All Stars, under former Hull KR coach Tim Sheens will provide the opposition at Warrington in the first of England’s two World Cup warm-up matches.
McGillvary, of Huddersfield Giants, was named in England’s initial 24-man squad, but dropped when it was reduced to 19.
Hull FC’s Connor has previously played for England and Leeming, of Leeds Rhinos, trained with them earlier this year and is a member of the second-string Knights squad.
Sheens, a World Cup winner with the 2013 Kangaroos, has confirmed Leeds forward Matt Prior will be co-captain, alongside Jackson Hastings of Wigan Warriors.
The squad includes players from nine different clubs, including Championship outfit Featherstone Rovers, whose ex-Castleford forward Junior Moors will feature.
Hull KR players were stood down after a Covid outbreak led to Friday's scheduled game against St Helens being postponed.
But no Saints players are included, despite them not having a game this weekend.
Sheens, said: “When this concept was created the aim was to give England a highly intense match as part of their preparations ahead of the Rugby League World Cup 2021.
“I’m confident we’ve assembled a squad that can do that.
“As it was always the case that Shaun [Wane] would get first pick for England, we obviously had to wait and work within the guidelines when selecting players.
“I’m really looking forward to working with them – and I hope we’re all going to enjoy the experience, getting to know some new people and trying out some new combinations.
“Also, the match is being played to help raise funds for the Mose Masoe Foundation and the players will take great pride in wearing the Mose-inspired jersey, which will no doubt will add to their motivation to perform well.”
The Combined Nations All Stars squad is: Jake Connor (Hull FC), Kenny Edwards (Huddersfield Giants), Jackson Hastings (Wigan Warriors), Liam Kay (Wakefield Trinity), Kruise Leeming (Leeds Rhinos), Ricky Leutele (Huddersfield Giants), Peter Mata'utia (Castleford Tigers), Suaia Matagi (Castleford Tigers), Jermaine McGillvary (Huddersfield Giants), Junior Moors (Featherstone Rovers), Pauli Pauli (Salford Red Devils), Nathan Peats (Leigh Centurions), Matt Prior (Leeds Rhinos), Chris Satae (Hull FC), Andre Savelio (Hull FC), Aidan Sezer (Huddersfield Giants), Ken Sio (Salford Red Devils), Kelepi Tanginoa (Wakefield Trinity), Luke Yates (Huddersfield Giants).