After defining some concepts, this chapter specifies the epidemiological features of this peculiar transmission mode of Trypanosoma cruzi. The possible maternal–fetal routes, the placental responses to parasite infection and the timing of transmission are reviewed in depth. The factors susceptible to be involved in parasite transmission and development of congenital Chagas disease, such as parasite genotypes and maternal and fetal immune responses, are discussed in detail. Information obtained from vertical transmission in other mammals is also examined. T. cruzi congenital infection is frequently asymptomatic, whereas reported symptoms are nonspecific, and severe and mortal clinical forms are mainly observed in case of maternal coinfection with HIV. The long-term consequences of congenital infection, such as the transgenerational transmission and the imprinting of neonatal immune system are also mentioned. The diagnosis of infection in pregnant women requires standard serological investigations. The laboratory diagnosis in newborns of positive mothers includes the use of parasitological techniques at birth or in the first months of life (though of limited sensitivity, these tests indisputably confirm the presence of live parasites) and/or standard serological investigations 8 months after birth, when maternal transmitted antibodies have disappeared. The conditions of using polymerase chain reaction (detecting parasitic DNA and not live parasites) are discussed in depth. All diagnosed congenital cases have to be treated before 1 year of age in order to cure them without side effects. Since the treatment of infected pregnant women is not recommended, the control strategy of congenital infection refers to its systematic detection in newborns of infected mothers by the means mentioned above.

In vivo administration of Canavalia brasiliensis lectin (at the time of infection, or maintained throughout the infection) reduced the lesions of highly susceptible BALB/c mice infected by Leishmania amazonensis. At the doses used C. brasiliensis lectin (ConBr) does not interfere with penetration or fate of Leishmania in the macrophages in vitro. Since Interferon-gamma (IFN-gamma) is the major macrophage activating factor, and considered a critical element in the successful immune response against leishmaniasis, we explored its participation in this phenomenon. ConBr either in vivo or in vitro induced IFN-gamma production in normal or in leishmania-infected BALB/c mice. However we were unable to change the course of disease by in vivo IFN-gamma administration (although IFN-gamma preparations were effective in inducing a leishmanicidal effect in vitro on L. amazonensis-infected peritoneal macrophages). Additionally, IFN-gamma neutralization with anti-IFN-gamma monoclonal antibody did not alter the protection conferred by ConBr administration. These data show that lectin administration in vivo is protective in the otherwise unchecked L. amazonensis infection of BALB/c mice, and suggest that such effect is not mediated by IFN-gamma.

In an open trial, longer courses of pentavalent antimonials (Sbv) at sub-optimal doses (10 mg/kg body weight), in association with recombinant human interferon-gamma (IFN-gamma) (100 micrograms/m2 of body surface area) were administered, by daily intramuscular injections, to 13 patients with diagnoses of cutaneous or mucocutaneous leishmaniasis unresponsive to Sbv. Four patients presented with large skin ulcers, and 9 had mucosal involvement as the main manifestation, the latter affecting the nose (3 cases), nose and septum (2 cases), nose and oral cavity (1 case), and nose, pharynx and larynx (3 cases). Except for one case with severe involvement of the upper respiratory tract, the lesions were fully resolved by the end of therapy (mean duration 40 +/- 12 [SD] d, range 30-60 d) in the 11 patients who completed therapy. The main side effects were headache and fever (7 cases), together with leucopenia and eosinophilia (4 cases). It is concluded that combined administration of low doses of Sbv plus IFN-gamma may provide a novel therapeutic approach for the treatment of antimony-resistant cutaneous or mucocutaneous leishmaniasis. The possible mechanisms by which IFN-gamma contributes to resolution of the disease are discussed.

T lymphocytes from patients with visceral leishmaniasis treated in vitro with leishmania antigens are unable to proliferate and to produce gamma interferon. These patients have negative specific skin tests. Opposite results are obtained in patients with another clinical form of the disease named mucocutaneous leishmaniasis, in which both tests are positive. Nevertheless, patients with visceral leishmaniasis or mucocutaneous leishmaniasis, refractory to chemotherapy (antimonium complex), were cured when treated with antimonium in combination with gamma interferon, in spite of different immunological profiles. Different interpretative hypotheses of the reversion of chemoresistance induced by gamma interferon are discussed.

T lymphocytes from patients with visceral leishmaniasis treated in vitro with leishmania antigens are unable to proliferate and to produce gamma interferon. These patients have negative specific skin tests. Opposite results are obtained in patients with another clinical form of the disease named mucocutaneous leishmaniasis, in which both tests are positive. Nevertheless, patients with visceral leishmaniasis or mucocutaneous leishmaniasis, refractory to chemotherapy (antimonium complex), were cured when antimonium in combination with gamma interferon, in spite of different immunological profiles. Different interpretative hypotheses of the reversion of chemoresistance induced by gamma interferon are discussed.

High tumor necrosis factor-alpha (TNF-alpha) levels were present in the serum of 24 of 28 active visceral leishmaniasis (VL) patients (142.9 +/- 113.9 pg/ml, mean +/- SD), whereas levels were not elevated in 26 of 30 patients with cryptic leishmanial infection (16 asymptomatic, 4 with self-healing subclinical infection, and 10 posttreatment VL cases). Serum TNF-alpha levels were also not elevated in 15 normal volunteers (11.3 +/- 15.6 pg/ml) and in 10 patients with tegumentary leishmaniasis (19.1 +/- 10.8 pg/ml). Leishmanial infection of human monocyte-derived macrophages enhanced the basal TNF-alpha production by these cells, and this effect was further potentiated by treatment with recombinant interferon-gamma. After effective treatment of VL patients, serum TNF-alpha levels dropped rapidly (129 +/- 112 vs. 9 +/- 13 pg/ml in 10 days), even before clinical parameters such as spleen size or parasitism, white blood cell count, or levels of hemoglobin returned to normal values. On the other hand, patients unresponsive to treatment remained with elevated levels (276 +/- 69 vs. 155 +/- 71 pg/ml in 10 days). Thus, serum TNF-alpha levels in VL patients are a good parameter to monitor in determining host response to therapy.

We investigated the correlations between the biological effects of interferon-alpha (IFN-α) and clinical responsiveness in low-grade non-Hodgkin's lymphomas (NHL). In this disease, 40–50% of cases respond to IFN-α therapy. Patients with nodular NHL were selected for a phase II trial in which they were treated daily with 9 × 106 U of IFN-α2a. Binding experiments with [125I]IFN-α2a showed the presence of IFN-α receptors on tumor B-cells isolated from lymph nodes before therapy in 9 out of 10 patients. Receptor levels were not related to the subsequent clinical responses. However, no specific binding was detected in one patient who turned out to be unresponsive to IFN-α treatment. Single injections of IFN-α2a before beginning the therapeutic protocol resulted in down-regulation of IFN-α receptors without change in their affinity in peripheral blood leukocytes from only patients who subsequently resonded to therapy (4/10). In 4/5 non-responders and one patient displaying a minor response, receptor numbers did not decrease but Kd values rose markedly in all six cases. These results indicate that lack of in vivo IFN-α receptor down-regulation and reduced receptor affinity, as detected before therapy, may be correlated with failure of IFN-α therapy in nodular NHL.

Acute visceral leishmaniasis is associated with an antigen-specific immunosuppression of mononuclear cells as evidenced by defective in vitro production of interferon gamma. We evaluated treatment with recombinant human interferon gamma in combination with conventional pentavalent antimony therapy in patients with visceral leishmaniasis. Six of eight patients with visceral leishmaniasis (mean duration, 17 months) that had been unresponsive to multiple courses of pentavalent antimony responded to treatment with recombinant human interferon gamma (100 to 400 micrograms per square meter of body-surface area per day) in addition to pentavalent antimony (20 mg per kilogram of body weight per day) for 10 to 40 days. The other two patients improved initially but then relapsed and required treatment with amphotericin B. Eight of nine additional patients with previously untreated severe visceral leishmaniasis were also successfully treated with the combination of interferon gamma and pentavalent antimony. The 14 patients who responded to this regimen had marked improvement in symptoms and in measures of anemia and leukopenia, as well as weight gain, a decrease in spleen size, and an absence or reduction of leishmanias in splenic aspirates. These patients had no recurrence of illness after a mean (+/- SE) follow-up of 8 +/- 1 months. Fever was the only major side effect of interferon gamma. We conclude that the combination of interferon gamma and pentavalent antimony is effective in treating seriously ill patients with refractory or previously untreated visceral leishmaniasis.

Hairy cells are classified as B cell tumors at a preplasma cell stage of differentiation and are believed to represent cells undergoing a switch process. These cells are stimulated in vitro to DNA synthesis and multiplication in the presence of the lymphokine LMW-BCGF. We have tested the level of expression on these cells of the newly described B8.7 activation marker which has been reported to be associated with the capacity of various B cells to respond to LMW-BCGF. The presence of this marker has been readily detected on the hairy cells of 10 of the 12 patients tested in this study; interestingly, for one of the negative cases, the tumor cells were unable to proliferate in response to LMW-BCGF. As on normal B cells, a marked inhibition of the LMW-BCGF dependent response could be achieved in the presence of a monoclonal anti-B8.7 antibody, sustaining the proposal that the B8.7 molecule is involved in the signaling pathway of this growth factor. IFN-alpha is highly efficient in the therapy of hairy cell leukemia (HCL), and we confirm in the present study that IFN-alpha also inhibits the LMW-BCGF dependent proliferation of hairy cells in vitro. In addition, we show that this inhibition is independent of a significant modulation of the B8.7 antigen, a molecule putatively associated with the LMW-BCGF receptor.

Hairy cells are stimulated to DNA synthesis by low molecular weight B cell growth factor (LMW-BCGF) and this proliferative response is suppressed by interferon (IFN)-alpha, both in vitro and in vivo. The suggestion that the CD23 molecule (Fc epsilon II receptor) might be involved in the signalling pathway of LMW-BCGF prompted us to study the expression of this molecule on hairy cells and its modulation by IFN- alpha. By flow cytometry and direct binding experiments with anti CD23 monoclonal antibodies, the presence of the CD23 antigen was detected in 7 of 12 cases tested, on variable percentages of cells, ranging from low to medium expression. In vitro incubation of hairy cells with IFN- alpha, which elicits a suppression of the proliferative response of these cells to LMW-BCGF, induced a parallel significant reduction of CD23 expression in only three cases. Similarly, a transient in vivo decrease of CD23 expression, concommitant with an inhibition of the LMW- BCGF response, could be detected in only one of three patients injected with IFN-alpha. Soluble sCD23/IgE-binding factor (BF) was quantitated in the serum from six other patients with hyperleukocytic hairy cell leukemia (HCL) undergoing a clinical trial of IFN-alpha therapy. Before treatment, these patients presented higher concentrations of the cleaved soluble form of the CD23 molecule than normal controls. Within a few weeks of IFN-alpha administration, these levels markedly decreased, paralleling a diminution of blood leukemic cells. Of interest, no such diminution was noticed for another patient resistant to IFN-alpha therapy. These results show that the proliferative response of hairy cells to LMW-BCGF is not linked to the expression of the CD23 marker. Besides, when the latter molecule was present, its decrease following IFN-alpha treatment, which could be detected in some cases, was not necessarily required for the suppression of the LMW-BCGF response and is thus not mandatory for the therapeutic efficacy of IFN- alpha. Our results point out that quantitation of serum sCD23/IgE-BF, whether related to a process of autocrine proliferation or not, is a parameter of potential importance for therapy monitoring.

We have carried out a longitudinal study of interferon (IFN) and tumor necrosis factor (TNF) using a whole-blood mitogen stimulation assay in 20 multiple sclerosis (MS) patients and in a healthy control group. We set up individual profiles and the results were quite constant for each individual, both in healthy donors and in the patients in remission. Before exacerbations, however, we found an increase of IFN-gamma and TNF production preceding clinical symptoms by a maximum of 2 weeks. In benign cases, the increase disappeared rapidly, even before the appearance of symptoms, whereas we found sequelae whenever the increase persisted during weeks. In chronic progressive patients, we frequently found intervening increases. It may be that IFN-gamma and TNF trigger off exacerbations at a very early stage and that these cytokines may also play a role in maintaining disease in chronic progressive and invalidating forms.

IFN-alpha induces tumor regression with a high percentage of complete remissions in hairy cell leukemia. We have recently reported that hairy cells express specific IFN-alpha receptors which are down-regulated upon therapy. We show here that the activity of 2-5 A synthetase, an IFN-induced enzyme, is 2 to 7-fold stimulated in hairy cells from responsive patients within 12-24 h after the first IFN dose. This in-vivo enzyme induction paralleled the kinetics of receptor down-regulation. In one patient who was unresponsive to IFN-alpha treatment neither expression of IFN-alpha receptor nor change in 2-5 A synthetase were expressed and modulated as in sensitive patients. In-vitro treatment of hairy cells with recombinant interferons showed that IFN-beta 1 was able to induce this enzyme to the same extent than IFN-alpha 2, whereas IFN-gamma was inactive despite the presence of specific IFN-gamma receptors. Our results indicate that IFN-alpha can exert its therapeutic effects by acting directly on the hairy cells through interaction with surface membrane receptors. Induction of 2-5 A synthetase can be one of the steps involved in this action. However, both mechanisms, as well as receptor down-regulation are not sufficient to explain the responsiveness of hairy cell leukemia to IFN-alpha.

This report presents the results of a clinical trial on 53 patients with hairy cell leukaemia using low-dose alpha-interferon as therapy. Improvement of cytopenia and/or bone marrow hairy cell infiltration occurred in all but one patient. Often, blood and bone marrow improvements were dissociated and, after 7 or 13 months of therapy, complete remission was only observed in about 40% of patients. Recurrence of the disease was observed in some cases after cessation of therapy. A summary of the following results is presented: alpha-interferon receptor analysis, oncogene expression, study of the sensitivity of hairy cells to natural killer cells, and the effects of interferon on T-cell receptor gene rearrangement and on the function of T-cell clones. Results are also presented which show that myelofibrosis may be due to a release of platelet derived growth factor. The immunological findings and oncogene expression in 2 patients with a variant form of hairy cell leukaemia for which resistance to therapy was observed are also described. All the results show that interferon acts on hairy cells and are consistent with a direct effect by interferon in the treatment of hairy cell leukaemia.