Vaccines which are used to induce immune response against bacteria are called Bacterial vaccines. It is prepared from bacteria or their products.
TYPES –
- Live attenuated vaccine
- Kill bacterial vaccine
- Purified protein vaccine
- Toxoid vaccine
- Capsular polysaccharides vaccine
Live attenuated vaccine:Contain Live attenuated bacteria, lose pathogenicity, and retain immunogenicity.
Example: Tularemiavaccine, Typhoid vaccine.
Kill bacterial vaccine:Contain Killed bacteria.
Example: Vibrio cholera vaccine
Purified protein vaccine:Contain purified protein derivatives.
Example: A cellular pertuses vaccine
Toxoid vaccine: Contain inactivated toxin, lose toxogenicity and retain antigenicity.
Example: Tetanus toxoid
Capsular polysacharidesvaccine:Contain capsular polyscharides Ag as immunogen. Can conjugate with carrier to enhance immune response.
Example: S. pneumonia and H. influenza vaccine
Bacterial vaccines generally recommended for children (0-6 years):
Dtap (Diphtheria, Tetanus toxoid a cellular Pedusess) vaccine
H.influenza type b (Hlb) vaccine
Meningococcal vaccine
Pneumonococcal vaccine.
GENERAL METHOD OF PREPARATION ON BACTERIAL VACCINES
Manufacturing begins with small amounts of a specific Bacteria (seed). Bacteria used in manufacture shall be derived from a Seed Lot System. The Bacteria must be free of impurities, including othersimilar bacteria and even variations of the same type of Bacteria.
Characteristics of The Bacteria Seed Used
The seed shall pass the tests for sterility and shall have freedom from a mycoplasma.
A record of the origin, passage history (including purification” ‘and characterisation procedures) and storage conditions should be maintained for each Seed Lot.
The seed must be kept under "ideal" conditions, usually frozen, that prevent the bacteria from becoming either stronger or weaker than desired.
DIFFERENT STEPS IN VACCINE PRODUCTION:
Upstream processing-
- Selecting the Seed Strain Used for Vaccine Production
- Standardizing the Seed Strains for Vaccine Production
- Growing the Microorganisms
- Harvesting & Purification of Microorganism
- Inactivation and Splitting of Organism
- Formulation of Vaccine
- Quality Control and Lot Release
- SELECTING THE SEED STRAIN USED FOR VACCINE PRODUCTION
The choice of strain depends on a number of factors including the efficacy of the resulting vaccine, and its secondary effects. If possible, the bacterial strain or cell line should be obtained from a recognized culture collection with an established and documented provenance.
Alternatively, if the chosen vaccine strain is an “in house” clinical isolate, it will be necessary to compile a complete history of the strain, including details of its isolation, identification, and maintenance for product registration.
- STANDARDIZING THE SEED STRAINS FOR VACCINE PRODUCTION
Once the candidate seed strains for vaccine production have been prepared, their antigens undergo identity testings and to evaluate their suitability for vaccine production.
This includes satisfactory yields when grown in embryonated ' d. eggs/ cell culture and antigenic stability throughout serial passage in eggs as well as the inactivation and purification.
- GROWING THE MICROORGANISMS
Once the production strain for each vaccine component has been selected, bulk vaccine production can begin. Bulk production begins with the cultivation of the Bacteria in a fermenter equipped with numerous process parameters to control temperature, pH, dissolved oxygen, and other factors.
Bacteria is grown in bioreactors by using the following techniques
i)Batch culture
The steps involved in batch culture are:
a) The micro-organism are grown in a closed vessel.
b) All the raw materials are put in the fermenter at the start and then the micro-organism is added.
c) The system is then left for a long time possibly a week until all the raw materials have been used up and there is loads of the product.
d) The fermenter is then emptied, and other processes are used to separate the product from the micro-organism.
ii)Continuous culture
The steps involved in continuous culture are:
a) The micro-organism is grown in an open system.
b) Continuous culture aims to keep a culture growing indefinitely. This can be done if fresh nutrients are continually supplied.
c) Accumulated cells and waste products are removed at the same rate
d) Conditions such as temperature and pH are kept at their optimum values.
e) Here the raw materials are trickled in at the top of a column in which there are immobilised microorganisms.
f) The product flows out the bottom in a pure state.
However, this process can only be used for reactions that are fast possibly taking 10 minutes.
- HARVESTING & PURIFICATION OF MICROORGANISM
After propagation, the bacteria is harvested. Harvesting of bacteria is largely a manual process that requires extracting infected cells, breaking down cell walls, and then collecting the bacteria.
After treatment of the infected cell line, the bacteria is released into the supernatant, and the cellular debris is centrifuged away by use of appropriate Centrifugation method.
Purification selectively separates and retains the desired product at the highest purity per its predetermined specification. (Remove unwanted compounds)
i)Centrifugation
Centrifugation is a process by which solid particles are sedimented and separated from a liquid using centrifugal force as a driving force.
Centrifugation is used to separation and purification of pathogenic bacteria antigens and other agents used in the production of vaccine. Centrifugation is also used to remove dead cells, cell debris etc.
ii)Chromatography
A group of physical separation techniques, which are. characterized by the separation of mixtures due to differences in the distribution coefficient of sample components between two phases, one stationary and the other mobile phase.
iii)Filtration
Filtration is a process for separating two substances of two different physical states. It is used for separating solids from turbid liquids (filtrate), pure gases or solids. Separation of panicles from liquid by applying a pressure to the solution to force the
solution through a filter.
- INACTIVATION AND SPLITTING OF ORGANISM
The baclerialcell suspension is inactivated by two different methods:
a. Heat: Low temperatures are essential to avoid damage to the antigens.The usual treatment is 56 0C for one hr. As this exposure cannot kill all contaminnling organisms particularly Spores, strict asepsis is necessary throughout manufacture.
b. Chemicals: The organisms are killed chemically when heat treatment affects antigenechy (e.g-Plngue vaccine). Chemical methods are the alternative to the heat method.
Examples:
i.05% of formalin for plague and pertussis.
ii.Phenol for cholera.
iii. Thiomersol for pertussis.
iv.75% of alcohol for TAB and TABC.
- FORMULATION OF VACCINE
The standardized cell suspension is formulated into final vaccine by incorporating some other substances include acidity regulators like sodium or potassium phosphate, preservatives to avoid contamination in multi dose vaccines thiomersol is the commonly used preservative and rarely formaldehyde or Phenol derivatives are also used.
Stabilizers are used to help the vaccine maintain its effectiveness during storage. Eg., MgC12, MgSO4, Lactose sorbitol and sorbitol gelatin.
- QUALITY CONTROL AND LOT RELEASE
a. Quality Control Tests
| Test | Purpose of test |
| Sterility | Demonstrates that no live microorganisms are present in product. |
| Safety | Demonstrates that overdose of the product causes no harm. |
| Residual toxicity | Demonstrates that the product contains no material that can cause harm |
| Efficacy | Demonstrates that each antigen in the product meets the recommended guideline level in internationally recognised tests. |
| Increase in virulence | With live vaccines, there is concern that the organism might be shed from the host and transmitted to contact animals, causing disease if it retains residual virulence or reverts to virulence. All live vaccines should be tested for virulence by means of passage studies. |
| Interference tests | For products with two or more antigenic components, tests must confirm that there is no interference between individual components, that is, one component causing a decrease in the protective immunological response to another component. |
b. Lot Release
BATCH/SERIAL RELEASE F OR DISTRIBUTION: Prior to release, the manufacturer must test each batch/serial for purity, safety, and potency.
I. Batch purity test:
Purity is determined by testing for a variety of contaminants. Tests to detect contaminants are performed on master seeds, primary cells, MCSs (Master cell stock), and each batch of final product prior to release.
II. Batch safety test:
Batches are considered satisfactory if local and systemic reactions to vaccination with the batch to be released in line with those described in the registration dossier and product literature.
III. Batch potency test:
Batch/serial potency tests, required for each batch prior to release, are designed to correlate with the host animal vaccination-challenge efficacy studies.
Sampling:
Samples should be selected from each batch/serial of product. The selector should pick representative sampler.
Filling Packaging and Labelling:
Once all procedures of vaccine production are completed, the vaccine is blended, filled the doses into vials and packaged. Which are then sealed carefully inspected before labels are applied to show the vaccine batch lot numbers, and expiration date.
Standards for labelling products will vary from country to country.
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