Detection and Characterisation of Picobirnaviruses in Human and Rabbit Faeces

Gallimore, Christopher Ian (1995). Detection and Characterisation of Picobirnaviruses in Human and Rabbit Faeces. MPhil thesis The Open University.



Human faecal samples were screened by nucleic acid extraction and polyacrylamide gel electrophoresis (PAGE) for the presence of novel dsRNA viruses. A genome typical of a bisegmented dsRNA virus termed picobirnavirus (PBV) was detected in 5 to 15% of about one thousand human faecal samples. The PBV genome consists of two equimolar segments of dsRNA of approximately 2.45 and 1.75 Kilo base pairs (Kbp) in size. During studies attempting to pass a human PBV (HPBV) strain into rabbits, a coincidental rabbit PBV (RPBV) strain was detected, and subsequently three further unique rabbit strains were detected in newly weaned rabbits. An atypical PBV (APBV) associated with Cryptosporidium positive human faecal samples was detected in 20/54 (37%) of samples. The genome of the APBV was 1.75 and 1.55 Kbp. in size and all strains detected were virtually identical.

Direct electron microscopy was performed on human faecal samples and small round featureless PBV-like particles with a diameter of 35-40nm were seen. Rabbit PBV-like particles were also detected in PAGE positive CsCl gradient fractions and peaked at a buoyant density of 1.395 g/ml was obtained.

An immune response temporally associated with virus excretion was demonstrated in one rabbit by immune electron microscopy. Two antigenically and genomically different strains were shown to be circulating in rabbits.

Epidemiological studies to determine the prevalence of PBV in several groups of patient samples including; gastroenteritis outbreaks occurring between 1982-93, hospitalised patients, HIV-infected patients and sporadic cases of gastroenteritis, showed that PBV are widely distributed, but no association with disease was demonstrated.

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