To the readers, if you have unsafe sex with multiple partners and shares intravenous drugs, you are at HIGH RISK for Hepatitis B. The disease spread through contact with infected blood or other body fluids of people who have hepatitis B. People who use intravenous drugs can get hepatitis B when they share needles with someone who has the virus. Pregnant women who are infected with hepatitis B can also pass the virus on to their babies. Hence, think twice before you act.
If you indulge in such activities you should see if you have these symptoms which arises through Acute Hepatitis B
Symptoms:
• nausea
• vomiting
• loss of appetite
• abdominal pain
• jaundice (the skin turns yellow)
• weakness
• fatigue
• brown urine (may look like tea)
Symptoms of hepatitis B can range from mild to severe. If you have a mild case of hepatitis, you may not even realize that you have it. It may not cause symptoms or may only cause symptoms similar to the stomach flu.
After reading what I have said about chronic and acute Hepatitis B, do you really understand what the differences between acute and chronic hepatitis B are?
When you are having symptoms for the first time, this is called acute hepatitis. Acute hepatitis lasts 6 weeks or less. Most people recover from the infection and have no long-lasting problems.
Hepatitis B can become an illness that lasts a long time. This is called chronic hepatitis B. It lasts six months or longer. Chronic hepatitis occurs when the liver has been damaged from the acute illness and can't recover. Chronic hepatitis develops in 10% to 20% of people who have hepatitis B.
People with chronic hepatitis B may not have any symptoms at all. In some people, chronic hepatitis can lead to cirrhosis of the liver. Cirrhosis occurs when the liver cells die and are replaced by scar tissue and fat. The damaged areas of the liver stop working and can't cleanse the body of wastes. Cirrhosis can lead to liver failure and even liver cancer.
If you have hepatitis B, you are also susceptible to hepatitis D (also called "Delta agent). Hepatitis D can only develop in people who already have hepatitis B. It can make your symptoms of hepatitis B or liver disease worse. It is spread through contact with infected blood or other body fluids of people who have hepatitis D.
The time between the acute illness and signs of chronic hepatitis B varies. It may take a short time, or it may be years after the acute infection before chronic hepatitis B develops.
By Amas goh
Friday, November 28, 2008
Thursday, November 27, 2008
How to diagnose, treat and prevent contracting Hepatitis B.
Hey it is me again! Today I will be talking on how to diagnose, treat and prevent yourself from contracting Hepatitis B.
The tests for detection of hepatitis B virus infection involve blood tests that detect either viral antigens or antibodies produced by the host. The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection. It is the first detectable viral antigen to appear during infection. The infectious virion contains an inner "core particle" enclosing viral genome known as hepatitis B core antigen, or HBcAg. During this stage the host remains infected but is successfully clearing the virus, IgM antibodies to the hepatitis B core antigen (anti-HBc IgM) may be the only serological evidence of disease.
After HbsAg appear, another antigen Hepatitis B e antigen (HBeAg) will appear. During the infection, the HBeAg may be cleared, and antibodies to the 'e' antigen (anti-HBe) will arise immediately afterwards. After the infection HBsAg will become undetectable and will be followed by IgG antibodies to the hepatitis B surface antigen and core antigen, (anti-HBs and anti HBc IgG). A person negative for HBsAg but positive for anti-HBs has either cleared an infection or has been vaccinated previously.
Individuals who remain HBsAg positive for at least six months are considered to be hepatitis B carriers. Carriers of the virus may have chronic hepatitis B, which would be reflected by elevated serum alanine aminotransferase levels and inflammation of the liver, as revealed by biopsy (cutting a small piece of liver for testing)
This picture shows what happens during and after the infection period
In adults, Acute hepatitis B infection does not usually require treatment because most adults clear the infection spontaneously, if not antiviral drugs can be given. For chronic infection, Interferon alfa-2b and other antiviral medicines will be given. Treatment may take a year or more, depending on the severity of the infection and the response to treatment.
After knowing all theses, we need to protect ourselves and our love one. So how do we do it?
The best way to prevent hepatitis B is to have protected sex (use a condom) and to avoid sharing needles. A vaccine is available to prevent hepatitis B. It is now routinely given in the first year of life to all newborn infants. It is safe and requires 3 shots over a 6-month period. This vaccine should be given to people who are at high risk for this illness, such as health care workers, all children, drug users, people who get tattoos or body piercing, and those with multiple sex partners.
Finally, remember the golden rules, play with fire and you will be burned. So think twice before you have unsafe sex!!
By Amas Goh
The tests for detection of hepatitis B virus infection involve blood tests that detect either viral antigens or antibodies produced by the host. The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection. It is the first detectable viral antigen to appear during infection. The infectious virion contains an inner "core particle" enclosing viral genome known as hepatitis B core antigen, or HBcAg. During this stage the host remains infected but is successfully clearing the virus, IgM antibodies to the hepatitis B core antigen (anti-HBc IgM) may be the only serological evidence of disease.
After HbsAg appear, another antigen Hepatitis B e antigen (HBeAg) will appear. During the infection, the HBeAg may be cleared, and antibodies to the 'e' antigen (anti-HBe) will arise immediately afterwards. After the infection HBsAg will become undetectable and will be followed by IgG antibodies to the hepatitis B surface antigen and core antigen, (anti-HBs and anti HBc IgG). A person negative for HBsAg but positive for anti-HBs has either cleared an infection or has been vaccinated previously.
Individuals who remain HBsAg positive for at least six months are considered to be hepatitis B carriers. Carriers of the virus may have chronic hepatitis B, which would be reflected by elevated serum alanine aminotransferase levels and inflammation of the liver, as revealed by biopsy (cutting a small piece of liver for testing)
This picture shows what happens during and after the infection period
In adults, Acute hepatitis B infection does not usually require treatment because most adults clear the infection spontaneously, if not antiviral drugs can be given. For chronic infection, Interferon alfa-2b and other antiviral medicines will be given. Treatment may take a year or more, depending on the severity of the infection and the response to treatment.
After knowing all theses, we need to protect ourselves and our love one. So how do we do it?
The best way to prevent hepatitis B is to have protected sex (use a condom) and to avoid sharing needles. A vaccine is available to prevent hepatitis B. It is now routinely given in the first year of life to all newborn infants. It is safe and requires 3 shots over a 6-month period. This vaccine should be given to people who are at high risk for this illness, such as health care workers, all children, drug users, people who get tattoos or body piercing, and those with multiple sex partners.
Finally, remember the golden rules, play with fire and you will be burned. So think twice before you have unsafe sex!!
By Amas Goh
Wednesday, November 26, 2008
How to do we get hepatitis A?
Fatigue, Fever, Nausea, Diarrhea, Appetite loss, Depression, Jaundice
Sharp pains in the right-upper quadrant of the abdomen, Weight loss, Itching
Although the virus is excreted in the feces towards the end of the incubation period, specific diagnosis is made by the detection of Hepatitis A virus specific IgM antibodies in the blood. IgM antibody is only present in the blood following an acute hepatitis A infection. It is detectable from one to two weeks after the initial infection and persists for up to 14 weeks. The presence of IgG antibody in the blood means that the acute stage of the illness is past and the person is immune to further infection. IgG antibody to HAV is also found in the blood following vaccination and tests for immunity to the virus are based on the detection of this antibody.
[Click to enlarge image]
During the acute stage of the infection, the liver enzyme alanine transferase (ALT) is present in the blood at levels much higher than is normal. The enzyme comes from the liver cells that have been damaged by the virus.
Hepatitis A virus is present in the blood, (viremia), and feces of infected people up to two weeks before clinical illness develops.
There is no specific treatment for hepatitis A. Sufferers are advised to rest, avoid fatty foods and alcohol (these may be poorly tolerated for some additional months during the recovery phase and cause minor relapses), eat a well-balanced diet, and stay hydrated. Approximately 15% of people diagnosed with hepatitis A may experience one or more symptomatic relapse(s) for up to 24 months after contracting this disease.
The United States Centers for Disease Control and Prevention (CDC) in 1991 reported a low mortality rate for hepatitis A of 4 deaths per 1000 cases for the general population but a higher rate of 17.5 per 1000, in those aged 50 and over. Death usually occurs when the patient contracts Hepatitis A while already suffering from another form of Hepatitis, such as Hepatitis B or Hepatitis C or AIDS.
Young children who are infected with hepatitis A typically have a milder form of the disease, usually lasting from 1-3 weeks, whereas adults tend to experience a much more severe form of the disease.
By Amas goh
Sharp pains in the right-upper quadrant of the abdomen, Weight loss, Itching
Although the virus is excreted in the feces towards the end of the incubation period, specific diagnosis is made by the detection of Hepatitis A virus specific IgM antibodies in the blood. IgM antibody is only present in the blood following an acute hepatitis A infection. It is detectable from one to two weeks after the initial infection and persists for up to 14 weeks. The presence of IgG antibody in the blood means that the acute stage of the illness is past and the person is immune to further infection. IgG antibody to HAV is also found in the blood following vaccination and tests for immunity to the virus are based on the detection of this antibody.
[Click to enlarge image]During the acute stage of the infection, the liver enzyme alanine transferase (ALT) is present in the blood at levels much higher than is normal. The enzyme comes from the liver cells that have been damaged by the virus.
Hepatitis A virus is present in the blood, (viremia), and feces of infected people up to two weeks before clinical illness develops.
There is no specific treatment for hepatitis A. Sufferers are advised to rest, avoid fatty foods and alcohol (these may be poorly tolerated for some additional months during the recovery phase and cause minor relapses), eat a well-balanced diet, and stay hydrated. Approximately 15% of people diagnosed with hepatitis A may experience one or more symptomatic relapse(s) for up to 24 months after contracting this disease.
The United States Centers for Disease Control and Prevention (CDC) in 1991 reported a low mortality rate for hepatitis A of 4 deaths per 1000 cases for the general population but a higher rate of 17.5 per 1000, in those aged 50 and over. Death usually occurs when the patient contracts Hepatitis A while already suffering from another form of Hepatitis, such as Hepatitis B or Hepatitis C or AIDS.
Young children who are infected with hepatitis A typically have a milder form of the disease, usually lasting from 1-3 weeks, whereas adults tend to experience a much more severe form of the disease.
By Amas goh
Monday, November 24, 2008
Hepatitis A..What is that?
Did you know that the most widespread hepatitis A outbreak in the United States afflicted at least 640 people (killing four) in north-eastern Ohio and south-western Pennsylvania in late 2003. The outbreak was blamed on tainted green onions at a restaurant in Monaca, Pennsylvania.In 1988, 300,000 people in Shanghai, China were infected with HAV after eating clams from a contaminated river… So, what is Hepatitis A?
The Hepatitis virus (HAV) is a Picornavirus; it is non-enveloped and contains a single-stranded RNA packaged in a protein shell.
Hepatitis A is an acute infectious disease of the liver caused by Hepatitis A virus, which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. The time between infection and the appearance of the symptoms, is between two and six weeks and the average incubation period is 28 days.
Hepatitis A does not have a chronic stage and does not cause permanent liver damage. Following infection, the immune system makes antibodies against the hepatitis A virus that confer immunity against future infection. The disease can be prevented by good hygiene, sanitation and vaccination. The vaccine protects against the virus in more than 95% of cases for 10 years. It contain inactivated Hepatitis A virus providing active immunity against a future infection. The vaccine was first phased in 1996 for children in high-risk areas, and in 1999 it was spread to areas with elevating levels of infection.
The vaccine is given in two doses in the muscle of the upper arm. The first dose provides protection two to four weeks after initial vaccination; the second booster dose, given six to twelve months later, provides protection for up to twenty years.
When HAV is ingested, it enters the bloodstream through the epithelium of the oropharynx or intestine. The blood carries the virus to its target, the liver, where it lives and multiplies within hepatocytes and Kupffer cells. There is no apparent virus-mediated cytotoxicity, and liver pathology is likely immune-mediated. Virions are secreted into the bile and released in stool. HAV is excreted in large quantities approimately 11 days prior to appearance of symptoms or anti-HAV IgM antibodies in the blood. The incubation period is 15-50 days, and mortality is less than 0.5%.
The virus spreads by the fecal-oral route and infections often occur in conditions of poor sanitation and overcrowding. Hepatitis A can be transmitted by the parenteral route but very rarely by blood and blood products. Food-borne outbreaks are not uncommon, and ingestion of shellfish cultivated in polluted water is associated with a high risk of infection. Approximately 40% of all acute viral hepatitis is caused by HAV. Infected individuals are infectious prior to onset of symptoms, roughly 10 days following infection.
Early symptoms of hepatitis A infection can be mistaken for influenza, but some sufferers, especially children, exhibit no symptoms at all. Symptoms typically appear 2 to 6 weeks, after the initial infection.
By Amas Goh
The Hepatitis virus (HAV) is a Picornavirus; it is non-enveloped and contains a single-stranded RNA packaged in a protein shell.
Hepatitis A is an acute infectious disease of the liver caused by Hepatitis A virus, which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. The time between infection and the appearance of the symptoms, is between two and six weeks and the average incubation period is 28 days.
Hepatitis A does not have a chronic stage and does not cause permanent liver damage. Following infection, the immune system makes antibodies against the hepatitis A virus that confer immunity against future infection. The disease can be prevented by good hygiene, sanitation and vaccination. The vaccine protects against the virus in more than 95% of cases for 10 years. It contain inactivated Hepatitis A virus providing active immunity against a future infection. The vaccine was first phased in 1996 for children in high-risk areas, and in 1999 it was spread to areas with elevating levels of infection.
The vaccine is given in two doses in the muscle of the upper arm. The first dose provides protection two to four weeks after initial vaccination; the second booster dose, given six to twelve months later, provides protection for up to twenty years.
When HAV is ingested, it enters the bloodstream through the epithelium of the oropharynx or intestine. The blood carries the virus to its target, the liver, where it lives and multiplies within hepatocytes and Kupffer cells. There is no apparent virus-mediated cytotoxicity, and liver pathology is likely immune-mediated. Virions are secreted into the bile and released in stool. HAV is excreted in large quantities approimately 11 days prior to appearance of symptoms or anti-HAV IgM antibodies in the blood. The incubation period is 15-50 days, and mortality is less than 0.5%.
The virus spreads by the fecal-oral route and infections often occur in conditions of poor sanitation and overcrowding. Hepatitis A can be transmitted by the parenteral route but very rarely by blood and blood products. Food-borne outbreaks are not uncommon, and ingestion of shellfish cultivated in polluted water is associated with a high risk of infection. Approximately 40% of all acute viral hepatitis is caused by HAV. Infected individuals are infectious prior to onset of symptoms, roughly 10 days following infection.
Early symptoms of hepatitis A infection can be mistaken for influenza, but some sufferers, especially children, exhibit no symptoms at all. Symptoms typically appear 2 to 6 weeks, after the initial infection.
By Amas Goh
Friday, November 21, 2008
Hepatitis B- What is it about?
Did you know that Hepatitis B virus infects the liver of in humans, and causes an inflammation called hepatitis. It is a DNA virus cause viral hepatitis and has caused epidemics in parts of Asia and Africa. Chronic hepatitis B is a long-term infection of the liver that can sometimes develop after a bout of acute, or short term, hepatitis B.
Look at this cute virus, it is a member of the Hepadnavirus family. The virion consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity. The outer envelope contains embedded proteins which are involved in viral binding of, and entry into, susceptible cells.
Did you know that Hepatitis B virus is one of the smallest enveloped animal viruses with a virion diameter of 42nm? The surface antigen (HBsAg) is composed of the lipid and protein that forms part of the surface of the virion and is produced in excess during the life cycle of the virus. The genome of HBV is made of circular DNA, but it is unusual because the DNA is not fully double-stranded. One end of the full length strand is linked to the viral DNA polymerase.
I found this video that will give a more detailed explanation on the Hepatitis B virus.
By amas goh
Look at this cute virus, it is a member of the Hepadnavirus family. The virion consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity. The outer envelope contains embedded proteins which are involved in viral binding of, and entry into, susceptible cells.
Did you know that Hepatitis B virus is one of the smallest enveloped animal viruses with a virion diameter of 42nm? The surface antigen (HBsAg) is composed of the lipid and protein that forms part of the surface of the virion and is produced in excess during the life cycle of the virus. The genome of HBV is made of circular DNA, but it is unusual because the DNA is not fully double-stranded. One end of the full length strand is linked to the viral DNA polymerase.
I found this video that will give a more detailed explanation on the Hepatitis B virus.
By amas goh
Thursday, November 20, 2008
Herpesviridae
Any one knows that Herpesviridae are a large virus family that affect animal and human?
Herpesviruses all share a common structure—all herpesviruses are composed of relatively large double-stranded, linear DNA genomes encoding 100-200 genes encased within an icosahedral protein cage called the capsid which is itself wrapped in a lipid bilayer membrane called the envelope. Herpesvirus is unique because after primary infection virus normally remain latent , reactivation occur when (stress,expose to sunlight during menstrual period)
Virus hide in the nerves tissue. Causes viralencephalitis or if passed from mother
birth, may cause brain damage in the child.
Herpesvirus genome has a concentric virion which contain
-Inner core
-Icosahedral capsid
-Amorphous tegument
-Envelope (glycoprotein)
Pathogenesis
Herpes simplex viruses
-HSV1 (cold sores) –oral cavity
-HSV2 (genital herpes) -genital
Varicella Zoster virus
-Varicella (chicken pox) –respiratory tract, pharynx
- Herpes zoster (shingles)
-Cytomegalovirus –? Virus found in saliva, urine, semen,
cervial secretion, breast milk
-EBV –nasopharynx, salivary gland
Clinical Features
Cold sores -blisters around the mouth -1 week
-Also affect eyes, gum.
-Genital herpes -blisters, burning sensation, discharge -1 -3 weeks
-Fever
-Lesion all over body
-Scratched lesion lead to secondary infection!
-Scarring
-Dangerous in pregnant women!
-May affect nervous system
Herpesviruses all share a common structure—all herpesviruses are composed of relatively large double-stranded, linear DNA genomes encoding 100-200 genes encased within an icosahedral protein cage called the capsid which is itself wrapped in a lipid bilayer membrane called the envelope. Herpesvirus is unique because after primary infection virus normally remain latent , reactivation occur when (stress,expose to sunlight during menstrual period)
Virus hide in the nerves tissue. Causes viralencephalitis or if passed from mother
birth, may cause brain damage in the child.
Herpesvirus genome has a concentric virion which contain
-Inner core
-Icosahedral capsid
-Amorphous tegument
-Envelope (glycoprotein)
Pathogenesis
Herpes simplex viruses
-HSV1 (cold sores) –oral cavity
-HSV2 (genital herpes) -genital
Varicella Zoster virus
-Varicella (chicken pox) –respiratory tract, pharynx
- Herpes zoster (shingles)
-Cytomegalovirus –? Virus found in saliva, urine, semen,
cervial secretion, breast milk
-EBV –nasopharynx, salivary gland
Clinical Features
Cold sores -blisters around the mouth -1 week
-Also affect eyes, gum.
-Genital herpes -blisters, burning sensation, discharge -1 -3 weeks
-Fever
-Lesion all over body
-Scratched lesion lead to secondary infection!
-Scarring
-Dangerous in pregnant women!
-May affect nervous system
Tuesday, November 18, 2008
Hierarchical classification of virus
This classification of virus was created by Lwoff, R. W. Horne, and P. Tournier in 1962.
It consists of phylum - class - order - family - subfamily - genus - species - strain/type, based on the shared properties of virus
4 main properties are used:
1. Nature of the nucleic acid: RNA or DNA
2. Symmetry of the capsid
3. Presence or absence of an envelope
4. Dimensions of the virion and capsid
Virus families are ordered with genomics, the explanation of relationships through evolution by researching on nucleic acid and protein sequence. All families have suffix -viridae e.g. Caliciviridae, Picornaviridae, Reoviridae, while genera have suffix –virus e.g. in Picornaviridae family there are 5 genera: enterovirus, cardiovirus, rhinovirus, apthovirus and hepatovirus.
Acknowledgement: http://www.nlv.ch/Virologytutorials/Classification.htm
This classification of virus was created by Lwoff, R. W. Horne, and P. Tournier in 1962.
It consists of phylum - class - order - family - subfamily - genus - species - strain/type, based on the shared properties of virus
4 main properties are used:
1. Nature of the nucleic acid: RNA or DNA
2. Symmetry of the capsid
3. Presence or absence of an envelope
4. Dimensions of the virion and capsid
Virus families are ordered with genomics, the explanation of relationships through evolution by researching on nucleic acid and protein sequence. All families have suffix -viridae e.g. Caliciviridae, Picornaviridae, Reoviridae, while genera have suffix –virus e.g. in Picornaviridae family there are 5 genera: enterovirus, cardiovirus, rhinovirus, apthovirus and hepatovirus.
Acknowledgement: http://www.nlv.ch/Virologytutorials/Classification.htm
Saturday, November 15, 2008
Baltimore classification
• I: dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses)
• II: ssDNA viruses (+)sense DNA (e.g. Parvoviruses)
• III: dsRNA viruses (e.g. Reoviruses)
• IV: (+)ssRNA viruses (+)sense RNA (e.g. Picornaviruses, Togaviruses)
• V: (-)ssRNA viruses (-)sense RNA (e.g. Orthomyxoviruses, Rhabdoviruses)
• VI: ssRNA-RT viruses (+)sense RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
• VII: dsDNA-RT viruses (e.g. Hepadnaviruses)
• II: ssDNA viruses (+)sense DNA (e.g. Parvoviruses)
• III: dsRNA viruses (e.g. Reoviruses)
• IV: (+)ssRNA viruses (+)sense RNA (e.g. Picornaviruses, Togaviruses)
• V: (-)ssRNA viruses (-)sense RNA (e.g. Orthomyxoviruses, Rhabdoviruses)
• VI: ssRNA-RT viruses (+)sense RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
• VII: dsDNA-RT viruses (e.g. Hepadnaviruses)
Acknowledgement
http://en.wikipedia.org/wiki/Baltimore_classification
http://en.wikipedia.org/wiki/Baltimore_classification
Sunday, November 9, 2008
Different between virus and bacteria!
The Difference Between Viruses and Bacteria
Viruses are the smallest and simplest known life form. They are 10 to 100 times smaller than bacteria.
The biggest difference between viruses and bacteria is that viruses must have a living host - like a plant, or animal - to multiply, while most bacteria can grow on non-living surfaces.
Unlike bacteria, which attack the body like soldiers mounting a pitched battle, viruses are guerilla fighters. They don't attack so much as infiltrate. They literally invade human cells and turn the cell's genetic material from its normal function to producing the virus itself.
Bacteria carry all the machinery needed for their growth and multiplication, while viruses carry mainly information - for example, DNA or RNA, packaged in a protein and/or membranous coat. Viruses harness the host cell's machinery to reproduce. In a sense, viruses are not truly "living," but are essentially information (DNA or RNA) that float around until they encounter a suitable living host.
References: Food and Drug Administration May 2007
http://www.cfsan.fda.gov/
Viruses are the smallest and simplest known life form. They are 10 to 100 times smaller than bacteria.
The biggest difference between viruses and bacteria is that viruses must have a living host - like a plant, or animal - to multiply, while most bacteria can grow on non-living surfaces.
Unlike bacteria, which attack the body like soldiers mounting a pitched battle, viruses are guerilla fighters. They don't attack so much as infiltrate. They literally invade human cells and turn the cell's genetic material from its normal function to producing the virus itself.
Bacteria carry all the machinery needed for their growth and multiplication, while viruses carry mainly information - for example, DNA or RNA, packaged in a protein and/or membranous coat. Viruses harness the host cell's machinery to reproduce. In a sense, viruses are not truly "living," but are essentially information (DNA or RNA) that float around until they encounter a suitable living host.
References: Food and Drug Administration May 2007
http://www.cfsan.fda.gov/
Friday, November 7, 2008
Virus structure!
Virus
A virus is a sub cellular organism with a parasitic intracellular life cycle. It contains either RNA or DNA but not both. A virus is a non-living thing since it does not meet the requirements of a living thing. But once it has a host, it starts to infect the host. A virus is made up of a virion which contains nucleic acid genome surrounded by protein. The basic objective of a virion is to transfer the viral genome to a cell where it starts to replicate. This requires 2 things which are structures to contain and protect nucleic acid genome and specific receptors on the virion surface which allows virus to enter the target cell.
Virus Structure - Capsid
The capsid is the protein structure surrounding the viral genome which is assembled around the nucleic acid. The whole part is called nucleocapsid. The use of small protein subunits reduces amount of genetic code capacity that has to be dedicated to produce capsid proteins which are crucial as big viral genomes are very small by cellular standards. Protein components naturally align in the energetically favourable state thus certain structure is preferred. These structures have mostly icosahedral or helical symmetry.
Envelope
The envelope is derived from membranes of the host cell. Envelopment is roughly a passive process of picking up membrane from the cell. Before envelopment takes places, specific changes occur to the membrane. Changes to membrane fluidity is resulting from preferential incorporation of specific lipids. The most apparent change is presence of protein spikes or fringe when virion is viewed by electron microscope. The viral proteins have to be present in order to platform specific virus functions like binding to host cell.
A virus is a sub cellular organism with a parasitic intracellular life cycle. It contains either RNA or DNA but not both. A virus is a non-living thing since it does not meet the requirements of a living thing. But once it has a host, it starts to infect the host. A virus is made up of a virion which contains nucleic acid genome surrounded by protein. The basic objective of a virion is to transfer the viral genome to a cell where it starts to replicate. This requires 2 things which are structures to contain and protect nucleic acid genome and specific receptors on the virion surface which allows virus to enter the target cell.
Classification of virus
Virus Structure - Capsid
The capsid is the protein structure surrounding the viral genome which is assembled around the nucleic acid. The whole part is called nucleocapsid. The use of small protein subunits reduces amount of genetic code capacity that has to be dedicated to produce capsid proteins which are crucial as big viral genomes are very small by cellular standards. Protein components naturally align in the energetically favourable state thus certain structure is preferred. These structures have mostly icosahedral or helical symmetry.
Icosahedral Helical
Envelope
The envelope is derived from membranes of the host cell. Envelopment is roughly a passive process of picking up membrane from the cell. Before envelopment takes places, specific changes occur to the membrane. Changes to membrane fluidity is resulting from preferential incorporation of specific lipids. The most apparent change is presence of protein spikes or fringe when virion is viewed by electron microscope. The viral proteins have to be present in order to platform specific virus functions like binding to host cell.
Viral Genome Size
A large viral genome is still small by cellular standards means that virus can produce many proteins allowing a complex structure whereas viruses with small genome are restricted. Therefore bigger viral genome means that the complexity of the structure is more than those with small viral genome.
Viral genome types
• Double stranded(ds) DNA – These are often among largest of viral genomes
• Single stranded (ss) DNA – These are usually small genomes
• Ds RNA- Compared to all RNA genomes these are smaller than most DNA genome
• Ss RNA - Can be subdivided into (+) & (-) sense. Positive sense can function as mRNA and those that are complementary to mRNA are negative sense.
Viruses with RNA genomes use DNA intermediate stage to produce the RNA genome.
Viruses with DNA genomes use RNA intermediate stage to produce DNA genome
Virus cycle
Attachment
Entry
Uncoating
replication and expression
Assembly
Exit
Replication of Virus
A virion must protect the viral genetic material and it has to be capable of delivering it into host cell. The surface of any virus must have receptor/effectors to bind to the host cell. Binding is mediated on one side by specific viral proteins and the other side by cellular structures. The progeny virus genomes assemble into new viruses and are used to make more viruses.
A large viral genome is still small by cellular standards means that virus can produce many proteins allowing a complex structure whereas viruses with small genome are restricted. Therefore bigger viral genome means that the complexity of the structure is more than those with small viral genome.
Viral genome types
• Double stranded(ds) DNA – These are often among largest of viral genomes
• Single stranded (ss) DNA – These are usually small genomes
• Ds RNA- Compared to all RNA genomes these are smaller than most DNA genome
• Ss RNA - Can be subdivided into (+) & (-) sense. Positive sense can function as mRNA and those that are complementary to mRNA are negative sense.
Viruses with RNA genomes use DNA intermediate stage to produce the RNA genome.
Viruses with DNA genomes use RNA intermediate stage to produce DNA genome
Virus cycle
Attachment
Entry
Uncoating
replication and expression
Assembly
Exit
Replication of Virus
A virion must protect the viral genetic material and it has to be capable of delivering it into host cell. The surface of any virus must have receptor/effectors to bind to the host cell. Binding is mediated on one side by specific viral proteins and the other side by cellular structures. The progeny virus genomes assemble into new viruses and are used to make more viruses.
Tuesday, November 4, 2008
T4 Phage?
Pictures of T4 Bacteriophage
Looks like an alien landing pod.
Bacteriophage attaches to surface of bacteria Escherichia coli (E. coli).
Once attached, it injects DNA into bacterium, which uses bacterium to generate more DNA to produce more of such bacteriophage. After cycle is complete, bacterium bursts and dies, releasing newly produced bacteriophages to continue infecting other bacteria.
Bacteriophages have been used as an antibiotic in the former Soviet Union and Eastern Europe. They are seen as a possible therapy against multi drug resistant strains of many bacteria.
T4 bacteriophage undergoes a lytic lifecycle. It takes about 30 minutes (at 37 °C) and consists of:
Adsorption and penetration (immediate)
Arrest of host gene expression (immediate)
Enzyme synthesis (starts after 5 mins)
DNA replication (starts after 10 mins)
Formation of new virus particles (starts after 12 mins)
Courtesy of: http://www.cellsalive.com/phage.htm, http://en.wikipedia.org/wiki/T4_phage
Looks like an alien landing pod.
Bacteriophage attaches to surface of bacteria Escherichia coli (E. coli).
Once attached, it injects DNA into bacterium, which uses bacterium to generate more DNA to produce more of such bacteriophage. After cycle is complete, bacterium bursts and dies, releasing newly produced bacteriophages to continue infecting other bacteria.
Bacteriophages have been used as an antibiotic in the former Soviet Union and Eastern Europe. They are seen as a possible therapy against multi drug resistant strains of many bacteria.
T4 bacteriophage undergoes a lytic lifecycle. It takes about 30 minutes (at 37 °C) and consists of:
Adsorption and penetration (immediate)
Arrest of host gene expression (immediate)
Enzyme synthesis (starts after 5 mins)
DNA replication (starts after 10 mins)
Formation of new virus particles (starts after 12 mins)
Courtesy of: http://www.cellsalive.com/phage.htm, http://en.wikipedia.org/wiki/T4_phage
Monday, November 3, 2008
What is a virus?
Virus
What Is a Virus?
A virus is an extremely tiny infectious agent that is only able to live inside a *cell.
Viruses can be rod-shaped, sphere-shaped, or multisided. Some viruses look like tadpoles.
Basically, viruses are composed of just two parts. The outer part is a protective shell made of *protein. This shell is often surrounded by another protective layer or envelope, made of protein or lipids (fats). The inner part is made of genetic material, either *RNA or *DNA.
A virus does not have any other structures (called organelles) that living cells have, like a nucleus or mitochondria. These organelles are the tiny organs that maintain a cell's metabolism (life processes). A virus has no metabolism at all.
http://www.acnepain.com/virus.html
What Is a Virus?
A virus is an extremely tiny infectious agent that is only able to live inside a *cell.
Viruses can be rod-shaped, sphere-shaped, or multisided. Some viruses look like tadpoles.
Basically, viruses are composed of just two parts. The outer part is a protective shell made of *protein. This shell is often surrounded by another protective layer or envelope, made of protein or lipids (fats). The inner part is made of genetic material, either *RNA or *DNA.
A virus does not have any other structures (called organelles) that living cells have, like a nucleus or mitochondria. These organelles are the tiny organs that maintain a cell's metabolism (life processes). A virus has no metabolism at all.
http://www.acnepain.com/virus.html
Saturday, November 1, 2008
Welcome to the Viridae Portal
We are a group of students from NYP Molecular Biotecnology MB0803
This blog is designed for our Microbiology B blog assignment, it is also a one stop portal for the news information from the world of viruses.
This blog is maintained by Amas Goh Chun Kiat, Wilson Chew Hong Wen, Phua Yao xing , N. Mohan , Low Soon Huat. This is our first entry and hope that you will carry on supporting this blog thanks =) Cheer!
This blog is designed for our Microbiology B blog assignment, it is also a one stop portal for the news information from the world of viruses.
This blog is maintained by Amas Goh Chun Kiat, Wilson Chew Hong Wen, Phua Yao xing , N. Mohan , Low Soon Huat. This is our first entry and hope that you will carry on supporting this blog thanks =) Cheer!
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