Abstract
BackgroundAfrican swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), a re-expanding devastating and highly lethal hemorrhagic viral disease. microRNAs (miRNAs) are a new class of small non-coding RNAs that regulate gene expression post-transcriptionally. The discovery of virus specific miRNAs has increased both in number and importance in the past few years. We have recently described the differential expression of several porcine miRNAs during in vivo infection with attenuated and virulent ASFV strains. Here, we have extended these studies trying to identify the presence of viral miRNAs encoded by ASFV in an in vivo infection in pigs.ResultsSixteen small RNA libraries were analyzed from spleen and submandibular lymph nodes obtained from eight pigs, seven infected with either the virulent E75 ASFV strain or its attenuated counterpart E75CV1, or from pigs surviving E75CV1-infection and challenged with BA71 (heterologous challenge) and one non infected as negative control. Samples were recovered at different times post-infection. Libraries were analyzed by next-generation sequencing. Some viral miRNA candidates were initially identified, which did not correspond to porcine miRNAs. Further structural analyses were carried out in order to confirm if they met the conformational requirements to be considered a viral miRNA.ConclusionsThe analysis of sixteen small RNA libraries prepared from two different tissues obtained from pigs experimentally infected with E75, E75CV1 or with E75CV1 plus BA71, revealed the presence of six potential miRNA sequences but none of them met the requirements to be considered as viral miRNAs. Thus, we can conclude that ASFV does not express miRNAs in vivo, at least under the experimental conditions described here.
Highlights
African swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), a re-expanding devastating and highly lethal hemorrhagic viral disease. microRNAs are a new class of small non-coding RNAs that regulate gene expression post-transcriptionally
The potential presence of viral miRNAs in ASFV-infected pigs was analyzed by high-throughput sequencing of small RNA libraries prepared from two tissues recovered in three conditions: i) The animals infected with virulent strain E75 necropsied at 3 and 7 dpi, ii) The animals infected with the attenuated strain E75CV1 and necropsied at 3 and 31 dpi, iii) The animals infected with the attenuated strain E75CV1 and re-inoculated at 31 dpi with the virulent strain BA71 and necropsied at 38 dpi
The pigs inoculated with the virulent strains E75 and BA71 developed typical clinical signs, while the pigs inoculated with the attenuated E75CV1 strain developed mild or no clinical signs [15]
Summary
African swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), a re-expanding devastating and highly lethal hemorrhagic viral disease. microRNAs (miRNAs) are a new class of small non-coding RNAs that regulate gene expression post-transcriptionally. MicroRNAs (miRNAs) are a new class of small non-coding RNAs that regulate gene expression post-transcriptionally. We have recently described the differential expression of several porcine miRNAs during in vivo infection with attenuated and virulent ASFV strains. We have extended these studies trying to identify the presence of viral miRNAs encoded by ASFV in an in vivo infection in pigs. African swine fever (ASF) is a contagious disease that affects domestic and wild pigs caused by ASF virus (ASFV) belonging to the Asfarviridae family, genus Asfivirus. MiRNAs encoded by viruses have been identified to be involved in the infection process. ASFV was a good candidate for a virus capable of encoding miRNAs. On the other hand, recently, our group has identified differential expression of porcine miRNAs in pigs after the infection with ASFV [11]
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