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Pathogenic Viruses

Pathogenic Viruses. Name of virus; what family it belongs to; what disease it causes. DNA or RNA? Ss or ds? Characteristics of disease, symptoms. Viral virulence factors Epidemiology: reservoirs, vectors Immunizations. Brief review. Non-cellular “life forms”

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Pathogenic Viruses

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  1. Pathogenic Viruses • Name of virus; what family it belongs to; what disease it causes. • DNA or RNA? Ss or ds? • Characteristics of disease, symptoms. • Viral virulence factors • Epidemiology: reservoirs, vectors • Immunizations

  2. Brief review • Non-cellular “life forms” • Consists of nucleic acid and capsid (protein) • Some types possess envelope, spikes, accessory proteins • Obligate intracellular parasites • Nucleic acid enters host cell, directs operations • Ultimately, new copies of viral N.A., proteins made • Virus depends mostly on host cell machinery • Following assembly, new virions escape to infect new hosts

  3. Attack and defense • Virus has ways of attacking • Specific binding to host cell receptor • Receptors involved in normal cell functions • Virus may regulate cell division for its own replication • Insertion of viral DNA into chromosome allows virus to hide from immune system

  4. Defense by host • Host has ways of defending • Cell mediated immunity (T cells): infected cells killed. • Antibodies intercept virions between cells, in fluids • Interferon produces anti-viral state, prevents replication

  5. Our selections for Summer 2005 • Herpes Virus family • HSV 1 & 2; VZV; and CMV • Hepatitis viruses • Hep A, B, and C: all unrelated, and transmitted differently, but cause similar disease. • Mosquito-borne viruses of Arkansas • Influenza • HIV (possible guest speaker)

  6. 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.

  7. 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.

  8. 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

  9. 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.

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