Week 4

Viral Components

Contains genetic code (DNA or RNA)

Can recognize cells via proteins and receptors

Undergo evolution

Cannot reproduce on its ow needs a host, are nonliving, cannot be seen under the microscope

Different types of Viral Structures

Genetic material with protein shell (naked)

Genetic material with protein shell and lipid bilayer around it (enveloped)

Helical- capsomer makes hollow tube containing the genetic virus (plants)

Polyhedral- animals

Spherical- enveloped, influenza

Complex- bacteriophages

How viruses are classified

Based on capsid structure, chemical composition, genome type

DNA virus

Double stranded:

Enveloped- HSV, Pox

Naked- Adeno, Papiloma

Single stranded:

Naked- parvovirus

RNA virus

+RNA enveloped and unenveloped directly into protein

-RNA enveloped, cannot be translated without complementary strand

-±RNA double stranded

+RNA via DNA enveloped, retrovirus, has to be translated into DNA before virus replication

6 Order of Steps of animal virus replication

1. Adsorption: the virus particle leaves the host cell. Protein on the viral surface and the protein on the hot cell surface physically interact causing the determination of what type of host a virus can infect and where it can infect

2. Penetration:(Either through Fusion or Endocytosis)

3. Uncoating: The viral genome needs to be released from the capsid, envelope, and vesicle. When the genome is released the capsid will fall apart and RNA is released in the cytoplasm

4. Synthesis: viral genome goes through replication, creating more copies of viral genome. Copies of mRNA are used to start the production of new capsomers and surface proteins. Synthesizing new components that are massed produced.

5. Assembly: as the new components are being made they start to assemble making new viral particles. Capsomers then form around the new copy of the genome. The enveloped spiked protein virus are sent to the cell membrane and host cell

6. Enveloped viruses bud off the membrane ready to infect another cell. This step is called release. (Budding, exocytosis, and lysis)

2 Types of Viral Entry

1. Fusion- the phospholipid bilayer interacts with the host cell that has protein interactions allowing the envelope of the virus to get close enough to envelope of the host cell and fuse them together. Now the capsid can enter the cytoplasm of the host cell and the viral envelope gets stuck and left behind on the cell membrane of the host cell.

2. Endocytosis interacts with naked viruses and enveloped. This causes the cell to wrap its membrane around the virus creating a vesicle

3 different types of Viral Release

1. Budding- the newly made virus pushes against the cell membrane causing the flexible phospholipid bilayer to surround the viral particle. This virus continues to opus outward until it pinches itself off and fuses together creating an enveloped sphere

2. Exocytosis- newly made virus goes into the vesicle and then towards the cells surface. The virus is then embedded into arts of the neoplasm if reticulum then transferred into the Golgi body. New copies are made through the Golgi body so at the end of the assembly step the new virus will be within the vesicle. The vesicle then goes to the surface of the host cell Enveloped viruses, fuses to the membrane, and then released.

3. Lysis: virus breaks apart the cell membrane so that the cytoplasm spills out releasing the viral particle, killing the host cell.

4 types of Viral infections

1. Acute Infection: rapid viral production and development of signs and symptoms (influenza)

2. Latent infection: virus genome hides out in the body for a time, not active not showing signs/ symptoms, but when triggered the virus goes into a round of replication. This can alternate from an active to latent infection and back and forth (herpes)

3. Chronic Infection- body releases virus at a slower rate making it less abundant ad hard to detect ( Hep B or C)

4. Malignant Infection- virus integrates its genome to our genome and causes a disrupt in regulation of cell growth. Viral infections can turn cancerous.

Latent and Chronic infection are the most persistent because they are able to stay in the body for long periods of time and infect

Plaque

“Spots” absence of bacterial cells because of the lack of host cells from an active viral replication

3 methods of viral propagation

1. Lawns create a lawn of bacteria on an agar plate, then incubate, ad observe the grown bacteria

2. Bird Embryos- when trying to propagate a mass produced virus, the shell protect against contamination, has lists of nutrients and cells propagate a virus

3. Animals- cultivate into vivo some viruses cannot propagate properly with out a host. So animals are used to propagate a virus

3 methods of viral detection

1. Use an agar plate and infect it with cell culture and look for plaques

2. Screening for parts of the virus: Molecular test - looks for gene that is unique in that virus for DNA or RNA, Rapid test- at home test (covid-19) detects viral protein uses antibodies to bind to viral antigens

3. Screen for immune response: if. In a serological test is positive it leant mean you have the virus currently but it could mean you’ve had it in the past so the antibodies present in your blood stream. If you have antibodies in the blood stream that binds to the virus, you have the virus

Interpret results of “rapid antigen’ test data

The reporter antibodies with the dye binds to the antigen that is being tested

In the control line antibodies will grab the receptor antibodies to tell that the test hasn’t been contaminated

The test line binds to the antigen, but by the time these antigens get to the test line, they are also bonded by the receptor antibodies concentrating the, together to make the line appear.