Genomic analysis of two phlebotomine sand fly vectors of Leishmania from the New and Old World

Phlebotomine sand flies are of global significance as important vectors of human disease, transmitting bacterial, viral, and protozoan pathogens, including the kinetoplastid parasites of the genus Leishmania, the causative agents of devastating diseases collectively termed leishmaniasis. More than 40 pathogenic Leishmania species are transmitted to humans by approximately 35 sand fly species in 98 countries with hundreds of millions of people at risk around the world. No approved efficacious vaccine exists for leishmaniasis and available therapeutic drugs are either toxic and/or expensive, or the parasites are becoming resistant to the more recently developed drugs. Therefore, sand fly and/or reservoir control are currently the most effective strategies to break transmission. To better understand the biology of sand flies, including the mechanisms involved in their vectorial capacity, insecticide resistance, and population structures we sequenced the genomes of two geographically widespread and important sand fly vector species: Phlebotomus papatasi, a vector of Leishmania parasites that cause cutaneous leishmaniasis, (distributed in Europe, the Middle East and North Africa) and Lutzomyia longipalpis, a vector of Leishmania parasites that cause visceral leishmaniasis (distributed across Central and South America). We categorized and curated genes involved in processes important to their roles as disease vectors, including chemosensation, blood feeding, circadian rhythm, immunity, and detoxification, as well as mobile genetic elements. We also defined gene orthology and observed micro-synteny among the genomes. Finally, we present the genetic diversity and population structure of these species in their respective geographical areas. These genomes will be a foundation on which to base future efforts to prevent vector-borne transmission of Leishmania parasites.

Effect of salivary CYP4EM1 and CYP4EM2 gene silencing on the life span of Chagas disease vector Rhodnius prolixus (Hemiptera, Reduviidae) exposed to sublethal dose of deltamethrin

Control of Chagas disease in endemic countries is primarily accomplished through insecticide spraying for triatomine vectors. In this context, pyrethroids are the first-choice insecticide, and the evolution of insect resistance to these insecticides may represent an important barrier to triatomine control. In insects, cytochrome P450s are enzymes involved in the metabolism of xenobiotics and endogenous chemicals that are encoded by genes divided into different families. In this work, we evaluated the role of three Rhodnius prolixus CYP4EM subfamily genes during blood meal and after deltamethrin exposure. CYP4 gene members were expressed in different insect organs (integument, salivary glands (SGs), midgut, fat body and malpighian tubules) at distinct transcriptional levels. CYP4EM1 gene was highly expressed in the SG and was clearly modulated after insect blood meal. Injection of CYP4EM1dsRNA promoted significant reduction in mRNA levels of both CYP4EM1 and CYP4EM2 genes and induced deleterious effects in R. prolixus nymphs subsequently exposed to sublethal doses of deltamethrin (3.4 or 3.8 ng/nymph treated). The higher dose reduced the survival over time and increased susceptibility of R. prolixus nymphs to deltamethrin. A better understanding of this mechanism can help in developing of more efficient strategies to reduce Trypanosoma cruzi vector transmission in Americas.

Host modulation by a parasite: how Leishmania infantum modifies the intestinal environment of Lutzomyia longipalpis to favor its development

Some reports have described the interference of Leishmania on sand flies physiology, and such behavior most likely evolved to favor the development and transmission of the parasite. Most of these studies showed that Leishmania could modulate the level of proteases in the midgut after an infective blood meal, and decreased proteolytic activity is indeed beneficial for the development of promastigotes in the gut of sand flies. In the present study, we performed a detailed investigation of the intestinal pH in Lutzomyia longipalpis females naturally infected with Leishmania infantum and investigated the production of trypsin by these insects using different approaches. Our results allowed us to propose a mechanism by which these parasites interfere with the physiology of L. longipalpis to decrease the production of proteolytic enzymes. According to our hypothesis L. infantum promastigotes indirectly interfere with the production of trypsin by modulating the mechanism that controls the intestinal pH via the action of a yet non-identified substance released by promastigote forms inside the midgut. This substance is not an acid, whose action would be restrict on to release H⁺ to the medium, but is a substance that is able to interfere with midgut physiology through a mechanism involving pH control. According to our hypothesis, as the pH decreases, the proteolytic enzymes efficiency is also reduced, leading to a decline in the supply of amino acids to the enterocytes: this decline reduces the stimulus for protease production because it is regulated by the supply of amino acids, thus leading to a delay in digestion.

Variability of the salivary proteins of 20 Brazilian populations of Panstrongylus megistus (Hemiptera: Reduviidae: Triatominae)

The objective of the present study was to study variability in the salivary proteins of 20 Panstrongylus megistus populations from different ecotopes and verify whether this variability influenced the intensity of the response to specific anti-saliva antibodies. Electrophoretic analysis of P. megistus saliva showed a complex protein composition and great interpopulation variability. A higher concentration of bands was observed in the 17-29 kDa region. The phenogram constructed from the electrophoretic profiles of the P. megistus study populations revealed the existence of two main groups. However, there was no evident relationship between these groups and geographical regions, ecotopes or hosts. Saliva inoculated by P. megistus during feeding elicited production of low level of anti-saliva antibodies in rabbit. The homologous and heterologous salivary proteins were recognised by serum of rabbit sensitised with saliva from only one population. Qualitative and quantitative differences were observed for recognised bands in the saliva of all eight populations studied by Western blot analysis. The most recognised bands were those of greatest molecular weight (68.0-97.4 kDa).

Anti-complement activity in the saliva of phlebotomine sand flies and other haematophagous insects

The saliva of haematophagous insects has a series of pharmacological activities which may favour blood feeding. In the present study, an inhibitory effect on the complement system was observed in salivary extracts obtained from the phlebotomine sand flies Lutzomyia longipalpis and Lu. migonei. Saliva from Lu. longipalpis was capable of inhibiting both the classical and alternative pathways, while that from Lu. migonei acted only on the former. Other haematophagous insect species were screened for inhibition of the classical pathway. The triatomine bugs Panstrongylus megistus, Triatoma brasiliensis and Rhodnius prolixus were also able to inhibit the classical pathway whereas the mosquito Aedes aegyti and flea Ctenocephalides felis were not. The activity of Lu. longipalpis saliva on the classical pathway was partially characterized. The inhibitor is a protein of Mr 10000-30000 Da, which is very resistant to denaturation by heat. The inhibition of the complement system by phlebotomine sand flies may have a role in the transmission of Leishmania to the vertebrate hosts. The inhibitor molecule is thus a promising component of a vaccine to target salivary immunomodulators.

Molecular cloning and sequencing of salivary gland-specific cDNAs of the blood-sucking bug Triatoma brasiliensis (Hemiptera: Reduviidae)

Haematophagous insects produce pharmacological substances in their saliva to counteract vertebrate host haemostasis events such as coagulation, vasoconstriction and platelet aggregation. To investigate the bioactive salivary molecules of the triatomine bug Triatoma brasiliensis, we produced subtraction-enriched cDNAs of salivary-gland specific genes using suppression subtractive hybridization. Six full-length differentially expressed cDNAs (Tb113, Tb125, Tb152, Tb169, Tb180 and Tb198) were selected, cloned and sequenced. Sequence similarity searches of the databases using the putative amino acid sequence of our clones gave the following results: Tb152 - Triabin, an antithrombin induced platelet aggregation factor found in salivary gland extracts of T. pallidipennis. Tb169 - Pallidipin, an anticollagen induced platelet aggregation factor also found in T. pallidipennis salivary homogenates. Tb180 - Procalin, the major allergen of T. protracta saliva. The other three salivary-gland specific cDNAs produced no obvious homologies. Comparison of these salivary gland-specific cDNAs of with those of other triatomines combined with functional studies using recombinant proteins will allow a better understanding of the co-evolutionary process occurring between these insects and their vertebrate hosts, and may also lead to the discovery of novel antihaemostatic agents.

[Biological potential of Triatoma brasiliensis]

Biological and physiological parameters of Triatoma brasiliensis, Triatoma infestans, and Triatoma pseudomaculata were studied and compared. T. brasiliensis, reared on mice, showed a faster evolutionary cycle from first stage to adult and higher fecundity, when compared to the other species. T. infestans showed the fastest blood intake in both hosts tested, followed by T. brasiliensis and T. pseudomaculata. Clotting tests using salivary gland extracts of T. brasiliensis presented intermediary values of anti-clotting activity when compared to T. infestans and T. pseudomaculata.

Comparison of feeding behaviour of Triatoma infestans, Triatoma brasiliensis and Triatoma pseudomaculata in different hosts by electronic monitoring of the cibarial pump

Feeding behaviour of Triatoma infestans, T. brasiliensis and T. pseudomaculata on pigeons and mice was compared by electronic monitoring of the cibarial pump. The methodology developed permits the study detailed of triatomine feeding behaviour using an artificial feeder as well as on live hosts. T. infestans was the species that fed most rapidly on the two hosts tested (28.03+/-1.6 mg/min for pigeon and 21.33+/-1.7 mg/min for mouse), followed by T. brasiliensis (17.09+/-1.4 mg/min and 13.1+/-1.5 mg/min for pigeon and mouse, respectively) and T. pseudomaculata, (5.23+/-0.6 mg/min and 4.09+/-0.4 mg/min for pigeon and mouse, respectively). The quantity of liquid ingested per stroke of the cibarial pump was 100.7+/-4.1 nl for T. infestans, 69.1+/-2.7 nl for T. brasiliensis and 26.8+/-1.5 nl for T. pseudomaculata. The rate of engorgement in pigeons tended to be greater than that obtained for mice in the three species studied. In the experiments carried out using mice, probing times tended to be longer and interruptions during the meal more prolonged. This reinforces the idea that feeding on mice is more difficult than on pigeons, requiring more contact time to obtain the similar quantity of blood.

Influence of the blood meal source on the development of Triatoma infestans, Triatoma brasiliensis, Triatoma sordida, and Triatoma pseudomaculata (Heteroptera, Reduviidae)

The objective of this study was to determine the influence of the blood meal source on the life cycle and reproductive development of female Triatoma infestans (Klug, 1834), Triatoma brasiliensis Neiva, 1911, Triatoma sordida (Stal, 1859), and Triatoma pseudomaculata Corrga & Espfinola, 1964. In all triatomine species studied the life cycle was shorter for the groups fed on mice than for those fed on pigeons, the range of differences being between 1.5 times (T pseudomaculata and T. infestans) and 2.4 times (T brasiliensis). The mortality rate of nymphs during the life cycle tended to be greater in insects fed on pigeons than in those fed on mice, the differences for T. brasiliensis being statistically significant. Females of T sordida and T pseudomaculata had a greater fecundity than those of T. infestans and T. brasiliensis independently of the blood meal source. The differences of fecundity observed probably reflect differences in the availability of blood in the silvatic ecotopes of these species, meals being more frequent for T. infestans and T brasiliensis, which live at high densities in association with rodents in highly stable ecotopes. Because T. sordida and T. pseudomaculata live in more unstable ecotopes with fewer sources of blood they form small sparse colonies and invest more energy in reproduction than maintenance.

Identification of morphologically similar Rhodnius species (Hemiptera: Reduviidae: Triatominae) by electrophoresis of salivary heme proteins

We examined intraspecific variability in the genus Rhodnius using starch gel electrophoresis of salivary heme proteins. Salivary protein profiles of 8 Rhodnius species (R. prolixus, R. robustus, R. neglectus, R. nasutus, R. ecuadoriensis, R. pallescens, R. pictipes, and R. domesticus) were compared. All species could be distinguished by this technique. The greatest protein polymorphism was found in R. ecuadoriensis, R. nasutus, R. robustus, and R. pictipes, followed by R. prolixus, R. neglectus, R. pallescens, and R. domesticus. This approach was able to distinguish R. prolixus from R. robustus and R. neglectus from R. nasutus, species with extreme phenotypical similarity.

Action of the saliva of Triatoma infestans (Heteroptera: Reduviidae) on sodium channels

Saliva of Triatoma infestans (Klug) produced a progressive reduction in the amplitude of the compound action potential recorded from rat sciatic nerve. The saliva also inhibited the Na+ current on GH3 cells. The data demonstrate that the saliva of T. infestans has an inhibitory effect on Na+ channels. We conclude that this effect may decrease the generation and conduction of nerve action potential, thereby decreasing the sensitivity of the region in which the insect probes, in a manner similar to that of local anesthetics. This study demonstrates such activity in the saliva of hematophagous insects. The adaptive value of this activity is clear, because the quantity of blood obtained by triatomines is limited by the irritation caused during the feeding process.

Differences in saliva composition among three Brazilian populations of Panstrongylus megistus (Hemiptera, Reduviidae)

Comparisons of electrophoretic profiles of triatomines (Panstrongylus megistus) from the Brazilian states of Bahia (BA), Minas Gerais (MG) and Santa Catarina (SC) revealed differences in the composition of the saliva between the three populations. A phenogram constructed on the basis of the most representative electrophoretic banding patterns allowed the specimens tested to be divided into two groups. The BA and SC populations could be completely separated while some individuals from MG could be placed in each group. The BA population presented fewer bands than the MG and SC ones. The populations studied also differed with regard to their degree of association with human habitations (sylvatic, peridomiciliary and/or intradomiciliary) and our results suggest that the proteinaceous composition of the saliva of the three distinct populations of triatomines could be related to the hosts each is likely to encounter.

Salivary heme proteins distinguish Rhodnius prolixus from Rhodnius robustus (Hemiptera: Reduviidae: Triatominae)

Rhodnius prolixus interpopulation variability was studied based on a new approach using salivary heme proteins (nitrophorins) electrophoresis in starch gel. We compared salivary proteins profiles of R. prolixus from three different laboratory colonies from Honduras, Venezuela, Brazil and Rhodnius robustus from Venezuela, constructing a UPGMA. The Honduran and Venezuelan populations could not be distinguished from each other, but the Brazilian population was well separated from the others. The high similarity between Honduran and Venezuelan specimens lends support to current theories that the Central American populations of R. prolixus may have been introduced from a Venezuelan origin. The low polymorphism shown by the Honduran specimens is in agreement with a possible founder effect. This new approach also distinguished R. prolixus populations from R. robustus, species with extreme phenotypical similarity.

Anticoagulant activity of Triatoma infestans and Panstrongylus megistus saliva (Hemiptera/Triatominae)

Salivary gland extract of Triatoma infestans prolonged thrombin time, prothrombin time, and activated partial thromboplastin time, while salivary gland extract of Panstrongylus megistus delayed thrombin time and activated partial thromboplastin time. However, saliva of P. megistus prolonged activated partial thromboplastin time and saliva of T. infestans delayed activated partial thromboplastin time and prothrombin time. T. infestans saliva interferes particularly with activity of factor VIII (intrinsic pathway) and factor V (common pathway), but also affects other factors. Saliva of the triatomine species studied presented distinct SDS-PAGE profiles. These results demonstrate that there are differences in anticoagulant activity and protein composition of triatomine saliva.

[AIDS: the view from Africa]

Epidemiological data on AIDS in several zones in Africa is presented. The clinical and diagnostic aspects of HIV infection in Africa, based on the definition of Bangui's AIDS (1986), are analysed and the criteria is presented. The treatment and follow-up of a patient with infusion by HIV in the African context is discussed. Reference is then made to some data on the status of AIDS in Angola.

Triatoma infestans is more efficient than Panstrongylus megistus in obtaining blood meals on non anaesthetized mice

We compared the influence of bug density in the capacity of Triatoma infestans and Panstrongylus megistus in obtaining blood meal in non anaesthetized mice. The regression analysis for increase in body weight (mg) versus density (no. of bugs/mouse) showed that in experiments with anaesthetized mice (AM), no correlation was observed. In experiments with non anaesthetized mice (NAM) the weight increase was inversely proportional to density. The regression slope for blood meal size on density was less steep for T. infestans than for P. megistus (-1.9 and -3.0, respectively). The average weight increase of P. megistus nymphs in experiments with AM was higher than for T. infestans nymphs; however, in experiments with NAM such results were inverted. Mortality of P. megistus was significantly higher than that of T. infestans with NAM. However, in experiments with AM very low mortality was observed. Considering the mortality and the slope of regression line on NAM, T. infestans is more efficient than P. megistus in obtaining blood meal in similar densities, possibly because it caused less irritation of the mice. The better exploitation of blood source of T. infestans when compared with P. megistus in similar densities, favours the maintenance of a better nutritional status in higher densities. This could explain epidemiological findings in which T. infestans not only succeeds in establishing larger colonies but also dislodges P. megistus in human dwellings when it is introduced in areas where the latter species prevails.

Predation of Biomphalaria glabrata during the development of Belostoma anurum (Hemiptera, Belostomatidae)

Belostoma anurum was reared under laboratory conditions. Specimens were exposed to semi-natural conditions of photo period. The mortality rate was 26.3% during the post embryonic period (38.6 +/- 0.7 days). During this time the average predation of Biomphalaria glabrata was of 99.0 +/- 9.4 snails. The mean increment ratio of length and dry weight per instar was of 1.4 +/- 0.1 and 2.8 +/- 0.5, respectively. The predation by B. anurum adults can be divided into two different periods: phase I (4.8 +/- 1.4 snails/day) and phase II (1.8 +/- 0.5 snails/day). The higher predation in phase I suggested the sexual maturation of the belostomatid.

Effects induced by saliva of the aquatic hemipteran Belostoma anurum on the isolated guinea-pig heart

1. The effects of the saliva of the aquatic hemipteran Belostoma anurum were investigated on the isolated guinea-pig heart, perfused with Locke solution by the Langendorff's method. 2. The electrocardiogram (bipolar lead), the contractile force (g) and coronary flow (ml/min) were simultaneously recorded. 3. The total protein present in the saliva of each belostomatid was 11.17 +/- 2.39 micrograms (N = 10), and SDS-PAGE of the saliva showed a complex protein composition (N = 10). 4. Bolus injections of 0.2 ml saliva obtained from 10 belostomatids elicited complex effects which were divided into two phases (N = 8): an initial phase characterized by sinus bradycardia and/or A-V block associated with a decrease in contractile force and an increase in coronary flow followed by a decrease and a second phase, 0.5-5 min after saliva injection, characterized by a progressive increase in resting tension (ventricular contracture). 5. Since pretreatment of the preparation with atropine or verapamil did not prevent the initial and the late effects (N = 12), we conclude that these effects are not explained either by a muscarinic effect or by a stimulation of calcium channels. 6. Injection of saliva previously mixed with heparin (1000 IU/ml, N = 7), evoked the first but not the second phase (ventricular contracture). 7. Injection of saliva from two belostomatids into the isolated hearts of guinea pigs, not previously treated with heparin, elicited dramatic effects, such as ventricular contracture (N = 6). 8. We suggest that the formation of an acid-base complex (heparin-saliva) would prevent, in part, the toxic effects of the saliva on the heart.

Return ventricular rhythm: new mechanism for tachyarrhythmia

A case study is presented in which the electrocardiographic patterns during tachycardia showed ventricular premature depolarizations with retrograde conduction to the atria probably using a left-sided anomalous pathway and reentry to the ventricles with normal ventricular activation and duplication of the heart rate. This type of tachycardia is being labeled "return ventricular rhythm" and, as far as it is known, this is the first description of its mechanism.

Hemodynamic effects of hypertonic sodium chloride during surgical treatment of aortic aneurysms

Thoracoabdominal aortic surgery with aortic clamping is normally associated with major volemic shifts when the clamp is removed. This study compares the hemodynamic effects of hypertonic (HS) and isotonic (IS) solutions of sodium chloride (NaCl) infusions on the severe hypotension which follows aortic unclamping. Five consecutive patients received HS, and five received IS immediately after aortic unclamping. Blood loss, diuresis, and blood and crystalloid infusions were monitored throughout the operation. Blood gases, and pH, and hematocrit, hemoglobin, and plasma electrolyte levels were controlled during and 24 hours after surgery. Systemic arterial pressure, pulmonary arterial and wedge pressures, cardiac output, and systemic and pulmonary vascular resistance were monitored at the start of the operation, during aortic clamping, immediately after unclamping, immediately after HS or IS NaCl infusion and at the end of the operation. Patients who received HS NaCl exhibited higher pulmonary arterial and wedge pressures, higher cardiac index, and lower systemic and pulmonary vascular resistances immediately after the infusion. These patients required less volume transfusion than patients who received IS NaCl, despite slightly higher blood losses. It is concluded that HS NaCl is useful for the treatment of human hemorrhagic shock.

Standard score assessment on physique and performance of Brazilian athletes in a six tiered competitive sports model

The use of large cross-sectional norms on Brazilian children and youths aged 7 to 18 years within a six level competition plan helps to assess development status and monitor change. Non-athletic prototypes for comparative purposes are illustrated by the use of the lowest competitive level of 18 year olds to assess differences from internationally elite players. The purpose of this study was to establish the efficacy of this practice in male and female basketball and volleyball samples. Comparisons were made on 11 anthropometric and performance variables using percent difference (% delta) and z-score values. The z-scores were highest for height, weight, and jumping ability in both sports groups. The volleyball players were the more linear in physique and the better jumpers. Related to their prototypes the female basketball players had the highest estimated VO2 max (ml kg-1 min-1), and the best values of anaerobic power measures. It is concluded that differences in physique and performance at various levels of competition compared to non-athletic prototypes may be used to infer selective and training factors.

Exercise testing in the latent phase of Chagas' disease

Exercise stress testing was performed in 50 completely asymptomatic patients in the latent phase of Chagas' disease. In 32 (64%) abnormalities were found consisting of either abnormal ST depression, exercise-induced arrhythmias, or chronotropic incompetence. The latter was determined by comparing the heart rate response to 50 age- and sex-matched control patients without serologic evidence of Chagas' disease. In the absence of an adequate control population we can only speculate as to the significance of the ST depression and arrhythmias during exercise. However, chronotropic incompetence may be a specific marker for Trypanosomal infestation in an endemic area. It probably is an early manifestation of autonomic dysfunction secondary to Chagas' disease.