Identification of an N-terminal 27 kDa fragment of Mycoplasma pneumoniae P116 protein as specific immunogen in M. pneumoniae infections.

BACKGROUND: Mycoplasma pneumoniae is an important cause of respiratory tract infection and is increasingly being associated with other diseases such as asthma and extra-pulmonary complications. Considerable cross-reactivity is known to exist between the whole cell antigens used in the commercial serological testing assays. Identification of specific antigens is important to eliminate the risk of cross-reactions among different related organisms. Adherence of M. pneumoniae to human epithelial cells is mediated through a well defined apical organelle to which a number of proteins such as P1, P30, P116 and HMW1-3 have been localized, and are being investigated for adhesion, gliding and immunodiagnostic purposes. METHODS: A 609 bp fragment P116(N-27), corresponding to the N-terminal region of M. pneumoniae P116 gene was cloned and expressed. A C-terminal fragment P1(C-40), of P1 protein of M. pneumoniae was also expressed. Three IgM ELISA assays based on P116(N-27), P1(C-40) and (P116 (N-27) + P1(C-40)) proteins were optimized and a detailed analysis comparing the reactivity of these proteins with a commercial kit was carried out. Comparative statistical analysis of these assays was performed with the SPSS version 15.0. RESULTS: The expressed P116(N-27) protein was well recognized by the patient sera and was immunogenic in rabbit. P1(C-40) of M. pneumoniae was also immunogenic in rabbit. In comparison to the reference kit, which is reported to be 100% sensitive and 75% specific, ELISA assay based on purified P116(N-27), P1(C-40) and (P116(N-27) + P1(C-40)) proteins showed 90.3%, 87.1% and 96.8% sensitivity and 87.0%, 87.1% and 90.3% specificity respectively. The p value for all the three assays was found to be < 0.001, and there was a good correlation and association between them. CONCLUSION: This study shows that an N-terminal fragment of P116 protein holds a promise for serodiagnosis of M. pneumoniae infection. The IgM ELISA assays based on the recombinant proteins seem to be suitable for the use in serodiagnosis of acute M. pneumoniae infections. The use of short recombinant fragments of P116 and P1 proteins as specific antigens may eliminate the risk of cross-reactions and help to develop a specific and sensitive immunodiagnostic assay for M. pneumoniae detection.

The presence of Mycoplasma pneumoniae infection and GM1 ganglioside antibodies in Guillain-Barré syndrome.

INTRODUCTION: Guillain-Barré syndrome (GBS) is an autoimmune disorder affecting the peripheral nervous system, usually triggered by an acute infection. GBS patients are known to have antecedent bacterial infections associated with auto-antibodies to various gangliosides. This investigation aimed to evaluate GBS patients for serological evidence of Mycoplasma pneumoniae infection and anti GM1 ganglioside antibodies. METHODOLOGY: This cross-sectional study included 57 pediatric GBS patients, 42 neurological controls (i.e., non-GBS Acute Flaccid Paralysis cases) and 35 non-neurological controls. Enzyme linked immune sorbent assay (ELISA) was performed on the sera of the subjects to detect IgM and IgG antibodies against Mycoplasma (M.) pneumoniae and GM1 gangliosides. RESULTS: The results showed that 15.79% and 21.05% GBS patients were positive for IgG and IgM antibodies against M. pneumoniae as compared to 2.38% (P < 0.05) and 14.2% in non-GBS-AFP and 5.7% and 14.2% in non-neurological controls respectively. Additionally, 43.85% and 38.54% GBS patients were positive for IgG and IgM antibodies against GM1 gangliosides as compared to 38.09% and 28.57% in non-GBS-AFP and 14.2% and 2.84% in non-neurological controls respectively (P < 0.05). CONCLUSIONS: Significant difference in levels of IgG antibodies against M. pneumoniae was observed between GBS patients and neurological controls, suggesting M. pneumoniae to be an important antecedent to GBS. Significant difference in levels of anti GM1 ganglioside antibodies (IgG & IgM) was seen between GBS patients and non-neurological controls, highlighting its possible role in the pathogenesis of GBS.

A fulminant case of acute respiratory distress syndrome associated with Mycoplasma pneumoniae infection.

Acute respiratory distress syndrome (ARDS) caused by mycoplasmas is very rare. This report describes a severe case of atypical pneumonia due to M. pneumoniae in a formerly healthy young woman who developed high grade fever and cough leading to severe disseminated lung disease and finally to fatal ARDS. This case came into picture when killer atypical pneumonia, namely, SARS (severe acute respiratory syndrome), spread very fast from South-Asian countries to the rest of the world. Moreover, the clinical presentation and radiologic features of SARS bear resemblance to the syndrome of atypical pneumonia, which lead us to investigate this case into detail. We suggest that M. pneumoniae infections should be included in the differential diagnosis of pathogens causing ARDS, establishing an early diagnosis may have important therapeutic implications.