1 Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada V6T1Z3; Department of Microbiology and Immunology, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt 21521.
2 Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada V6T1Z3.
3 Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada V6T1Z3. Electronic address: rachelf@mail.ubc.ca.