The Elusive Common Cold

In 2000, ViroPharma conducted clinical trials for pleconaril, a novel pill aimed at treating the common cold. While the medication proved effective for many patients, researchers discovered a disheartening reality. Within just a few days of treatment, seven individuals developed mutated virus variants that were highly resistant to pleconaril. This particular virus strain exhibited an astonishing rate of mutation, rapidly outmaneuvering years of research and development. This highlights the ongoing challenge of combating the common cold, especially for individuals with compromised immune systems or those taking immunosuppressant drugs.

For individuals without a fully functional immune system, a common cold infection can quickly progress and spread deep into the lungs. Rampant viral replication can lead to the destruction of lung tissue, hindering the supply of oxygen and potentially causing asphyxiation. This poses a genuine risk to millions of individuals worldwide. Even though common cold symptoms are usually mild for those with a healthy immune system, it's important to acknowledge that each cold episode may be caused by different viruses.

The common cold stems from at least eight different families of viruses, each with its own species and subtypes. Despite the similarity in symptoms, these viruses trigger our immune system through various entry points. One common pathway is inhalation, which prompts the immune system to deploy frontline defenses. These defenses, in turn, generate many of the familiar cold symptoms. For instance, the production of mucus and a runny nose is the immune system's way of trapping and flushing out the virus. Fever is the body's response to hinder viral replication by raising its temperature. Inflammation occurs as the immune system widens blood vessels and recruits white blood cells to combat the virus.

Given the diverse array of viruses responsible for the common cold, finding a cure seems daunting. However, there is a glimmer of hope. One particular viral family, rhinovirus, accounts for 30 to 50% of all colds. If we could eliminate rhinovirus infections, significant progress would be made towards curing the common cold. Two primary approaches to fighting viruses exist: vaccines and antiviral drugs.

The initial attempt to create a rhinovirus vaccine in 1957 showed promising results. Vaccinated children displayed significantly lower infection rates compared to those who received a placebo. However, subsequent trials of the vaccine failed to provide any protection at all. This setback was largely due to the discovery that rhinovirus encompasses multiple subtypes, rendering the vaccine's limited effectiveness against a vast array of strains.

Developing antiviral drugs poses its own set of challenges. Viruses rely on the cellular machinery of their hosts to replicate and spread, making it difficult to target the virus without harming human cells. Furthermore, even if an effective antiviral drug is developed, the virus may mutate, rendering the drug ineffective. Nevertheless, there have been remarkable successes in antiviral drug development, such as the effective cocktail of drugs used to combat HIV.

Despite the continued absence of a cure for the common cold, the past few decades have witnessed groundbreaking medical advancements, including mRNA vaccines and CRISPR technology. CRISPR, with its origins in bacteria as a defense against viruses, shows promise as an antiviral agent. Preliminary research during the COVID-19 pandemic demonstrated that a CRISPR system can degrade coronavirus and influenza genomes in human lung cells, offering potential avenues for future antiviral treatments.

While the common cold remains an enduring challenge, ongoing scientific endeavors hold the promise of eventually conquering this ubiquitous illness.

Henrik Leandro