ABC transporter ATPase of Chlamydophila pneumoniae as a potential vaccine candidate.

Better vaccines and new therapeutic drugs could be a successful breakthrough against intracellular bacteria. M. tuberculosis ABC transporter ATPase (Rv0986) plays a role in mycobacterial virulence by inhibiting phagosome-lysosome fusion. Thus, it could be a potential vaccine candidate. C. pneumoniae another important intracellular bacterium possesses a protein named CpB0255, which is homologous with the mycobacterial Rv0986. The aim of this study was the cloning, over-expression and purification of CpB0255 ABC transporter ATPase protein to study its biological properties. The immunogenicity and protective effect of recombinant chlamydial ATPase protein combined with Alum adjuvant were investigated in mice. The immunization resulted in the reduction of the number of viable C. pneumoniae in the lungs after challenge. Our results confirm that chlamydial ATPase induces protective immunity in mice.

Immunization with a combination of ApoB and HSP60 epitopes significantly reduces early atherosclerotic lesion in Apobtm2SgyLdlrtm1Her/J mice.

OBJECTIVE: HSP60 is emerging as an immunodominant target of autoantibodies in atherosclerosis and recent studies have revealed oxLDL as a key antigen in the development of atherosclerosis. In this study, we assay whether immunizing Apobtm2SgyLdlrtm1Her/J mice with a combination of ApoB and human HSP60 peptides has an additive effect on atheroprotection compared to ApoB or HSP60 peptides applied alone by following atherosclerotic lesion development. METHODS AND RESULTS: In this study, 2 weeks after the first immunization, Apobtm2SgyLdlrtm1Her/J mice were placed on a high-fat diet for 8 weeks followed by 2 weeks on a normal diet allowing the mice to adapt to the environment before sacrifice. High levels of ApoB and HSP60 antibodies were detectable in week 2 and week 12 following the first immunization with KLH-conjugated ApoB and HSP60 peptides either individually or in combination. Histological analyses demonstrated that mice immunized with both, ApoB and HSP60 peptides, showed the most significant reduction in atherosclerotic lesions (41.3%; p<0.001) compared to a reduction of 14.7% (p<0.05) and 21.1% (p<0.01) in mice immunized with ApoB or HSP60 peptides, respectively; control mice were immunized with either PBS or adjuvant alone. These results were further supported by significant differences in the cellular and humoral immune responses between test animals. CONCLUSIONS: Immunization with a combination of ApoB and HSP60 peptide antigens significantly reduced early atherosclerotic lesions in the Apobtm2SgyLdlrtm1Her/J mouse model of atherosclerosis. This approach offers promise as a novel strategy for developing anti-atherosclerotic agents.

Quaternary structure and biochemical properties of mycobacterial RNase E/G.

The RNase E/G family of endoribonucleases plays the central role in numerous post-transcriptional mechanisms in Escherichia coli and, presumably, in other bacteria, including human pathogens. To learn more about specific properties of RNase E/G homologues from pathogenic Gram-positive bacteria, a polypeptide comprising the catalytic domain of Mycobacterium tuberculosis RNase E/G (MycRne) was purified and characterized in vitro. In the present study, we show that affinity-purified MycRne has a propensity to form dimers and tetramers in solution and possesses an endoribonucleolytic activity, which is dependent on the 5'-phosphorylation status of RNA. Our data also indicate that the cleavage specificities of the M. tuberculosis RNase E/G homologue and its E. coli counterpart are only moderately overlapping, and reveal a number of sequence determinants within MycRne cleavage sites that differentially affect the efficiency of cleavage. Finally, we demonstrate that, similar to E. coli RNase E, MycRne is able to cleave in an intercistronic region of the putative 9S precursor of 5S rRNA, thus suggesting a common function for RNase E/G homologues in rRNA processing.

The role of histamine in the intracellular survival of Mycobacterium bovis BCG.

The course and outcome of infection with mycobacteria are determined by a complex interplay between the immune system of the host and the survival mechanisms developed by the bacilli. Histamine plays an important role in various processes, including cell division, metabolism, and apoptosis, and it modulates innate and adaptive immune responses. In the present study we investigated the intracellular survival of Mycobacterium bovis BCG in murine bone-marrow macrophages isolated from wild-type (WT) and histidine-decarboxylase knock-out [HDC (-/-)] mice. Mycobacterial titers were significantly higher in the HDC (-/-) macrophages as compared with the WT cells. M. bovis BCG growth in WT macrophages could be enhanced by pyrilamine and cimetidine. Exogenously added histamine decreased the intracellular counts of M. bovis BCG in HDC (-/-) macrophages. Infection of activated macrophages with M. bovis BCG elicited apoptosis, but there was no significant difference between the WT and the HDC (-/-) cells. These bacilli induced comparable levels of tumor necrosis factor-alpha production in the WT and the HDC (-/-) macrophages. M. bovis BCG stimulated interleukin-18 (IL-18) production in the macrophages from WT mice, but not in the HDC (-/-) cells. Exogenously added IL-18 decreased the titers of intracellular mycobacteria in HDC (-/-) cells. In conclusion, these data implicate histamine in the intracellular survival of M. bovis BCG. The cellular control mechanisms restricting the growth of M. bovis BCG are complex and involve H1 and H2 receptor-mediated events. Histamine might be an important mediator of M. bovis BCG-induced IL-18 production, which in turn contributes to immune protection.

Mycobacterial RNase E-associated proteins.

RNase E and its complex with other proteins ('degradosome') play an important role in RNA processing and decay in Escherichia coli and in many other bacteria. To identify the proteins which can potentially interact with this enzyme in mycobacteria, Mycobacterium tuberculosis H37Rv RNase E was cloned and expressed as a 6HisFLAG-tagged fusion protein. Analysis of the mycobacterial RNase E overexpressed and purified from M. bovis BCG revealed the presence of GroEL and two other copurified proteins, products of the Mb1721 (inorganic polyphosphate/ATP-NAD kinase) and Mb0825c (acetyltransferase) genes. Identical copies of these two genes can be found in M. tuberculosis H37Rv.