FA 2019 pg.168 on neg sense RNA virus: must transcribe - strand to +.Virion brings its own RNA-dependent RNA polymerase.
the gotdamn trick here is HIV is single standed + sense "diploid". NBME writers are just fuckers. ughhhh
Ok, so RNA dependent DNA polymerase is for reverse transcriptase... single stranded + use RNA dependent RNA polymerase. Can someone explain?
my problem with this, why can't it be similar to Hep B (circular DNA)? virus is new or hypothetical.
RNA dependent DNA polymerase= Reverse transcriptase. 2 viruses have reverse transcriptase- retroviruses and HBV. HBV DOESNT cause encephalitis and it is partially double stranded. And HIV is ss positive sense And you have that option given. Hence D.
When you hear reverse transcriptase (RNA dependent DNA polymerase) you should immediately be thinking HIV or Hep. B. In this case, Hep B. isn't amongst the answer choices, it is a partially double stranded circular DNA virus, not a fully double stranded DNA virus.
This leaves HIV, single stranded positive sense RNA virus. Another clue is that this is causing encephalitis, which immediately clued me into HIV associated encephalitis with microglial proliferation. HIV has tropism in the CNS for macrophages (microglia). Hep B. infects hepatocytes, and I'm unaware that it can spread to the CNS at all.
I think this was referring to reverse transcriptase, and the only two viruses I knew that used them were HepB and HIV/retroviruses. Given the context I picked HIV/retroviruses which are SS + sense. This was kind of weird though since the virus was โnewโ ... but Iโve learned that โnewโ usually means very little on these tests.
My guess is that they are referring to Retrovirus (HIV/HTLV)- a single stranded positive sense linear RNA. Retroviruses are known to carry reverse transcriptase (RNA-dependent DNA-polymerase). The encephalitis is what threw me off cuz I automatically thought of the many negative sense RNA viruses that cause encephalitis (like arenavirus or bunyavirus). Apparently there have been a few causes of HTLV causing encephalitis... maybe this is what they were trying to get at? Idk but i just spent way too much time on this damn question https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5878187/
RNA depended DNA polymerase = reverse transcriptase (FA 20 p 38, under telomerase).
Given the virus has reverse transcriptase, it is likely a retrovirus (hepadnavirus also has reverse transcriptase).
Retroviruses are SS+ RNA viruses (FA 20 p 167)
Japanese encephalitis virus according to Dr. Google (ncbi)
As soon as I saw encephalitis I thought of Flaviviruses which are:
SS โ linear Icosahedral including:
HCV,Yellow fever, Dengue, St. Louis encephalitis, West Nile virus aka meningoencephalitis and Zika virus
p. 167 First Aid 2018
submitted by โhaliburton(224)
according to medbullets link ns ss RNA must carry RNA dependent RNA polymerase (so that is out).
also, according to medbullets there are very few ds RNA viruses, so "most likely" will be ss. Also, RNA-dependent DNA polymerase = Reverse Transcriptase. Since HIV is a ss ps RNA virus with RT, they've described an HIV cousin. not sure beyond this.