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Neisseria meningitidis, Haemophilus influenzae type B and Sterptococcus pneumonia are important human pathogens, particularly in young children. Explain why a vaccine against each of these organisms has been developed for children who are less than two ye

March 29, 2016 | Author: | Posted in labor studies, social sciences

p Neisseria meningitidis , Haemophilus influenzae type B and Sterptococcus pneumonia are important human pathogens , particularly in young children . Explain why a vaccine against each of these organisms has been developed for children who are less than two years

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Defensive immunity to encapsulated bacteria entails an antibody response to a polysaccharide (PS ) antigen , interactions with B and T lymphocytes , and host defense mechanisms . PS vaccines , like those developed against Neisseria meningitidis , Streptococcus pneumoniae Haemophilus influenzae type B , prevent [banner_entry_middle]

infection by provoking an immune response against particular capsular polysaccharides . These vaccines however , presented little protective immunity in young children and infants . The invention of glycoconjugate vaccines was a need of time to over come many limitations related with PS vaccines by entailing a quantitatively and qualitatively diverse immune response Encapsulated bacteria are significant pathogens that cause disease particularly among infants , the elderly , and persons with compromised immunity . In spite of antibiotic treatment , the morbidity and mortality from bacteremia , meningitis , and pneumonia caused by these organisms are still elevated in these populations . The mechanism by which nearly all encapsulated bacterial pathogens inflicts disease in children engross virulence factors e .g . surface capsular polysaccharides (PSs . The PS antigens contained in vaccines in the earlier period conversely , were weakly immunogenic and did not provoke defensive immunity in younger children .1

There was an immense need to enhance protective immunity in higher risk individuals particularly younger children which resulted in the development of conjugate vaccines . The pairing of PS antigens to a carrier protein overcame the immunologic restrictions faced with PS vaccines . The conjugation of Haemophilus influenzae type B (HiB ) PS to diphtheria toxoid , tetanus toxoid , meningococcal outer membrane protein or mutant diphtheria protein CRM197 and consequent vaccination with HiB PS as a glycoconjugate vaccine effectively resulted in a more than 97 decrease of HiB disease in certain Europian countries and United States of America .2

Capsular PSs are highly polar , hydrophilic cell surface polymers comprising of oligosaccharide repeat units . These molecules are the key antigens concerned in the defensive protection to encapsulated bacteria Capsular PSs hinder with bacterial contact with phagocytes by jamming opsonization . Opsonization is the coating of the organisms by particular antibodies and complement , that enables host phagocytes to swallow and kill invading bacteria . Antibodies to capsular PSs might work as bacterial-cell-to-phagocytic-cell ligands or as complement activators .3

The reaction to a capsular PS is T-cell-independent , sensing that B lymphocytes flourish and generate antibody without the assistance of T cells . Conjugation combines a PS to a carrier protein , which alters the capsular PS from a T-cell-independent antigen to a T-cell-dependent antigen . The immune response brought by this protein antigen utilize helper T cells and thus is T-cell- dependent . Helper T cells facilitates a more fast and improved immune response to take place on re-exposure to an antigen . In this way , a conjugate vaccine imparts immunologic memory and grants long-standing protective immunity

Along with an increased antibody production , an immune response… [banner_entry_footer]


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