ASFV Vaccines: Don’t Hold Your Breath…

With African Swine Fever continuing to dominate the discussion within the Swine Industry, DPI GLOBAL would like to provide talking points from leading Swine Veterinarians as it pertains specifically to an update on the development of a vaccine…

Drs. Scott Dee, Joseph Yaros and Gordon Spronk

Pipestone Veterinary Services, Pipestone, MN

May 1, 2019

African swine fever (ASF) is caused by a large DNA virus (African swine fever virus). ASF produces high case fatality rates that can reach up to 100%. In most affected regions in the world, control has not been effective in part due to lack of a vaccine. The inability to develop effective vaccines is due to several factors, including:

1. 1. 1. 1. The complexity of the ASF virus particle and the large number of proteins encoded by its genome resulting in a large majority of the proteins uncharacterized or unknown function.

1. Many of these virus proteins inhibit the host’s immune system thus facilitating virus replication and persistence.
2. While pigs that recover from infection are resistant to homologous (identical strain) challenge, evidence of cross-protection to heterologous (different strain) does not occur.
3. The virus can “confuse” and “evade” the immune system, inhibiting the production of neutralizing antibodies. Specifically, the receptors the virus uses to infect the swine macrophage are not known.
4. The cell lines needed for commercial vaccine production are not available.

The lack of an effective ASFV vaccine is not due to a lack of effort:

1. ASFV vaccine development has been underway since the 1960s.
2. Many different approaches have been tried, including inactivated (killed) viruses, recombinant proteins/peptides, viral vectors for antigen delivery, and live-attenuated vaccines.
3. As of yet, none of these experimental approaches have resulted in commercial vaccine production for use in the field that is both safe and effective.
4. With the report of the virus in the world’s largest swine herd, there will be increased activity, research and reporting of progress in production of a safe and effective vaccine. A word of caution to any reader that all reports of breakthroughs need to be confirmed from reliable sources and supporting data.

In summary:

1. ASFV is a very complex virus.
2. Attempts to develop vaccines for more than 5 decades by world leaders in vaccinology have been frustrating.
3. It is unlikely that an effective vaccine will be available in the near future.
4. The US industry should focus on keeping ASFV out of the country.
5. The introduction of ASF into Asia reported in August 2018, will lead to increased efforts to develop an effective vaccine by multiple stakeholders.

Resource link and for more information:

Global African Swine Fever Research Alliance (GARA) Gap Analysis Report. 2018: https://go.usa.gov/xPfWr