Hepatitis A Virus

Hepatitis A Virus (HAV) is simply an enteric RNA virus that causes Hepatitis A, a liver disease. Identification of the virus occurred in 1973. This event could be achieved by the help of electron microscope because of HAV’s small sizes, it has 27-32 nm range of diameter. It is composed of 70% viral protein and 30% RNA. Its RNA is positive sense single stranded. Because of that it can translate its genetic material directly into protein. HAV differs from other members of the family, that it belongs to, in terms of:


 * Replication rate and adaptation duration in cell culture
 * Rare production of cytopathic effect
 * Unique composition
 * Ability to navigate itself to specific tissue
 * Genetic differences

Uniqueness of this organism leads to formation of a new genus, called Hepatovirus, under the family Picornavaridae. An individual infected by this virus is very lucky after overcome the infection. Because HAV includes only one serotype, one infection is enough to get lifelong immunity. However, it is reported that genetic variation occurs in Hepatitis A virus. Seven HAV genotype exist. They are I, II, III, IV, V, VI and VII. Four of them are able to infect human. Among four of them, I is the most common one.

Severity of HAV infection differs in terms of the type. Infection may include no symptom or may lead to formation of hepatic failure which can result in death. The virus is mainly threatening young children and chronic liver diseased old adults.

Most infections caused by the virus have fecal-oral route. General transmission way are the direct contact with infected individual and consumption of contaminated water or food. The most encouraged sources of foodborne HAV are vegetables, fruits and shellfish, which is able to be counted as major source among the others. The organism infects liver of, not only, humans and other primates, too. It is possible to acquire HAV from non-human infected primates in slavery, via close contact. The organism is very resistance. It can be understood from:


 * Its durability to purification process.
 * It is able to live more than 1 mount in seawater.
 * HAV is stable against to acid as other enteric viruses are (It can maintain its infectivity below pH 3)
 * Resistance to heating and freezing
 * Resistance against ether, chloroform and alcohol (because of non-lipid envelop).

Although it has very strong sides, chlorination, is the most commonly used disinfection method, can partially inactivate HAV while ionizing radiation, usage of phenol and formaldehyde are providing total inactivation.

Wild type of the virus has low rate of reproduction. Rate of reproduction increases after long term adaptation. This adaptation induces emergence of persistent infection of HAV. After infection, the virus loses its strong effect.

Fetal Rhesus monkey kidney and Africa green monkey kidney cells mainly used for culturing HAV though another cell types are available. In cell culture systems, some HAVs, that cause cytopathic effect, are observed. It is observed that these strains of HAV reproduce faster. Because of that more viral load formed than non-cytopathic strains produced. Average time needed for incubation of HAV is 30 days, however, it ranges from 2 weeks to 6 weeks.

It is a mystery what exact story of viral activity inside the host is. But it is known that as HAV is reproducing in host cell, organelles work synchronized. As a result of this collaboration, non-lytic quit of viruses from host occurs. Progeny of the virus released to bile and transported to fecces.

It is supposed that viral activity is much related with membranes produced from Endoplasmic Reticulum. And a recent study demonstrated that mature virions are stored in lysosome. Therefore, lysosome plays key role on non-lytic secretion of progenies. HAV is distributed over all around the World. However, this distribution is not uniform because regions includes low level of sanitation disrupt uniformness.

Sweden was the first victim of outbreak of Hepatitis A in 1955. This outbreak occurred because of ingestion of raw oysters. Such a good new, just 629 victims was part of the outbreak. But in following years larger scaled outbreaks experienced like outbreak in Shanghai, China in 1987. In this outbreak 300 000 people suffered from Hepatitis A and its source was contaminated clams.

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