Viral STIs Flashcards
What are the 3 most common viruses that cause STIs?
Molluscum contagiosum virus, Herpes simplex virus, human papilloma virus
What is the morphology of MCV and does it have a reservoir?
MCV is an eveloped DNA virus. It is only found in humans and has no animal reservoir.
What are the clinical manifestations of MCV and what is its epidemiology? (6)
Infection appears as flesh coloured, dome-shaped lesions on skin, affects skin and mucous membranes, MCV is not always an STI
Epidemiology: long incubation period (2-7 weeks), usually resolves on its own in 6-8 weeks, doesn’t remain in the body and therefore no long term immunity conferred
How is MCV treated?
Either by chemical or surgical removal of the lesions
What is the morphology and 2 main gene products of HSV ?
HSV is an enveloped, icosahedral capsid virus. Its genome encodes for thymidine kinase and DNA polymerase
What are the 2 types of HHV and the areas they infect most frequently?
HHV-1: ocular/oral infections
HHV-2: genital infections
What are the range of diseases that HHV can cause? (4)
Asymptomatic, lesions, meningitis, ocular infections
Describe the pathogenesis of HHV (think of latency and reactivation)
Upon primary infection by HHV, most people are asymptomatic and infected at a young age. The virus gets transported along sensory nerves to nerve cell bodies where they become latent and reside for life. Latent virus can reactivate where they multiply in the nerve cell and get transported along the axon to the nerve terminals in skin, causing cold sores or genital warts.
What are 2 important things to remember about genital herpes in terms of who is infected and the symptoms?
Most people dont know they are infected and many of the 1st symptoms they see are actually reactivation of the virus
How is HHV diagnosed and why is serology not a useful diagnostic tool?
HHV is diagnosed with RT-PCR
Serology is not useful because you can’t tell if it is HHV1 or HHV2 from it.
What is acyclovir, how does it work and how does it get activated?
Acyclovir is a nucleoside analog that is used as an antiviral by blocking viral DNA polymerase. In order to be activated it must be triphosphorylate, the first phosphorylation is done by viral thymidine kinase and the second two by host cell kinases.
How is the majority of resistance to acyclovir conferred by HHV?
95% of resistance is a result of mutations in viral thymidine kinase
What is morphology, epidemiology and diagnostic method for HPV? (4)
HPV is a non-enveloped, ds DNA virus and is the most prevalent STI. HPV cant be cultured and must therefore be detected by either molecular methods or a pap test/smear
What is high risk and low risk HPV and the 2 types associated with each class?
High risk HPV are types of the virus that carry the greatest risk of being oncogenic: HPV 16 and 18 cause 75% of cervical cancer
Low risk HPV are types of the virus aren’t normally associated with cancer but rather genital warts and self-limiting, low grade abnormalities: HPV 6 and 11
How does HPV infection manifest in most people?
For most people, HPV is a transient infection where nothing happens because the body’s immune system is able to clear the virus
