Pathogenic Viruses continued

1. Pathogenic Viruses continued • Herpes Virus family • VZV, CMV, and EBV • Hepatitis viruses • Hep A, B, and C: all unrelated, and transmitted differently, but cause similar disease. • Picornaviruses • Mosquito-borne viruses of Arkansas • Influenza • HIV (guest speaker Debbie Biazo of NARAN)

2. Herpes virus family • Human herpes viruses now numbered • But common names easier to use. • As a family: • ability to become latent; • predilection for either nervous tissue or lymphocytes; • ability to cause cancer. • Herpes roster: • Herpes simplex, Varicella zoster, cytomegalovirus, Epstein Barr, roseola, Kaposi’s sarcoma virus.

3. Herpes Simplex viruses • HHV1 (above the waist) • Typically oral, cold sores; flu-like symptoms, etc. • HHV2 (genital), STD and neonatal • Painful, contagious sores on genitals, overlap w/ HHV1. • Latency • Viruses enter nearby nerve cells, remain until activated by stress of some sort, cause disease, then return. • Spread and treatment: • Person to person by direct contact; spread within host by forming syncytia, escape immune system. • Acyclovir helps; no cure, lifetime infection.

4. Herpes family: Varicella Zoster • Varicella: chicken pox; Zoster: shingles • Chickenpox (not a pox virus), respiratory, disease becomes systemic with fever, malaise, skin lesions. • Very contagious; usually mild, esp. in children • Virus can become latent in nerves like Herpes simplex • Recurrence: shingles; rash, pain, on one side • Acyclovir can lessen symptoms • Beware of salicylates + viruses: Reyes syndrome • Vaccination: Varivax: attenuated vaccine

5. Herpes family: Cytomegalovirus • CMV (HHV5): Infection results in enlarged cells • Widespread asymptomatic infections, latency • Virus shed in body fluids: sex, birth, transplants • Problem for unborn, immunosuppressed, transplant patients; major cause of viral-induced birth defects. • Epstein Bar Virus • Cause of infectious mononucleosis • Infects B lymphocytes and salivary glands • With malaria, increased risk of cancer • Burkitt’s Lymphoma

6. Hepatitis • Hepatitis is inflammation of the liver • Liver especially important in metabolism • Breakdown of drugs, toxins, waste products • Damage results in accumulation of bilirubin • Bilirubin is stage in hemoglobin breakdown • Results in yellow color: jaundice • Hepatitis can be caused by several different viruses • Hepatitis A, B, and C viruses all cause liver damage, but are unrelated viruses.

7. Hepatitis B • A DNA virus: “Hepadnavirus” • Hepatitis B released from live cells, so accumulates in high numbers in body fluids. • Blood of infected person is rather infectious • Cuts, piercing, sex, childbirth, etc. • Large amounts of empty capsids ties up antibodies. • After exposure, long incubation, long disease • 10% have chronic infections • The younger the host, the likelier chronic infection

8. Hep B continued • Chronic infection correlated with liver destruction • Liver tissue replaced by scar tissue; liver failure • Long term exposure to virus increases risk of liver cancer • Insertion of HBV DNA into chromosome may activate oncogenes • Vaccination now recommended • Because of bad result of early infection and great danger of liver damage, liver cancer. • Recombinant vaccine.

9. Hepatitis A virus • A small RNA virus, “Picornavirus” • Transmitted by fecal-oral route • Incubation for 1 month, followed by fever, nausea, anorexia, jaundice • T cells attack infected liver cells • No chronic infections, patients recover. • Note comparisons to Hepatitis B: • RNA vs DNA • Shorter disease, few long term problems • Mode of spread completely different

10. Hepatitis C • Another RNA virus, different group: “Flavivirus” • Causes chronic infections • Can be mild, or destructive • Long term infections increase risk of cancer. • Transmission like Hep B: blood, sex, transplants • New hepatitis viruses being regularly discovered

11. Picornaviruses • Small RNA viruses • Two kinds: • enteric viruses, includes Hepatitis A and polio • Rhinoviruses: major cause of common cold • Rhinoviruses have many serotypes • Variants, caused by easy mutation of RNA • Immune system can’t recognize all differences, but enough similarities that colds become less severe, less frequent with age.

12. Arkansas Arboviruses • Not an official taxonomic group, but short for “arthropod-borne” • Includes Flaviviruses, Togaviruses, and others. • Zoonotic, spread from animals to people by arthropod vectors, especially mosquitoes. • Reservoirs may be birds, various mammals • Result in two main types of illnesses • Encephalitis, inflammation of the brain • Hemorrhagic fever: high fever with bleeding

13. Arkansas Arboviruses • Encephalitis: spread by skeeters • In Arkansas: Eastern Equine; • Togavirus; • Also infects, kills horses. Most dangerous. • St. Louis encephalitis, • Flaviviral diseases; Human disease. • Usually not serious. • West Nile virus • Flavivirus; imported to US, spread from NYC • Disease mostly in young and elderly

14. Orthomyxovirus • Influenza: a serious respiratory disease • Virus has a segmented genome • 8 different RNA molecules • Spikes: Hemagglutinin (for infecting cells) and neuraminidase (for escaping them) • Antigenic drift and shift • Drift: small mutations, making host susceptible • Shift: major mixing of RNAs, whole new virus. • Attack on respiratory tract • Kills ciliated epithelial cells, allows bacterial infections. Release of interferon causes symptoms.

15. View of flu http://www.astrosurf.org/lombry/Bio/virus-influenza.jpg http://www-micro.msb.le.ac.uk/3035/3035pics/flusection.jpg

16. influenza • Changes in H and N (antigenic shift) • Mixing of viruses that infect birds, pigs, produce new strains able to jump to humans. • New antigenic type leaves population unprotected • Numerous epidemics throughout history • Flu of 1918-1919 killed 20 million • Asia watched very carefully • Flu vaccines made from deactivated viruses • Slow process, so every year correct strains are “guessed”.

17. HIV/AIDS • Infection • 4 main types of cells infected, esp. T helper cells • Have CD4 glycoprotein on surface • After RNA is copied into cDNA, cDNA inserts • Infection is for life • Chronic infection • T cells continually made, continually destroyed • Eventually, host loses • AIDS diagnosis: • CD4 count below 200/µl; opportunistic infections

18. Treatment and prevention • Prevention is easy • Practice monogamous sex, avoid shared needles • HIV cannot be spread by casual contact, skeeters • Fastest growing victim demographic is YOU. • Not just a “gay disease” • Treatment is expensive, but usually works • Nuceloside analogs, protease inhibitors • Processing viral proteins requires protease • About $1500 a month for drugs