Immunization with PIII, a fraction of Schistosoma mansoni soluble adult worm antigenic preparation, affects nitric oxide production by murine spleen cells

Nitric oxide (NO) is an important effector molecule involved in immune regulation and defense. NO produced by cytokine-activated macrophages was reported to be cytotoxic against the helminth Schistosoma mansoni. Identification and characterization of S. mansoni antigens that can provide protective immunity is crucial for understanding the complex immunoregulatory events that modulate the immune response in schistosomiasis. It is, then, essential to have available defined, purified parasite antigens. Previous work by our laboratory identified a fraction of S. mansoni soluble adult worm antigenic preparation (SWAP), named PIII, able to elicit significant in vitro cell proliferation and at the same time lower in vitro and in vivo granuloma formation when compared either to SEA (soluble egg antigen) or to SWAP. In the present work we report the effect of different in vivo trials with mice on their spleen cells ability to produce NO. We demonstrate that PIII-immunization is able to significantly increase NO production by spleen cells after in vitro stimulation with LPS. These data suggest a possible role for NO on the protective immunity induced by PIII.

Induction of protective immunity against Schistosoma mansoni infection by antigens purified from PIII, a fraction of adult worm, associated to the downregulation of granuloma formation

This study was performed in order to define Schistosoma mansoni antigens able to function as modulator agents in BALB/c mice granulomatous hypersensitivity to parasite egg. The antigens P-24, P-35 and P-97 were purified by affinity chromatography from a fraction of S. mansoni adult worm antigenic preparation, denominated PIII, involved in the inhibition of granulomatous response to eggs. Immunization of mice with these antigens, in the presence of Corynebacterium parvum and Al(OH)3 as adjuvant, induced a significant protection degree against challenge infection, as observed by the decrease on worm burden recovered from portal system. In vitro blastogenesis assays revealed that purified antigens were able to induce significant proliferation of spleen cells from S. mansoni-infected mice. This protection was correlated to significant decrease in granuloma size induced by PIII. From these results, we concluded that PIII preparation contains antigens capable of mediating protective anti-parasite immunity and down-regulating granulomatous hypersensitivity to S. mansoni eggs.

Morphological study of adult male worms of Schistosoma mansoni Sambon, 1907 by confocal laser scanning microscopy

Aiming to detail data obtained through brightfield microscopy (BM) on reproductive, excretory and digestive system, specimens of Schistosoma mansoni eight weeks old, were recovered from SW mice, stained with Langeron's carmine and analyzed under a confocal laser scanning microscope CLSM 410 (Carl Zeiss). The reproductive system presented a single and lobate testis, with intercommunications between the lobes without efferent duct. Supernumerary testicular lobe was amorphous and isolated from the normal ones. Collecting tubules (excretory ducts), followed by the excretory bladder, opening to the external media through the excretory pore, were observed at the posterior extremity of the body. In the digestive tract, a cecal swelling was noted at the junction that originates the single cecum. It was concluded that through confocal laser scanning microscopy, new interpretations of morphological structures of S. mansoni worms could be achieved, modifying adopted and current descriptions. The gonad consists of a single lobed testis, similar to that observed in some trematode species. Moreover, the same specimens can be observed either by BM or CLSM, considering that the latter causes only focal and limited damage in tissue structures.

Density of Sand Flies (Diptera: Psychodidae) in Domestic and Wild Animal Shelters in an Area of Visceral Leishmaniasis in the State of Rio Grande do Norte, Brazil

The objective of the present study was to determine the association of sand flies with the presence of domestic and wild animals in the peridomiciliary area. The sand flies were collected using direct aspiration and CDC light traps placed in animal shelters. The results suggest that different sand flies species have different behavioral characteristics in an apparent preference for animal baits and that Lutzomyia longipalpis and Lu. evandroi were the most eclectic species regarding their biotope choice. Lu. longipalpis showed a distinct preference for horses and Lu. evandroi for armadillos.

Bloodmeal microfilariae density and the uptake and establishment of Wuchereria bancrofti infections in Culex quinquefasciatus and Aedes aegypti

The relationship between ingestion of microfilariae (mf), production of infective larvae (L3) and mf density in human blood has been suggested as an important determinant in the transmission dynamics of lymphatic filariasis. Here we assess the role of these factors in determining the competence of a natural vector Culex quinquefasciatus and a non vector Aedes aegypti to transmit Wuchereria bancrofti. Mosquitoes were infected via a membrane feeding procedure. Both mosquito species ingested more than the expected number of microfilariae (concentrating factor was 1.28 and 1.81 for Cx. quinquefasciatus and Ae. aegypti, respectively) but Cx. quinquefasciatus ingested around twice as many mf as Ae. aegypti because its larger blood meal size. Ae. aegypti showed a faster mf migration capacity compared to Cx. quinquefasciatus but did not allow parasite maturation under our experimental conditions. Similar proportions of melanized parasites were observed in Ae. aegypti (2.4%) and Cx. quinquefasciatus (2.1%). However, no relationship between rate of infection and melanization was observed. We conclude that in these conditions physiological factors governing parasite development in the thorax may be more important in limiting vectorial competence than the density of mf ingested.

Effects of flooding and temperature on Aedes albifasciatus development time and larval density in two rain pools at Buenos Aires University City

Aedes albifasciatus is a floodwater mosquito that breeds in temporary waters. This semi-domestic species, widely distributed in Argentina, is a competent vector of the western equine encephalitis. The present study was carried out in two rain pools of the city of Buenos Aires, from April 1998 through March 1999. Samples were taken twice a week during the cold season and daily during the warmer months, starting from October. Immature mosquitoes were collected with a dipper, being the number of dippers proportional to the flooded area. The estimated rainfall thresholds to initiate cohorts of Ae. albifasciatus were: 16-17 mm in the fall-winter period, 25 mm in the spring, and 30 mm in the summer. The development time of the different cohorts and the mean air temperature of their respective periods were estimated in all seasons, ranging from six days (at 24ºC) to 32 days (at 13ºC). The equation that best expresses the relationship between development time and mean air temperature is dt =166,27.e-0,1435.T (R²=0,92). Significantly shorter development times were recorded for larvae of the first three stages as compared to the fourth larval stage and pupae.

Adult and nymphs of Microtriatoma trinidadensis (Lent, 1951) (Hemiptera: Reduviidae) caught from peridomestic environment in Bolivia

This is the first report of adult and nymphs (20 nymphs of all stages and 4 adults) of Microtriatoma trinidadensis (Lent 1951) (Hemiptera: Reduviidae: Triatominae) collected in peridomestic environment, in the department of La Paz, Bolivia. These specimens were associated to Rhodnius stali Lent, Jurberg & Galvão 1993. The exceptional finding of M. trinidadensis in peridomestic environment, illustrates the general tendency of triatominae to adapt to human dwellings and dependences.

Morphological aspects of Schistosoma mansoni adult worms isolated from nourished and undernourished mice: a comparative analysis by confocal laser scanning microscopy

Malnutrition hampers the course of schistosomiasis mansoni infection just as normal growth of adult worms. A comparative morphometric study on adult specimens (male and female) recovered from undernourished (fed with a low protein diet - regional basic diet) and nourished (rodent commercial laboratory food, NUVILAB) white mice was performed. Tomographic images and morphometric analysis of the oral and ventral suckers, reproductive system and tegument were obtained by means of confocal laser scanning microscopy. Undernourished male specimens presented smaller morphometric values (length and width) of the reproductive system (first, third and last testicular lobes) and thickness of the tegument than controls. Besides that, it was demonstrated that the dorsal surface of the male worms bears large tubercles unevenly distributed, but kept grouped and flat. At the subtegumental region, vacuolated areas were detected. It was concluded that the inadequate nutritional status of the vertebrate host has a negative influence mainly in the reproductive system and topographical somatic development of male adult Schistosoma mansoni, inducing some alterations on the structure of the parasite.

Preliminary analysis of Sm14 in distinct fractions of Schistosoma mansoni adult worm extract

In previous studies it was shown that the recombinant molecule, r-Sm14, induces high levels of protection against Schistosoma mansoni infection in two outbred animal models and immune crossprotection against infection by Fasciola hepatica in Swiss outbred mice. r-Sm14 was derived from a living worm extract, called SE, and is being developed as the molecular basis of an anti-helminth bivalent vaccine against the two parasites, for medical and veterinary application. Present data refer to SDS-PAGE and Western Blotting analysis of four different preparations of S. mansoni adult worms focusing Sm14 identification. The extracts correspond to the initial fraction of the SE extraction process, containing products released by living worms (SEi); SE2, reextraction of adult worms in PBS; and SE of separated male and female adult worms. In all extracts it was possible to detect the component of 14 kDa, that was recognized by specific anti-rSm14 antibody raised in rabbits.

Ultrastructural alterations in adult Schistosoma mansoni caused by artemether

Progress has been made over the last decade with the development and clinical use of artemether as an agent against major human schistosome parasites. The tegument has been identified as a key target of artemether, implying detailed studies on ultrastructural damage induced by this compound. We performed a temporal examination, employing a transmission electron microscope to assess the pattern and extent of ultrastructural alterations in adult Schistosoma mansoni harboured in mice treated with a single dose of 400 mg/kg artemether. Eight hours post-treatment, damage to the tegument and subtegumental structures was seen. Tegumental alterations reached a peak 3 days after treatment and were characterized by swelling, fusion of distal cytoplasma, focal lysis of the tegumental matrix and vacuolisation. Tubercles and sensory organelles frequently degenerated or collapsed. Typical features of subtegumental alterations, including muscle fibres, syncytium and parenchyma tissues, were focal or extensive lysis, vacuolisation and degeneration of mitochondria. Severe alterations were also observed in gut epithelial cells and vitelline cells of female worms. Our findings of artemether-induced ultrastructural alterations in adult S. mansoni confirm previous results obtained with juvenile S. mansoni and S. japonicum of different ages.

Laboratory evaluation of Mesocyclops annulatus (Wierzejski, 1892) (Copepoda: Cyclopidea) as a predator of container-breeding mosquitoes in Argentina

In laboratory bioassays we tested the predatory capacity of the copepod Mesocyclops annulatus on Aedes aegypti and Culex pipiens larvae. A single adult female of M. annulatus caused 51.6% and 52.3% mortality of 50 first instar larvae of Ae. aegypti and Cx. pipiens respectively, in a 72 h test period. When alternative food was added to the containers, mortality rates declined to 16% and 10.3% for Ae. aegypti and Cx. pipiens respectively. When 50 first instar larvae of each of the two mosquito species tested were placed together with a single adult female of M. annulatus, mortality rates were 75.5% for Ae. aegypti larvae and 23.5% for Cx. pipiens larvae in a three day test period. Different density of adult females of M. annulatus ranged from 5 to 25 females produced mortality rates of Ae. aegypti first instar larvae from 50% to 100% respectively. When a single adult female of M. annulatus was exposed to an increasing number of first-instar Ae. aegypti larvae ranging from 10 to 100, 100% mortality was recorded from 1 to 25 larvae, then mortality declined to 30% with 100 larvae. The average larvae killed per 24 h period by a single copepod were 29.

Reproductive system abnormalities in Schistosoma mansoni adult worms isolated from Nectomys squamipes (Muridae: Sigmodontinae): brightfield and confocal laser scanning microscopy analysis

Schistosoma mansoni adult worms with genital anomalies isolated from Nectomys squamipes (Muridae: Sigmodontinae) were studied by confocal laser scanning microscopy under the reflected mode. One male without testicular lobes (testicular agenesia/anorchism) and two females, one with an atrophied ovary and another with 17 uterine eggs, were identified. The absence of testicular lobes occurred in a worm presenting otherwise normal male adult characteristics: tegument, tubercles and a gynaecophoric canal with spines. In both female specimens the digestive tube showed a vacuolated appearance, and the specimen with supernumerary uterine eggs exhibited a developing miracidium and an egg with a formed shell. The area of the ventral sucker was similar in both specimens however the tegument thickness, ovary and vitelline glands of the specimen with the atrophied ovary were smaller than those of the one with supernumerary eggs. These reported anomalies in the reproductive system call attention to the need to improve our understanding of genetic regulation and the possible role of environmental influences upon trematode development.