1. Herpesviruses

2. General characteristics of Herpesviridae  1. most important human pathogens (HSV, VZV, EBV…), some wide host cell range (HSV), others have narrow host cell range (EBV).  2. different types of infection I - Primary infection I - Primary infection -1 st attack in person. -1 st attack in person. - clinically asymptomatic. - clinically asymptomatic. - followed by latent infection. - followed by latent infection. II - Latent infection - Lifelong latent infection. - Neurons (HSV,VZV) or lymphocytes (EBV, CMV). - Lifelong latent infection. - Neurons (HSV,VZV) or lymphocytes (EBV, CMV). III - Secondary infection (recurrent infection) Occur individuals those exposed to virus previously & have virus latent in the body. Occur individuals those exposed to virus previously & have virus latent in the body.  3. Herepsviruses susceptible to antiviral chemotherapy because they are large viruses, more independent of cellular function & there is more virus specific process are available as target for drug action.

3.  4. Virus Spherical in shape enveloped, large size viruses(150-200)nm in diameter, enveloped icosaherdral in symmetry.  5. Genome double-stranded DNA, linear, 125-240 kbp.  6. Replication: nucleus.  7. Herpesviruses have been linked with malignant diseases in human: a- EBV with Burkitt´s lymphoma, & nasopharyngeal carcinoma. a- EBV with Burkitt´s lymphoma, & nasopharyngeal carcinoma. b- HHV8 associated with Kaposi sarcoma. b- HHV8 associated with Kaposi sarcoma. Note that all herpesviruses have identical morphology and cannot be distinguished from each other under electron microscopy.

4. Classification of herpes viruses three subfamilies I- α -Alpha herpes viruses HSV-1 HSV-2 HSV-2 VZV VZV Characterize by Characterize by a- Wide host range. a- Wide host range. b- Efficient replication, cultivated easily in vitro. b- Efficient replication, cultivated easily in vitro. c- Establish latency in sensory ganglia ( neurons). c- Establish latency in sensory ganglia ( neurons). 2- β -Beta herpes viruses CMV CMV HHV6 HHV6 HHV7 HHV7 Characterize by Characterize by a- Narrow host range. a- Narrow host range. b- Slow replication, enlargement of the infected cells. b- Slow replication, enlargement of the infected cells. c- Site of latency secretary glands, kidney, lymphoid tissue. c- Site of latency secretary glands, kidney, lymphoid tissue. 3- γ - Gamma herpes viruses EBV & HHV8 EBV & HHV8 Characterize by Characterize by a- Narrow host range. a- Narrow host range. b- Ability to transform cell. b- Ability to transform cell. c- Latency in lymphoid cell lines, but when infect epithelial cell cause replication not latency. c- Latency in lymphoid cell lines, but when infect epithelial cell cause replication not latency.

5. Herpesviruses commonly infect humans:  1- Herpes simplex virus (HSV) - HSV1 cause primary oropharyngeal herpes. - latent in trigeminal ganglion. - cause recurrent attacks of fever blisters. - HSV 2 cause primary genital herpes. - latent in dorsal root ganglion. - HSV1 cause primary oropharyngeal herpes. - latent in trigeminal ganglion. - cause recurrent attacks of fever blisters. - HSV 2 cause primary genital herpes. - latent in dorsal root ganglion. - recurrent lesion in the genital tract. - recurrent lesion in the genital tract.  2- Varicella- Zoster virus (VZV) - Primary infection cause chickenpox (varicella) - Latent infection in neurons. - Reactivation cause zoster (shingles). - Reactivation cause zoster (shingles).  3- Epstein- Barr virus (EBV) - Primary disease is infectious mononucleosis. - Latent infection in B lymphocytes. - Reactivation occur as asymtomatic virus excretion in saliva. - Latent infection in B lymphocytes. - Reactivation occur as asymtomatic virus excretion in saliva.

6.  4- Cytomegalovirus (CMV) - Primary disease in adolescent infectious mononucleosis (heterophil negative). - Primary disease in adolescent infectious mononucleosis (heterophil negative). - Newborn cause congenital defects & mental retardation if occur during intrauterine life. - Newborn cause congenital defects & mental retardation if occur during intrauterine life. - CMV establishes lifelong latent infections. - CMV establishes lifelong latent infections. - Reactivation occur as asymptomatic virus excretion or as serious infection like CMV pneumonia in immunocompromised. - Reactivation occur as asymptomatic virus excretion or as serious infection like CMV pneumonia in immunocompromised.  5- Human herpesvirus 6 & 7 (HHV6, HHV7) - HHV6 infect lymphocytes in early infancy. - exanthema subitum ( roseola infantum ), febrile illness of children with maculopapular rash. - Target cells are not known. HHV7 T lymphotropic virus has not yet been linked to any specific disease (closely related to HHV6). HHV7 T lymphotropic virus has not yet been linked to any specific disease (closely related to HHV6).  6- Human herpesvirus 8 (HHV8) associated with Kaposi´s sarcoma common among patients with AIDS.  7- Herpes B virus of monkeys is highly pathogenic for humans. Transmissibility of virus to humans is limited, but infection when occur are associated with high mortality rate ( ~ 60%). B virus disease of humans is an acute ascending myelitis & encephalomyelitis.

7. Herpes Simplex Virus (HSV) Introduction HSV infection widespread, replicate in many types of cells (epithelial cells of oropharynx, eye, genital tract, neurons), virus grow rapidly. HSV infection widespread, replicate in many types of cells (epithelial cells of oropharynx, eye, genital tract, neurons), virus grow rapidly. HSV establish latent infections in nerve cells, & recurrence are common.  Properties of virus: spherical, enveloped, with icosahedral nucleocapsid, genome is double stranded DNA with 150 kbp. Types of Herpes simplex virus  Two distinct types HSV1. HSV2. Differences between two types  a- The genome sequence homology similar is 80%, distinguished by restriction enzyme analysis of viral DNA.  b- The two viruses cross react serologically, but unique proteins exist for each type ( specific antigen).  c- Mode of transmission. HSV1 spread by contact with infected saliva. HSV2 is transmitted sexually or from a maternal genital tract to newborn. HSV1 spread by contact with infected saliva. HSV2 is transmitted sexually or from a maternal genital tract to newborn.

8. Pathogenesis of herpes simplex infection  Source Human with symptomatic or asymptomatic infection.  Mode of transmission HSV1 the virus is transmitted by respiratory droplets or by direct contact with infected saliva. HSV1 the virus is transmitted by respiratory droplets or by direct contact with infected saliva. HSV2 transmitted by contact with genital secretion. HSV2 transmitted by contact with genital secretion.  Spread Viral replication occur first at the site of infection (local lesion), then invade local nerve endings & transported retrogradly to axonal flow to reach the site of latent infection in neuronal ganglion. Viral replication occur first at the site of infection (local lesion), then invade local nerve endings & transported retrogradly to axonal flow to reach the site of latent infection in neuronal ganglion.  HSV latent infection Site: HSV1 trigeminal ganglia, HSV2, sacral ganglia. Site: HSV1 trigeminal ganglia, HSV2, sacral ganglia. State: virus resides in infected ganglia in non replicating state. State: virus resides in infected ganglia in non replicating state. Period: ( life long latency). Period: ( life long latency). Eradication: Virus cannot be eradicated from the host even by antiviral drugs. Eradication: Virus cannot be eradicated from the host even by antiviral drugs.  Reactivation Spontaneously or following stimuli (axonal injury, fever, physical stress, emotional stress, exposure to UV, menstrual cycle, immunosuppresion). Immunity in the host limits local viral replication so that lesion are less extensive & less sever. Spontaneously or following stimuli (axonal injury, fever, physical stress, emotional stress, exposure to UV, menstrual cycle, immunosuppresion). Immunity in the host limits local viral replication so that lesion are less extensive & less sever.

9.  Spread after reactivation Virus follows nerve axons back to the peripheral site and replication proceeds in the skin or mucous membrane (vesiculo-ulcerative lesion). HSV1 to oral mucosa, eye. HSV2 genital mucosa.

10. Clinical disease (HSV1, HSV2) I. Oropharyngeal disease  1- Primary HSV-1 infection Children ( 1- 5 years) - herpetic gingivostomatitis. - I.P 3-5 days. - herpetic gingivostomatitis. - I.P 3-5 days. - fever, sore throat. - fever, sore throat. - vesiculo-ulcerative lesions of buccal & gingival mucosa & submandibular lymphadenopathy. - vesiculo-ulcerative lesions of buccal & gingival mucosa & submandibular lymphadenopathy. Adults Adults - herpetic pharyngitis & tonsillitis. - herpetic pharyngitis & tonsillitis. - Localized lymphadenopathy. - Localized lymphadenopathy.  2- Recurrent infection - herpes labials (fever blister). spontaneous reactivation or following certain stimuli (fever, stress, menses). - herpes labials (fever blister). spontaneous reactivation or following certain stimuli (fever, stress, menses). - Lesion localized at border of the lip. - Lesion localized at border of the lip. - pain occur at the onset & lesion appear as a cluster of vesicles. - pain occur at the onset & lesion appear as a cluster of vesicles. - Progress through pustular lesion & crusting stage, heal without scarring in 8-10 days. - Progress through pustular lesion & crusting stage, heal without scarring in 8-10 days. Primary herpes simplex virus gingivostomatitis in a child, extending to involve the cheek, chin and periocular skin.

11. II. Keratoconjunctivitis  Primary infection with HSV-1 occur in the eyes producing, sever kerato conjunctivitis (red eye with pain). with HSV-1 occur in the eyes producing, sever kerato conjunctivitis (red eye with pain).  Recurrent lesions occur as denderitic keratitis, common appear as corneal ulcer or as vesicles on the eyelids. Recurrent herpetic keratitis cause permanent corneal opacity & blindness. occur as denderitic keratitis, common appear as corneal ulcer or as vesicles on the eyelids. Recurrent herpetic keratitis cause permanent corneal opacity & blindness. III. Genital herpes  Primary genital herpes Acquired sexually & can be sever lasting for 3 weeks. Most cases caused by HSV2. vesiculo-ulcerative lesions of male genitalia, & female - cervix, vagina & perineum. Most cases caused by HSV2. vesiculo-ulcerative lesions of male genitalia, & female - cervix, vagina & perineum. Lesion is very painful with fever & inguinal lymphadenopathy. Viral excretion persist for about 3 weeks. Lesion is very painful with fever & inguinal lymphadenopathy. Viral excretion persist for about 3 weeks. The virus become latent in sacral ganglion. The virus become latent in sacral ganglion.  2- Recurrent genital herpes Common & tend to be mild (vesiculo-ulcerative lesion of genital tract), virus excretion last for few days. Recurrence may be asymptomatic presented with virus excretion.

12. IV. Skin infections  1- Localized infection herpes caused by HSV-1 or HSV-2, as a result of abrasions contaminated with virus. herpes caused by HSV-1 or HSV-2, as a result of abrasions contaminated with virus. Lesion seen in the figures of dentists & hospital personnel (contaminated with saliva) herpetic whitlow & body of wrestlers ( herpes gladiatorum). Lesion seen in the figures of dentists & hospital personnel (contaminated with saliva) herpetic whitlow & body of wrestlers ( herpes gladiatorum).  2- Generalized infection Sever & life threatening condition in individuals with skin disease such as eczema (Eczema herpeticum) or burns that permit viral replication & spread. There is high fever & extensive vesiculation of skin over large area. There is high fever & extensive vesiculation of skin over large area. V. HSV Encephalitis Sever form of encephalitis (mostly HSV1 lesser HSV2), mortality 80% without treatment. Sever form of encephalitis (mostly HSV1 lesser HSV2), mortality 80% without treatment.  This infection may be primary or recurrent from latent virus.  In adults & older children the neurological manifestation suggest a lesion in the temporal lobe, pleocytosis chiefly lymphocytes in CSF.  Diagnosis needed urgently a- Immunofluorescent test is the method of choice. a- Immunofluorescent test is the method of choice. b- Hybridization using labeled DNA probes. b- Hybridization using labeled DNA probes. c- PCR will provide rapid results. c- PCR will provide rapid results. d- Serology by measure IgM in CSF or serum. d- Serology by measure IgM in CSF or serum.

13. VI. Neonatal herpes simplex infection  Primary infection of neonates with HSV, results in sever herpetic disease (mortality is 50%) because of inability to limit viral replication & spread (immature immunity).  About 75% of neonatal herpes infection caused by HSV-2.  Source newborn acquire the infection  1- Prenatally during intrauterine period. 2- Natally ( ≥ 75%) during delivery, contact with herpetic lesions in birth canal. 3- Postnatally acquired through exposure to HSV-1 or HSV-2 from family members & hospital personnel. 3- Postnatally acquired through exposure to HSV-1 or HSV-2 from family members & hospital personnel.  Neonatal herpes almost always symptomatic, three forms almost always symptomatic, three forms 1- Lesion localized to skin, eye, & mouth. 1- Lesion localized to skin, eye, & mouth. 2- Encephalitis with or without localized skin involvement. 2- Encephalitis with or without localized skin involvement. 3- Disseminated disease involving multiple organs including CNS, mortality 80% & those survive left with permanent neurological deficit. 3- Disseminated disease involving multiple organs including CNS, mortality 80% & those survive left with permanent neurological deficit. The cause of death of babies with disseminated disease is usually viral pneumonitis or intravascular coagulopathy. The cause of death of babies with disseminated disease is usually viral pneumonitis or intravascular coagulopathy.

14. VII. Infection in immunocompromised patients  Sever HSV infections occur among patients with impaired immunity like those with cytotoxic therapy, transplants patients, haematological malignancies, & those with AIDS.  Mortality > 80%.  Most disease reflect reactivation of latent HSV infection.  Clinically the disease presented as 1- Respiratory tract ( HSV pneumonia). 1- Respiratory tract ( HSV pneumonia). 2- Intestinal mucosa, liver (HSV hepatitis). 2- Intestinal mucosa, liver (HSV hepatitis).

15. LABORATORY DIAGNOSIS  1- General cytological changes scraping or swab from the base of lesion contain multinucleated giant cells that are indicative for HSV infection.  2- Direct detection a- Electron microscopy of vesicle fluid, show virus particles. b-Immunoflouresent stain of swab from the skin lesion c-PCR, used routinely for the diagnosis of herpes simplex encephalitis c-PCR, used routinely for the diagnosis of herpes simplex encephalitis  3- Isolation & identification of virus Samples from throat wash, skin, eye, brain, genital lesions. Inoculated onto cell monolayer (HEP-2) & monitored for the development of characteristic cytopathic effect (swollen & rounded cells in cell culture. Inoculated onto cell monolayer (HEP-2) & monitored for the development of characteristic cytopathic effect (swollen & rounded cells in cell culture. This is usually detected within in 2-3 days. The virus can be further identified by immuno fluorescent s taining with specific antiserum. This is usually detected within in 2-3 days. The virus can be further identified by immuno fluorescent s taining with specific antiserum.  4- Serology Specific antibodies appear in 4-7 days after infection. Tests CF, RIA, ELISA. measurement of type specific antibodies (rising titer of IgG, or specific IgM). Positive immunofluorescence test for HSV antigen in epithelial cell. Cytopathic Effect of HSV in cell culture HEP-2: Note the ballooning of cells.

16. LABORATORY DIAGNOSIS Positive immunofluorescence test for HSV antigen in epithelial cell. Cytopathic Effect of HSV in cell culture HEP-2: Note the ballooning of cells.

17. Treatment  Several antiviral drugs proved effective against HSV infection, all are inhibitors of viral DNA synthesis through inhibition of viral polymerase.  It inhibit herpesvirus replication & suppress clinical manifestation.  Types of antiviral drugs  1- Acyclovir: Non toxic drug, it is used locally, orally, intravenously. Drug of choice for treatment of the following herpetic conditions: A- Herpes encephalitis. B- Herpetic keratitis. C- Ezema herpeticum.  D- Immunocompromised.  2- Vidarabine effective for herpes infection, but is more toxic used to treat infection caused by acyclovir resistant isolates of HSV.