Diurnal preference, mood and the response to morning light in relation to polymorphisms in the human clock gene PER3

PER3 gene polymorphisms have been associated with differences in human sleep-wake phenotypes, and sensitivity to light. The aims of this study were to assess: i) the frequency of allelic variants at two PER3 polymorphic sites (rs57875989 length polymorphism: PER3 ⁴, PER3 ⁵; rs228697 SNP: PER3 ^C, PER3 ^G) in relation to sleep-wake timing; ii) the effect of morning light on behavioural/circadian variables in PER3 ⁴ /PER3 ⁴ and PER3 ⁵ /PER3 ⁵ homozygotes. 786 Caucasian subjects living in Northern Italy donated buccal DNA and completed diurnal preference, sleep quality/timing and sleepiness/mood questionnaires. 19 PER3 ⁴ /PER3 ⁴ and 11 PER3 ⁵ /PER3 ⁵ homozygotes underwent morning light administration, whilst monitoring sleep-wake patterns and the urinary 6-sulphatoxymelatonin (aMT6s) rhythm. No significant relationship was observed between the length polymorphism and diurnal preference. By contrast, a significant association was observed between the PER3 ^G variant and morningness (OR = 2.10), and between the PER3 ^G-PER3 ⁴ haplotype and morningness (OR = 2.19), for which a mechanistic hypothesis is suggested. No significant differences were observed in sleep timing/aMT6s rhythms between PER3 ⁵ /PER3 ⁵ and PER3 ⁴ /PER3 ⁴ subjects at baseline. After light administration, PER3 ⁴ /PER3 ⁴ subjects advanced their aMT6s acrophase (p < 0.05), and showed a trend of advanced sleep-wake timing. In conclusion, significant associations were observed between PER3 polymorphic variants/their combinations and both diurnal preference and the response to light.

Maternal immune activation results in complex microglial transcriptome signature in the adult offspring that is reversed by minocycline treatment

Maternal immune activation (MIA) during pregnancy has been linked to an increased risk of developing psychiatric pathologies in later life. This link may be bridged by a defective microglial phenotype in the offspring induced by MIA, as microglia have key roles in the development and maintenance of neuronal signaling in the central nervous system. The beneficial effects of the immunomodulatory treatment with minocycline on schizophrenic patients are consistent with this hypothesis. Using the MIA mouse model, we found an altered microglial transcriptome and phagocytic function in the adult offspring accompanied by behavioral abnormalities. The changes in microglial phagocytosis on a functional and transcriptional level were similar to those observed in a mouse model of Alzheimer's disease hinting to a related microglial phenotype in neurodegenerative and psychiatric disorders. Minocycline treatment of adult MIA offspring reverted completely the transcriptional, functional and behavioral deficits, highlighting the potential benefits of therapeutic targeting of microglia in psychiatric disorders.

Mapping elements distribution in carapace of Caretta caretta: A strategy for biomonitoring contamination in sea turtles?

This study analyzed the carapace distribution of Ca, Cd, Cr, Cu, Mg, Mn, Pb, Sb, U, V and Zn by GF-AAS and ICP-AES in one specimen of Caretta caretta from Mediterranean Sea. Calcium, Mg, Mn, Pb, U, Zn were mainly distributed in the central area while Cd, Cr, Cu, Sb, V in lateral areas. Cadmium, Cr, Mg, Mn, Sb, U and V were different between lateral areas. The different distribution may be related to several exposures during lifetime and/or the shell ossification during growth. Carapace may be a suitable matrix for metal biomonitoring, however, further studies are required to confirm these findings.

First Report of the Root Knot Nematode, Meloidogyne inornata, on Common Bean in Paraná State, Brazil

Common bean (Phaseolus vulgaris F.) is one of the most important crops in Paraná State, which is responsible for almost 10% of the Brazilian production (4). Root knot nematodes, Meloidogyne spp., are common parasites of this crop worldwide, but damage caused by Meloidogyne inornata has not been reported. During a survey of nematode species present on common bean fields in Paraná State, Brazil, galled root samples of cultivars Tuiuiú and Eldorado were submitted, in June 2012, in the Nematology Laboratory from IAPAR, collected in the municipalities of Araucária (25°35'34″S, 49°24'36″W) and Santana do Itararé (23°45'18″S, 49°37'44″W). Plants did not exhibit any above-ground symptoms. The specimens were identified through perineal patterns and esterase phenotypes of 20 adult females extracted from dissected roots (2,3). The population densities observed in the samples were 140 and 700 J2 and eggs per gram of roots, respectively, for both samples. Characteristics were consistent with those described for M. inornata. For example, perineal patterns of M. inornata showed a high dorsal arch, with smooth to wavy striae, similar to those of M. incognita; but no punctate markings between anus and tail terminus were observed. However, from the esterase electrophoresis we obtained the I3 (Rm = 0.83, 1.15, and 1.32) phenotype, typical of M. inornata, a species-specific phenotype used to differentiate this species from M. incognita (1). Moreover, the excretory pore of adult females was located 32.1 (± 5.4) μm from the anterior end, consistent with the M. inornata description (25 to 53 μm) (1). To the best of our knowledge, this is the first report of M. inornata parasitizing common bean roots. This finding has great importance for Brazilian agriculture, since this nematode may damage common bean plants and become an additional problem for this crop. Additional work is necessary in order to elucidate the losses caused by M. inornata on common bean. References: (1) R. M. D. G. Carneiro et al. Nematology 10:123, 2008. (2) P. R. Esbenshade and A. C. Triantaphyllou J. Nematol. 22:10, 1990. (3) K. M. Hartman and J. N. Sasser. Page 115 in: An Advanced Treatise on Meloidogyne, Volume II Methodology. K. R. Barker et al., eds. Raleigh: North Carolina State University Graphics, 1985. (4) MAPA. Feijão, Ministério da Agricultura, Brasil. Retrieved from http://www.agricultura.gov.br/vegetal/culturas/feijao September 05, 2012.

The occurrence of chemical elements and POPs in loggerhead turtles (Caretta caretta): an overview

Chemical elements and persistent organic pollutants (POPs) are globally present in aquatic systems and their potential transfer to loggerhead marine turtles (Caretta caretta) has become a serious threat for their health status. The environmental fate of these xenobiotics may be traced by the analysis of turtles' tissues and blood. Generally, loggerhead turtles exhibited a higher metal load than other turtle species, this could be explained by differences in diet habits being food the main source of exposure. Literature shows that muscle, liver and kidney are most considered for the quantification of chemical elements, while, organic compounds are typically investigated in liver and fat. This paper is an overview of the international studies carried out on the quantification of chemical elements, polychlorinated biphenyls (PCBs), organochlorines (OCs) and perfluorinated compounds (PFCs), in tissues, organs and fluids of C. caretta from the Mediterranean Sea, the Atlantic and the Pacific Oceans.

Fungal infections in recipients of hematopoietic stem cell transplants: results of the SEIFEM B-2004 study--Sorveglianza Epidemiologica Infezioni Fungine Nelle Emopatie Maligne

BACKGROUND

The purpose of our study was to evaluate the incidence and outcome of invasive fungal infection (IFI) among patients who underwent autologous or allogeneic hematopoietic stem cell transplantation (HSCT) at 11 Italian transplantation centers.

METHODS

This cohort-retrospective study, conducted during 1999-2003, involved HSCT patients admitted to 11 tertiary care centers or university hospitals in Italy, who developed IFIs (proven or probable).

RESULTS

Among 3228 patients who underwent HSCT (1249 allogeneic HSCT recipients and 1979 autologous HSCT recipients), IFI occurred in 121 patients (overall incidence, 3.7%). Ninety-one episodes (2.8% of all patients) were due to molds, and 30 (0.9%) were due to yeasts. Ninety-eight episodes (7.8%) occurred among the 1249 allogeneic HSCT recipients, and 23 (1.2%) occurred among the 1979 autologous HSCT recipients. The most frequent etiological agents were Aspergillus species (86 episodes) and Candida species (30 episodes). The overall mortality rate was 5.7% among allogeneic HSCT recipients and 0.4% among autologous HSCT recipients, whereas the attributable mortality rate registered in our population was 65.3% (72.4% for allogeneic HSCT recipients and 34.7% for autologous HSCT recipients). Etiology influenced the patients' outcomes: the attributable mortality rate for aspergillosis was 72.1% (77.2% and 14.3% for allogeneic and autologous HSCT recipients, respectively), and the rate for Candida IFI was 50% (57.1% and 43.8% for allogeneic and autologous HSCT recipients, respectively).

CONCLUSIONS

IFI represents a common complication for allogeneic HSCT recipients. Aspergillus species is the most frequently detected agent in these patients, and aspergillosis is characterized by a high mortality rate. Conversely, autologous HSCT recipients rarely develop aspergillosis, and the attributable mortality rate is markedly lower. Candidemia was observed less often than aspergillosis among both allogeneic and autologous HSCT recipients; furthermore, there was no difference in either the incidence of or the attributable mortality rate for candidemia among recipients of the 2 transplant types.

ELISA and LC-MS/MS methods for determining cyanobacterial toxins in blue-green algae food supplements

The use of natural products as a diet supplement is increasing worldwide but sometimes is not followed by adequate sanitary controls and analyses. Twenty samples of pills and capsules of lyophilised cyanobacteria (blue-green algae), commercialised in Italy as dietary supplements, were found positive at the Vibrio fischeri bioassay. Further analyses with ELISA and LC-MS/MS methods revealed the presence of four microcystin (MC) analogues, MC-LR, -YR, -LA, -RR and two demethylated forms of MC-RR. The highest total microcystin content was 4.5 and 1.4 microg g-1 in pills and capsules, respectively. The ELISA measurements, compared to the LC-MS/MS analyses, showed significantly lower concentrations of microcystins in pills, this confirming a possible ELISA underestimate of mixed microcystins, due to different sensitivities for some toxic analogues.

Microcystin diversity in a Planktothrix rubescens population from Lake Albano (Central Italy)

The cyanobacterium Planktothrix rubescens Anagnostidis & Komarek (previously Oscillatoria rubescens DC ex Gomont) is present in several Italian lakes and it is known to produce cyanotoxins. The dynamics and toxin production of P. rubescens population in Lake Albano, a volcanic crater lake in Central Italy, has been studied for 5 years (January 2001-April 2005). Winter-spring superficial blooms with frequent scums were observed every year. Total microcystin (MC) levels were measured from April 2004 to October 2005 by liquid chromatography-tandem mass spectrometry. MC levels up to 14.2mug/l were measured, with high concentrations found in summer at a 20-25m depth. The intracellular toxin content varied between 1.5 (surface, January 2004) and 0.21pg/cell (surface, May 2004). Six different MCs were detected, the most abundant being two desmethyl-MC-RR isomers. Of the 13 water wells monitored in the Lake Albano area, two of them showed MC contamination during winter, confirming the ability of these toxins to migrate through groundwater towards public water sources. These results highlight the need for further studies on the mobility and fate of these pervasive cyanobacterial toxins.

NK/T-cell lymphomas ‘nasal type’: an Italian multicentric retrospective survey

OBJECTIVE

To evaluate the clinical characteristics and outcome of NK/T-cell lymphoma 'nasal type' developed in Italian patients.

PATIENTS

Between 1997 and 2004, 26 new cases of NK/T-cell lymphoma 'nasal type' were diagnosed in 10 Italian Hematology institutions.

RESULTS

All patients were Caucasian, male/female ratio was 19/7, with a median age of 50 years (range 20-80). In 23 cases presentation at the onset was in the nasal cavity or adjacent structures, in two cases the lymphoma onset with skin lesions was followed successively by rhynopharyngeal dissemination, while the remaining case had bone marrow and lymph node involvement followed by oro-pharyngeal involvement. Regarding the stage of disease: 12 patients were in stage I; six in stage II; eight in stage IV. Diagnosis was based on the finding of a NK/T-cell phenotype at the histological and immunophenotypic examination of oropharyngeal or cutaneous lesions. All patients but one were treated with chemotherapy, alone in nine cases or associated to radiotherapy in 14 cases; two patients had chemotherapy, radiotherapy and surgery, while one patient underwent only surgery. Chemotherapy was anthracycline-based in 17 out of 25 cases. In those patients in whom radiotherapy was performed, radiation dosages ranged between 36 Gy and 47.5 Gy, with a median dosage of 40 Gy. Nine patients (34%) were responsive to the treatments: six patients obtained a complete remission and other three a partial remission. The remaining 17 patients resulted refractory or presented a limited response to therapy. The median disease-free survival was 14 months and the median overall survival time was 9 months.

CONCLUSION

The results of this retrospective survey confirmed that NK/T-cell lymphoma 'nasal type' is a very rare lymphoma in the Italian population, and it is characterized by a very bad prognosis. Due to the rarity of this disease, a standardized therapeutic approach is lacking. More data are needed to know the epidemiology of this kind of lymphoma in Europe.

Multiple resistance of acetolactate synthase and protoporphyrinogen oxidase inhibitors in Euphorbia heterophylla biotypes

Resistance to acetolactate synthase (ALS)-inhibiting herbicides in Brazil has been documented for six species. The probability to select biotypes of Euphorbia heterophylla (EPPHL) with multiple resistance increases in the same order of magnitude as the use of other herbicides belonging to only one mechanism of action. The objectives of this work were to evaluate the distribution of resistant populations (R) in the states of the Parana and Santa Catarina; to determine the existence of populations of EPHHL with multiple resistance to ALS and PROTOX inhibitors, and to confirm the occurrence of cross resistance to compounds of these mechanisms of action. Seeds of EPHHL of areas with suspected resistance had been sampled in 97 places during 2003. In the greenhouse experiment samples of each population were sprayed with imazethapyr or fomesafen, at only one rate. To identify the resistant ones they were sprayed with different levels of the herbicides imazethapyr and fomesafen. Later they were sprayed with diverse herbicides of the same mechanisms of action to confirm the multiple/cross resistance. There is widespread distribution in the region of populations with resistance to ALS inhibitors. Some biotypes demonstrated resistance to herbicides from the two mechanisms of action. The resistance factor (FR), or the relation of resistance between R and susceptible biotypes, confirms the existence of two biotypes of EPHHL with cross resistance to several herbicides inhibitors of ALS and PROTOX.

Successful treatment of Acremonium fungemia with voriconazole

We report two cases of Acremonium fungemia with proven involvement of the skin and probably of the lung in patients who were both undergoing chemotherapy, one for mantle cell lymphoma and the other for acute lymphoblastic leukemia. Both patients failed amphotericin B deoxycholate treatment and were successfully treated with voriconazole with very mild toxicity.

Voriconazole in the management of invasive aspergillosis in two patients with acute myeloid leukemia undergoing stem cell transplantation

The management of invasive aspergillosis in patients with hematological malignancies remains controversial. A major problem is how to manage patients who had invasive aspergillosis during remission induction and consolidation therapy and then undergo SCT. Indeed in these patients the mortality rate related to invasive aspergillosis recurrence remains unacceptably high. We report two cases of patients who underwent remission induction for AML, developed invasive aspergillosis during antifungal prophylaxis with itraconazole, failed amphotericin B deoxycholate and liposomal amphotericin B treatment, were successfully treated with voriconazole and eventually underwent SCT with voriconazole prophylaxis without reactivation of invasive aspergillosis.

Plasmodium falciparum signal sequences: simply sequences or special signals?

The malaria parasite, Plasmodium falciparum, synthesises and exports several proteins inducing morphological and biochemical modifications of erythrocytes during the erythrocytic cycle. The protein trafficking machinery of the parasite is similar to that of other eukaryotic cells in several ways. However, some unusual features are also observed. The secretion of various polypeptides was inhibited when P. falciparum-infected erythrocytes were incubated with Brefeldin A. Immunoelectron microscopy studies revealed substantial morphological changes in the endoplasmic reticulum following exposure of parasitised erythrocytes to the drug. Immunofluorescence studies of Brefeldin A-treated parasites suggest that polypeptide sorting to different intracellular destinations begins at the endoplasmic reticulum. The parasite also secretes polypeptides by a Brefeldin A-insensitive route that bypasses the classical endoplasmic reticulum-Golgi complex pathway.

Fludarabine in combination with cyclophosphamide or with cyclophosphamide plus mitoxantrone for relapsed or refractory low-grade non-Hodgkin's lymphoma

BACKGROUND AND OBJECTIVES

We report the activity of two combinations of fludarabine (FLU), one with cyclophosphamide (FLU/CY) and the second with CY plus mitoxantrone (FLU/CY/MITO). The aim of the study was to evaluate the activity and toxicity of these two schedules in patients with non-Hodgkin's lymphoma (NHL).

DESIGN AND METHODS

Twenty-two patients with recurrent low grade non-Hodgkin's lymphoma (LGL) received FLU/CY (FLU 25 mg/m(2) days 1 to 3, CY 300 mg/m(2) days 1 to 3), and 31 patients received FLU/CY/MITO (FLU 25 mg/m(2) days 1 to 3, CY 300 mg/m(2) days 1 to 3, mitoxantrone 10 mg/m(2) day 1). Patients received antibiotic oral prophylaxis during all treatments and growth factors (G-CSF) when grade III granulocytopenia (WHO scale) occurred.

RESULTS

Of the 53 patients, 31 achieved complete remission (CR) (58%) and 16 partial remission (PR) (30%). Response was similar in both arms of the study. After 3 courses, 77% of patients who achieved CR showed a complete disappearance of disease. Seventy-nine per cent of patients experienced granulocytopenia. Few patients had fever, all without infection. One patient died with fever of unknown origin three months after completion of six courses of treatment.

INTERPRETATION AND CONCLUSIONS

Both treatments were seen to be effective in recurrent low-grade NHL. Antibiotic prophylaxis with G-CSF support seems to reduce treatment-related infection.

Pfsbp1, a Maurer's cleft Plasmodium falciparum protein, is associated with the erythrocyte skeleton

Antibodies from hyperimmune monkey sera, selected by absorption to Plasmodium falciparum-infected erythrocytes, and elution at acidic pH, allowed us to characterize a novel parasite protein, Pfsbp1 (P. falciparum skeleton binding protein 1). Pfsbp1 is an integral membrane protein of parasite-induced membranous structures associated with the erythrocyte plasma membrane and referred to as Maurer's clefts. The carboxy-terminal domain of Pfsbp1, exposed within the cytoplasm of the host cell, interacts with a 35 kDa erythrocyte skeletal protein and might participate in the binding of the Maurer's clefts to the erythrocyte submembrane skeleton. Antibodies to the carboxy- and amino-terminal domains of Pfsbp1 labelled similar vesicular structures in the cytoplasm of Plasmodium chabaudi and Plasmodium berghei-infected murine erythrocytes, suggesting that the protein is conserved among malaria species, consistent with an important role of Maurer's cleft-like structures in the intraerythrocytic development of malaria parasites.

The transport of the histidine-rich protein I from Plasmodium falciparum is insensitive to brefeldin A

During its intraerythrocytic development, Plasmodium falciparum synthesizes several proteins that are exported beyond its membrane. Some of these secreted antigens are involved in the formation of protuberances or knobs, a major virulence factor, at the erythrocyte membrane. Various secreted malarial polypeptides, the transport of which is sensitive to brefeldin A, are translocated in vitro into dog pancreatic microsomes. We present evidence that the histidine-rich protein I (PfHRPI) is secreted by the parasite via a novel pathway, independent of the ER/Golgi apparatus. The secretion of PfHRPI was not blocked by incubation of parasite cultures at 15 degrees C and 20 degrees C or 37 degrees C in the presence of brefeldin A. PfHRPI was not translocated into microsomes in an in vitro translation-translocation cell-free system. Unlike other polypeptides from eukaryotic cells that bypass the ER/Golgi pathway and do not have a signal peptide, PfHRPI has an atypical signal sequence consisting of 21 amino acids, including eight positively charged residues followed by 11 hydrophobic residues. We also found that the unusually charged PfHRPI signal sequence diverts Exp-1, which is usually exported, away from the translocation machinery of microsomal membranes.

Novel secretory pathways in Plasmodium?

The secretion of proteins from intraerythrocytic stages of Plasmodium falciparum into the infected host cell is still poorly understood. A recent proposal that two distinct, mutually exclusive, secretory compartments may exist within the parasite cell has received much attention. Denise Mattei, Gary Ward, Gordon Langsley and Klaus Lingelbach here critically discuss the data on which this model is based, and then they address a more general question: to what extent are unusual aspects of protein secretion in Plasmodium unique among eukaryotic cells?

Limited genetic diversity of Plasmodium falciparum in field isolates from Honduras

The genetic diversity displayed by Plasmodiumfalciparum field isolates, the occurrence of variant forms of the parasite at different frequencies in different geographic areas, and the complexity of the infections represent major obstacles for the development of effective malaria control measures. However, since most of the existing studies have been performed in regions where P. falciparum transmission is high, little is known about the diversity and complexity of parasite populations circulating in areas of low malaria endemicity. We investigated the extent of genetic polymorphism in P. falciparum field isolates from Honduras, a region where its transmission is low and seasonal. Allelic diversity was analyzed in the highly polymorphic parasite genes encoding the merozoite surface proteins- (MSP-1) and -2 (MSP-2) and the glutamate-rich protein (GLURP) by the polymerase chain reaction. Gene polymorphism was also assessed in the EB200 region derived from the highly size polymorphic Pf332 gene. Limited size polymorphism was detected in all genes analyzed, with four and three variants for the MSP-1 and MSP-2 alleles, respectively, and two size variants for the GLURP and Pf332 genes. Moreover, based on the studied genetic markers, most infections consisted of only a few genetically distinct parasite clones. These results suggest that the P. falciparum parasite populations circulating in this region are genetically homogeneous and point to an association between the extent of parasite genetic diversity and the intensity of malaria transmission.

Expression and cellular localization of Trypanosoma cruzi type II DNA topoisomerase

Topoisomerases are enzymes that participate in many cellular functions involving topological manipulation of DNA strands. There are two types of topoisomerases in the cell: (a) type I topoisomerases; and (b) type II topoisomerases (topo II). Previously we have cloned and sequenced the gene encoding Trypanosoma cruzi topo II (TcTOP2). This study group has raised an antiserum against recombinant type II DNA topoisomerase (TctopoII) to study the expression of this gene during T. cruzi differentiation and to determine the cellular location of the enzyme. Western blot analysis showed that T. cruzi TctopoII is expressed in the replicative epimastigotes but not in the infective and non-replicative trypomastigotes. However, slot blot analysis of RNAs extracted from epimastigotes and metacyclic trypomastigotes showed that the mRNA encoding the enzyme is present in both developmental stages of the parasite. Confocal laser microscopy using the antiserum raised against recombinant TctopoII showed that the enzyme is located exclusively in the nucleus of the parasite. Similar results were obtained by immunofluorescence analysis of Crithidia fasciculata. However, monoclonal antisera against the corresponding enzyme extracted from C. fasciculata recognizes a kinetoplast protein in both T. cruzi and Crithidia.

Characterisation of PfSec61, a Plasmodium falciparum homologue of a component of the translocation machinery at the endoplasmic reticulum membrane of eukaryotic cells

Plasmodium falciparum secretes several proteins that cause changes in the erythrocyte membrane enabling it to survive within red blood cells. Little is known of the mechanisms involved in the secretion and targeting of parasite polypeptides to the various cell compartments. The P. falciparum gene homologous to the mammalian Sec61alpha, gene, which encodes a component of the translocation pore in the endoplasmic reticulum of eukaryotic cells, was characterised to investigate the translocation process in the parasite. PfSec61 is present as a unique copy in the parasite genome and was mapped to chromosome 13. It encodes a 40 kDa polypeptide, as shown by immunoblotting and immunoprecipitation of [35S]methionine metabolically-labelled parasite extracts. The deduced amino acid sequence of PfSec61 is 87% similar to the mammalian polypeptide, and the two proteins give similar hydropathy plots. These results strongly suggest that PfSec61 has the same topological orientation and functional role as Sec61alpha. Anti-PfSec61 antibodies were used to investigate the cellular location and kinetics of expression of the polypeptide in the parasite. Immunofluorescence confocal microscopy showed that PfSec61 was located in the parasite cytoplasm, close to the nucleus, in a position consistent with its being in the endoplasmic reticulum.

Biology of Giant Proteins of Plasmodium: Resolution on Polyacrylamide-Agarose Composite Gels

The malaria parasite Plasmodium falciparum that infects humans encodes several extremely large proteins with molecular masses in the hundreds of thousands to megadalton range. Studies on the structure, function and antigenicity of these ;giant proteins' are hindered by the inability to resolve them effectively in conventional polyacrylamide gels. In this report, Jochen Wiesner, Denise Mattei, Artur Scherf and Michael Lanzer describe a convenient gel system, based on a composite polyacrylamide-agarose matrix, which facilitates analysis of giant proteins.

Humoral immune response to the 72 kDa heat shock protein from Plasmodium falciparum in populations at hypoendemic areas of malaria in western Brazilian Amazon

The heat-shock protein Pf72/Hsp70-1 from the human malaria parasite Plasmodium falciparum has been suggested as a potential candidate antigen for a multivalent vaccine. We have investigated the prevalence and levels of IgG antibodies to the recombinant protein PfR44, derived from Pf72/Hsp70-1, in individuals from different age groups living in Candeias do Jamari, an Amazonian town characterized by unstable and hypoendemic malaria transmission. Blood were collected from a household-based random sample comprising 241 people and the sera were comparatively tested against recombinant antigen PfR44 and a detergent-soluble extract of P. falciparum (PfAg-T). The prevalence and levels of IgG antibodies to both recombinant and total P. falciparum antigens were positively correlated with cumulative exposure to malaria, as estimated by the age of the individuals and the duration of their stay in the study area. Nevertheless, correlations between antibody responses to Pf72/Hsp70-1 and the acquisition of protective anti-malarial immunity could not be derived from our data.

Immunogenicity and efficacy trials with Plasmodium falciparum recombinant antigens identified as targets of opsonizing antibodies in the naive squirrel monkey Saimiri sciureus

We have previously shown that Plasmodium falciparum recombinant antigens PfEB200, R23, and Pfi72 consistently inhibit opsonization of infected red blood cells by protective hyperimmune Saimiri sera, indicating that they present target epitopes involved in the phagocytosis of infected red blood cells. We report here an analysis of the immune response elicited in naive squirrel monkeys injected with the individual recombinant antigens or with a mixture of the three antigens combined with a synthetic peptide. In the three administration protocols investigated, there was no evidence for the production of antibody contributing to the phagocytosis of infected red blood cells, contrasting with the increase of opsonizing antibodies elicited by these antigens in monkeys with a prior (> or = 500 days) experience with malaria infection. However, the recombinant antigens were highly immunogenic, inducing specific antibody responses to P. falciparum and to the recombinant antigens. When the monkeys immunized with the antigen combination were challenged with blood-stage parasites, there was substantial protection: three of seven immunized animals self-cured and two others experienced a delayed peak of parasitemia. Taken together with our previous findings, these results suggest that PfEB200, R23, and Pfi72 constitute interesting vaccine candidates, and show that the presence of antibodies promoting phagocytosis of infected red blood cells is not a prerequisite for protection after immunization with these antigens in the Saimiri model.

Expressed var genes are found in Plasmodium falciparum subtelomeric regions

The antigenic variation and cytoadherence of Plasmodium falciparum-infected erythrocytes are modulated by a family of variant surface proteins encoded by the var multigene family. The var genes occur on multiple chromosomes, often in clusters, and 50 to 150 genes are estimated to be present in the haploid parasite genome. Transcripts from var genes have been previously mapped to internal chromosome positions, but the generality of such assignments and the expression sites and mechanisms that control switches of var gene expression are still in early stages of investigation. Here we describe investigations of closely related var genes that occur in association with repetitive elements near the telomeres of P. falciparum chromosomes. DNA sequence analysis of one of these genes (FCR3-varT11-1) shows the characteristic two-exon structure encoding expected var features, including three variable Duffy binding-like (DBL) domains, a transmembrane sequence, and a carboxy-terminal segment thought to anchor the protein product in knobs at the surface of the parasitized erythrocyte. FCR3-varT11-1 cross-hybridizes with var genes located close to the telomeres of many other P. falciparum chromosomes, including a transcribed gene (FCR3-varT3-1) in chromosome 3 of the P. falciparum FCR3 line. The relatively high level transcription from this gene shows that the polymorphic chromosome ends of P. falciparum, which have been proposed to be transcriptionally silent, can be active expression sites for var genes. The pattern of the FCR3-varT11-1 and FCR3-varT3-1 genes are variable between different P. falciparum lines, presumably due to DNA rearrangements. Thus, recombination events in subtelomeric DNA may have a role in the expression of novel var forms.

Cloning and characterisation of a gene from Plasmodium vivax and P. knowlesi: homology with valine-tRNA synthetase

We have previously described a lambdagt11 clone detected by immune screening with a monoclonal antibody (mAb) A12. This mAb is capable of completely blocking Plasmodium vivax transmission in the mosquito vector. An epitope recognised by A12 was mapped to six amino acids (aa) within the translated sequence of this clone. Here, we describe the complete sequence of the gene within which we mapped this epitope. Surprisingly, the translated sequence of the full-length open reading frame shows homology with that of valine-tRNA synthetases (Val-tRS) from other organisms. DNA cross-hybridisation with several of these species was observed by Southern blot. In addition, the corresponding gene has been obtained from the closely related simian malaria parasite, P. knowlesi. The two aa sequences show 66% identity and yet are very divergent from other Val-tRS sequences, apart from conserved blocks related to functional activity. Multiple sequence alignments reflect this dichotomy, as do predicted differences in antigenicity.

Immunogens containing sequences from antigen Pf332 induce Plasmodium falciparum-reactive antibodies which inhibit parasite growth but not cytoadherence

Immunogens based upon sequences from the P. falciparum asexual blood stage antigen Pf332 were assessed for their capacity to induce antibodies inhibiting parasite growth or cytoadherence of infected erythrocytes in vitro. Selection of the Pf332 sequences was based on their reactivity with the human monoclonal antibody (MoAb) 33G2 which inhibits parasite growth as well as cytoadherence in vitro. Octameric multiple antigen peptides (MAP) were assembled based upon either a trimer of the minimal epitope recognized by the MoAb, VTEEI, or a Pf332 sequence including that motif, SVTEEIAEEDK. A dimer of SVTEEIAEEDK was also expressed in Escherichia coli, genetically fused to ZZ, two IgG-binding domains of staphylococcal protein A. Rabbit antibodies elicited by the immunogens reacted with Pf332 in immunofluorescence and in ELISA with Pf332 peptides which were also recognized by MoAb 33G2. The MAP with branched (VTEEI)3 peptide induced the highest titres of P. falciparum-reactive antibodies. In contrast to MoAB 33G2, none of the polyclonal Pf332 reactive sera cross-reacted with repeat sequences of the malaria antigen Pf155/RESA. The polyclonal Pf332-reactive antibodies inhibited parasite growth efficiently but had no or very low inhibitory effect in a cytoadherence assay. Thus, while Pf332 may be an important target for parasite neutralizing antibodies its involvement in cytoadherence is unclear.

Karyotype analysis of virulent Plasmodium falciparum strains propagated in Saimiri sciureus: strain adaptation leads to deletion of the RESA gene

The squirrel monkey, Saimiri sciureus, is an important experimental model for the study of the human malaria parasite Plasmodium falciparum. A detailed karyotype analysis of four different P. falciparum strains propagated in S. sciureus was done using various subtelomeric antigen gene probes. We observed deletion of the complete RESA gene from chromosome 1 in all four strains. Interestingly, a loss of RESA was observed immediately upon adaptation to the squirrel monkey, suggesting that this DNA rearrangement is fundamental for the P. falciparum infection of S. sciureus erythrocytes. However, a RESA-specific gene probe hybridized with chromosome 1 of wild isolates from 28 different patients, indicating that this gene is maintained during infection of humans.

Induction of opsonizing antibodies after injection of recombinant Plasmodium falciparum vaccine candidate antigens in preimmune Saimiri sciureus monkeys

We have previously shown that Plasmodium falciparum recombinant antigens PfEB200, R23, and Pfi72 inhibit opsonization of infected erythrocytes by hyperimmune Saimiri sera, indicating that they contain target epitopes involved in the phagocytosis of infected erythrocytes. We have investigated in this study the immune response of Saimiri monkeys with previous experience of malaria infections (preimmune monkeys) after injection of these recombinant antigens, administered alone or simultaneously. The humoral response to the recombinant antigens was monitored by radioimmunoassay, and the response to P. falciparum blood stages was assayed by immunofluorescence. The relative proportion of protective versus nonprotective immunoglobulin subtypes was investigated by using 3A2/G6 and 3E4/H8 monoclonal antibodies, and the capacity of the antisera to promote in vitro phagocytosis of infected erythrocytes was evaluated. The antigens evoked in most cases a secondary-type antibody response, resulting in important increases in antigen-specific antibody titers and concomitantly in anti-P. falciparum titers. The ratio of 3A2/G6 to 3E4/H8 immunoglobulin subtypes varied with the immunogen used. Opsonizing antibodies were boosted in several animals, the most promising combination being the mixture of PfEB200 and R23 that induced long-lasting production in five of five animals. The detectable opsonizing activity appearing after immunization of the animals was antigen specific, as it was lost after adsorption of the recombinant antigens. The challenge of the animals with blood stage parasites confirmed previous findings showing a correlation between the presence of detectable opsonizing antibodies in serum and protection.

Immunization with the malaria heat shock like protein hsp70-1 enhances transmission to the mosquito

Mosquitoes fed on mice infected with Plasmodium yoelii after an immunization with the i72 recombinant form of the heat shock protein hsp70-1 developed significantly more oocysts than mosquitoes fed on controls. This effect was due to a marked increase in the relative numbers of gametocytes during the early stages of infection. A comparison of blood-induced and sporozoite-initiated infection showed that these gametocytes were derived from merozoites released from the liver. The stimulus for increased gametocyte production is unknown but is likely to be linked with antibody-dependent cellular cytotoxicity and associated cytokine responses.

Plasmodium falciparum: the Pf332 antigen is secreted from the parasite by a brefeldin A-dependent pathway and is translocated to the erythrocyte membrane via the Maurer's clefts

The transport of the megadalton protein Pf332 was studied during the asexual bloodstage development of Plasmodium falciparum. Four mouse monoclonal antibodies, produced against a recombinant polypeptide derived from the Pf332 protein, were used to analyze the kinetics of synthesis, the subcellular location, and transport of this giant molecule to the erythrocyte membrane. After parasite invasion of a red blood cell, the Pf332 antigen is first detected in young trophozoites at the parasitophorous vacuole membrane or in the cytoplasm of the erythrocyte as large vesicle-like structures. The number of vesicles increases during maturation of the parasite and thus forms a rim-like immunofluorescence pattern between the erythrocyte membrane and the parasitophorous vacuole at very late stages. The various anti-Pf332 antibodies react with the surface of erythrocytes infected with very mature parasites (segmenter stage 42-46 hr postinvasion). Immunoelectron microscopic analysis shows that the Pf332 antigen is transported in association with Maurer's clefts in the cytoplasm of the erythrocyte. This transport could be completely blocked by Brefeldin A, resulting in the accumulation of the antigen within the parasite. These data strongly suggest that the Pf332 antigen is exported to the erythrocyte cytoplasm via the classical Golgi secretory pathway.

Fusion between large phagocytic vesicles: targeting of yeast and other particulates to phagolysosomes that shelter the bacterium Coxiella burnetii or the protozoan Leishmania amazonensis in Chinese hamster ovary cells

This report examines the fusion of phagocytic vesicles with the large phagolysosome-like vacuoles induced in Chinese hamster ovary cells by the bacterium Coxiella burnetti or the Protozoan flagellate Leishmania amazonensis. Infection by these organisms is compatible with cell survival and multiplication. Fusion was inferred from the transfer of microscopically identifiable particles from donor to target vesicles. Donor vesicles contained heat-killed yeast, zymosan, beta-glucan or latex beads taken up by the host cells. Yeast and zymosan were also coated with Concanavalin A to increase their uptake by the cells (Goldman, R., Exp. Cell Res. 104, 325–334, 1977). Particle localization, routinely ascertained by phase-contrast microscopy, was confirmed by confocal laser fluorescence and by transmission electron microscopy. Coxiella vacuoles admitted all the particles tested and transfer took place whether the particles were given to the cells prior to or after infection. Transfer of uncoated or Concanavalin-A-coated yeast or zymosan was dependent on the number of particles ingested and on the incubation period (between 2 and 24 hours). Furthermore, the transfer step was quite efficient, since over 85% of the particles ingested entered Coxiella vacuoles at all particle to cell ratios examined. The fraction of uncoated or Concanavalin-A-coated yeast or zymosan transferred to Leishmania vacuoles was consistently lower and diminished at higher particle loads. In addition, only rarely did latex beads enter these vacuoles. The models proposed may be useful for the delineation of biochemical and molecular mechanisms involved in the fusion of large phagocytic vesicles and the modulation of the latter by cellular and pathogen-derived signals.

Interchromosomal exchange of a large subtelomeric segment in a Plasmodium falciparum cross

Duplications and interchromosomal transpositions of chromosome segments are implicated in the genetic variability of Plasmodium falciparum malaria parasites. One parasite clone, HB3, was shown to lack a subtelomeric region of chromosome 13 that normally carries a PfHRPIII gene. We show here that the chromosome 13 segment carrying PfHRPIII was replaced in HB3 by a duplicated terminal segment from chromosome 11. Mapping results indicate that the segment includes at least 100-200 kb of subtelomeric DNA and contains duplicated copies of the Pf332 and RESA-2 genes. We followed inheritance of this duplication in a genetic cross between the HB3 and another P.falciparum clone, Dd2, that is euploid for the Pf332, RESA-2 and PfHRPIII genes. Three types of progeny from the cross showed expected inheritance forms: a Dd2 euploid parent type, an HB3 aneuploid parent type, and a recombinant euploid type that carried PfHRPIII from Dd2 chromosome 13 and Pf332 from HB3 chromosome 11. However, a fourth euploid progeny type was also observed, in which the chromosome 13 segment from HB3 was transposed back to replace the terminus of chromosome 11. Three of 14 individual progeny were of this type. These findings suggest a mechanism of recombination from subtelomeric pairing and exchange between non-homologous chromosomes in meiosis.

Subtelomeric chromosome instability in Plasmodium falciparum: short telomere-like sequence motifs found frequently at healed chromosome breakpoints

The stability of chromosome ends of the human malaria parasite P. falciparum was analysed using a polymerase chain reaction (PCR) assay that detects potential chromosome breaks that have been healed by the addition of telomere repeats. The data show that the Pf332 and Pf87 genes located in subtelomeric positions of chromosomes 3 and 11, respectively, represent fragile sites. Breakpoints were observed in different regions of these genes. In the broken genes, the DNA sequences preceding the telomere addition sites generally have complementarity to the predicted RNA template of a P. falciparum telomerase ribonucleoprotein enzyme complex. We propose a model for the creation of new telomeres in P. falciparum adjacent to broken ends containing short telomere-like sequence motifs.

Brefeldin A inhibits transport of the glycophorin-binding protein from Plasmodium falciparum into the host erythrocyte

Plasmodium falciparum, a protozoan parasite of the human erythrocyte, causes the most severe form of malaria. During its intraerythrocytic development, the parasite synthesizes proteins which are exported into the host cell. The compartments involved in the secretory pathway of P. falciparum are still poorly characterized. A Golgi apparatus has not been identified, owing to the lack of specific protein markers and Golgi-specific post-translational modifications in the parasite. The fungal metabolite brefeldin A (BFA) is known to inhibit protein secretion in higher eukaryotes by disrupting the integrity of the Golgi apparatus. We have used the parasite-encoded glycophorin-binding protein (GBP), a soluble protein found in the host cell cytoplasm, as a marker to investigate the effects of BFA on protein secretion in the intracellular parasite. In the presence of BFA, GBP was not transported into the erythrocyte, but remained inside the parasite cell. The effect caused by BFA was reversible, and the protein could be chased into the host cell cytoplasm within 30 min. Transport of GBP from the BFA-sensitive site into the host cell did not require protein synthesis. Similar observations were made when infected erythrocytes were incubated at 15 degrees C. Incubation at 20 degrees C resulted in a reduction rather than a complete block of protein export. The relevance of our findings to the identification of compartments involved in protein secretion from the parasite cell is discussed.

Characterization of a Plasmodium falciparium mutant that has deleted the majority of the gametocyte-specific Pf11-1 locus

We identified a gametocyte-specific protein of Plasmodium falciparum called Pf11-1 and provide experimental evidence that this molecule is involved in the emergence of gametes of the infected erythrocyte (gametogenesis). A mutant parasite clone, which has deleted over 90% of the Pf11-1 gene locus, was an important control to establish the gametocyte-specific expression of the Pf11-1. Molecular analysis of the Pf11-1 deletion indicates that it is presumably due to a chromosome breakage with subsequent 'healing' by the addition of telomeric heptanucleotides. Moreover, similar DNA rearrangements are observed in most of the laboratory isolates during asexual propagation in vitro.

Demonstration of heat-shock protein 70 in the sporozoite stage of malaria parasites

Three monoclonal antibodies generated by immunization of mice with Plasmodium berghei-infected red blood cells were found to react with the 75-kDa heat-shock protein (HSP70) present in liver stages and erythrocytic forms of the parasites. These antibodies were shown to react with a recombinant protein encoding the carboxyl terminal half of PfHSP70 (aa 365-681). Differently from earlier results, we clearly demonstrated that HSP70 was also expressed in the sporozoite stage, using these monoclonal antibodies in an immunofluorescence and Western immunoblot assay. These monoclonal antibodies react not only with sporozoites of P. berghei, the parasites originally used for the immunization, but also with sporozoites of several other rodent and human plasmodial species. Passive transfer of these monoclonal antibodies into naive mice, simultaneously injected with sporozoites, failed to neutralize the infectivity of P. berghei sporozoites and to inhibit the development of liver stages of P. yoelii.

In vitro phagocytosis inhibition assay for the screening of potential candidate antigens for sub-unit vaccines against the asexual blood stage of Plasmodium falciparum

We have previously established a direct correlation between immune protection against the asexual blood stage Plasmodium falciparum infection and the presence of opsonizing antibodies promoting phagocytosis of parasitized red blood cells. In the present communication we describe an in vitro assay for measuring phagocytosis inhibition (PIA) specific for P. falciparum-infected erythrocytes. The phagocytosis inhibition assay is a simple procedure for screening potential candidates for sub-unit vaccines against P. falciparum based on the correlation between opsonizing antibodies and immunoprotection. The assay was used to analyse 18 recombinant molecules, corresponding to 11 distinct antigens of P. falciparum. Pre-incubation and selective antibody depletion experiments demonstrate the antigen-antibody specificity of the PIA. The presence of epitopes participating as targets of opsonic antibodies were demonstrated in six distinct polypeptide antigens.

Pfl I-I and Pf332: Two giant proteins synthesized in erythrocytes infected with Plasmodium falciparum

Although the malaria parasite develops within erythrocytes, it has to modify the surrounding red blood cell membrane for its intracellular survival and maturation. These changes include the translocation of proteins across the parasite and the parasitophorous vacuole membranes to the host membrane. In this review, Denise Mattei, Katherine Hinterberg and Artur Scherf focus on two distinct giant parasite molecules of unprecedented size (approximately one MDa), called Pf332 and PflI-I, that are synthesized and exported into the cytoplasm of the host cell in the asexual and sexual blood stages of Plasmodium falciparum, respectively. The corresponding genes are located in genetically unstable subtelomeric chromosome regions.

Gene inactivation of Pf11-1 of Plasmodium falciparum by chromosome breakage and healing: identification of a gametocyte-specific protein with a potential role in gametogenesis

We report the identification of the product of the Plasmodium falciparum Pf11-1 gene and demonstrate that it is a gametocyte-specific protein that has a potential role in the rupture of the host erythrocyte and emergence of the gametes (gametogenesis). The Pf11-1 gene is a large locus (30 kb) whose sequence predicts a glutamic acid-rich polypeptide. Our identification of the Pf11-1 gene product as gametocyte specific was greatly facilitated by the isolation of a mutant parasite clone in which greater than 90% of the Pf11-1 gene was deleted. Molecular analysis of the mutant locus suggests that the underlying genetic mechanism is chromosome breakage and subsequent healing by the addition of telomere repeats. PCR-based analysis showed that similar DNA rearrangements occur commonly in small subpopulations of most laboratory strains, suggesting that the Pf11-1 locus represents a fragile chromosome region. Northern blot analysis demonstrates that a large Pf11-1 gene-specific transcript (much greater than 10 kb) is present in gametocytes but not in asexual blood stage parasites. The Pf11-1 protein was localized by electron microscopy to granules in the cytoplasm of gametocytes adjacent to the membrane of the parasitophorous vacuole. Following in vitro stimulation of gametogenesis, the Pf11-1 protein was found in the membrane of lysed erythrocytes, suggesting a role for Pf11-1 in erythrocyte rupture within the mosquito gut.

Cloning and characterization of chromosome breakpoints of Plasmodium falciparum: breakage and new telomere formation occurs frequently and randomly in subtelomeric genes

We analysed the genetic stability of two subtelomeric genes of the human malaria parasite Plasmodium falciparum. A PCR based assay, using a telomere and a target-gene specific primer was used to detect potential chromosome rearrangements. We show that chromosome breakage and the formation of new telomeres occur frequently in the two genes coding for histidine rich proteins (HRP I and HRP II) in laboratory isolates, but remains undetectable in clinical parasite isolates. This finding suggests an essential role of these genes in vivo and that chromosome breakage is rather an accidental process than a programmed chromosome fragmentation. Cloning and sequencing of 8 chromosome breakpoints of the HRP II gene from one parasite isolate shows that the breakage occurs within a broad region in which new telomere formation appear to take place at random sites. Furthermore, this analysis revealed no obvious sequence similarities of sites of telomere addition. Finally, we show that an irregular pattern of heterogeneous telomere repeats is added at each broken end and that each healed chromosome contains a distinct pattern of repeats. We discuss a model for telomere formation in P. falciparum.

Involvement of Pf155/RESA and cross-reactive antigens in Plasmodium falciparum merozoite invasion in vitro

Lines of Plasmodium falciparum FCR3 either expressing or not expressing the blood-stage antigen Pf155/RESA were used to analyze the possible involvement of this antigen in the merozoite invasion process in vitro. Antibodies from human sera, affinity purified on synthetic peptides corresponding to C-terminal repeated sequences in Pf155/RESA, were shown to inhibit merozoite invasion of both types of parasites with similar efficiency. Reversal of the invasion inhibition by fusion proteins containing repeated sequences of Pf155/RESA but not of the cross-reactive antigens Ag332 and Pf11.1 indicated that the inhibitory antibodies had similar target antigens in both Pf155/RESA+ and Pf155/RESA- parasites that involved cross-reacting epitopes present in Pf155/RESA. Rabbit antibodies specific for Pf155/RESA repeats inhibited merozoite invasion of Pf155/RESA expressing parasites efficiently but had no or very small effect on the invasion of Pf155/RESA-deficient parasites. In contrast, rabbit antibodies specific for Ag332 repeats as well as human antibodies affinity purified on synthetic Ag332 peptides inhibited merozoite invasion of both types of parasites with high efficiency. A similar inhibition pattern was seen with the human monoclonal antibody 33G2, which has specificity for Ag332 but also cross-reacts with Pf155/RESA and Pf11.1. Taken together, our data suggest that Pf155/RESA and related cross-reactive antigens as well as Ag332 are involved in the merozoite invasion process and may constitute targets for invasion inhibitory antibodies.

The Pf332 gene of Plasmodium falciparum codes for a giant protein that is translocated from the parasite to the membrane of infected erythrocytes

We studied the gene structure of the Plasmodium falciparum antigen 332 (Ag332). The gene size was estimated to be approx. 20 kb based on the large size of both the transcript found in mature asexual blood stage parasites and mung bean nuclease fragment generated from genomic DNA. Sequence analysis of genomic and cDNA clones representing different regions of the Pf332 locus showed that the gene product contains a large number of highly degenerated glutamic acid (Glu)-rich repeats (32% Glu). The gene shows dramatic restriction fragment length polymorphism in various P. falciparum isolates and was mapped to the subtelomeric region of chromosome 11. The recombinant 332 fusion protein reacts strongly with the human monoclonal antibody (mAb) 33G2, which is able to inhibit the cytoadherence of parasitized red blood cells on the melanoma cell line C32 and merozoite invasion in in vitro assays. The epitope recognized by this mAb is found frequently in the reported sequence. Ag332 monospecific antibodies were obtained by immunization of mice with a recombinant fusion protein. These antibodies react with a large parasite molecule with an apparent molecular size of 2500 kDa of trophozoite and schizont-infected erythrocytes on Western blot and by immunoprecipitation analysis. Immunofluorescence studies using a confocal microscope showed that Ag332 is exported from the parasite to the infected red blood cell membrane within large vesicle-like structures of about 1 micron diameter.

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 strains 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 in glutamic acid. Mung been nuclease digestion and Northern blot analysis suggested that the 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.