Development of a novel live attenuated African Swine Fever vaccine based in the deletion of gene I177L
Inventors
Gladue, Douglas P. • Borca, Manuel V.
Assignees
US Department of Agriculture USDA
Publication Number
US-11813319-B2
Publication Date
2023-11-14
Expiration Date
2039-09-24
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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-GΔI1771 modified virus, a recombinant ASFV-G modified by deleting a portion of the I177L ORF rendering the I177L gene nonfunctional.
Core Innovation
The invention provides a recombinant African Swine Fever Virus (ASFV) live attenuated vaccine for prevention of ASF caused by various strains of ASFV, including the highly virulent Georgia 2007 isolate (ASFV-G). The vaccine comprises the ASFV-GΔI177L modified virus, which is a recombinant ASFV-G virus with a deletion in the I177L open reading frame (ORF), rendering the I177L gene nonfunctional.
African Swine Fever (ASF) is a contagious viral disease of swine that is often fatal, characterized by fever, hemorrhages, ataxia, and severe depression. The disease is endemic in multiple regions including sub-Saharan Africa, parts of Europe, and Asia. There is no commercial vaccine available, and control relies on quarantine and slaughter. Attempts at vaccines using infected cell extracts, purified and inactivated virions, or infected macrophages have failed to induce protective immunity. Survivors of infection develop long-term resistance mostly to homologous strains but rarely to heterologous virus challenge.
The invention addresses the problem of the lack of effective vaccines by constructing a genetically modified ASFV-G virus with a deleted I177L gene that results in a live attenuated virus. Animals inoculated intramuscularly with ASFV-GΔI177L remain clinically normal during observation and are protected upon challenge with the virulent parental ASFV-G strain. The vaccine induces immunity and prevents clinical disease presentation.
Claims Coverage
The patent contains one independent recombinant virus claim and one independent method claim, supported by additional dependent claims refining the mutation specifics and vaccine composition.
Recombinant ASFV mutant with non-functional I177L gene
A recombinant ASFV mutant virus comprising a synthetic mutation in the I177L open reading frame or in a regulatory element controlling the expression of the I177L protein, resulting in a non-functional genomic I177L gene.
Deletion mutation in I177L gene
The synthetic mutation is a deletion mutation resulting in the deletion of one or more nucleotides between positions 174471 and 175004 of SEQ ID NO:1.
Frameshift, insertion, or nonsense mutation in I177L gene
The synthetic mutation is a frameshift mutation, insertion mutation, or nonsense mutation of one or more nucleotides between positions 174471 and 175004 of SEQ ID NO:1.
Mutant ASFV is an ASFV-Georgia isolate
The mutant ASFV can be an ASFV-Georgia isolate.
Mutant ASFV genome identity
The mutant ASFV comprises a genome at least 95% identical to SEQ ID NO:2.
Vaccine composition comprising the recombinant mutant virus
A vaccine composition against ASFV-G comprising the recombinant virus defined by the synthetic mutation of the I177L gene resulting in non-functional I177L.
Method for protecting swine using live attenuated vaccine
A method for protection of swine against ASFV by administering a live attenuated vaccine comprising the recombinant virus with non-functional I177L in an amount effective to protect swine from clinical ASFV disease.
Specific ASFV strain for protection method
The ASFV in the protection method is ASFV-G.
Effective vaccine dosage
The amount effective to protect swine from clinical ASFV disease is a vaccine comprising 10² to 10⁶ HAD50 of the genetically modified recombinant virus.
The claims cover creation of genetically modified ASFV viruses with synthetic mutations in the I177L gene that render it non-functional, and their use in vaccine compositions and methods to protect swine against ASFV, particularly the ASFV-Georgia isolate, by live attenuated vaccination at effective dosages.
Stated Advantages
Deletion of the I177L gene produces complete attenuation of the highly virulent ASFV-G virus, making it safe for inoculated pigs.
Vaccination with the ASFV-GΔI177L virus induces protective immunity in swine against subsequent challenge with lethal parental ASFV-G strain.
The ASFV-GΔI177L mutant virus does not cause clinical signs or disease in vaccinated pigs during the observation period.
The vaccine strain exhibits reduced replication in vitro compared to parental ASFV-G, correlating with safety.
ASFV-GΔI177L infected animals do not shed the vaccine virus to naive animals, reducing transmission risk.
Vaccinated animals develop robust and lasting anti-ASFV antibody responses.
Vaccination can induce sterile immunity preventing replication of challenge virus in most animals at doses of 10⁴ HAD50 or higher.
Documented Applications
Use as a live attenuated vaccine to protect swine against African Swine Fever Virus, particularly the highly virulent ASFV-G Georgia 2007 isolate.
Intramuscular administration of the recombinant ASFV-GΔI177L as a protective immunogen in domestic pigs and other members of the Suidae family.
Use in immunogenic compositions to elicit protective immune responses and confer immunity in swine populations.
Serological and genetic DIVA (differentiating infected from vaccinated animals) testing to distinguish vaccinated animals from those infected with wild-type ASFV.
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