The key difference between virus and prion is that the virus is a tiny infectious particle composed of nucleic acids and a protein coat while the prion is a small infectious particle composed of a single protein.
There are different types of biological entities studied by microbiologists. Among them, virus and prion are two types of acellular infectious particles. They are not considered as living organisms since they show more non-living characteristics than living characteristics. Similarly, they do not contain ribosomes and enzymes to synthesize proteins. Hence, they need a living organism (host) to multiply. Furthermore, they cannot be observed under the light microscopes, and they cannot be filtered out by Chamberland filters. Moreover, they are not culturable in nutrient media. The difference between virus and prion is mainly due to their composition. Viruses consist of nucleic acids and proteins while prions consist only of proteins. Likewise, there are several differences between virus and prion which this article will discuss.
CONTENTS
1. Overview and Key Difference
2. What is Virus
3. What is Prion
4. Similarities Between Virus and Prion
5. Side by Side Comparison – Virus vs Prion in Tabular Form
6. Summary
What is Virus?
Virus is a nanometer size infectious particle composing a protein coat and nucleic acids. Thus, viral nucleic acids can be either DNA or RNA. Nucleic acids can be single or double-stranded. Furthermore, they can be linear or circular or segmented. Structurally, nucleic acids remain protected within the protein capsid. Protein capsid may contain spikes and tails. These spikes and tails help the viruses to attach with the host cells.
Based on the protein capsid arrangement, viruses have different shapes such as helical, icosahedral, polyhedral and complex structures. Other than the nucleic acids and protein capsid, some viruses possess an envelope that encloses the nucleocapsid. Thus, there are enveloped virus while others are naked virus. Using these nucleic acids, viruses multiply inside a living organism (host) via five steps; attachment, penetration, replication and synthesis, assembly and release. Hence they are obligate parasites. In simple words, viruses need a living host to make proteins and multiply.
Figure 01: Virus
There are different types of virus based on the host organism that they use to multiply. A bacteriophage is one type which infects bacteria. Mycoviruses infect fungi while archaeal viruses infect archaea. Furthermore, there are animal viruses, plant viruses, protists viruses, and mammalian endogenous retroviruses. As the name suggests, these virus use different host organisms to multiply while causing diseases to them.
What is Prion?
Prion is a subviral entity composed only of a protein. Simply, it is a proteinaceous infectious particle which is acellular. Prion neither has DNA nor RNA. Hence they lack genes. This is the distinguishing character of prions that separates prions from viruses. Surprisingly, prion proteins are harmless proteins that are present in mammals and birds. But these proteins are in abnormal form, and once they enter the human brain, they are capable of causing severe brain infections.
Figure 02: Prion
Normally these prions are ingested, but they also get formed through mutation of a gene that contains this protein. As soon as prion finds their way into the brain, they cause normal proteins to turn into abnormal ones. Then afterwards, they soon multiply causing severe infection in the brain. Due to this infection, some holes appear inside the brain that can only be treated by incineration. Some of the diseases caused by prion are Mad Cow Disease, Scrapie in sheep and goat, chronic wasting disease in deer and elk, kuru and Creutz-Jakob disease. However, prions do not cause infections in plants, unlike viruses. Though prion causes diseases in humans and other animals, prion diseases are very rare. Furthermore, there are no specific treatments for prion diseases. Because prions are resistant to most of the sterilization methods such as heat, radiation, chemicals, etc.
What are the Similarities Between Virus and Prion?
- Virus and prion are non-living particles.
- Furthermore, they are acellular.
- Virus and prion are harmful.
- Both cause many diseases to be human and other organisms.
- Also, they need a host organism to multiply.
- Hence, they are obligate parasites.
- Moreover, both do not contain ribosomes.
- But, both contain proteins.
- Furthermore, they are very small, even smaller than the bacteria.
What is the Difference Between Virus and Prion?
Virus is an infectious particle made from both nucleic acids and proteins while prion is a sub-viral entity composed only of a protein. This is the key difference between virus and prion. Furthermore, viral diseases are common while prion diseases are rare. Moreover, prion causes diseases to humans and animals while virus causes diseases to animals, plants, fungi, bacteria, protists and archaea. Hence, this is also a notable difference between virus and prion.
The below infographic on difference between virus and prion shows the differences more clearly in tabular form.
Summary – Virus vs Prion
Virus and prion are two types of infectious particles, which are acellular and non-living. The key difference between virus and prion is that virus is composed of both nucleic acids and proteins while prion is composed only of a protein. Prion lacks DNA or RNA while viruses possess nucleic acids either DNA or RNA. Furthermore, virus causes diseases to animals, plants, bacteria, protists, archaea, etc. while prion causes diseases only to human and animals.
Reference:
1.Gelderblom, Hans R. “Structure and Classification of Viruses.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 1 Jan. 1996. Available here
Image Courtesy:
1.”Virus stucture simple”By GrahamColmTalk – Own work (CC BY-SA 3.0) via Commons Wikimedia
2.”BOVINE PRION PROTEIN 1dx0 asym r 500″By Lopez-Garcia, F., Zahn, R., Riek, R., Wuthrich, K. & RCSB (Public Domain) via Commons Wikimedia