In medium bowl, whisk first 3 ingredients; season. In large pot of boiling salted water, cook pasta to al dente. Drain, reserving 1 1/4 cups cooking water. In pot, stir cooked ziti, pasta water, cream cheese, blue cheese and celery over medium-low, stirring, until smooth, about 5 minutes. Stir in chicken; season. Serve pasta with hot-sauce mixture.