BIOL 416 EXAM 3

Describe three factors that contributed to the high pathogenicity of the 1918 pandemic influenza virus.

-Binding of HA/NA to both α2-6 sialic acid in upper respiratory tract and α2-3 sialic acid in lower respiratory tract. -Hemagglutinin cleavage by proteases other than tryptase Clara (viruses able to cause systemic infections). -PB1 and NS1 added to strain virulence. -Severe immune pathology (cytokine storm) -New strain so no pre-existing immunity

What are potential targets for antivirals?

-Prevention of entry into host cells -Inhibition of virus uncoating -Integrase inhibitors -Duplication of viral genome (RNA or DNA) -mRNA transcription and processing -Protein translation -Post translational modification of proteins -Assembly of molecular components into the whole virus, maturation so the successful targeted stages = Inhibitions of virus entering, Duplication of viral genome (RNA or DNA), mRNA transcription and processing, Post-translational modification of proteins

2 reasons why we have so few antiviral drugs

2 reasons why we have so few antiviral drugs 1. Compounds interfering with virus growth can adversely affect the host cell o Side effects are common o Every step in viral life cycle engages host functions 2. Many medically important circuses are dangerous, cant be tested in model systems, or can't be propagated o Difficult or impossible to grow in the laboratory: E.g. hepatitis B and C, papilloma virus o Have no available animal model of human disease E.g. smallpox virus, HIV, measles virus o We kill investigators who aren't careful E.g. Ebola virus, lass fever virus, smallpox virus

How are RNA vaccines produced? What are some examples?

An RNA is injected in the body. This RNA encodes the information to produce the antigen, which is a protein from a pathogen, that will stimulate the immune system. Inside the cells, the RNA is used to synthesize the antigen, which is exposed to the cell surface. Then, a subset of immune system cells recognizes the antigen and trigger an immune response (direct response and long-term memory). Examples: Ebola Zika Rabies

2 reasons why many acute infections are of short duration

Another serious problem for antiviral drug hunters: Many acute infections are of short duration 1. By the time the patient feels ill, the virus is no longer replicating in the protein o The symptoms are due to the immune response o The antiviral drug is of no use • Antiviral drugs for these viruses must be given early in infection to prophylactically to populations at risk o Safety issues; giving drugs to healthy people is not wise 2. No broad-spectrum antiviral agents are currently available, so every virus infection has to be identified specifically

What is the difference between antigen shift and antigenic drift in terms of mechanism?

Both antigenic drift and antigenic shift are terms used to describe ways in which the flu virus changes over time. A drift is a minor change while a shift is a major one. antigen shift: Occurs via reassortment of gene segments ---Therefore requires coinfection Antigenic shift occurs when the influenza A virus acquires a new H or N gene. abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans. Such a "shift" occurred in the spring of 2009, when an H1N1 virus with a new combination of genes emerged to infect people and quickly spread, causing a pandemic. When shift happens, most people have little or no protection against the new virus antigenic drift: Mutations are common during viral replication. Viral RNA dependent RNA polymerase lacks proofreading and correction ability. Antigenic drift is the gradual accumulation of new epitopes on the H protein (and, to a lesser degree, the N protein). small changes in the genes of influenza viruses that happen continually over time as the virus replicates. These small genetic changes usually produce viruses that are pretty closely related to one another. Viruses that are closely related to each other usually share the same antigenic properties and an immune system exposed to an similar virus will usually recognize it and respond. (This is sometimes called cross-protection.)

Potential Viral Bioterrorism Agents: Category A Category B Category C

Category A: Smallpox; viral hemorrhagic fevers (filoviruses [e.g., Ebola, Marburg] and arenaviruses [e.g., Lassa, Machupo]) - can be easily disseminated or transmitted from person to person - result in high mortality rates and have the potential for major public health impact; - might cause public panic and social disruption; and - require special action for public health preparedness. Category B: Noroviruses - are moderately easy to disseminate; - result in high morbidity rates and low mortality rates; and - require enhancements of CDC's diagnostic capacity and enhanced disease surveillance. Category C: Emerging hemorrhagic and encephalitic viruses such as Hantavirus and Nipah virus - availability; - ease of production and dissemination; and - potential for high morbidity and mortality rates and major health impact.

What approaches are public health entities worldwide taking to deal with the challenge of future influenza pandemics?

Challenges in Dealing with a Pandemic Practical: - production of sufficient vaccine or antivirals - Insufficient hospital resources for care of infected individuals • Political: - dissemination of healthcare in difficult/hostile situations - Lack of political will to institute preventive measures • Biological: - Antigenic shift of virus makes vaccine development difficult • Economic: - Projected dire impacts on global economy ($US675B) • Social: - Estimated 200,000,000 US infections, 2,000,000 dead Approaches: -Improving Planning Process -Increasing Availability of Antiviral Agents and Vaccines -Providing Better Medical Care -Developing Feasible Mitigation Strategies -Strengthening Core Capacities -Strengthening International Collaboration

Name the Representative member and Polarity of genome for each RNA virus family: Coronaviridae Orthomyxoviridae Picornaviridae Flaviviridae Filoviridae

Coronaviridae Representative member: SARS Polarity of genome: + Orthomyxoviridae Representative member: Influenza Polarity of genome: - Picornaviridae Representative member: Polio Polarity of genome: + Flaviviridae Representative member: Dengue Polarity of genome: + Filoviridae Representative member: Ebola Polarity of genome: -

What was the source of the original smallpox vaccine?

Cowpox was inadvertently replaced with an unrelated poxvirus, vaccinia. • The origin of vaccinia is completely unknown. • Smallpox eradicated using administration of vaccinia. • The last known natural infection in 1979.

How are DNA Vaccines produced? What are some examples?

DNA vaccination is a technique for protecting against disease by injection with genetically engineered DNA so cells directly produce an antigen, producing a protective immunological response. The direct injection of genetic material into a living host causes a small amount of its cells to produce the introduced gene products. This inappropriate gene expression within the host has important immunological consequences, resulting in the specific immune activation of the host against the gene delivered antigen. The DNA is injected into the cells of the body where the host cell then interprets the DNA and uses it to synthesize the pathogen's proteins. An immune response is then triggered when the pathogen's proteins are recognized as foreign to the immune system. ---Naked plasmid DNA expressing viral gene ---Can co-express immune stimulatory molecules ---Plasmid DNA is itself a TLR ligand! No approved human DNA virus. Several DNA vaccines are available for veterinary use.

Explain the two diseases associated with dengue infection. What determines which disease is manifested in a given patient?

Dengue Hemorrhagic Fever (DHF) or Dengue Shock Syndrome (DSS)

Define: Emerging Disease Re-emerging Disease Endemic Epidemic Pandemic Epidemiology

Emerging disease: new to humans Re-emerging disease: reappearing and causing increased incidence of disease Endemic: diseases that persist at a moderate and steady level within a geographic area Epidemic: unusually high number of cases in excess of the norm of a similar illness in a population, community or region Pandemic: a world wide epidemic ---Spanish Flu ---H5N1 Epidemiology: the study of how diseases affect whole communities and how outbreaks are linked

Factors Leading to Emergence of "New" Virulent Viruses/Diseases

Factors That Affect Stable Virus-Host Interactions and Promote Emergence of New Diseases • Population growth • Travel/Migration • Pasture, hunting, and fishing practices • Agriculture/Deforestation/Dam Construction • Global Commerce • Human social behavior (sex, IV drugs, etc) • Climate variability Factors Leading to Emergence of "New" Virulent Viruses • Viral mutation/recombination resulting in new virulence or resistance to preventive measures • Alterations in viral vector species behavior • Environmental changes altering virus-host interactions • Social/behavioral changes of host • Health care interventions • Food production and distribution • New detection methods

We described how the 1918 Pandemic Flu was resurrected and produced infectious influenza virus. Using the same principles used for that virus, describe a strategy for generating infectious hantavirus from the known genomic sequence. Be aware that the genome has 3 genomic segments and requires two proteins for RNA synthesis (N and L proteins). Explain the basis for your strategy.

First perform RT-PCR of the RNA genome segments to generate cDNA for each segment. Next clone the 3 cDNA segments into 3 plasmids. Also clone N and L polymerase genes into 2 helper plasmids that are driven by promoter to express them. Transfect the 5 plasmids into cells, then harvest the live hantavirus.

What type of selection occurs when a virus is initially passaged in cell culture? What selection occurs after continual passage in cell culture?

Initially, directional selection, as the virus will acquire mutations that promote its replication in cell culture. After continual passage in cell culture the virus will experience stabilizing selection where its genome stays relatively the same.

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How are live vaccines produced? What are the advantages/disadvantages to a live virus vaccine?

Live attenuated vaccines are made by weakening the natural virus or bacteria (uncommon). Example: Rotavirus Vaccine, Shingles Vaccine, Vaccinia (Smallpox) Vaccine Advantages: -Live attenuated vaccines are great at teaching the immune system how to fight off a particular virus because they are the closest to a natural infection. -They only require one to two doses for life-long immunity. (Fewer boosters!) -These vaccines are relatively easy to create for certain viruses. Disadvantages: -It is possible that weakened viruses have the ability to gain control of their natural environment again and cause disease. -These vaccines can not be administered to people with weakened immune systems due to cancer, HIV, or other immune system depressing disease. -Live, attenuated vaccines usually must be refrigerated and protected from light. -It may be hard to ship these vaccines overseas and used in places that lack refrigeration. -This technique doesn't work as well with bacteria, therefore there are very few live bacterial vaccines. Viruses are very simple and contain very few genes in relation to bacteria, which have thousands of genes. This makes bacteria much harder to control and manipulate than viruses. Currently, scientists are hard at work trying to remove key genes from certain bacteria, in order to create weakened versions to be used in vaccines • Low level replication - Duration of Ag presentation is short • Consequence? • Tropism may be altered - Adaptive response may depend on tropism - Response to secondary natural infection may not be protective; disease may be more severe (Rotashield vaccine failure) • Reversion to virulence • Spread to unvaccinated, at-risk individuals • Cannot be administered to immune compromised patients

Describe the process of membrane fusion.

Membrane fusion, one of the most fundamental processes in life, occurs when two separate lipid membranes merge into a single continuous bilayer. Fusion reactions share common features, but are catalyzed by diverse proteins. These proteins mediate the initial recognition of the membranes that are destined for fusion and pull the membranes close together to destabilize the lipid/water interface and to initiate mixing of the lipids. A single fusion protein may do everything or assemblies of protein complexes may be required for intracellular fusion reactions to guarantee rigorous regulation in space and time. Cellular fusion machines are adapted to fit the needs of different reactions but operate by similar principles in order to achieve merging of the bilayers.

What two cellular proteases are involved in dengue virion processing and where are they active?

NS2b/NS3 Protease

***SARS-CoV Outbreak 2003

Natural reservoir is a bat • Thought to have spread to humans through a civet cat • Was spread world wide via airline travel of infected individuals (Super Spreaders)

Unlike many RNA viruses, influenza replication occurs in the nucleus, why is this necessary?

Orthomyxoviridae viruses are one of two RNA viruses that replicate in the nucleus (the other being retroviridae). This is because the machinery of orthomyxo viruses cannot make their own mRNAs. They use cellular RNAs as primers for initiating the viral mRNA synthesis in a process known as cap snatching.[52] Once in the nucleus, the RNA Polymerase Protein PB2 finds a cellular pre-mRNA and binds to its 5' capped end. Then RNA Polymerase PA cleaves off the cellular mRNA near the 5' end and uses this capped fragment as a primer for transcribing the rest of the viral RNA genome in viral mRNA.[53] This is due to the need of mRNA to have a 5' cap in order to be recognized by the cell's ribosome for translation.

PRACTICE EXAM

PRACTICE EXAM

- Discuss current views of the epidemiology of avian influenza spread from wild birds to poultry to humans, highlighting adaptation that must occur for efficient human infection

Pandemics: the Avian Influenza Threat Pandemics require: - Novel virus (no preexisting immunity) - Severe disease - Ability to spread human-to-human

List three pathogens that have been linked to Guillain-Barré syndrome. How is the disease believed to occur?

Pathogens: Zika virus C. jejuni influenza virus cytomegalovirus EBV Hepatitis A,B,C,E, HIV mycoplasma pneumonia Immune cells produce antibodies against the pathogen that are self-reactive and bind to gangliosides in nerve cells. This leads to destruction of myelin sheath and nervous system damage, including symptoms such as tingling in extremities.

How are Reassortant Vaccines produced? What are some examples?

Reassortant vaccines: A vaccine made by combining antigens from several viruses or from several strains of the same virus. Mixtures of gene segments from: ---human and animal viruses ---virulent and attenuated viruses Only applicable for segmented genome viruses Examples: Rotavirus Vaccine Influenza Vaccine

How are Recombinant Vaccines produced? What is an example of this type of vaccine?

Recombinant Vaccines: Insertion of a human virus gene into an attenuated, live virus vector. This involves inserting the DNA encoding an antigen that stimulates an immune response into bacterial or mammalian cells. An antigen against the virus gene is produced in the cells (vector) and then purified and used to make the vaccine. This results in a safe inactivated vaccine that can stimulate immunity, but cannot cause disease - vaccinia-based - adenovirus-based - RNA virus based Example: Whooping Cough Vaccine Shingles Vaccine Hep B Vaccine HPV vaccine

Why is drug resistance such a problem and what are strategies to reduce this problem?

Resistance to any antiviral drug must be anticipated when one applies compounds that inhibit viral growth o Viruses replicates so efficiently o Have modest to high mutation frequencies RNA viruses o The masters of error-prone replication RNA polymerases are unable to correct errors Host repair systems do not work on RNA DNA viruses o Replication of DNA virus genomes is not as error-prone as replication of RNA virus genomes o Most DNA polymerases can excise and replace mis-incorporated nucleotides o Most DNA viruses tend to evolve slower than RNA viruses because they do not generate as much diversity

You are treating a patient who has a mild fever, and determine they are infected with dengue virus serotype 1. How would you evaluate the likelihood of the patient developing dengue shock syndrome/dengue hemorrhagic fever?

Screen their blood to determine if they have antibodies against a different serotype of DENV (serotypes 2-4). In addition, evaluate risk factors including age, genetics, and location.

How are subunit vaccines produced? What are the advantages/disadvantages to a "subunit" vaccine?

Subunit vaccines are vaccines that use only part of the disease-causing virus. Example: Hepatitis B and HPV Vaccine Advantages: -Subunit vaccines can be given to people with weakened immune systems. -These vaccines appear to give long-lived immunity -Since only parts of the virus are used for these vaccines, the risks of reactions are very low. Disadvantages: Several doses must be given for proper life-long immunity.

What makes the Ideal Virus Target for Vaccination?

The Ideal Virus Target for Vaccination • Genetically stable ---don't want something that will mutate quickly • Environmentally unstable ---don't want it to hang out in the population; want to get it into the target population and not bystander population • Only one host reservoir ---wan the single host to be human • Natural infection confers lifelong immunity ---if not you'll need more than one dose; problematic • Natural infection easy to detect (obvious disease in the host) ---some viruses don't have visible symptoms • Inefficiently transmitted prior to symptoms ---hard to transmit is better

What are the activities of the M2 protein and discuss the mechanism of antiviral activity against this protein.

The Matrix-2 protein is a proton-selective ion channel protein, integral in the viral envelope of the influenza A virus. The M2 protein from the influenza A virus forms a proton channel in the virion and is essential for infection. As a relatively conserved protein, the M2 protein seems to be a suitable candidate for development of a new generation of vaccine or antiviral agents. Due to the spontaneous mutations of these viral proteins, currently available antiviral and anti-influenza drugs quickly develop resistance.

What is vaccination? Who came up with this technique?

Vaccination was the process by which people were deliberately infected with the virus that causes another disease, the relatively mild cow-pox. Those who were given cow-pox virus were found to be immune if they were subsequently exposed to smallpox. (Vaccinia=cowpox). A vaccine is a substance that helps protect against certain diseases. Vaccines contain a dead or weakened version of a microbe. This technique was attributed to Edward Jenner, a British physician, (although there is evidence it was used earlier). It provided the same protection, with much less risk, and was so successful that it became a standard practice around the globe, culminating in a complete eradication of smallpox by 1977. Jenner noticed that milkmaids were protected from smallpox ---prior infection with cowpox? ---Lucky guess Jenner infected a 9 year old boy with cowpox. Then two weeks later, exposed boy to lethal smallpox infection and he survived. Cowpox does not replicate sufficiently in humans so it can't spread human to human. It has sufficient determinants and epitopes for antibody and t-cell response to be able to be used as a vaccine ---many viruses cause pox-like disease ---few are related to smallpox (cowpox is)

What is the difference between vaccines and antivirals? How does the duration of a virus infection influence the utility of an antiviral?

Vaccines prevent or mitigate infections. They are designed to induce a protective immune response in the body against the viruses represented in the vaccine. When vaccinated, the immune system of the body produces a specific response, consisting of specific T cells and specific antibodies that fight off the infection when exposure to the virus occurs at a later stage. More importantly, vaccination also leads to the induction of a specific immunological memory against the viruses represented in the vaccine. Upon contact with the virus at a later stage, the immune system is able to mount a specific response much more rapidly than the non-primed immune system. • Vaccines = Prophylactic o Intended to prevent disease o Induce an immune response in the body against viruses presented in the vaccine o Have provided considerable success in preventing viral disease o But they have modest or often no therapeutic effect for individuals who already are infected They can't stop an infection once it has started ---France has the lowest incidence of vaccinating they're kids Antivirals are drugs that can treat people who have already been infected by a virus. They also can be used to prevent or limit infection when given before or shortly after exposure, before illness occurs. A key difference is that the antiviral drug is effective only when administered within a certain time frame before or after exposure and is effective during the time that the drug is being administered. They can stop an infection once it has started

What is variolation? What is an example?

Variolation was the process by which people were deliberately infected with less-severe strains of smallpox virus with the intention that when they recovered (about 98% did), they would be immune to future infections even with the more deadly strain. This was practiced in China, Africa, and several countries in the Middle East right up to the mid-1700s. (Variola=smallpox). Practiced at least since the 11th century ---Smallpox scabs from a person who recovered from smallpox were blown into the nose of healthy person ---Healthy children wear underwear of infected children for seven days ---Inoculate pus from recovering person into small scratch on healthy person's arm ---Lower lethality than natural infection, but still high

How are killed vaccines produced? What are the advantages/disadvantages to a "killed" vaccine?

Virus stock produced in vitro in chicken eggs. Inactivated by heating or chemical treatment (formalin). Virus cannot replicate/infect cells. Mixed with preservatives and adjuvant Example: Influenza vaccine, Rabies Vaccine, Hepatitis A Vaccine Advantages: -Inactivated vaccines are more stable and safer than live vaccines. There is absolutely no chance the bacteria or virus in the vaccine can cause disease. The killed viral particles or bacteria are not able to come back to life! -The virus or bacteria is still recognized as an invader by the body even though it does not cause disease, so the immune system still makes protective antibodies against it. -The vaccine can be given to people with weakened immune systems -These vaccines do not usually need to be refrigerated. They can be stored easily and transported when freeze-dried. This makes them great vaccines to use in developing countries. Disadvantages: -Inactivated vaccines often stimulate a much weaker immune response than live vaccines. Therefore, there are typically several doses needed before gaining immunity to a disease. In addition, booster shots are sometimes needed to keep immunity to the disease. -No replication! • Few PAMPs produced • Consequence? • Solution: use of adjuvants (immune stimulatory compounds) -Few MHC-I and MHC-II peptides presented • Consequence? • Solution: booster vaccines (repeated injections) • Immune response to vaccine will be almost entirely B cell driven • Why? • If B cell response is not protective against natural infection, vaccine may lead to enhanced disease - Respiratory syncytial virus (RSV) vaccine failure

Describe the host transmission cycle of West Nile virus, including its main reservoir. Why are humans considered a dead-end host for West Nile virus? Is this true for dengue virus, and why?

West Nile virus is transmitted to humans by mosquitoes, and its main reservoir is birds such as crows. Humans are a dead end host because they don't have a high level of virus in their blood (viremia), so they are unable to pass the disease to new mosquitoes. This is not true for dengue because humans have a high viremia, and so can pass on the virus to new mosquitoes.

a. How would you generate an attenuated vaccine and a killed vaccine against Zika virus? b. What type of immune response would each one produce? c. Which vaccine would be best to administer for the elderly and why?

a. Attenuated vaccines are made by serial passaging the virus in unnatural host such as eggs or cell culture until it has acquired attenuating mutations that will not revert. Killed vaccines are produced by inactivating the virus with heat or formalin. b. Attenuated vaccines produce a strong immune response, B and T cell driven. Killed vaccines generate a weak immune response, and are mostly B cell driven. c. A killed vaccine is best for the elderly because there is no chance for reversion to virulence.

Answer the following TRUE (T) OR FALSE (F): a. Polyprotein processing of flaviviruses is performed only by viral protease NS3. b. Mosquitoes that are infected with flaviviruses can immediately infect new hosts. c. The antigenome of influenza functions like a mRNA. d. Antigenic shift is a consequence of genomic recombination. e. Influenza primarily replicates in the cytoplasm. f. Variolation was not an effective strategy for preventing smallpox. g. FluMist is a live attenuated vaccine for influenza virus. h. Yellow fever virus undergoes reassortment during virus assembly. i. A pandemic consists of a high number of infected individuals within a local community. j. The immune system can frequently exacerbate disease symptoms.

a. FALSE. Polyprotein processing is also performed by NS2B (and likely others) b. FALSE. Virus must replicate in mosquito mid-gut c. FALSE. Still not 100% sure d. TRUE e. FALSE. Replicates in nucleus f. TRUE g. TRUE h. FALSE i. FALSE. Pandemics are global. j. TRUE

(a) What are the protein targets for influenza virus antivirals and (b) how do they interfere with the virus life cycle?

a. M2 ion channel and Neuraminidase b. M2 inhibitors block entry by stopping H+ from entering the interior of virus, which causes uncoating. NA inhibitors block exit because they stop neuraminidase activity, which causes virus to bind back to precursor cell.

Describe the activity of neurminidase and any antivirals that have been developed against it.

an enzyme, present in many pathogenic or symbiotic microorganisms, that catalyzes the breakdown of glycosides containing neuraminic acid. Neuraminidase is an important target for influenza drugs Neuraminidase, on the other hand, plays its major role after the virus leaves an infected cell. It ensures that the virus doesn't get stuck on the cell surface by clipping off the ends of these polysaccharide chains. Neuraminidase inhibitors (NAIs) are a class of drugs which block the neuraminidase enzyme. They are commonly used as antiviral drugs because they block the function of viral neuraminidases of the influenza virus, by preventing its reproduction by budding from the host cell.

Stabilizing selection Directional selection Disruptive selection

directional selection: a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction disruptive selection: (or diversifying selection) a mode of natural selection in which extreme values for a trait are favored over intermediate values stabilizing selection: a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value In the absence of changing selection pressure, most viral mutations are neutral or make the virus less fit - stabilizing selection favors the "consensus" sequence • When the virus encounters a new host or new environment, some mutations may make the virus more fit - directional selection favors development of a new consensus sequence

Describe the mechanisms for generating genetic diversity in viruses. Key differences between RNA and DNA viruses

mutation: Polymerase base pair misincorporations. permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements. Mutations result from errors during DNA replication (especially during meiosis) or other types of damage to DNA such as radiation and random insertions and deletions of segments of DNA. recombination (all viruses): template switching during replication Self recombination occurs when two viral genomes recombine by homologous crossing over. These recombination events can be of evolutionary advantage for the virus when it helps to evade host immune defenses, for example by changing surface protein antigenicity. Recombination with host or other organism occurs when a viral genome recombine to acquire sequences from another organism Natural selection can retain acquired sequence if it gives an evolutionary advantage to the virus and mutations can modify its original functions. Example: RNA and retroviruses, Corana virus reassortment (segmented viruses): Reassortment occurs event when two similar segmented viruses exchange part of their genomes during a cell co-infection . This event occurs in all segmented viruses . It is particularly studied for Influenza virus, since reassortment is the major event giving rise to new flu pandemics Example: influenza virus RNA viruses: high mutation rates (drift), recombination, and reassortment (shift) - Near the theoretical "error threshold" for maintenance of viral information: as sloppy as they can get and still replicate • DNA viruses: recombination, limited mutation - Recombination with host genes yields novel phenotypes

A human-induced rabbit virus pandemic: the first inter-species bioterrorist attack

•24 European rabbits introduced to Australia in 1858 by hunters •No natural predators or diseases •Rabbits rapidly became devastating agricultural pests •Highly virulent rabbit pox (myxoma) introduced in 1950 in an attempt to eliminate rabbits; initially very successful with >99% lethality during first infections Both rabbits and myxoma rapidly evolved to an attenuated, stable relationship

Describe the genome of influenza virus and the number of proteins produced during infection.

segmented genome 8 ssRNA segments As in all viruses, the genome of an influenza virus particle is encased in a capsid that consists of protein. the influenza A genome contains eight genes encoding 11 proteins.

Why are flaviviruses important human pathogens? Example?

single-stranded, enveloped RNA viruses that are transmitted to humans primarily through the bites of arthropods flaviviruses spread quickly and easily Example: Dengue and Yellow Fever and Zika

What is a zoonotic infection, and what types of human activities introduce new zoonoses into the populution?

zoonotic infection: a disease spread between animals and people. Zoonotic diseases can be caused by viruses, bacteria, parasites, and fungi. Diseases that arise from microbes that infect other animals Lots of variables leading to emergence - Thought to be zoonotic in origin - Increased human population - Human travel - Frequent mutation - Human social interaction • Sexual practices • IV drug use • Blood transfusions

***H5N1: Why it's so scary

• Domestic birds in close contact with wild migratory birds who carry the virus • Once in domestic birds, increased virulence and capable of species jumping • Humans in close contact with infected wild and domestic birds • Domestic birds transmitting the virus back to wild migrating birds which are for the first time exhibiting symptoms of disease

What are the characteristics of an ideal virus vaccine? For each of the points be prepared to expand on them.

• Effective with a single dose ---most are live viruses vaccines currently unfortunately ---some people may not come back for the other doses • Oral (needles are expensive and spread disease) ---some people don't like needles • Cheap (<$1 per person) ---so a large portion of the population can be vaccinated • Stable (without refrigeration) ---avoid cold conditions • Safe (Low risk of complications)

How does a vaccine becomes approved for human use? Why is drug development such an expensive and time-consuming process? What are the three basic stages of drug development?

• Preclinical evaluation: 1-2 years - large scale animal studies of immunogenicity and safety • Clinical trials: (these are generally the same for vaccines or any other medical intervention) - Phase I: 20-100 volunteers, ~2 years: safety, side effects - Phase II: 100-300 volunteers, >2 years, immunogenicity - Phase III: 10,000+ volunteers, up to 4 years, large scale effectiveness trials to generate statistically significant data across a broad population Application for FDA approval: can take > 1 year. • Start to finish: ~ 10 years, $500 million +