By Sinéad Carew and Ankika Biswas Dec 21 (Reuters) - Wall Street's main stock indexes closed higher on Wednesday with help from upbeat Nike NKE.N and FedEx FDX.N quarterly earnings, as well as improving consumer confidence and easing inflation expectations from investors. It's been helped by upbeat corporate commentary and an improvement in consumer confidence," said Angelo Kourkafas, investment strategist at Edward Jones in St. Louis referring to Nike and FedEx. Still, Wednesday's data also showed that U.S. existing home sales slumped 7.7% to a 2-1/2-year low in November as the housing market was hurt by higher mortgage rates.