Bovine papillomavirus type 13 DNA in equine sarcoids

Abstract

Equine sarcoids are locally aggressive fibroblastic neoplasms considered to be the most common skin tumors of horses worldwide. Bovine papillomavirus types 1 and 2 have typically been associated with sarcoids in equids. Investigations aiming to identify papillomavirus strains, aside from bovine papillomaviruses 1 and 2, which might be associated with sarcoid lesions, have been lacking. The aim of this article is to report the identification of a third bovine papillomavirus type, bovine papillomavirus 13, associated with equine sarcoids. Six sarcoid lesions were collected from diverse anatomical sites on two horses from southern Brazil. To detect a broad spectrum of papillomavirus strains, eight degenerate primer pairs designed to detect conserved regions on the L1 and E1 genes were tested on the DNA samples. Direct sequencing was then performed on the obtained amplicons, and sequence identities were compared with sequences from all bovine papillomavirus types. The FAP59/FAP64, MY09/MY11, and AR-E1F2/AR-E1R4 sequences generated from the sarcoids were shown to present 99 to 100% identity with bovine papillomavirus 13, a new bovine papillomavirus type previously described in cattle. The results from this study suggest that there is a need to identify bovine papillomavirus type 13 and other papillomavirus strains that might be associated with sarcoids in diverse geographical areas; such investigations might establish the frequency of occurrence of this viral type in these common tumors of equids.

Fig 1

Histological features characteristic of equine sarcoids observed in the lesion collected from the ear of animal A and macroscopically classified as the verrucous type. Discrete epidermal hyperplasia and inward projections of the epidermis (rete pegs, arrow) into the dermis can be observed, as can the proliferation of fibroblasts arranged in short interlacing bundles. Hematoxylin and eosin (H&E) staining was used.

Fig 2

Maximum-likelihood phylogenetic tree reconstructed from L1 nucleotide sequences of all previously sequenced BPVs, of other even-toed ungulate PVs, and of BPV type 13 obtained from equine sarcoid DNA samples. The tree is divided into the previously determined genera Deltapapillomavirus (δ), Epsilonpapillomavirus (ε), and Xipapillomavirus (ξ) and an undesignated Papillomavirus genus (BPV7). The numbers at the internal nodes represent the bootstrap support values (percentages) determined for 1,000 replications. The scale bar indicates the number of nucleotide substitutions per site.