Salivary anti-PGL-1 IgM may indicate active transmission of Mycobacterium leprae among young people under 16 years of age

Abstract

Considering that the main route of Mycobacterium leprae transmission is the upper respiratory tract, detection of salivary antibodies can be a useful tool for diagnosing early infection. The study aimed to analyze salivary anti-PGL-1 IgA and IgM antibodies in 169 children aged 4-16 years old, who lived nearby or inside the house of multibacillary or paucibacillary leprosy patients in two endemic cities in Alagoas State - Brazil. Salivary anti-PGL-1 antibodies were quantified by modified ELISA method. The frequency of contact and clinical form of the index case were significantly associated with salivary antibody levels. High frequency of IgM positivity strongly suggests active transmission of M. leprae in these communities. We suggest in the present work that salivary anti-PGL IgA and IgM are important biomarkers to be used for identifying communities with probable active transmission of M. leprae.

Serum IgA Antibodies Specific to M. leprae Antigens as Biomarkers for Leprosy Detection and Household Contact Tracking

“…Interestingly, our experiments show that the IgA responses did not rely on the nature of the antigen, because all the evaluated antigens led to increased IgA reactivity. In that sense, it has already been demonstrated that IgA reactivity to PGL-I correlates with IgM responses in both serum and saliva (19,28). As the nasal mucosal surfaces are the main portal of entrance for M. leprae (18), the antigen challenge induces local humoral antibody responses, mainly IgA, which appears early in saliva than in serum (18).…”

In search of biomarkers for leprosy by unraveling the host immune response to Mycobacterium leprae

“…Contacts of untreated leprosy patients, which are continuously exposed to M leprae , showed higher salivary IgA levels to M leprae than endemic controls, indicative of an activated mucosal immune response 59 . High salivary IgA levels in response to LAM or PGL‐I compared to controls were also observed in household contacts, 60,61 especially in frequent contacts of MB patients 62 . The level of exposure to M leprae therefore seems to correlate to the salivary IgA levels.…”

“…59 High salivary IgA levels in response to LAM or PGL-I compared to controls were also observed in household contacts, 60,61 especially in frequent contacts of MB patients. 62 The level of exposure to M leprae therefore seems to correlate to the salivary IgA levels. The IgA antibodies observed in the mucosal airways might confer protection to M leprae infection by efficiently clearing the bacterium at the site of infection.…”

Recent laboratory advances in diagnostics and monitoring response to treatment in leprosy

“…[838485] Several studies in Indonesia, India, and Brazil have indicated that in an endemic community as population are exposed to infection, the biological samples such as blood, nasal swabs, saliva, and slit-skin smears of contacts of patients remain positive either for ML-specific antibody or for specific component of ML. [868788899091] How many of these biomarker-positive contacts of the population will transform into cases is generally uncertain and depends on the immune status of the individual having subclinical infection. These diagnostic tests are performed only once in individuals who pass through a dynamic state of the immune system, and therefore every individual who test positive to these assays do not develop leprosy in future.…”