Cellular immune response to common mycobacterial antigens in subjects seropositive for Trypanosoma cruzi

Antibody profiles induced by Trypanosoma cruzi in chagasic patients with previous or current exposure to mycobacteria

Since the immune response mounted by the host to a particular microorganism might be influenced by the acquired immunological experience due to previous contact with other microorganisms, we performed a cross-sectional study to explore the pattern of Trypanosoma cruzi infection-related antibodies in T. cruzi-seropositive individuals presenting concomitant tuberculosis, or the antecedent of BCG vaccination. Sampled individuals were grouped as follows: patients with Chagas disease, not vaccinated with BCG, who further developed pulmonary tuberculosis; individuals with Chagas disease, BCG-vaccinated; and subjects with Chagas disease, presenting neither BCG scar nor tuberculosis disease. Non-vaccinated individuals or without tuberculosis, presented the highest values of anti-PH (P < 0.001), anti-FRA (P < 0.001), anti-p2β (P = 0.0023) and anti-B13 (P < 0.001) antibodies. The present findings constitute the first demonstration of the potential influence of concomitant tuberculosis on Chagas disease.

Immunotherapy with Mycobacterium vaccae and peripheral blood flow in long-treated leprosy patients, a randomised, placebo-controlled trial

OBJECTIVE

to evaluate immunotherapy as a means of improving peripheral blood flow in chronic leprosy patients.

DESIGN

this was a double-blind, randomised, placebo-controlled, clinical trial.

MATERIALS

heat-killed Mycobacterium vaccae 1mg plus 0.02 microg Tuberculin protein per 0.1 ml dose in borate buffer, with saline as placebo. Those studied were 92 long-treated residents of a leprosy centre in Iran, 10 of their healthy children and 10 staff members. Evaluation employed the Perimed PF2, Laser-Doppler Flowmeter, a platinum skin thermistor, and a thermal sensibility tester.

METHODS

single intradermal injections of test or placebo were given to 103 patients 18 months before the blinded evaluation. Fingerpulp blood flux was measured in controlled conditions and vasomotor reflexes and skin sensation to touch, pain and heat were evaluated in 45 and 47 patients in the placebo and M. vaccae groups, respectively, and in 20 healthy control persons.

RESULTS

Laser-Doppler flux, skin temperature, vasomotor reflexes and sensation were impaired in leprosy patients. Immunotherapy improved (p < 0.05) Laser-Doppler flux, skin temperature and temperature sensation.

CONCLUSIONS

immunotherapy, given 18 months earlier, significantly improved blood flow and temperature sensation, in fully-treated, chronic, leprosy patients. The same principles might be employed in other conditions of reduced peripheral blood flow.

Seroprevalence of Helicobacter pylori infection in chronic chagasic patients, and in the rural and urban population from Uberlândia, Minas Gerais, Brazil

As patients with chronic Chagas disease exhibit morphological and functional changes of the stomach (hypomotility and hypochlorhydria), malnutrition, immunological deficiency and high prevalence of peptic disease associated to Helicobacter pylori infection, the purpose of this study was to evaluate if the prevalence of H. pylori infection in chronic chagasic is higher than in non-chagasic individuals in the urban and rural population from Uberlândia, MG, Brazil. Serological determination of IgG antibodies to H. pylori was performed using a second-generation ELISA. Thus, 598 people were evaluated: 128 chagasic (CG), 222 non-chagasic living in urban area (U-NCG) and 248 non-chagasic living in rural area (R-NCG). Regarding the age range from 21 to 50 years, the prevalence of H. pylori infection in the CG (85.1%) was significantly higher than in the U-NCG (56.3%, p < 0.01) and the R-NCG (67.4%, p < 0.05). In the patients over 50 years, the prevalence in the CG (86.4%) was similar to the U-NCG (78.8%) and R-NCG (86.1%). Similar results were also found between the U-NCG and R-NCG for all age ranges, with prevalence rates of 29.1% and 35.3% for the age range from 5 to 13 years, and 47.2% and 40% for that from 14 to 20 years, respectively. We conclude that chagasic patients showed a higher seroprevalence of H. pylori infection than non-chagasic individuals, in the age range from 21 to 50 years, and that the prevalence of this infection was similar in the studied urban and rural non-chagasic population.

Administration of interferon-g to pregnant rats reverses the depressed adjuvant-induced arthritis of their chronically Trypanosoma cruzi-infected offspring

We demonstrated that administration of interferon gamma (IFN-gamma) to the inbred "I" strain of pregnant rats conferred partial resistance on their offspring to challenge with Trypanosoma cruzi. We now examine if this intervention also modifies the reportedly immunodepressed cellular responses which occur during chronic infection. Offspring were born to mothers undergoing one of the following procedures during gestation: subcutaneous injections of recombinant rat IFN-gamma, 50,000 IU/rat, five times/week for 3 weeks, which was started on the day of mating (IFN-Mo); infection with 10(6) trypomastigotes of T. cruzi at 7, 14, and 21 days after mating plus IFN-gamma treatment as given to the former group (TcIFN-Mo); the same protocol except that physiological saline was injected instead of IFN-gamma (Te-Mo); injection of physiological saline only (control-Mo). All offspring groups (N = 8-10/group) were infected at weaning and were assessed 90 days later for their adjuvant-induced arthritic response or levels of major T cell subsets in spleen and lymph nodes. TcIFN-Mo and IFN-Mo offspring showed a reestablished arthritic response, which remained within the range seen in controls. Immunolabeling studies on parallel groups of 90-day-infected offspring showed that the inverse CD4/CD8 cell ratio that is usually seen in lymphoid organs from these chronically infected rats (median 0.61) appeared to have recovered in the TcIFN-Mo and IFN-Mo groups (median 1.66 and 1.78, respectively) and was not different from uninfected controls (1.96). These studies indicate that early stimulation with IFN-gamma is able to reverse the immunosuppressive state that is usually present during the chronic period of the experimental infection.

Vaccination of mice with a combination of BCG and killed Leishmania promastigotes reduces acute Trypanosoma cruzi infection by promoting an IFN-gamma response

The combination of BCG with killed Leishmania promastigotes, demonstrated to be efficient in the cure of patients suffering American cutaneous leishmaniasis and in the induction of a long-term immune response in healthy vaccinated volunteers, was tested in BALB/c mice infected with Trypanosoma cruzi, in comparison to BCG or Leishmania alone, and a vehicle (PBS) control. BCG-Leishmania vaccination, applied intra-peritoneally 10 and 3 days before T. cruzi trypomastigote inoculation, prolonged the survival, and reduced blood parasitaemia of infected animals. Proliferation studies indicated that splenocytes of mice vaccinated with BCG-Leishmania and harvested in the acute phase of T. cruzi infection displayed stimulation indices higher than cells from PBS-treated mice when stimulated with PHA mitogen, PPD, Leishmania or T. cruzi antigens. Injections of a monoclonal antibody able to neutralise IFN-gamma into BCG-Leishmania vaccinated mice increased parasitaemia to levels similar to those of control animals (treated with PBS) and reversed the beneficial effect of vaccination on the proliferative response to T. cruzi antigen. These results show that vaccination of mice with BCG plus killed Leishmania promastigotes delayed acute T. cruzi infection, stimulated a T-cell response to T. cruzi antigen and promoted IFN-gamma production.

Psoriasis patients have T-cells with reduced responsiveness to common mycobacterial antigens

Heparinised blood samples were obtained from 20 patients with chronic plaque psoriasis and from 13 age-matched healthy controls. After preliminary titration, mononuclear cells separated over Ficoll-Tryoson were cultured for 5 days with 10 microg ml(-1) of 15 mycobacterial preparations, or with pokeweed mitogen and concanavalin A. Stimulation indices were determined for each reagent and means were determined for patients and controls. Results for patients showed a striking reduction of responsiveness to mycobacteria, apparently due to loss of responses to group i, common mycobacterial antigens, and no differences in responses to mitogens. These observations relate psoriasis to certain other diseases, notably mycobacterial infections, rheumatoid arthritis, Chagas' disease and human immunodeficiency virus infection. The observations may be relevant to the aetiology of psoriasis, and to potential immunotherapy for the disease.

Trypanosoma cruzi-infected macrophages are defective in major histocompatibility complex class II antigen presentation

Trypanosoma cruzi, the intracellular protozoan parasite that causes Chagas' disease, interferes with the host immune response to establish a persistent infection. In this report, we demonstrate that macrophages infected with T. cruzi are unable to effectively present antigens to CD4 T cells. The interference is due to defective antigen-presenting cell (APC) function, as antigen-independent stimulation of the T cell in the presence of infected macrophages is not affected. The defect is distal to antigen processing and is not due to decreased major histocompatibility complex (MHC) class II expression, decreased viability, defective peptide loading in the infected macrophages, nor absence of CD28 co-stimulation. There was a role for gp39: CD40 co-stimulation during antigen presentation to the T cells we studied, but the expression of CD40 on T. cruzi-infected macrophages was not decreased. Antigen-specific adhesion between macrophages and T cells was reduced by infection. Equivalent levels of the adhesion molecules lymphocyte function-associated antigen-1, intercellular adhesion molecule-1, vascular cell adhesion molecule-1 or very late antigen-4 are found on infected and uninfected APC, suggesting that reduced expression of these adhesion molecules was not responsible for the defect in antigen-specific adhesion. The defective T cell:macrophage adhesion may be due to the reduced expression of other adhesion molecules or other changes in the cell induced by infection. Interfering with MHC class II antigen presentation in infected macrophages may help T. cruzi to blunt the immune response by the host.

Peptic disease and Helicobacter pylori are highly prevalent in patients with the indeterminate form of Chagas' disease: report of 21 cases

Given that chagasic patients in the indeterminate form of this disease, can have abnormal motility of the digestive tract and immunologic abnormalities, we decided to assess the frequency of peptic disease and Helicobacter pylori (Hp) infection in these individuals. Twenty-one individuals, 13 males and 8 females, mean age 37.6 +/- 11.1 years, were examined. Biopsies of the duodenum, antrum, lesser and greater gastric curvature and esophagus were performed. The endoscopic findings were of chronic gastritis in 20 (95.2%) patients, duodenal ulcer in 3 (14.3%), gastric and duodenal ulcer in 3 (14.3%), gastric ulcer alone in 1 (4.8%), esophagitis in 5 (23.8%), and duodenitis in 5 (23.8%). The diagnosis of infection by the Hp was done by the urease test and histologic examination. Hp infection was found in 20 (95.2%) individuals: in 20 out of them in the antrum, in 17 in the lesser curvature, and in 17 in the greater curvature. Hp was not found in the esophagus and duodenum. The only individual with no evidence of infection by Hp was also the only one with normal endoscopic and histologic examinations. The histologic examinations confirmed the diagnoses of gastric ulcer as peptic, chronic gastritis in 20 patients, duodenitis in 14, and esophagitis in 9. In this series the patients had a high frequency of peptic disease, which was closely associated with Hp infection.

Lack of skin test reactivity to common mycobacterial antigens in human immunodeficiency virus infected individuals with high CD4 counts

BACKGROUND

T cell response to mycobacterial antigens may be directed against those antigens common to all mycobacteria (group i), those restricted to slow (group ii) or fast growers (group iii), or those which are species- or subspecies-specific (group iv). These responses were assessed by skin testing patients infected with the human immunodeficiency virus (HIV) and healthy controls with reagents derived from different strains of mycobacteria.

METHODS

Skin test responses to new tuberculins prepared from Mycobacterium tuberculosis, M avium serotypes 4 and 8, and either M intracellulare or M flavescens antigens were evaluated prospectively in 51 HIV infected patients and 67 healthy controls.

RESULTS

Assessment of induration at 72 hours showed absence of skin test response to common mycobacterial antigens in all 27 HIV positive patients with CD4 counts of > or = 400/mm3 (range 400-1594, median 540) compared with 27% reactivity in controls; complete anergy was demonstrated in 24 patients with CD4 counts of < 400/mm3. By contrast, no difference in species or subspecies-specific responses was found between healthy controls and HIV positive patients with CD4 counts of > or = 400/mm3.

CONCLUSIONS

Subsets of CD4+ T helper cells are instrumental in determining the balance between cell-mediated and humoral immunity. One T helper subset (TH1) produces cytokines that increase cellular immunity and is stimulated by group i common mycobacterial antigens. Lack of this response, but preservation of responses to species-specific antigens while CD4 counts are near normal, may indicate an early failing of TH1 immunity and explain the increased susceptibility of HIV positive patients to mycobacterial infection early on in the evolution of their HIV infection.

NK and LAK functions in human chronic Chagas disease

Natural killer (NK) and lymphokine activated killer (LAK) functions were measured in 40 patients with chronic Chagas disease divided into asymptomatic/indeterminate (18) and symptomatic forms (22) and in 24 healthy controls. A chromium release assay was used employing K562 or P815 cell lines as targets. There was no difference in either NK or LAK activity between the three groups. A small number of patients in each group showed results above or below the normal range for controls. However, there was no correlation between NK and LAK values in the same individual. In conclusion, NK immunosuppression associated with human chronic Chagas disease.

Tuberculosis and cancer: parallels in host responses and therapeutic approaches?

Mycobacteria elicit two quite different immune responses. One is protective and is partly based on recognition and lysis of stressed, bacilli-laden cells expressing heat-shock proteins. The other suppresses this recognition and instead leads to indiscriminate necrosis of tissues containing mycobacteria (the Koch phenomenon). The type of response depends on the predominant T-cell maturation pathway, Th1 or Th2, which in turn is determined by priming by prior contact with environmental mycobacteria. Vaccination by BCG induces whichever response the recipient is primed to make, and this is a likely explanation of the variable efficacy of this vaccine in prevention of tuberculosis and therapy of cancer. Thus; BCG is a two-edged sword. We postulate that by using other mycobacterial preparations, such as killed Mycobacterium vaccae, it might be possible to suppress the indiscriminate necrosis and enhance Th1-regulated selective destruction of tumour cells.