Herpes Viruses 2024 Sept PDF

HERPESVIRUSES  Learning Outcomes At the end of the lecture the students should be able to 1. Describe the morphological characteristics of herpesviruses 2. Classify human herpes viruses and state characteristic features of herpes viral infections 3. Describe pathogenesis, clinic...

HERPESVIRUSES  Learning Outcomes At the end of the lecture the students should be able to 1. Describe the morphological characteristics of herpesviruses 2. Classify human herpes viruses and state characteristic features of herpes viral infections 3. Describe pathogenesis, clinical features and complications of human herpes virus infections 4. Outline the methods used for laboratory diagnosis and the principle of treatment 5. Outline the prevention and control of herpesvirus infections  Herpes viruses that commonly infect humans: 1 Herpes simplex virus type 1 (HSV-1) HHV1 2 Herpes simplex virus type 2 (HSV-2) HHV2 3 Varicella-zoster virus (VZV) HHV3 4 Epstein-Barr virus (EBV) HHV4 5 Cytomegalovirus (CMV) HHV5 6 Human herpesvirus 6 HHV6 7 Human herpesvirus 7 HHV7 8 Kaposi sarcoma-associated herpesvirus (KSHV) HHV8  Overview of herpesviruses Icosahedral core with envelope ds DNA virus Replicate in the nucleus and form IB Multinucleated giant cells (HSV-1, HSV-2, VZV, CMV) by Tzanck smear Life-long latent infections (latency in neurons HSV-1, HSV-2, VZV), B-lymphocytes (EBV, HHV-8), monocytes (CMV) Vesicular rash (HSV-1, HSV-2, VZV) Severe infections (Neonatal herpes with HSV-2, intrauterine infection (CMV) Association/causation cancers (EBV, KSHV) Antiviral drugs available : HSV-1, HSV-2, VZV Vaccines against VZV (Varivax, Shingrix)  Herpes simplex viruses (HSV 1& 2) Morphologically similar Antigenicity & locations of infections – different HSV 1 – infections above the waist ( contact transmission) HSV 2 – below waist (sexual, mother-to-fetus) Latency in sensory ganglion HSV 1 - trigeminal ganglion HSV 2 - lumber & sacral ganglion CMI is important to limit infection Reactivated by inducers (stress, trauma, fever, sunlight)  Herpes Simplex Viruses infections Primary infection - first contact with HSV Latent infection - persistence of virus in ganglia Reactivation - production of infective virus by latently infected cell Recurrence - clinically apparent disease produced by reactivation Primary infections are more severe than reactivation Symptoms of initial/primary and subsequent episodes/reactivation-similar Herpetic whitlow  HSV 1& 2 Primary infection with HSV-1: Gingivostomatitis, pharyngitis (most common) among children, young adults Reactivation by HSV-1: recurrent herpes labialis (most common) In AIDS patients- persistent ulcerative HSV infection HSV infection in eyes: corneal blindness (most common) Genital HSV infection: Cervix, urethra involve >80% Most sensitive Dx method for HSV infection: PCR Treatment & Prevention: Acyclovir, valacyclovir, famciclovir, penciclovir Reduce viral shedding, shorten the duration of illness, No effect on latency s Avoid contact with vesicular lesions or ulcers Cesarean section for term pregnancy who has genital lesions No vaccines  Varicella Zoster Virus (VZV) Primary disease: Chickenpox / Varicella Recurrent or reactivation: Zoster / shingles Latency in dorsal root ganglion Morphology of virus similar to other herpesviruses Antigenically different Only one serotype  Zoster / Shingle Reactivation of VZV painful vesicles distributed on the skin corresponds to the areas of innervation from an individual dorsal root ganglion Herpes zoster ophthalmicus (dermatome) post herpetic neuralgia Immunocompromised patient: life- threatening disseminated infections such as pneumonia  EB virus Lab Dx: Monospot test detect Heterophil ab (non-specific Ab : IgM ab that reacts with Paul Bunnel Antigen on sheep or bovine RBCs) – no longer use EBV-specific ab test (VCA IgM, IgG, EA, EBNA) Persistent antibody to Early Antigen correlated with severe diseases Atypical lymphocytes detection EBV DNA Treatment Acyclovir reduces EBV shedding but does not affect symptoms Vaccine: NOT available  Produces owl’s eye cells (intranuclear inclusions) High infection rate in childhood and early adulthood Mother to foetus – congenital infection Kaposi’s sarcoma Herpes B Virus – Herpes B virus of Old World monkeys (simian virus) highly pathogenic for humans. – An acute usually fatal ascending myelitis, encephalomyelitis.