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Cornell Institute for Biology Teachers Title Viral Reproduction and Budding Demonstration # 1 Modified from CIBT (EB-97) authors Patricia Nolan Bertino and James Blankenship Author CIBT EB-97 Patricia Nolan Bertino, Scotia-Glenville High School (retired), Scotia, NY Demo # 1 Viral Reproduction Teacher Section Page 1 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008 Appropriate Level This activity is appropriate middle and high school students. Objectives After viewing this activity, students should be able to: 1. Describe how a virus replicates inside a host cell 2. Describe how an infected cell undergoes lysis and releases newly formed viruses. 3. Distinguish between an enveloped virus and a non-enveloped virus. 4. Explain how a virus spreads from infected cells to healthy cells 5. Relate the balloon simulation of viral replication to a the replication of HIV within an infected host Materials 4 Medium-sized balloons of the same color (host cell) Scissors 4 5X8 cards Cut up pieces of papers inserted into balloon (new viruses) 4 Pins used to pop the balloons 8 Styrofoam balls (or ping pong balls) to represent HIV 2 gallon-sized zipped-lock baggie to represent the host cell membrane 4 rubber bands HHMI DVD entitled: 2000 and Beyond: Confronting the Microbe Menace HHMI DVD entitled: AIDS: Evolution of an Epidemic ( Or connect to HHMI website www.biointeractive.org ) Safety Do not use latex balloons if anyone in the class has a latex allergy. Objectives . This demonstration takes 15 minutes. Time CIBT EB-97 Demo # 1 Viral Reproduction Teacher Section Page 2 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008 Abstract A balloon filled with small pieces of cut-up papers is used to simulate how a host cell infected with a virus may later “explode” or undergo lysis and release many copies of the virus attacking healthy cells. This is an excellent demo to describe enveloped viruses. HIV reproduction is described in terms of budding out of the host cell. As the host cell produces more viruses, some of the newly synthesized HIV will bud through the cell membrane. In doing so, the newly synthesized virus does not cause a complete lysis of the cell, but instead will carry part of the lipid cell membrane around the virus forming an envelope. Because the virus is enveloped in the host’s cell membrane, it is more difficult for the immune cells to recognize the virus. To demonstrate an enveloped virus such as HIV, place eight Styrofoam balls inside of a large zipped locked baggie. The Styrofoam balls represent newly synthesized HIV. To show how the newly formed HIV buds out of the host cell, wrap rubber bands between the zipped locked bag and four of the Styrofoam balls that are located inside of the baggie. Procedure Advance Preparation Infected Host cells 1. Select 4 medium-sized balloons all the same color and shape to represent host cells. 2. Cut a 3X5 card into small pieces of paper to be used as viruses. 3. Stretch the opening of a deflated balloon and insert the cut pieces of the cut up pieces of the 3X5 card into the open mouth of the balloon. 4. Inflate the balloon and tie it off. 5. Repeat steps 2-5 so that you have a total of 4 inflated balloons (infected host cells) all containing the paper pieces (virus) Budding virus from an infected host cell 6. Place one ball into a gallon-sized zip-locked baggie and seal This represents a host cell infected with one virus 7. Place the remaining 7 balls into a different gallon-sized zip-locked Baggie. This represents an infected host cell with 7 virus particles. 8. Using the baggie containing the 7 balls (viruses), wrap a rubber band over the baggie and one of the balls (virus). Wrap a rubber band over the baggie and the ball to demonstrate an enveloped virus. 9. Repeat this for three more of the balls (viruses) inside the baggie. When finished you should have 4 enveloped viruses inside the host cell (baggie) and 3 viruses not enveloped. Demonstration 1. Ask students to try to explain why the symptoms of a viral infection such as a cold seem to intensify over a period of several days and ultimately disappear. CIBT EB-97 Demo # 1 Viral Reproduction Teacher Section Page 3 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008 2. Hold the inflated balloon over the head of a student. Explain that the balloon represents a viral infected host cell in their body. Each student in the class represents healthy cells within the body. Using a pin, pop the balloon releasing all of the “paper” viruses inside of the “balloon” or host cell. Check to see how many “students” or healthy cells are now infected. Ask the newly infected cells to stand. Ask students to relate this demonstration to someone just exposed to the cold virus and the progression of symptoms. 3. Give the 3 other inflated balloons (infected host cells) filled with paper to 3 of the newly infected “students” or cells along with a pin. Ask the students to stand and hold the balloon over their heads. On the count of three, each of the infected cells (students) will pop the balloon representing lysis of the infected cell. 4. Observe how the virus continues to spread to other healthy cells in the area. Ask the newly infected “students” or host cells to please stand along with any previously infected host cells. 5. Ask students to predict what happens to the host if the virus is not eliminated from the host. 6. Ask the students to brainstorm ideas on how the body fights a viral infection enabling a person to stop exhibiting symptoms of the virus. 7. Show the HHMI animation entitled: “ Viral Life Cycle” 8. Show the students the one large baggie (host cell) containing the one ball (virus). Ask the students to summarize from the animation what happens in the host cell that results in an increase in the number of viruses inside of the host cell. 9. Show the students the model of the budding enveloped viruses from an infected host cell. (Large baggies containing the 7 viruses: 4 budding and 3 non-budding viruses.) 10. Ask students to describe how a virus forms an enveloped virus. 11. Have students compare the body’s ability to seek and destroy an enveloped virus versus a non-enveloped virus. 12. Introduce the idea of viral latency. Use the Herpes virus as an example of a virus that may infects and then becomes latent for varying amounts of time before another outbreak of symptoms. Ask students to hypothesize as to what happens to the virus during this latency period. CIBT EB-97 Demo # 1 Viral Reproduction Teacher Section Page 4 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008 Further Study Ask students to elaborate on this model and create a model that would demonstrate how specific viruses will only invade specific host cells. This model could be a three-dimensional model or graphic model presented in the form of a PowerPoint presentation. References HHMI animation: Viral Life Cycle (1 min. 8 sec.) HHMI Holiday Lecture; Infectious Disease: 2000 and Beyond: Confronting the Microbe Menace Hour 1 DVD Chapter 13 animation: Viral Infection Additional Reference for Instructors HHMI Holiday Lecture Infectious Disease: 2000 and Beyond: Confronting the Microbe Menace Hour 1 “Microbe Hunters: Tracking Infectious Agents” Chapter 10: What are Viruses? Chapter 12: How does a Virus Affect a Cell? Hour 4 “ Emerging Infections: How Epidemics Arise” DVD Chapter 20 Recombination of Viral RNA in a Host Cell (3 min. 04 sec) Animation: Recombination of Viral Genome (3 min. 5 sec) HHMI Holiday Lectures AIDS Evolution of an Epidemic 2007 Hour 2 add title of hour 2 DVD chapter 16 HIV Life Cycle Part 1 CIBT EB-97 Demo # 1 Viral Reproduction Teacher Section Page 5 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008 CIBT EB-97 Demo # 1 Viral Reproduction Teacher Section Page 6 ©1997 Cornell Institute for Biology Teachers, Ithaca, NY 14853. Distribution of this laboratory exercise is permitted if (i) distribution is for non-profit purposes only, (ii) this copyright notice appears on each copy. Lab issue/rev. date: 8/31/97 revised 3/12/2008