Intro to viruses

Viral genetic sequences

• carried as part of human genetic material

First virus discovered

• tobacco mosaic virus

First written record of virus

• in hieroglyphics

• Depicts temple priest showing signs of polio

Pharaoh Ramses

• pox marks found on mummy

• Suggests death by smallpox

Edward Jenner

• found milkmaid was infected with cowpox, then was immune to smallpox

• Used cowpox infected material to vaccinate a child

• Proved to work by deliberate attempt to infect with smallpox

• Smallpox was more dangerous than cowpox

Scientists who developed concepts of viruses

• Dmitri iwanowski

• Helmet ruska

• Martinus beijernick

Dmitri iwanowski

• Tobacco mosaic virus

• extracts from infected plants could infect other plants

• Filtered extract w chamberland filter , didn’t prevent transmission

• Postulated there was a v small infectious agent

Chamberland filter

• porcelain filter

• Removes bacteria from drinking water

Martinus beijerkick

• confirmed Dmitri findings

• New form of infectious agent discovered

• Demonstrated its only method of division was in living dividing cells

• Filtrate agent

Loeffler and Frosch

• repeated TMV experiments

• Demonstrated in foot and mouth disease in cattle was same principle

Carlos Finlay

• researched mosquitos carried cause of yellow fever

• First identified human virus

Discovering bacterial viruses

• Frederick twort - phage discovered due to clear lysis zones on plate of bacteria

• Isolated by felix d herelle - bacteriophage

Electron microscope

• developed 1933

• Quickly used to study phage and TMV

Virus elements

• genetic element

• Capsid

• Can’t replicate without living host cell

Virus properties

• small

• DNA or RNA

• Different replication strategy -not binary fission

• Obligate intracellular parasites

• Simple structure

Viral studies - health

• gain knowledge on disease

• Gene therapy (viral vectors)

• Vaccines

• Antiviral drug development

Antiviral drugs

• work to inhibit any stage of the viral replication in host

Mutations

• viruses can mutate

• Leads to increase in infection rates as immune response doesnt recognise it