The Avengers have re-assembled and they’ve brought some friends with them in honour of teenager super-fan Josh, who is battling leukaemia.

17-year-old Josh was diagnosed with stage four glioblastoma at the age of 15 – the same aggressive form of cancer that recently took Senator John McCain.

Chris Evans (Captain America), Chris Pratt (Star Lord), Tom Holland (Spider-Man), Ryan Reynolds (Deadpool) and Hugh Jackman (Wolverine) are amongst those who have reached out to Josh on social media after his mother started a campaign to “try to get as many celebrities to message him while he is still with us" - and the response has already been overwhelming.

Ryan Reynolds kicked things off, introducing himself as “Uncle Deadpool” and delivering a heartfelt message in which he says “you have more courage and more strength in your pinkie finger than any superhero does in their entire body.” He then added: "We love you, I love you, we're thinking about you, Deadpool is thinking about you - maximum effort and hang in there, buddy. Josh’s mother shared the video on Twitter with the caption “Such a special man with a huge heart. Thank you, Ryan Reynolds – Josh loves you so much for brightening up his days.”

Hugh Jackman followed suite and sent Josh a video saying “I just want you to know that I’m thinking about you and your family and friends. I’m sending you lots of positive thoughts. Keep fighting, man.” Josh’s mother took to twitter to thank Jackman for “putting a smile on my brave son’s face.”

Captain America himself, Chris Evans was up next and took to twitter in a comical video in which he acknowledges that Josh is “probably a bigger fan of Deadpool than of Captain America” but accepted defeat by saying “I’ll give it you; he’s funny. He gets to make the jokes! I don’t get to make the jokes.”

British actor, Tom Holland – who plays Spider-Man – sent his best wishes and told Josh that “I just wanted to let you know that I’m thinking about you, everyone at Marvel are thinking about you and we send you all our love.”

Guardians of the Galaxy star Chris Pratt, a well-known Christian who is open about his religious beliefs, reached out to Josh and said “I’m thinking about you, I love you and I’m praying for you and your mom” and stating that, while he plays a superhero in the movies, the real heroes are “young people like you who have to face challenges and do so with the bravery you do.”

God of Thunder, Thor (Chris Hemsworth) is one of the latest celebrities to offer his support to Josh and his mother, in a video in which he calls Josh a “legend” and offers all of his love and support, saying that everyone in the world is sending their love.

The outpouring of love and support for Josh has been amazing and his mother is hoping that other superhero actors and various other celebrities join the campaign, as many of those who have already sent messages have encouraged others to do the same, with Robert Downey Jr, Samuel L Jackson and Dwayne “The Rock” Johnson amongst those who have been asked to show their support.

If you want to follow Josh’s journey and send him your own best wishes, follow @josh_braveheart on Twitter.