Viral Structure, Lifecycles, HIV, and the Immune System

I. Virus- segment of DNA or RNA wrapped in a protein coat

A. Characteristics 1. Non-cellular (i.e. not a cell) 2. They do not use energy (They don not carry on respiration or photosynthesis) 3. No organelles 4. They Reproduce within cells; but not directly with other viruses 5. They do not grow in size 6. Contain nucleic acids and proteins 7. Have limited enzyme activity

B. Structure

C. Lytic CycleLytic Cycle

1. Attachment- The virus attaches to a specific area (receptor site) on a specific cell

2. Entry- the viral nucleic acid is then injected into the host cell.

3. Replication- host DNA is destroyed. Viral nucleic acid is replicated. Viral components are manufactured

4. Assembly- viral components are assembled into mature viruses.

5. Release - Host cell lyses (splits open). This releases as many as 300 new viruses.

D. Lysogenic Cycle- (another virus life cycle). However, lysis is delayed and the viral DNA is integrated with the host DNA forming a provirus.

Lysogenic Cycle 1.Attachment and entrance are the same as in the lytic cycle. 2.Provirus Formation- viral DNA attaches to the host cell’s DNA forming a new combination of DNA known as a provirus. A provirus is latent. (I.e. it does not attack immediately) 3.Cell Division- cell undergoes normal asexual reproduction with replication of both the host and viral DNA. 4.Activation- the provirus leaves the host DNA and reverts back to the lytic cycle

E. AIDS- Acquired Immune Deficiency SyndromeAIDS

1. HIV Transmission A)Sexual Contact (Semen & vaginal secretions) B)I.V. Drug Use (Direct contact with blood) C)Mother to Baby (Across placenta, Breast milk)

2. Disease Progression a)Well- Disease is in lysogenic cycle, spreading through budding and replication b)PGL- persistent generalized lymphoma. Continuously swollen glands indicate infection c)ARC- Aids related complex. Weight loss, fatigue, sweats, gastrointestinal difficulties, thrush, shingles and other small infections d)AIDS- first pneumonia, discoloration of the skin, brain damage. Immune system shut down

3. Treatment a)Antibiotics- help fight against opportunistic infectious agents b)CSF, IL-1,IL-2: increase number of white blood cells and bolsters the immune system c)Antivirals- (AZT, Acyclovir, Interferon, Protease inhibitors) Fight viral replication directly

The Body’s Defense Against Disease Unleashing the Fury of the Immune System Macrophage engulfing bacteria Cytotoxic T-Cell killing a cancer cell

1. Skin & Mucus Membrane is the body’s first line of defense against disease. It prevents most germs from entering the body. Openings are protected a)Mouth- contains digestive enzymes b)Nose- contains hair and mucus c)Ears- has hair and wax d)Vagina- contains a mild acid

2. The Body’s second line of defense is Macrophages and Neutrophils a) White blood cells detect foreign protein patterns on germs called antigens b) It then engulfs the germ through a process called phagocytosis

a) Macrophages ingest the antigens and display then on their surface 3. The body’s third line of Defense is AntibodiesAntibodies

The macrophage is now an Antigen Presenting Cell Antigen Presenting Cell b) T-Cells bind to the APC (antigen presenting cell) and release chemicals. The chemical activates a specific B cell

C)B-Cells activate and divide forming Memory cells and Plasma Cells D)Plasma Cells secrete antibodies that bind to the antigen and immobilize it Antibodies Memory Cell

One Way Antibodies Work Neutralization -block viral and bacterial binding sites

E) Memory Cells persist after the infection and provide immunity 1 st Exposure to A2nd Exposure to A

4. Vaccines contain dead or weakened germs and cause an immune response which produces immunity without disease

5. T-Cells also activate cytotoxic T-cells (T-Killers) which attack germs directly