In vitro and in vivo assessment of orf virus (ORFV) by electron microscopy

Abstract

Transmission electron microscopy (TEM) was employed for describing skin and scab lesions in goats affected by orf virus and to demonstrate the parapoxvirus from clinical suspensions by negative staining and ORFV confirmation by immunogold electron microscopy. All samples were confirmed as parapoxvirus by semi-nested PCR amplification of partial gene encoding for the B2L envelope protein. Skin lesions were characterized by ballooning degeneration and loss of desmosomes of the spinosum cells, cytolysis and vesicle formation. Nuclear changes included chromatin margination and increase in electron density. Cytoplasmic changes were typical of cell swelling, vacuolation and the presence of uniform, moderately electron dense viroplasm, situated in the perinuclear region. Various intracellular forms including immature virions (IV), mature virions (IMV) and wrapped virions (WV) were observed in the cytoplasm. All these forms of ORFV were observed morphologically akin to vaccinia virus (VACV). Negative staining of clinical samples and viral suspensions showed typical parapoxvirus morphology with a characteristic criss-cross tubular surface

A Review on Human Orf: A Neglected Viral Zoonosis

“…26 This pattern wrapping around the particle surface is genetically encoded in the virus genome. [26][27][28] The mature ORFV particle when emerged from an infected cell after lysis appears enveloped and infectious. However, when the virions are viewed intracellularly, some of the particles appeared to possess a second wrapping membrane that originates from the Golgi apparatus and buds off the infected cell as external enveloped virion.…”

“…82 ORFV observed under electron microscopy demonstrates a classic ovoid crisscrossed viral particle that helps for differential diagnosis (Figure 1). 27 On the other hand, ORFV isolation using different tissue culture systems and embryonated eggs are potential options; however, the growth rate of ORFV can be slow and variable. 81 Moreover, isolation of the virus in tissue culture usually requires primary cell lines that are relatively difficult to obtain on a routine basis compared to continuous cell culture systems for the developing world.- 83 The cell culture system is normally employed in a live attenuated ORFV vaccine preparation for animals such as primary neonatal bovine or ovine testicular cells used to culture the virus.…”

“…However, when the virions are viewed intracellularly, some of the particles appeared to possess a second wrapping membrane that originates from the Golgi apparatus and buds off the infected cell as external enveloped virion. 23 , 27 …”

“… 82 ORFV observed under electron microscopy demonstrates a classic ovoid crisscrossed viral particle that helps for differential diagnosis ( Figure 1 ). 27 …”

Natural Infection of Goats with Orf (Contagious ecthyma) and Its Diagnosis

“…Besides the current applications, other confirmatory applications were also employed. In our earlier studies, ORFV has also been successfully cultured in continuous lamb testis cells (OA3.Ts) (Nashiruddullah et al, 2016) and the virus has been demonstrated by immunofluorescence and visualized by Transmission Electron Microscopy (TEM) (Nashiruddullah et al, 2018). ELISA applications for antibody detection showed positive results and were consistent.…”