Transmission and protection in leprosy: indications of the role of mucosal immunity

Abstract

Summary Recent advances in treatment have achieved a large drop in the prevalence of active leprosy cases, but the incidence is at best decreasing slowly. Most people within leprosy-endemic populations have been exposed to Myco bacterium leprae, but few develop disease and it seems likely that the majority of the population develops protective immunity. If the site of initial infection is in the nose, dissemination of bacilli around the body to skin and nerve implies that the initial infection is bacilliferous and it has been shown that nasal M. leprae are detectable by polymerase chain reaction (PCR) of nasal swabs. Since salivary anti-M. leprae IgA (sMLIgA) levels are correlated with protection, 5 we have surveyed groups ofleprosy patients, contacts and the general population for both their sMLIgA and nasal PCR positivity. A total of 304 subjects were enrolled in the study: PCR and mucosal challenge tests were performed in 204 of these individuals. sMLIgA was present in 66% of treated patients, 76% of leprosy workers and 72% of healthy contacts. However, only 33% of indigenous subjects were sMLIgA+, in contrast to the earlier studies showing 74% positivity. 5 PCR for M. leprae was present in both household contacts (2%) and indigenous controls (5%). In a subsequent fo llow-up study, nasal swabs were taken from 97 of those studied in the first series: three PCR+ individuals followed up after one year became negative, while of the remaining 94 PCR-individuals retested, 2

Monoclonal IgA Antibodies Protect Against Acanthamoeba Keratitis

“…Because IgA antibodies are not strongly associated with inflammatory responses, immunization procedures which stimulate IgA antibodies provide a different form of protection than conventional immunization. A growing body of evidence has demonstrated the efficacy and protective ability of IgA antibodies against such diverse pathogens as the influenza virus, Herpes simplex virus, plague and leprosy (Ramaprasad et al, 1997 ;Eyles et al, 1998 ;Higaki et al, 1998 ;Gallichan and Rosenthal, 1998). This study extends these observations by directly demonstrating the protective effects of IgA against an ocular pathogen.…”

Diversity of Potential Short Tandem Repeats in Mycobacterium leprae and Application for Molecular Typing

“…Some regard human beings as a host for the bacteria, while others are still considering more possibilities. It was proposed that the nasal mucosa are the exit/entry pathway of M. leprae (9,17,18). In light of the transmission mode, human-to-human direct contact was first generally accepted (6, 16), with time as airborne (23), as vector-borne (14, 25) and as vehicle-borne (3, 12) routes from evidence that has been obtained.…”

Detection of Mycobacterium leprae DNA by polymerase chain reaction in the blood and nasal secretion of Brazilian household contacts

“…Most people within leprosy-endemic populations have been exposed to M. leprae but few develop the disease, and it seems likely that the majority of the population present genetic resistance (Feitosa et al 1995, Santos et al 2002, Mira et al 2004) and develops protective immunity (Ramaprasad et al 1997). The interruption of leprosy transmission is one of the main challenges of leprosy control programs since no consistent evidence exists that transmission has been reduced after the introduction of multidrug therapy (Buhrer-Sekula et al 2003).…”