Development of diploid embryonic sheep heart cells and sensitivity study of three poxviruses: Lumpy skin disease, Camelpox viruses, and Ecthyma

Abstract

Abstract Lumpy skin disease virus (LSDV), Camelpox virus (CPV), and Ecthyma virus (ORFV), the three representative viruses of Poxvirus family, are usually grown on embryonated eggs or primary cells for isolation or production since continuous cell lines are less sensitive. The use of eggs or primary cells presents disadvantages such as availability, potential endogenous contaminants, and limited number of passages. In this study, we developed a diploid cell, originated from an embryonic sheep heart and demonstrated their high prolificity and capability of long-term storage. We also demonstrated the maintain of the diploid cell sensitivity to isolation and growth of three genera of Poxvirus family; Capripoxvirus (LSDV), Orthopoxvirus (CPV) and Parapoxvirus (ORFV). Developed cell grow with a doubling time of 24h and can reach 40 passages with a satisfactory yield comparable to Lamb primary testis at passage 5. After infection, the titer of each Poxvirus is maintained between 7, 0 and 7,6 log TCID50/ml up to 5 passages, around 6,8 for the three viruses at passages 6 to 25, 6,4 at passage 30 and 5,6 at passage 40. Sensitivity of diploid embryonic heart cells did not decrease after long-term conservation in liquid nitrogen. Results showed a higher sensitivity of those cells comparatively to lamb primary testis, intensively used for Capripoxvirus and parapoxvirus detection and growth or Vero cells for Orthopoxvirus. The study demonstrated the interest of embryonic heart diploid cells for poxvirus isolation and production to avoid constraints of eggs, embryo, or primary cells.