Immunostimulants

What is Immunostimulants?

·         Immunostimulants are the substances that increases the ability of the immune system to fight against infectious & disease.

Types of Immunostimulants

1.      Specific Immunostimulants

2.      Non-specific Immunostimulants

Specific Immunostimulants

·         Provide antigenic specificity in immune response such as vaccination.

·         E.g.: Vaccine.

Non-specific Immunostimulants

·         These act irrespective of antigen specificity, so act against all antigens.

·         E.g.: Immunoglobulins

Functions of Immunostimulants

·         It activates the immune system of human and animals.

·         Develops immune system factors like phagocytosis, properdin, complement systems, protective secretory IgA antibodies, α- and γ-interferon release, T- and B-lymphocytes, synthesis of specific antibodies and cytokines, and synthesis of pulmonary surfactant.

·         The reasons of affect the immune system

o   Antibiotic resistance of the bacteria

o   Allergic reactions to antibiotics

o   Immunosuppressive effects of antibiotics

o   Poor effects of the antibiotics in viral infections

 Classification of Immunostimulants

1.      Vaccines

2.      Adjuvants

3.      Immunoglobulins

4.      Miscellaneous agents

·         Levamisole

·         Thalidomide

·         Isoprinosine

·         Immunocynin

VACCINE

BCG vaccine

• It is freeze dried preparation containing live culture of the bacillus of calmette and Guerin strain of Mycobacterium tuberculosis.

Preparation

• The bacilli are grown on a suitable culture media until 1mg when plated out on suitable solid culture media, it shows not less than 20 million colonies.
• The growth period should not be more than 14 days in any case.
• After a suitable growth, they are separated by filtration in the form of a cake.
• The cake is homogenised in a grinding flask and suspended in a suitable sterile liquid medium. (to preserve the antigenicity and viability of the vaccine)
• The suspension is transferred into the final sterile containers and freeze dried.
• Then the containers are sealed so as to prevent contamination or deterioration of the vaccine.

Uses

• Used as an immunising agent which protection against tuberculosis.

Dose

• Prophylactic, 0.1 ml as a single dose by intra-cutaneous injection.

Cholera Vaccine

• Cholera vaccine is colourless, whitish or slightly coloured opalescent liquid.
• It is a sterile suspension of killed cholera vibrios (Vibrio cholerae) of a strain selected for high antigenic property and purity.

Preparation

• It is prepared from equal portions of suspensions of Cholera vibrio of Vibrio cholerae Inaba and Ogawa strains selected for high antigenic efficiency. Either a single strain or several strains of each type may be used.
• Each strain of cholera vibrios is grown separately on a solid medium for 24 to 48 hours.
• Bacteria are then washed with normal saline solution.
• The suspension of bacteria thus obtained is killed either by heating at 56⁰C for one hour or adding alcohol or other bactericide, such as, phenol or formaldehyde.
• All precautions must be taken to ensure that the antigenic property of the preparation is not destroyed.
• The preparation is then standardised so that 1ml of vaccine contains not less than 12,000 million bacteria.
• After adding a suitable preservative, it is transfer into final containers and then sealed.
• The vaccine must comply with the tests for sterility and also the test for undue toxicity of vaccine.

Uses

• It is used for immunisation against cholera. But it has a limited use as it has only about 50% effectiveness for a period of 3 to 6 month. The vaccine does not prevent transmission of the disease.

Dose

• Prophylactic, initial dose 0.5 ml; second dose, 1 ml after an interval of 4 to 6 weeks.

Pertussis vaccine (whooping cough vaccine)

• It is more or less turbid, whitish liquid nearly dourless or having faint odour due to antimicrobial agent.
• Pertussis vaccine is a sterile bacterial suspension of killed pertussis bacilli (Bordetella pertussis) of a strain or strains selected for high antigenic efficiency.

Preparation

• It is prepared by culturing Bordetella pertussis in a suitable culture media.
• It is separated, washed and suspended in normal saline solution.
• The bacteria are killed either by heating or by adding some bactericides.
• The suspension is standardised. The vaccine may show abnormal toxicity in animal tests and this is removed by cold storage for up to three months.

Uses

• For active immunisation of children against whooping cough especially when diphtheria and tetanus toxoids and pertussis vaccine (DPT) cause untoward reaction or it’s contraindicated.

Dose

• It is administered by subcutaneous injection in three doses of 0.5 ml, 1.0 ml and .5 ml at least 4 weeks apart.

Typhoid fever

• Typhoid vaccine is white or creamy white turbid liquid free from clumps.
• It is sterile suspension prepared from one or more strains of Salmonella typhi that are smooth and have the components of O, H and VI antigens.

Preparation

• Salmonella typhi organism are grown on a suitable culture media. The bacteria are killed by heat or by a bactericide such as phenol, formaldehyde or by a chemical such as acetone.
• It is then standardised, so that 1.0 ml of the typhoid vaccine contains not less than 1000 million bacteria (S. typhi).
• The vaccine must comply with the tests for sterility and the test for undue toxicity for vaccine.

Uses

• It is used for immunisation against infection caused by typhoid bacilli.

Dose

• Prophylactic, initial dose 0.5 ml followed by second dose of 1.0 ml by subcutaneous injection after an interval of 4 to 6 weeks.

Smallpox Vaccine

• Small pox vaccine is almost white powder which reconstitutes to yield viscid, straw coloured liquid.
• Smallpox vaccine contains living attenuated vaccinia virus.
• The vaccine is prepared by two methods

1.      By using animals

2.      By using eggs

1. Preparation of smallpox vaccine using animals

• Smallpox vaccine is prepared by using claves or sheep.

Methods of preparation

• Selection of animal free from disease: healthy calves or sheep are used for the production of vaccine. The animals are kept for 10-14 days in an isolated area under observation. They are given through examination to exclude diseases.
• Preparation of animal for scarification: the abdomen and flanks (the side of the body between ribs and ilium) are thoroughly scrubbed, washed and disinfected. The animal is taken to a special room where abdomen and flanks are shaved, scrubbed and then thoroughly disinfected.
• Inoculation: light incisions are made in the cleared skin without drawing blood with the help of scarifier. The scarified area in then rubbed with some of seed vaccine of known potency.
• Incubation: during next 7-9 days pustules or vesicles from along the line of scarification. During the incubation period, every precaution is taken to keep the animal as clean and aseptic as possible.
• Collection of viruses: the animal is taken to the operation table and killed. A post mortem on the animal is made to check the absence of disease not detected otherwise. The abdomen and flanks are then washed with sterile water. The material in the pustules is withdrawn with the help of sharp edged spoon under aseptic condition.
• Purification: the content of the pustules are mixed with equal volume of glycerine, cooled and then finely ground to form homogeneous mixtures. It is then stored for a long time at -10⁰C to remove impurities.

The recent methods of purification are:

                                i.            By using brilliant green

                              ii.            By using trichlorofluro ethan

                            iii.            By adding 0.4% phenol and then incubated at 22⁰C for 2 days.

                            iv.            By treating with a mixture of glycerine and peptone and then store it at -10⁰C.

• Filling, sealing and storage: it is filled into the final container under aseptic conditions and freeze dried. The containers are sealed to exclude the possibility of any contamination.

2. Preparation of smallpox vaccine using eggs

• The eggs of hen are examine and selected for fertility. These eggs are incubated for 12 days. On the following day a small portion of the shell of the egg is removed and the chorio-allantoic membrane is inoculated with seed vaccine of known potency. The portion of the shell is replaced and sealed in position with a little melted paraffin wax. The eggs are incubated for 72 hours.
• Using aseptic precaution the shell s removed and chorio-allantoic membrane is separated. It is placed in sterile saline solution at 0⁰C. Maintain a low temperature, 50% glycerine is added. The material is ground to produce a homogenous suspension. It then transferred into final containers, freeze dried and sealed.

Uses

• Smallpox disease has been eradicated from India, but it prepared in small quantity for the laboratory worker who are likely to have contact with vaccinia virus, and for travellers

Dose

• Prophylaxis: 0.02ml is applied to the skin and inoculated by scarification or pressure.

ADJUVANTS

·         An adjuvant is a substance that increase immune response to foreign antigen.

o   Adjuvants may be added to a vaccine to modify the immune response by boosting it such as to give a higher amount of antibodies and a longer-lasting protection.

o   Adjuvants are also used in the production of antibodies from immunized animals.

o   The most commonly used adjuvants include aluminum hydroxide and paraffin oil.

Aluminum Hydroxide

·         It is a white gelatinous precipitate in aqueous suspension.

·         The mechanism of action includes the formation of a depot at the injection site, which enabling the slow release of antigen and the stimulation of antibody producing plasma cells.

Side Effects

·         Pain at the site of injection.

·         Fever

IMMUNOGLOBULINS

·         Antibody molecule consists of two light and two heavy chains composed of different domains.

·         The Fab fraction serves as the antigen binding site.

·         The specific antigen-binding properties of an IgG molecule are conferred by the three dimensional stearic arrangement inherent in the amino acid sequence of the variable region of the light and the heavy chains of the molecule.

·         This portion of the IgG molecule is called the idiotypic determinant.

·         FC fragment is relatively constant and determines the effectors function of the antibody.

·         The FC domain is necessary for interaction with complement cascade.

Human Normal Immunoglobulin:

·         Roughly plasma protein can be fractionated into four important components, viz. albumin and the alpha, beta and gamma globulins.

·         The Ig obtained from pooled, human, adult blood is known as immune serum, more selective type of a gamma globulin against a particular infection obtained from the blood of individuals, this is called as Hyper Immune Serum or Human Specific Ig.

Adverse Reactions

·         It can cause pain at the site of injection

·         Allergic reactions can occur

·         It may give rise to fever, flushing, shivering joint pain and nausea. Therapeutic Uses:

·         Infective Hepatitis (gamma globulin can suppress the clinical symptoms). The dose of HNI recommended is 750 mg.

Diphtheria

·         Hyper immune specific serum can be used both prophylactically and therapeutically.

Monoclonal antibodies

·         These are the antibodies produced by single clone of B cells, which are now being used for diagnostic procedures and therapeutic purposes.

Mechanism of action

·         They block the characteristic of targeted antigen, its function, and its cell surface and tissue distribution, to produce immune conjugates.

Adverse reactions

·         Hypersensitivity reactions.

·         Activation of inflammatory cells.

Therapeutic uses of mAb

·         Used as immunosuppressant.

·         In auto immune disease.

MISCELLANEOUS AGENTS

LEVAMISOLE

·         It is available as ergamisol or vermisol.

·         First synthesized to treat parasitic worm infections.

·         Used as immuno modulating agent in cancer.

·         It is given orally, which is rapidly absorbed and it crosses BBB.

·         Metabolized in liver and excreted through urine.

·         It restores depressed B and T cells functions.

Mechanism of action:

·         It acts by modulating cell mediated immunity.

·         The ganglia in worms are stimulated causing paralysis and expulsion of live worms, by the activation of macrophages.

Dose

·         It is administered in a dose of 50mg three times a day for 4-6 weeks.

Adverse Effects

·         Nausea

·         Muscle pain

·         Skin rashes

·         Drowsiness

ISOPRINOSINE

·         It is also available as inosine.

·         Useful as immunostimulant in immunodefecient patients.

·         It is antiviral agent.

·         It acts as a immunostimulant, an analog of thymus hormones.

·         It is most commonly used to treat the rare measles complication subacute sclerosing panencephalits.

Mechanism of action

·         Isoprinosine is a synthetic purine derivative with immunomodulatory and anti-viral properties.

·         The action of Isoprinosine:

o   It normalizes the cell-mediated immunity by stimulating the differentiation of T-lymphocytes into T-helper cells, and increasing production.

o   It increases the humoral immune response by stimulating the differentiation of B-lymphocytes into plasma cells and by enhancing antibody production.

o   It inhibits viral growth by suppressing viral RNA synthesis while potentiating depressed lymphocytic action.

Dose

·         Patients with cancer can take 2000 mg to 3000 mg of Isoprinosine daily for two months

Adverse Effects

·         Nausea

·         Headache

·         Vomiting

·         Abdominal pain

·         Dizziness

·         Diarrhoea