Virus structure and the differences between antiviral drugs and vaccines

Derek Kinchington briefly discussed virus structure and the differences between antiviral drugs and vaccines. He reminded us that viruses were measured in nanometres (10-9 metres) and were tiny bags of a lipid and protein coat containing DNA or RNA encased in a protein core. Viruses have no existence outside of animal or plant cells. They just replicate within cells and infect other cells. Viruses have been around since the first primitive cells evolved about 2.5 billion years ago. The latest Mars rover, Perseverance, is searching dried up estuaries and deltas to see if the same primordial life forms existed on Mars as those on Earth, when similar environments existed on both planets.

Antiviral drugs are designed by crystallographers and medicinal chemists to target one very specific function of a virus. These range from blocking the entry of a virus into a cell, inhibiting the replication of its nucleic acid or to stop the virus from maturing. Highly active antiviral drugs will bring about a rapid reduction in viral replication within days.

Vaccines are blunt instruments and rely on using the innate immune systems of animals to overcome an infection. The design of some vaccines uses recombinant DNA technology to make a plasmid (AstraZeneca-Oxford) or a specific length of RNA (Pfizer-BioNTech) both of which express the sars-cov-2 spike protein. All vaccines select many millions of different combinations of B-cells expressing antibodies on their surface. These B-cells are already circulating in the blood, and when triggered produce a clonal expansion of the best-fit antibodies which usually take several weeks to neutralise the virus. In genetically stable viruses, vaccines will produce memory B-cells that remember the same viral proteins for faster antibody production in future infections. But for RNA viruses prone to mutate more rapidly it will be necessary to produce a modified vaccine each year. Such viruses are influenza and now sars-cov-2, the cause of Covid-19.  

Derek Kinchington PhD, FRCPath, Scientific Advisor to Intelligence Forums

Dr. Kinchington studied smallpox/human monkey pox genomes, DNA tumour viruses and spent about 15 years developing anti-HIV drugs. Derek is a Fellow of the Royal College of Pathologists