Herpes Viruses of Humans PDF

# Herperviruses of Humans ## Subfamily/Genus: 1. Simplexvirus: - Human Herpesvirus 1: HHV-1 - Human Herpesvirus 2: HHV-2 2. Varicellovirus: - Human Herpesvirus 3: HHV-3 - (Varicella-zoster virus) VZV 3. Betahepesvirinae: - Human Herpesvirus 5: (Cytomegalovirus) CMV 4. Roseolovir...

# Herperviruses of Humans ## Subfamily/Genus: 1. Simplexvirus: - Human Herpesvirus 1: HHV-1 - Human Herpesvirus 2: HHV-2 2. Varicellovirus: - Human Herpesvirus 3: HHV-3 - (Varicella-zoster virus) VZV 3. Betahepesvirinae: - Human Herpesvirus 5: (Cytomegalovirus) CMV 4. Roseolovirus: - Human Herpes virus 6: HHV-6 5. Lymphocrptovirus: - Human Herpes Virus 4: HHV-4 - (Epstein-Barr Virus EBV) # PROPERTIES OF HERPESVIRIDAE - Spherical enveloped virion (120-200nM Diameter) - Icosahedral capsid - Linear ds DNA - Replicates in the nucleus - DNA replication and encapsidation occur in the nucleus. - Establish latent infections with genome persisting in the nucleus of neurons or lymphocytes. - Reactivation triggers replication and recurrent or continuous shedding of infectious virus. # Herpesvirus Particle - An image shows a HSV-2 virus particle. The text states that herpesviruses all have an identical morphology and cannot be distinguished from each other under electron microscopy. # REPLICATION - Infection by HHV's begins with the attachment of the virus to a cellular receptor. The virus penetrates the cell via fusion of viral envelope with the plasma membrane. # HERPESVIRIDAE - Herpesviruses have the capacity to persist in their hosts indefinitely, in the form of an episome in the nucleus of the host cell. - Host specific herpesviruses of different subfamilies occupy distinct ecologic niches, in particular types of cells within a given individual. # Simplexvirus: (HHV-1 & HHV-2) - Transmission occurs as a result of direct contact with infectious material. - Orofacial infections occur via kissing. - Genital herpes infections are acquired as a result of either: - Genital-Genital - Oral-Genital - Anal-Genital - Herpes simplex infection can also take place during asymptomatic virus shedding. - Incubation period of herpes simplex is 2-12/7 # Gingivostomatiti - An image shows a close up of a mouth with sores around the lips and on the chin. # Clinical Features - 1º infection with HHV-1 most commonly involves the mouth and/or throat. - In young children the classic clinical presentation is Gingivostomatitis. Mouth/Gums are covered with vesicles which soon rupture to form ulcers. - Following recovery from 1º oropharyngeal infection the individual retains HHV-1 DNA in the trigeminal ganglion for life with high chance of suffering recurrent attacks of herpes labialis (herpes facialis, herpes simplex, fever blisters or cold sore). # Genital Herpes - 1º genital herpes is caused by HHV-2, but an increasing of genital herpes is attributable to HHV-1. - As a STI genital herpes is seen mainly in young adults. - Ulcerating vesicular lesions develop on the vulva, vagina, cervix, urethral and/or perineum if females. Penis in males. Rectum and perianal region under some conditions. # LAB DIAGNOSIS - Some of the clinical presentation of herpes simplex such as recurrent herpes labialis are so characteristic. - Others are not nearly so clear-cut: - Encephalitis - Kerato conjuctivitis - Herpes genitalis confined to the cervix # Specimens includes: - Vesicle Fluid, CSF, or Swabs or scrapings from genital tract, throat, eye or skin. - Isolation in cell culture is then performed. - ELISA on CSF. - PCR is now the method of choice for detection of HHV-1/2 in CSF. # Chemotherapy - Acyclovir - Valcylovir - There is little benefit of treating recurrent herpes genitalis or herpes labialis. # HUMAN HERPES VIRUS 3 - (VARICELLA-ZOSTER VIRUS) HHV-3 OR VZV - HHV-3 is responsible for two human diseases - Varicella (chickenpox) - one of the exanthemata of childhood - Herpes Zoster (Shingles) common in aged and immunocompromised persons. - HHV-3 enters by inhalation and replicates in the mucosa of the respiratory tract and oropharynx. # Pathogenesis - The incubation period is 14/7. Dissemination occurs via lymphatics/blood. Virus multiplics in mononuclear leukocytes and capillary endothelial cells. - The skin rash results from multiplication of virus in epithelial cells of the skin. From the skin HHV-3 is presumed to ascend the axons of various sensory nerves to localize in sensory ganglia, where it becomes latent for life until reactivation by immunosuppression. - 1º infection is controlled by T-Cell-mediated immunity and results in prolonged immunity. - An image shows a close up of a man's torso with numerous skin sores. # Human Herpes Virus-5 - (Cytomegalovirus) HHV-5 or CMV - Of all the herpes viruses HHV-5 is the one responsible for most morbidity and mortality in immunocomprised persons. # Pathogenesis and Immunity - HHV-5 infection is acquired sub-clinically during childhood through inhalation. - Once infected with HHV-5(CMV) an individual carries the virus for life and may shed it intermittently in saliva, urine, semen, cervical secretions and/or breast milk. - During the viremia observed in acute infection 10 or during reactivation, virus can be recovered from monocytes, polymorphs and a lesser extent T Lymphocytes. # Lab Diagnosis of HHV-5 - Viral Culture (slow) - PCR for HHV-5 DNA # Rx - Ganciclovir - Foscarnet - These drugs are the drugs of choice for severe HHV-5 infections - pneumonia, chorioretinitis, or colitis. # HHV-4 genome persists in B Cells as a plasmid with relatively few genes expressed, one of the genes expressed results in B' cell immortalization (transformation). # Each immortalized cell is a B' cell clone which produces B-cell growth factor and characteristic monoclonal antibodies. # HHV-4 fall into two classes: - Type A – Most common in Europe and US commonly isolated from B lymphocytes. - Type B:- Only recovered from B cells of immunocompromised persons and is confined to mucosal epithelia and decretions therefrom. # Clinical features of HHV-4 (EBV) 1. Infectious mononucleosis (glandular fever). Incubation (4-7/52) - Complication - Neurologic :- Bell's Palsy, meningoencephalitis, transverse myelitis. - Others:- nephiritis, thrombocytopenia 2. Burkitt's Lymphoma & Nasopharyngeal Carcinoma - Burkitts Lymphoma is a malignant B' Cell Lymphoma of high prevalence in children in tropical Africa. The regular association of HHV-4 with Burkitts suggests a cause and effect relationship. # The route of HHV-8 transmission is not yet fully understood, though evidence points to sexual and solid organ transplants. # How HHV-8 contributes to the development of KS is under study? - By in situ PCR HHV-8 can be shown to infect both the spindle cells typical of advanced KS and a typical flat endothelial cells lining vascular spaces of early KS lesions. HHV-8 may contribute to cell proliferation/transformation. # Kaposi's Sarcoma - An image shows a person's forearm with a number of purple lesions.