Major Areas of Interest
- Development and application of novel imaging methods for analysis of tissue cells
- T cell dynamics in secondary lymphoid organs in natural infection (HIV/SIV) and after vaccination
- Generating “tissue imaging signatures” in cancer and cancer/HIV
The mission of the Tissue Analysis Core is the development, optimization and application of cutting-edge imaging assays for the analysis of human and nonhuman primate (NHP) tissues in support of VRC goals.
Imaging methodologies are a prerequisite for the understanding of:
- the spatial analysis of tissue immune cells and with respect to tissue structure
- the local interactions between immune cells, tissue stromal cells and tissue-expressed antigens (pathogens, cancer, self-antigens)
- the role of local inflammatory mediators for the dynamics of tissue immune cells
A comprehensive tissue analysis requires the application of complementary technologies allowing for the characterization of phenotype, localization, function and molecular signatures of cells under investigation. Merging cutting-edge technologies like multidimensional imaging, multiparameter flow cytometry and deep sequencing allows for the generation of “imaging signatures” that could provide information about viral persistence in specific tissue areas-sanctuaries and assist in the discovery of biomarkers for disease progression and interventional strategies with specific immunotherapies and vaccines.
Current technologies employed in the Tissue Analysis Core include:
- multispectral confocal imaging (A),
- RNAscope methodology that allows for the simultaneous detection of mRNA and several protein markers (B),
- live imaging and v) TIRF microscopy (C).
Several analytical tools (Imaris, Voloom, Histo-cytometry platform and in house developed algorithms) are used for the quantitative analysis of the obtained imaging objects.
Dr. Petrovas has been working in the field of HIV/SIV pathogenesis for more than 15 years. He obtained his Ph.D. in immunology studying anti-phospholipid antibodies in autoimmunity and HIV at the School of Medicine, National University of Athens, Greece. He pursued post-doctoral work at the Department of Biochemistry, Boston University and Department of Microbiology and Immunology, Drexel University before he joined the Immunology Laboratory at VRC in 2005. His previous work focused on the mechanisms mediating the “exhaustion” of SIV/HIV- specific CD8 T cells and he was the first to describe PD-1 as a mediator of SIV/HIV-specific CD8 T cell survival. More recently, his research has been focused on the dynamics of CD4 and CD8 T cells at tissue level and particularly in the lymph node follicles in HIV and SIV infection. His work was the first to describe the phenotype, localization, molecular profile and dynamics of Tfh CD4 T cells in acute and chronic SIV infection. Currently, he is characterizing the dynamics of tissue immune cells in HIV/SIV and cancer and developing tools to understand the interplay between inflammation, adaptive immunity and tissue antigens.
Padhan K, Moysi E, Noto A, Chassiakos A, Ghneim K, Perra MM, Papaioannou V, Fabozzi G, Ambrozak D, Poultsidi A, Loannou M, Fenwick C, Sekaly RP, Pantaleo G, Koup RA, Petrovas C. Acquisition of optimal TFH cell function is defined by specific molecular, positional and TCR dynamic signatures. Proc Natl Acad Sci USA (accepted).
Potter EL, Gideon HP, Tkachev V, Fabozzi G, Chassiakos A, Petrovas C, Darrah PA, Lin PL, Foulds KE, Kean LS, Flynn JL, Roederer M. Measurement of leukocyte trafficking kinetics in macaques by serial intravascular staining. Sci Transl Med. 2021 Jan 13;13(576):eabb4582.
Shankwitz K, Pallikkuth S, Sirupangi T, Kirk Kvistad D, Russel KB, Pahwa R, Gama L, Koup RA, Pan L, Villinger F, Pahwa S, Petrovas C. Compromised steady-state germinal center activity with age in nonhuman primates. Aging Cell. 2020 Feb;19(2):e13087.
Austin JW, Buckner CM, Kardava L, Wang W, Zhang X, Melson VA, Swanson RG, Martins AJ, Zhou JQ, Hoehn KB, Fisk JN, Dimopoulos Y, Chassiakos A, O'Dell S, Smelkinson MG, Seamon CA, Kwan RW, Sneller MC, Pittaluga S, Doria-Rose NA, McDermott A, Li Y, Chun TW, Kleinstein SH, Tsang JS, Petrovas C, Moir S. Overexpression of T-bet in HIV infection is associated with accumulation of B cells outside germinal centers and poor affinity maturation. Sci Transl Med. 2019 Nov 27;11(520):eaax0904.
Ferrando-Martinez S, Moysi E, Pegu A, Andrews S, Nganou Makamdop K, Ambrozak D, McDermott AB, Palesch D, Paiardini M, Pavlakis GN, Brenchley JM, Douek D, Mascola JR, Petrovas C, Koup RA. Accumulation of follicular CD8+ T cells in pathogenic SIV infection. J Clin Invest. 2018 May 1;128(5):2089-2103.