In 2000, ViroPharma, a pharmaceutical company, conducted clinical trials for pleconaril, a new pill designed to treat the common cold. While the pill proved effective for many patients, seven of them developed mutated virus variants that were almost completely resistant to pleconaril just a few days into the treatment. This rapid mutation outmaneuvered years of research and development, highlighting the challenges of treating viral infections.
Without an immune system, a cold infection could quickly spread deep into the lungs, leading to tissue destruction and eventual asphyxiation due to insufficient oxygen supply. This is a real risk for millions of people worldwide living with a less-than-fully-functional immune system or those on immunosuppressant drugs. However, for those with a fully functional immune system, a cold usually results in relatively mild symptoms.
On average, adults catch more than 150 colds throughout their lives. Despite similar symptoms, the cause could be different each time. Common colds are caused by at least eight different families of viruses, each with its own species and subtypes. These viruses invade our bodies in a few ways, one of which is through the air we breathe. Our immune system sets up frontline defenses that produce many of the symptoms of a cold, such as a runny nose, fever, and inflammation.
Given that the common cold is caused by many different viruses, finding a cure is challenging. However, one fact in our favor is that a single family of viruses, rhinovirus, causes 30 to 50% of all colds. If we could eliminate all rhinovirus infections, we’d go a long way towards curing the common cold. There are two main ways to fight a virus: vaccines and antiviral drugs.
The first attempt to create a rhinovirus vaccine in 1957 was a short-lived success. William Price vaccinated 50 kids with inactivated rhinovirus and gave 50 others a placebo. A rhinovirus outbreak soon followed, and only three kids in the vaccinated group got sick compared to 23 in the placebo group. However, later trials of the vaccine showed no protection at all due to the multiple subtypes of rhinovirus.
Creating antiviral drugs is also challenging because viruses hijack human cellular machinery to replicate and spread. It’s hard to make a molecule that’s toxic to the virus without also being toxic to the human. Even if this is achieved, the virus could mutate out of reach of the drug.
Despite these challenges, there have been some incredible successes. Smallpox was eradicated thanks to an effective vaccine, the fact that it can’t hide out in other species, and its relatively low mutation rate. HIV, which mutates quickly, can be managed with an effective cocktail of drugs that the virus can’t easily mutate away from.
While we are stuck with colds for now, the last few decades have featured some entirely game-changing medical breakthroughs, like mRNA vaccines and CRISPR. CRISPR, which originally evolved in bacteria as an immune defense against viruses, could be particularly promising as an antiviral agent. Early in the COVID-19 pandemic, a research team showed that a CRISPR system could degrade coronavirus and influenza genomes in our lung cells. They called their system prophylactic antiviral CRISPR in human cells, or PAC-MAN for short.
Create a simple simulation to understand how viruses mutate. Use colored beads or paper clips to represent different virus strains. Start with a single color and introduce new colors to show mutations. Discuss how these mutations can make it difficult to treat viral infections like the common cold.
Organize a role-play activity where you act as different parts of the immune system (e.g., white blood cells, antibodies) and viruses. This will help you understand how the immune system fights off infections and why it’s crucial for preventing severe illness from the common cold.
Conduct a research project on different antiviral drugs and how they work. Present your findings to the class, focusing on the challenges of creating effective antiviral drugs without harming human cells. Include examples like pleconaril and discuss why some drugs fail.
Participate in a debate on the effectiveness of vaccines versus antiviral drugs in combating viral infections. Form teams and argue for one method over the other, using evidence from the article and additional research. This will help you understand the pros and cons of each approach.
Explore the potential of CRISPR technology as an antiviral agent. Watch a video or read an article about how CRISPR works and its applications in medicine. Discuss in groups how CRISPR could be used to treat viral infections like the common cold and what challenges scientists might face.
Clinical Trials – Scientific studies conducted to evaluate the safety and effectiveness of medical treatments or interventions on human subjects. – The new drug is currently undergoing clinical trials to determine its efficacy in treating cancer patients.
Pleconaril – An antiviral medication used to treat certain viral infections, particularly those caused by enteroviruses. – The doctor prescribed pleconaril to the patient to help alleviate the symptoms of their enterovirus infection.
Mutated Virus Variants – New strains of viruses that have undergone genetic changes or mutations, potentially leading to different characteristics or behaviors. – The emergence of mutated virus variants has raised concerns about the effectiveness of existing vaccines.
Research and Development – The process of investigating and creating new products, technologies, or treatments through scientific research and experimentation. – The pharmaceutical company invests a significant amount of resources in research and development to discover novel treatments for various diseases.
Viral Infections – Illnesses caused by the invasion and replication of viruses within the body, often resulting in specific symptoms and immune responses. – Common examples of viral infections include the flu, colds, and COVID-19.
Immune System – The body’s complex network of cells, tissues, and organs that work together to defend against harmful pathogens and foreign substances. – A strong immune system helps protect the body from various infections and diseases.
Cold Infection – A common viral infection primarily affecting the upper respiratory tract, characterized by symptoms such as sneezing, runny nose, and congestion. – The cold infection made the patient feel fatigued and congested for several days.
Tissue Destruction – The process of damage or degeneration of body tissues, often caused by infections, diseases, or injury. – The severe infection resulted in significant tissue destruction in the affected area, requiring surgical intervention.
Symptoms – Physical or mental manifestations experienced by an individual that indicate the presence of an illness or medical condition. – Some common symptoms of the flu include fever, cough, sore throat, and body aches.
