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Vaccination and skin test studies on the children of leprosy patients
J L Stanford1, C A Stanford, K Ghazi Saidi
1School of Pathology, University College and Middlesex School of Medicine, London, U.K.
Insights
Two new vaccines combining BCG with Mycobacterium vaccae significantly boosted leprosin A skin-test positivity in children of leprosy patients. This suggests a potential advance in preventing multibacillary leprosy among close contacts.
Area of Science:
- Immunology
- Infectious Diseases
- Vaccinology
Background:
- Leprosy remains a significant global health challenge, particularly for close contacts of infected individuals.
- BCG vaccination is used for leprosy prevention, but its efficacy varies.
- Developing effective vaccines to enhance immunity against leprosy is crucial.
Purpose of the Study:
- To evaluate the efficacy of two novel vaccine formulations in increasing skin-test positivity to leprosin A in children of leprosy patients.
- To assess the long-term immune response to mycobacterial antigens after vaccination.
Main Methods:
- Two groups of children of leprosy patients were vaccinated: one with BCG Glaxo plus killed Mycobacterium vaccae (vaccine B), and another with killed M. vaccae alone (vaccine D).
- Skin testing with leprosin A was performed initially and repeated eight years later.
- Response to common mycobacterial antigens (category 1 responders) was analyzed.
Main Results:
- Both vaccine B and vaccine D significantly increased the proportion of children responding to leprosin A compared to expected responses from BCG Pasteur alone.
- The increase in leprosin A positivity was largely attributed to a higher response rate to common mycobacterial antigens (category 1 responders).
Conclusions:
- Combining BCG with killed Mycobacterium vaccae shows promise in enhancing immune responses relevant to leprosy prevention.
- These findings suggest a potential advancement in strategies to protect close contacts from multibacillary leprosy, contingent on leprosin A positivity being a reliable correlate of protection.
Abstract:
In an attempt to achieve maximal skin-test positivity to leprosin A in children of leprosy patients living in Baba Baghi Leprosy Sanatorium in Iranian Azerbaijan, two new vaccines have been employed. Children without scars of previous BCG and without response to leprosin A were given a vaccine containing 10(8) viable units of BCG Glaxo plus 10(7) killed Mycobacterium vaccae per dose (vaccine B). Children with BCG Pasteur (Teheran) scars but without response to leprosin A were given a vaccine containing 10(8) killed M. vaccae alone (vaccine D). Eight years later skin testing was repeated, and both new vaccines were found to have significantly increased the numbers of children responding to leprosin A above the level that would have been expected had they received BCG Pasteur alone. This increase was due in large part to increases in the proportions of individuals responding to group i (common mycobacterial) antigens, and known as category 1 responders. The use of suspensions of killed M. vaccae in conjunction with BCG may represent a considerable advance in inducing protection from multibacillary leprosy in close contacts of leprosy patients if leprosin A positivity is truly a correlate of protective immunity. A comparison, using the same criteria, with the other proposed vaccines for leprosy would be very interesting.