Linda Grosche

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B2 Control of HSV-1 specific replication and transmission mechanisms in human dentritic cells

Principal investigator
Alexander Steinkasserer

Mentor
Manfred Marschall

Adhesion and migration of herpesviral-infected dendritic cells

Leukocyte migration is pivotal for initiation of immune responses, while dendritic cells (DCs) constitute a group of leukocytes operating at the interface of innate and adaptive immunity with specialization for the activation of lymphocytes. Immature DCs (iDCs) reside as sessile and very adhesive cells in peripheral tissues getting activated by antigen uptake or stimulation of pattern recognition receptors (PRRs). This is accompanied by a maturation process with changes in the surface receptor repertoire and motility. Mature DCs (mDCs) loosen their adhesions and migrate chemotactically from the site of infection to secondary lymphatic organs (SLOs). This migration process is a prerequisite for activation of T- and B-cells in order to induce an adaptive immune response. Considering the central role of DCs in the orchestration of immune responses, they constitute potential targets for pathogen immune-evasion strategies. Indeed, an impairment of proper DC migration by herpes simplex virus type-1 (HSV-1) has previously been shown.
This project is focused on the inhibition of DC migration, in particular by increasing the activity of the β2-integrin LFA-1 (lymphocyte function-associated antigen 1) in HSV-1 infected DCs. This is achieved by stabilizing the cytohesin-1-mediated activation of LFA-1 by degradation of CYTIP (cytohesin-1 interacting protein), which is a negative regulator of the cytohesin-1-mediated activation of LFA-1.
A specific focus of this project is to elucidate the exact molecular mechanisms of HSV-1-induced CYTIP degradation and PI3K (phosphoinositide 3-kinase) activation, which was also observed in HSV-1 infected DCs. Furthermore, the HSV-1 gene product responsible for the observed phenotype in infected DCs is of great interest, while first experiments indicated an involvement of HSV-1 ICP27 and late gene products. A second aim is to elucidate whether this immune escape mechanism is conserved among herpesviridae, thus the human cytomegalovirus (HCMV) is analyzed regarding a modulation of DC adhesion and migration. Determination of cytohesin-1, CYTIP and PI3K protein levels in mock or HCMV infected cells will provide evidence whether HCMV similarly regulates DC migration.

 

Figure: The β2 integrin LFA-1 and its regulation by cytohesin-1 and CYTIP in uninfected or infected DCs. A-C Cytohesin-1 directly interacts with membrane bound PIP3 and the intracellular CD18 domain of LFA-1 resulting in increased LFA-1 affinity, which promotes adhesion to its ligand. PI3K activation - by e.g. CCR7 signaling - leads to a polarized PIP3 accumulation at the plasma membrane resulting in polarized LFA-1 activation and directed migration, following e.g. a CCL19 gradient. CYTIP negatively regulates cytohesin-1-induced LFA-1-activation by its binding with subsequently translocation of the cytohesin-1/CYTIP-complex to the cytosol, thereby diminishing LFA-1 affinity and ultimately adhesion. D HSV-1 induces a proteasomal degradation of CYTIP, thus stabilizing the LFA-1-mediated activation by constitutive binding of cytohesin-1 leading to impaired migration of DCs. Furthermore HSV-1 infected DCs possess increased levels of activated phosphor-PI3K, leading to non-polarized PIP3 accumulation.

 

Publications

 

Presentations

October 2016 8th Annual Retreat, Erlangen School of Molecular Communication, Schloss Schney, Lichtenfels, Germany
”Adhesion and migration of herpesviral-infected dendritic cells”
Talk
     
April 2016 26th Annual Meeting of the Society for Virology (GfV), Münster, Germany
”Modulation of Dendritic Cell Adhesion and Migration by Herpes Simplex Virus Type 1 and Human Cytomegalovirus”
Poster
     
October 2015 2nd International SFB 796 Conference: Mechanisms of microbial host cell manipulation: From plants to humans, Erlangen, Germany
”Modulation of Dendritic Cell Adhesion and Migration by Herpes Simplex Virus Type 1 and Human Cytomegalovirus”
Poster
     
July 2015 7th Annual Retreat, Erlangen School of Molecular Communication, Schloss Hirschberg, Beilngries, Germany
”Adhesion and migration of herpesviral-infected dendritic cells”
Talk
     
July 2015 40. IHW ("International Herpesvirus Workshop"), Boise, Idaho, USA
Modulation of Dendritic Cell Adhesion and Migration by Herpes Simplex Virus Type 1
Poster