What are the FUNCTIONAL consequences of virus structure

[TastyCurrantJelly]

---

Members don't see this ad.

So with all the virus structure aspects to memorize - icosahedral/enveloped/positive or negative/single stranded vs. double stranded, there has to be some reason why these matter - I somehow have never learned this. Can anyone help break down what each of these differences means for the virus virulence and/or immune response?

 

[Phloston]

Enveloped ones tend to be parenterally contracted, and non-enveloped ones enterally. Viruses without envelopes survive harsh conditions (e.g., change in pH, dehydration), such as the enteroviruses. Polio, for instance, is non-enveloped and is contracted fecal-oral. HIV and HepB/C, for instance, are enveloped and are contracted parenterally. Even if you're the type with a poor memory, if you remember the rule, you could make the envelope vs non-envelope inference without knowing the specifics about every virus.

 

[dyspareunia]

Enveloped ones tend to be parenterally contracted, and non-enveloped ones enterally. Viruses without envelopes survive harsh conditions (e.g., change in pH, dehydration), such as the enteroviruses. Polio, for instance, is non-enveloped and is contracted fecal-oral. HIV and HepB/C, for instance, are enveloped and are contracted parenterally. Even if you're the type with a poor memory, if you remember the rule, you could make the envelope vs non-envelope inference without knowing the specifics about every virus.

If it's not already obvious, the reason enveloped viruses are more susceptible to the environment has to do with membrane lipids being easily degraded. Thus, enveloped viruses aren't going to be spread via fomites and are unlikely to be causing GI distress.

As far as positive/negative RNA goes, all the negative RNA viruses must carry their own RNA polymerase (not just encode it) because there is no eukaryotic RNA dependent RNA polymerase with which to transcribe +RNA (mRNA) from -RNA. This creates a target for antivirals.
RNA viruses are also much more likely to successfully mutate than DNA viruses because there is no proofreading by host RNA polymerase. Also every (-)RNA virus is enveloped.

Icosahedral vs helical has no effect on virulence and is really of no importance other than classification as far as I know.

dsRNA is highly immunogenic and is the main activator of IFN functions.

 

[CherryRedDracul]

dsRNA is highly immunogenic and is the main activator of IFN functions.

The only dsRNA viruses I'm aware of that are pathogenic to humans are the reoviruses (e.g. rotavirus). That makes it sound like interferons are pretty useless in a majority of cases.

But, FA errata made a correction which suggests that its blurb on interferons should be activated in response to viral nucleic acids in general rather that only in response to dsRNA, which makes more sense. Typically, RNA begets a stronger interferon response than DNA, and dsRNA are known to induce a very strong response, but the fact remains that all forms of nucleic acids trigger some sort of interferon response as long as those responses aren't inhibited.

This is on page 206 of FA 2014 if anyone wants to fix the error.

 

[notbobtrustme]

functionally, nothing really. It's just **** we have to memorize. In real life, no one cares that you know Bunyaviruses are negative sense RNA viruses.

 

[BlueArc]

Ether and other inorganic solvents can inactivate the "enveloped" non defective fully intact viruses, which results in a loss of viral activity, so loss of infectivity is a characteristic feature of enveloped viruses.
-non enveloped viruses are generally resistant to the action of ether..

 

[dyspareunia]

The only dsRNA viruses I'm aware of that are pathogenic to humans are the reoviruses (e.g. rotavirus). That makes it sound like interferons are pretty useless in a majority of cases.

But, FA errata made a correction which suggests that its blurb on interferons should be activated in response to viral nucleic acids in general rather that only in response to dsRNA, which makes more sense. Typically, RNA begets a stronger interferon response than DNA, and dsRNA are known to induce a very strong response, but the fact remains that all forms of nucleic acids trigger some sort of interferon response as long as those responses aren't inhibited.

This is on page 206 of FA 2014 if anyone wants to fix the error.

Every RNA virus produces dsDNA during its replication cycle. But yes, there are many more viral PAMPs.