Isolated splenic tuberculosis in an immunocompetent patient

A 20-year-old woman presented with fever and was eventually diagnosed with splenic tuberculosis as the sole site of the disease. Laboratory data gave no specific information for diagnosis except for a raised erythrocyte sedimentation rate and mild anaemia. Abdominal ultrasonography revealed splenomegaly with multiple hypoechoic lesions within it. A diagnosis of isolated splenic tuberculosis was confirmed after CT-guided aspiration from splenic lesions showed the presence of acid-fast bacilli.

GLS/IL-12-modified Mycobacterium smegmatis as a novel anti-tuberculosis immunotherapeutic vaccine

OBJECTIVE

To study the effects and mechanisms of recombinant Mycobacterium smegmatis (rMS) carrying pZM03 (a co-expression plasmid encoding human granulysin [GLS] and murine interleukin 12 [IL-12]) on murine M. tuberculosis infection.

DESIGN

BALB/c mice infected with M. tuberculosis were treated with normal saline, M. smegmatis, pZM03 or rMS. The number of viable bacteria in the lungs and spleens were counted to observe the therapeutic effects. The levels of IL-12 and interferon-gamma (IFN-gamma) in serum, and IFN-gamma and tumour necrosis factor-alpha (TNF-alpha) released from spleen lymphocytes were detected to observe the T-helper 1 (Th1) response. Secretory IgA (SIgA) in bronchoalveolar lavage fluid was measured to observe the mucosal immunity. The lungs and spleens were prepared for pathological analysis.

RESULTS

The rMS group showed a significantly reduced number of colony-forming units compared to the other groups. The expression of GLS in the tissue, and increased levels of IL-12, IFN-gamma, TNF-alpha and SIgA, were found in the rMS group. The pathological changes in the lungs of the rMS group were localised, while those in the control group were extensive.

CONCLUSION

rMS had immunotherapeutic effects associated with a switch to the Th1 response and the antibacterial activity of GLS.

Mycobacterial infection in natural killer T cell knockout mice

To gain a better understanding of the pathological role of natural killer (NK) T cells in murine tuberculosis, NKT knockout (KO) mice (J(alpha)281(-/-)mice) were utilized. Eight-week-old NKT KO mice of BALB/c origin and wild-type (WT) mice were infected with Mycobacterium tuberculosis Kurono strain by the airborne route using an airborne infection apparatus, and their capacity to control mycobacterial growth, granuloma formation, and cytokine production were examined. The NKT KO mice developed granulomatous lesions in the lungs; there was no statistically significant difference in pulmonary granuloma size between NKT KO and WT mice (p<0.01). The average CFU values increased 3 weeks post-infection, but decreased 9 and 11 weeks post-infection, in the lungs of NKT KO mice. When stimulated with Kurono strain in vitro, splenic cells from NKT KO mice produced less IFN-gamma than did those from WT mice. Expression of mRNA for IL-2, IL-4, IL-6, IL-10 and IL-12 p40 was slightly lower in NKT KO mice compared with WT mice. Our data indicate that NKT cells play a detrimental role in late-phase mycobacterial infection, although Th1 cells are essential in early-phase mycobacterial infection.

Vaccination of guinea pigs with DNA encoding Ag85A by gene gun bombardment

A DNA vaccine encoding Ag85A from Mycobacterium tuberculosis was administered to guinea pigs by epidermal gene gun bombardment and its protective efficacy was determined. Vaccination with Ag85A DNA twice significantly reduced the severity of pulmonary pathology and number of pulmonary colony-forming units (CFU) (p<0.01). When immunogenic synthetic Ag85A peptide was used as a booster, lung pathology was improved significantly and pulmonary CFU were reduced dramatically. Neither Ag85A DNA nor BCG Tokyo protected the guinea pigs from hematogenous spread of tubercle bacilli to the spleen because splenic granulomas without central necrosis were recognized. When the vaccinated guinea pigs were followed up for 7 months, the pulmonary lesions became fibrotic in guinea pigs vaccinated with Ag85A DNA plus Ag85A peptide, or BCG Tokyo, and no tubercle bacilli were detected. The protective efficacy of the tuberculosis Ag85A DNA vaccine was improved significantly by peptide boosting. It is concluded that dosage and peptide boosting are important in the induction of higher protective efficacy by a tuberculosis DNA vaccine.

Abdominal findings in AIDS-related pulmonary tuberculosis correlated with associated CD4 levels

BACKGROUND

To document the abdominal manifestations of tuberculosis (TB) associated with human immunodeficiency virus (HIV) infection and to correlate those findings with CD4 levels.

METHODS

Twenty-nine HIV-positive patients with culture-proven Mycobacterium tuberculosis infection were entered into the study. Chest changes were used to separate patients into two groups: those with and those without evidence of previous TB. All patients had standard chest radiographs, routine and high-resolution chest computed tomography (CT), and abdominal ultrasound examinations. Twenty-four patients had abdominal CT scans.

RESULTS

The group of patients with no previous radiographic evidence of pulmonary TB had a significantly greater tendency to have manifestations of pulmonary and/or abdominal miliary dissemination. Those patients with radiological evidence of miliary dissemination were significantly more likely to have CD4 counts of less than 300.

CONCLUSIONS

Chest and abdominal miliary dissemination of TB in HIV-positive patients is significantly associated with radiologically determined primary onset pulmonary TB. These changes occur predominantly at CD4 counts of less than 300.

Induction of a type 1 immune response to a recombinant antigen from Mycobacterium tuberculosis expressed in Mycobacterium vaccae

A 19-kDa lipoprotein from Mycobacterium tuberculosis was expressed as a recombinant antigen in the nonpathogenic mycobacterial host strain M. vaccae. Immunization of mice with the recombinant M. vaccae resulted in induction of a strong type 1 immune response to the 19-kDa antigen, characterized by immunoglobulin G2a (IgG2a) antibodies and gamma interferon (IFN-gamma) production by splenocytes. Immunization with the same antigen in incomplete Freund's adjuvant induced a strong IgG1 response with only low levels of IFN-gamma. Subsequent intravenous and aerosol challenges of immunized mice with virulent M. tuberculosis demonstrated no evidence of protection associated with the response to the 19-kDa antigen; in fact, the presence of the recombinant 19-kDa antigen abrogated the limited protection conferred by M. vaccae (vector control). The recombinant M. vaccae system is a convenient approach to induction of type 1 responses to M. tuberculosis antigens. However, the unexpected reduction in protective efficacy of M. vaccae expressing the 19-kDa antigen highlights the complexity of testing recombinant subunit vaccines and the need for a better understanding of the immune mechanisms required for effective vaccination against tuberculosis.

[The tubercular process and antitubercular immunity in mice of different ages]

Experiments on "young" and "old" mice (aged, respectively, 2-4 and 22-24 months) infected with Mycobacterium tuberculosis, strain Bovinus-8, have revealed that in old mice the tuberculous process progresses at a faster rate than in "young" mice, which is manifested in "old" mice by their earlier death, more pronounced lesion of their internal organs and by a greater number of Mycobacterium colonies harvested after the inoculation of samples taken from their organs (after equal periods of incubation). In the process of the development of tuberculosis most immunity parameters are progressively suppressed, this suppression being more pronounced in the old animals and leading to a decrease in antibody-dependent cell cytotoxicity, the number of natural killer cells, the reaction of lymphocyte blast-transformation on PPD, cytotoxic effect on PPD-coated red blood cells, the synthesis of interleukin-1 and interleukin-2 after incubation with PPD, the titer of antituberculosis antibodies.

Behavior of attenuated mycobacteria in organs of neonatal and adult mice

The consequences of Calmette-Guérin bacillus (BCG) vaccination were followed in newborn and adult mice. BCG failed to multiply in the organs of adult mice when administered peritoneally. In contrast, extensive multiplication of the vaccine occurred in both splenic and pulmonary tissue after its peritoneal administration to newborn mice. This absence of tuberculostasis occurred during the period when the animal's spleen, lung, and thymus were rapidly growing. Animals achieved similar levels of resistance to virulent respiratory challenge 10 wk after vaccination irrespective of whether the vaccine had been administered when the mice were newly born and BCG had multiplied in vivo or administered when the animals were fully grown and the BCG had remained in the dormant state. Although neonatal infection with BCG was severe, as shown by the large numbers of organisms recovered from the animals' tissues, the animals suffered no mortality or overt signs of disease. Neonatal vaccination did not significantly affect either the animal's growth rate or the gross development of its organs.