A goal at the end of each half secured a youthful Latics side all three points in their reserve fixture with Wigan Athletic.
Jordan Bove put Latics ahead in the first half but Antelmi levelled the scores just after the break. Johnson had a penalty saved by Joel Coleman before John Pritchard fired Latics to victory in the dying minutes.
It was the visitors that dominated the early proceedings as Coleman had to be alert from a free kick. The goalkeeper saved well after Ryan Jennings was hacked down after a mazy run.
In what was a sunny afternoon at Chapel Road, the home side were being made to work by a strong Wigan side.
Against the run of play, the home side took the lead just before the break. Bove pounced on a mistake in the middle of the park and drove at the Wigan's defence before cooly slotting the ball past goalkeeper, Lee Nicholls.
Wigan started the second half brightly and were level five minutes after the break. Goalscorer Antelmi beat Coleman to the ball aerially and had the simplest of tap-ins to equalise for the visitors.
Instantly they had a chance to take the lead as a Wigan striker was brought down in the area and the referee awarded the spot kick. Johnson stepped up to take it but Coleman guessed the right way to deny the striker and was quickly back to his feet to stop the follow up.
The home side rallied and started to come back into the game. With chances falling to either side and time running out, Latics felt Wigan defender Wilson should have been dismissed for bringing down Jordache Walters as he raced through on goal.
The defender received a yellow card for his actions but Pritchard took the free kick and it sneaked under the wall to give the home side victory.
That victory now makes it two wins from two as Latics comfortably dispatched Walsall 4-0 a fortnight ago.