Viruses DNA viruses: 6 families Poxviridae Herpesviridae Adenoviridae Hepadnaviridae Papovaviridae Parvoviridae
Human herpesviruses Three subfamilies (genome structure, tissue tropism, cytopathologic effect, site of latent infection) Alphaherpesvirinae: Human herpesvirus 1 Herpes simplex type 1 HSV-1 Human herpesvirus 2 Herpes simplex type 2 HSV-2 Human herpesvirus 3 Varicella-zoster virus VZV Gammaherpesvirinae Human herpesvirus 4 Epstein-Barr virus EBV Human herpesvirus 8 Kaposi s sarcoma related virus HHV-8 Betaherpesvirinae Human herpesvirus 5 Cytomegalovirus CMV Human herpesvirus 6Herpes lymphotropic virus HHV-6 Human herpesvirus 7 Human herpesvirus 7 HHV-7
Human herpesviruses Three subfamilies (genome structure, tissue tropism, cytopathologic effect, site of latent infection) Alphaherpesvirinae: Human herpesvirus 1 Herpes simplex type 1 HSV-1 Human herpesvirus 2 Herpes simplex type 2 HSV-2 Human herpesvirus 3 Varicella-zoster virus VZV Gammaherpesvirinae Human herpesvirus 4 Epstein-Barr virus EBV oncogenic Human herpesvirus 8 Kaposi s sarcoma related virus HHV-8 oncogenic Betaherpesvirinae Human herpesvirus 5 Cytomegalovirus CMV: congenital infection Human herpesvirus 6Herpes lymphotropic virus HHV-6 Human herpesvirus 7 Human herpesvirus 7 HHV-7
Human herpesviruses
Human herpesviruses Large, enveloped double stranded DNA viruses Sensitive to acid, solvents, detergents and drying
Human herpesviruses They have common: Virion morphology Basic mode of replication Capacity to establish latent and recurrent infections, in case of EBV immortalizing infections Ubiquitous Usually cause benign disease especially in children In immunosuppressed people they cause significant morbidity and mortality
Human herpesviruses -DNA polymerase: -viral DNA replication -good target for antiviral drugs. -lytic,persistant, latent, for EBV immortalizing infections
Herpes simplex virus Two types: HSV-1 and HSV-2 HSV can infect most types of human cells and even cells of other species. Lytic infection of fibroblasts and epitelial cells but latent infection of neurons The primary target cell: mucoepitelial cells Site of latency: neurons
Herpes simplex virus Means of spread: HSV-1 close contact, HSV-2 close contact+sexual transmission! Generally cause infection at the site of infection HSV-1: infections above the waist HSV-2: infections below the waist
Herpes simplex virus
Herpes simplex virus
Herpes simplex virus
Herpes simplex virus
Herpes simplex virus Recurrence: stress, trauma, fever, sunlight) The virus travels back down the nerve causing lessions at the dermatome Recurrences are less severe and more localized
HSV-1 is common 90% have antibody by 2 years of age HSV-2 occurs later in life with sexual activity Physicians,nurses,dentists at risk for infection of fingers (herpetic whitlow) Immunocompromised people and neonates at risk of disseminated, life-threateneing disease.
Laboratory diagnosis Direct antigen detection DNA :PCR in tissue or vesicle fluid
Laboratory diagnosis Serology:primary infection, type specific antibody by ELISA (differentiates HSV-1 and HSV-2)
Varicella-Zoster Chickenpox(varicella) With recurrence :herpes zostershingles:zona Primary target cell: mucoepitelial cell Site of latency: neuron Means of spread: respiratory and close contact
Chickenpox(varicella)
Shingles
Varicella-Zoster Extremely communicable Rates of infection exceeds 90% among household contact Contagious before and during symptoms Vaccine.
Epstein-Barr Virus Heterophile antibody-positive infectious mononucleosis Chronic disease Associated with endemic Burkitt s lymphoma, Hodgkin s disease, nasopharyngeal carcinoma, B-cell lymphomas in patients with acquired or congenital immunodeficiencies. Hairy oral leukoplakia Mitogen for B cells and immortalizes them
Epstein-Barr Virus Gammaherpesvirinae: Primary target cell: B cells and epitelial cells Site of latency: B cell Means of spread: saliva (kissing disease).
EBV-associated neoplasms Geographic distribution Co-factor? Endemic Burkett s lymphoma: Africa:malaria Nasopharyngeal carcinoma: China
Cytomegalovirus(CMV) Betaherpesvirnae: lymphotropic Primary target cell: monocyte, lymphocte, epitelial cell Site of latency: monocyte, lymphocyte and? Means of spread: close contact, transfusions, tissue transplant and congenital
Congenital infection
Congenital infection An important cause of congenital disease Serious birth defects is high if primary infection occurs during pregnancy Microcephaly, intracerebral calcification,hepatosplenomegaly,rash(cytomega lic inclusion disease), unilateral or bilateral hearing loss, mental retardation CMV in the urine in the first week (culture,pcr)
Laboratory tests Antigen in peripheral leucocytes DNA by PCR Cell culture: Human diploid fibroblasts Serology: primary infection
Human herpesvirus 8 Kaposi s sarcoma related virus HHV-8 (especially in HIV /AIDS)