Question

Describe why it can be challenging to develop an antiviral drug that lacks toxic side effects.

Explain how viruses with small genomes can encode for multiple proteins.

List the two methods viruses use to escape host cells.

Answer 1

Part A

It can be challenging to develop an antiviral drug that lacks toxic side effects because viruses use the host's cell machinery to replicate. So it is difficult to find novel targets for the drug that would interfere with the virus replication without causing any interference with cellular enzymes and DNA synthesis of the host cells.

Part B

Viruses with small genomes can encode for multiple proteins by

(i) employing overlapping reading frames or frameshifting, in which multiple proteins are encoded by the same nucleotide sequence.

(ii) generating smaller mRNA molecules from viral genomic RNA by alternative splicing.

(iii) synthesizing a single large polyprotein precursor and subsequently cleaving this into many smaller proteins by a series of limited proteolytic cleavages mediated by viral or cell proteases.

Part C

Viruses can escape host cells by

(i) Lysis - by bursting out of the infected cell (kills host cell)

(ii) Budding - by incorporating viral membrane glycoproteins in host cell membrane and forming a bud which is eventually pinched off by membrane scission to release the enveloped virus (may not kill a host cell)