Demonstration of PGL-I & LAM-B antigens in paraffin sections of leprosy skin lesions

Leprosy: a review of laboratory and therapeutic aspects--part 2

Leprosy is a chronic infectious condition caused by Mycobacterium leprae(M. leprae). It is endemic in many regions of the world and a public health problem in Brazil. Additionally, it presents a wide spectrum of clinical manifestations, which are dependent on the interaction between M. leprae and host, and are related to the degree of immunity to the bacillus. The diagnosis of this disease is a clinical one. However, in some situations laboratory exams are necessary to confirm the diagnosis of leprosy or classify its clinical form. This article aims to update dermatologists on leprosy, through a review of complementary laboratory techniques that can be employed for the diagnosis of leprosy, including Mitsuda intradermal reaction, skin smear microscopy, histopathology, serology, immunohistochemistry, polymerase chain reaction, imaging tests, electromyography, and blood tests. It also aims to explain standard multidrug therapy regimens, the treatment of reactions and resistant cases, immunotherapy with bacillus Calmette-Guérin (BCG) vaccine and chemoprophylaxis.

Mycobacterium lepraein Neurons of the Medulla Oblongata and Spinal Cord in Leprosy

Peripheral neuropathy has been extensively studied in leprosy, a chronic disease caused by Mycobacterium leprae, but the central nervous system (CNS) is thought to be free from bacilli. Involvement of the CNS was explored in autopsy cases of clinically cured lepromatous leprosy (n = 67) and in non-leprosy cases (n = 15). Paraffin sections of the medulla oblongata and spinal cord were subjected to hematoxylin and eosin staining, Fite acid-fast staining, and anti-phenolic glycolipid-I (PGL-I) immunostaining. PGL-I-positive areas were microdissected from selected cases and nested polymerase chain reaction (PCR) targeting the M. leprae-specific repetitive sequence was performed. Of the 67 cases of leprosy, 44 (67%) had vacuolar changes of motor neurons either in medulla oblongata (nucleus ambiguous or hypoglossal nucleus) or spinal cord. Fite staining was negative, but PGL-I was positive in vacuolated areas. PCR revealed M. leprae-specific genomic DNA in 18 of 19 cases (95%) with vacuolated changes and 5 of 8 (63%) without vacuolated changes. All of above findings were negative in control cases. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining did not show a significant increase of apoptosis in the neurons. The PCR positivity had a significant correlation with PGL-I immunostaining (p < 0.05). The presence of vacuolar changes in the spinal cord was correlated with hand and feet deformity grades (p = 0.04). This study provides significant additional evidence to indicate that M. leprae is present in the CNS in a subset of patients. Further investigation is required to correlate this finding to motor dysfunction and silent neuropathy in leprosy.

Immunohistological analysis of in situ expression of mycobacterial antigens in skin lesions of leprosy patients across the histopathological spectrum. Association of Mycobacterial lipoarabinomannan (LAM) and Mycobacterium leprae phenolic glycolipid-I (PGL-I) with leprosy reactions

The presence of mycobacterial antigens in leprosy skin lesions was studied by immunohistological methods using monoclonal antibodies (MAbs) to Mycobacterium leprae-specific phenolic glycolipid I (PGL-I) and to cross-reactive mycobacterial antigens of 36 kd, 65 kd, and lipoarabinomannan (LAM). The staining patterns with MAb to 36 kd and 65 kd were heterogeneous and were also seen in the lesions of other skin diseases. The in situ staining of PGL-I and LAM was seen only in leprosy. Both antigens were abundantly present in infiltrating macrophages in the lesions of untreated multibacillary (MB) patients, whereas only PGL-I was occasionally seen in scattered macrophages in untreated paucibacillary lesions. During treatment, clearance of PGL-I from granulomas in MB lesions occurred before that of LAM, although the former persisted in scattered macrophages in some treated patients. This persistence of PGL-I in the lesions paralleled high serum anti-PGL-I antibody titers but was not indicative for the presence of viable bacilli in the lesions. Interestingly, we also observed a differential expression pattern of PGL-I and LAM in the lesions of MB patients with reactions during the course of the disease as compared with those without reactions. In conclusion, the in situ expression pattern of PGL-I and LAM in MB patients may assist in early diagnosis of reactions versus relapse.