Typically the major threats from canniblism are bacteria, viruses, fungus, parasites and prions. The bacteria, viruses, fungus and parasites shouldn't exist under properly maintained lab conditions. But prions are just misfolded proteins. They happen rarely and typically they are quarantined in the cell they were produced in. A number of things have to go very, very wrong for them to get out into your body from your own cells. However, eating and digesting cells can let out the prions they contain. Once they get out they'll start triggering other proteins to misfold but only if the right materials are present and if the prion came from human tissue you can be sure they are.

The human immune system is incredible, it has impressive countermeasures for almost anything you could think of. Heck it'll even attack solid objects that get stuck inside you. If you get shot by a bullet and don't get it removed (not recommended) your body will layer by layer eat that bullet. Slowly dissolving it and passing it into your blood so your kidneys can filter it and you can piss out that bullet over the course of decades. (Though having a bunch more metal in your blood causes its own problems). Your body has a response to just about everything including cancer which to get anywhere has to have some mutations to deceive your immune system.

Your body has no answer to prions whatsoever. Your body puts up no fight. If you are infected by a prion disease you are going to die. There is no vaccine, no cure, no treatment.

Once symptoms appear you'll have at most a few years if your very lucky but more likely a few months. Most prion diseases attack the brain. (side note; don't eat the brains of any animal regardless of circumstances)

Will perfectly sterile lab conditions eliminate prions as a concern? No If anything it might be possible that growing the meat artificially might result in more misfolded proteins. I'd still happily eat lab-grown animal meat. But lab-grown human meat? No thank you