Sam Stejskal, Paul Tenorio and Jeff Rueter of The Athletic first broke the news on Wednesday. They note the agreement could reach up to $2 million and the Rapids will retain a sell-on clause.
The Rapids had been fielding offers for Vines from Europe for some time, including other Belgian clubs, German sides as well as Spain, sources say.
Vines, who just turned 22 at the end of May, broke into the first team as their first choice left back in 2019 and hasn't looked back. He has made 53 MLS appearances and earned his senior debut with the US national team, where he is currently with his country at the Gold Cup. He scored his first USMNT goal in their 1-0 win over Haiti to open the tournament.
The left back signed a five-year contract extension prior to the season starting, but it was always likely he'd be transferred to Europe early in the contract when the right opportunity presented itself.
Antwerp finished second during the regular season of the Belgian league and qualified for the playoff round of the Europa League.
Vines would leave a big hole for the Rapids as Colorado will have to replace his minutes at left back. With Vines on international duty, center back Auston Trusty filled the role. With the Secondary Transfer Window open another few weeks, the club could seek further reinforcements externally.