DNA Viruses Flashcards
What type of genome is found in Herpesviruses?
Double-stranded DNA, enveloped, icosadeltahedral capsid
Where does Herpesvirus replication and assembly occur?
In the nucleus, with DNA polymerase encoded by the virus
What type of infection can Herpesviruses establish aside from lytic infections?
Latent infections, often in neurons
What diseases are commonly caused by Herpes Simplex Virus (HSV)?
Oral and genital herpes, encephalitis, and keratitis
How is Herpes Simplex Virus (HSV) primarily transmitted?
Through direct contact with infected secretions
Which immune evasion strategy is used by HSV to avoid antibody detection?
Cell-to-cell spread and formation of syncytia
What diagnostic methods are used for Herpesvirus infections?
PCR, serology, and Tzanck smear for multinucleated giant cells
What is the main treatment for HSV infections?
Antiviral drugs like acyclovir, targeting viral DNA polymerase
Describe the Poxvirus genome and structure.
Large, complex, double-stranded DNA with a brick-shaped envelope
Where does Poxvirus replicate in the host cell?
In the cytoplasm, using its own transcription machinery
What are the major diseases caused by Poxviruses?
Smallpox and Molluscum contagiosum
How is Poxvirus typically transmitted?
Smallpox via respiratory droplets, others by direct contact
What immune evasion mechanisms are encoded by Poxviruses?
Multiple immune-modulating proteins such as virokines and virostealth proteins
How is Poxvirus infection diagnosed?
Clinical signs (pustular rash), PCR, and electron microscopy
What prevention method led to the eradication of smallpox?
Vaccination using a live vaccinia virus
What is the genome structure of Adenoviruses?
Linear double-stranded DNA with terminal proteins, non-enveloped
Describe the replication location and process of Adenoviruses.
Replicates in the nucleus with its own DNA polymerase; switches from early to late gene expression
What common diseases are associated with Adenovirus?
Respiratory infections, conjunctivitis, and gastroenteritis
How is Adenovirus primarily transmitted?
Through respiratory droplets, fecal matter, and fomites
How does Adenovirus evade the immune system?
By producing proteins that inhibit MHC class I antigen presentation
What are common diagnostic methods for Adenovirus?
PCR, antigen detection, and cell culture
Are there vaccines for Adenovirus?
Yes, live oral vaccines for military personnel against types 4 and 7
What is the structure of Papillomavirus?
Small, non-enveloped with circular double-stranded DNA in an icosahedral capsid
How does Papillomavirus replicate in host cells?
Replicates in the nucleus, often utilizing host cell machinery to initiate DNA synthesis
What are common diseases caused by Papillomavirus?
Warts, cervical cancer, and other epithelial cancers
How is Papillomavirus typically transmitted?
Through direct contact, sexual contact, and from mother to newborn during delivery
What immune evasion tactic is used by Papillomavirus?
Persistence in basal cells, avoiding immune detection
How is HPV infection diagnosed?
Pap smear, PCR, and visualization of koilocytosis
What vaccines are available for HPV?
Gardasil (covers types 6, 11, 16, 18) and Gardasil 9 (covers nine HPV types)
How does HPV contribute to cancer development?
Integration of viral DNA disrupts regulatory genes, leading to uncontrolled cell growth
Which Herpesviruses are known to cause latent infections in neurons?
HSV-1, HSV-2, and Varicella-Zoster Virus (VZV)
What mechanism allows HSV to maintain latency in neurons?
Suppression of viral gene expression, remaining dormant in the neuron until reactivation
How does Epstein-Barr Virus (EBV) alter host cells during latency?
It immortalizes B cells, potentially leading to cancers like Burkitt’s lymphoma
What unique feature allows Poxvirus to replicate in the cytoplasm?
It carries its own DNA and RNA polymerase, bypassing the need for nuclear replication
Which Poxvirus protein assists in immune evasion?
Virokines, which mimic host cytokines to modulate immune responses
What is the primary cause of Molluscum contagiosum?
Infection with a specific type of Poxvirus that affects skin
How does Adenovirus affect host cellular machinery during infection?
It induces host DNA replication machinery and inhibits apoptosis to prolong cell life
What part of the respiratory system does Adenovirus typically infect?
It primarily infects the respiratory epithelium, causing symptoms like pharyngitis
What seasonal trend is often seen with Adenovirus infections?
Higher transmission rates in late winter and spring
How does the E6 protein of high-risk HPV strains contribute to carcinogenesis?
It binds to p53, inhibiting its tumor-suppressor functions
What is the effect of the HPV E7 protein in infected cells?
It binds to retinoblastoma protein (pRB), disrupting cell cycle regulation
What immune response is essential for controlling Herpesvirus infections?
Cell-mediated immunity, particularly T cells
What is the primary site of latency for Varicella-Zoster Virus (VZV)?
Sensory ganglia, where it can reactivate as shingles
How does Cytomegalovirus (CMV) evade the immune system during latency?
By reducing MHC class I expression on infected cells
Which diagnostic method is particularly useful for detecting CMV in immunocompromised patients?
Quantitative PCR to measure viral load
What feature makes Poxviruses resistant to adverse environmental conditions?
Their complex, protein-rich envelope
Which part of the immune system does the Adenovirus E3 protein inhibit?
Tumor necrosis factor (TNF)-mediated apoptosis, aiding in immune evasion
Which high-risk group is particularly susceptible to severe CMV infections?
Immunocompromised individuals, such as organ transplant recipients
What vaccination strategy is recommended to prevent HPV-related cancers?
Vaccination with Gardasil or Gardasil 9 before sexual activity
How can EBV infection be diagnosed in the lab?
Detection of heterophile antibodies (Monospot test) or EBV-specific antibodies
What antiviral is often used for the treatment of Poxvirus infections in special cases?
Cidofovir, an inhibitor of viral DNA polymerase
What is the role of the HSV glycoprotein gB in infection?
It facilitates viral entry by binding to host cell receptors
How do Papillomaviruses persist in the host without immune detection?
By maintaining low-level expression of viral proteins in basal epithelial cells
How does the Adenovirus genome facilitate immune evasion?
By encoding E1A and E1B proteins to block interferon response and apoptosis
What structural feature distinguishes Adenovirus from enveloped DNA viruses?
Its icosahedral, non-enveloped capsid, which makes it environmentally stable
