HARRISBURG, Pa. -- A young man who testified last year at Jerry Sandusky's child sexual abuse trial sued the former coach and Penn State on Thursday over what he said was nearly four years of sexual assault while in his early teens.

The lawsuit by the man known as Victim 9 in criminal court records was filed in Philadelphia Common Pleas Court after talks with the university failed to reach a settlement.

The lawsuit claims the boy, now 20 years old, would not have been victimized if university officials had properly handled other complaints about Sandusky.

"Penn State provided Sandusky the tools with which to ply the craft of a pedophile long after Sandusky's formal ties with the university were supposed to have been severed," the lawsuit said.

Victim 9's lawyers wrote that "it was the inviolable culture of financial and sporting success of Penn State football that made possible the horrific sexual abuse that forms the basis of this lawsuit."

A university spokesman declined comment, and a message left for a lawyer who has represented Sandusky in other civil litigation was not immediately returned.

The young man's lawyers called him John Doe D and asked that his identity not be disclosed. The Associated Press does not generally publish the names of sexual abuse victims.

"It's now clear that Penn State enabled Sandusky to sexually abuse more than 20 other children before Sandusky preyed on this boy," wrote the plaintiff's lawyer, Stephen E. Raynes. "Each of those tragic assaults provided Penn State with the opportunity to stop Sandusky, opportunities which Penn State squandered. We will learn through this lawsuit why that happened and what additional lessons Penn State should learn from this tragic episode in its history."

The lawsuit claims that the university knew or should have known, after officials fielded complaints about Sandusky in 1998 and 2001, that children such as Victim 9 were "endangered by Sandusky's predatory pedophilia."

During testimony at Sandusky's trial in June 2012, Victim 9 said Sandusky began by fondling him and degenerated into forced oral sex before several instances of rape in Sandusky's State College home. The lawsuit said the abuse took place between summer 2005 and fall 2009, when he was 16 years old.

He testified that his muffled screams went unheard by Sandusky's wife, Dottie, upstairs.

"He got real aggressive, and just forced me into it," he testified. "And I just went with it -- there was no fighting against it."

The lawsuit claims Sandusky's former boss, coach Joe Paterno, invited the boy and Sandusky to have lunch with him at Beaver Stadium and tour the stadium, despite the late coach "being alerted years earlier to Sandusky's sexual assault of young boys."

"Each time Sandusky and John Doe D encountered Paterno, Paterno greeted Sandusky, endorsing Sandusky's favored status with Penn State," the lawsuit stated.

Paterno was fired shortly after Sandusky's November 2011 arrest and died a few months later. A spokesman and lawyer for his family did not immediately return messages seeking comment.

The lawsuit is the first filed against Sandusky and the university since Penn State announced last month it was paying nearly $60 million to settle abuse claims by 26 young men. It's not clear how many, if any, suits are still pending against the school following those settlements.

Victim 9's lawyers said he has suffered depression, post-traumatic stress disorder, flashbacks of abuse at Sandusky's hands, sleep disturbance and other problems.

The lawsuit asserts an assault and battery claim against Sandusky. The university was sued for negligence and recklessness, tortious conduct, misrepresentation and infliction of emotional distress.

Six of the 45 counts for which Sandusky was convicted concerned Victim 9: two counts of involuntary deviate sexual intercourse, indecent assault, unlawful contact with a minor, corruption of minors and endangering a child's welfare.

Three former Penn State administrators currently await trial on charges they engaged in a criminal cover-up of complaints about Sandusky. Former president Graham Spanier, former vice president Gary Schultz and former athletic director Tim Curley all deny the allegations.

Curley renewed his efforts to dismiss the charges Thursday, arguing that investigators improperly relied on privileged attorney-client information between Curley and former university lawyer Cynthia Baldwin, who accompanied him to the grand jury.