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Herpesviridae Family

Herpesviridae Family . Dr.Nehal Draz. A good teacher is one who “…does not bid you to enter the house of his wisdom, but rather leads you to the threshold of your mind.”. . (Gibran). Introduction. Leading cause of human viral disease, second only to influenza & cold viruses.

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Herpesviridae Family

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  1. Herpesviridae Family Dr.NehalDraz

  2. A good teacher is one who “…does not bid you to enter the house of his wisdom, but rather leads you to the threshold of your mind.”. (Gibran)

  3. Introduction • Leading cause of human viral disease, second only to influenza & cold viruses. • Capable of causing overt disease or remaining silent for many years only to be reactivated, e.g. shingles • Derived from the Greek word herpeinmeans tocreep……reflects the creeping or spreading nature of the skin lesions caused by herpes virus.

  4. Structure • Large, enveloped DNA viruses • Icosahedralcapsids • DNA replicates in the nucleus of host cells

  5. This family includes 8 human pathogens: • Herpes simplex viruses (HSV) types 1 &2 • Varicella Zoster virus (VZV) • Cytomegalo virus (CMV) • Epstein-Barr virus (EBV) • Human Herpes viruses (HHV) types 6,7&8

  6. General Characteristics • Most infections are asymptomatic • They remain latent in the host after recovery from primary infection • All herpes viruses cause recurrent infections by reactivation of viral replication • In tissue culture they produce: • Intracellular inclusion bodies • Cytopathic effect: balloning and rounding of infected cells followed by cell death • Some are oncogenic: HSV-2, EBV, and HHV-8 • They can cause severe disease in immunocompromised hosts and neonates

  7. Types of Herpesviruses Dr Ekta Chourasia, Microbiology

  8. Epstein-Barr Virus (EBV) • Infects more than 95% of human poulation • Primary infection: acute infectious mononucleosis, a self limiting disease • It is an oncogenic virus associated with human malignancies

  9. Mode of transmition • Requires intimate contact with the saliva of an infected person ( kissing disease) • Doesn’t normally occur through air or blood

  10. pathogenesis • Replication in nasopharyngeal epithelium • Spreads to salivary glands and oropharyngeal lymphoid tissue • Further replication results in viremia, with subsequent infection of reticuloendothelial system; liver, spleen & B- lymphocytes • Host immune response includes CTLs (cytotoxic T-lymphocytes); characteristic atypical lymphocytes found in peripheral blood

  11. CTLs destroy EBV-infected B-cells reducing their number • Followed by latency in B-lymphocytes & oropharyngeal epithelial cells • In some cases EBV DNA becomes integrated with the host chromosome giving the infected cell the ability to proliferate indefinitely resulting in malignancy

  12. Disease 1- infectious mononucleosus: • Fever,malaise, lymphadenopathy, pharyngitis & hepatosplenomegaly with or without jaundice • May be rash • The severity depends on age ( younger milder) 2- EBV-associated malignancies: - Burkitt’s lymphoma in Africans - Nasopharyngeal carcinoma in Asians

  13. Nasopharyngeal carcinoma in Asia Burkitt’s lymphoma in Africa

  14. Laboratory diagnosis Blood picture: absolute lymphocytosis with atypical lymphocytes ( Downey cells) Specific Diagnosis: • Specimen: saliva,peripheral blood & lymphoid tissue 1- Direct Virus Demonstration: a) Direct Immunofluorescence: Cell scrappings from lesions are stained with monoclonal antibodies conjugated with a fluorescence dye. Viral inclusion bodies appear in UV microscope as a bright green intranuclear particles b) PCR and nucleic acid hybridization: for detection of viral DNA, most sensitive

  15. Paul Bunnel test Downey cells monospot test

  16. 2- serology: • a) detection of non-specific heterophil Abs: • patients with acute infectious mononucleosis develop transient non-specific Abs that agglutinate sheep RBCs. These are detected by Paul Bunnel or monospot tests • b) detection of specific Abs: by ELISA, indirect IF: • IgM to viral capsid Ag ( VCA-IgM)= recent infection followed by IgG to viral capsid Ag ( VCA-IgG) that remains for life • different Abs against other EBV Ags appear later in different stages of the disease No antiviral drugs or vaccines are available

  17. Thank You Have a Nice Day

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