Adjuvant requirements for protective immunization of mice using a Trypanosoma cruzi 90K cell surface glycoprotein

A wide range of adjuvants including alhydrogel, saponin, Corynebacterium parvum, DDAB, Pfizer CP-20,961, oil adjuvants and several MDP analogues have been compared for their adjuvant activity in protecting mice against lethal Trypanosoma cruzi infection following immunization with a T. cruzi 90K cell surface glycoprotein. Only saponin was found to be effective. Promotion did not correlate with the ability to promote a particular Ig isotype; however, saponin was unique in its ability to promote cell-mediate immunity against the 90K glycoprotein.

Effect of isometamidium on infections by Trypanosoma vivax and T. evansi in experimentally-infected animals

Assays dealing with the therapeutic and prophylactic activity of isometamidium on experimental infections by Trypanosoma vivax and T. evansi were carried out. The drug was found to be highly effective against T. vivax infection in sheep and cattle in which periods of protection ranging from 118 to 195 days were achieved. No complete effects against infection by T. evansi were observed. The drug was well tolerated in sheep and cattle while side-effects were noted in treated mares. It was concluded that isometamidium could be used to prevent damage and economical losses caused by T. vivax in Venezuela.

[Ecological aspects of South American trypanosomiasis. XVII - Development of Triatominae regional domiciliation in an endemic center of Triatoma sordida]

São apresentados os resultados obtidos mediante as observações sobre o processo de domiciliação triatomínea, após a desinsetização domiciliar, e levadas a efeito no período de janeiro de 1975 a janeiro de 1979. A região estudada inclui-se no domínio paisagístico dos cerrados do Brasil Central, considerado como centro de dispersão de Triatoma sordida. A domiciliação local, inicialmente encontrada, implicou a participação dessa espécie e de Triatoma infestans. Após a realização do expurgo, as pesquisas de vigilância trimestrais e os levantamentos finais evidenciaram a ocorrência de novo processo de domiciliação de triatomíneos, de decurso lento, e resultando em coeficientes de positividade de edifícios acentuadamente inferiores aos registrados por ocasião do levantamento inicial, durante todo o período de observação. Após o expurgo, o valor geral do coeficiente de edifícios (casas e anexos) positivos variou do valor mínimo de 1,9 ao máximo de 5,7%, enquanto foi de 40,4% o observado quando do levantamento inicial. Essa situação perdurou pelo tempo mínimo de três anos e meio, o que permite recomendar que a vigilância e a possível aplicação do expurgo seletivo, subseqüentes à desinsetização geral, sejam iniciadas a partir de decorrido tal prazo. Nesse ínterim, recomenda-se a motivação dos habitantes locais, no sentido de obter-lhes a colaboração para a denúncia de novos focos intradomiciliares. Na transferência da infecção tripanossômica para o ambiente domiciliar evidenciou-se papel importante desempenhado por vertebrados domiciliados ou em domiciliação, em especial modo ratos (Rattus) e gambás (Didelphis), de hábitos ubiquistas. No processo de evolução da nova domiciliação triatomínea, coube papel preponderante a T. sordida mediante a ocupação inicial do peridomicílio. O reaparecimento de T. infestans deveu-se principalmente à influência da atividade humana, em especial modo, a mobilidade dos habitantes locais. O papel desempenhado pelo R. neglectus foi pouco expressivo embora, à semelhança de T. sordida, tenha facilmente desenvolvido colônias em galinheiros experimentais. A participação proporcional dos dois principais triatomíneos na composição específica das populações domiciliadas, observada antes e após o expurgo em cinco diferentes ocasiões, foi avaliada pelos respectivos percentuais dentro do número total e edificações (casas e anexos) encontradas positivas. Os resultados mostraram aumento constante da proporção correspondente a T. sordida e diminuição da referente a T. infestans. Atribuiu-se a fatores educacionais e habitacionais maior influência sobre a domiciliação desta espécie do que na daquela. Observou-se também indícios sobre a possibilidade de dispersão ativa de T. infestans. Nas áreas rurais, os anexos peridomiciliares revelaram-se como ecótopos de concentração para o início da domiciliação de triatomíneos silvestres, em especial modo, de T. sordida. As áreas com pequeno número de anexos, aparentemente permanecem negativas por tempo mais prolongado, levando a supor que a domiciliação encontre ali maiores dificuldades de se desenvolver.

Immunization against a challenge with insect vector, metacyclic forms of Trypanosoma cruzi simulating a natural infection

The protective effects of immunization with an antigen derived from epimastigote forms of Trypanosoma cruzi against challenges with vector metacyclic or bloodstream forms of the parasite were investigated. A marked degree of protection was observed in the immunized mice after challenged with bloodstream or insect-transmissible metacyclic forms. High rates of survival in the immunized groups were accompanied by relatively low, shortlasting parasitemias in some of the animals and significant percentages of immunized mice never developed a measurable parasitemia during the course of the experiments. In contrast, all of the non-immunized animals showed high levels of parasitemias. Similar results were obtained whether the metacyclic challenge was by the intraperitoneal or by the ocular route for which conditions mimicking a natural infection were selected. These results emphasize the protection that immunization confers against challenge with insect-transmissible forms of T. cruzi, and the feasibility of protecting a highly susceptible host against an otherwise lethal acute infection similar to one occurring naturally.

Trypanosoma cruzi: attenuation of virulence by culture in tissues

Trypomastigotes of the 'Brazil' strain of Trypanosoma cruzi were cultured in Vero and fish (Pimephales promelas) cells at 30 and 37 C. Those harvested from 37 C Vero cell cultures killed all inoculated C3H mice no matter how long the cultures had been maintained. Those harvested from 120-day 30 C Vero and fish cultures killed only 1 out of 10 mice each, indicating attenuation of virulence. When the surviving mice were later challenged with Vero-cultured trypomastigotes known to be lethal to controls, only 2 of the 18 animals developed even light parasitaemias, indicating previous immunization by the attenuated parasites. Varying the number of attenuated trypomastigotes cultured at 30 C for 30 days at most delayed the rise of parasitaemia. Possible mechanisms of these phenomenon are discussed.

Cell surface glycoproteins of Trypanosoma cruzi: protective immunity in mice and antibody levels in human chagasic sera

Two cell surface glycoproteins from Trypanosoma cruzi have been compared for their ability to protect mice against an acute lethal infection. One of these, a 90,000 glycoprotein found on all stages of the parasite, protected against both bloodstream and metacyclic trypomastigote challenge. A 72,000 glycoprotein found only on insect-derived stages of T. cruzi protected only against a metacyclic trypomastigote challenge. Antibody against both of these glycoproteins was present in human chagasic sera.

The treatment and control of parasitic diseases

In many parts of world, transmission of malaria due to Plasmodium falciparum can no longer be controlled by insecticides. Furthermore, this species has developed an amazing capacity for resistance to polyvalent drugs. The advent of new drugs and the possibility of developing a vaccine offer some hope for control of falciparum malaria. The fact that the spread of many parasitic diseases is promoted by contaminated water supplies resulting from inadequate waste disposal raises important questions about the relevance of current research. The control of some endemic infections, like Chagas' disease, would be better served by delivery of available technology than by improved science education. Discovery of means to promote self-help programs in rural communities will be an important aspect of research in disease control in the future.

Trypanosoma cruzi culture used as vaccine to prevent chronic Chagas' disease in mice

The development of chronic pathology in mice at 2 to 10 months after inoculation of 10(2) T. cruzi trypomastigotes can be prevented by preimmunization with live, attenuated culture parasites (strain TCC). Swiss mice received one or three immunizing inoculations of 10(6) TCC organisms and were challenged with 10(2) Tulahuén blood trypomastigotes. Control groups received only the immunizing or the challenge inoculations. Immunized groups as compared with nonimmunized controls had lower mortality rates at 2 months postchallenge (9% versus 23%; P = 0.059), lower early peaks of parasitemia, lower percentages of positive xenodiagnoses at 5.5 months (40 versus 80%; P = 0.061), and lower incidences of tissue lesions in the skeletal muscle (P less than 0.005) at 2,6, and 10 months postchallenge. Tissue lesions in the heart and smooth muscle were also reduced, reaching statistical significance after 10 months (P less than 0.02). Chronic pathology parameters were never enhanced in preimmunized groups. In spite of the putative role that autoimmunity may play in the development of chronic chagasic lesions, the preventive effect of vaccination is readily exerted upon the chronic murine model of Chagas' disease.

A primary screen for drugs to prevent transmission of Chagas's disease during blood transfusion

This paper describes how Microslide tubes can be used as the basis for a quick, simple, inexpensive screen to test for compounds which might prevent the transmission of Chagas's disease as a result of blood transfusion. The test uses Trypanosoma cruzi-infected mouse blood and requires only very small amounts of compound. The screen identifies compounds known to be active against blood trypomastigotes in vitro at 4 degrees C, and is apparently free of false negative and positive results.

The control of Chagas' disease in Mambaí, Brazil: the initial phases

The control of Chagas' disease depends on breaking contact between Man and vector organisms living in the house fabric; the primary method utilized is residual insecticide spraying of houses. Ministries of health in afflicted countries have elaborated standard procedures for such combat programs. The first two phases of such a program in Mambaí, Goiaś, Brazil are described. In the third phase of vigilance, community participation is necessary to detect residual organism populations in houses. A house improvement scheme applied to houses with persistent infection, is recommended as being most practical at this time.

[Proposal for a predator for the destruction of Triatoma infestans: Tarentola mauritanica]

The task of Chagas disease control is overwhelming. One of the measures is the destruction of the bugs which act as vectors. In this paper the authors suggest trying this with a predator, a voracious insectivorous lizard, a kind of gecko: the Tarentola mauritanica or Moorish Gecko. These geckos were transported fortuitously to Argentina in cargoes of cork from their natural habitat, the Mediterranean basin. They have adapted easily to their new environment. Their ability to eat the kissing bug (Triatoma infestans) was tested in the observations reported herein. Four adult geckos were caught in an area of the city of Buenos Aires, in the neighbourhood of a corkstop factory. These geckos were placed in a modified glass acuarium tank with fourteen ninphs and adult kissing bugs. The bugs were rapidly eaten by the geckos (Fig. 3). The advantages of this type of biological control are stressed. The lizard and the bugs share the same habitat and both are nocturnal. Both make themselves quite at home in human habitations. The lizards -as the birds- are refractory to Tripanosomiasis and so they cannot become reservoirs. This kind of gecko seems also to be resistant to the toxic action of Gammexane. Therefore the authors think it is worthwhile to try this possibility of bug control in the field. It will be necessary to favour the reproduction of gecko and promote an educational campaign to prevent their destruction by man emphasizing their usefulness and their domesticity. Though costs were not estimated, the authors believe that it would be cheaper to provide lizards to dwellers in the poor homes of the rural areas ("ranchos") than expensive campaigns with potentially dangerous insecticides.

Prevention of transfusion-induced Chagas' disease by amphotericin B

Amphotericin B, a polyene antibiotic effective against eukaryotic cells, can eliminate the trypomastigote form of Trypanosoma cruzi from blood stored at 4 degrees C. This antitrypanosomal effect can be achieved with a concentration of 3 micrograms/ml within 48 hours. This concentration of amphotericin B does not produce hemolysis over a period of 3 weeks. Amphotericin B methyl ester and nystatin are not effective. Amphotericin B may be considered as a replacement for crystal violet in blood bank blood to prevent transfusion-induced Chagas' disease.

[Ecological aspects of South American trypanosomiasis. XV. Development, variation and permanence of Triatoma sordida, Panstrongylus megistus and Rhodnius neglectus in artificial ecotopes]

Em colônias de Triatoma sordida, Panstrongylus megistus e Rhodnius neglectus, espontaneamente desenvolvidas em galinheiros experimentais, observou-se as condições de desenvolvimento, bem como a variação e a permanência de seus componentes. A colonização e dispersão de T. sordida é favorecida em ambiente aberto resultante da instalação de pastagens com conseqüente proliferação de árvores isoladas e secas. O desenvolvimento de colônias de P. megistus ocorre em ambiente coberto na íntima proximidade de matas residuais, admitindo-se que os anexos domiciliares lhes sirvam de pontos de atração. O R. neglectus revelou certo grau de domiciliação aliado à capacidade de dispersão que lhe permite atravessar distâncias apreciáveis. O primeiro semestre do ano parece incluir a época infestante das colônias de T. sordida revelada pela maior produção de adultos e ninfas de primeiro estádio. O papel de visitantes observado para algumas ninfas dessa espécie, permite supor do poder de dispersão dessas formas.

Corynebacterium parvum as an adjuvant for Trypanosoma cruzi epimastigote vaccines: a comparison with saponin and Bordetella pertussis

The effect was compared in CBA mice of adding Corynebacterium parvum, saponin, and Bordetella pertussis to living or killed Trypanosoma cruzi (Y strain) epimastigote vaccines on the induction of protective immunity against subcutaneous (s.c.) challenge with blood trypomastigotes. The addition of C. parvum to a low dose of T. cruzi vaccine, which alone was non-protective, generated a greater degree of protection than did saponin or B. pertussis. C. parvum alone increased resistance to infection to a variable and usually weak extent. The addition of C. parvum to larger doses of T. cruzi vaccine, which were themselves sufficient to elicit some degree of protection, improved resistance when the challenge was given 1 or 12 weeks after immunization, but lowered it at 3 weeks. It is concluded that the comparative efficacy of adjuvants for T. cruzi vaccines needs to be assessed on 3 parameters: (1) the dose of antigen, (2) the dose of adjuvant and (3) the time interval between immunization and challenge.

A comparison of challenge with Trypanosoma cruzi blood-stream trypomastigotes and metacyclic trypomastigotes from Rhodnius prolixus in mice immunized with killed antigens

Groups of CD-1 mice were immunized with vaccines prepared from freeze-thawed or ultra-sonicated epimastigotes, blood trypomastigotes, or "plasma antigen", of Trypanosoma cruzi strains Y, M1 and Tulahuen. The mice were challenged by the injection of blood stream trypomastigotes obtained from mice, or of metacyclic trypomastigotes harvested from the rectum of Rhodnius prolixus. Both challenges induced virulent infections in control mice. Blood-stream trypomastigotes killed mice more rapidly than the same number of bug-derived trypomastigotes. Vaccinated mice resisted infection with bug-derived trypomastigotes as well as with blood trypomastigotes, and in some instances better. It is concluded that results obtained with the more convenient, but artificial blood trypomastigote challenge are comparable with the more natural, bug-derived, challenge.

Chagas' disease: trends in immunological research and prospects for immunoprophylaxis

Acute infection with Trypanosoma cruzi usually subsides spontaneously but the mortality rate encountered in individuals with the chronic infection is high. Much evidence has accumulated in the last five years that autoimmunity plays an important role in the pathogenesis of the myocarditis that is common in the chronic phase. A negative relationship has been observed between the demonstrable parasitaemia and the presence of severe cardiac lesions. This myocarditis is characterized by lymphocytic infiltrates and destruction of normal heart cells, in the absence of the parasite in situ. Furthermore, the demonstration in vitro of heart cell lysis by T. cruzi-sensitized T lymphocytes is strong evidence of autoimmunity in Chagas' disease.Acquired immunity plays a major role in the course that T. cruzi infections may run in the mammalian host. As a result of the immune mechanisms induced by the parasite, the infection is controlled at subpatent levels, and the immune host does not develop acute T. cruzi infection again. At present there are several means of achieving immunoprotection against experimental T. cruzi infections, but it is not known whether vaccinated animals might develop chronic Chagas' disease and die many months or years later. Studies on immunoprotection against Chagas' disease should therefore not be limited only to the acute phase of the infection. Furthermore, the involvement of autoimmunity in the production of the lesions of Chagas' disease indicates that research in this area should be conducted with caution. The definition of an animal model for chronic Chagas' disease is essential to further development of immunological research devoted to immunoprophylaxis.

Immunization of mice against Trypanosoma cruzi: the effect of chemical treatment or immune serum on an epimastigote vaccine

Groups of long Evans and CD-1 mice were immunized with vaccines prepared from epimastigotes of Trypanosoma cruzi, strains Y and Tulahuen, modified by various chemical means, or by the addition of immune sera. Freeze-thawed epimastigotes were used as a control antigen. Freeze-thawed epimastigotes, with and without saponin as adjuvant, gave significant protection against challenge with homologous trypomastigotes. Similar levels or protection were obtained in mice vaccinated with living epimastigotes. Treatment of epimastigotes by various chemical means, including sodium perchlorate failed to increase their immunogenicity, but did not reduce it. The addition of immune serum to the antigen may have slightly increased its immunogenicity.

The effect of an immune RNA (RNAi) against Trypanosoma cruzi infection in mice

Immune ribonucleic acid (RNAi) was extracted with phenol from the spleen of mice immunized with the avirulent PF strain of Trypanosoma cruzi. These preparations were able to induce immunocompetent cells to answer as a secondary response to later challenges with the virulent Y strain of the same parasite. The preparations of RNAi were"immunogenic" and free of proteins. The RNAi preparations were sensitive to pancreatic RNAase and lost their immune effect when pretreated with this enzyme. The injections of normal RNA (RNAn) obtained by the same method showed that this polymer acts as an immuno supressor or competitive agent. The electrophoretic profiles of the RNAi preparations in polyacrylamide gels showed normal and characteristic migration patterns (28S, 18S and 4.5S). These results demonstrate the development of an immune state against T. cruzi infection in mice injected with RNAi, in the absence of living parasites.

Passive immunization of mice against Trypanosoma cruzi using convalescent mouse serum

Groups of 10 mice were infected by the s.c. injection of blood trypomastigotes of Trypanosoma cruzi, strains "Y" and "Tulahuen". They were injected i.p. with convalescent mouse-anti-T. cruzi serum (CMATS) at various times. A single dose of CMATS (Y) was most effective when injected one day after homologous infection -31 of 40 mice survived the infection, whereas all controls, both untreated and injected with normal serum, died. CMATS was significantly less effective in treating mice infected with the Tulahuen strain. Sera from animals immunized with killed epimastigotes or trypomastigotes showed only very slight passive immunizing properties.

Effect of the injection of ribosomes and RNA from Crithidia fasciculata on the experimental infection of mice by Trypanosoma cruzi

Immunization of mice with Crithidia fasciculata (live suspension, ribosomal fraction and purified RNA) induced a certain degree of protection (decrease of parasitaemia) against infection with Trypanosoma cruzi.

Role of activated macrophages in resistance of mice to infection with Trypanosoma cruzi

The role of the activated macrophage in resistance of mice to infection with Trypanosoma cruzi was investigated with use of mice that had not been infected with T. cruzi but whose macrophages were activated by Toxoplasma gondii or Besnoitia jellisoni. Mice with activated macrophages were significantly more resistant to intra-peritoneal challenge with the Tulahuen strain of T. cruzi than were controls. The role of serum factors in resistance to T. cruzi was excluded by the demonstration of no difference between survival of T. cruzi in serum from mice with activated macrophages and in that from controls. As the only modality of resistance to T. cruzi in this in vivo model appeared to be the activated macrophage, this cell was investigated in vitro. Activated macrophages were shown to be able to inhibit completely multiplication of T. cruzi, whereas significant multiplication of the parasite occurred in control macrophages. Both in vivo and in vitro data suggest that the activated macrophage may play a major role in resistance to infection with T. cruzi.

Enhancement of resistance and suppression of immunization against experimental Trypanosoma cruzi infection by Corynebacterium parvum

Intravenous but not intraperitoneal injection of killed Corynebacterium parvum either before or after intraperitoneal infection with the highly reticulotropic Tulahuén strain of Trypanosoma cruzi produced enhanced resistance against the infection in mice. In contrast, C. parvum had no effect when the infection was caused with the predominately myotropic Y strain of T. cruzi. C. parvum given intravenously before immunization with killed culture forms of the Y strain parasite consistently diminished the protective effect against subsequent infection, which could be obtained with antigen alone.