Serum and aqueous humour cytokine response and histopathological alterations during ocular Toxoplasma gondii infection in C57BL/6 mice.

Toxoplasma gondii, an obligate intracellular protozoan parasite, infects most species of warm-blooded animals, and in humans it causes toxoplasmosis. Healthy people that become infected rarely present clinical symptoms because the immune system prevents the parasite from causing illness. Congenital toxoplasmosis may result in abortion, hydrocephalus, as well as neurological and ocular disease (most frequently retinochoroiditis) of the newborn. In immunocompromised patients, reactivation of latent disease can cause encephalitis. Cell-mediated immunity to T. gondii antigens involves innate acute inflammatory responses and antigen-specific adaptive immunity. Considering the complexity of the immunological events triggered during toxoplasmosis, systemic and local responses were evaluated by cytokine measurements. Aqueous humour and serum were obtained from non-infected and T. gondii Me-49 strain infected C57BL/6 mice for cytokine quantification. Histopathological analyses were made with eyes enucleated from mice after 30 days of infection. ELISA assays showed an increase of IFN-gamma levels both in serum and aqueous humour of infected mice in opposition to a decrease in IL-10 levels. On the other hand, TGF-beta was high, whereas IL-12 and TNF-alpha were present in small levels in both groups. We also detected higher levels of IL-4 and IL-6 in aqueous humour than in serum of infected mice when compared to the control group. MIP-2 presented no significant differences between the two groups. Fas and Fas-L were also present in similar levels in serum of non-infected and infected mice, but both chemokines were increased in the aqueous humour of infected mice. Histopathological analysis of infected mice showed inflammatory infiltrates around blood vessels and alteration of the outer photoreceptor segments, on the external and inner nuclear layer. Parasites were observed in 82% of eyes, inside the blood vessels associated with inflammatory infiltrate. Edema, characterized by the increase of interstitial spaces between the FTR, forming lacunae was also noted. These alterations take the form of projections (retino-vitreal), characteristic of retinochoroiditis. In conclusion, T. gondii infection of C57BL/6 mice revealed that cytokine patterns alone do not assure susceptibility or resistance against infection, thus reinforcing the notion that it is necessary more than cytokine dosage to determine Th1 or Th2 profile in this model.

Geographic diversity of adult t-cell leukemia/lymphoma in Brazil. The Brazilian ATLL Study Group.

We describe 195 cases of adult T-cell leukemia/lymphoma (ATLL) reported to the national registry of T-cell malignancies in Brazil between 1994 and 1998. We compared the effect of demographic differences and clinical features of 150 consecutive ATLL cases in different regions of this diverse country. At diagnosis, the predominant clinical sub-type was the acute type (60%), followed by lymphoma (22%), chronic (10%) and smoldering (8%) types. Although we expected that different sub-types would be present in different regions, on the basis of immunogenetic factors determined by ethnicity, we did not demonstrate these differences. There were no significant differences among ATLL subtypes by age or gender. No ethnic group predominated in the total population of patients, but significant differences were noted when examining ethnic distribution by region. Reflecting the general population distribution, white patients were seen more often in São Paulo and black patients in Bahia, than in other regions. In most regions, cases were equally distributed between blacks and mulattos, except in Pernambuco, where blacks were less frequent. The main clinical features were lymphadenopathy, skin lesions, hypercalcemia and hepatomegaly. Fourteen patients (9%) suffered from HTLV-I-associated myelopathy (HAM/TSP), either at diagnosis or during follow-up of ATLL. All cases but one had antibodies to HTLV-I, with concordant results with ELISA, WB and PCR analyses. For the antibody-negative case, pol and tax gene sequences were present in tumor cells when subjected to PCR analyses. The prognosis was generally poor, suggesting that the disease in Brazil behaves in similar fashion regardless of ethnic or geographical differences.

Frequent expansion of Epstein-Barr virus (EBV) infected cells in germinal centres of tonsils from an area with a high incidence of EBV-associated lymphoma.

Burkitt's lymphoma (BL) and Hodgkin's disease (HD) occurring in developing regions are frequently associated with Epstein-Barr virus (EBV) infection and have a high incidence in childhood. Recent genotyping studies indicate that the tumour cells of both neoplasms represent B cells that contain somatically mutated immunoglobulin heavy chain genes. This implies that the precursors of these neoplasms have participated in the germinal centre (GC) reaction. We therefore presumed that normal lymphoid tissues from children living in developing regions would harbour an increased number of EBV-infected cells within the GC, when compared with children living in industrialized nations. To test this hypothesis, hyperplastic tonsils from 40 children living in Bahia (Brazil) and 40 from German children were analysed for the presence of EBV-encoded small nuclear RNA (EBER) and EBV-encoded proteins by in situ hybridization and immunohistology, respectively. Although the overall EBV infection rate was similar in both groups (50 per cent of Bahian vs. 45 per cent of German cases), a significantly higher number of EBER-positive lymphoid cells were found in the GCs of 8/20 EBV-positive tonsils from Brazil (9-89 cells/GC; mean: 14.5 cells/GC per case), while only 3/18 tonsils from Germany displayed a few EBER positive cells (1-9 cells/GC; mean: 0.5 cell/GC per case) in this compartment (p < 0.007). In addition, the EBV-infected GC cells in Bahian samples resembled centroblasts, exhibited mitotic activity, and in two cases showed expression of EBV-encoded latent membrane protein (LMP)-1, findings not present in German samples. These data show that latently EBV-infected cells participate more frequently in GC reactions in developing regions than in industrialized countries and may abnormally express the oncogenic protein LMP-1. This could in part explain the higher incidence in this region of EBV association with lymphomas related to GC cells or their progeny, such as BL and HD.

Adult T-cell leukemia/lymphoma in northeastern Brazil: a clinical, histopathologic, and molecular study.

The state of Bahia in the northeastern coast of Brazil is a region in which HTLV-I infection is endemic. This study investigated the characteristics of 28 HTLV-I-associated lymphomas/leukemias in this region. HTLV-I-infection diagnosis was based on serologic study, Southern blot analysis, and polymerase chain reaction (PCR) in neoplastic tissue. The main clinical differences between these lymphomas and adult T-cell leukemia (ATL) cases from other endemic areas were as follows. The mean age was 47 years; 20% of the cases occurred in young adults; and a predominance was found among male subjects (2:1), blacks, and of those of mixed race (96%). Histologically, 20 cases were T-cell pleomorphic leukemia/lymphoma, 5 were Mycosis fungoides-like cutaneous lymphoma, and 3 were CD30+ large-cell anaplastic lymphoma. Immunohistochemistry demonstrated 4 cases of CD8+ lymphoma. Proviral genomic sequences were demonstrated by PCR in 9 lymph node biopsy specimens and in 3 skin biopsy specimens. Southern blot was performed and was positive in 8 cases.

Trypanosoma cruzi: resistance to the pore forming protein of cytotoxic lymphocytes--perforin.

The pore-forming protein perforin is one of the main effector molecules which cytotoxic lymphocytes utilize to kill their targets both in vivo and in vitro. Natural killer cells and cytotoxic T lymphocytes play an important role in host defense against a number of intracellular microorganisms such as virus and protozoan, but the exact way they help control infection is unknown. On the other hand, many microorganisms have evolved successful escape strategies to avoid immune-cell-mediated attack. It is thus necessary to investigate the direct interaction of infectious microorganisms with the lytic machinery of cytotoxic lymphocytes and other cells. In the present work we report the effect of perforin on both a protozoan, Trypanosoma cruzi, and the infected host cell. Epimastigote, amastigote, and trypomastigote forms of T. cruzi, as well as infected macrophages, were assayed for their susceptibility to perforin based on three different criteria. T. cruzi in all three differentiation stages were resistant to purified perforin at doses up to 100-fold larger than that sufficient to kill susceptible tumor cells. No morphological change was observed under electron microscopy. Survival rates and infectivities of the treated parasites in vitro were similar to those of control parasites. Moreover, the measurement of calcium influx using Fura-2 to assess membrane damage revealed that T. cruzi resist perforin attack by avoiding transmembrane pore formation. Resistance to perforin was not transferred to host cells since infected macrophages could be easily destroyed by perforin while intracellular amastigotes remained intact.

AIDS-related lymphoma in Brazil. Histopathology, immunophenotype, and association with Epstein-Barr virus.

The occurrence of malignant lymphoma is an increasingly important cause of morbidity and mortality in AIDS patients. The incidence of AIDS-related lymphoma in some developing countries such as Brazil is increasing as the survival of HIV infection has improved. Although there is a clear association between several types of immunodeficiency-related lymphomas and Epstein-Barr virus (EBV), the association of EBV infection in AIDS-related lymphoma in Brazil, where the incidence of AIDS is high, is unknown. Formalin-fixed, paraffin-embedded tissue from 24 cases of AIDS-related lymphoma in Brazil were analyzed for morphologic classification, immunophenotype, and EBV association using in situ hybridization studies with an EBV-EBER1 biotinylated probe. Twenty cases of AIDS-related lymphoma were classified as non-Hodgkin's lymphoma and four cases were Hodgkin's disease. Eleven non-Hodgkin's lymphomas were classified as diffuse large cell type, five cases were small non-cleaved cell, Burkitt-type, and four cases were large cell immunoblastic non-Hodgkin's lymphoma. Eighteen cases were of B-cell phenotype; one was a T-cell lymphoma, and one was classified as null. Epstein-Barr virus (EBV) was demonstrated in the majority of tumor cells of 11 of 20 (55%) of the cases non-Hodgkin's lymphomas and in 3 of 4 (75%) cases of Hodgkin's disease. AIDS-related lymphomas in Brazil are usually of large cell/immunoblastic type, but Hodgkin's disease is also seen. Both non-Hodgkin's lymphoma and Hodgkin's disease are often associated with EBV infection. The non-Hodgkin's lymphoma is predominantly of B-cell phenotype.

PIP: While there is a clear association between several types of immunodeficiency-related lymphomas and Epstein-Barr virus (EBV), the association of EBV infection in AIDS-related lymphoma in Brazil, where the incidence of AIDS is high, has remained unknown. The authors report their findings from an analysis of tissue samples from 24 cases of AIDS-related lymphoma in Brazil. The samples were analyzed for morphologic classification, immunophenotype, and EBV association. 20 cases were classified as non-Hodgkin's lymphoma, while 4 were Hodgkin's disease. 11 non-Hodgkin's lymphomas were classified as diffuse large cell type, 5 as small, non-cleaved cell, Burkitt-type, and 4 as large cell immunoblastic non-Hodgkin's lymphoma. 18 cases were of B-cell phenotype; one was a T-cell lymphoma and one was classified as null. EBV was demonstrated in the tumor cells of 11 of the 20 non-Hodgkin's lymphoma cases and in 3 of the 4 cases of non-Hodgkin's disease.

Trypanosoma cruzi recognition by macrophages and muscle cells: perspectives after a 15-year study.

Macrophages and muscle cells are the main targets for invasion of Trypanosoma cruzi. Ultrastructural studies of this phenomenon in vitro showed that invasion occurs by endocytosis, with attachment and internalization being mediated by different components capable of recognizing epi- or trypomastigotes (TRY). A parasitophorus vacuole was formed in both cell types, thereafter fusing with lysosomes. Then, the mechanism of T. cruzi invasion of host cells (HC) is essentially similar (during a primary infection in the absence of a specific immune response), regardless of whether the target cell is a professional or a non-professional phagocytic cell. Using sugars, lectins, glycosidases, proteinases and proteinase inhibitors, we observed that the relative balance between exposed sialic acid and galactose/N-acetyl galactosamine (GAL) residues on the TRY surface, determines the parasite's capacity to invade HC, and that lectin-mediated phagocytosis with GAL specificity is important for internalization of T. cruzi into macrophages. On the other hand, GAL on the surface of heart muscle cells participate on TRY adhesion. TRY need to process proteolytically both the HC and their own surface, to expose the necessary ligands and receptors that allow binding to, and internalization in the host cell. The diverse range of molecular mechanisms which the parasite could use to invade the host cell may correspond to differences in the available "receptors" on the surface of each specific cell type. Acute phase components, with lectin or proteinase inhibitory activities (alpha-macroglobulins), may also be involved in T. cruzi-host cell interaction.