vaccines for leprosy

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VACCINES FOR LEPROSY AJAY ABRAHAM MBBS 2007

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LEPROSY Chronic granulomatous disease caused by Mycobacterium leprae Primarily affects peripheral nerves and skin Among infectious diseases it is a leading causes of physical disability!!

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Clinical Presentation Hypo pigmented patches Total or partial loss of cutaneous sensation on affected areas Presence of thickened peripheral nerves Presence of acid-fast bacilli in skin or nasal smears

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Diagnosis Clinical Examination : History, Physical examination Bacteriological Examination : Skin smear, Skin biopsy Nerve biopsy Histamine test, sweating test Staining of the smears by Ziehl-Neelsen technique Microscopy to demonstrate the acid-fast bacilli

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Treatment Multidrug therapy Rifampicin : 600mg once monthly under supervision Dapsone : 100mg daily self administered Clofazimine: 300mg once monthly supervised and 50mg daily self administered

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VACCINE

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These are vaccines under trial Yet to achieve the status of a vaccine Now called by the name “CANDIDATE VACCINES”

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Category I (Based on M.leprae) Category II (Based on cultivable mycobacteria) Killed M.leprae Killed M.leprae + BCG Acetoacetylated M.leprae BCG BCG + M.vaccae Killed ICRC bacillus Candidate Vaccines

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One of the first vaccines to be used against leprosy was BCG Started way back in late 1970’s Lot of controversies about efficacy Lot of trials in different parts of the world showing different efficacies Efficacy varying from 0 to 80% History

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Convit et al showed that the immunogenicity of M.leprae (which is a weak immunogen) is enhanced by the addition of BCG and subsequently established the concept of a mixed vaccine containing a mixture of heat-killed armadillo-derived M.leprae ( M.leprae -A') + BCG

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A multi-arm trial of anti-leprosy vaccines was initiated in South India in January 1991, on a population of 3 lakh people of whom 1.75lakh where selected The trial had five arms-BCG alone, BCG+HKML, Mycobacterium welchii (M. w), ICRC bacillus and placebo Preliminary findings from the third re-survey conducted between August 1999 and December 2002 showed the overall vaccine efficacy to be 67% for BCG + HKML, 51% for ICRC, 41% for M. w. and 22% for BCG alone

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Practical difficulty Inability to culture Mycobacterium leprae! Overcome by growing M.leprae in Armadillos Newer technique available now: rDNA technology, Liquid chromatography etc

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ARMADILLO

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A mixed vaccine containing BCG and ICRC bacilli or their immunogenic 'sub-units' could be the future polyvalent mycobacterial vaccine that might offer protection against a wide spectrum of mycobacterial diseases The Future High efficacy of MDT has however brought down the need for advances in vaccines against leprosy