ASFV-G-∆I177L as an Effective Oral Nasal Vaccine against the Eurasia Strain of Africa Swine Fever

Abstract

The African swine fever virus (ASFV) is currently causing a pandemic affecting wild and domestic swine from Western Europe to Asia. No commercial vaccines are available to prevent African swine fever (ASF), resulting in overwhelming economic losses to the swine industry. We recently developed a recombinant vaccine candidate, ASFVG-ΔI177L, by deleting the I177L gene from the genome of the highly virulent ASFV strain Georgia (ASFV-G). ASFV-G-ΔI177L has been proven safe and highly efficacious in challenge studies using parental ASFV-G. Here, we present data demonstrating that ASFV-G-ΔI177L can be administered by the oronasal (ON) route to achieve a similar efficacy to that of intramuscular (IM) administration. Animals receiving ON ASFV-G-ΔI177L were completely protected against virulent ASFV-G challenge. As previously described, similar results were obtained when ASFV-G-ΔI177L was given intramuscularly. Interestingly, viremias induced in animals inoculated oronasally were lower than those measured in IM-inoculated animals. ASFV-specific antibody responses, mediated by IgG1, IgG2 and IgM, do not differ in animals inoculated by the ON route from that had IM inoculations. Therefore, the ASFV-G-ΔI177L vaccine candidate can be administered oronasally, a critical attribute for potential vaccination of wild swine populations.

African Swine Fever Virus as a Difficult Opponent in the Fight for a Vaccine—Current Data

“…ASFV-G-ΔI177L proved to be safe and highly efficacious in challenge studies using parental ASFV-G in the previously described studies by Borca et al [ 57 , 58 ]. Effective replication of this vaccine strain was possible only in primary swine macrophages, which limits the large-scale production potential.…”

“…In the next few years, this scenario is unlikely to occur [ 90 ]. Few studies have been carried out on the oral immunization of wild boars against ASF [ 58 , 61 ]. The first report on the experimental vaccination of wild boars against genotype II ASFV, and also the first study on oral immunization against any ASFV strain in wild boars, was published in 2019 by Barasona et al [ 61 ].…”

“…These facts indicate that o.n. administration of ASFV-G-∆I177L is safe and facilitates the potential use of this vaccine in wild swine populations [ 58 ].…”

Report on the First African Swine Fever Case in Greece

“…Appropriate application of respective farm biosecurity measures should be the major priority in order to reduce the risk of infection. Finally, continuing efforts to develop an effective vaccine have shown promising results and should probably further contribute to the control of the disease [ 13 ].…”

“…Up today, due to the lack of treatment or vaccine development, the early detection and implementation of strict preventive measures constitute the only way to eliminate the disease [ 9 ]. Genetic diversity and the very large and complex genome of the ASF virus increase the difficulty of vaccine development, however, efforts with live attenuated or subunit vaccines from various research groups, have started with respective pilot studies [ 10 , 11 , 12 , 13 ].…”