LAS VEGAS — A Nevada jury was asked Wednesday to hold the state's largest health management company responsible for up to $1 billion in damages because two women contracted incurable hepatitis C during treatment at a Las Vegas outpatient medical clinic later blamed for an outbreak called the largest in U.S. history. In closing arguments, lawyers for plaintiffs Helen Meyer and Bonnie Brunson accused Health Plan of Nevada and parent company Sierra Health Services Inc. executives of disregarding evidence that clinic owner Dr. Dipak Desai had a history of endangering patients at his endoscopy clinics.