Early Revelation of Leprosy in China by Sequential Antibody Analyses with LID-1 and PGL-I

Leprosy is a disabling chronic infection, with insidious onset that often evades early detection. In order to detect new leprosy cases in a timely manner, we conducted surveillance visits in some difficult-to-reach mountain areas in South West China where the disease is still prevalent. Our data confirm that Chinese multibacillary (MB) leprosy patients have strong antibody responses against Mycobacterium leprae antigens ND-O-BSA and LID-1. Contacts of clinically diagnosed patients were then monitored at regular intervals by both physical examinations and the laboratory determination of antibody responses in sera collected during these examinations. Elevations in antibody titers indicated the onset of MB leprosy in one of the contacts, and diagnosis was subsequently confirmed on physical examination. Our data indicate that rising antibody titers can be used as a trigger for physical examination or increased monitoring of particular individuals in order to provide early leprosy diagnosis. 1. Introduction Leprosy is the clinical manifestation of infection with Mycobacterium leprae. ？With a slow growth rate of division every 12-13 days at an optimum temperature of 30°C, M. leprae bacteria infect macrophages and Schwann cells [1]. Infection of Schwann cells predisposes infected individuals to nerve damage, rendering leprosy, a chronic disabling infection with insidious onset typically characterized by the early involvement of skin and peripheral nerves. The immune response of the leprosy patient shapes the clinical presentation [2]. The response can limit bacterial growth and dissemination, resulting in few localized skin lesions and the definition of such patients as paucibacillary (PB). In cases where the response does not control bacterial growth, high bacterial burden arises, infection becomes systemic and many disseminated lesions and significant nerve function impairment can be observed; these patients are defined as multibacillary (MB). If such cases are left untreated, leprosy can progress to disfigurement and disability. Although early detection is recommended by World Health Organisation (WHO), diagnosis is currently achieved only upon the recognition of clinical symptoms by skilled clinicians [3]. As leprosy is usually associated with low socioeconomic development, patients often have limited access to medical care and evade early detection. Misdiagnosis is also common in clinics within large municipalities. Estimates are that patients are misdiagnosed an average of 2 times, resulting in a substantial amount of time passing from the onset of