Abstract
The development of subunit vaccines against African swine fever (ASF) is mainly hindered by the lack of knowledge regarding the specific ASF virus (ASFV) antigens involved in protection. As a good example, the identity of ASFV-specific CD8+ T-cell determinants remains largely unknown, despite their protective role being established a long time ago. Aiming to identify them, we implemented the IFNγ ELISpot as readout assay, using as effector cells peripheral blood mononuclear cells (PBMCs) from pigs surviving experimental challenge with Georgia2007/1. As stimuli for the ELISpot, ASFV-specific peptides or full-length proteins identified by three complementary strategies were used. In silico prediction of specific CD8+ T-cell epitopes allowed identifying a 19-mer peptide from MGF100-1L, as frequently recognized by surviving pigs. Complementarily, the repertoire of SLA I-bound peptides identified in ASFV-infected porcine alveolar macrophages (PAMs), allowed the characterization of five additional SLA I-restricted ASFV-specific epitopes. Finally, in vitro stimulation studies using fibroblasts transfected with plasmids encoding full-length ASFV proteins, led to the identification of MGF505-7R, A238L and MGF100-1L as promiscuously recognized antigens. Interestingly, each one of these proteins contain individual peptides recognized by surviving pigs. Identification of the same ASFV determinants by means of such different approaches reinforce the results presented here.
Highlights
African swine fever (ASF) is a hemorrhagic viral disease of pigs that courses with lethality rates up to 100% in its acute forms
African swine fever virus (ASFV) is the sole member of the family Asfarviridae, genus Asfivirus, and it is included in the nucleocytoplasmic large DNA virus superfamily [2]
ASFV was first described in Kenia in 1921 as an endemic virus continuously circulating between African wild pigs and ticks from the Ornithodoros genus in an asymptomatic manner [3]
Summary
African swine fever (ASF) is a hemorrhagic viral disease of pigs that courses with lethality rates up to 100% in its acute forms. Two ASFV entries in Portugal, dated in 1957 and 1960, provoked 40 years of ASFV endemicity in the Iberian peninsula, the sporadic occurrence of ASF in some countries of Europe and South America and the establishment of ASFV in Sardinia since 1978 until today [4]. In 2014, the virus entered the European Union (EU) territory for the first time, affecting both domestic pigs and wild boars, the latter playing a critical role in ASF spread. In this area, the main causes of ASFV transmission include pig to pig contact, infected pig products, or infected fomites, such as transport vehicles [4]. Developing safe and efficacious vaccines against ASF is a priority for the swine industry worldwide [9]
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