DNA Viruses 1

• DNA - Single or Double stranded. Circular or Linear
• Replication of Nucleic Acid (DNA)

  • Early Transcription (ds DNA is needed, ss-> ds)
  • Early Translation (mrNA-> enzymes for viral DNA replication)
  • Late transcription (ds DNA used)
  • Late translation (mRNA-> proteins for capsid)
• Parvoviruses

  • Icosahedral
  • 18-26 nm diameter (smallest)
  • Single-stranded DNA
  • Non-enveloped
  • 2-5 proteins
  • Resistant to inactivation
• Parvovoirus Family: Parvoviridae

  Classified into two* subfamilies:

  • Densovirinae -contains viruses of invertebrates, requires helper viruses for productive infection
  • Parvovirinae - contain viruses of vertebrates
  • Erythroparvovirus
  • Bocaparvovirus
  • Protoparvovirus
  • Dependoparvovirus
• Human Parvovirus B19

  • First discovered in 1975
  • Predominant parvovirus pathogen in humans
  • Three genotypes
  • Only infects human
• Erythema Infectiosum

  • Also known as fifth’s disease 
  • Most common manifestation of B19
  • Most common in children
  • Incubation period of 1-2 weeks 
  • Mild Symptoms
  • Fever
  • Runny nose 
  • Headache
  • Rash
• Transient Aplastic Crisis

  • Characterized by an abrupt cessation of red blood cell synthesis
  • Lowers red blood cell production, causing a reduction in the hemoglobin level of peripheral blood
  • Usually occurs in people with sickle cell anemia, and thalassemia
  • Common symptoms include
  • Pale skin
  • Fatigue and Weakness
  • can complicate chronic hemolytic anemia
• Pure Red Blood Cell Aplasia

  • Occurs in immunocompromised individuals
  • Very few immature red blood cells in the blood vessels and erythroid progenitor cells
  • Similar symptoms to anemia
  • Usually chronic
• Pregnancy complications in Parvovirus

  • Hydrops fetalis
  • Accumulation of fluid in soft tissues
  • Miscarriage
  • Higher rate if infected on the first half of the pregnancy
• Transmission in Parvovirus:

  • Respiratory aerosol spread from acutely infected
  • Mother-to-child
  • Blood products (heat and solvent resistant)
  • Massive productive replication in erythroid progenitor cells
  • Very high viral load in acute infection prior to a detectable immune response
  • Occurs worldwide but restricted to humans
  • Seroprevalence increases with age
• Treatment for Transient aplastic crisis - Transfusion of blood products
• Treatment for fifth disease - Usually mild, Gets better on its own
• Tretament for Chronic infections - Immunocompromised individuals, Immune globulin intravenous therapy (IVIG)
• Treatment for Arthralgia & Arthritis -NSAIDs, Resolve on their own
• Treatment for Severe anemia in a fetus

  • Before 18 weeks
  • procedure is too difficult
  • 18-35 weeks
  • intrauterine blood transfusion
  • After 35 weeks
• Adenovirus

  • Icosahedral
  • 70-90nm
  • Double-stranded DNA
  • Non-enveloped
  • Many vertebrates are host
• Family: Adenovirdae 

  6 Genera:

  • Atadenovirus
  • Aviadenovirus
  • Ichtadenovirus
  • Siadenovirus
  • Testadenovirus
  • Mastadenovirus
  • Human Adenovirus
  • A-G
• • Adenovirus Clinical Manifestation in Respiratory diseases
  • Upper respiratory tract - infectious rhinitis (common cold), pharyngitis, tonsillitis
  • Lower respiratory system - pneumonia
• Adenovirus Clinical Manifestation in Eye infection

  • Conjunctiva - Conjunctivitis (pink eye)
  • Epidemic keratoconjunctivitis - preauricular lymphadenopathy
• Adenovirus Clinical Manifestation in Gastrointestinal diseases

  • Small intestine - gastroenteritis
• Adenovirus Clinical Manifestation in Genitourinary diseases

  • Urinary tract - Hemorrhagic cystitis
• Adenovirus Transmission:

  • Respiratory Droplets 
  • Fecal-Oral Route - “The 4Fs” Fluids, Fingers, Flies, and Fields
• Herpesvirus

  • Icosahedral
  • 150-200 nm
  • Double-stranded DNA
  • Enveloped
• Herpesvirus Family: Herpesviride

  Divided into 3 subfamilies

  • Alphaherpesvirinae
  • Simplex Virus
  • HSV 1 and 2
  • Varicellovirus
  • Varicella Zoster Virus
  • Betaherpesvirinae
  • Cytomegalovirus
  • Human Cytomegalovirus 
  • Roseolovirus
  • HHV 6 and 7
  • Gammaherpesvirinae
  • Lymphocryptovirus
  • EBV
  • Rhadinovirus
  • KSHV
• Herpes Simplex Virus

  • HSV-1 and HSV-2
  • HSV-1 is transmitted primarily through contact with infected oral secretions
  • HSV-2 is acquired primarily through contact with infected genital secretions
• Herpesvirus Primary Infection

  • HSV is transmitted by contact of a susceptible person with an individual excreting virus
  • The virus must encounter mucosal surfaces or broken skin for an infection to be initiated 
  • HSV-1 and HSV-2 also infect nearby sensory neurons, and travel up their axon to the neuron’s cell body to start up the latent cycle.
  • Majority of cases are mild
• Herpesvirus Latent Infection

  • Virus resides in latently infected ganglia in a nonreplicating state
  • Only a very few viral genes are expressed 
  • Viral persistence in latently ganglia lasts for the lifetime of the host.
• Herpes virus Skin Infections

  • Rare for healthy people
  • Usually seen in fingers 
  • Herpetic whitlow
  • Can be seen in the body, head, and extremities
  • Herpes gladiatorum
  • Could be serious for people with certain skin conditions
  • Burn injuries
  • Atopic dermatitis
• HSV Infection of other areas in rare cases

  • HSV can spread to the CNS
  • Causing meningitis or encephalitis
  • Typically in the temporal lobe
  • Commonly happens during reactivation as virus escapes into bloodstream
  • When there is brain involvement 
  • lumbar punctures give: 
  • Increased RBCs & WBCs
  • Elevated protein levels
  • CT, MRI & EEG Changes
• Herpesvirus Recurrence

  • Provocative stimuli can reactivate virus from the latent state
  • The virus transits via axons back to the peripheral site, and replication proceeds at the skin or mucous membranes
  • Many experience prodrome syndromes
• ORAL HERPES

  • Primarily asymptomatic
  • Symptoms usually appear in children
  • Incubation period of 2-12days, illness lasts 2-3 weeks
  • Primarily cause lesions in the mouth area
  • Herpetic gingivostomatitis
• GENITAL HERPES

  • Usually caused by HSV-2
  • Primary infection can be severe 
  • Generally lasts 3 weeks 
  • Characterized by painful lesions on the genitals 
  • Less severe for people with HSV-1 immunity
• HSV KERATOCONJUNCTIVITIS

  • Recurrent lesions of the eye are common and appear as dendritic keratitis or corneal ulcers or as vesicles on the eyelids
  • With recurrent keratitis, there may be progressive involvement of the corneal stroma, with permanent opacification and blindness
• NEONATAL HSV 

  • Transmissions happens at birth
  • Neonatal HSV may appear as:
  • Disseminated multiorgan disease (occuring in about 25% of neonates with infections)
  • Localized CNS disease (About 35%)
  • Localized infection of skin, eyes, mouth (about 40%)
• HERPES SIMPLEX VIRUS

  • can spread by asymptomatic shedding 
  • Can be in saliva and genital secretions
  • Most contagious when virus-filled lesions are present
• Herpes Simplex Virus Diagnosis

  • How skin or mucous membrane lesions look
  • Confirmation 
  • Look for viral DNA with PCR
  • Antibody response to virus
  • Growing virus in culture
• Herpex Simple Virus Treatment

  • Often resolves without treatment
  • Antiviral drugs such as: 
  • Acyclovir - reduce pain & speed healing
  • famciclovir - best if taken at start of prodrome
  • valacyclovir
• Varicella Zoster Virus

  Causes 2 diseases

  • Varicella (Chickenpox)
  • Primary infection
  • Herpes zoster (Shingles)
  • Reactivation of varicella
• VARICELLA

  Two stages:

  • Primary Viremia:
  • Spreads virus and leads to replication in the liver and spleen
  • Secondary Viremia
  • Infects T cells and travels to the skin
  • Infects keratinocytes
  • Incubation period of 10-21 days 
  • Initial symptoms include malaise and fever
  • Skin lesions then following the scalp, face, and body,
  • Macules
  • Papules
  • Vesicles
• SHINGLES

  • Infects sensory neurons
  • Travels to the dorsal root ganglia or trigeminal ganglion and establishes latency, allowing them to evade the immune system
  • The virus can be reactivated due to a weaker immune system
  • Travels back to the sensory nerve into the skin
  • It usually starts with sever pain in the area of skin or mucosa
  • Within a few days after onset, a crop of vesicles appears over the skin supplied by the affected nerves
  • The trunk, head, and neck are most commonly affected
  • Common complication is postherpetic neuralgia