Giovanni Gazzinelli

Cytokine Regulation of Human Immune Response to Schistosoma mansoni: Analysis of the Role of IL‐4, IL‐5 and IL‐10 on Peripheral Blood Mononuclear Cell Responses

The role of cytokines on the in vitro proliferative response of peripheral blood mononuclear cells (PBMC) from Schistosoma mansoni infected patients to soluble egg (SEA) and adult worm antigens (SWAP) were evaluated. The results obtained demonstrated that the proliferative response of PBMC from chronic intestinal (INT) patients to SEA and SWAP is increased by the blockage of IL‐10 with specific monoclonal antibodies (MAb). The effects of these antibodies were readily reversed by the addition of recombinant IL‐10. In contrast, no effect was observed on the PBMC response of acute and hepatosplenic patients (HS) in the presence of anti‐IL‐10. Anti‐IL‐4 antibodies decreased the PBMC response of the intestinal (INT) and HS individuals to SEA and SWAP, and the PBMC response of acute patients to SEA but not to SWAP. Addition of anti‐IL‐5 MAb did not decrease the PBMC response of acute patients to SEA or SWAP. These results suggested that IL‐10 has an important role in the modulation of the immune response in chronic asymptomatic patients and that this cytokine may be an important factor in controlling morbidity.

CHAGASIC PATIENTS LACK CD28 EXPRESSION ON MANY OF THEIR CIRCULATING T LYMPHOCYTES

A balanced host‐parasite interaction during Trypanosoma cruzi infection allows for the establishment of a chronic infection that can last for many years. T cells are a major element responsible for parasite specific and non‐specific immunityduring the complex immune response of the host. However, the sub‐populations of T cells involved in the response, as well as the exact mechanisms through which those cells are activated or rendered unresponsive, are not well defined. It is known thatco‐stimulatory signals, some of which are mediated via CD28, are of critical importance in the triggering of appropriate T cell responses. In this study the authors performed double‐labelling studies to determine the frequency of expression of CD28 byCD4+ and CD8+ T lymphocytes in the peripheral blood of patients with Chagas’ disease. The results show that chagasic patients throughout the spectrum of chronic clinical forms of the infection have significantly higher meanfrequencies of CD4+CD28– and CD8+CD28– T cells, as compared with non‐chagasic individuals. Considering the importance of CD28 for T‐cell activation, the observed down‐regulation or loss of CD28during infection may indicate a possible basis for observed immunoregulatory events or distinct stages of T‐cell activation in this infection. Recent evidence from patients with HIV/AIDS indicates that CD28– cell populations are morelikely to undergo apoptosis, and increased apoptosis has been observed in experimental Chagas disease.

Large-Scale Laboratory Maintenance of Schistosoma mansoni, with Observations on Three Schistosome/Snail Host Combinations

This review discusses the large-scale laboratory maintenance of Schistosoma mansoni. Emphasized are features which increase efficiency in such facilities, and problems most frequently encountered. Profiles are given of the long-term, high-level production of 3 strains of S. mansoni. Two of the strains, NMRI and PR-1, were of Puerto Rican origin and the other, LE, was from Brazil. Three to 8 million cercariae of each strain were usually obtained per week. The most obvious differences between the 3 strains were cercarial output per snail and snail mortality rates. Maintenance problems encountered were usually related to water quality, temperature, genetics of the parasite or snail host, predators or contaminants, feeding, or crowding of snails. Examination of the production data from these 3 life cycles led to identification of features that could be of benefit for increasing the productivity and efficiency of other S. mansoni life cycles used in research activities.

Cytokine production associated with periportal fibrosis during chronic schistosomiasis mansoni in humans

ABSTRACT Volunteers living in an area where schistosomiasis mansoni is endemic were subjected to ultrasound examination and classified into groups according to the levels of fibrosis diagnosed, namely, absence of indications of fibrosis (group 0), incipient fibrosis (group 1), and moderate/severe fibrosis (group 2). Peripheral blood mononuclear cells (PBMC) collected from the volunteers were stimulated with soluble antigens from adult schistosomes or from schistosome eggs, and the production of the cytokines gamma interferon, tumor necrosis factor alpha, transforming growth factor β (TGF-β), interleukin-4 (IL-4), IL-10, and IL-13 was determined. Potential associations of the level of fibrosis with age, sex, intensity of infection, and cytokine production were investigated between the three groups. Univariate analysis identified associations of age (>50), gender (male), and absence of eggs/g of feces with moderate/severe fibrosis and an association of intensity of infection (>100 eggs) with incipient fibrosis. When cytokine production in PBMC cultures stimulated by soluble egg antigens was categorized as low or high, significant differences in the distribution of IL-13 levels were established between groups 0 and 2. No significant differences were detected between the groups in the cytokines produced by PBMC cultures stimulated with soluble antigens from adult schistosomes. When all variables were tested in multivariate analyses, only IL-13 was strongly associated with fibrosis (odds ratio = 5.8; 95% confidence interval [CI] = 1.1 to 30.5). While high levels of TGF-β appeared to be associated with protection against fibrosis, the strength of the association was low.

Natural versus Drug-induced Resistance in Schistosoma mansoni Infection

Rodrigo Corrêa-Oliveira, Iramaya Rodrigues Caldas and Giovanni Gazzinelli here focus on the immune response of individuals with natural resistance to schistosomiasis, which differs significantly from that of post-treatment resistant and infected individuals. They suggest that the activation of T helper type 1 (Th1) and Th2 cells is needed for the induction of natural resistance against Schistosoma mansoni infection.

Analysis of anti-keyhole limpet haemocyanin antibody in Brazilians supports its use for the diagnosis of acute schistosomiasis mansoni

Antibody (immunoglobulin (Ig) G) to the haemocyanin of the keyhole limpet (KLH) (Megathura crenulata), which shares a well defined carbohydrate epitope with the surface of schistosomula of Schistosoma mansoni, was determined by enzyme-linked immunosorbent assay (ELISA) in the sera of Brazilians with acute schistosomiasis. Of 53 such individuals tested, 51 had a level of KLH reactivity in excess of the mean +2 standard deviations of that exhibited by chronically infected individuals. This difference in reactivity allowed the acute cases to be readily identified by visual inspection of ELISA plates. The levels of IgG in patients with hepatointestinal and hepatosplenic schistosomiasis, as well as in non-infected, seropositive residents of endemic areas and infected children from endemic areas, were not statistically different from those of intestinal patients. Significant levels of anti-KLH IgG were not detected in patients with leishmaniasis, Chagas disease, ancylostomiasis or ascariasis. The results support the use of KLH as a means of rapidly and easily identifying individuals with acute schistosomiasis.

Comparison of antibody isotype responses to Schistosoma mansoni antigens by infected and putative resistant individuals living in an endemic area

The isotypic patterns of antibodies against Schistosoma mansoni antigenic preparations from eggs (SEA), adult worms (SWAP) andcercariae (CERC) have been studied in sera from two groups of individuals living in an area endemic for S. mansoni. One of the groups was comprised of individuals diagnosed as having S. mansoni infections based on their patency, i.e. those passing eggs in their faeces (patent infections, PI). The other group has been consider ‘putatively resistant’ due to their residence in an endemic area, their documented exposure to positive transmission sites, and their repeated negativity upon stool examinations (endemic normals, EN). There are strong specific responses oflgGl, IgG4 and IgM, particularly to SEA and CERC, by both groups. The reactivities of all isotypes were lower to SWAP. The responses of IgG4, IgM and IgE anti‐CERC in EN and PI are higher than those found in normal individuals from outside endemic areas. In general, EN individuals express a relative higher level of anti‐STEG IgE as compared to IgG4. On the other hand the pool of sera from PI showed the opposite pattern of higher IgG4 as compared to IgE. Several correlations are seen between isotypic responses to SEA, SWAP and CERC based on comparisons to the anti‐SWAP IgE responses of the individuals in the two groups. These comparisons indicate the presence of distinct immunologic differences between individuals in the PI and the EN groups.,

The human immune response to defined immunogens of Schistosoma mansoni: elevated antibody levels to paramyosin in stool-negative individuals from two endemic areas in Brazil

Sera from individuals living in 2 areas endemic for Schistosoma mansoni in Minas Gerais, Brazil were assayed for the presence of antibodies against paramyosin and glutathione-S-transferase (GST), molecules previously implicated as vaccine immunogens from studies in laboratory hosts. A group was identified consisting of subjects who were stool-negative and had no record of previous infection but who were seropositive by enzyme-linked immunosorbent assay against crude adult worm antigen (SWAP). These individuals had anti-paramyosin antibody levels which were dramatically elevated with respect to those measured in infected (stool-positive) individuals living in the same endemic area. In contrast, the same 2 groups of stool-positive and stool-negative subjects could not be distinguished on the basis of their seroreactivity to either GST or SWAP. After chemotherapy, anti-paramyosin antibodies rose above pre-treatment levels and remained elevated in those individuals who became stool-negative. In contrast, anti-paramyosin antibodies decreased to pretreatment values in drug-treated individuals who failed to show complete parasitological cure. These results suggest that the immune response of humans to paramyosin may play a role in natural resistance to schistosome infection, and that an elevated antibody level against this antigen may be a useful correlate of drug-induced cure.

Direct lysis of Trypanosoma cruzi: a novel effector mechanism of protection mediated by human anti-gal antibodies.

Summary Anti‐gal antibodies directed against a carbohydrate epitope present in mouse laminin (galactosyl α 1‐3 galactose) and detected in high levels in sera from patients in the acute phase of Chagas disease are responsible for the direct lysis (DL) of Trypanasoma cruzi blood forms independent of either the classic or alternative complement pathways. Furthermore, the lectins Euonymus europaeus (EE) specific for the carbohydrates gal α1‐3 gal present a similar lytic activity against T. cruzi at the same concentrations of purified anti‐gal antibodies. The DL activity was tested with several other lectins but Concanavalin A (Con A) specific for α‐D‐mannose and α‐D‐glucose was the only one also presenting lytic activity. The lectins and anti‐gal antibodies lytic activity can be inhibited by specific carbohydrates suggesting that this phenomenon is related to the capability of these lectins or anti‐gal antibodies to bind to a crucial surface component of T. cruzi. Moreover, the infectivity of T. cruzi blood forms to mice was clearly inactivated by incubation with acute chagasic sera (ACS) but not by ACS absorbed by immunoaffinity chromatography with mouse laminin, a strong evidence that high levels of anti‐gal antibodies participate in the decline of the parasitaemia from the acute to the chronic phase in Chagas disease.

The role of the immune response on the development of severe clinical forms of human Chagas disease

Centro de Pesquisas Rene Rachou-Fiocruz, Av. Augusto de Lima 1715, 30190-002 Belo Horizonte, MG, Brasil *Departamento de Bioquimica e Imunologia, ICB **Departamento de Morfologia, ICB-UFMG, Av. Antonio Carlos 6627, 31270-010 Belo Horizonte, MG Brasil ***Faculdade de Medicina do Triângulo Mineiro, Uberaba, MG, Brasil ****Faculdade de Medicina/Hospital das Clinicas, UFMG, Av. Alfredo Balena 190, 30130-100 Belo Horizonte, MG, Brasil ****Laboratorio de Biologia do Reconhecer, Universidade Estadual Norte Fluinense, Campos dos Goytacazes, RJ, Brasil