Immunogenicity of multiple antigen peptides containing Plasmodium vivax CS epitopes in BALB/c mice

Multiple antigen peptide systems (MAPs) allow the incorporation of various epitopes in to a single synthetic peptide immunogen. We have characterized the immune response of BALB/c mice to a series of MAPs assembled with different B and T cell epitopes derived from the Plasmodium vivax circumsporozoite (CS) protein. A B-cell epitope from the central repeat domain and two T-cell epitopes from the amino and carboxyl flanking regions were used to assembled eight different MAPs. An additional universal T cell epitope (ptt-30) from tetanus toxin protein was included. Immunogenicity in terms of antibody responses and in vitro T lymphocyte proliferation was evaluated. MAPs containing B and T cell epitopes induced high titers of anti-peptides antibodies, which recognized the native protein on sporozoites as determined by IFAT. The antibody specificity was also determined by a competitive inhibition assay with different MAPs. A MAP containing the B cell epitope (p11) and the universal epitope ptt-30 together with another composed of p11 and the promiscuous T cell epitope (p25) proved to be the most immunogenic. The strong antibody response and specificity for the cognate protein indicates that further studies designed to assess the potential of these proteins as human malaria vaccine candidates are warranted.

Infection of Oxydoras kneri Bleecker, 1862 (Pisces, Doradidae) by the acanthocephalan Paracavisoma impudica (Diesing, 1851) Kritcher, 1957

Infection of Oxydoras kneri by the acanthocephalan Paracavisoma impudica is described. The parasites do not penetrate deeply into the host gut wall and do not reach the muscularis layers. Host reaction is minimal, consisting of limited fibrosis around the proboscides. Haemorrhages and lymphocyte infiltration are not observed, and phagocytic cells are only present occasionally. Oxydoras kneri is a newly reported host for Paracavisoma impudica.

Laboratory indicators for monitoring HIV disease

Immunological monitoring of disease progression following HIV infection and seroconversion illness, latency and AIDS, not only helps in the basic investigation of the natural history of the viral infection in man, but also can assist in prognosis and treatment of AIDS-defining illnesses. However, outside clinical trials, these tests should be selected and used in clinical practice only if they are validated as relevant and effective. The absolute CD4+ T-helper lymphocyte count, measured by flow cytometry, has emerged as the best available investigation, but needs care in sampling due to diurnal and circadian rhythms, effects of age, pregnancy, therapy, intercurrent infections and technique. Sampling should provide a baseline and trends - monthly intervals initially, then quarterly in uncomplicated cases. Thresholds may be given for counts (e.g. 200/µl) below which prophylaxis against pneumocystis pneumonia should be administered, and repeating persistently low counts (e.g. below 50/µl) is seldom helpful in practice. Serum levels of beta-2 microglobulin, neopterin and immunoglobulins rarely add information. Physicians and laboratories should have testing guidelines based on clinical audit of best practice, based in turn on scientific understanding of the immunological processes involved.

Tuberculin Skin Test and CD4+/CD8+ T Cell Counts in Adults Infected with the Human Immunodeficiency Virus in Medellín, Colombia

To evaluate the effect of BCG vaccination and T lymphocyte subpopulations on the reactivity to the tuberculin skin test, 113 asymtomatic HIV+ individuals were tuberculin tested by intradermal injection of 5TU of purified protein derivative and the levels of circulating lymphocyte (CD3, CD4 and CD8) subpopulations determined by indirect immunofluorescence. Ninety-two percent of the subjects included in the study were males. The mean age of the group was 32.1±7.4 years. Sixty-two percent presented a BCG scar. However, only 22% exhibited positive tuberculin reactions (³5mm) irrespective of the presence of the BCG scar. Tuberculin positive individuals exhibited higher CD4+ cell counts (p=0.004) and CD4+/CD8+ ratios (p=0.006) than tuberculin negative (<5mm) HIV+ individuals. The number of individuals with positive tuberculin reactions was significantly higher in subjects with more than 500 CD4+ lymphocytes/ml (p=0.02) or CD4+/CD8+ ratios ³1.12 (p=0.002). These results suggest that a prior BCG vaccination does not influence the reactivity to the tuberculin skin test in HIV+ asymptomatic individuals and that the number of CD4+ lymphocytes and the CD4+/CD8+ ratio positively correlate with the tuberculin reactivity

Impact of Antifibrotic Treatment on the Course of Schistosoma mansoni Infection in Murine Model

Administration of an antifibrotic agent as an adjunct to antihelmintic treatment with the objective of morbidity reduction was investigated in the murine schistosomiasis mansoni model. Antifibrotic, ß-aminopropionitrile treatment has a profound effect on the cellular matrix composition of the liver granuloma of Schistosoma mansoni infected mice when given alone, resulting in increase macrophage infiltration. These macrophages, in response to stimulation with soluble egg antigen or lipopolysaccharide produced elevated levels of nitric oxide but low levels of tumor necrosis factor alpha compared to untreated infected mice. This also correlated with reduced liver granuloma size. In spite of low numbers of eggs in the liver, mice receiving a combine treatment had a high level of resistance to a challenge infection compared with mice receiving only praziquantel. Those mice also exhibited a reduced lymphocyte proliferative response, similar to that of infected untreated mice. Antifibrotic treatment has an impact on the dynamic of the cellular nature of granulomas and impacts on the host immunity to infection

A role for lymphocytes and cytokines on the eosinophil migration induced by LPS

In the present work we review the existing evidence for a LPS-induced cytokine-mediated eosinophil accumulation in a model of acute inflammation. Intrathoracic administration of LPS into rodents (mice, rats or guinea pigs) induces a significant increase in the number of eosinophils recovered from the pleural fluid 24 hr later. This phenomenon is preceded by a neutrophil influx and accompanied by lymphocyte and monocyte accumulation. The eosinophil accumulation induced by LPS is not affected by inhibitors of cyclo or lipoxygenase nor by PAF antagonists but can be blocked by dexamethasone or the protein synthesis inhibitor cycloheximide. Transfer of cell-free pleural wash from LPS injected rats (LPS-PW) to naive recipient animals induces a selective eosinophil accumulation within 24 hr. The eosinophilotactic activity present on the LPS-PW has a molecular weight ranging between 10 and 50 kDa and its effect is abolished by trypsin digestion of the pleural wash indicating the proteic nature of this activity. The production of the eosinophilotactic activity depends on the interaction between macrophages and T-lymphocytes and its effect can not be blocked by anti-IL-5 monoclonal antibodies. Accumulated evidence suggest that the eosinophil accumulation induced by LPS is a consequence of a eosinophilotactic cytokine produced through macrophage and T-cell interactions in the site of a LPS-induced inflammatory reaction.

Description of an in vivo model for the assessment of eosinophil chemoattractants in the mouse

Chemokines (chemoattractant cytokines) induce potent and selective chemotaxis of leukocyte subsets in vitro. Here, we review briefly the chemokines shown to induce eosinophil chemotaxis in vitro and describe a novel model for the study of the ability of chemokines to stimulate eosinophil migration in vivo. Eosinophils were purified from the blood of mice over-expressing the IL-5 gene and labelled with 111In. Only the C-C chemokines, eotaxin and MIP-1alpha, but not RANTES, MCP-1, MCP-3, MCP-4, MIP-1ß, KC and MIP-2, effectively induced the recruitment of 111In-eosinophils in mouse skin. We suggest that this mouse model will be useful in assessing the role of endogenously-generated chemokines in mediating eosinophil migration to sites of allergic inflammation in vivo.

Chagas' Disease and HIV Co-infection: Genotypic Characterization of the Trypanosoma cruzi Strain

In the past few years, new aspects of the immunopathology of Chagas' disease have been described in immunosuppressed patients, such as fatal central nervous system lesions related to the reactivation of the parasite. This article is the first description of the genotypic characterization, at the strain level, of Trypanosoma cruzi isolated from a patient with Chagas` disease/AIDS co-infection. The presence of four hypodense lesions was observed in the cranial compute tomographic scan. The diagnosis of AIDS was assessed by the detection of anti-HIV antibodies using enzyme-linked immunosorbent assay (ELISA) and Western blot techniques. The CD4+ lymphocyte counts were maintained under 200 cells/mm3 during one year demonstrating the severity of the state of immunosuppression. Chagas' disease was confirmed by serological and parasitological methods. Trypomastigote forms were visualized in a thick blood smear. The parasite isolated is genotypically similar to the CL strain. The paper reinforces that cerebral Chagas' disease can be considered as another potential opportunistic infection in AIDS resulting from the reactivation of a dormant T. cruzi infection acquired years earlier.

Immune Dysfunction and the Pathogenesis of AIDS-associated non-Hodgkin's Lymphoma

Much has been learned about how HIV-induced immune dysfunction contributes to B cell hyperactivation, and potentially, to the pathogenesis of AIDS-lymphoma. However, further studies are needed to fully understand how HIV infection and immune dysfunction promote B cell hyperactivation and the development/growth of AIDS-lymphoma. In particular, studies are needed to define the role of HHV8 vIL6, IL6 receptor-expression, and lymphocyte surface stimulatory molecules, in promoting B cell hyperactivation or lymphoma cell growth.

Adenosine Deaminase Activities in Sera, Lymphocytes and Granulocytes in Patients with Cutaneous Leishmaniasis

Adenosine deaminase (ADA) activities in sera, lymphocytes and granulocytes in patients with cutaneous leishmaniasis were investigated and compared with control groups. Fifty patients and 50 healthy individuals were studied. The clinical diagnosis was parasitologically confirmed by culture and Giemsa stain. ADA activities were measured by colorimetric method. Serum ADA activities 37.80 ± 11.90, 18.28 ± 6.08 IU/L (p<0.0001), lymphocyte specific ADA activities 14.90 ± 7.42, 8.38 ± 7.42 U/mg protein (p = 0.04), granulocyte specific ADA activities 1.15 ± 0.73 , 1.09 ± 0.67 U/mg protein ( p>0.05) were found in patients and control groups, respectively. ADA activity increases in some infectious diseases were cell mediated immune mechanisms are dominant. In cutaneous leishmaniasis, lymphokine-mediated macrophage activity is the main effector mechanism. Increase in serum and lymphocyte ADA activities in patients with cutaneous leishmaniasis may be dependent on and reflects the increase in phagocytic activity of macrophages and maturation of T-lymphocytes.

The spleen is an important site of T cell activation during human hepatosplenic schistosomiasis

We have undertaken a comparative immunephenotypic study of spleen cells from hepatosplenic patients (HS) and uninfected individuals (NOR) using flow cytometry. Our data did not show any significant differences in the mean percentage of T-cells and B-cells between the two groups. Analysis of activated T-cells demonstrated that HS present an increased percentage of CD3+HLA-DR+ splenocytes in comparison to NOR. Analysis of T-cell subsets demonstrated a significant increase on the percentage of both activated CD4+ T-splenocytes and CD8+ cells in HS. We did not find any difference in the mean percentage of CD28+ T-cells. Analysis of the B-cell compartment did not show any difference on the percentage of B1-splenocytes. However, the spleen seems to be an important reservoir/source for B1 lymphocytes during hepatosplenic disease, since after splenectomy we found a decreased the percentage of circulating B1-lymphocytes. We observed an increase on the percentage of CD2+CD3- lymphocytes in the spleen of HS suggesting that the loss of CD3 by activated T-cells or the expansion of NK-cells might play a role in the development/maintenance of splenomegaly.

T Cell Response of Asymptomatic Leishmania chagasi Infected Subjects to Recombinant Leishmania Antigens

In areas of Leishmania chagasi transmission the ability to control leishmania infection is associated with IFN-g production. In visceral leishmaniasis down-regulation of T cell responses is mediated by interleukin-10 (IL-10). In this study we evaluated the lymphoproliferative response, IFN-g and IL-10 production on lymphocyte cultures stimulated with recombinant leishmania antigens in subjects with asymptomatic L. chagasi infection. There was a statistically significant difference in the lymphoproliferative response of the subjects with asymptomatic infection as compared to patients with visceral leishmaniasis and healthy subjects with respect to crude antigens (p<0.01), gp-63 (p<0.05) and hsp-70 (p<0.01), as well as between asymptomatic L. chagasi infected subjects and patients with visceral leishmaniasis with respect to the response to all antigens tested. The IFN-g production observed in the group with asymptomatic infection with all the three recombinant antigens tested was higher (p<0.01) than that observed in patients with visceral leishmaniasis and in healthy subjects. Furthermore, in individuals with asymptomatic infection, IL-10 levels in cultures stimulated with recombinant antigens were very low. This study shows that lymphocytes from individuals with asymptomatic L. chagasi infection are able to recognize recombinant leishmania antigens with production of a cytokine that is associated with leishmania killing.

Comparison between Human Immunodeficiency Virus Positive and Negative Patients with Tuberculosis in Southern Brazil

The objective of this study is to determine the different characteristics of human immunodeficiency virus (HIV) positive and negative patients treated for tuberculosis (TBC) in a tertiary hospital in Southern Brazil. We conducted a retrospective cohort study over a 5-year period, from January 1992 through December 1996. We reviewed medical charts of patients from our institution who received TBC treatment. We reviewed 167 medical charts of patients with confirmed TBC. HIV positivity was detected in 74 patients. There were statistically significant difference between HIV positive and negative patients in sex and age. HIV-infected patients showed significantly more signs of bacteremia than HIV-negative patients. Extra-pulmonary TBC was present respectively in 13 (17.6%) and 21 (22.6%) HIV positive and negative patients. There was a significant difference between chest radiograph presentation in HIV positive and negative patients. There were significantly lower hematocrit, hemoglobin, leukocyte and lymphocyte levels in HIV-positive compared to HIV-negative patients. Outcome was significantly different in the two groups with a death rate of 36.5% and 10.8% in HIV-positive and in HIV-negative patients. The difference between HIV positive and negative patients may have importance in the diagnosis, management and prognosis of patients with TBC.

Cell populations in lesions of cutaneous leishmaniasis of leishmania (L.) amazonensis- infected rhesus macaques, Macaca mulatta

The cellular nature of the infiltrate in cutaneous lesion of rhesus monkeys experimentally infected with Leishmania (L.) amazonensis was characterized by immunohistochemistry. Skin biopsies from infected animals with active or healing lesions were compared to non-infected controls (three of each type) to quantitate inflammatory cell types. Inflammatory cells (composed of a mixture of T lymphocyte subpopulations, macrophages and a small number of natural killer cells and granulocytes) were more numerous in active lesions than in healing ones. T-cells accounted for 44.7 ± 13.1% of the infiltrate in active lesions (versus CD2+= 40.3 ± 5.7% in healing lesions) and T-cell ratios favor CD8+ cells in both lesion types. The percentage of cells expressing class II antigen (HLA-DR+) in active lesions (95 ± 7.1%) was significantly higher (P < 0.005) from the healing lesions (42.7 ± 12.7%). Moreover, the expression of the activation molecules CD25 (@ 16%), the receptor for interleukin-2, suggests that many T cells are primed and proliferating in active lesions. Distinct histopathological patterns were observed in lesions at biopsy, but healing lesions contained more organized epithelioid granulomas and activated macrophages, followed by fibrotic substitution. The progression and resolution of skin lesions appears to be very similar to that observed in humans, confirming the potential for this to be used as a viable model to study the immune response in human cutaneous leishmaniasis.

Detection of intracytoplasmic cytokines by flow cytometry

Flow cytometry has been used as a powerful technique for studying cell surface antigen expression as well as intracellular molecules. Its capability of analyzing multiple parameters simultaneously on a single cell has allowed identification and studies of functional cell subsets within heterogeneous populations. In this respect, several techniques have been developed during the past few years to study cytokine-producing cells by flow cytometry in humans and several animal models.