Biology Reference
In-Depth Information
recover from the disease; however, fatalities do occur, with case-fatality
rates being highest for older adults.
Hepatitis E Virus
The hepatitis E virus (HEV) is the prototype species of the genus
Hepevirus
, the only member of the family
Hepeviridae
.
12
It has a sin-
gle-stranded, non-segmented, positive-sense RNA genome of about
7.2 kB that encodes three ORFs. Recent work suggests that the
HEV capsid is composed of a single protein type.
13
Multiple copies
of the structural protein interact to form an icosahedral shell with
protrusions.
HEV is known to infect humans and other animal species. It is
endemic to various countries. The virus is spread mainly through the
fecal-oral route; however, cases of hepatitis E infections arising from
blood-transfusions and eating raw/undercooked meat have also been
reported.
12,14-16
In humans, the virus causes hepatitis E, an acute dis-
ease characterized by anorexia, jaundice and an inflamed liver. It has
a low mortality rate of about 1%.
Rabies Virus
The Rabies virus belongs to the
Rhabdoviridae
family, and is the pro-
totypic member of the genus
lyssavirus.
17
It has a single-stranded,
non-segmented, negative-sense RNA genome of approximately 11.9
kB that contains five genes (N, P, G, M and L) and a pseudogene.
Like most other members of the
Rhabdoviridae
family, the rabies virus
posseses a characterestic “bullet” shape. Each virion has two compo-
nents: (a) a ribonucleoprotein (RNP) core, which consists of the single-
stranded RNA genome tightly coiled around multiple copies of the
major nucleoprotein N and the minor polymerase components, the L
and P proteins; and (b) a lipoprotein bilayer membrane. Copies of the
glycosylated G protein, embedded in the lipid bilayer, protrude out-
ward as spike-like projections. The matrix protein M binds to the
inner membrane and to the RNP, forming a bridge between the inner
ribonucleoprotein core and the surface membrane. The structural
