Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA. eoghanh@stanford.edu|Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA. eoghanh@stanford.edu|Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA. eoghanh@stanford.edu|Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA. eoghanh@stanford.edu|Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA. eoghanh@stanford.edu