1. Human Herpesviruses

2. 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

3. Herpesviruses Unique Features of Herpesviruses
Herpesviruses have large, enveloped icosadeltahedral capsids containing double-stranded DNA genomes.
Herpesviruses encode many proteins that manipulate the host cell and immune response.
Herpesviruses encode enzymes (DNA polymerase) that promote viral DNA replication and that are good targets for antiviral drugs.
DNA replication and capsid assembly occurs in the nucleus.
Virus is released by exocytosis, cell lysis, and through cell-cell bridges.
Herpesviruses can cause lytic, persistent, latent, and, for Epstein-Barr virus, immortalizing infections.
Herpesviruses are ubiquitous.
Cell-mediated immunity is required for control.

4. 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

5. Table 54-1. Properties Distinguishing the Herpesviruses
Body_ID: T054001
Table Properties Distinguishing the Herpesviruses
Subfamily
Virus
Primary Target Cell
Site of Latency
Means of Spread
Alphaherpesvirinae
Human herpesvirus 1
Herpes simplex type 1
Mucoepithelial cells
Neuron
Close contact
Human herpesvirus 2
Herpes simplex type 2
Close contact (sexually transmitted disease)
Human herpesvirus 3
Varicella-zoster virus
Respiratory and close contact
Gammaherpesvirinae
Human herpesvirus 4
Epstein-Barr virus
B cells and epithelial cells
B cell
Saliva (kissing disease)
Human herpesvirus 8
Kaposi's sarcoma-related virus
Lymphocyte and other cells
Close contact (sexual), saliva?
Betaherpesvirinae
Human herpesvirus 5
Cytomegalovirus
Monocyte, lymphocyte, and epithelial cells
Monocyte, lymphocyte, and ?
Close contact, transfusions, tissue transplant, and congenital
Human herpesvirus 6
Herpes lymphotropic virus
T cells and ?
Respiratory and close contact?
Human herpesvirus 7 ?
? indicates that other cells may also be the primary target or site of latency.

6.            
                                                                                                            
icosadeltahedral capsid and an envelope

7. Human herpesviruses
-DNA polymerase: -viral DNA replication -good target for antiviral drugs. -DNA replication and assembly:nucleus -buds from nuclear membrane, released by exocytosis and cell lysis. -lytic,persistant, latent, for EBV immortalizing infections

9. Disease Mechanisms for Herpes Simplex Viruses
Disease is initiated by direct contact and depends on infected tissue (e.g., oral, genital, brain).
Virus causes direct cytopathologic effects.
Virus avoids antibody by cell-to-cell spread (syncytia).
Virus establishes latency in neurons (hides from immune response).
Virus is reactivated from latency by stress or immune suppression.
Cell-mediated immunity is required for resolution with limited role for antibody.
Cell-mediated immunopathologic effects contribute to symptoms.
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10. 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

11. 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
Growth characteristics are different
HSV-2 :more potential for viremia

15. Herpes simplex virus
Initiates infection through mucosal membranes or breaks in the skin
Virus replicates in the cells at the base of the lession and infects the innervating neurons
Travels by retrograde transport to the ganglion( trigeminal ganglion for oral HSV, sacral ganglia for genital HSV)

16. Herpes simplex virus Then turns to initial site of infection
May be inapparent or vesicular( vesicle fluid contains infectious virons)
Tissue damage: viral pathology+immunopathology
Heals without a scar
Latent infection occurs in neurons

17. Herpes simplex virus
Infects most types of human cells, even cells of other species. Lytic infection of fibroblasts and epitelial cells and latent infection of neurons HSV-1 binds to heparan sulfate , a proteoglycan found on the outside of many cell types

18. Herpes simplex virus
Interacts HveC (herpes virus entry mediator C) : a member of immunoglobulin protein family similar to polio virus receptor, found on most cells and neurons Penetrates by fusion During latent infection: the only region of genome to be trancribed generates latency associated transcripts(LATs) and these RNAs are not translated in protein

19. Epidemiology Virus causes lifelong infection
Recurrent diseases is source of contagion
Asymtomatic shedding
Saliva, vaginal secretion, lesion fluid
Transmitted orally, sexually, into eye, breaks in skin
HSV-1 usually orally
HSV-2 usually sexually

20. 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

21. 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.

22. Clinical Syndromes HSV-1 and HSV-2 are common human pathogens
Painful but benign manifestations and recurrent disease
A clear vesicle on an erythematous base
Pustular lesion, ulcer, crusted lesion
Sinificant morbidity and mortality on infection of eye,brain or on disseminated infection in immunosuppressed person or neonate.

23. Clinical Syndromes Primary herpetic gingivostomatitits
Recurrent mucocutaneous HSV(cold sores, fever blister)
Herpes pharyngitis
Herpetic keratitis: corneal damage leading to blindness
Herpetic whitlow
Eczema herpeticum
Genital herpes mostly by HSV-2

25. Clinical Syndromes
-Herpes encephalitis: usually by HSV-1,the most common viral cause of sporodic encephalitis.Mortality is high. At all age, at any time of year -HSV meningitis: complication of genital HSV-2 -Neonatal infection: HSV-2, usually fatal

27. Neonatal HSV HSV-2 Either during passage through genital tract
Or rarely in utero
Postnatally from family or hospital personel
Immune system weak
Disseminates to organs
Baby is septic and vesicular lesions
Death,or mental retardation or neurological disability

28. Laboratory diagnosis
Cytology and histology: Tzanck smear(scraping of the base of a lesion), Papanicolaou smear or biopsy specimen
Cytopathic effects: syncytia, ballooning of cytoplasm, Cowdry A intranuclear inclusions
Direct antigen detection: immunofluorescence method or immunoperoxidase method
DNA :in situ hybridization or PCR in tissue or vesicle fluid

29. Laboratory diagnosis
Virus isolation: CPE in 1-3 days in HeLa, Hep-2 cells, human embryonic fibroblasts and rabbit kidney cells. Isolates are identified by immunologic methods by antigen detection by IFA.
Serology:primary infection, type specific antibody by ELISA (differentiates HSV-1 and HSV-2)

30. Direct microscopic examination of cells from base of lesion
Body_ID: T054002
Body_ID: None
Table Laboratory Diagnosis of Herpes Simplex Virus (HSV) Infections
Approach
Test/Comment
Direct microscopic examination of cells from base of lesion
Tzanck smear shows multinucleated giant cells and Cowdry type A inclusion bodies.
Cell culture
HSV replicates and causes identifiable cytopathologic effect in most cell cultures.
Assay of tissue biopsy, smear, cerebrospinal fluid, or vesicular fluid for HSV antigen or genome
Enzyme immunoassay, immunofluorescent stain, in situ DNA probe analysis, and polymerase chain reaction (PCR).
HSV type distinction (HSV-1 vs. HSV-2)
Type-specific antibody, DNA maps of restriction enzyme fragments, sodium dodecyl sulfate-gel protein patterns, DNA probe analysis, and PCR.
Serology
Serology is not useful except for epidemiology.
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31. Treatment Nucleotide analogues, viral DNA polymerase inhibitors
Prevents or shortens the course of primary or recurrent disease
Can not eliminate latent infection

32. Treatment Acyclovir Penciclovir Valacyclovir Famciclovir
Adenosine arabinoside
Iododeoxyuridine
Trifluridine

33. FDA-Approved Antiviral Treatments for Herpesvirus Infections
Herpes Simplex 1 and 2
Acyclovir
Penciclovir
Valacyclovir
Famciclovir
Adenosine arabinoside
Iododeoxyuridine
Trifluridine
Varicella-Zoster Virus
Varicella-zoster immune globulin
Zoster immune plasma
Live vaccine
Epstein-Barr Virus
None
Cytomegalovirus
Ganciclovir*
Valganciclovir*
Foscarnet*
Cidofovir*
The

34. Pregnant women Active genital HSV Asymtomatic shedding
Such transmission can be prevented by cesarean section
No vaccine available yet.

35. Varicella-Zoster Chickenpox(varicella)
With recurrence :herpes zoster-shingles:zona
Primary target cell: mucoepitelial cell
Site of latency: neuron
Means of spread: respiratory and close contact
Viremia occurs after local replication :skin lessions over the entire body

36. Disease Mechanisms of Varicella-Zoster Virus (VZV)
Initial replication is in the respiratory tract.
VZV infects epithelial cells, fibroblasts, T cells, and neurons.
VZV can form syncytia and spread directly from cell to cell.
Virus is spread by viremia to skin and causes lesions in successive crops.
VZV can escape antibody clearance, and cell-mediated immune response is essential to control infection. Disseminated, life-threatening disease can occur in immunocompromised people.
Virus establishes latent infection of neurons, usually dorsal root and cranial nerve ganglia.
Herpes zoster is a recurrent disease; it results from virus replication along the entire dermatome.
Herpes zoster may result from depression of cell-mediated immunity and other mechanisms of viral activation.
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37. Varicella-Zoster Primary VZV infection: mucosa of respiratory tract
Viremia
Reticuloendotelial system,liver,spleen
11-13 days later secondary viremia
Virus is spread through the body and skin=rash+fever+systemic symptoms

40. Varicella-Zoster
Latent in dorsal root or cranial nerve ganglia after primary infection
Reactivates in older adults and in patients with impaired immunity.
On reactivation : a vezicular rash along the entire dermatome
Children and leukemia: VZV more serious and more disseminated disease

41. Varicella-Zoster Extremely communicable
Rates of infection exceeds 90% among household contact
Contagious before and during symptoms.
HZ develops in 10-20% of people infected with VZV and contains viable virus.

42. Varicella(Chickenpox)
Five classic childhood exanthems: chickenpox, measles, roseola, fifth disease,rubella
Mild childhood disease
Fever+maculopapular rash
14 days incubation
All stages of skin lesion (vesicle, pustular, crust)
More severe on trunk even on scalp
Bacterial superinfection

43. Varicella(Chickenpox)
Severe in adults (interstitial pneumonia)
Severe in neonates and immunocompromised.

44. Herpes-zoster Recurrence of latent varicella Severe pain
Rash limited to the dermatome

46. Varicella-Zoster Laboratory diagnosis: Cytology
Virus isolation: difficult
Serology
Treatment:
ACV,famciclovir and valacyclovir
Prophylaxis: VZIG:varicella-zoster immunoglobulin:immunosuppressed patients
A live attenuated vaccine(Oka strain)

47. 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

48. Epstein-Barr Virus
Gammaherpesvirinae: Primary target cell: B cells and epitelial cells Site of latency: B cell Means of spread: saliva (kissing disease) Limited host range and tissue tropism: receptor for C3d component of the complement system (CR2 or CD21) which is expressed on B cells of humans and some epitelial cells of oro- and nasopharynx.

49. Select viral genes are expressed, depending on the state of the B cell; they include Epstein-Barr nuclear antigens (EBNAs) 1, 2, 3A, 3B, and 3C; latent proteins (LPs); latent membrane proteins (LMPs) 1 and 2
The EBNAs and LPs are DNA-binding proteins that are essential for establishing and maintaining the infection (EBNA-1), immortalization (EBNA-2), and other purposes.
The LMPs are membrane proteins with oncogene-like activity. These proteins stimulate the growth of and immortalize the B cell.
EBV establishes latency in memory B cells in which only the EBNA-1 and LMP-2 are expressed, maintaining the genome in the cells but with minimal potential for immune recognition of the infected cell.

50. Disease Mechanisms of Epstein-Barr Virus
Virus in saliva initiates infection of oral epithelia and spreads to B cells in lymphatic tissue.
There is productive infection of epithelial and B cells.
Virus promotes growth of B cells (immortalizes).
T cells kill and limit B-cell outgrowth. T cells are required for controlling infection. Antibody role is limited.
EBV establishes latency in memory B cells and is reactivated when the B cell is activated.
T-cell response (lymphocytosis) contributes to symptoms of infectious mononucleosis.
There is causative association with lymphoma in immunosuppressed people and African children living in malarial regions (African Burkitt's lymphoma) and with nasopharyngeal carcinoma in China.

51. EBV
The diseases of EBV result from either an overactive immune response (infectious mononucleosis) or
the lack of effective immune control (lymphoma and hairy cell leukoplakia).

54. Epstein-Barr Virus
EBV activate B-cell growth and prevents apoptosis(programmed cell death) T cell response (lymphocytosis) :atypical Lymphocytosis:Downey cells account for 10-80% of total white blood cells during the second week Lymph glands,spleen and liver swells Mild in children

57. Epstein-Barr Virus
Virus causes lifelong infection May cause aymptomatic shedding Recurrent disease is a cause of contagion Children:mild or asmptomatic Teenagers and adults: infectious mononucleosis Immunocompromised people: at high risk of for life threatening neoplastic disease

58. Diagnosis of Epstein-Barr Virus
Symptoms
Mild headache, fatigue, fever
Triad: Lymphadenopathy, splenomegaly, exudative pharyngitis
Other: Hepatitis, ampicillin-induced rash
Complete blood cell count
Hyperplasia
Atypical lymphocytes (Downey cells) (T cells)
Heterophile antibody (transient)
EBV-antigen specific antibody

59. post-transplant lymphoproliferative disease
Many Hodgkin's lymphomas can also be attributed to EBV
Hairy Oral Leukoplakia

61. EBV-associated neoplasms
Geographic distribution
Co-factor?
Endemic Burkett’s lymphoma: Africa:malaria
Nasopharyngeal carcinoma: China

63. Laboratory diagnosis
Heterophile antibody: results from nonspecific activation of B cells by EBV
IgM antibody recognizes Paul-Bunnell antigen on sheep, horse and bovine erythrocytes not on guinea pig kidney cells
Detected at the end of first week , lasts for several months
Monotest, ELISA: specific antibodies
VCA-IgM, antibody to early antigen (EA): recent infection
VCA-IgG, EBNA: previous infection

65. 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

66. Sources of infection
Neonate: transplacental transmission, intrauterine infection, cervical secretion
Baby or child: body secretions, breast milk, saliva, tears, urine
Adult: sexual transmission(semen), blood transfusion, organ graft

67. Clinical findings Predominant presentation: asymptomatic
Neonates: deafness, mental retardation
Immunosuppressed patients: disseminated dissease, severe disease (pneumonia, retinitis, colitis, esophagitis)

68. CMV the most common viral cause of congenital defects
particularly important as an opportunistic pathogen in immunocompromised patients

69. Congenital infection An important cause of congenital disease
Serious birth defects is high if primary infection occurs during pregnancy
Microcephaly, intracerebral calcification,hepatosplenomegaly,rash(cytomegalic inclusion disease), unilateral or bilateral hearing loss, mental retardation
CMV in the urine in the first week (culture,PCR)

70. CMV immunsupressed patients
CMV disease of the lung (pneumonia and pneumonitis) is a common outcome in immunosuppressed patients
Retinitis (%10-15 AIDS patients)
Interstitial pneumonia and encephalitis
colitis or esophagitis may develop in as many as 10% of patients with AIDS
May be related with GVHR after bone marrow transplantation

71. Table 54-6. Cytomegalovirus Syndromes
Body_ID: T054006
Table Cytomegalovirus Syndromes
Tissue
Children/Adults
Immunosuppressed Patients
Predominant presentation
Asymptomatic
Disseminated disease, severe disease
Eyes -
Chorioretinitis
Lungs
Pneumonia, pneumonitis
Gastrointestinal tract
Esophagitis, colitis
Nervous system
Polyneuritis, myelitis
Meningitis and encephalitis, myelitis
Lymphoid system
Mononucleosis syndrome, post-transfusion syndrome
Leukopenia, lymphocytosis
Major organs
Carditis,* hepatitis*
Hepatitis
Neonates
Deafness, intracerebral calcification, microcephaly, mental retardation
*Complication of mononucleosis or postperfusion syndrome.

72. . Epidemiology of Cytomegalovirus Infection
Disease/Viral Factors
Virus causes lifelong infection.
Recurrent disease is source of contagion.
Virus may cause asymptomatic shedding.
Transmission
Transmission occurs via blood, organ transplants, and all secretions (urine, saliva, semen, cervical secretions, breast milk, and tears).
Virus is transmitted orally and sexually, in blood transfusions, in tissue transplants, in utero, at birth, and by nursing.
Geography/Season
Virus is found worldwide.
There is no seasonal incidence.
Who Is at Risk?
Babies.
Babies of mothers who experience seroconversion during term: At high risk for congenital defects.
Sexually active people.
Blood and organ recipients.
Burn victims.
Immunocompromised people: Symptomatic and recurrent disease.
Modes of Control
Antiviral drugs are available for patients with acquired immune deficiency syndrome.
Screening potential blood and organ donors for cytomegalovirus reduces transmission of virus.
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73. Laboratory tests
Cytology and histology: ‘OWL’s eye’ inclusion body basophilic intranuclear:Urine not so sensitive
Antigen in peripheral leucocytes
DNA by PCR
Cell culture: Human diploid fibroblasts
Serology: primary infection

75. Treatment
Ganciclovir
Foscarnet
Valganciclovir
Cidofovir
No vaccine

76. Other mononucleosis causes
EBV
CMV
HIV
Toxoplasma gondii

77. Human herpesvirus 6 Betaherpesvirinae Lymphotropic , ubiquitous
Primary target cell: T cells and ?
Site of latency: T cells and ?
Means of spread: Respiratory, close contact
Exanthema subitum: roseola
A mononucleosis syndrome and lympadenopathy

78. Exanthema subitum High fever+rash for 24-48 hours Incubation 4-7 days
Recovery without complication

79. Human herpesvirus 8
HHV-8 DNA sequences were discovered by PCR in biopsy specimens of
Kaposi’s sarcoma (characteristic opportunistic diseases associated with AIDS)
Primary effusion lymphoma (rare type of B-cell lymphoma)
Multicentric Castleman’s disease

80. Human herpesvirus 8 Kaposi’s sarcoma-related virus
Primary target cell: Lymphocyte and other cells
Site of latency:?
Means of spread: close contact, sexual, saliva?
Limited to certain geographic areas (Italy, Greece, Africa) and AIDS

81. Human herpesvirus 8 Laboratory diagnosis:
Serology: specific antibodies:IFA IgG,IgM
HHV-8DNA by PCR

82. Herpesvirus simiae(B virus)
Asian monkeys
Bites, saliva
Encephalopathy in humans
fatal