Download HERPESVIRIDAE

INTRODUCTION TO
VIRUSES AND THEIR
STRUCTURE:
PETER H. RUSSELL, BVSc,
PhD, FRCPath, MRCVS
Department of Pathology and
Infectious Diseases, The Royal
Veterinary College,
Royal College Street,
London NW1 OTU.
E-mail
Web site
Objectives
Students should be able to:
• Summarise virus properties and
control.
• Describe virus structure and
enzymes in outline
Introduction to virology
How are virulent virus
infections controlled?
To associate a new virus with a
disease it must be grown in
pure culture and shown to be
virulent.
Virus structure
The nucleic acid:
Virus particles do not contain
messenger RNA, this is in the host
cell
A virus will contain either an RNA or
DNA genome
The capsid protein
The capsid proteins protects the nucleic acid.
They are arranged into are 3 forms of
symmetry, icosahedral, helical and complex.
Icosahedral capsid
An icosahedron has 12 vertices
with 20 triangular sides, termed
facets, like a geophysical dome.
It is made of capsomeres, which
appear spherical by em..
Helical capsid
Complex capsid
Envelope
Enzymes and regulatory
proteins
These are virus proteins which are
essential to virus replication. Some
are present in the virus particle,
others are only in the host cell.
Examples of non-structural
enzymes found in the infected cell
but not the virus :
Summary
Viruses require living cells and are
therefore infectious but can be contained
by hygiene/vaccines.
Several hundred particles which look
identical are made in each infected cell
overnight.
Viruses comprise a nucleic acid
surrounded by protein. Some have an
additional envelope which makes them
more fragile.