The influence of intestinal parasites on Plasmodium vivax-specific antibody responses to MSP-119 and AMA-1 in rural populations of the Brazilian Amazon

BACKGROUND

Polyparasitism is a common condition in humans but its impact on the host immune system and clinical diseases is still poorly understood. There are few studies of the prevalence and the effect of malaria-intestinal parasite co-infections in the immune response to malaria vaccine candidates. The present study determines whether the presence of malaria and intestinal parasites co-infection is associated with impaired IgG responses to Plasmodium vivax AMA-1 and MSP-119 in a rural population of the Brazilian Amazon.

METHODS

A cross-sectional survey was performed in a rural area of Rondonia State and 279 individuals were included in the present study. At recruitment, whole blood was collected and Plasmodium and intestinal parasites were detected by microscopy and molecular tests. Blood cell count and haemoglobin were also tested and antibody response specific to P. vivax AMA-1 and MSP-119 was measured in plasma by ELISA. The participants were grouped according to their infection status: singly infected with Plasmodium (M); co-infected with Plasmodium and intestinal parasites (CI); singly infected with intestinal parasites (IP) and negative (N) for both malaria and intestinal parasites.

RESULTS

The prevalence of intestinal parasites was significantly higher in individuals with malaria and protozoan infections were more prevalent. IgG antibodies to PvAMA-1 and/or PvMSP-119 were detected in 74 % of the population. The prevalence of specific IgG was similar for both proteins in all four groups and among the groups the lowest prevalence was in IP group. The cytophilic sub-classes IgG1 and IgG3 were predominant in all groups for PvAMA-1 and IgG1, IgG3 and IgG4 for PvMSP-119. In the case of non-cytophilic antibodies to PvAMA-1, IgG2 was significantly higher in IP and N group when compared to M and CI while IgG4 was higher in IP group.

CONCLUSIONS

The presence of intestinal parasites, mainly protozoans, in malaria co-infected individuals does not seem to alter the antibody immune responses to P. vivax AMA-1 and MSP-119. However, IgG response to both AMA1 and MSP1 were lower in individuals with intestinal parasites.

Structural studies of BmooMPalpha-I, a non-hemorrhagic metalloproteinase from Bothrops moojeni venom

Hemostatically active snake venom metalloproteinases (SVMPs) perturb the blood coagulation cascade at specific points and due to their potential application as thrombolytic agents, the fibrin(ogen)olytic non-hemorrhagic SVMPs have been employed as biochemical tools in coagulation research and diagnosis. Structural studies complemented by the design of metalloproteinase inhibitors have been instrumental in understanding their stereo specificity and action mechanism. We present here, details of the crystal structure of BmooMPalpha-I, a 22.6 kDa non-hemorrhagic P-I class SVMP isolated from Bothrops moojeni venom, determined at 1.76 A resolution. In this structure, the catalytic zinc ion displays an unusual octahedral coordination formed by the three canonical histidines (His(142), His(146) and His(152)) and additionally, by three solvent molecules. Comparative sequence and structural studies indicate that the motif comprising amino acid segments 153-164 and 167-176 adjacent to the methionine-turn is a salient feature that differentiates both non and hemorrhagic P-I class SVMPs and could directly be involved in the development of the hemorrhagic activity.

Exposure to sublethal concentrations of Zn(II) and Cu(II) changes biochemical parameters in Leporinus obtusidens

The aim of the present study was to assess the effect of the exposure of Leporinus obtusidens (Piava) to zinc and copper on catalase activity in the liver, delta-aminolevulinate dehidratase (delta-ALA-D) activity in liver, muscle, brain and kidney, and thiobarbituric reactive species (TBARS) in brain, muscle and liver. In addition, hematological parameters were measured in blood. The fish were exposed to 10% and 20% of the derived LC(50) values, 2.3 and 4.6 mg Zn l(-1) and 0.02 and 0.04 mg Cu l(-1), and sampled on days 30 and 45. Exposure to Zn(II) and Cu(II) decreased hematological parameters and also delta-ALA-D activity mainly in liver and kidney at all concentrations tested. Liver catalase activity increased after zinc or copper exposure at all concentrations and exposure times tested. Thiobarbituric reactive substances (TBARS) increased in the brain and liver of the fish exposed to zinc(II) for 45 days at both metal concentrations. In muscle, zinc(II) increased TBARS production at both exposure times and concentrations tested. Copper(II) exposure reduced the TBARS levels in liver at both concentrations and times tested. In brain, there was a decrease in TBARS levels only after 45 days of exposure. In muscle, this decrease was observed after 30 days of exposure at both concentrations. Although zinc and copper are required as microelements in the cells, our results showed that the sublethal concentrations of these metals can change biochemical parameters which may alter normal cellular function. These results pointed out the differential sensitivity of fish tissues to essential, but also toxic and environmentally relevant metals. The alterations of distinct biochemical parameters in fish tissues certainly contribute to the toxicity of Zn and Cu, and are of importance for an area that has been growing and has still been poorly explored in the literature.

Primers based on the rpf gene region provide improved detection of Xanthomonas axonopodis pv. citri in naturally and artificially infected citrus plants

AIMS

To have a PCR-based detection method for Xanthomonas axonopodis pv. citri (Xac) using primers designed in a specific region of its genome.

METHODS AND RESULTS

A Xac-specific region was identified inside the rpf gene cluster of strain IAPAR 306 in an analysis of its complete genomic sequence. Two primers were designed, Xac01 and Xac02, which, when used in a standard PCR assay, direct the amplification of a 581 bp fragment from DNA of strains belonging to Xac from different regions around the world including unusual American and Asian strains. This product was not observed when DNA from strains of the closely related X. a. aurantifolli and X. a. citrumelo were used as templates. Extracts prepared from 28 xanthomonads of other species, and epiphytic bacteria isolated from citrus also failed to produce products with these primers. Amplification was obtained from cells grown in vitro, from extracts of both fresh and dried citrus canker lesions and from washes of inoculated but asymptomatic leaf surfaces. In sensitivity tests, this PCR technique detected as few as 100 cells.

CONCLUSIONS

Primers Xac01 and Xac02 provide specific and sensitive detection of Xac in all citrus tissues where the pathogen is found.

SIGNIFICANCE AND IMPACT OF THE STUDY

This PCR-based diagnostic test is suitable for monitoring asymptomatic plants in areas where the bacteria is endemic, in plant quarantine and regulatory situations, and also for obtaining an accurate diagnosis in a very short time. These are important characteristics for any assay to be used for the management of citrus canker disease.

Structure of human uropepsin at 2.45 A resolution

The molecular structure of human uropepsin, an aspartic proteinase from the urine produced in the form of pepsinogen A in the gastric mucosa, has been determined by molecular replacement using human pepsin as the search model. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.99, b = 75.56, c = 89.90 A. Crystallographic refinement led to an R factor of 0.161 at 2.45 A resolution. The positions of 2437 non-H protein atoms in 326 residues have been determined and the model contains 143 water molecules. The structure is bilobal, consisting of two predominantly beta-sheet lobes which, as observed in other aspartic proteinases, are related by a pseudo-twofold axis. A model of the uropepsin-pepstatin complex has been constructed based on the high-resolution crystal structure of pepsin complexed with pepstatin.