TA novel HRM-based gap-qRT-PCR for identification and quantitation of the vaccine and field strain(s) of lumpy skin disease virus

Pathogenicity and virulence of lumpy skin disease virus: A comprehensive update

Lumpy skin disease (LSD), which was confined to the Africa for many decades, has expanded its geographical distribution to numerous countries across Asia and Europe in recent years. The LSD virus (LSDV) is a relatively poorly studied virus. Its 151 Kb genome encodes 156 open reading frames (ORF); however, the exact number of the proteins encoded by the viral genome and their specific functions remain largely unknown. Arthropod vectors primarily transmit the LSDV mechanically, but the precise nature of these vectors in different regions and their role in transmission is not fully understood. Homologous live-attenuated vaccines prepared using LSDV have proven to be highly efficacious compared to heterologous vaccines based on sheep pox virus or goatpox virus, in protecting cattle against LSD. This review offers the latest insights into the molecular biology and transmission of LSDV and discusses the safety and efficacy of available vaccines, along with the challenges faced in controlling and eradicating the disease in endemic regions.

Progress in diagnostic methods and vaccines for lumpy skin disease virus: a path towards understanding the disease

Lumpy skin disease (LSD) is caused by Lumpy Skin disease virus (LSDV) belonging to the genus Capripoxvirus (CaPV). The disease is widespread in Africa, the Middle East and Asia and has been present in Egypt since 1988. LSD is mainly transmitted by blood-sucking insects. LSD is clinically distinguished by a high fever, skin nodules, and swollen Lymph nodes. Detecting sub-clinical disease can be challenging however, prompt laboratory investigations are vital. Skin lesions are the main source of infection, although the virus is shed through many excretions and discharges including semen. Disease confirmation in clinical laboratories includes detection of viral nucleic acid, antigen and antibody levels. Simple, adaptable, and quick assays for detecting LSDV are required for control measures. Vaccination, together with controlled quarantine and vector control measures, may be beneficial for preventing disease spread. Presently, a range of live attenuated vaccines, have been used in the field with different levels of protection and side effects. With high levels of vaccination coverage, attenuated Neethling vaccines have successfully eradicated of LSDV in Europe. Inactivated LSDV vaccines have also been demonstrated effective in experimental infections. Furthermore, due to its large genome, LSDV is being exploited as a vaccine delivery element, generating an innovative composite with additional viral genes by DNA recombination. Vaccines developed on this basis have the potential to prevent a wide range of diseases and have been demonstrated to be effective in experimental settings. In this review, we emphasizethe advances in diagnostic methods and vaccines developed last decade, thereby providing a basis for future research into various aspects of LSDV and providing information for possibility of disease elimination.

Development of a Multi-Locus Real-Time PCR with a High-Resolution Melting Assay to Differentiate Wild-Type, Asian Recombinant, and Vaccine Strains of Lumpy Skin Disease Virus

Lumpy skin disease virus (LSDV) affects cattle and causes significant economic damage. The live vaccine derived from an attenuated strain is effective but is associated with mild disease and skin lesions in some vaccinated cattle. Moreover, recombinant LSDV strains, particularly one with wild-type field and vaccine strains, have recently emerged and spread throughout Asian countries. A cost-effective LSDV typing method is required. We developed a multi-locus real-time PCR with a high-resolution melting (HRM) assay to differentiate between the wild-type, vaccine, and dominant Asian recombinant strains. Based on a multiple alignment analysis, we selected three target genes for the HRM assay, ORF095, ORF126, and ORF145, in which there are insertions/deletions and nucleotide substitutions between wild-type and vaccine strains, and designed primer sets for the assay. Using the synthetic DNA encoding these genes for the two strains, it was shown that the PCR amplicons intercalated with a saturating fluorescent dye could clearly differentiate between wild-type and vaccine strains in the HRM analysis for all three target genes. Further, using clinical samples, our method was able to identify recombinant strains harboring the wild-type ORF095 and ORF145 and the vaccine strain ORF126 genes. Thus, our HRM assay may provide rapid LSDV typing.

Identification of miR-29a as a novel biomarker for lumpy skin disease virus exposure in cattle

Micro RNAs (miRNAs) have been implicated in the regulation of maturation, proliferation, differentiation, and activation of immune cells. In this study, we demonstrated that miR-29a antagonizes IFN-γ production at early times post-LSDV infection in cattle. miR-29a was predicted to target upstream IFN-γ regulators, and its inhibition resulted in enhanced IFN-γ production in sensitized peripheral blood mononuclear cells (PBMCs). Further, stimulation of PBMCs with LSDV antigen exhibited lower levels of miR-29a, concomitant with a potent cell-mediated immune response (CMI), characterized by an increase in LSDV-specific CD8+ T cell counts and enhanced levels of IFN-γ, which eventually facilitated virus clearance. In addition, a few immunocompromised cattle (developed secondary LSDV infection at ~ 6 months) that failed to mount a potent cell-mediated immune response, were shown to maintain higher miR-29a levels. Furthermore, as compared to the sensitized crossbred cattle, PBMCs from sensitized Rathi (a native Indian breed) animals exhibited lower levels of miR-29a along with an increase in CD8+ T cell counts and enhanced levels of IFN-γ. Finally, we analysed that a ≥ 60% decrease in miR-29a expression levels in the PBMCs of sensitized cattle correlated with a potent CMI response. In conclusion, miR-29a expression is involved in antagonizing the IFN-γ response in LSDV-infected cattle and may serve as a novel biomarker for the acute phase of LSDV infection, as well as predicting the functionality of T cells in sensitized cattle. In addition, Rathi cattle mount a more potent CMI response against LSDV than crossbred cattle.