NEWS ▶▶▶ ASFv vaccine produced in cell line
The US African Swine Fever virus (ASFv) vac- cine candidate has been adapted to grow in a cell line, which means that those involved in vaccine production will no longer have to rely on live pigs and their fresh cells for vaccine production. Senior scientist Dr Manuel Borca, from the Agricultural Research Service (ARS) at the US Department of Agriculture, said, “This opens the door for large-scale vaccine produc- tion, which is a valuable tool for the possible eradication of the virus.” The vaccine candidate has been under devel- opment for years at the Plum Island Animal Dis- ease Center, part of the ARS. The vaccine candi- date revolves around the deletion of the gene I177L from a highly virulent ASFv strain from the country Georgia. Hence, the official name of the vaccine candidate is “ASFV-G-ΔI177L”. The latest discovery, highlighted in the peer-reviewed Journal of Virology, overcomes one of the major challenges for manufacture of an ASFv vaccine. The newly developed vac- cine, grown in a continuous cell line, has the same characteristics as the original vaccine
Scientists study in utero heat stress
produced with fresh swine cells. “Traditionally we used freshly isolated swine cells to produce vaccine candidates, and this constitutes a sig- nificant limitation for large-scale production,” said senior ARS scientist Dr Douglas Gladue. “But now we can retain the vaccine character- istics while simultaneously replicating the vac- cine in lab-grown cell cultures. We no longer have to rely on gathering fresh cells from live swine.” The vaccine candidate was tested in a com- mercial breed of pigs and determined to be safe, protecting pigs against the virus. The team did not observe any negative effects.
US ASFv vaccine works oronasally
More news on the US ASFv vaccine candidate described above: It has been tested successfully when provided through the oronasal route. The announcement offers hope for those countries that have ASF in wild boar populations. Between development and marketing, howev- er, a wide range of is tests required. Publication in a special edition of the peer-reviewed title Vaccines is one of the steps in the vaccine’s de- velopment. Especially for wild boar, intramus- cular vaccination is not an option, but it can be administered through feed that is deposited for them in forests. In December 2019, the news broke that sterile immunity against ASFv was possible with this vaccine. Ever since, the scientific evidence has grown that the researchers are on the right track with this vaccine candidate. In the cur- rent report, the scientists state that the vaccine candidate has been proven “safe and highly efficacious in challenge studies using parental ASFv-G”. The trial of the oronasal vaccine version was
carried out with three groups of five cross- breed Yorkshire pigs weighing roughly 40 kg. Prior to a challenge with ASFv-G virus, the ani- mals were inoculated with one of the follow- ing: an intramuscular vaccine, an oronasal vac- cine in the rear of the nasal cavity and at the base of the tongue, or a mock vaccine. The team recorded clinical signs daily throughout the experiment. The research team also evalu- ated the presence of virus-specific antibodies in the sera of inoculated pigs. Having followed the progress of the outbreak, the Plum Island team wrote that the vaccine candidate can be administered by the oronasal route to achieve a similar efficacy to that of intramuscular administration. The news does not mean that the vaccine is available for use in wild boar populations just yet. The next steps include formulating the vaccine into baits and testing for oral con- sumption of the baits. In addition, the vaccine will also have to be tested for efficacy and safety in wild boar.
Gestating sows experiencing heat stress can predispose unborn piglets to health compli- cations and diminished performance later in life, US research has found. The team of scien- tists, from the Agricultural Research Service (ARS), Purdue University, the University of Missouri and the Oak Ridge Institute for Science and Education found that “in utero heat stress” may also hypersensitise the pig- let’s immune system, potentially doing more harm than good to the young animals. The team published an article about this research late in 2020 in the peer-reviewed Journal of Animal Science. A recent news release at the ARS website ex- plained in detail that pigs are more suscepti- ble to heat stress due to an inability to sweat. That places them at greater risk of health and production problems. Research has shown that pigs experiencing heat stress during pregnancy can predispose their offspring to complications later in life that can lead to di- minished performance, including efficient feed use, growth rate and ultimately, pork production. However, less is known about how this heat stress affects their offspring’s innate immuni- ty, or first-line defence against disease-caus- ing bacteria and other pathogens, noted Jay S. Johnson, animal scientist at the ARS in the news release.
Dr Johnson said their research dovetails with increasing concern over the potential impacts of global climate change on swine welfare and management – especially in regions of the world prone to frequent or prolonged drought and heat waves.
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▶ PIG PROGRESS | Volume 37, No. 5/6, 2021 33
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