Mireille Hontebeyrie

DNA-Based Immunization with Trypanosoma cruzi Complement Regulatory Protein Elicits Complement Lytic Antibodies and Confers Protection against Trypanosoma cruzi Infection

ABSTRACT A complement regulatory protein (CRP) of Trypanosoma cruzi was evaluated as a vaccine candidate in a murine model of experimental T. cruzi infection. Recombinant CRP derived from an Escherichia coli expression system and a plasmid encoding the full-length crp structural gene under the control of a eukaryotic promoter were used to immunize BALB/c mice. Immunization with both protein and DNA vaccines resulted in a Th1-type T-cell response, comparable antibody titers, and similar immunoglobulin G isotype profiles. Only mice immunized with the crp DNA plasmid produced antibodies capable of lysing the parasites in the presence of complement and were protected against a lethal challenge with T. cruzi trypomastigotes. These results demonstrate the superiority of DNA immunization over protein immunization with the recombinant CRP. The work also supports the further investigation of CRP as a component of a multigene, anti-T. cruzi DNA vaccine.

Deoxyribonucleic Acid Homologies in the Genus Leuconostoc

Six deoxyribonucleic acid (DNA)-DNA homology groups within 45 strains of the genus Leuconostoc were distinguishable through DNA-DNA hybridizations with four 3H-labeled reference DNA preparations from type or reference strains of the various known named species. There is good correspondence between two of these DNA-DNA hybridization groups and the species L. lactis and L. paramesenteroides. Strains named L. mesenteroides are heterogeneous, comprising three different hybridization groups. One of these groups includes all the strains named L. dextranicum and L. cremoris. These results agree precisely with previous results from an immunological study of the two isofunctional enzymes, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and d-lactate dehydrogenase (EC 1.1.1.28), prepared from L. lactis NCDO 546 and L. mesenteroides NCDO 768 (ATCC 12291).

Seroprevalence of Trypanosoma cruzi infection in French Guiana

A survey was carried out on 1487 individuals to assess the seroprevalence of Trypanosoma cruzi infection in French Guiana. The overall prevalence of T. cruzi specific IgG was 0.5%. In multivariate analysis, residence in areas where housing is favorable for the presence of triatomine bugs was the only factor associated with the presence of T. cruzi antibodies. These results have implications for public health since blood donors are not routinely screened for T. cruzi infection in French Guiana.

Comparative Immunological Relationships of Two Distinct Sets of Isofunctional Dehydrogenases in the Genus Leuconostoc

D-Lactate dehydrogenase (D-LDH) and glucose-6-phosphate dehydrogenase (G-6-P-DH), both purified from Leuconostoc lactis strain NCDO 546, were used to prepare specific antisera. Cross-reactions of varying intensity with the anti-D-LDH were obtained with all of the Leuconostoc strains and with certain strains of the heterofermentative lactobacilli studied. Cross-reactions with the anti-G-6-P-DH were obtained with all of the Leuconostoc strains except those of L. oenos; none of the heterofermentative lactobacilli cross-reacted. Pairwise comparisons between cross-reacting extracts with respect to each antiserum permitted the assignment of strains to groups of identical immunological specificity: with the exception of a single strain, the groups of strains revealed by the use of each antiserum coincided.

Immunological Relationships of Glucose-6-Phosphate Dehydrogenase of Leuconostoc mesenteroides NCDO 768 (= ATCC 12291)

An antiserum against the purified glucose-6-phosphate dehydrogenase (EC 1.1.1.49) (G-6-P-DH) of Leuconostoc mesenteroides NCDO 768 has been prepared. Cross-reactions were observed with extracts of other strains of Leuconostoc, comprising named strains of L. lactis, L. mesenteroides, L. dextranicum, L. cremoris, and L. paramesenteroides. Cross-reactions were not obtained with L. oenos. The groups of identical specificity and their order of decreasing similarity toward the homologous enzyme were determined, and the results are consistent with those obtained previously with another G-6-P-DH antiserum from L. lactis NCDO 546. Thus, except for L. oenos, many strains of Leuconostoc comprising multiple (three or more) species might be considered as phenotypically diverse but genetically rather uniform in their line of descent from a common ancestor.

Séparation et purification de la D-lactico-déshydrogénase et de la glucose-6-phosphate déshydrogénase de Leuconostoc lactis Etude de quelques propriétés

Summary The NAD dependent D-lactic acid dehydrogenase and the NAD(P) dependent glucose-6-phosphate dehydrogenase from Leuconostoc lactis have been purified from the same crude extact by chromatography on hydroxyapatite. The two enzymes were then separately purified until obtention of fractions producing a single band of protein in polyacrylamide gel electrophoresis and a single line of precipitation by immunoelectrophoresis. The main properties of the two enzymes were studied and compared to the properties of isofunctionnal enzymes of other lactic acid bacteria. The D-lactic acid dehydrogenase of Leuconostoc lactis shows the same physical and kinetic properties than the Lactobacillus enzymes. These properties are quite different from those of other known bacterial D-lactic acid dehydrogenases.

Pathological Consequences of Host Response to Parasites

The pathophysiology of Chagas heart disease is still not well understood and two main mechanisms have been proposed: (i) parasite-dependent myocardial damage and (ii) immunological responses associated with molecular mimicry. Some data support that the pathology relies on boosted inflammation and specific CD8 + T cell responses triggered by the parasites present in heart. This is associated with particular profile of cytokines/chemokines secretion and modifications of regulatory T cells, NK and NKT cells. The role of the parasite is directly supported by the reduction of heart disease after parasiticidal treatments and indirectly by the relationship between high parasitemia in acute phase and evolution toward chronic Chagas heart disease. The large lymphocyte polyclonal activation induced during the acute phase, likely worsens the situation and favors the induction of autoreactive antibodies and T cells (by molecular mimicry) that participate in chronic heart lesions. Recently, parasite molecules able to polyclonally activate the B cell compartment have been cloned: one is a proline racemase and the other one is a trans -sialidase. The entry of the parasite also triggers an important remodeling of the lymphoid organs, splenomegaly, swelling of lymph nodes, and atrophy of the thymus. This atrophy of the thymus could be associated to alteration of the T cell repertoire. Murine model has also disclosed a crucial role for CD4 + T cells in the chronic pathology. The complexity of interactions between the mammalian host and Trypanosoma cruzi needs further studies to elucidate the multifactorial process leading to chronic Chagas disease depending (i) on the parasite and its genomic heterogeneity and (ii) on host genetic factors as well as environmental factors.

Other Forms of Transmission

Publisher Summary This chapter discusses the four modes of T. cruzi contamination. In addition to the natural transmission of Trypanosoma cruzi by vectors or from a mother to a newborn, the parasite may be transmitted by transfusion of infected blood, at the time of an organ transplant from an infected donor or to an infected recipient, by a laboratory accident with contaminated samples, or by an oral route. Presently, safe policies have been implemented to control the blood supply in blood banks in endemic countries and in most of the nonendemic countries, where there are many Latin American migrants, and to control the status of a donor or receiver of an organ transplant. To prevent laboratory accidents, severe measures exist to avoid the risks of contamination, and working conditions are highly managed. Oral transmission seems to be developing particularly in the Amazonian area because of the custom to drink juice from fruits of palm trees in which generalist triatomines are living. Education of the population is absolutely essential to control this kind of transmission.

21 – Vector Transmission

Publisher Summary Generally, transmission occurs during the night when the insects are the most active, at which time they take their blood meal on sleeping humans. The parasite is transmitted during this contact, but the free-infection form (flagellated) is in the feces of the insect rather than the salivary glands as in most other arthropod vectors. Chagas disease is commonly transmitted by blood-sucking triatomine vectors living in residential dwellings (domestic vectors) in close contact with humans. Indeed, the main interventions to decrease transmission focus on eliminating vectors that live in dwellings. The parasites are concentrated in the rectal bulb in the terminal part of the digestive tube of the insect, and during the blood meal or soon after, the bugs defecate and deposit the infected feces on the skin or near mucosa. The bite causes a skin abrasion that allows the parasite to enter underneath the skin. This transmission is complex, and all the steps are not well understood. Its load depends on many factors including those that promote the human vector contact, and those that allow the parasite to enter its host.