There is little information about the mucosal immune response in
leprosy. We have developed a nasal provocation test with
leprosin A which will be used to investigate mucosal immunity to Mycobacterium leprae. Initial studies were performed with increasing doses of
leprosin A (1.0 pg/ml-10 micrograms/ml) to determine the optimal safe dose of
leprosin A. Anti-M. leprae
IgA antibody and normal
IgA concentrations were measured in the saliva of
leprosy contacts and controls before and after instillation of
leprosin A. Nasal
leprosin A was well tolerated up to a concentration of 10 micrograms/ml without side effects. None of the six subjects who had not been exposed to
leprosy had salivary
IgA against whole M. leprae, whereas
IgA was detected from 64 h to 140 h following instillation of
leprosin A in all of the
leprosy hospital workers and in 15 out of 18 healthy household contacts tested. There was no correlation between serum and salivary anti-M. leprae
IgA levels before and after testing. Salivary
IgA anti-
lipoarabinomannan responses were seen in 12 out of 20 household contacts. Normal salivary
IgA concentrations varied from 8 to 240 mg/l. The
leprosin A nasal provocation test appears to be a safe method for the investigation of the role of mucosal immunity in the pathogenesis of
leprosy.