Source: USDA ARS, 4/25/22 Scientists with the U.S. Department of Agriculture's Agriculture Research Service (ARS) today announced that a vaccine candidate for African Swine Fever (ASF) passed an important safety test required for regulatory approval, moving the vaccine one step closer to commercial availability.The test is an important milestone as part of a series of safety
studies. These new results show that USDA's vaccine candidate does not revert
to its normal virulence, after being injected into swine. This "reversion
to virulence" test is required to ensure that the vaccine's weakened form
of the ASF virus does not revert to its original state. "This is a critical milestone for the ASF vaccine
candidate. These safety studies bring this vaccine one step closer to being
available on the market," said senior ARS scientist Manuel Borca. These safety studies are necessary to gain approval for use in
Vietnam and eventually in other countries around the world. Future commercial
use, however, will depend on approval from the department of animal health
within each requesting country. Although the virus is causing profound economic losses to the
swine industry, there have not been any outbreaks in the United States. The highly contagious
ASF virus spread from Africa to the Republic of Georgia in 2007, and has since
swept through Central Europe and Asia, before reaching the Dominican Republic
in 2021. The virus is unable to transmit from pigs to humans.
"It is very hard to predict how selective pressure can
cause a live attenuated vaccine to return to virulence," said senior ARS
scientist Douglas Gladue. "In the case of this particular
vaccine candidate, ASFV-G-DI177L, we deleted a gene, which makes it difficult
for the virus to simply add the gene back. So, we expected reversion to
its original form to be unlikely, but the test still has to be performed." An attenuated vaccine strain retains much of its genetic makeup
and could genetically change when exposed to various external circumstances.
All live attenuated vaccines are weakened versions of a virus and can be
used as a vaccine because the live vaccine virus will not cause illness and can
still provide immunity. This research is highlighted in this month's issue of Viruses. The vaccine candidate was
recently selected by NAVETCO for commercial development in Vietnam. NAVETCO has
partnered with ARS on ASF vaccine research and development since 2020. Further
development will continue once the vaccine candidate receives regulatory
approval from Vietnam. The Agricultural Research Service is the U.S.
Department of Agriculture's chief scientific in-house research agency. Daily,
ARS focuses on solutions to agricultural problems affecting America. Each
dollar invested in agricultural research results in $17 of economic impact.
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