Cellular infiltration, cytokines, and histopathology of skin lesions associated with different clinical forms and stages of naturally occurring lumpy skin disease in cattle.

Lumpy skin disease (LSD) caused by the Capripoxvirus LSD virus which infects cattle, leading to a serious disease characterized by fever and the eruption of skin nodules all over the surface of the body. Our understanding of the pathogenesis of this disease is still incomplete, particularly the immunopathological alterations occurring in the skin nodules of infected animals. Therefore, we collected skin nodules from naturally infected cattle with different forms of the disease, both in the early stage of clinical infection and after disease progression. The skin samples were examined both histopathologically and immunohistochemically using a variety of antibodies targeting immune cellular markers and cytokines. As a result, the dermatohistopathology revealed orthokeratotic hyperkeratosis, vasculitis, epidermal microvesicles, and cellules claveleuses of Borrel in the early stage of infection, with the severity of the lesions correlating with the severity of the clinical disease. Meanwhile, late-stage samples had epidermal hyperkeratosis as well as dermal lymphocytic and histiocytic infiltrations. The predominant cellular infiltrates in the cutaneous lesions of early-stage LSD samples were interferon (IFN)-γ+ cells and CD4+ T lymphocytes with few macrophage lineage cells. However, in the late-stage samples, numerous Iba-1+ macrophages, with few IFN-γ+ cells and CD4+ T lymphocytes, were detected. Our findings indicate that IFN-γ+ cells, CD4+ T lymphocytes, and macrophages play a key role in the immunity against natural LSD virus infection and imply that cutaneous vasculopathy associated with LSD virus infection is an immune-mediated lesion. The current study contributes to our understanding of the pathogenesis of LSD.

Comparative Study of the Pathogenesis of Rhinopneumonitis Induced by Intranasal Inoculation of Hamsters with Equine Herpesvirus-9, Equine Herpesvirus-1 strain Ab4p and Zebra-borne Equine Herpesvirus-1.

Equine herpesvirus-9 (EHV-9), equine herpesvirus-1 (EHV-1) and zebra-borne EHV-1 are members of the family Herpesviridae and cause encephalitis and rhinopneumonitis in a range of animal species. The aim of this study was to characterize and compare the rhinopneumonitis induced by experimental intranasal inoculation of groups of hamsters with EHV-9, EHV-1 strain Ab4p or zebra-borne EHV-1 viruses. Animals inoculated with EHV-9 had earlier and more severe neurological and respiratory signs than those inoculated with EHV-1 strain Ab4p or zebra-borne EHV-1. At 4-5 days post inoculation (dpi), hamsters inoculated with EHV-9 had significantly increased expression of open reading fame (ORF) 30, the viral gene encoding the DNA polymerase, in lung tissue. ORF 30 expression at these time points was higher in the hamsters infected with EHV-9 than in those inoculated with the other two viruses. Severe, mild or very mild rhinitis was seen in animals inoculated with EHV-1 strain Ab4p, EHV-9 and zebra-borne EHV-1, respectively. Viral antigen was detected in olfactory receptor neurons, inflammatory cells and desquamated epithelial cells in animals in all groups until 5 dpi. Tracheitis was also seen in all three virus-infected groups with viral antigen detected in tracheal epithelium. Inoculated hamsters developed interstitial pneumonia of increasing severity over the course of the experiment. Bronchopneumonia and vasculitis were also seen in all three infected groups. These results confirm that, in addition to their neurotropism, EHV-9 and zebra-borne EHV-1 are pneumotropic viruses. EHV-1 strain Ab4p caused more severe upper respiratory tract disease, but no significant differences were detected in the severity of pneumonia induced by each virus.

Time Course-Dependent Study on Equine Herpes Virus 9-Induced Abortion in Syrian Hamsters.

This study aimed to follow the time-course pathogenesis of EHV-9 abortion in early and late trimesters. Twenty-seven pregnant hamster dams were divided into three groups: (G1) control, (G2) EHV-9-inoculated on the 5th day (early trimester), and (G3) EHV-9-inoculated on the 10th day of gestation (late trimester). Dams were sacrificed at different time points during gestation and examined for viremia and viral DNA in different fetal and maternal tissues and pathological changes in fetal tissue, placenta, and cytokines. Animals in G3 showed a marked increase in the number of dead fetuses than those in G2. Histopathological findings of G2 showed early band coagulative necrosis of maternal spaces and stromal decidual cells. Necrotic changes were observed within the decidua basalis, spongiotrophoblast layer, and labyrinth. First, the virus was localized within mononuclear leukocytes in the decidua capsularis and basalis, and within the necrotic chorionic villi and cervical epithelium. G3 demonstrated degenerative changes within the chorionic villi and trophospongium. The virus antigen was observed within the chorionic villi, trophoblasts, mononuclear cells, and fetal tissues. In conclusion, EHV-9 induced abortion mostly occurs through necrosis of the chorionic villi and cannot cross through the capsular placenta in the early trimester but can through the developed decidual placentation.

Effect of a single point mutation on equine herpes virus 9 (EHV-9) neuropathogenicity after intranasal inoculation in a hamster model.

This study aimed to investigate the neuropathogenesis of equine herpes virus 9 (EHV-9) by studying the effects of a single point mutation introduced in two different EHV-9 genes. The two EHV-9 mutants, 14R and 19R, were generated carrying a point mutation in two separate EHV-9 genes. These mutants, along with the wild-type EHV-9, were used to infect a hamster model. The EHV-9- and 19R-infected groups showed earlier and more severe clinical signs of infection than the 14R-infected group. The white blood cells (WBCs) count was significantly increased in both EHV-9- and 19R-infected groups compared to the 14R-infected group at the 4th day post infection (DPI). Viremia was also detected earlier in both EHV-9- and 19R-infected groups than 14R-infected group. There were differences in the anterograde transmission pattern of both EHV-9 and 19R compared to 14R inside the brain. Serum TNF-α, IL-6 and IFN-γ levels were significantly increased in both EHV-9- and 19R-infected groups compared to the 14R-infected group. Histopathological and immunohistochemical analyses revealed that the mean group scores for the entire brain were significantly higher in both EHV-9- and 19R- infected groups than 14R-infected group. Collectively, these results confirm that the gene product of Open Reading Frame 19 (ORF19) plays an important role in EHV-9 neuropathogenicity and that the mutation in ORF19 is responsible for the attenuation of EHV-9.