DNA-Protein Vaccination Strategy Does Not Protect from Challenge with African Swine Fever Virus Armenia 2007 Strain

Abstract

African swine fever virus (ASFV) causes high morbidity and mortality in swine (Sus scrofa), for which there is no commercially available vaccine. Recent outbreaks of the virus in Trans-Caucasus countries, Eastern Europe, Belgium and China highlight the urgent need to develop effective vaccines against ASFV. Previously, we evaluated the immunogenicity of a vaccination strategy designed to test various combinations of ASFV antigens encoded by DNA plasmids and recombinant proteins with the aim to activate both humoral and cellular immunity. Based on our previous results, the objective of this study was to test the combined DNA-protein vaccine strategy using a cocktail of the most immunogenic antigens against virulent ASFV challenge. Pigs were vaccinated three times with a cocktail that included ASFV plasmid DNA (CD2v, p72, p32, +/−p17) and recombinant proteins (p15, p35, p54, +/−p17). Three weeks after the third immunization, all pigs were challenged with the virulent ASFV Armenia 2007 strain. The results showed that vaccinated pigs were not protected from ASFV infection or disease. Compared to the non-vaccinated controls, earlier onset of clinical signs, viremia, and death were observed for the vaccinated animals following virulent ASFV challenge. ASFV induced pathology was also enhanced in the vaccinated pigs. Furthermore, while the vaccinated pigs developed antigen-specific antibodies, immunized pig sera at the time of challenge lacked the capacity to neutralize virus, and instead was observed to enhance ASFV infection in vitro. The results of this work points to a putative immune enhancement mechanism involved in ASFV pathogenesis that warrants further investigation. This pilot study provides insight for the selection of appropriate combinations of ASFV antigens for the development of a rationally-designed, safe, and efficacious vaccine for ASF.

Clinical Course and Gross Pathological Findings in Wild Boar Infected with a Highly Virulent Strain of African Swine Fever Virus Genotype II

“…To begin to understand ASF pathology and clinical course in wild boar, we experimentally infected animals with the Arm07 ASFV strain, which is highly virulent in domestic pigs and wild boar [ 14 , 15 ]. In addition, this strain is closely related to other strains isolated in Eastern Europe, such as Georgia 2007 strain [ 16 , 17 ]. Few studies have examined the pathology caused by closely strains in a minimal number of wild boars.…”

Current status and evolving approaches to African swine fever vaccine development

“…Given the fact that peptide or DNA immunization is unable to confer full protection, some groups have proposed improved approaches such as DNA–protein vaccination strategy. Recently, a combined ASFV plasmid DNA (CD2v, p72, p32, ±p17) and recombinant proteins (p15, p35, p54, ±p17) have been used to immunize pigs; however, the pigs were not protected from ASFV infection (Sunwoo et al, ). Pérez‐Núñez et al () have also reported that DNA–protein immunization helped to identify viral antigen‐specific responses and provide information about the potential correlates of safer ASFV subunits vaccines.…”

Unravelling the dispersal dynamics and ecological drivers of the African swine fever outbreak in Belgium

“…African swine fever is a disease originally endemic to sub-Saharan Africa where it affects warthogs and domestic pigs, with soft tick species of the genus Ornithodoros acting as vectors (Chenais, Ståhl, Guberti, & Depner, 2018). The causative agent of the disease is the African swine fever virus (ASFV), a DNA virus belonging to the family Asfarviridae and genus Asfivirus (Galindo & Alonso, 2017) and for which there is currently no effective vaccine available (Sunwoo et al, 2019). In addition to its sub-Saharan African endemic range, the virus has also been circulating in Sardinia since 1978 (Mur et al, 2016).…”