B6: Preventing and Treating Disease

What is a vaccine

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body. This stimulates some white blood cells to produce antibodies and others to become memory cells. If the same pathogen enters the body again, the white blood cells (memory cells) respond quickly to produce the correct antibodies. These kill the pathogen before it can cause any symptoms.

How does Vaccination prevent disease

If the body is re-infected with the pathogen, the memory cells recognise the antigens. The white blood cells are able to produce antibodies more quickly this time. The pathogen is destroyed before it has the chance to make you feel ill.

Herd Immunity

When a large portion of a community (the herd) becomes immune to a disease.

Antigen

Proteins on the surface of cells. They can help to determine between self/non self.

Antibodies

Drugs that kill bacteria. Proteins made by plasma cells to destroy unrecognised antigens.

Bactericidal and Bacteriostatic Antibiotics

Bactericidal antibiotics kill bacteria.

Bacteriostatic antibiotics inhibit protein synthesis so bacteria cannot grow or multiply.

Causes of Antibiotic Resistance

Not finishing your course. Not taking a high enough dose. Not taking antibiotics specific to the bacteria causing the illness. Taking antibiotics to treat illness caused by viruses. Use of antibiotics preventatively in farming.

Stages of Antibiotic Resistance

Normal S.Aureus are a common bacteria

A mutation occurs that makes one bacterium reistsant to the antibiotic methicillin

Initially the mutation has no real advantage

If methicillin is used, the unadapted bacteria die and the resistant bacteria have the advantage and survive.

The methicillin resistant bacteria reproduce and pass the resistance off to their offspring, becoming the dominant species.

Antibiotic medical use

Kill bacteria

Difference between antibiotic and antiseptic

Antibiotics only kill bacteria. Antiseptics kill pathogens, but only on surfaces.

Why is it difficult to develop medicine against viruses?

They hide in cells, so the whole cell must be killed.

Traditional source of medical drugs

Penicillin - Antibiotic - Penicillium mould

Asprin - Painkiller - Willow

Digitalis - Heart Disease - Foxglove

Efficacy

Does the drug work to kill pathogens/reduce symptoms/prevent disease?

Toxicity

Is it safe? It shouldnt kill cells or cause other serious side effects

Dose

How much should be used and for how long?

Stable

It must be possible to store any new drug for a period of time

Stages of drug trials

Preclinical: Cells - Efficacy, Toxicity

Preclinical: Tissues - Efficacy, Toxicity

Preclinical: Live Animals - Efficacy, Dose, Toxicity

Clinical: Healthy volunteers - Toxicity, Side Effects

Clinical: Patients - Efficacy, Dose, Toxicity

Double Blind Trials

A trial where neither the doctor not the patient know who has been given a drug or a placebo (fake). Avoids unconscious bias.

Monoclonal Antibody

Antibodies produced in a lab outside of the body, from a clone of cells derived from a single B lymphocyte cell. Only recognise one antigen. They need to produce specific monoclonal antibodies, and to be able to divide quickly.

Stages of making Monoclonal Antibodies

A lymphocyte (makes specific antibodies) and a tumour cell (divides rapidly) are combined to make a hybridoma, which can both make specific antibodies and divide rapidly.

The hybridoma divides rapidly by mitosis

The cloned cells make specific monoclonal antibodies which are collected and then purified.

Uses of monoclonal antibodies

For diagnosis (such as pregnancy tests)

In laboratories to measure the levels of hormones and other chemicals in blood, or to detect pathogens.

In research to locate or identify specific molecules in a cell or tissue by binding them with a fluorescent dye

To treat some diseases, eg. cancer.

Advantages of monoclonal antibodies

They only bind to the specific diseased or damaged cells

Healthy cells are not affected

Will become cheaper

Could carry specific drugs to target cells

Avoids use of more destructive treatments such as radiotherapy

Disadvantages of monoclonal antibodies

More side effects than expected

Expensive

Triggered an immune response in humans

Humans may react against the antibodies because they are made by mouse cells.

Not yet widely used.

Monoclonal Antibodies in Pregnancy Tests

Pregnancy test kits use monoclonal antibodies. These have been designed to bind with a hormone called HCG which is found only in the urine of pregnant women. Monoclonal antibodies are attached to the end of a pregnancy test stick onto which a woman urinates. If she is pregnant, HCG will be present in her urine and will bind to the monoclonal antibodies on the test stick. This will cause a change in colour or pattern which will indicate pregnancy. These specific monoclonal antibodies in the pregnancy test will only bind with HCG.

Monoclonal Antibodies Treating Cancer

They can trigger the immune system by making cancer cells more noticeable

Bind to receptors on cancer cells, removing the stimulus to grow and divide

Carry drugs or radioactive therapies to cancer cells to destroy them

Who discovered penicillium mould

Alexander Fleming

What are monoclonal antibodies produced from?

Mouse cells

What has to happen before drug testing results can be published?

Peer review.

Clinical Trials on Volunteers

All volunteers must be healthy.

Very low doses are given at the start of the trial. If the drug is found to be safe, further clinical trials are carried out to find the optimum dose.