Graeme Price g.e.price at bham.ac.uk
Tue Mar 12 15:57:29 EST 1996

In article <o0c9869-1103961814490001 at ppp0d-02.rns.tamu.edu>,
o0c9869 at tam2000.tamu.edu wrote:

> Interesting questions for immunologists:
> What do you think is the fate of viral DNA inside a macrophage?.

This is highly dependent on the virus involved, and in the way the virus
got into the macrophage (or any phagocyte). I'm relatively certain that
HIV proviral sequences have been detected in monocytes (which may serve as
a reservoir for HIV), and Cytomegalovirus is capable of replicating in
monocytes. Other viruses, such as influenza suffer a block in replication
in monocytes and macrophages, giving only a very low yield or an abortive
infection. Remember that not all viruses use DNA as their genetic
material: examples of RNA viruses abound.

> Possible ways for viruses to get to infect a macrophage?
> Is the viral particle phagocitized by the macrophage, or gets inside by
> another way?.

The "normal" way a virus gets into a cell is via an interaction between a
protein on the viral surface and a receptor on the cell surface. This
results in viral-cell membrane fusion (often preceeded by endocytosis) and
dumps the viral genome in the cytoplasm of the cell. Phagocytosis of
opsonized viral particles can occur, although this should usually result
in the destruction of the viruses. The final way I can think of offhand is
via Fc receptors binding non-neutralizing antibody complexed with virus
particles. This is a well known phenomenon with dengue virus, where after
a mild infection with one strain (which induces Ab specific to that
strain, but capable of cross reacting to other strains without
neutralizing infectivity) a subsequent infection with a second strain can
lead to much more severe disease as the virus can enter macrophages when
the Fc region of the antibody bound to it binds the Fc receptor on the
cell surface. This is called antibody dependent enhancement of infection.
> I am looking for your answers, based of course in real facts, and may be
> some degree of speculation. Let's discuss it.
> O Chacon.
> MD. Msc Immunolgy. PhD Candidate-Immunology.



Graeme Price
Microbial Molecular Genetics and Cell Biology Group, 
School of Biological Sciences, Biology West Building,
University of Birmingham,
Edgbaston, Birmingham,
West Midlands, B15 2TT.
United Kingdom.

Tel. (+44) (0)121 414 6555
Fax. (+44) (0)121 414 6557
E-mail g.e.price at bham.ac.uk

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