First Insights into the Occurrence of Circular Single-Stranded DNA Genomes in Asian and African Cattle

Abstract

Circular replicase-encoding single-stranded (CRESS) DNA viruses and other circular DNA agents are increasingly found in various samples and animals. A specific class of these agents—termed bovine meat and milk factors (BMMF)—has been supposed to act as a factor in indirect carcinogenesis in humans. Initial observations attributed the BMMF to European cattle breeds and foodstuffs produced thereof. In the present study, blood and fecal samples from African and Asian cattle were examined. BMMF molecules and genomoviruses were detected in all bovids under study. The majority (79%) of the 29 circular elements could be assigned to BMMF groups 1 and 2, whereas CRESS viruses of the family Genomoviridae accounted for the smaller part (21%). Two genomoviruses belong to the genus Gemykibivirus and one to the genus Gemykrogvirus. The remaining three might be considered as novel species within the genus Gemycircularvirus. The majority of all isolated molecules originated from fecal samples, whereas only three derived from blood. The results from this study expand our knowledge on the diversity and presence of circular DNA in different ruminants that serve for food production in many countries over the world.

Current Research on Small Circular Molecules: A Comprehensive Overview on SPHINX/BMMF

“…Clearly, these are unsolved questions which should be addressed in further studies. [10,13,14,18,19,30]. Schematic image of the regulatory region (framed), which potentially includes oriT (green) [19], AT-rich region (potential origin of replication, grey) [19,31] and iteron-like tandem repeats (ITRs, orange) [19].…”

“…In order to investigate whether SPHINX/BMMFs are only present in B. taurus -derived food products, further food products and animal samples were examined [ 13 , 14 , 15 , 16 , 18 , 19 ]. All these studies are based on the methods of isolation and detection of SPHINX/BMMF DNA previously described by the DKFZ, using SPHINX/BMMF-specific primers to amplify these molecules from Round Circle Amplification (RCA)-enriched food DNA samples.…”

“…In our further investigations, we showed that complete circular DNAs with high homologies to SPHINX/BMMF could also be detected in foods from animals and plants, including pork, wild boar, chicken meat, Alaska pollock, pangasius, black tiger shrimp, apple, carrot, and sprouts from alfalfa, radish, and broccoli [ 19 ]. Further SPHINX/BMMF molecules had been isolated from blood and feces of African and Asian cattle [ 18 ].…”

“… Overview of SPHINX/BMMF group 1 and 2 molecules. ( a ) Summary of the properties of SPHINX/BMMF group 1 molecules known to date and illustration of two typical molecules including one (Rep ORF in blue) or two ORFs (second ORF in light blue) [ 10 , 13 , 14 , 18 , 19 , 30 ]. Schematic image of the regulatory region (framed), which potentially includes ori T (green) [ 19 ], AT-rich region (potential origin of replication, grey) [ 19 , 31 ] and iteron-like tandem repeats (ITRs, orange) [ 19 ].…”

“…Then, in 2019, a press conference held by the German Cancer Research Center (DKFZ) attracted attention, in which the BMMFs were presented as “factors” or “novel pathogens” originating from European domestic cattle ( Bos taurus ) and which were stated to be involved in the development of cancer [ 11 ]. As there were considerable doubts regarding the interpretation of existing data by the DKFZ, several further studies were subsequently published by various groups [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”