Bovine Meat and Milk Factors

Bovine Meat and Milk Factors (BMMFs) are circular, single-stranded DNA molecules (cssDNAs), also termed plasmid-like, originally found in beef and cow's milk which have been linked to the development of cancer—particularly colorectal and breast cancer. They are formerly known as Slow Progressive Hidden INfections of variable X (SPHINX). Similar molecules have since been found in a much wider range of food. In 2022, a study examined whether BMMF occurred in foods that were not of taurine bovine origin. Numerous foods including chicken, pork, seafood, fruit, vegetables and grains were examined using PCR analysis. BMMF/SPHINX-like DNA was identified in plants, poultry, wild animals and seafood.

BMMF/SPHINX sequences are able to copy themselves in animal cells. They encode functional proteins that are expressed in some animal cells. Every BMMF/SPHINX contains at least a "Rep" open reading frame, which encodes a replication endonuclease that, in HEK 293TT cells, acts to replicate and retain the cssDNA. The cssDNA derive from bacteria in an outer membrane vesicle OMV and in vitro cross into human tissue culture cells, demonstrating the role of OMV in transport from bacterial to eucaryotic cells.

BMMF/SPHINX sequences are divided into four clades. Clades 1, 2, and 3 share sequence similarity with the plasmids of Acinetobacter baumannii. (A. baumanii regularly produces outer membrane vesicles containing these plasmids, and animal cells are known to take up these vesicles.) Clade 4 shares sequence similarity with Gemycircularvirus.