Common Cold Viruses: Isolation and Analysis in the Laboratory

Understanding the common cold is crucial for developing effective preventive and therapeutic measures. This article delves into the isolation and analysis of viruses that cause colds in laboratory settings, focusing on two prominent types: rhinoviruses and adenoviruses. We also compare these findings with more recent studies to understand the evolving landscape of cold viruses and their impact.

Historical Studies on Common Cold Viruses

In the 1960s, research conducted by Thomas and colleagues identified rhinoviruses, herpesviruses, and adenoviruses as the main culprits behind common cold symptoms in a small study of college and medical students. The study, which analyzed 111 specimens obtained during the 1963-1964 school year, revealed that mild sore throat, rhinorrhea, cough, and general malaise were associated with rhinovirus and herpesvirus isolations. In contrast, adenovirus was linked to more severe symptoms such as marked sore throat, cervical adenopathy, conjunctivitis, and high fever.

Rhinoviruses: Profiles and Characteristics

A more extensive study from 1998 analyzed 200 young adults with common cold symptoms over a 10-month period, using various techniques including virus culture, antigen detection, PCR (Polymerase chain reaction), and serology with paired samples. The study found that 105 out of 200 patients (52.5%) contracted rhinoviruses, making it the most common cause of the common cold. Other viruses identified included coronaviruses (OC43 and 229E), influenza A and B viruses, and single infections with parainfluenza viruses, respiratory syncytial virus, adenovirus, and enteroviruses. Bacterial infections, though identified in some cases, were rare, supporting the notion that the common cold is predominantly a viral disease.

Structural Analysis of Rhinoviruses

From a structural perspective, rhinoviruses are described as having single-stranded positive-sense RNA genomes, typically between 7200 and 8500 nucleotides in length. The 5' end of the genome encodes a viral protein, similar to mammalian mRNA, and there is a 3' poly-A tail. Structural proteins are encoded in the 5' region, while non-structural proteins are encoded at the 3' end. The viral particles are non-enveloped, and icosahedral in structure, composed of a capsid containing four viral proteins (VP1, VP2, VP3, and VP4), each with 60 copies.

Recent Insights into Coronavirus

A 2016 study provided insights into a different cold virus, the coronavirus, which is characterized as being large and enveloped with a positive-stranded RNA genome ranging from 27 to 32 kb. The RNA genome is packed inside a helical capsid formed by the nucleocapsid protein N and is further surrounded by an envelope. This structural information is essential for the development of antiviral therapies and vaccines.

Diagrams and Visual Representations

We have included diagrammatic representations of these viruses to provide a clear visual understanding. The first diagram shows a rhinovirus, which has the characteristic icosahedral structure. Another diagram illustrates the structure of the coronavirus, emphasizing its helical capsid and envelope structure.

Conclusion

Despite the advancements in research and the availability of various diagnostic and therapeutic tools, understanding the precise role of each virus in causing the common cold, and how these roles might change over time, remains crucial. Future studies should focus on large-scale population studies to monitor viral prevalence and develop new strategies to control and prevent the common cold.

References

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