Micro J210 Virology 1

• -discovered in 1898
• -Visualized only after discover of electron microscope in 1930
• -A virus particle is also called a virion
• -smaller than bacteria

• -Their simple, very small, acellular
• -The presence of either DNA or RNA, not both, in the same viral particle
• -Their inability to reproduce independently of living, 2-50 genes.

• -DNA or RNA and protein capsid which surrounds the nucleic acid
• -Combo of nucleic acid and capsid is called a nucleocapsid

• -If it only has a protein capsid, it is naked
• -The subunits are call capsomeres and the entire protein coat is called the capsid

• -Membrane derived from host cell
• -in the envelope are viral proteins.
• -Enveloped viruses are not very stable since envelope is it is a membrane.
• -The envelope has protein and carbs, some from the host.

• -Capsid
• -Nucleic acid
• -Capsomere
• -Nucleocapsid
• -Virion

• -Capsid
• -Nucleic acid
• -Capsomere
• -Nucleocapsid
• -Virion
• -Envelope
• -Spike (envelope glycoproteins)

• -DNA or RNA
• -Single or Double stranded

• -Icosahedral (hexagonal, most common)
• -Helical (spiral staircase-shaped)

• -Viruses make separate parts within the host cell they are infecting and then assemble into many viral particles
• -1 Human virus (12-72) = 100,00 virions

• -Animal: Influenze
• -Plant: Tobacco mosaic virus
• -Bacteria viruses: Bacteriophage

• -Viral diseases have been some of the major concern for epidemics in humans. (Polio, rabies, smallpox, yellow fever)
• -Leading cause of all human disease (Common acute respiratory, GI, Ebola, AIDS, Hepatitis C, Hantaviruses, SARS)
• -Can be useful for gene therapy

-Measles, Mumps, Chicken pox (shingles, reactivation of diseases), small pox.

• - Visible effects on the patient
• 1. Direct damage of virus to cells, make cells different
• 2. Host defense mechanisms (immunocytopathology) Sickness caused by immune system working

• -Cell death
• -Giant Cell formation, Syncytia
• -Rounding up of cells
• -Pilling up of cells
• -Inclusion boides inside the cells

• -CPE, cytopathic effect
• -Lysis of host cell, viral plaques, bacteriophage
• -Plaque assay of bacteriophage

• -CPE, cytopathic effect
• -Syncytia, when cells fuse together to form large cells with many nuclei
• -Sticks to the T cells so they cannot kill anymore

• -III of viral CPE.
• -Rounded up as result of infection

• -CPE IV, Transformation, focus formation, wart
• -Warts are small, painless growth
• -Raised round or oval growth on the skin
• -No discomfort unless in a bad area, goes away on their own within two years
• -Venereal warts can cause cancer

• -CPE V
• -Visible by EM
• -Lesion inside the cell

• 1. Attachment
• 2. Penetration
• 3. Uncoating
• 4. Replication of Nucleic acids
• 5. Protein synthesis
• 6. Assembly
• 7. Release

• -1 step in life cycle
• -Lock and key, matching part
• -Attachment proteins, specific surface proteins for each virus
• -Cell specific-receptors

• -Life cycle step 2, follows attachment
• -Same step in bacteriophage with uncoating
• 1. Endocytosis-Whole virus goes in and then the capsule is released
• 2. Membrane fusion- just capsule is released

• Step 3 of life cycle
• -Removal of membrane and capsid proteins, usually carried out by cellular enzymes that chew off the viral coat by lysosome function

• -Step 4 of the life cycle
• -DNA virus: nucleus, 1-2 viral and many cellular enzymes
• -RNA virus: cytoplasm, always uses viral coded enzymes

• -Step 5 of life cycle
• -Cytoplasm, both viruses use cellular ribosomes and the rest of the host cell protein synthetic machinery

• -Step 6 of life cycle
• -Nucleic acid and capsid proteins come together and undergo self assembly which is a spontaneous process

• -Final step of life cycle
• -Lysis of cell, naked virus
• -Budding: enveloped virus: reverse process of membrane fusion. The virus acquires the membrane from the host cell but the membrane always contains viral protein that are required for specific attachment.

• -Skin: HPV, Warts
• -Respiratory tract: Rhinovirus, common cold
• -GI tract: Rotavirus, diarrhea
• -Eye: Adenovirus, conjunctivitis
• -Genitourinary tract: Herpes virus, genital herpes
• -Direct entry: West nile, Hep B, Rubella, HIV

• -Spread of virus throughout the body-viremia-target organ
• 1. Local replication at the site of entry, grow into large number
• 2. Spread into blood, viremia
• 3. Dissemination throughout the body-now any susceptible organ may be infected, can go in the lymphatic system to spread
• 4. Disease: Symptoms are usually seen in cells of only the target organ. Observable clinical symptoms

-After exposure to the virus, asymptomatic until the virus reaches the target organ and cause symptoms, and this is called the incubation time (period) of the virus.

-The amount of time between infection with a virus or bacteria to beginnings of the symptoms

• -Distance between the site of infection and target organ. Short: 2 days for Flu, respiratory tract is both. Long: Weeks to months for rabies virus.
• -Growth rate of the virus. Fast: 1 to 2 for flu. Slow: weeks to months for papillomavirus for warts

• -Host defense
• -Innate
• -Alpha: PMNS and macrophages
• -Beta: produced by Fibroblasts
• -Gama: produced by CD4 T cells
• -Cellular protein
• -Can work by warning neighboring cells
• -Antiviral states in the neighboring cells: Degrades RNA, inhibit protein synthesis

• -Host defense
• -Neutralizing antibodies
• -Opsonization
• -Complement fixation

• -Host defense
• -render virus harmless, coats virus particle, inhibit attachment, if partial binding-no penetration, attachment. Aggregation-reduction in virus infectivity

• -Host defense
• -Enhancement of phagocytosis
• -Antibodies with virus attach to PMNs which kill the virus
• -Nk cells kill antibody coated viral particles by process of antibody dependent cellular cytotoxicity (ADCC)

• -Host defense
• -Activation of complement cascade
• -Component of complement C3 is an opsonin
• -Viral proteins present in infected cell membrane or viral envelope can by lysed by C6, 7, 8, which form the MAC attack
• -ONLY enveloped viruses

• -Cellular response, these cells act on virus infected cells, not directly on virus.
• -CD4 T cell: They recognize the new viral antigens, proliferate and produce cytokines that activate B cells to release neutralizing antiviral antibodies
• -Activate T killer cells.

• -WHO started in 1967 to eradicate smallpox from the earth, gone by 1977.
• -Last naturally occurring in 1977, somalia.
• -National stockpile of vaccine in case of bioterrorism.

• -Being tested
• -Get into patient cells and express the gene produce

• -Live attenuated, vaccinia
• -Killed- Flu
• -Sub- viral component: Hep B, Recombinant

• 1. Herpes Viruses
• 2. Adenovirus: Conjunctivitis, diarrhea
• 3. Paravovirus: Pox virus
• 4. HPV, warts