The antigens of Mycobacterium tuberculosis. Protein fractions from cytoplasm and culture filtrate

Purification and Characterization of Two Proteins from Culture Filtrates of Mycobacterium tuberculosis H(37)Ra Strain

Two proteins have been purified from culture filtrates of Mycobacterium tuberculosis, H(37)Ra strain by a procedure combining gel filtration, diethylaminoethyl (DEAE)-cellulose chromatography, and zone electrophoresis. The two proteins are similar in molecular weight but differ slightly in charge. The faster migrating protein, designated a(1), is not antigenic. The slower migrating protein, designated a(2), is antigenic both with respect to antisera and as a skin-testing antigen.

Separation of mycobacterial soluble antigens by isoelectric focusing

Ion-exchange chromatography and gel filtration have been reported to yield partial separation of mycobacterial antigens. These procedures were used in combination with isoelectric focusing in an attempt to purify antigens of Mycobacterium tuberculosis strain H37Ra. The fractionating action of isoelectric focusing is dependent upon differences in the isoelectric points of the proteins to be separated. Culture filtrate of M. tuberculosis H37Ra was chromatographed on Sephadex G-200. This resulted in two widely separated peaks. The first peak, presumably containing high-molecular-weight substances, was then fractionated on a diethylaminoethyl Sephadex anion-exchange column. Three peaks were collected, and each was subjected to isoelectric focusing. Each peak was further separated into two or more fractions. The serological reactivity of each fraction was determined by immunodiffusion and immunoelectrophoresis. Sensitized guinea pigs were also skin-tested with the fractions. Two of the fractions contained only a single precipitinogen. One fraction contained two precipitinogens. A fourth fraction contained three precipitinogens and was also the only fraction to display sensitin activity. Four of the fractions were inactive either as precipitinogens or sensitins. The results suggest that the methods described are useful for the separation of mycobacterial antigens.

Comparison of antigens in sonic and pressure cell extracts of Mycobacterium tuberculosis

Comparisons were made of the yield, chemical content, and biological activity of filtrates and extracts obtained by sonic and pressure cell disruption of bacilli from 4- and 8-week-old Proskauer and Beck cultures of the H37Rv strain (TMC no. 102) of Mycobacterium tuberculosis. The culture filtrates were dialyzed, freeze-dried, reconstituted in saline, and sterilized by membrane filtration. The viable bacilli were washed and resuspended in distilled water and subsequently disrupted either by sonication in the cold for 15 or 30 min or by treatment at 20,000 or 40,000 lb/in2 in a pressure cell. The resulting extracts were clarified by centrifugation, concentrated, and sterilized by filtration. All preparations were adjusted to contain 10 mg of solids (dry weight)/ml and were analyzed quantitatively for protein, deoxyribonucleic acid, ribonucleic acid, polysaccharide, and lipid content. Separation patterns obtained by gradient acrylamide gel electrophoresis, as well as by one- and two-dimensional immunoelectrophoresis, provided the basis for qualitative comparisons of the culture filtrates and cell extracts. Three-point dose-response curves also were used to compare the preparations for skin test reactivity in BCG-vaccinated guinea pigs. It was concluded that, although there were no consistent differences in chemical content or biological activity between the preparations, a 15-min sonic treatment appeared to be the most suitable method for preparation of bacillary extracts based on yield of active components and ease of preparation.

Characterization and comparison of mycobacterial antigens by two-dimensional immunoelectrophoresis

Two-dimensional immunoelectrophoresis (2D-IEP), in which a complex of antigens is subjected to electrophoresis first through an agarose matrix in one direction and secondly through an antiserum-agarose matrix at right angles to the first direction, was evaluated as a tool for analysis of mycobacterial antigens. Cell extracts from four species of mycobacteria, Mycobacterium tuberculosis (four strains), M. bovis strain BCG, M. scrofulaceum, and M. phlei, were assayed by 2D-IEP with four anti-mycobacterial antisera. Besides displaying the precipitin curves in a more easily interpreted format than did conventional immunoelectrophoresis (IEP), 2D-IEP offered greater sensitivity in terms of numbers of precipitin curves when like reactions were compared with IEP patterns. As many as 60 immunoprecipitates were observed on 2D-IEP slides compared to 18 on comparable IEP plates. Technical reproducibility of patterns from run to run was excellent. Other parameters, such as the influence of using different batches of antigen on the pattern, are discussed. Each of the cell extract antigens gave a unique pattern of precipitin peaks which could be easily differentiated from the patterns given by the other mycobacterial cell extracts when reacted with any of the antisera in 2D-IEP. Since both the species and strains of mycobacteria could be easily and reproducibly differentiated solely on the basis of two-dimensional immunoelectrophoretic patterns obtained with any of the antisera employed in this study, it may be possible, by using IEP, to differentiate and identify all species and strains of mycobacteria with one standard, highly sensitive antiserum, rather than a battery of antisera.