Abstract
Leprosy is mainly transmitted among family members who share genetic and ambient factors. The clinical form of leprosy in the index case and kinship could be risk factors for leprosy transmission. High antibody levels in household contacts (HC) in the absence of neural or skin lesions may characterize latent infection. This study aimed to evaluate the association between seropositivity for anti-phenolic glycolipid-I immunoglobulin M antibodies (APGL-I) in HC and the clinical classification of the index case and to analyze the association between APGL-I positivity with other factors such as age, kinship, and gender. We performed a survey among 320 HC of 120 leprosy patients who were evaluated and followed-up in a leprosy outpatient clinic of a university hospital. All HC underwent complete skin examination, peripheral nerve palpation, skin sensory tests, and serologic tests for the detection and quantification of APGL-I. The overall seropositivity rate was 20%, and was greatly affected by kinship. APGL-I seropositivity was higher in siblings (41%), followed by parents (28%), spouses (26%), other (19%), and offspring (14%). Independent risk factors for seropositivity were being siblings (OR 3.3) and being a HC of an index case with indeterminate leprosy (OR 5.3). APGL-I seropositivity was associated with index cases with a bacillary index of 4 (88%; p<.001). Seropositivity among HC was not significantly associated with their gender and age. There was no statistical difference in the seropositivity rates of HC of index patients with paucibacillary and multibacillary leprosy. Strict evaluation and follow-up of HC with positive results for APGL-I is recommended. Special attention should be paid during the screening of siblings of the index cases, HC of patients with a high bacillary index, and HC of patients with indeterminate leprosy.
Highlights
Leprosy is mainly transmitted among family members who share genetic and ambient factors
This study aimed to evaluate the association between seropositivity for anti-phenolic glycolipid-I immunoglobulin M antibodies (APGL-I) in household contacts (HC) and the clinical classification of the index case and to analyze the association between APGL-I positivity with other factors such as age, kinship, and gender
Studies have reported that 40-95% of multibacillary leprosy (MB) patients present with high levels of APGL-I(3) (5) (6) (7) (8), whereas 15-28% of paucibacillary leprosy (PB) patients present with low levels of APGL-I(6) (8), similar to that noted in the normal control population(1)
Summary
Leprosy is mainly transmitted among family members who share genetic and ambient factors. In cases of tuberculoid leprosy (TT), the immune system is capable of destroying the causative pathogen through the cellular immune response, resulting in well-defined granulomatous skin lesions, with no detectable bacilli(1), and low levels of anti-phenolic glycolipid-I immunoglobulin M (APGL-I), specific antibodies against Mycobacterium leprae(1) (3). On the other end of the spectrum, cases of lepromatous leprosy (LL) are characterized by an individual’s inability to develop an effective cellular immune response, leading to mycobacterial survival and multiplication, and dissemination of skin lesions with a high bacillary load. These LL patients, develop a strong, yet ineffective, humoral immune response with high levels of APGL-I(1) (4).
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