1. Microbial Biotechnology
Lecture:4
Microbial Biotechnology

2. Treatment for Viral Disease

3. Vaccines An attenuated virus is a weakened, less vigorous virus
“Attenuate" refers to procedures that weaken an agent of disease (heating)
A vaccine against a viral disease can be made from an attenuated, less virulent strain of the virus
Attenuated virus is capable of stimulating an immune response and creating immunity, but not causing illness

4. Other Viral Treatments
Interferon are naturally occurring proteins made by cells to fight viruses
Genetic altering of viruses (attenuated viruses)
Antiviral drugs (AZT)
Protease inhibitors – prevent capsid formation

5. Antibiotics
Antibiotics can only be used to treat bacterial infections!
Target specific structures on bacteria to kill them.
First made from a fungus (penicillin), now most are made artificially.
Unfortunately, antibiotic resistance (where the antibiotic doesn’t kill the target bacteria anymore) is becoming a major problem.

6. Antivirals
Antivirals can only be used to treat certain viral infections! Does not “kill” or disarm the virus permanently; only shortens symptoms by 1-2 days. Usually only prescribed to patients with life threatening symptoms or those that have a greater chance of developing complications (because of their age or they have a high-risk medical condition). Just like antibiotics, there is evidence of antiviral resistance too!

7. Influenza A virus Properties of the virus Myxovirus
Enveloped virus with a segmented RNA genome
Infects a wide range of animals other than humans
Undergoes extensive antigenic variation
Major cause of respiratory infections
Influenza A virus is the second acute infection to be discussed.
Myxovirus
Enveloped virus with a segmented RNA genome
Infects a wide range of animals other than humans
Undergoes extensive antigenic variation
Major cause of respiratory infections

8. Influenza A virus Infection
Spread by respiratory route
Virus infects cells of the respiratory tract
Destruction of respiratory epithelium
Secondary bacterial infections

9. Spread of influenza virus
Respiratory aerosoles can be generated from the respiratory tract by various means – from speaking to sneezing.
During a sneeze, millions of tiny droplets of water and mucus are expelled at about 200 miles per hour (100 metres per second). The droplets initially are about micrometres diameter, but they dry rapidly to droplet nuclei of 1-4 micrometres, containing virus particles or bacteria. This is a major means of transmission of several diseases of humans.

10. Respiratory Tract
There are various means by which the host is protected from infection by influenza virus.
The droplets containg the virus may be filtered by fines hairs and cilia in the nasal cavity.
Muco-cilliary cells lining the trachea can trap virus particles and sweep the virus to the back of the throat from where it is swallowed and excreted via the intestinal tract.
Alveolar macrophages can engulf the virus if it enteres as far as the lower reaches of the lung and alveolar sac.

11. Nucleic acid replication Virus protein processing Virus maturation
Antiviral Targets
Attachment/Entry
Nucleic acid replication
Virus protein processing
Virus maturation
Attachment/Entry
Picornaviruses
Nucleic acid replication
Human immunoideficiency virus (AZT)
Herpes simplex virus (Acyclovir)
Virus protein processing
HIV (Protease inhbitors)
Virus maturation
Influenza A virus (Neuraminidase blockers)
Problems of antivruals
Dificuly in finding a virus specific site against which to direct the antivrial
As with the use of antiiotics – resistant mutant scan be readily generated that are resistant to antiirals – this is particuarly a problem with those against HIV where the drug has to be used for prolonged periods of time.