Well How About That

Weed Could Block H.I.V.’s Spread. No, Seriously.

The changes that THC produces in the gut a process formally known as “microbial translocation,” isn’t as complicated as it sounds. During HIV infection, one of the earliest effects is that the virus spreads rapidly throughout the body and kills a significant part of cells in the gut and intestine. This activity damages the gut in a way that allows the HIV to leak through the cell wall of the intestines and into the bloodstream.
When THC is introduced into this environment, it activates the CB2 receptors in the intestines to build new, healthy bacterial cells that block the virus from leaking through the cell walls. In other words, the body works hard to keep bad stuff in the intestines and the good stuff out.
Put another way: HIV kills the cells that protect the walls— THC brings them back. Reducing the amount of the virus in the lower intestines could then help keep uninfected people uninfected.

Healing guts.  That explains a whole lot.

here's the abstract