Lecture 1 Flashcards
What is the historical significance of the small pox virus?
Smallpox: accredited with success of the Spanish conquistadors and the British Revolution against Native Americans.
-The British used contaminated blankets and presented them as gifts to local tribes – extremely high mortality resulted. This was possible due to the fact that smallpox virus has the ability to retain infectivity for long periods of time outside of the host
What is the historical significance of the yellow fever virus?
spread to South & North America during the slave trade period. There were huge outbreaks during 1776, especially in Philadelphia. This virus is transmitted by a mosquito biological vector and thus led to experimentation to determine route of transmission.
What is the historical significance of the poliovirus?
First killed vaccine- A team from Harvard headed by John Henders grew poliovirus in cell culture- they demonstrated that once you could propagate the virus, you would have lots of viral proteins that could be inactivated using a disinfectant and rendered incapable of infection. The inactivated proteins were mixed with an adjuvant (aluminum hydroxide) and used as a killed vaccine that induces the humoral immune response.
First modified live vaccine
Further research was conducted to produce a live vaccine that would induce both the humoral and CM immune response – the virus was attenuated by passing it through multiple abnormal hosts. The resulting cell cultures produced a vaccine that could induce immunity without inducing disease (proven in a study in Russia because these experiments were not supported in the US).
What is the historical significance of the Nipah Virus?
in late 90s there was an emergence in swine/human populations that led to widespread extermination of pigs to avoid spread and zoonosis. The natural host of this virus is the fruit bat, and outbreaks started when there were forest fires in Malaysia that disrupted the bat populations (bats shed the virus during periods of stress). They were forced out of their natural habitat and flew into areas that contained swine farms, leading to transmission to pigs (respiratory disease). Humans were most susceptible and would get disease of a respiratory/neurologic nature that was fatal
What is the historical significance of the 1918 Influenza outbreak?
1918: virus started to appear in both swine and human populations. The spread started in Kansas and was associated with Fort Riley, a military installation that gathered recruits for preparation to travel to Europe for WWI. The virus was dispersed throughout Europe, known as “Spanish Flu” – estimated 20-100 mil deaths.
What is the historical significance of Avian Influenza?
: H5N1 is a zoonotic avian influenza strain that has resulted in many fatal human cases (spread from poultry to humans). There has not been any demonstrated spread between humans, but if there is a genetic change in this strain in humans, there may be rapid transmission and high potential for a pandemic.
How viruses differ from bacteria, mycoplasmas, rickettsiae, and chlamydia with respect to physical & biological properties
Viruses are obligate intracellular parasites
generally less tnhan 300nm in size, have only DNA/RNA
generally do not have ribosomes, although one family has acquired non-fx ribosomes
virus do not perform metabolism
see chart in SG
What is the classical experiment Ivanosky and Bijernick demonstrated?
Ivanosky and Bijernick each used tobacco mosaic virus (TMV) to demonstrate that a “filterable agent” was an infectious replicating agent and not a toxin
What was the basic structure of the mosaic experiments?
took infected plant leaf, ground it up, serial 10x dilution
inoculated healthy oplants with dilution and noted infections,
higher diluitions- no disease transferred
ground up newly infected leaves, performed dilutions and observed same results
What was the key take home message of the mosaic experiments?
This demonstrated that the filterable agent was a replicating entity – if the material had been a toxin, then when they repeated the experiment with the dilute solution leaf they would have maybe observed infection after one or two dilutions, but definitely not as far down the dilution scale as they produced.
What is the classical experiment Avery and Griffith?
Used Streptococcus pneumonia to demonstrate that NA carry the code for virulence (virulent strains of this bacteria produce smooth colonies on BAP, avirulent strains produce rough colonies on BAP).
What was the structure of Avery and Griffiths experiment?
took virulent strain of bacteria, heat inactivated it, extracted components
treated live avirulent strains with the extracted material
streaked bacteria and saw both strains
THEN- repeated experiment but then this time destroyed the NA in the extract
upon streaking only the avirulent strain was present
What is the classical experiment of Hershey and Chase?
definitively demonstrated the NA contain the genetic code using phages and radio labeled isotopes
What was the structure of Hershey and Chase’s experiment?
labeled phages w/ isotopes (sulfer 35 for protein and phosphorus 32 for NA)
infected E. coli bacT w/ the phages
solution was agitated to detach the empty phage
viral genome allowed to replicate
resulting progeny phages only had the 32P was present, none had the 35S,
What was the take home message of the Hershey and Chase experiment?
Definitively proved that NA carried the genetic code.
