistence in porcine tonsils is associated with a weak induction of the innate immune response, an absence of IFN gamma mRNA expression, and a decreased frequency of CD4+CD8+ double-positive T cells

In humans, Japanese encephalitis virus (JEV) causes a devastating neurotropic disease with high mortality, whereas in pigs, the virus only causes mild symptoms. Besides tropism to the central nervous system, JEV seems to harbor a particular tropism for the tonsils in pigs. This secondary lymphoid organ appears to act as a reservoir for the virus, and we show that it is found up to 21 days post infection at high viral titers. The immune response in the tonsils was studied over time upon intradermal inoculation of pigs. Entry of the virus in the tonsils was accompanied by a significant increase in anti-viral OAS1 and IFN beta mRNA expression. This limited antiviral response was, however, not sufficient to stop JEV replication, and importantly, no IFN gamma or innate inflammatory cytokine mRNA expression could be observed. Strikingly, the persistence of JEV in tonsils was also associated with a significant decreased frequency of CD4(+)CD8(+) double-positive T lymphocytes. Furthermore, it is important to note that JEV persistence in tonsils occurred despite a strong induction of the adaptive immune response. JEV-specific antibodies were found after 6 days post infection in serum, and cell-mediated immune responses upon NS3 restimulation of PBMCs from experimentally infected pigs showed that CD4(+)CD8(+) double-positive T cells were found to display the most prominent proliferation and IFN gamma production among lymphocyte subtypes. Taken together, these results suggest that an inadequate induction of the innate immune response and the absence of an IFN gamma antiviral response contribute to the persistence of JEV in the tonsils and is associated with a decrease in the frequency of CD4(+)CD8(+) double-positive T cells

Efficient control of Japanese encephalitis virus in the central nervous system of infected pigs occurs in the absence of a pronounced inflammatory immune response

BACKGROUND: Japanese encephalitis virus (JEV) is the leading cause of viral encephalitis in Asia. JEV infection of mice and humans can lead to an uncontrolled inflammatory response in the central nervous system (CNS), resulting in a detrimental outcome. Pigs act as important amplification and reservoir hosts, and JEV infection of pigs is mostly subclinical. Information on virus spread in the CNS and immune responses controlling JEV infection in the CNS of pigs, however remains scarce. METHODS: Nine-week-old pigs were inoculated intranasal or intradermal with a relevant dose of 105 TCID50 of JEV genotype 3 Nakayama strain. Clinical signs were assessed daily, and viral spread was followed by RT-qPCR. mRNA expression profiles were determined to study immune responses in the CNS. RESULTS: Besides a delay of 2 days to reach the peak viremia upon intranasal compared to intradermal inoculation, the overall virus spread via both inoculation routes was highly similar. JEV appearance in lymphoid and visceral organs was in line with a blood-borne JEV dissemination. JEV showed a particular tropism to the CNS but without the induction of neurological signs. JEV entry in the CNS probably occurred via different hematogenous and neuronal pathways, but replication in the brain was mostly efficiently suppressed and associated with a type I IFN-independent activation of OAS1 expression. In the olfactory bulb and thalamus, where JEV replication was not completely controlled by this mechanism, a short but strong induction of chemokine gene expression was detected. An increased IFNy expression was simultaneously observed, probably originating from infiltrating T cells, correlating with a fast suppression of JEV replication. The chemokine response was however not associated with the induction of a strong inflammatory response, nor was an induction of the NLRP3 inflammasome observed. CONCLUSIONS: These findings indicate that an adequate antiviral response and an attenuated inflammatory response contribute to a favorable outcome of JEV infection in pigs and help to explain the limited neurological disease compared to other hosts. We show that the NLRP3 inflammasome, a key mediator of neurologic disease in mice, is not upregulated in pigs, further supporting its important role in JEV infections.status: publishe

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

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

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

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

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

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