MICROBIO 2.8 - HEPATITIS VIRUSES

• Hepatitis is caused by several viruses (hepatitis viruses A through E) that are antigenically and genetically unrelated.
• Some hepatitis viruses are acquired by ingestion via the fecal-oral route (hepatitis A and E).
• Other hepatitis viruses are primarily bloodborne or sexually transmitted (hepatitis B, C, and Delta).
• Whatever the portal of entry, all hepatitis viruses demonstrate marked tropism for liver cells.
• Hepatitis A and E produce only a transient infection followed by resolution.
• Hepatitis B, C, and Delta viruses can produce lifelong persistent infections, with ongoing virus replication in the liver and persistent viremia.
• Viral hepatitis is a clinical syndrome characterized by fever and signs/symptoms of liver injury.
• Clinical signs are variable and initially indistinguishable among the different hepatitis viruses.
• Specific etiology is identified by testing for specific viral proteins, specific antibodies against those proteins, or viral nucleic acid associated with the causative agent.
• Acute hepatitis isn't treated, but chronic hepatitis B or C can be treated with specific antiviral drugs to prevent or forestall permanent liver damage.
• Blood products which are routinely screened for hepatitis viruses, so transfusion-related hepatitis is now rare.
• Effective vaccines can prevent hepatitis A and B infections.
• Hepatitis A, B, and C are more common in the US.
• Hepatitis A is responsible for most cases of infectious hepatitis.
• Hepatitis B uses reverse transcription, like lentivirus/HIV.
• Hepatitis A & Hep E transmission occurs via oral ingestion, replication in the liver, shedding into bile ducts/intestine, and passage in feces.
• Hepatitis B & Hep C transmission may not always be symptomatic, but causes extensive replication in the liver.
• Hepatitis B is a DNA virus; the rest are RNA.

Hepatitis Specifics

• Hepatitis A is an (+) RNA Picornavirus with a naked icosahedral capsid and is transmitted via the fecal-oral route.
• It is common, usually benign, but more severe in adults and is vaccine preventable.
• It is self-limiting, treated with supportive care, and antibody (IgG) provides life-long immunity.
• Hepatitis B is a DNA Hepadnavirus with an enveloped icosahedral capsid with HBsAg outnumbering virions in serum and transmitted in blood, tissue, and semen.
• HBV coinfection and super-infection exist.
• There is a vaccine, Hepatitis B immune globulin, and chronic treatments are available.
• HBV Co-Infection onset is slow, and HBV Super-Infection onset is rapid.
• Hepatitis B can be sexual, vertical or parenteral transmission.
• Hepatitis C is an (+) RNA Flaviviridae with an enveloped icosahedral capsid transmitted via blood, tissue, and semen.
• There is no treatment, but Glecaprevir/Pibrentasvir and Paritaprevir are available.
• Parenteral and sexual trasmission.
• Hepatitis D is a (-) RNA Deltavirus with an enveloped icosahedral capsid and is "defective" because it relies on HBV and increases the severity of HBV infection, transmitted via blood, tissue, and semen.
• HBV Vaccine and Interferon are forms of treatment
• Is transmitted via vertical, parenteral or sexual means.
• Hepatitis E is (+) RNA Hepevirus with an icosahedral capsid (quasi-enveloped) and is transmitted via the fecal-oral route, particularly through water.
• Sanitation, Supportive Care, and a HepE vaccine licensed in China are available
• Is of sexual, vertical or fecal-oral route.

Temporal Aspects of Illness

• Hepatitis A transmission is via the fecal-oral route, transmission of hepatitis B and C is commonly through sexual contact.
• Hepatitis A & Hep E- causes oral ingestion, replication in liver, shed into bile ducts/intestine, passed in feces.
• Hep B & Hep C- can be asymptomatic with extensive replication in liver, can be transient: acute infection, or persistent: continued replication in liver & release in blood stream.
• Hep B transmission can occur through sexual transmission whereas C does not.
• After introduction to the bloodstream, HBV travels to the liver and attaches to surface of hepatocytes in order to start its infection and multiplication.
• Hepatitis B utilizes DNA-laden viral cores to bud through intracellular membranes which pick up the envelope of HBs Ag, and progeny virions will eventually be released.
• Hepatitis B is one ancient viruses known to infect man, and the virus was first specifically identified in 1966.
• The first hepatitis B vaccine became available in 1976.

Treatments

• All- Safe sex, washing hands (esp. before eating & after bathroom), clean needles, getting tested & treated quickly
• Hep A- inactivated HAV vaccine, Supportive Care, post-exposure prophylaxis with anti-HAV antibodies
• Hep B- HBV vaccine, Hep B immunoglobulin post-exposure prophylaxis (esp. if mother is HepB+), interferon & ribavirin (prevent replication), reverse transcriptase inhibitors (yes, it can also be used to prevent HIV & is often prescribed for patients with parenteral HBV)
• Hep C- No vaccine, interferon (transcription & protein synthesis), ribavirin (nucleotide biosynthesis & mutation), ritonavir (protease inhibitor)
• Poor patient adherence interferon is chronic drug (& there are side effects like fever & joint & muscle aches, CNS depression; ribavirin long-term is teratogenic-mutations to fetus)
• Hep D- HBV vaccine, interferon (transcription & protein synthesis)
• Hep E- Sanitation, Supportive Care, HepE vaccine licensed in China

Explore Hepatitis lectures and the structural differences between naked and enveloped RNA viruses. Naked viruses consist of only a protein capsid enclosing genetic material, while enveloped viruses have a lipid membrane surrounding the capsid. Prevent spread by focusing on hygiene.