2. The use of reassortant viruses can be used experimentally to determine which

Question

2. The use of reassortant viruses can be used experimentally to determine which gene segment (and its corresponding viral protein) is associated with a specific pathogenic phenotype. In the following example, reovirus T1L was mixed with reovirus T3D to determine the mode of spread to the central nervous system (CNS) after injection into the foot of mice. As shown in the table below, T3D spreads exclusively by a neural route (i.e., traveling nerve-to-nerve) while T1L spreads through the bloodstream before crossing the blood/brain barrier Origin of gene segment Virus Pattern of in vivo Spread Virus Isolate ParentTIL strain L L L L L L L L L Blood viremia R1 R2 R3 R4 L LLLD DLLD L Blood viremia D D D DLL L DD L Blood viremia D D D LDD L DDLBlood viremia Variants R6 R7 R8 R9 Neuronal (a) Based on the above data, which genome segment was found to be responsible for the pathway of virus spread within the mice? [3 pts.] (b) How do you think the protein encoded by the above indicated gene segment influences virus spread? Explain your reasoning. [4 pts.]

Explanation / Answer

As per the given data, we can see that there is proper mixing of L and D strain only by blood viremia. On the other hand the neuronal pathway shows that there is negligible mixing of the virus.

Either they are all L or D in case of neuronal. So the experiment gives us the idea about the p[athway of the virus spread is blood viremia.

B. The protein T3D determine the mode of spread through the CNS, while T1L spread by bloodstream. It is very clear that the L is more severely spreaded because of the carrier bloodstream that induces the flow as compared to the neurns. Bloodstream is the main pathway for any virus to spread easily.

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