Viruses
are nanoscale particles that infect cells of all living organisms to replicate
and spread. During the infection process, the plasma membrane plays a key role
as it acts as a barrier that needs to be crossed both during viral entry and
egress. It contains attachments factors and receptors that the virus exploits
in order to bind to the cell surface and enter the cell. Understanding the
mechanisms regulating these virus-cell membrane interactions is therefore of
great interest in anti-viral research and an important step towards the
development of new anti-viral drugs and vaccines.
A. Cell membrane mimics to probe virus-membrane interactions
As a complement to traditional cell
studies used in the field of virology, our group develops surface-based assays
in combination with advanced microscopy techniques. These assays involve
different types of cell membrane mimics: from simplified artificial
supported-lipid bilayers that contain one cell receptor of choice(1, 2) (Figure 1A), to more complex native-like
membranes in which we incorporate membrane material extracted from relevant
cell lines(3) (Figure 1B). We probe binding kinetics
and mobility of individual virions interacting with the surfaces and study how
the composition of the membranes or the properties of the virions influence
this interaction. Our current work focuses on the Herpes Simplex Virus, a very
widespread human virus that affects about 90% of the population worldwide and
which presents structural or functional similarities to a large number of other
viruses, like HIV, Ebola, and Zika for example. Using our surface-based
approaches we study the molecular and physical mechanisms modulating HSV
binding and release from the cell surface (Figure 2). More specifically, we
gain insight into the modulatory function of protein glycosylation(1, 2) and interrogate the role of GAG
sulfation in the process(4).
Figure 1: Cell membrane mimics to study
virus-cell membrane interactions. A) Glycosaminoglycans serve as attachment
factors for a large number of viruses. To mimic the presentations of these
molecules in the extracellular matrix and close to the cell surface, we end-grafted
the polysaccharide chains to the surface, using a supported lipid bilayer and a
monolayer of streptavidin(1,
2). B) To increase the complexity
of our model membrane and to study virus-cell membrane interactions in a more
native-like environment, we incorporated membrane material extracted from
relevant cell lines to the supported-lipid bilayers(3).
Figure 2:
Image of fluorescently labeled
HSV-1 particles binding to end-grafted glycosaminoglycan chains, obtained with
total-internal reflection fluorescence microscopy. Scale bar: 50 µm.
Major collaborations
Tomas Bergström, Department of Infectious Diseases, Institute
of Biomedicine, University of Gothenburg, Göteborg, Sweden
Stephan Block, Department of Chemistry and Biochemistry, Freie Universität
Berlin, Berlin, Germany
B. Cell-based assays to study virus uptake
In complement to the use of
cell-membrane mimics, our group is developing and implementing experimental
methods based on live cell microscopy to probe virus attachment to, diffusion
on and uptake through the cell membrane on a single particle level.
C.
Virus characterization on a single
particle level
Virus particles are characterized by a
high degree of heterogeneity in their composition and in their physical
properties. To better understand what makes a virus infectious and to establish
a relation between particle properties and the characteristics of their
interaction with the cell surface, we are currently developing methods allowing
for the characterization of virus particles on a single particle level. Along
these lines we have recently presented a nanofluidic device, working as a nano
flow cytometer to characterize one by one small biological particles (Figure 3).
This device is compatible with standard epifluorescence microscopy, operates in
multiple fluorescence channels and allows for the fluorescence-based detection
of individual viruses and their quantification(5).
Figure 3: A nanofluidic device working as a nano flow cytometer
allows for the characterization of biological particles on a single particle
level using fluorescence microscopy. The particles are flown through the
nanochannels and kept in focus for imaging(5).
Major collaborations
Fredrik Westerlund, Department of Biology and Biological
Engineering, Chalmers Univeresity of Technology, Göteborg, Sweden
Elin Esbjörner Department of Biology and Biological
Engineering, Chalmers Univeresity of Technology, Göteborg, Sweden
D.
Selected references
1. Altgärde, N., C. Eriksson, N. Peerboom, T. Phan-Xuan, S.
Moeller, M. Schnabelrauch, S. Svedhem, E. Trybala, T. Bergström, and M. Bally.
2015. Mucin-like Region of Herpes Simplex Virus Type 1 Attachment Protein
Glycoprotein C (gC) Modulates the Virus-Glycosaminoglycan Interaction. J. Biol.
Chem. 290: 21473–21485.
2. Peerboom,
N., S. Block, N. Altgärde, O. Wahlsten, S. Möller, M. Schnabelrauch, E.
Trybala, T. Bergström, and M. Bally. 2017. Binding Kinetics and Lateral
Mobility of HSV-1 on End-Grafted Sulfated Glycosaminoglycans. Biophys. J. 113:
1–12.
3. Peerboom,
N., E. Schmidt, E. Trybala, T. Bergström, H. Pace, and M. Bally. In
preparation. .
4. Trybala,
E., N. Peerboom, B. Adamiak, M. Krzyzowska, J.-Å. Liljeqvist, M. Bally, and T.
Bergström. In preparation. .
5. Friedrich,
R., S. Block, M. Alizadehheidari, S. Heider, J. Fritzsche, E.K. Esbjörner, F.
Westerlund, and M. Bally. 2017. A nano flow cytometer for single lipid vesicle
analysis. Lab Chip. 17: 830–841.
E.
Project members
Marta Bally (Project leader)
Nadia Peerboom
Eneas Schmidt
Quentin Lubart
Noomi Altgärde