Evaluation of the serum virome in calves persistently infected with Pestivirus A, presenting or not presenting mucosal disease
Bovine viral diarrhea virus 1, reclassified as Pestivirus A, causes an economically important cattle disease that is distributed worldwide. Pestivirus A may cause persistent infection in that calves excrete the virus throughout their lives, spreading the infection in the herd. Many persistently infected (PI) calves die in the first 2 years of life from mucosal disease (MD) or secondary infections, probably as a consequence of virus-induced immune depression. Here, high-throughput sequencing (HTS) was applied for evaluation of the total virome in sera of (i) PI calves displaying clinically apparent MD (n = 8); (ii) PI calves with no signs of MD (n = 8); and (iii) control, Pestivirus A-free calves (n = 8). All the groups were collected at the same time and from the same herd. Serum samples from calves in each of the groups were pooled, submitted to viral RNA/DNA enrichment, and sequenced by HTS. Viral genomes of Pestivirus A, Ungulate erythroparvovirus 1, bosavirus (BosV), and hypothetical circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses were identified. Specific real-time PCR assays were developed to determine the frequency of occurrence of such viruses in each of the groups. The absolute number of distinct viral genomes detected in both PI calf groups was higher than in the control group, as revealed by higher number of reads, contigs, and genomes, representing a wider range of taxons. Genomes representing members of the family Parvoviridae, such as U. erythroparvovirus 1 and BosV, were most frequently detected in all the three groups of calves. Only in MD-affected PI calves, we found two previously unreported Hypothetical single-stranded DNA genomes clustered along with CRESS-DNA viruses. These findings reveal that parvoviruses were the most frequently detected viral genomes in cattle serum; its frequency of detection bears no statistical correlation with the status of calves in relation to Pestivirus A infection, since clinically normal or MD-affected/non-affected PI calves were infected with similar U. erythroparvovirus 1 genome loads. Moreover, MD-affected PI calves were shown to support viremia of CRESS-DNA viral genomes; however, the meaning of such correlation remains to be established.
KeywordsBVDV Persistent infection Mucosal disease Virome NGS
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Propesq/UFRGS supported this study. Cláudio Wageck Canal and Paulo Michel Roehe are CNPq productivity research fellows. Matheus Nunes Weber was sponsored by a scholarship from CNPq (process 155366/2016-5) during this study. Funding was provided by Pró-Reitoria de Pesquisa, Universidade Federal do Rio Grande do Sul.
Conceptualization: MNW, SPC, FMS, SS, ACSM, MVB, DD and SPP. Data curation: MNW, SPC, SS, and JCO. Formal analysis: MNW, SPC, SS, FMS, MSS, and ACSM. Investigation: SS, MSS, ACSM, and MVB. Methodology: MNW, SPC, JCO, and FQM. Software: MNW, SPC, FQM, APMV, TFT, and PMR. Supervision: FQM, PMR, and CWC. Writing: MNW, FMS, FQM, PMR, and CWC.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
The project was registered with the Ethics Committee on the Use of Animals (CEUA) of Universidade Federal do Rio Grande do Sul under protocol number # 31976.
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