Download VIROLOGY - MCB 5505 VIRUS FAMILY: RHABDOVIRIDAE I

VIROLOGY - MCB 5505
VIRUS FAMILY:
RHABDOVIRIDAE
I.
DISTINGUISHING CHARACTERISTICS
A.
LYSSA VIRUS (RABIES VIRUS) CAN CAUSE A RARE AND
DEADLY ENCEPHALITIS
B.
ELONGATED, DISTINCTIVE “BULLET SHAPED” APPEARANCE
C.
VIRIONS CONTAIN AN RNA POLYMERASE ACTIVITY (L)
THAT TRANSCRIBS AND REPLICATES GENOME RNA
D.
-STAND RNA IS NON-INFECTIOUS (NEITHER IS THE +STRAND)
E.
REPLICATION OCCURS IN THE CYTOPLASM OF HOST CELL
WHICH ACTS AS A VIRUS “FACTORY” CREATING CYTOPLASMIC INCLUSION BODIES
II.
STRUCTURE
A.
SIZE: 70-180 nm IN DIAMETER
B.
ENVELOPE: YES
1.
GLYCOPROTEINS: EXTERNAL (G) GLYCOPROTEIN
65kDa
PROTEIN SPIKE
2.
OTHER PROTEINS: NONE
3.
MATRIX PROTEINS: INTERNAL (M) MATRIX PROTEIN
26kDa
LINE ENVELOPE
C.
NUCLEOCAPSID
1. NUCLEIC ACID: HELICAL NUCLEOCAPSID
a.
TYPE: RNA
BALTIMORE TYPE: V
b.
STRANDED: SS
c.
POLARITY: (-)
d.
# GENES:
5
2. GENETIC (PHYSICAL) MAP:
VSV INTERGENIC SEQUENCE : AUACUUUUUUU GA UUGUC
|
|
End
Intergenic Start
Katie Eggers
3. CAPSID- NUCLEOCAPSID
a.
SYMMETRY: ELONGATED, ROD “BULLET” SHAPE
b.
COMPOSITION:
(1)
PROTEINS: NUCLEOCAPSID (N) PROTEIN
MAJOR 50kDa
LARGE PROTEIN (L) 116-190kDa
P PROTEIN 40kDa
VIRUS FAMILY:
RHABDOVIRIDAE
III.
CLASSIFICATION AND CHARACTERISTIC MEMBERS
GENERA
Lyssa virus
PROPERTIES
Infect vertebrates and
some insects
Vesiculovirus
VSV infection of
humans, mostly
infects insects
Ephemerovirus
infects vertebrates
IV.
MEMBERS
Rabies virus
Makola virus
Lagos Bat virus
Vesicular Stomatitis Virus –
VSV
Cocal virus
Alogoas virus
Bovine ephemeral fever virus
VIRAL MULTIPLICATION
A.
ABSORPTION: Attachment of viral glycoprotein (G) to a receptor on
host cell surface, probably a phospholipid
B.
PENETRATION AND UNCOATING: Penetrates by a temperature and
pH process, probably using endocytosis and fusion with the membrane of
the vesicles meditated by the G protein. Uncoating happens in the
cytoplasm where replication occurs.
C.
GENE EXPRESSION: The genome is transcribed into 5 mRNA’s,
capped and polyadenylated. Glycoprotein (G) and Matrix protein (M) are
both involved in the envelope. The viral core is found to be infectious,
which shows that transcript activity is associated with the Largest protein
(L), the Nucleocapsid protein (N) and the P protein. This makes the 3
internal proteins a functional replicase complex, although it is undefined
as to how the RNA polymerase activity occurs.
D.
GENOME REPLICATION: The 5 mRNA’s are made by the sequential
transcription of the ORF’s. Transcription starts at a single site, requiring
the leader sequence. There is an intergenic sequence responsible for
termination and reinitiation of transcription by the polymerase between
each gene, producing separate transcripts. Replication requires the
transcription of the (+) intermediate RNA strand, which serves as a
template for progeny RNA and the mRNA that makes the viral proteins.
The genome is replicated by the L and P polymerase complex, but
requires additional unknown host factors.
E.
ASSEMBLY AND BUDDING: Virions are assembles around the tightly
coiled core. The (-) strand is packaged. The M protein becomes attached
to the host cell’s lipid bilayer, attracting the nucleocapsid proteins
associated with the L and P protein molecules. The helical nucleocapsid
buds through the lipid bilayer acquiring the M and G proteins. Small
amounts of host cell plasma membrane proteins become a part of the
viral envelope.
Katie Eggers
VIRUS FAMILY:
RHABDOVIRIDAE
V.
CLINICAL CORRELATIONS
A.
The rabies virus was first shown infectious in 1808. Pasteur (in the
(1880'S) succeeded in isolating an attenuated virus which he used to
treat patients. Replication of the virus occurs locally in muscle
and connective tissue with no symptoms, but eventually infects the
peripheral nerves. It travels to the central nervous system where it
causes a severe and fatal encephalitis. Rabies is transmitted by an
animal bite that breaks the skin. The animal vectors can be foxes,
bats, dogs, cats, etc. Passive immunization is required for those
infected and must be done soon after transmission. There are no
effective drug treatments.
B.
VSV causes an epidemic, self-limited disease in cattle. It can infect
humans causing a mild febrile disease.
Katie Eggers
REFERENCES:
http:// www.tulane.edu/~dmsander/www/335/Rhabdoviruses.html
http://www.tulane.edu/~dmsander/BIG VIROLOGY/BVRNArhabdo.html
http://life.anu.edu.au/viruses/ICTdB/620200000.htm
Levy, J.A., et al. (1994). Virology , 3rd ed. Prentice Hall, New Jersey.
Katie Eggers