Detection and quantification of bovine papillomavirus DNA by digital
droplet PCR in sheep blood
Abstract
Abstract – Highly pathogenic bovine Delta papillomaviruses (δPVs) were
detected and quantified for the first time using digital droplet
polymerase chain reaction (ddPCR) by liquid biopsy in 103 clinically
healthy sheep. Overall, ddPCR detected bovine δPVs in 68 blood samples
(66%). Bovine papillomavirus (BPV) infection by a single genotype was
revealed in 59% of the blood samples, and BPV coinfection by double,
triple or quadruple genotypes was observed in 41% of liquid biopsies.
The BPV-2 genotype was most frequently seen in sheep, whereas BPV-1 was
the least common. Furthermore, ddPCR was very useful for detection and
quantification; the BPV-14 genotype was observed for the first time in
ovine species, displaying the highest prevalence in some geographical
areas (Apulia). In 42 of the positive samples (61.8%), a single BPV
infection was observed, 26 of which were caused by BPV-2 (61.9%) and 7
by BPV-13 (16.7%). BPV-14 was responsible for 7 single infections
(16.7%) and BPV-1 for 2 single infections (4.7%). Multiple BPV
coinfections were observed in the remaining 26 positive samples
(38.2%), with dual BPV-2/BPV-13 infection being the most prevalent
(84.6%). BPV infection by triple and quadruple genotypes was also
observed in 11.5% and 3.8% of cases, respectively. The present study
showed that ddPCR, a biotechnological refinement of conventional PCR, is
by far the most sensitive and accurate assay for BPV detection.
Therefore, ddPCR displayed diagnostic and epidemiological value
resulting in the identification of otherwise undetectable BPV genotypes
as well as their geographical distributions and suggesting that animal
husbandry practices contribute to cross-species transmission of BPVs.