Development of a novel live attenuated African swine fever vaccine based in the deletion of gene A137R
Inventors
Gladue, Douglas P. • Borca, Manuel V.
Assignees
US Department of Agriculture USDA
Publication Number
US-11801296-B2
Publication Date
2023-10-31
Expiration Date
2041-06-30
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Abstract
Provided herein are details on the construction of a recombinant African Swine Fever Virus (ASFV) live attenuated vaccine for prevention of ASF caused by various strains of ASFV, such as the highly virulent Georgia 2007 isolate (“ASFV-G”). An exemplary vaccine comprises the ASFV-GΔA137R modified virus, a recombinant ASFV-G modified by deleting a portion of the A137R ORF rendering the A137R gene nonfunctional.
Core Innovation
The invention provides a genetically modified African Swine Fever Virus (ASFV) live attenuated vaccine based on the deletion of the A137R gene, specifically from the highly virulent ASFV Georgia 2007 isolate (ASFV-G). This recombinant virus, referred to as ASFV-G ΔA137R, contains a deletion mutation rendering the A137R gene nonfunctional, and this modification results in a virus that is fully attenuated in swine yet capable of inducing protective immunity against clinical ASF disease.
The problem addressed by the invention is the absence of any commercial vaccine for African Swine Fever (ASF), a contagious and often fatal disease in swine caused by ASFV. Current control methods rely on quarantine and culling, and prior vaccination attempts with various ASFV preparations have failed to induce protective immunity. This invention aims to overcome these limitations by providing a live attenuated ASFV vaccine that is safe and immunogenic, specifically by genetically deleting the A137R gene, thereby producing a virus that does not cause disease but confers protection against virulent ASFV challenge.
The invention further describes the construction of this recombinant virus via homologous recombination methods to delete a portion of the A137R open reading frame, resulting in a complete attenuation of virulence in swine, while maintaining the virus’ capacity to replicate to some extent in vitro. Vaccination with ASFV-G ΔA137R protects swine from clinical ASF disease upon challenge with the parental virulent ASFV-G strain, demonstrating its utility as an effective live attenuated vaccine.
Claims Coverage
The patent includes two main independent claims covering the genetically modified virus with specific genome identity and the recombinant ASFV virus with a synthetic mutation in the A137R gene leading to a non-functional protein, along with their uses in protective vaccines and methods of administration.
Genetically modified ASFV genome with high sequence identity to SEQ ID NO: 2
The genetically modified virus comprises a viral genome at least 99.5% identical to SEQ ID NO: 2, specifically including versions that are at least 99.8% identical or exactly identical to SEQ ID NO: 2.
Vaccine composition containing the genetically modified ASFV for ASFV-Georgia 2007 isolate
A vaccine composition comprising the genetically modified virus with the defined genome, formulated against African Swine Fever Virus, particularly the ASFV-Georgia 2007 isolate.
Method of protecting swine by administering live attenuated vaccine with genetically modified virus
A method for protecting swine against ASFV by administering an effective amount of a live attenuated vaccine comprising the genetically modified virus with at least 99.5% genome identity to SEQ ID NO: 2, specifically at dosages between 102-106 HAD50.
Recombinant ASFV virus with synthetic mutation in A137R gene rendering it non-functional
A recombinant ASFV virus comprising a synthetic mutation, such as deletion, frameshift, insertion, or nonsense mutation, in the genomic A137R open reading frame or its regulatory elements that results in a non-functional A137R gene, including viruses derived from ASFV-Georgia isolates with genome identities of at least 95% or 99% to SEQ ID NO: 2.
Vaccine composition comprising recombinant ASFV with non-functional A137R gene
Vaccine composition against ASFV-G, comprising the recombinant ASFV virus containing the synthetic mutation in A137R as described.
Method for protecting swine using live attenuated vaccine with recombinant ASFV virus
A method for protecting swine against ASFV by administering a live attenuated vaccine comprising the recombinant ASFV virus with non-functional A137R gene, at an effective amount of at least 102 HAD50.
The claims collectively cover genetically modified ASFV viruses with specific high identity to a defined sequence where the A137R gene is non-functional, vaccine compositions comprising these viruses, and methods of protecting swine by administering these live attenuated vaccines in defined dosage ranges.
Stated Advantages
The vaccine induces complete attenuation of a previously highly virulent ASFV strain, thereby preventing clinical disease in vaccinated swine.
Vaccination with the ASFV-G ΔA137R virus provides protective immunity against lethal challenge with the parental virulent ASFV-G isolate.
The recombinant ASFV-G ΔA137R virus retains the ability to replicate in swine macrophages, facilitating vaccine production.
The vaccine allows differentiation of infected animals from vaccinated ones (DIVA) by detecting absence or mutation of the A137R gene product.
The vaccine induces a strong host antibody response correlating with protection.
The vaccine can elicit sterile immunity, preventing replication of challenge virus in vaccinated animals.
Documented Applications
Preventive vaccination of domestic and wild swine against African Swine Fever caused by highly virulent ASFV strains, including the ASFV-Georgia 2007 isolate.
Use as a live attenuated vaccine in swine to induce protective immunity and prevent ASF clinical disease.
Differentiation of infected versus vaccinated animals through serological or genetic testing against the A137R gene or protein.
Potential use in various delivery methods including intramuscular, subcutaneous, intranasal, oral, or bait delivery systems in swine populations.
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