The vertical dispersión of Anopheles (Kerteszia) cruzi in a forest in southern Brazil suggests that human cases of malaria of simian origin might be expected

By staining females of Anopheles cruzi with fluorescent coloured powders in a forest in the State of Santa Catarina, we showed that they move from canopy to ground and vice-versa to feed. This suggests that in areas where this mosquito is a vector of human and simian malarias sporadic infections of man with monkey plasmodia might be expected.

Study of some parameters affecting the in vitro cultivation of Plasmodium falciparum within saimiri sciureus red blood cells

The in vitro growth and multiplication of the erythrocytic stages of Plasmodium falciparum within Saimiri sciureus (squirrel monkey) red blood cells have been studied. Various parameters, such as the origin of the red blood cells and serum supplement, nature of the buffer, influence of the final pH of the medium, role of proteose peptone and glucose addition, were investigated. The selection of the best culture conditions led to the obtention of a reproducible in vitro growth of two parasite cycles in Saimiri erythrocytes, which is an useful achievement for in vitro studies. Our failure to establish a continuous culture line for longer than 19 days, could be explained by a dramatic increasing of osmotic fragility of the Saimiri red blood cells related to their small size.

A review of achievements of the national schistosomiasis control program in middle and upper Egypt areas

In Egypt the "national schistosomiasis control program" was formulated to control transmission by reduction of prevalence and intensity of current infections, and thereby achieve an acceptable level of schistosomiasis disease control. The program was implemented foremost in Middle Egypt (1977) and Upper Egypt (1980), collectively extending 800 km alongside of the River Nile and accommodate about 10.5 million people. Schistosoma haematobium has been essentially the prevailing species infection in both areas. The strategy of control entailed both area-wide mollusciciding with niclosamide, and selective population chemotherapy with metrifonate. Evaluation in 1986 showed that prevalence dropped from pre-control 29.4% in Middle Egypt and 26.3% in Upper Egypt to 6% and 7.8% respectively, together with a remarkable drop of infections among children. Also mean intensity attained low levels consistent of low grade infections. It is evident therefore that in these areas where an enhancement of schistosomiasis infections had been anticipated the employment of the twofold strategy effected a state of low-prevalence/low-intensity signifying a lowered reservoir of infection and a substantial interference with the potentials of transmission.

Trypanosoma cruzi: experimental Chagas' disease in Rhesus monkeys. II. Ultraestructural and cytochemical studies of peroxidase and acid phosphatase activities

Ultrastructural and cytochemical studies of peroxidase and acid phosphatase were performed in skin, lymph node and heart muscle tissue of thesus monkeys with experimental Chagas's disease. At the site of inoculation ther was a proliferative reaction with the presence of immature macrophages revealed by peroxidase technique. At the lymph node a difuse inflammatory exudate with mononuclear cells, fibroblasts and immature activated macrophages reproduces the human patrtern of acute Chagas' disease inflamatory lesions. The hearth muscle cells present different degrees of degenerative alterations and a striking increase in the number of lysosomal profiles that exhibit acid hydrolase reaction product. A strong inflammatory reaction was present due to lymphocytic infiltrate or due to eosinophil granulocytes associated to ruptured cells. The present study provides some experimental evidences that the monkey model could be used as a reliable model to characterize histopathological alterations of the human disease.

Some biological properties of the human amniotic membrane interferon

Human amniotic interferon was investigated to define the species specificity of its antiviral action and compare its anti-cellular and NK cell stimulating activities with those of other human interferons. The antiviral effect was titrated in bovine (RV-IAL) and monkey (VERO) cells. Amniotic interferon exhibited, in bovine cells, 5% of the activity seen in monkey cells, while alpha interferon displayed 200%. No effect was detected with either beta or gamma interferon in bovine cells. Daudi cells were exposed to different concentrations of various interferons and the cell numbers were determined. The anticellular effect of the amniotic interferon reached its peak on the third day of incubation. Results suggested a higher activity for alpha and gamma interferons and a lower activity for beta when compared to amniotic interferon. Using total mononuclear cells as effector cells and K 562 as target cell in a 51Cr release assay, it was demonstrated that low concentrations of amniotic interferon consistently stimulated NK cell activity in cells derived from several donors, the results indicating a higher level of activity with this interferon than with alpha and beta interferons.

The Pf332 gene codes for a megadalton protein of Plasmodium falciparum asexual blood stages

We characterized the Plasmodium falciparum antigen 332 (Ag332) which is specifically expressed during the asexual intraerythrocytic cycle of the parasite. The corresponding Pf332 gene has been located in the subtelomeric region of chromosome 11. Furthermore, it is present in all strais so far analyzed and shows marked restriction length fragment polymorphism. Partial sequence and restriction endonuclease digestion of cloned fragments revealed that the Pf332 gene is composed of highly degenerated repeats rich is glutamic acid. Mung been nuclease digestion and Northern blot analysis suggested that Pf332 gene codes for a protein of about 700 kDa. These data were further confirmed by Western blot and immunoprecipitation of parasites extracts with an antiserum raised against a recombinant clone expressing part of the Ag332. Confocal immunofluorescence showed that Ag332 is translocated from the parasite to the surface of infected red blood cells within vesicle-like structures. In addition, Ag332 was detected on the surface of monkey erythrocytes infected with Plasmodium falciparum.

A study on the pathogenesis of human cerebral malaria and cerebral babesiosis

Cerebral complications are important, but poorly understood pathological features of infections caused by some species of Plasmodium and Babesia. Patients dying from P. falciparum were classified as cerebral or non-cerebral cases according to the cerebral malaria coma scale. Light microscopy revealed that cerebral microvessels of cerebral malaria patients were field with a mixture of parazited and unparazited erythrocytes, with 94% of the vessels showing parasitized red blood cell (PRBC) sequestration. Some degree of PRBC sequestration was also found in non-cerebral malaria patients, but the percentage of microvessls with sequestered PRBC was only 13% Electron microscopy demonstrated knobs on the membrane of PRBC that formed focal junctions with the capillary endothelium. A number of host cell molecules such as CD36, thrombospondim (TSP) and intracellular adhesion molecule I (ICAM-1) may function as endothelial cell surfacereports for P. falciparum-infected erythrocytes. Affinity labeling of CD36 and TSP to the PRBC surface showed these molecules specifically bind to the knobs. Babesia bovis infected erythrocytes procedure projections of the erythrocyte membrane that are similar to knobs. When brain tissue from B. bovis-infected cattle was examined, cerebral capillaries were packed with PRBC. Infected erythrocytes formed focal attachments with cerebral endothelial cells at the site of these knob-like projections. These findings indicate that cerebral pathology caused by B. bovis is similar to human cerebral malaria. A search for cytoadherence proteins in the endothelial cells may lead to a better understanding of the pathogenisis of cerebral babesiosis.

South American monkeys in the development and testing of malarial vaccines - a review

South American Aoutus an d Saimiri monkeys, which are susceptible to infection with human malarias, have been used to develop models for the testing of huma malaria vaccines. Studies indicate that blood-stage and sporozoite vaccines can be tested in these monkeys using appropriate strains of parasites.

Mechanisms of protective immunity against asexual blood stages of Plasmodium falciparum in the experimental host Saimiri

In the Saimiri monkey, an experimental host for human malaria, acquired protection against Plasmodium falciparum blood stages depends on the IgG antibody populations developed. In vivo protective anti-falciparum activity of IgG antibodies is correlated with the in vivo opsonizing activity promoting phagocytosis of parasited red bloood cells. In contrast, non protective antibodies inhibit this mechanism by competing at the target level. A similar phenomenon can be and human infection. Anti-cytoadherent and anti-rosette antibodies developed by Saimiri and humans prevent the development of physiopathological events like cerebral malaria which can also occur in this experimental host. Furthermore, transfer to protective human anti-falciparum IgG antibodies into infected Saimiri monkeys exerts an anti parasite activity as efficient as that observed when it is transfered into acute falciparum malaria patients, making the Saimiri an even more attractive host. Studies on the role of immunocompetent cells in the protective immune reponse are still in their infancy, however the existance of a restricted polymorphism of MHC II class molecules in the Saimiri confers additional theoretical and practical importance to this model.

Protection of aouts monkeys after immunization with recombinant antigens of Plasmodium falciparum

The genus Aotus spp. (owl monkey) is one of the WHO recommended experimental models for Plasmodium falciparum blood stage infection, especially relevant for vaccination studies with asexual blood stage antigens of this parasite. For several immunization trials with purified recombinant merozoite/schizont antigens, the susceptible Aouts kenotypes II, III, IV and VI were immunized with Escherichia coli derived fusion proteins containg partial sequences of the proteins MSAI (merozoite surface antigen I), SERP (serine-strech protein) and HRPII (histidine alanine rich protein II) as well as with a group of recombinant antigens obtained by an antiserum raised against a protective 41 kD protein band. The subcutaneous application (3x) of the antigen preparations was carried out in intact animals followed by splenectomy prior to challange, in order to increase the susceptibility of the experimental hosts to the parasite. A partial sequence of HRPII, the combination of three different fusion proteins of the 41 kD group and mixture of two sequences of SERP in the presence of the modified Al(OH)3 adjuvant conferred significant protection against a challange infection with P. falciparum blood stages (2-5 x 10 (elevado a sexta potência) i. RBC). Monkey immunized with the MS2-fusion protein carrying the N-terminal part of the 195 kD precursor of the major merozoite surface antigens induced only marginal protection showing some correlation between antibody titer and degree of parasitaemia. Based on the protective capacity of these recombinant antigens we have expressed two hybrid proteins (MS2/SERP/HRPII and SERP/MSAI/HRPII) in E. coli containing selected partial sequences of SERP, HRPII and MSAI. Antibodies raised against both hybrid proteins in rabbits and Aotus monkeys recognize the corresponding schizont polypeptides. In two independent immunization trials using 13 animals (age 7 months to 3 years) we could show that immunization of Aotus monkeys with either of the two hybrid proteins administered in an oil-based well tolerated formulation protected the animals frm a severe experimental P. falciparum (strain Palo Alto) infection.

Study of humoral immune response in mammals immunized with Plasmodium falciparum antigenic preparations

Six Plasmodium falciparum protein fractions, isolated under reducing conditions, were used to immunize mice, rabbits and the squirrel monkey Saimiri sciureus. Five or seven subcutaneous injections of each antigenic preparation, in conjunction with Freund's complete or incomplete adjuvants, were administered. This led to the development of specific antibodies detected by IFAT, ELISA or immunobloting which inhibited merozoite reinvasion in in vitro P. falciparum cultures. This activity seems to be associated with rhoptry proteins contained in fractions Pf F2 and Pf F4.

Simian malaria at two sites in the Brazilian Amazon: I-The infection rates of Plasmodium brasilianum in non-human primates

The parasite that causes simian malaria in the Brazilian Amazon, Plasmodium brasilianum, is infective to man. In this region, where humans live within and in close proximity to the forest, it was suspected that this parasite could be the cause of a zoonosis. A study was performed in the areas surrounding two hydroelectric plants in the Amazon, Balbina and Samuel, aiming at determining the zoonotic potential of this parasite. P. brasilianum was detected in, respectively, 15.8% and 9.9% of 126 and 252 primates belonging to seven and eight species examined from Balbina and Samuel. The highest malaria infection rates were found among the red-howler monkey Alouatta seniculus straminea (32.3%), the bearded-saki Chiropotes satanas chiropotes (50%) and the spider-monkey Ateles paniscus paniscus (2[1+]) from Balbina and in the squirrel-monkey Saimiri ustus (21%) and the black-faced-spider-monkey Ateles paniscus chamek (28.6%) from Samuel.

Chronic experimental infection by Trypanosoma cruzi in Cebus apella monkeys

Twenty young male Cebus apella monkeys were infected with CAl Trypanosoma cruzi strain and reinfected with CA l or Tulahuen T.cruzi strains, with different doses and parasite source. Subpatent parasitemia was usually demonstrated in acute and chronic phases. Patent parasitemia was evident in one monkey in the acute phase and in four of them in the chronic phase after re-inoculations with high doses of CAl strain. Serological conversion was observed in all monkeys; titers were low, regardless of the methods used to investigate anti-T. cruzi specific antibodies. Higher titers were induced only when re-inoculations were perfomed with the virulent Tulahuén strain or high doses of CAl strain. Clinical electrocardiographic and ajmaline test evaluations did not reveal changes between infected and control monkeys. Histopathologically, cardiac lesions were always characterized by focal or multifocal mononuclear infiltrates and/or isolated fibrosis, as seen during the acute and chronic phases; neither amastigote nests nor active inflammation and fibrogenic processes characteristic of human acute and chronic myocarditis respectively, were observed. These morphological aspects more closely resemble those found in the "indeterminate phase" and contrast with the more diffuse and progressive pattern of the human chagasic myocarditis. All monkeys survived and no mortality was observed.

Biological characterization of clones derived from the edmonston strain of measles virus in comparison with schwarz and CAM-70 vaccine strains

Four virus clones were derived from the Edmonston strain of measles virus by repeated plaque purification. These clones were compared with the vaccine strains Schwarz and CAM-70 in terms of biological activities including plaque formation, hemagglutination, hemolysis and replication in Vero cells and chick embryo fibroblasts (CEF). Two clones of intermediate plaque yielded mixed plaque populations on subcultivation whereas the other two, showing small and large plaque sizes, showed stable plaque phenotypes. The vaccine strains showed consistent homogeneous plaque populations. All the Edmonston clones showed agglutination of monkey erythrocytes in isotonic solution while both vaccine strains hemagglutinated only in the presence of high salt concentrations. Variation in the hemolytic activity was observed among the four clones but no hemolytic activity was detected for the vaccine virus strains. Vaccine strains replicated efficiently both in Vero cells and CEF. All four clones showed efficient replication in Vero cells but different replication profiles in CEF. Two of them replicated efficiently, one was of intermediate efficiency and the other showed no replication in CEF. Two of the clones showed characteristics similar to vaccine strains. One in terms of size and homogeneity of plaques, the other for a low hemolytic activity and both for the efficiency of propagation in CEF.

Pulmonary biology of anti-interleukin 5 antibodies

Interleukin 5 (IL-5) is a critical cytokine for the maturation of eosinophil precursors to eosinophils in the bone marrow and those eosinophils then accumulate in the lungs during asthma. We have studied anti IL-5 antibodies on allergic responses in mice, guinea pigs and monkeys and are extending this experiment into humans with a humanized antibody. In a monkey model of pulmonary inflammation and airway hyperreactivity, we found that the TRFK-5 antibody blocked both responses for three months following a single dose of 0.3 mg/kg, i.v. This antibody also blocked lung eosinophilia in mice by inhibiting release from the bone marrow. To facilitate multiple dosing and to reduce immunogenicity in humans, we prepared Sch 55700, a humanized antibody against IL-5. Sch 55700 was also active against lung eosinophilia in allergic monkeys and mice and against pulmonary eosinophilia and airway hyperresponsiveness in guinea pigs. Furthermore, as opposed to steroids, Sch 55700 did not cause immunosuppression in guinea pigs. Studies with this antibody in humans will be critical to establishing the therapeutic potential of IL-5 inhibition.