Infection of neotropical non-human primates with bat deltaviruses

Background & Aims: The origin of hepatitis D virus (HDV) and related deltaviruses remains elusive. Contrarily, hepatitis B virus, HDV's helper virus, and related hepadnaviruses display long-term association with primates. Current data suggest cross-order host shifts as a common mechanism in deltavirus ecology, but corroborative evidence is lacking. Here, we aimed to elucidate the genealogy of primate deltaviruses. Methods: We screened 961 non-human primate (NHP) liver specimens obtained in Brazil between 2017-2023 for deltaviruses and hepadnaviruses. Complete deltaviral genomes were obtained via overlapping nested RT-PCR, cloned, expressed in vitro and analyzed via immunoblot and immunofluorescence analysis. Anti-deltaviral antibodies in NHP and vampire bats were detected via immunofluorescence analysis. Results: We detected deltaviruses in two NHP. Complete deltaviral genomes exhibited common features including high self-complementarity, genomic and antigenomic ribozymes, and a delta antigen open reading frame. NHP deltaviruses were phylogenetically related to viruses found in common vampire bats. The NHP deltaviruses replicated in vitro without the expression of a large delta antigen. We did not detect anti-deltaviral antibodies in NHP sera (0/249), in contrast to sera from common vampire bats (7/112; 6.2%, 95% CI: 1.8-10.7), indicating viral circulation in bats. Ancestral state reconstruction suggested a bat origin of NHP deltaviruses. Targeted screening excluded a coinfecting hepadnavirus in the deltavirus-positive animals but led to the discovery of a hepadnavirus, corroborating a non-recent introduction of hepadnaviruses into the primate stem-lineage. Conclusions: Our data are consistent with deltaviral cross-order host shifts and suggestive of the susceptibility of primates to reservoir-bound deltaviruses, lending credibility to a zoonotic origin of HDV.