Biology Reference
In-Depth Information
deaths occurring in developing countries.
1
Diarrhea is the third lead-
ing cause of mortality worldwide. Every year, an estimated three mil-
lion pediatric deaths result from viral gastroenteritis and dehydration.
2
Along with rotavirus, calicivirus, and enteric adenovirus, human astro-
viruses (HAstV) are one of the most important causes of viral pediatric
acute gastroenteritis.
3-5
HAstV were first identified 30 years ago by
Appleton and Higgins
6
as the cause of a gastroenteritis outbreak in a
maternity ward. Shortly thereafter, Madeley and Cosgrove
7
proposed
the name “astrovirus” after observing the virus' star-like morphology
by electron microscopy (EM) in stool samples from a pediatric diarrhea
outbreak. Despite the years that have elapsed since HAstV were dis-
covered, many aspects of their molecular biology and pathogenesis
remain still to be elucidated.
Human astroviruses are non-enveloped icosahedral viruses that
belong to the family
Astroviridae
with a plus-sense, single-stranded
RNA genome. According to the International Committee on Taxon-
omy of Viruses, the
Astroviridae
family is divided into two genera:
Mamastrovirus
, which includes astroviruses that infect mammals and
primarily causes gastroenteritis, and
Avastrovirus
, which includes
astroviruses that infect avian species and may cause intestinal as well
as extra-intestinal illness. Presently, HAstV are divided into eight
serotypes (HAstV-1 to HAstV-8), with HAstV-1 being the most
prevalent worldwide. HAstV-1 to 7 were initially identified accord-
ing to the reactivity of the capsid proteins with reference type-specific
rabbit antibodies, while HAstV-8 was fully characterized some years
later.
8-10
Over the last few years, the number of astrovirus sequences
available via Genbank has rapidly increased and the complete genome
for five HAstV isolates — including serotypes 1, 2, 3, and 8 — has
been sequenced.
9,11-14
Complete capsid sequences are available for
HAstV-1 through 6 and HAstV-8, as well as for feline, porcine, ovine,
mink, and turkey astroviruses and for the avian nephritis virus. HAstV
can be isolated and propagated in human intestinal CaCo-2 contin-
uous cell line in the presence of trypsin, which is involved in the cap-
sid protein maturation.
15
An infectious full-length cDNA clone is
available for HAstV-1.
16
BHK-21 cells can support HAstV-1 RNA
