8 - Virus Introduction

viruses

obligate intracellular pathogens in that they must enter a cell to replicate

obligate intracellular pathogens

what type of pathogens are viruses?

10 to 100 nm in diameter

size of viruses

electron microscope

what microscope can you appreciate the morphology of viruses in?

virions

complete virus particles

virions

extracellular form of the virus that is not capable of reproduction but is capable of infecting

virions

simples form of human viruses

protein coat (capsid)

what do you call the coat of all viruses?

capsid

consists of repeating capsomeres

capsomeres

what composes the capsid?

capsomeres

building blocks of capsid

capsomeres

small protein units

capsid

what is this?

capsomeres

what are the small circles called?

nucleic acid

what do you call the black component in the center?

enveloped virus

what type of virus?

non-enveloped virus

what type of virus?

naked virus

other name for non-enveloped virus

lipoprotein envelope

enveloped virus are covered with what?

• icosahedral

• helical

two types of capsid

• nucleic acid genome

• capsid

what makes up nucleocapsid?

• DNA (deoxyribonucleic acid)

• RNA (ribonucleic acid)

genomes of virus

surface proteins

attachment to host cell receptors

envelope protein

what is the first structure being pointed?

envelope

what is the second structure being pointed?

viral genome

what is the third structure being pointed?

nucleocapsid

what is the fourth structure being pointed?

viral tegument

what is the fifth structure being pointed?

• dna

• rna

viruses posses which genomes?

• ribosomes

• mitochondria

what does viruses not contain?

viruses

unable to replicate, make protein and nucleic acid on their own

• ribosome enzymes

• metabolites

where does viruses rely on?

• genes

• enzymes

viruses can metabolize because they lack what?

viral replication

how does viruses reproduce?

• Herpes virus

• Hepadnavirus

• Adenovirus

• Papovavirus

• Poxvirus

• Parvovirus B19

DNA viruses

• Herpes Simplex Virus

• Varicella Zoster Virus

• Cytomegalovirus

• Epstein Barr Virus

examples of herpes virus

Hepatitis B

example of hepadnavirus

human papillomavirus (HPV)

example of papovavirus

• molluscum

• smallpox

• orf

• milker’s nodule

diseases caused by poxvirus

Parvovirus B19

the only single-stranded DNA virus

Hepatitis B virus

what virus

Herpes simplex virus

what virus

adenovirus

what virus

parvovirus

what virus

human papilloma virus

what virus

Reoviruses

the only double stranded rna virus

DNA → Transcription (mRNA) → RNA → Translation (tRNA) → Protein

central dogma of genetics

RNA viruses

viruses that are just like a messenger RNA

RNA viruses

enters a host cell, its RNA can immediately be translated by the host’s ribosomes into protein

DNA viruses

viruses that cannot be translated directly into proteins

NDA viruses

it must be transcribed into mRNA with subsequent translation of mRNA into structural proteins and enzymes

• double-stranded DNA

• single-stranded RNA

• single-stranded DNA

• double-stranded RNA

categories of viruses based on the of genomes they possess

Parvovirus B19

the only single stranded DNA virus

• circular

• linear

categories of viruses based on the shape of genome

• icosahedral

• helical - coiled tubes

• spherical

• complex

categories of viruses based on the shape of capsids

• attachment

• penetration

• uncoating

• biosynthesis

• assembly

• release

viral replication process

attachment

phase of viral replication where influenza virus becomes attached to a target epithelial cell

penetration

phase of viral replication where the cell engulfs the virus by endocytosis

uncoating

phase of viral replication where viral contents are released

biosynthesis

phase of viral replication where viral RNA enters the nucleus, where it is replicated by the viral RNA polymerase

assembly

phase of viral replication where new phage particles are assembled

release

phase of viral replication where new viral particles are made and released into the extracellular fluid. The cell, which is not killed in the process, continues to make virus.

inclusion bodies

remnants of infected cells which may be found in the cytoplasm or within the nucleus

• Negri bodies

• Owl eyes inclusion

examples of inclusion bodies

Negri bodies

cytoplasmic inclusion bodies in nerve cells of cells infected with rabies

owl eyes inclusion

intranuclear inclusion body for CMV (cytomegalovirus)

laten virus infections

infectious disease that may go from symptomatic to asymptomatic, then sometime later go back to symptomatic

• herpes virus infections

• shingles/varicella zoster infection

examples of latent virus infections

• infected person is always harboring virus in nerve cells

• fever, stress, or excessive sunlight can trigger the viral genes

• produce more viruses

• cold sore develops

herpes virus infection pathophysiology

• occurs after a chickenpox infection

• virus remains latent in the dorsal root nerve ganglia

• weakened immune system

• laten chickenpox virus resurfaces

shingles pathophysiology

oncogenic viruses

viruses that can cause cancer

• Epstein-Barr Virus

• Human Herpes Virus 8

• Hepatitis B and Hepatitis C

• Human Papilloma Virus

• Human T Lymphotrophic Virus 1

examples of onxogenic viruses

• nasopharyngeal carcinoma

• Burkitt lymphoma

• B-cell lymphoma

diseases caused by Epstein-Barr Virus as an oncogenic virus

Kaposi’s Sarcoma

diseases caused by Human Herpes Virus 8 as an oncogenic virus

hepatocellular carcinoma

diseases caused by Hepatitis B and Hepatitis C as an oncogenic virus

• cervical cancer (women)

• penile cancer (men)

diseases caused by Human Papilloma Virus as an oncogenic virus

adult T-cell leukemia

diseases caused by Human T Lymphotrophic Virus 1 as an oncogenic virus

Human T Lymphotrophic Virus -1

the only RNA oncogenic virus provided in the ppt

cell destruction

most of the symptoms of the viral infection are a result of