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Adenovirus, parvovirus, polyomavirus


Adenovirus


Case presentation A 68 year old African American male status post a heart and kidney transplant on immunosuppresive therapy presents with altered mental status, fever, diarrhea, productive cough was found on exam to have decreased breath sounds with bilateral harsh breath sounds, bilateral eye injection and redness. Lab work revealed leukocytosis of 14,000 on initial exam, cultures negative and CT chest revealing patchy consolidation right upper lobe, left lower lobe.


Adenovirus classification • Infect numerous vertebrate species (fish to human) • Only vertebrates (so far) • 51 human serotypes


Adenovirus structure, genome

From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 53-1.

• Icosahedral, non enveloped, 90 nM diameter • 36 kb (medium sized) linear dsDNA


Adenovirus Genome Late genes

E1

E2

E3

E4

• 36 kb (medium sized) linear dsDNA • Early genes for host and viral transcription control, viral DNA replication • Late genes for virion structure


Adenovirus replication • Replicates and assembles in nucleus via DNA intermediate • Uses host transcription apparatus, but modifies it to facilitate virus gene expression – Uses oncogenes (E1) in a fashion similar to papillomaviruses

• Transcription cascade (early and late genes) • Encodes virus specific DNA replication apparatus, including viral DNA polymerase


Adenovirus replication cycle

(From Fields Virology, 4th ed, Knipe & Howley, eds, Lippincott Williams & Wilkins, 2001, Fig. 67-5.)


Adenovirus pathogenesis • • •

Only one third of serotypes cause most clinical disease Widespread Respiratory or fecal-oral tramsmission – May establish viremia

• • • • • • • •

Replication in respiratory tract, eye, gastrointestinal tract, urinary bladder Persistence for months Responsible for 5% of acute respiratory disease (ARD) in children under 5 ARD in military recruits Conjunctivitis Hemorrhagic cystitis Gastroenteritis and diarrhea Some serotype specificity in pathogenesis


Adenovirus disease

(From Fields Virology, 5th ed, Knipe & Howley, eds, Lippincott Williams & Wilkins, 2007, Table 64.1.)


Adenovirus pathogenesis

From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005,, Fig. 50-4.


Adenovirus diagnosis • Cell culture • Viral antigen detection (ELISA, immunofluorescence)


Adenovirus vaccine • Live, wild type enteric coated vaccine for military recruits • Asymptomatic infection of gut raises protective immune response for respiratory infection


Summary: adenovirus • Structure

– Medium sized (36 kb) dsDNA genome, naked capsid

• Pathogenesis – – – –

respiratory or fecal oral transmission replication in nucleus; moderately host dependent local spread; viremia cellular and humoral immunity important; virus encodes countermeasures against MHC I expression and apoptosis – direct cell damage from replication; respiratory illness, conjunctivitis, gastroenteritis, cystitis

• Diagnosis

– culture, viral antigen detection

• Treatment/prevention – live military vaccine

• Gene therapy vector


Parvovirus


Case presentation The patient was a 19-year-old pregnant female who presented at 22 weeks gestation with signs and symptoms of preeclampsia. An ultrasonogram revealed intrauterine fetal demise. Hydrops (abnormal accumulation of fluid in tissues) was present. Labor was induced, and a stillborn fetus was delivered. An autopsy was performed on the fetus. Severe autolysis was evident, which is consistent with intrauterine demise. On histopathologic examination of the fetus, characteristic intranuclear viral inclusions were seen in erythroid precursor cells in the bone marrow and liver. Serologic evidence of acute infection due to maternal exposure to parvovirus B19 supported the diagnosis in this case.


Classification • Parvoviruses affect many animal species – Vertebrates and invertebrates

• Limited but noteworthy interspecies transmission • Human, cat, dog and pig parvoviruses economically and socially important • Two human viruses – B19 – Adeno associated virus (AAV)


Parvovirus structure

• • •

Icosahedral, non enveloped, 18-26 nM diameter (reeeeally small) 5 kb, linear, single stranded DNA genome (reeeeally small) Depending on virus, only one of both DNA strands may be encapsidated, but if both, they are encapsidated separately.


Canine parvovirus


Parvovirus Genome

ITR Rep

Cap

• 5 kb, linear, single stranded DNA • Inverted terminal repeats essential for replication and integration (dependoviruses) • Two genes – Rep is required for DNA replication – Cap encodes capsid proteins

ITR


Parvovirus replication • Replicates and assembles in nucleus via DNA intermediate • Uses host transcription apparatus • Encodes control protein (Rep) for DNA and RNA synthesis • Two replication styles – Autonomous – Helper dependent


Autonomous parvovirus replication

• •

Includes the human pathogen B19 Must replicate in mitotically active cells (S-phase) – Preference for erythroid lineage

Postulated replication of parvovirus (B19) based on information from related viruses (minute virus of mice). The internalized parvovirus delivers its genome to the nucleus, where the single-stranded (plus or minus) DNA is converted to double-stranded DNA by host factors and DNA polymerases present only in growing cells. Transcription, replication, and assembly occur in the nucleus. Virus is released by cell lysis.(From Medical Microbiology, 5th ed., Murray, Rosenthal, Kobayashi & Pfaller, Mosby Inc., 2002, Fig. 56-2.)


Helper dependent parvovirus (AAV) replication

• Includes human non-pathogenic adeno associated virus (AAV) • Absolutely dependent on adenovirus as helper – Several adenovirus genes are involved in helper function • Efficient, site specific integration during replication • Integration not required for replication • Integrated provirus may be activated to replicate by infection with helper


Parvovirus pathogenesis • Human parvovirus B19 – Widespread (50 - 90% of population depending on age), mostly asymptomatic infections – Respiratory transmission – Viremia – Infects erythroid precursor cells in bone marrow – Disease • • • •

Erythema infectiosum (fifth disease) in children Acute polyarthritis in adults Transient aplastic crisis in anemic individuals Hydrops fetalis in seronegative pregnant women – Results from anemia in fetus

• Adeno associated virus (AAV) – No known human disease


Erythema infectiosum (fifth disease)

• • •

Facial erythema (“slapped cheek”) Lacy, reticular evanescent maculopapular eruption on trunk and extremities Rash represents immune response


Parvovirus pathogenesis

From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 56-3.


Parvovirus diagnosis • Serology • Viral nucleic acid


Parvovirus • Structure

– Small (5 kb) linear ssDNA genome, naked capsid

• Pathogenesis

– respiratory transmission – replication in nucleus, very host dependent, needs S phase cells or helper virus – viremia – antibody important in immunity – targets erythroid lineage cells; fifth disease (symptoms immunological); transient aplastic crisis; hydrops fetalis

• Diagnosis

– serology, viral nucleic acid

• Treatment/prevention – None

• Gene therapy vector


Polyomavirus


Case presentation 21 year old white female status post B cell acute lymphocytic leukemia. Treated with bone marrow transplant. Developed graft vs host disease, HSV I, cystitis, hematuria and passage of blood clots. Continuous bladder irrigation, cystoscopy, clot evacuation, bilateral urethral catheter placement/occluding nephrostomy tubes to hopefully prevent cystectomy.


Polyomavirus classification • Infect a variety of vertebrates, birds to humans


Polyoma virus structure

• Icosahedral, non enveloped capsid, 40-45 nM diameter • 36 kb (medium sized) linear dsDNA


Polyomavirus genome

• •

Early genes for host and viral transcription control, viral DNA replication Late genes for virion structure

Genome of the SV40 virus. The genome is a prototype of other polyomaviruses and contains early, late, and noncoding regions. The noncoding region contains the start sequence for the early and late genes and for DNA replication (ori). The individual early and late messenger RNAs are processed from the larger nested transcripts.(From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 52-7.)


Polyomavirus replication • Replicates and assembles in nucleus via DNA intermediate • Uses host transcription apparatus • Transcription cascade (early and late genes) • Encodes a single virus specific DNA replication initiation protein, T antigen. – T antigen is also an oncoprotein; stimulates cellular DNA replication; strategy analagous to papillomaviruses.


Polyomavirus replication

Replication cycle of polyomaviruses. Steps in the replication cycle are indicated by numbers as follows: 1, adsorption of virions to the cell surface; 2, entry by endocytosis; 3, transport to the cell nucleus (route and mechanism not yet known); 4, uncoating; 5, transcription to produce early region mRNAs; 6, translation to produce early proteins (T antigens); 7, viral DNA replication; 8, transcription to produce late region mRNAs; 9, translation to produce late proteins (capsid proteins); 10, assembly of progeny virions in the nucleus; 11, entry of virions into cytoplasmic vesicles (mechanism unknown); 12, release of virions from the cell by fusion of membrane vesicles with the plasma membrane; 13, released virion. (From Fields Virology, 4th ed, Knipe & Howley, eds, Lippincott Williams & Wilkins, 2001, Fig. 63-4.)


Polyomavirus pathogenesis • • • •

Two widespread human polyomaviruses, JC and BK Respiratory infection, usually asymptomatic Persistent infection in kidneys Clinical disease results from immunosuppression (persistence is important!) – AIDS gives rise to JC induced progressive multifocal leukoencephalopathy (PML) •

Lytic infection of myelin producing oligodendrocytes; apparent lesions by MRI or CT; neurologic symptoms (muscle weakness, cognitive abnormalities, sensory & visual deficits)

– Bone marrow transplant gives rise to hemorrhagic cystitis (BK virus)

Recent association (80%) of polyomavirus with Merkel cell carcinoma, a neuroendocrine carcinoma of the skin – Virus genome usually present integrated into host genome – T antigen expression


Polyomavirus pathogenesis

From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig.52-8.


Polyomavirus • Structure – Small (5 kb) circular dsDNA genome, naked capsid

• Pathogenesis – – – – –

respiratory transmission replication in nucleus; very host dependent viremia persistence in kidneys; reactivation with immune compromise inapparent infection; hemorrhagic cystitis; PML

• Diagnosis – viral nucleic acid

• Treatment/prevention – cidofovir ?


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