VIRUSES, VIROIDS, AND PRIONS

Virus

Have DNA or RNA; single type of nucleic acid (DNA or RNA) 

Viroids

only RNA

Prions

NO DNA or RNA

Virus

Protein coat (capsid) present (sometimes itself enclosed by an envelope of lipids, proteins, and carbohydrates) that surrounds the nucleic acid

Viroids

Lacking a protein coat

Prions

Misfolded proteins

Virus

Causes disease in plants, animals and humans

Viroids

Infects plants

Prions

Cause disease in animals and humans

Virology

the scientific study of viruses

Edward Jenner

• smallpox vaccine, 1796 Orthopoxvirus

  • Smallpox virus Baltimore Group I (dsDNA)

Charles Edouard Chamberland 

Pasteur-Chamberland filter

Chamberland Filter

Porcelain filter, remove bacteria from liquids 

• pivotal in the discovery of viruses 

• Smaller than bacteria

Dmitri Ivanovsky

Russian Botanist & Virologist 

Dmitri Ivanovsky

• Tobacco Mosaic Virus, 1892 

• Groundwork for the discovery of viruses

TMV (Tobacco Mosaic Virus)

Is a plant virus that infects tobacco and other plants, causing characteristic mosaic patterns on leaves. Model organisms in virology research

Virus

Multiply inside living cells by using the synthesizing machinery of the cell

Virus

Cause the synthesis of specialized structures that can transfer viral nucleic acid to other cells

Icosahedral, Helical, and Complex

General Morphology of Viruses

Icosahedral

Polyhedral shape with 20 triangular faces, Adenovirus

Helical

Rod-shaped, with the capsid proteins arranged in spiral, Tobacco mosaic virus 

Complex

icosahedral and helical structures, Bacteriophages

Enveloped Viruses

Have a lipid membrane derived from the host cell.

Enveloped Viruses

More susceptible to environmental stress, disinfectants, and drying

Enveloped Viruses

Often rely on specific interactions between viral envelope proteins and host cell receptors for attachment and entry

Non-enveloped Viruses

Lack a lipid membrane, with only a protein (glycoprotein) capsid.

Non-enveloped Viruses

Generally, more resistant to environmental stress, disinfectants, and drying

Non-enveloped Viruses

Can survive longer outside host cells.

Baltimore Classification

Grouped according to how their mRNA is produced

PRC

amplifies viral genetic material for detection 

Sequencing

 viral genome sequence

Serology

detects antibodies or antigens in blood or tissues

Electron Microscopy

visualizes viral particles

Cell Culture

grows viruses in controlled environments

Taxonomy of virus

• virus: genus names 

• viridae: family name 

• ales: order

• In formal usage, the family and genus names are used in the following manner: Family Herpesviridae, genus Simplexvirus, human herpesvirus-2

Baltimore Classification

• Groups viruses into 7 classes based on their genome type and replication strategy

1. I: dsDNA viruses 

2. II: ssDNA viruses 

3. III: dsRNA viruses 

4. IV: (+)ssRNA viruses 

5. V: (-)ssRNA viruses 

6. VI: ssRNA-RT viruses 

7. VII: dsDNA-RT viruses

CLASS 1: dsDNA VIRUSES

Human Papillomavirus (HPV) is a common sexually transmitted infection (STI) that can cause various health problems.

Human Papillomavirus (HPV)

is a common sexually transmitted infection (STI) that can cause various health problems. 100 different types of this are classified into high risk (cancer causing HPV 16 and HPV 18) and low risk categories (genital warts, HPV 6 and HPV 11)

Rotaviruses

• Can cause severe diarrhea in infants and young children

• Rotavirus vaccine

Reoviruses

• Can infect various humans, mammals and birds 

• Potential use in oncolytic virotherapy