AdenovirusesAdenoviridae

1
Adenoviruses Adenoviridae

• Characteristics
• double stranded DNA viruses linear molecular
• non-enveloped, icosa hedral particles 70 - 90 nm
• vertices exhibit viral attachment protein(VAP) as
  fibers or spikes
• possess hemagglutinin, and type-specific viral
  antigen
• capsid proteins are toxic to host cell and may
  inhibit cellular synthesis
• viral genome encodes many viral proteins
• early proteins promote the growth the infected
  cell
• E1A/E1B viral proteins bind and inactivate
  cellular p53 and RB(p1050 genes, thus stimulating
  cells growth
• virus also provides its own DNA dependent DNA
  polymerase
• some viral proteins suppress the host immune
  response including inflammation
• late proteins provide structural proteins and
  those carried in mature virion
• viral cycle takes 32 - 36 hours and produces 10,
  000 virions
• virus enters the cell by endocytosis, lyses the
  endosomal vesicle, and capsid is removed as it
  delivers the DNA to the nucleus
• 51 human adenoviruses in groups A - F
• based upon DNA homology, disease tropism, and
  fiber antigens

2
Trophisms of Adenoviruses

• Pathogenesis
• Permissive cells which best replicate
  adenoviruses tend to be from epidthelial
  (ectodermal) origin.
• viruses infect lymphoid tissues, respiratory
  epithelium, gastrointestinal epithelium, and
  conjunctiva
• permissive cells will ultimately exhibits lysis
  and death
• most of the above mucoepithelial diseases result
  from cell lysis
• non-permissive cells exhibit latency
• mostly in lymphoid tissues like tonsils,
  adenoids, or Peyers patches
• rodent cells infected with human adenoviruses
  become malignant
• Viremia is not commom, but may occur in
  immunocompromised individuals also recurrence
  from latency may occur as a result of
  immunocompromise.

3
Pathogenesis of Adenovirus Infections

• Cytopathology
• dense, central, intranuclear inclusion bodies
  composed of DNA and protein
• associated mostly with epithelial cell necrosis
  and mononuclear cell infiltrates
• no cellular enlargement(cytomegaly) as seen in
  other DNA viruses
• Immune Avoidance Mechanisms
• blocks the stimulation of anti-viral protein by
  interferon
• prevent expression of class I major
  histocompatibility antigen on the surface of
  macrophages, Thus no processed antigen is
  delivered to cytotoxic T-cells.

4
Adenovirus Diseases/Infections

• Acute febrile pharyngitis Serotypes 1 -7
• nasal congestion, cough, coryza, malaise, fever,
  myalgia, and headache
• pharyngitis (with no other symptoms often mimic
  Streptoccal disease)
• Pharyngoconjunctival fever Serotypes 1 -7
• pharyngitis accompanied by conjunctivitis
• Acute Respiratory Infection often mimic the
  common cold
• fever, cough, pharyngitis, cervical adenitis,
  laryngitis, croup, and bronchiolitis
• remember the common cold seldom has fever
• Epidemic Keratoconjunctivitis
• follicular conjunctivitis in which the mucosa of
  the palpebral (eyelid) conjunctiva becomes
  pebbled or nodular and inflamed
• Gastroenteritis and Diarrhea Acute viral
  gastroenteritis
• enteric adenovirues group F(serotypes 40, 41,
  42)
• Systemic Infection in Immunocompromised Patients
• Acute Hemorrhagic Cystitis

5
Diagnosis of Adenovirus Disease

• Diagnosis clinical and epidemiological
• viral antigen detection
• host antibody response
• viral culture
• cytopathatic effects

6
Epidemiology of Human Adenoviruses

• Epidemiology
• many variations of the person-to-person, mode of
  transmission
• respiratory droplet(aersol), close contact,
  fecal-oral, fomite
• a non-enveloped virus which is stable to drying,
  detergents, GI secretions, choline, including
  chlorinated swimming pools
• Immunity
• specific humoral immunity (antibody) in response
  to lytic infections is necessary for resolution
  and prevention of re-infection
• cell mediated immunity in necessary to prevent
  viral spreading or outgrowth

7
Herpeviruses Herpesviridae

• Characteristics
• large enveloped, double stranded DNA viruses
• genome encodes for proteins which regulate viral
  m-RNA synthesis by the cells DNA dependent RNA
  polymerase
• genome also encodes for proteins which regulate
  viral DNA replication
• provide for their own DNA dependent DNA
  polymerase
• genome also encodes proteins which slow down or
  stop the cells ability to synthesize its own DNA,
  RNA, and proteins
• DNA replication and assembly occur in the nucleus
• virus buds through the nuclear membrane, and is
  released from the cell by exocytosis or by lysis
• herpesviruses infections can result in lysis,
  latent persistence, and oncogenesis(immortalizatio
  n)
• as a group they have a significant tendency
  toward latent persistence in semi-permissive
  cells
• viruses in this group are very common
• the hosts ability to control herpesvirus
  infections requires cell-mediated immune response

8
Herpesvirus Cycle

• Virus Cycle
• viral glycoproteins(VAPs) bind virus to host
  cell receptors
• viral trophism is governed by this affinity
• virus fuses with the host cell membrane this
  removes the envelope and releases then
  nucleocapsid into the cytoplasm
• the virus particle carries carries some enzymes
  and transcription factors which begin the
  replication cycle
• nucleocapsid binds to the nuclear membrane and
  releases the genome into the nucleus of the host
  cell
• early proteins facilitate transcription of viral
  genome and include the DNA dependent DNA
  polymerase viral genome is transcribed by the
  cellular DNA dependent RNA polymerase
• late proteins are structural and are synthesized
  after DNA is replicated
• viral genome replication requires viral DNA
  dependent DNA polymerase
• cells that promote latency restrict viral
  transcription of early and late proteins
• cells that complete early and late protein
  synthesis will die
• viruses are assembled in the nucleus and bud
  through the nuclear membrane
• viruses exit the cell via exocytosis or via cell
  lysis

9
Herpes simplex Viruses I/II

• Alpha Herpesviruses
• pathogenesis
• HSV can infect most types of human cells
• infection is generally lytic in permissive
  fibroblasts and epithelial cells
• latent infection occurs in semipermissive neurons
• the glycoprotein receptors bind to heparin
  sulfate found on many cell membrane
• a special fusion protein promotes the penetration
  into the host cell and loss of the envelope
• viral particle carries several proteins
• one initiates virus transcription another is a
  cytotoxic protein and kinase
• one early protein, latency-associated
  transcripts, inhibits viral replication and
  promotes latency in semipermissive cells
• early protein enzymes include viral DNA dependent
  DNA polymerase
• other early proteins inhibit cellular DNA and RNA
  synthesis and cause the degradation of the
  cellular DNA and RNA
• some early viral based products enable the virus
  to escape immune detection
• after genome is replicated, late genes capsid
  proteins which are transported back to the
  nucleus for assembly
• envelope glycoproteins are incorporated into the
  nuclear membrane

10
Herpes simplex Viruses I/II Pathogenesis

• viruses infect mucoepithelial cells and establish
  latency in the innvervating neurons
  (semipermissive cells)
• cause lytic infections of most cells, and latent
  persistence in neurons
• cellular lysis(cytolysis) follows inhibition of
  cellular macromolecular synthesis, degradation of
  host DNA, etc
• Cowdry type A acidophilic intranuclear inclusion
  bodies form
• some strains cause syncytia formation
• HSV -1 generally causes lesions above the waist
• HSV -2 generally causes lesion below the waist
• Viremia is rarely observed except in
  immunocompromised pat
• viruses enter through breaks in skin or mucous
  membranes
• virus replication in mucoepithelial cells results
  in vesicle formation
• vesicular fluid contains infectious virions
• simultaneouly the virus infects the innervating
  neuron trigeminal or sacral nerve
• this establishes the basis for latency and
  recurrence
• virus may move from cell-cell thus evading immune
  response

11
Herpes simplex Viruses I/II

• Immunity
• Humoral and cellular immunity are necessary for
  the HSV infection to be controlled and resolved
• during the primary infection interferon and
  natural killer cells limit spreading
• during subsequent infections humoral antibody
  limits spreading
• cytotoxic T-cells and activated macrophages
  resolve the current infection
• these immune responses are the basis for symtoms
• antibody directed against the glycoprotein spikes
  limits its spreading
• since the effect of antibody may be reduced by
  expression of Fc and complement receptors, cell
  mediated immunity is required for complete
  resolution of the infection
• Latent infection
• occurs in neurons stimulated by physiological and
  anatomical stress
• stress causes recurrence by causing reactivation
  of viral genome
• virus moves down nerve and buds near a dermatome
• recurrent infections are generally less severe
• antibody does not prevent reoccurrence

12
Herpes simplex I/II- Clinical Diseases

• Herpes labialis Fever Blisters, Cold Sores
• clear vesicles on erythematous base, which
  ulcerates and crust over
• mostly caused by HSV-1 sometimes HSV-2 in adults
• often re-occurs when virus buds from sensory
  neuron
• Herpetic gingivostomatitis
• complication of Herpes labialis with lesions on
  the oropharynx
• mostly occurs in children and involves HSV-1
• Herpes pharyngitis in young adults involving
  HSV-1/2
• Herpetic keratitis severe infection of the eye
• may cause corneal damage leading to blindness
• mostly due to re-occurrence(budding) of HSV-1
  into the eye
• Herpetic whitlow/ gladiatorium cutaneous
  vesicles on the hands or body involving HSV- 1
• wrestlers, thumb-sucking children, health care
  professionals

13
Herpes simplex I/II Clinical Diseases

• Eczema herpeticum primary infection of
  preexisting eczema (dermatitis) causing spread
  of herpetic vesicles HSV-1
• Herpes genitalis Genital herpes
• mostly involves HSV-2 sometimes HSV-1
• painful, itching, vesicular lesions
• males glans or shaft of penis sometime in the
  urethra
• femalevulva, cervix(mucoid vaginal discharge),
  perianal area, inner thighs
• accompanied by fever, malaise myalgia and
  sometimes inguinal adenitis
• periodic recurrence involves budding of HSV-2
  from the sacral nerve
• Herpetic proctitis vesicles in lower rectum and
  anus
• Herpes encephalitis
• acute febrile illness involving HSV-1
• immunopathology causes destruction of temporal
  lobe causing seizures, focal neurological
  abnormalities, headache, fever, etc.
• most common type of sporadic viral encephalitis
  high mortality

14
Herpes simplex 1/II Clinical Diseases

• HSV meningitis
• milder neurological complication of HSV-2
  infections
• Neonatal Herpes
• devastating and often fatal disease of newborns
  involving HSV-2
• most often acquired perinatally from infected
  mothers
• occasional congenital transmission
• since neonatal cellular immune mechanisms are
  usually not well developed at birth, the virus
  disseminates to liver, lung, CNS, and other
  organs
• Lesion develop on skin, in eyes and mouth
• 50 mortality from viral pneumonitis or
  intravascular coagulopathy
• 80 from dissemination to the brain resulting in
  encephalits

15
Herpes simplex - Epidemiology

• HSV-1 is probably more constantly present in
  humans than any other virus
• Most children are infected by age 3
• Person-to-person, direct, salvia
• Person-to-person, indirect, eating utensils
• Most children get the virus from symptomatic or
  asymptomatic parents
• Antibodies develop following primary infection,
  but do not eliminate virus from the body
  intracellular latency
• Approx 80 of developed populations habor latent
  HSV-1
• HSV-2 is the third most common STD behind
  Chamydia and HPVs
• Person-to-person, direct, sexual
• 40 -60 million infected persons in the U.S.
• Only 20 of these possess detectable antibody

16
Herpes simplex 1/II - Epidemiology

• Reservior is humans who have acute or
  asymptomatic infection
• because of latency, a person is infected for a
  life time
• HSVs are exclusively human pathogens
• being enveloped, they are readily inactivated by
  drying, detergents, and other adverse conditions
  such a the GI tract
• Thus, are transmitted by direct contact, both
  sexual and nonsexual
• Also fingers and exchange of oral fomites
• may be autoinoculated from oral/genital lesions
  to other areas
• HSV-1 is very common as observed by symptoms an
  antibody studies
• HSV-2 is spread most by sexual contact and is the
  third leading sexually transmitted microorganism
  in the U.S.
• HSV-2 is also an etiological agent of cervical
  cancer, or at least a cofactor along with HPV
  and other organisms in the development of this
  carcinoma

17
Herpes simplex 1/II - Diagnosis

• Cytology using scrapings from vesicles
• Tzanck smear, Papanicolaou smear, Biopsy
• CPEs such a multinucleated giant cells and
  Cowdry type A intranuclear inclusions
  presumptive diagnosis
• Viral antigen detection
• immunofluorescence or immunoperoxidase(EIA)
• Nucleic acid detection
• DNA hybridization
• gene probes
• Virus Isolation -vesicular fluid introduced into
  tissue cultures (HeLa cells), human fibroblasts,
  rabbit kidney) show CPE in 1 -3 days
• cells are enlargedballooned with cell fusion
  creating giant cells or syncytia
• Serology - only for primary infections detects
  presence of antibody

18
Varicella-Zoster Virus

• AlpHerpesVirus 3
• Similar to HSV, but has smaller genome,
  replicates slowly, and infects a narrower
  spectrum of cell types
• establishes latent infection in neurons
• recurrent infection along innervated dermatomes
• requires cell mediated immunity to control and
  prevent
• vesicular, blister-like, lesions
• differs from HSV in mode of transmission
• mostly via p-p, direct, respiratory droplet
• systemically spread by viremia through entire body

19
Varicella-Zoster Virus - Pathogenesis

• Primary infection in the cells of the respiratory
  mucous, epithelial cells and fibroblasts
  cell-to-cell spreading to regional lymph nodes
• primary viremia( blood and lymph) moves virus to
  reticuloendothelial system
• secondary viremia moves virus from RES via the
  blood though the entire body including the skin
• Symptoms include fever, malaise, and pathomonic
  vesiculopustular rash that appears in successive
  crops beginning on head/neck, then thorax, and
  finally extremities
• Virus becomes latent in semipermissive cells of
  dorsal root ganglia and/or cranial nerve ganglia
• antibody limits viremia spread, but cell-mediated
  immunity is required for complete resolution of
  infection.
• infection in adult is more serious, than in
  children
• a phenomenon associated with differences in
  cell-mediated response

20
Varicella-Zoster Virus Clinical Disease

• Shingles Herpes zoster
• is a recurrent manifestation of VZV acquired
  earlier in life as chickenpox
• virus buds through the nerves along the thoracic
  dermatomes or along the trigeminal nerve
• painful vesicular lesions having an erythematous
  basedevelop along these nerves
• Postherpetic neuralgia
• chronic pain along the dermatomes which persists
  from years following a bout of shingles
• occurs in 30 of patients older than 65 year of
  age

21
Varicella-Zoster Virus Clinical Disease

• Chickenpox classic childhood exanthem
• a mild childhood disease with symptoms of fever
  and maculopapular rash which follows a 14 day
  incubation period
• the vesicle is the hallmark of Varicella
• maculopapular lesion forms a thin walled
  vesicle(dew drop) - 2-4 mm
• vesicle becomes pustular and crusts over forming
  a scab
• successive crops of vesicles appear over 3-5
  days at any given time all stages of skin
  lesions can be observed
• lesions are generalized beginning on the scalp,
  spreading over face and neck to the trunk where
  they are most severe and noticable
• lesions may also appear on mucous membrane of the
  mouth, conjunctiva, and vagina
• rash may hemorrhage in cases of thrombocytopenia
• Interstitial pneumonia
• a severe complication of VZV infection in adults
• 20 -30 of adults with VZV infection and may be
  fatal

22
Varicella-Zoster - Diagnosis

• Cytology
• Cowdry type A intrnuclear inclusion bodies in
  infected cells
• also syncytia observed
• Tzanck smears from base of vesicles reveal
  multinucleated giant cells (syncytia
• Antigen detection from skin lesions, biopsy
  specimens
• Direct florescent antibody - most sensitive
• Virus isolation in human diploid fibroblasts
  CPE
• Serology
• presence of IgM or four fold increase in IgG
• ELISA is most quantitative

23
Varicella- Zoster Virus - Epidemiology

• Epidemiology
• Chickenpox
• VZV is extremely communicable
• Reservoir infected humans either symptomatic
  or asymptomatic
• Primary Mode of Transmission p-p, direct,
  respiratory droplet
• Secondary Route direct contact with active
  vesicles
• Shingles
• Is a reactivation disease resulting from
  previous VZV infection
• Is generally not considered a communicable
  condition
• Exception
• There are a few documented cases of transmission
  from and adult with shingles to a young child
• Child developed chickenpox

24
Varicella-Zoster Virus - Control

• Chickenox
• Isolation of Infected Individuals
• Active Attenuated Vaccine or VZV immunue
  globulin
• induces both humoral and cell-mediated immunity
• Shingles
• Theoretically, control of chickenpox should
  reduce latency in neurons and ultimately reduce
  the amount of re-current symptoms in the form of
  shingles

25
Epstein-Barr Virus - Characteristics

• Gammaherpes Virus
• very limited host range and tissue trophism
• range is defined the C3d complement receptor
• C3d is expressed on B-cells, and epithelial cells
  of the oropharynx nasopharynx, and salivary
  glands

26
Epstein-Barr Virus Clinical Diseases

• Infectious Mononucleosis
• high fever, malaise, pharyngitis,
  lymphadenopathy, and often hepatosplenomegaly
  occasional rash
• lymphocytosis
• heterophile postive
• most common complaint is fatigue
• generally mild or symptomatic in children
• most severe in adolescents and adults
• often referred to as heterophile positive
  mononucleosis
• sometimes has neurological complications
• Meningoencephalitis Guillan-BarreSyndrome
• Incubation period 30-60 days
• Carriers shed virus for weeks, sometimes months
• Symptoms last 2-4 weeks T-cells self-limits
  disease

27
Epstein-Barr Virus Clinical Diseases

• Chronic mononuclesis-like disease
• recurrent and cyclical
• characterized by chronic fatigue
• Lymphoproliferative Diseases
• Hairy Oral Leukoplakia unusual presentation of
  EBV productive infection of the epithelial cells
  of the mouth/tongue in immunocompromised
  patients
• Burkitts Lymphoma AfBL
• monoclonal B-cell lymphoma of the jaw and face
  due to immortalization of B-cells
• malaria seems to enhance this manifestation in
  Africa
• mostly seen children
• tumors express EBNA-1 viral antigen lymphocyte
  derived tumors

28
Epstein-Barr Virus Virus Cycle

• Virus transcription pattern governs the outcome
  of infection
• Lytic infection
• occurs in permissive cells mostly respiratory
  epithelial cells
• ZEBRA protein activates early genes
• virus provides for its own DNA dependent DNA
  polymerase
• several glycoproteins synthesized and
  incorporated into the nuclear membrane
• virus is released by lysis
• Infected cells express Late antigens
• Viral capsid antigen
• Viral envelope glycoproteins

29
Epstein-Barr Virus Virus Cycle

• Latent infection
• The major target cell for EBV is the B-lymphocyte
• B-cells become transformed or immortalized and
  begin a pattern of uncontrolled cell division
• infected cell contain a small number of circular
  plasmid-like EBV genomes which are replicated
  when the cell is actively dividing
• in this cycle several viral coded proteins are
  produced which promote latency, immortalization,
  and sometimes oncogenesis
• EBNAs
• latent proteins (LP)
• latent membrane proteins (LMP)
• EBER - Epstein Barr Encoded RNA
• occurs in semi-permissive B-cells
• lt10 of immortalized cells release active virions

30
Epstein-Barr Virus- Pathogenesis

• Productive infection of epithelial cells in the
  oropharynx
• virus is shed into lymphatics and blood and
  infects B-cells
• Basis of pharyngitis
• EVB binds to the C3d receptors on B-lymphocytes,
  penetrates into the cells by fusion, DNA is
  released into the nucleus, and immediately
  establishes a condition of latency most as
  extra-chromosomal episomes.
• Infected cells initiate the cells cycle, begin to
  synthesize DNA (including viral DNA), and begin
  to divide rapidly by mitosis
• infected immortalized cells synthesize many EBV
  products
• EBNAs nuclear antigens(6)
• LMPs latent membrane proteins(2)
• EBER virus specific RNAs(2)

31
Epstein-Barr Virus - Pathogenesis

• Infectious mononucleosis
• B-cells are immortalized and continue to divide
• EBV is a B-cells mitogen which stimulates growth
  and prevent apoptosis
• B-cells become the site of latent infection
• EBV alters the way B-cells interact with the
  immune system
• increases the expression of B-cell surface
  proteins
• EBV infected B-cells express antigens which
  activate T-cells
• The classical lymphocytosis of this condition is
  the result of the proliferation of atypical
  lymphocytes Downey Cells
• lymphocytosis 10 -80 of white cells are
  atypical
• the increased T-cells cause swelling of lymph
  nodes, spleen, liver
• Mononucleosis results from the interaction of
  infected B-cells with activated T-cells
• Activated T-cells are essential for the
  resolution of the disease
• Immortalized B-cells synthesize heterophile
  antibody

32
Infectious Mononucleosis - Diagnosis

• symptoms
• Lymphcytosis 60 - 70 mononuclear cells with
  30 atypical lymphocytes earliest indicator
  of disease
• Virus detection
• Nucleic acid hydridization to detect EBV RNAs
• antigen detection on epithelial cells in throat
  washings
• serology
• heterophile antibody infected B-cells produce an
  IgM heterophile antibody which reacts with the
  Paul-Burnell antigen on sheep, horse, and bovine
  erythrocytes
• antibody is present by end of first week and is
  an excellent indicator of EBV infection in
  adults not reliable in children
• ELISA test used for detection
• other tests for antibody against viral capsid
  proteins and EBNA

33
Epstein-Barr Virus - Epidemiology

• Reservoir is Humans ( symptomatic or
  asymptomatic)
• Person-to-Person mode of transmission
  respiratory droplet
• EBV is transmitted in salvia
• more than 90 of infected individuals shed virus
  intermittently for life
• children often become infected at an early age by
  sharing drinking glasses
• Disease is generally subclinical in children
• disease in correctly called the kissing disease
  because of it increased incidence in adeloscents
  who exhange salvia.
• approx. 70 of the U.S. population is infected by
  age 30
• Transplant recipients who are immunocompromised
  have a high risk for immuno-proliferative disease