Rapid detection of African swine fever virus

“We have identified a cell line that can be used to isolate and detect a live virus,” said ARS scientist Dr. Douglas Gladue. “This is a major breakthrough and a huge step forward in the diagnosis of African swine fever virus.”
There is currently no vaccine for ASF, and outbreak control often depends on the isolation and removal of infected or exposed animals. Until now, effective detection of live ASF virus required the collection of blood cells from live donor pigs for each diagnostic test, as the cells can only be used once. New cell lines can be continuously replicated and frozen for future use, reducing the number of live donor animals needed.
The new cell line could also be used in veterinary diagnostic laboratories, which traditionally do not have access to porcine blood cells needed to detect live ASF virus.
According to the study, the diagnosis of ASF in clinical samples (mostly whole blood) was done using real-time polymerase chain reaction (RT-PCR), a molecular test that can detect a small portion of the viral genome but cannot detect live infectious virus. . Virus isolation is necessary to confirm active infection and subsequent analysis, such as whole genome sequencing. Currently, virus isolation is only possible using primary porcine macrophages, which are rarely available in most regional veterinary diagnostic laboratories. The production of primary porcine macrophages is time consuming and labor intensive due to the need to collect cells from pig blood or isolate cells from lungs. Previous studies have shown that ASF virus replicates in established cell lines after the virus has adapted to a particular cell line, usually after a serial passaging process. To date, mature commercially available cell lines have not been shown to be suitable for ASF virus isolation using field samples.
In this study, the investigators identified a cell line capable of supporting detection of ASFV in field samples with a TCID50 sensitivity comparable to that of primary porcine macrophages. Careful screening of commercially available cell lines has led to the identification of African green monkey MA-104 cells as a surrogate for primary porcine macrophages for ASF virus isolation.
There have been recent outbreaks of the ASF virus outside the African continent since its emergence in the Republic of Georgia in 2007. The disease has recently spread to China and countries in Southeast Asia, including Mongolia, Vietnam, Cameroon, North and South Korea, Laos, Myanmar, Philippines, Timor-Leste, Indonesia, Papua New Guinea and India. The current outbreak of the strain “Georgia” is highly contagious and fatal to domestic pigs, with a mortality rate of up to 100%. Although the virus is currently absent from the United States, the US pig industry could suffer significant economic losses in the event of an outbreak.