Johnny is a very different character than Niko, with a very different background. I can't go into too much detail on the story, because we try not to give away too much plot before the game is released. But I can say that the story will show you a different side of Liberty City.
A USA Today report is the setting for the announcement of Grand Theft Auto IV's long-awaited piece of downloadable content. Titled "Lost and Damned", the DLC will be available on February 17, and will leave Niko's story behind (though he will make a few cameo appearances) to follow the exploits of Johnny Klebitz, a member of the Lost biker gang that the game's radio channels liked to talk about so much. Rockstar's Dan Houser:
The USA Today report also says the expansion will "let you download more sandbox time", Houser elaborating "We feel like we've only scratched the surface in terms of the depth and detail in [Liberty City]". 'Grand Theft Auto' yields road to the 'Lost and Damned' [USA Today]