Understanding Nonenveloped DNA Viruses: Adenoviruses and HPVs

1. OPTO435 Microbiology II Gamal El-Hiti

2. Nonenveloped DNA Viruses Lecture Nine

3. Learning Outcomes OPT435 L09 – W11

4. Viral Infections OPT435 L09 – W11

5. Nonenveloped DNA Viruses OPT435 L09 – W11

6. Nonenveloped DNA Viruses  Adenoviruses are members of the family Adenoviridae.  They are medium sized viruses (80–90 nm).  Nonenveloped viruses have an icosahedral nucleocapsid containing a double stranded DNA genome.  Their name derives from their initial isolation from human adenoids in 1953. OPT435 L09 – W11

7. Nonenveloped DNA Viruses  A virus is an infectious agent that is minimally constructed of two components, genome and capsid.  A genome consisting of DNA.  A capsid which is a protein-containing structure designed to protect the genome.  Over 150 types of human papillomaviruses (HPVs)are now recognized, based on DNA sequences of well characterized virus genes.  HPVs exhibit great cell specificity, infecting surface of skin and mucous membranes. OPT435 L09 – W11

8. Nonenveloped DNA Viruses OPT435 L09 – W11

9. Nonenveloped DNA Viruses OPT435 L09 – W11

10. Nonenveloped DNA Viruses  Epidemiology of Human Adenovirus  Transmission of HPVs infection requires direct contact with infected individuals (e.g. sexual contact or contaminated surfaces).  HPVs can also be transmitted from mother to infant during passage down the birth canal.  Outbreaks have been more common in late winter, spring and early summer.  All ages are susceptible to adenovirus infection, but commonly during childhood. OPT435 L09 – W11

11. Nonenveloped DNA Viruses  Pathogenicity of Adenovirus  The HPVs multiplication and pathogenesis are very specific for the epithelial cells.  When an adenovirus enters its host, it will typically replicate in the epithelial cells that line the lungs or other enteric organs.  After several replication cycles, the virus will being to inhibit host macromolecular synthesis and transport of mRNA to the cytoplasm. OPT435 L09 – W11

12. Nonenveloped DNA Viruses  These cellular disturbances will kill host cells and can cause disease symptoms.  Studies have implied that the penton protein of adenoviruses is virulent  to their host.  The penton protein has caused the cells to detach from monolayers.  Even when the disease symptoms disappear, the virus can still remain latent in a person's body for years.  The viruses are found in lymphoid tissue. OPT435 L09 – W11

13. Nonenveloped DNA Viruses OPT435 L09 – W11

14. Nonenveloped DNA Viruses  Clinical Significance of Adenovirus  HPVs cause diseases that cover from simple warts to malignancies.  Warts can occur on any part of the body, including both cutaneous and mucosal surfaces.  Specific HPV types tend to be associated with specific wart morphology, although a wart morphological type is also related to its location. OPT435 L09 – W11

15. Nonenveloped DNA Viruses OPT435 L09 – W11

16. Nonenveloped DNA Viruses Acute adenovirus conjunctivitis is very contagious and transferred by contact. Common symptom includes swelling of the eyelid, either upper or lower.  Redness of the eye (pink eye).  Excess tears, itchy, burning and sensation of a foreign object in the eye.  Accompanied by a pus-like discharge, often causing eyelids to stick together after sleeping. OPT435 L09 – W11

17. Nonenveloped DNA Viruses OPT435 L09 – W11

18. Nonenveloped DNA Viruses  Treatment and Prevention of Adenovirus  There is no specific treatment for people with adenovirus infection.  Most adenovirus infections are mild and don’t require any medical care.  Cidofovir has been used to treat severe adenovirus infections in people with immunocompromised systems.  Currently, there is no adenovirus vaccine available for the general public. OPT435 L09 – W11

19. Nonenveloped DNA Viruses  Cidofovir (brand name Vistide) is an injectable antiviral used as a treatment for cytomegalovirus retinitis (an infection of the retina of the eye) in people with AIDS. OPT435 L09 – W11

20. Nonenveloped DNA Viruses Estimated HPV DNA prevalence in the world region (2007) OPT435 L09 – W11

21. Picornaviridae  Picornaviridae contain a single-stranded, non-segmented RNA genome.  Picornaviruses are small, naked (nonenveloped) and icosahedral viruses. OPT435 L09 – W11

22. Picornaviridae  They cause a broad spectrum of diseases but they share the following features:  They replicate in the cytoplasm.  Genomic RNAs serve as messenger RNAs and are infectious.  Genomic RNAs are nonsegmented.  Virions do not contain any enzymes.  Virus-specified proteins are synthesized as polyproteins that are processed by viral and cellular proteases, giving rise to individual viral proteins. OPT435 L09 – W11

23. Enteroviruses  Enteroviruses are a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases.  More than seventy enteroviruses have been identified.  Enteroviruses isolated more recently are named with a system of consecutive numbers as EV68, EV69, EV70 and EV71.  They affect millions of people worldwide, and often found in respiratory secretions. OPT435 L09 – W11

24. Enteroviruses  Epidemiology of Enteroviruses  Individuals are infected with Enteroviruses by ingestion of contaminated food or water.  Enteroviruses are stable at the low pH of the stomach, replicate in the gastrointestinal (GI) tract and are excreted in the stool.  They can replicate in a variety of tissues.  Most infections are asymptomatic.  Enteroviruses account for ca. 1015 million symptomatic infections per year in the US. OPT435 L09 – W11

25. Enteroviruses  Clinical Significance of Enterovirus Infections  All Enteroviruses can cause CNS disease.  Enteroviruses are currently the major cause of acute aseptic meningitis syndrome.  Viral meningitis disease is milder than bacterial meningitis.  Evidence of infection can also be obtained by demonstration of a rise in antibody titer against a specific enterovirus. OPT435 L09 – W11

26. Enteroviruses  Treatment of Enterovirus Infections  Viral meningitis occurs mainly in summer and fall, affecting both children and adults.  Enteroviruses infection is usually a benign self-limiting illness.  No antiviral drugs are available for the treatment of infections caused by Enterovirus species.  No vaccine is currently available for the prevention of enterovirus infections. OPT435 L09 – W11

27. Acute Hemorrhagic Conjunctivitis  Acute hemorrhagic conjunctivitis (AHC) is a derivative of the highly contagious conjunctivitis virus (pink eye).  Symptoms include excessively red, swollen eyes as well as subconjunctival hemorrhaging.  Currently, there is no known treatment.  Patients are required to merely endure the symptoms while the virus runs its five to seven day course. OPT435 L09 – W11

28. Acute Hemorrhagic Conjunctivitis  There are three main viruses that have been confirmed as the agents responsible for AHC, including Enterovirus 70, Coxsackievirus A24 variant (CA24v) and Adenovirus 11. OPT435 L09 – W11

29. Acute Hemorrhagic Conjunctivitis Enterovirus 70 and Coxsackievirus A24 are members of the genus Enterovirus and family of Picornaviridae.  They are non-enveloped having a single-stranded positive-sense RNA genome. Enterovirus 70 is very small. Coxsackievirus A24 is isolated from human.  Adenovirus 11 is a medium-sized variant that are nonenveloped.  These viruses are some of the largest nonenveloped viruses in existence. OPT435 L09 – W11

30. Enteroviruses OPT435 L09 – W11

31. Enteroviruses Weekly case numbers of acute hemorrhagic conjunctivitis reported by the disease surveillance network in Guangdong (China) between July and October of 2007 and 2010. OPT435 L09 – W11

32. Enteroviruses The incidence of acute hemorrhagic conjunctivitis cases in China.  OPT435 L09 – W11