Our laboratory is interested in protein-protein interactions, particularly those mediating immune recognition. We use X-ray crystallography and biochemistry to study purified proteins, and electron and confocal microscopy to examine protein complexes in cells. Following upon our electron tomography (ET) studies of receptor-mediated transport of IgG across intestinal epithelial cells, we are now conducting ET imaging studies of HIV-1-infected human tissue and equivalent samples from humanized mouse models to characterize sites of infection at high resolution during a natural infection. We are focusing on gut-associated lymphoid tissue, which is an early site for HIV replication and CD4 T-cell depletion and using immuno-EM to identify HIV virions and cell subtypes of interest (e.g., the Th17 subset of CD4 T-cells) to determine which cells are infected and subsequently involved in large amounts of viral budding and dissemination). Topics that can be addressed by 3-D imaging of HIV-infected tissues include: (i) quantitative analysis of numbers and types of infected cells, including their positions with respect to each other and within the tissue as a function of the length of infection, viral load, and the presence or absence of anti-retroviral drugs; (ii) quantitative analyses of global viral location and state (i.e., intracellular versus extracellular locations, numbers of fusing versus budding virions, and immature versus mature viruses), again as a function of length of infection and the presence or absence of anti-retroviral drugs; (iii) mapping routes of virus trafficking in infected cells with respect to cell boundaries and how the ultrastructure of those cells is altered during the course of the HIV replication cycle; (iv) comparisons of budding of HIV from the plasma membrane versus into intracellular locations as a function of cell type; and (v) quantitative comparisons of virus transmission during the course of infection, which may be pertinent to understanding the propensity for viral spread via cell-to-cell transmission or infection by free virions within different tissues or organs. Bjorkman directs the Tissue EM Core.
Pamela Bjorkman, PhD
Howard Hughes Medical Institute
Division of Biology, 114-96
California Institute of Technology
1200 E. California Blvd.
Pasadena, CA 91125
Lab webpage: http://www.its.caltech.edu/~bjorker/