England coach Eddie Jones named uncapped number eight Nathan Hughes and lock Mike Williams on Monday in a 45-man provisional pre-season training squad.
The group will meet from August 6-8 to prepare for tests against South Africa, Fiji, Argentina and Australia later this year.
Fijian-born Hughes, 25, qualified to play for England this year after three seasons with Premiership club Wasps. Williams, 24, was born in Zimbabwe and joined Leicester in 2015.
Uncapped back-row forward Josh Beaumont, prop Kyle Sinckler and centre Ben Te’o, a New Zealand-born former rugby league player, were also included in the squad.
Flyhalf Danny Cipriani, centre Luther Burrell and winger Chris Ashton were notable omissions.
“This camp sets the scene for November,” Jones told the English RFU website.
“It’s important to catch up with the players prior to the start of the season and continue to put our plans in place.”
Jones led England to this year’s Six Nations title and a 3-0 series win in Australia after taking over as coach from Stuart Lancaster, lifting them to second in the world rankings behind world champions New Zealand.
“The long-term strategy for England is to develop a side who can be the most dominant team in world rugby, so we’ve chosen a number of new faces to attend this camp on the form they have shown recently or the potential we see in them,” Jones said.
England have not beaten South Africa since 2006.
“Not a single player who will attend the pre-season camp has played in a side that has ever beaten South Africa,” Jones said.
“We cannot afford to have any complacency in our approach to this test.”
Josh Beaumont, Dan Cole, Luke Cowan-Dickie, Jack Clifford, Will Evans, Charlie Ewels, Jamie George, Ellis Genge, Teimana Harrison, Dylan Hartley, James Haskell, Paul Hill, Nathan Hughes, Maro Itoje, George Kruis, Joe Launchbury, Courtney Lawes, Joe Marler, Matt Mullan, Chris Robshaw, Kyle Sinckler, Billy Vunipola, Mako Vunipola, Mike Williams, Tom Youngs
Mike Brown, Danny Care, Elliot Daly, Owen Farrell, George Ford, Alex Goode, Mike Haley, Jonathan Joseph, Joe Marchant, Jonny May, Jack Nowell, Dan Robson, Semesa Rokoduguni, Joe Simpson, Henry Slade, Ben Te’o, Manu Tuilagi, Anthony Watson, Marland Yarde, Ben Youngs