Hela cells are infected with HPV. So is it safe to work with them? What are the safety precautions?
Most guidelines for HeLa (and most cells of human origin) say they should be kept at a BSL2 level. For example, from a 2007 publication in Applied Biosafety:
Work with cell cultures from human or primate origin should generally be performed under BSL2 conditions. Containment level 1 may be considered if all manipulations occur in a Type II biosafety cabinet ...
ATCC general guidelines recommend BSL2 containment for the broad category covering HeLa:
- Biosafety Level 2
- Cell lines that harbor mycoplasma or any other BSL 2 agent (See: NOTE)
- Cell lines exposed to or transformed by a primate oncogenic virus
- Primate cell lines that contain viruses
- Cell lines carrying a part of certain viral genomes, even if whole virus is not released from the cell
Their specific page for HeLa also recommends BSL2, with the note "[Cells contain human papilloma virus]".
That said, HeLa cells have been very widely used, including for decades before modern lab safety practices were agreed on, and I'm not aware of any actual problem ever arising (including such amazing practices as injecting live HeLa cells into convict "volunteers" to see if cancers would appear - They did not).
So the answer to the question is that it is safe to work with HeLa cells, but that proper BSL2 lab practices should be followed.