May 8th Exam 5/6

Viruses are

Obligate intracellular parasites (Can infect anything)

General size of viruses

1-2 um (Needs electron microscope)

Viruses have

Central core or a covering

Capsids

Protein that encloses and protects their nucleic acid

Nucleocapsid

Capsids + Nucleic acid

Envelope

External covering that acts as a extra layer of protection for viruses

Naked

A virus that doesn’t have a envelope

Capsomers

Identical protein subunits that makes up a capsid

Viral envelope

Mostly animal viruses, acquired when the virus leaves the host cell, has spikes on the outside used to attach to host cells

Complex/Atypical Viruses are

complex viruses

Bacteriophages

Viruses that infect bacterial cells (Complex/Atypical virus)

Poxviruses

Complex/Atypical virus that infects bacterial cell

Viral genome

Either DNA or RNA, not both that’s used by viruses to infect host cells to create more viruses

DNA viruses

Usually double stranded (ds) but may be single
stranded (ss), Circular or linear

RNA viruses

Usually single-stranded, may be double-stranded, may
be segmented into separate RNA pieces

Enzymes in viruses

Polymerase, Replicase, and Reverse Transcription

Adsorption (1/6)

binding of virus to specific molecules on
the host cell

Penetration (2/6)

genome enters the host cell

Uncoating (3/6)

the viral nucleic acid is released from the
capsid

Synthesis (4/6)

viral components are produced

Assembly (5/6)

new viral particles are constructed

Release (6/6)

assembled viruses are released by
budding (exocytosis) or cell lysis

Host range

Variety of host cells that a virus can infect

Endocytosis

entire virus is engulfed and
enclosed in a vacuole or vesicle (Penetration/Uncoating)

Fusion

envelope merges directly with
membrane resulting in nucleocapsid’s
entry into cytoplasm (Penetration/Uncoating)

DNA viruses generally are replicated and
assembled in the

nucleus

RNA viruses generally are replicated and
assembled in the

cytoplasm

Budding/Exocytosis (Release 6/6)

nucleocapsid binds to membrane
which pinches off and sheds the
viruses gradually; cell is not
immediately destroyed

Lysis (Release 6/6)

nonenveloped and
complex viruses released when
cell dies and ruptures

Cytopathic effects

Virus-induced damage to host cells that alters the cell, i.e., becoming a cancer cell, a misshapen cell, inclusion bodies, altered DNA, cell lysis, cells clumping together, and evidence left in the cytoplasm

Persistent infections

When cell harbors the virus but doesn’t lysis immediately

Chronic late state

are persistent infections

Transformed cells

Cells that have abnormal behavior via viral infections that can cause cancer, uncontrolled growth, alters in chromosomes, etc.

Oncoviruses

Mammalian viruses that are able to induce tumor growth

Method for growing viruses

Cell culture (For observation and effects of cytopathic effects) bird embryo (Ideal for virus growth), and live animal inoculation (Only when necessary)

Prions

Misfolded proteins, infectious particles that contain no nucleic acid, attacks the nervous system, hard to get rid of

Scrapie

Prions in sheep/goats

Bovine epongiform encephalopathies (Mad cow disease)

Prions in cows

Wasting disease

Prions in elk

Creutzfeldt-Jakob
Syndrome

Prions in humans

Characteristics of viruses are

Rashes, fever, muscle aches, discomfort, and involves the respiratory system and lymph nodes

Porxviruses

Enveloped DNA virus, produce eruptive skin pustules (pocks or pox) that leaves scars, loves skin and connective tissues

Smallpox

First disease eradicated via vaccinations, spreads by skin contact/inhalation, causes fever/rashes

Variola major smallpox

Highly virulent, caused toxemia, shock, and causes blood to clot in the body (deadly)

Variola minor smallpox

Less virulent smallpox

Smallpox Vaccination

Single drop of vaccinia virus
punctured into the skin with a double-pronged needle

Humans can get poxviruses such as

cowpox and monkeypox

Herpesvirus

Enveloped DNA viruses that show latency and recurrent infection lives in sensory neurons of the immune system

Herpes Simplex Virus 1

Most common herpes virus, leaves cold sore and blisters around the mouth

Herpes Simplex Virus 2

Sexually transmitted herpes that leaves lesions on the genitals, can spread without visible lesions

Herpes labialis

Most common symptom, fever blister or cold sore

Herpetic gingivostomatitis

Inflammation in the oral cavity, gums, tongue, and lips

Herpetic keratitis

Inflammation of the eye, the virus travels to the optic nerve rather than the mandibular nerves

Herpetic whitlow (complication)

When Herpes penetrates the skin and causes a localized infection, usually on one finger, extremely painful and itchy

Herpes Simplex Virus 1 encephalitis

When Herpes cause inflammation of the brain (deadly)

Herpes Simplex Virus Treatment

Over the counter medication

Varicella-Zoster Virus

The highly contagious virus causes a primary infection, chickenpox (Varicella), and a reactivation infection, shingles (Herpes Zoster), lives in neurons and reactivates in the neurons and goes from spine to skin

Varicella-Zoster Virus Treatment

Live attenuated vaccine (Varivax) for chickenpox and
shingles

Epstein-Barr Virus

Ubiquitous virus; infects lymphoid tissue and salivary glands, spread by infected saliva, causes sore throat and high fever

Burkitt lymphoma

Cancer in cancerous B cells that causes the cheeks and jaw to swells, commonely found in African ancestry

Nasopharyngeal carcinoma

Cancer of the nasopharynx, commonly associated with people of Chinese descent, involving a bleeding nose, blood saliva, etc