Identification of a novel deltavirus in Boa constrictor
Human hepatitis D virus (hHDV) forms the genus Deltavirus which has not been assigned to any virus family. hHDV is a satellite virus and needs hepatitis B virus (HBV) to make infectious particles. Deltaviruses are thought to have evolved in humans, since they have thus far not been identified elsewhere. Herein we report, prompted by a recent observation of HDV-like agent in birds, the identification of a deltavirus in a snake (Boa constrictor) designated as snake-HDV (sHDV). The circular 1711 nt RNA genome of the newly identified virus resembles hHDV in its coding strategy and size. We discovered sHDV when performing a meta-transcriptomic study on brain samples of two boas with central nervous system signs. We did not identify accompanying HBV-like sequences in the samples. By sequence comparison, the putative hepatitis D antigen (HDAg) of sHDV, encoded by one of the two open reading frames (ORFs), is roughly 50% identical to the previously known HDAgs. We used antiserum raised against recombinant snake HDAg to demonstrate a broad viral target cell spectrum, ranging from neurons over epithelial cells to leukocytes. Using RT-PCR, we detected sHDV RNA also in the liver and blood of the two snakes and could show sHDV infection not only in two of their juvenile offspring, but also in a water python (Liasis mackloti savuensis) in the same snake colony, indicating potentially vertical and horizontal transmission. The finding of abundant sHDAg in several tissues suggests that sHDV actively replicated in the studied animals. Our findings suggest that sHDV spread may not be restricted to hepadnavirus co-infection. This would imply that deltaviruses may employ other enveloped viruses for producing infectious particles.