Sialoglycoconjugates in Trypanosoma cruzi-host cell interaction: possible biological model - a review

A number of glycoconjugates, including glycolipids and glycoproteins, participate in the process of host-cell invasion by Trypanosoma cruzi and one of the most important carbohydrates involved on this interaction is sialic acid. It is known that parasite trans-sialidase participates with sialic acid in a coordinated fashion in the initial stages of invasion. Given the importance of these sialogycoconjugates, this review sets out various possible biological models for the interaction between the parasite and mammalian cells that possess a sialylated receptor/ligand system.

Observation on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid

Investigations were carried out on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid. This gregarious female parasitoid infected and or oviposited in only one host and caused 100 por cento mortality of the infected host. However, increase in parasitoid density decreased the progeny production and influenced the sex ratio. The progenies produced were male biased. When host preference was tested by offering oothecae of different species of cockroaches, T. hagenowii showed a predilection towards the oothecae of P. americana, suggestings its host specificity.

The interaction between Poultry and Triatoma infestans Klug, 1834 (Hemiptera: Reduviidae) in an experimental model

This paper compares the predation pressure that ducks and chickens exert on triatomines. For the tests, these birds were placed in individual boxes together with a known number of Triatoma infestans and left to interact from 6 p.m. till the next morning, involving a long lasting period of complete darkness limited by two short-term periods of semi-darkness. There was a shelter which could prevent the bugs from being predated. The number of live and dead triatomines was recorded, considering missing bugs as predated by the birds. Ducks exhibited a greater predatory activity than chickens, that could be due to a long term active period at night while chickens sleep motionless from sunset to dawn. Surviving triatomines that had fed on chickens outnumbered those fed on ducks suggesting that these were less accessible to the triatomine biting. If ducks are better than chickens to detect and eat bugs and to interfere with their feeding in the field, an increase in duck number might help to diminish triatomine density. Further research is needed to determine the feasibility of application of these experimental results.

Interaction between Didelphis albiventris and Triatoma infestans in relation to Trypanosoma cruzi transmission

This paper attempts to prove if a high Trypanosoma cruzi prevalence of opossums might be reached with few potential infective contacts. One non-infected Didelphis albiventris to T. cruzi and 10 infected nymphs of Triatoma infestans were left together during 23 hr in a device that simulated a natural opossum burrow. Twenty-six replicates were perfomed using marsupials and triatomines only once. Potentially infective contacts occurred in all the trials. From the 26 opossums used in trials, 54% did not eat any bug. Of the 260 bugs used, 21% were predated. In the 25 trials involving 205 surving bugs, 36 % of them did not feed. In 15/25 cases, maior ou igual a 60% of the triatomines were able to feed. The parasitological follow-up of 24 opossums showed that among 10 that had eaten bugs, 4 turned out infected and among the 14 that had not predate, 3 (21%) became positive. In sum, 7/24 (29%) of the marsupials acquired the infection after the experiment. This infection rate was similar to the prevalences found for the opossum population of Santiago del Estero, Argentina, suggesting that the prevalences observed in the field might be reached if each marsupial would encounter infected bugs just once in its lifetime.

Trypanosoma cruzi-cardiomyocytes: new contributions regarding a better understanding of this interaction

The present paper summarizes new approaches regarding the progress done to the understanding of the interaction of Trypanosoma cruzi-cardiomyocytes. Mannose receptors localized at the surface of heart muscle cell are involved in binding and uptake of the parasite. One of the most striking events in the parasite-heart muscle cells interaction is the disruption of the actin cytoskeleton. We have investigated the regulation of the actin mRNA during the cytopathology induced in myocardial cells by the parasite. T. cruzi invasion increases calcium resting levels in cardiomyocytes. We have previously shown that Ca2+ ATPase of the sarcoplasmic reticulum (SERCA) is involved in the invasion of T. cruzi in cardiomyocytes. Treating the cells with thapsigargin, a drug that binds to all SERCA ATPases and causes depletion of intracellular calcium stores, we found a 75% inhibition in the T. cruzi-cardiomyocytes invasion.

Flow cytometry as a tool to identify Mycobacterium tuberculosis interaction with the immune system and drug susceptibility

Flow cytometric analysis is a useful and widely employed tool to identify immunological alterations caused by different microorganisms, including Mycobacterium tuberculosis. However, this tool can be used for several others analysis. We will discuss some applications for flow cytometry to the study of M. tuberculosis, mainly on cell surface antigens, mycobacterial secreted proteins, their interaction with the immune system using inflammatory cells recovered from peripheral blood, alveolar and pleura spaces and the influence of M. tuberculosis on apoptosis, and finally the rapid determination of drug susceptibility. All of these examples highlight the usefulness of flow cytometry in the study of M. tuber-culosis infection.

In vitro interaction of Brazilian strains of the Nematode-trapping fungi Arthrobotrys spp. on Panagrellus sp. and Cooperia punctata

In vitro tests were carried out to verify the activity of 26 Brazilian isolates of predatory fungi of the genus Arthrobotrys on a free-living nematode (Panagrellus sp.) and on infective larvae of Cooperia punctata, a parasitic gastrointestinal nematode of cattle. The results showed that the free-living nematode Panagrellus sp. was the most preyed upon, compared to C. punctata, for all the fungal treatments. Also, variable predatory capacity was observed for different fungal isolates belonging to the same genus when applied to different nematode species.

Interaction of Diocleinae Lectins with Glycoproteins Based in Surface Plasmon Resonance

Interaction of glucose/mannose-binding lectins in solution with immobilized glycoproteins was followed in real time using surface plasmon resonance technology. The lectins which share many biochemical and structural features could be clearly differentiated in terms of their specificity for complex glycoconjugates. The most prominent interaction of the lectins with PHA-E comparing with soybean agglutinin, both glycoproteins exhibiting high mannose oligosaccharides, suggests that the whole structure of the glycoproteins themselves, may interfere in affinity. These findings also support the hypothesis that minor amino acid replacements in the primary sequence of the lectins might be responsible for their divergence in fine specificity and biological activities. This is the first report using surface plasmon resonance technology that evidences differences of Diocleinae lectins in respect their fine glycan-specificity.

Interaction between the Intermediate Host of Schistosomiasis in Brazil Biomphalaria glabrata (Planorbidae) and a Possible Competitor Melanoides tuberculata (Thiaridae): I. Laboratory Experiments

The biological control of Biomphalaria glabrata, intermediate host of Schistosoma mansoni, is one the accepted options to fight schistosomiasis. One of the most promising candidates to control B. glabrata is the snail Melanoides tuberculata, a potential competitor. However, the mechanisms of interaction between the two species are not clear. Our objective is to determine if M. tuberculata indeed compete with B. glabrata, using two laboratory experiments. In Experiment 1, we tested the effect of the presence of M. tuberculata on the fecundity and mortality rates of B. glabrata. In Experiment 2, we tested if there was a direct or indirect interaction between the two species. In Experiment 1, M. tuberculata was eliminated after the peak in reproductive activity of B. glabrata. In Experiment 2, B. glabrata produced more egg masses when raised with M. tuberculata. The conditions leading to this unexpected positive effect of M. tuberculata on the fecundity of B. glabrata need further clarification, but emphasize that detailed studies of the interaction between these species in the conditions of the local environment should be considered.

Anionic Sites, Fucose Residues and Class I Human Leukocyte Antigen Fate During Interaction of Toxoplasma gondii with Endothelial Cells

Toxoplasma gondii invades and proliferates in human umbilical vein endothelial cells where it resides in a parasitophorous vacuole. In order to analyze which components of the endothelial cell plasma membrane are internalized and become part of the parasitophorous vacuole membrane, the culture of endothelial cells was labeled with cationized ferritin or UEA I lectin or anti Class I human leukocytte antigen (HLA) before or after infection with T. gondii. The results showed no cationized ferritin and UEA I lectin in any parasitophorous vacuole membrane, however, the Class I HLA molecule labeling was observed in some endocytic vacuoles containing parasite until 1 h of interaction with T. gondii. After 24 h parasite-host cell interaction, the labeling was absent on the vacuolar membrane, but presents only in small vesicles near parasitophorous vacuole. These results suggest the anionic site and fucose residues are excluded at the time of parasitophorous vacuole formation while Class I HLA molecules are present only on a minority of Toxoplasma-containig vacuoles.

Ultrastructural study of the in vitro interaction between Biomphalaria glabrata hemocytes and Schistosoma mansoni miracidia

Biomphalaria glabrata and Schistosoma mansoni relationship was studied by light microscopy (LM) and freeze-fracture replica technique (FFR). We observed very thin cytoplasmic extensions of hemocytes in the LM, which then surround immobilize the miracidia. FFR images showed that the contact site between hemocytes cytoplasmic extensions and the external tegumentary coat involved only superficial layers of miracidia. Numerous vacuoles and filopodia were observed in the hemocyte cytoplasm, the latter binding with those from neighboring cells. In spite of the close interfilopodia contact, no cellular junctions were seen at these sites nor between filopodia-miracidia contact areas. The observed migration of hemocytes and their disposition in layers surrounding the miracidia in vitro correspond to previous studies.

Plasminogen interaction with Trypanosoma cruzi

The ability of Trypanosoma cruzi to interact with plasminogen, the zimogenic form of the blood serin protease plasmin, was examined. Immunohistochemistry studies revealed that both forms, epimastigotes and metacyclic trypomastigotes, were able to fix plasminogen in a lysine dependant manner. This interaction was corroborated by plasminogen activation studies. Both forms of the parasite enhanced the plasminogen activation by tissue-type plasminogen activator.The maximal enhancements obtained were 15-fold and 3.4-fold with epimastigotes and metacyclic trypomastigotes, respectively, as compared to plasminogen activation in absence of cells. Ligand-blotting analysis of proteins extracted with Triton X-114 from a microsomal fraction of epimastigotes revealed at least five soluble proteins and one hydrophobic protein able to bind plasminogen.

Biomphalaria tenagophila/Schistosoma mansoni interaction: premises for a new approach to biological control of schistosomiasis

Biomphalaria tenagophila is very important for schistosomiasis transmission in Brazil. However its mechanisms of interaction with Schistosoma mansoni are still scantly studied. Since this snail displays strains highly susceptible or completely resistant to the parasite infection, the knowledge of that would be a useful tool to understand the mechanism of snail resistance. Particularly, the Taim strain consistently shows absolute resistance against the trematode, and this resistance is a dominant character. A multidisciplinary research group was created aiming at studying B. tenagophila/S. mansoni interaction. The possibility for applying the knowledge acquired to obtain a biological model for the control of S. mansoni transmission in endemic areas is discussed.