This study aimed to determine the role of surfactant protein A (SP-A) in the formation of stable microbubble in tracheal aspirates. Our results showed that as the concentration of anti SP-A antibodies added to tracheal aspirate specimens increased, the number of stable microbubble formed in the specimen decreased. The correlation between stable microbubble counts and the SP-A levels in the tracheal aspirates was good, r = 0.85, p < 0.05. This study suggests that SP-A plays an important role in stable microbubble formation. Measurement of small stable microbubbles is thus a useful bedside test for predicting the SP-A activity in the tracheal aspirates and in indirect measurement of lung maturity.
An in-house enzyme-linked immunoabsorbant assay (ELISA) for SP-A was successfully developed using in-house polyclonal anti SP-A and a commercial polyclonal anti-rabbit immunoglobulin horseradish peroxidase conjugate system. The standard curve, generated by using 50 ng of SP-A to coat the plate and 1:500 dilution of polyclonal anti SP-A as a primary antibody, was linear for concentrations of SP-A ranging from 4 micrograms/l to 4000 micrograms/l and reproducible. Results of recovery study of SP-A from a known sample of tracheal aspirate ranged from 94%-114%. Intra- and inter-assay coefficients of variations were 2.7% and 5.6% respectively for a known sample of tracheal aspirate. Interference study showed that tracheal aspirate did not interfere with the assay. The assay developed was intended to be used for SP-A measurement in tracheal aspirates obtained from neonates with and without respiratory distress syndrome.
Tuberculosis (TB) remains an important cause of mortality and morbidity. The TB vaccine, BCG, is not fully protective against the adult form of the disease and is unable to prevent its transmission although it is still useful against severe childhood TB. Hence, the search for new vaccines is of great interest. In a previous study, we have shown that proteoliposomes obtained from Mycobacterium smegmatis (PLMs) induced cross reactive humoral and cellular response against Mycobacterium tuberculosis (Mtb) antigens. With the objective to evaluate the protective capability of PLMs, a murine model of progressive pulmonary TB was used. Animals immunized with PLMs with and without alum (PLMs/PLMsAL respectively) showed protection compared to non-immunized animals. Mice immunized with PLMsAL induced similar protection as that of BCG. Animals immunized with BCG, PLMs and PLMsAL showed a significant decrease in tissue damage (percentage of pneumonic area/lung) compared to non-immunized animals, with a more prominent effect in BCG vaccinated mice. The protective effect of the administration of PLMs in mice supports its future evaluation as experimental vaccine candidate against Mtb.