Vaccines:
Vaccines are preparations from pathogenic microorganisms that is injected to humans or other animals to induce protective immunity. The vaccine may be prepared from killed or attenuated(living but weakened) microorganisms, inactivated bacterial toxins(toxoids) purified antigenic macro molecules, rDNA proteins. For the first time Edward Jenner and Louis Pasteur developed vaccination against small pox and Rabies diseases respectively now many other vaccines have been developed against epidemic diseases like anthrax, cholera, diphtherea, measles, hepatitis A&B, mumps, polio and whooping cough.
The successful vaccine must be able to stimulate immune responses that are similar to those infect naturally many efforts are being made to produce successful vaccines for many dangerous diseases. Vaccines are classified into 6 types based on the type of materials used for the preparation of vaccines. They are:
a) Whole-organism vaccines: Whole organisms that are killed(inactivated) or attenuated(avirulant live) are known as whole organism vaccines. Many of the common vaccines currently used for the bacterial or viral diseases come under this type that is anthrax vaccine, measles vaccines, polio vaccine, yellow fever vaccine are effective but require several booster doses and they do not stimulate cell mediated immunity and secretory IgA production properly where as attenuated vaccines work effectively in single dose and stimulate both humeral and cell mediated immunity.
b) Purified macro molecular vaccines: The whole organism vaccines have some disadvantages like some fail to give immunity, revert to virulant form by mutation, causes unknown effect or act as allergic agents in the host. To overcome these effects, purified specific macro molecule(antigenic molecules) derived from the pathogenic microorganisms are used in the preparation of vaccines. Examples of this type are pure capsular polysaccharide(streptococcus pneumonia vaccine) denatured toxins called toxoids(tetanus) recombinantly produced surface antigen(Hepatitis B vaccines) etc.
c) Recombinant-vector vaccines: The genes that encode major antigens of dangerous pathogenic organisms are introduced into non pathogenic or attenuated organisms(bacteria or virus) which act as vector. These attenuated organisms are called recombinant vectors which are introduced into host where these vector organisms express antigenic proteins during their growth. These antigenic proteins induce both cellular and humoral immunity in host. Adeno virus, canary pox virus, vaccinia virus, attenuated polio virus attenuated salmonella and mycobacterium have been used as vector vaccines.
d) DNA Vaccines: The DNA encoding antigenic proteins are injected directly to the muscle cells of the recipient. These transformed muscle cells take up and express the antigenic proteins. These antigenic proteins stimulate both cellular and humoral immunity in in the host. The DNA may integrate into the chromosomal DNA or maintained as episomal form in the cells. Now, DNA vaccines against AIDS, Hepatitis B, herpes, influenza and malaria are under human trails.
e) Synthetic peptide vaccines: As various pathogenic antigen sequences are known, efforts are made to synthesize small peptides and introduced into recipient still lot of procedural progress has to be made in this category.
f) Multivalent sub unit vaccines: The synthetic peptide vaccines are known to induce only humoral immunity and less of cellular immunity, thus antigenic synthetic peptide compounds which induce both humoral immunity and cell mediated immunity are attached to monoclonal antibodies on a solid matrix this matrix is known as solid matrix antigen-antibody complex. It helps in making particulate matter, that facilitates phagocytosis and thus induce humoral and cellular immunity. The other methods include incorporation of antigenic peptides into protein micells or into lipid vesicles(liposomes)