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Research group "Retrovirus Transmission" - Dr. rer. nat. Xaver Sewald

Seeing is believing - visualizing retrovirus transmission and dissemination
Retroviruses can efficiently spread between leukocytes in a cell contact-dependent manner (Fig 1). They take advantage of inherent immune cell properties such as dynamic cell migration and tight cell-cell contact formation to disseminate within target cell populations in vitro and in vivo. Our laboratory is interested in the underlying mechanism of retrovirus cell-to-cell transmission. In particular, we want to understand how retroviruses exploit the cell and tissue physiology to spread in living organisms. Using visual approaches we are eager to study the transmission of retroviruses between cells through tight cell-cell contacts called virological (Fig. 1B) or infectious synapses (Fig. 1C). State-of-the-art imaging approaches such as live cell confocal microscopy and single cell analysis tools are used to reveal the function of cellular and viral proteins in retrovirus cell-to-cell transmission. In addition, multi-photon intravital microscopy is applied to follow retrovirus infection in lymphoid and mucosal tissues under physiological conditions in vivo. We aim to understand how the tissue physiology and tissue-specific cell populations support retroviruses to establish infection and contribute to their systemic dissemination in the host organism.

Figure 1: Concepts of retrovirus transmission between cells

1. Mechanism of retrovirus cell-to-cell transmission

We study cell-to-cell transmission of the model retrovirus murine leukemia virus (MLV) between relevant primary leukocytes in vitro. Using imaging approaches such as spinning disc confocal microscopy we investigate cell-cell interactions as well as dynamics of viral and cellular proteins in retrovirus-infected primary leukocytes during cell-to-cell transmission. In particular, we are interested in the subcellular distribution of proteins in migrating MLV-infected cells and during phases of virological synapse initiation, stabilization, as well as termination. Using custom-made microwell slides for live cell microscopy, we gain unique insights into the mechanism of how cell contacts are initiated and subsequently result in the formation of virological synapses for retrovirus transfer and infection. This novel experimental approach allows a systematic population analysis of retrovirus cell-to-cell transmission at single cell resolution.

Figure 2: Cell-cell contact (virological synapse) between lymphocytes during retrovirus transmission

2. Retrovirus transmission in vivo

We are establishing platforms for imaging retroviral infection in small animals. Applying multi-photon intravital microscopy (MP-IVM), we are visualizing different steps during retrovirus infection in vivo. This state-of-the-art technique allows us to follow virus particles and infected cells directly in lymphoid and mucosal tissues of the host organism. In addition to the studies of the model retrovirus murine leukemia virus (MLV) within its natural murine host, we team up with the research group of Prof. Keppler to investigate HIV infection using humanized mouse models. Together with multi-colour flow cytometry, immunohistochemistry and non-invasive in vivo bioluminescence imaging we tackle the following questions:

•    Characterize how retroviruses establish infection of the host
•    Explore the mechanism of retrovirus transmission between cells in vivo
•    Elucidate the systemic spread of retrovirus infection in living organisms

Movie 1: MLV-infected lymphocytes in vivo. Extended focus projection of images acquired by MP-IVM showing a lymph node 2 days after infection with fluorescent MLV. MLV-infected B-1 cells (red) express MLV capsid Gag-GFP. ROIs represent examples of stable cell-cell contacts (virological synapses) for virus transmission. The movie is played as time lapse.

Current Group Members

Dr. Xaver Sewald, PhD
Email: sewald(at)mvp.uni-muenchen.de
Phone: +49 89 2180 78136

Rebecca Engels, PhD student
Email: engels(at)mvp.uni-muenchen.de
Phone: +49 89 2180 78123

Florian Weber, PhD student
Email: florian.weber(at)mvp.uni-muenchen.de
Phone: +49 89 2180 78123

Selected publications

Sewald X., Motamedi N., W. Mothes (2016).  Viruses exploit the tissue physiology of the host to spread in vivo. Curr Opin Cell Biol., 41:81-90

Sewald X.*, Ladinsky M., Uchil P., Beloor J., Pi R., Herrmann C., Motamedi N., Murooka T., Brehm M., Greiner D., Shultz L., Mempel T., Bjorkman P., Kumar P.*, W. Mothes* (2015). Retroviruses use CD169-mediated trans-infection of permissive lymphocytes to establish infection. Science, 350(6260):563-7 * corresponding author

Li F., Sewald X., Jin J., Sherer N., W. Mothes (2014). Murine leukemia virus Gag localizes to the uropod of migrating primary lymphocytes. Journal of Virology, 88(18):10541-55.

Sewald X., Gonzalez D.G., Haberman A.M., W. Mothes (2012). In Vivo Imaging of Virological Synapses. Nature Communications, 3:1320.

 For a complete publication list follow this link to Pubmed.

Contact

Dr. Xaver Sewald
Max von Pettenkofer Institute, Virology
National Reference Center for Retroviruses
Faculty of Medicine
LMU München
Feodor-Lynenstraße 23
81377 Munich, Germany

Tel.: 089 2180 78136
sewald(at)mvp.uni-muenchen.de