Identification of a novel protein localized to the crystalloid of the Plasmodium ookinete.

Reducing Plasmodium parasite transmission via the mosquito vector is a promising strategy for malaria control and elimination in endemic regions. In the mosquito midgut after the ingestion of an infected blood meal, malaria parasite gametes egress from erythrocytes and fertilize to develop into motile ookinetes that traverse midgut epithelial cells and transform into oocysts adjacent the basal lamina. Plasmodium ookinetes and young oocysts possess a unique organelle called the crystalloid; which has a honeycomb-like matrix structure and is indicated to be involved in sporozoite formation and maturation.

Rhoptry neck protein 4 plays important roles during sporozoite infection of the mammalian liver.

During invasion, parasites secrete proteins from rhoptry and microneme apical end organelles, which have crucial roles in attaching to and invading target cells. A sporozoite stage-specific gene silencing system revealed that rhoptry neck protein 2 (RON2), RON4, and RON5 are important for sporozoite invasion of mosquito salivary glands. Here, we further investigated the roles of RON4 during sporozoite infection of the liver .

Vaccine co-display of CSP and Pfs230 on liposomes targeting two Plasmodium falciparum differentiation stages.

A vaccine targeting multiple stages of the Plasmodium falciparum parasite life cycle is desirable. The sporozoite surface Circumsporozoite Protein (CSP) is the target of leading anti-infective P. falciparum pre-erythrocytic vaccines.

PSOP1, putative secreted ookinete protein 1, is localized to the micronemes of Plasmodium yoelii and P. berghei ookinetes.

Plasmodium parasites cause malaria in mammalian hosts and are transmitted by Anopheles mosquitoes. Activated gametocytes in the mosquito midgut egress from erythrocytes followed by fertilization and zygote formation. Zygotes differentiate into motile invasive ookinetes, which penetrate the midgut epithelium before forming oocysts beneath the basal lamina.

Detection of the Rhoptry Neck Protein Complex in Sporozoites and Its Contribution to Sporozoite Invasion of Salivary Glands.

In the life cycle, two infectious stages of parasites, merozoites and sporozoites, share rhoptry and microneme apical structures. A crucial step during merozoite invasion of erythrocytes is the discharge to the host cell membrane of some rhoptry neck proteins as a complex, followed by the formation of a moving junction involving the parasite-secreted protein AMA1 on the parasite membrane. Components of the merozoite rhoptry neck protein complex are also expressed in sporozoites, namely, RON2, RON4, and RON5, suggesting that invasion mechanism elements might be conserved between these infective stages.

The C-terminal region of the Plasmodium yoelii microgamete surface antigen PyMiGS induces potent anti-malarial transmission-blocking immunity in mice.

Malaria transmission-blocking vaccines (TBVs) aim to inhibit parasite fertilization or further development within the mosquito midgut. Because TBV-immunized individuals reduce the transmission of malaria parasites to mosquito vectors, TBVs could serve as a promising strategy to eliminate malaria. We previously reported that a male specific protein, PyMiGS (Plasmodium yoelii microgamete surface protein), is localized to the surface of microgametes and anti-PyMiGS antibodies have strong transmission-blocking activity.

Observation of morphological changes of female osmiophilic bodies prior to Plasmodium gametocyte egress from erythrocytes.

Plasmodium parasites cause malaria in mammalian hosts and are transmitted by Anopheles mosquitoes. Gametocytes, which differentiate from asexual-stage parasites, are activated by environmental changes when ingested into the mosquito midgut, and are rapidly released from erythrocytes prior to fertilization. Secretory proteins localized to osmiophilic bodies (OBs), organelles unique to gametocytes, have been reported to be involved in female gametocyte egress.

Malaria transmission-blocking vaccines: wheat germ cell-free technology can accelerate vaccine development.

: Highly effective malaria vaccines are essential component toward malaria elimination. Although the leading malaria vaccine, RTS,S/AS01, with modest efficacy is being evaluated in a pilot feasibility trial, development of a malaria transmission-blocking vaccine (TBV) could make a major contribution toward malaria elimination. Only a few TBV antigens have reached pre-clinical or clinical development but with several challenges including difficulties in the expression of malaria recombinant proteins and low immunogenicity in humans.

Expression and Localization Profiles of Rhoptry Proteins in Sporozoites.

In the lifecycle two infectious stages of parasites, merozoites, and sporozoites, efficiently infect mammalian host cells, erythrocytes, and hepatocytes, respectively. The apical structure of merozoites and sporozoites contains rhoptry and microneme secretory organelles, which are conserved with other infective forms of apicomplexan parasites. During merozoite invasion of erythrocytes, some rhoptry proteins are secreted to form a tight junction between the parasite and target cell, while others are discharged to maintain subsequent infection inside the parasitophorous vacuole.

Rhoptry neck protein 11 has crucial roles during malaria parasite sporozoite invasion of salivary glands and hepatocytes.

The malaria parasite sporozoite sequentially invades mosquito salivary glands and mammalian hepatocytes; and is the Plasmodium lifecycle infective form mediating parasite transmission by the mosquito vector. The identification of several sporozoite-specific secretory proteins involved in invasion has revealed that sporozoite motility and specific recognition of target cells are crucial for transmission. It has also been demonstrated that some components of the invasion machinery are conserved between erythrocytic asexual and transmission stage parasites.

Rhoptry neck protein 2 expressed in Plasmodium sporozoites plays a crucial role during invasion of mosquito salivary glands.

Malaria parasite transmission to humans is initiated by the inoculation of Plasmodium sporozoites into the skin by mosquitoes. Sporozoites develop within mosquito midgut oocysts, first invade the salivary glands of mosquitoes, and finally infect hepatocytes in mammals. The apical structure of sporozoites is conserved with the infective forms of other apicomplexan parasites that have secretory organelles, such as rhoptries and micronemes.

Evaluation of LIPS (luciferase immunoprecipitation system) for serodiagnosis of Toxoplasmosis.

Development of reliable, quantitative technologies for serodiagnosis of Toxoplasma gondii infection remains desirable. The luciferase immunoprecipitation system (LIPS) is a relatively simple, highly sensitive, and rapid quantitative immunoassay. The major advantages of this assay over ELISA are a wider dynamic range, shorter overall assay time, and less sample volume.

Adhesion of Toxoplasma gondii tachyzoite-infected vehicle leukocytes to capillary endothelial cells triggers timely parasite egression.

Intracellular pathogens have numerous strategies for effective dissemination within the host. Many intracellular pathogens first infect leukocytes, which they use as a vehicle to transport them to target organs. Once at the target organ, intracellular parasite Toxoplasma gondii can cross the capillary wall in extracellular form by infecting endothelial cells.

Theileria annulata seroprevalence among different cattle breeds in Rajshahi Division, Bangladesh.

An epidemiological survey of Theileria annulata infection was undertaken in a cattle population in Rajshahi Division, Bangladesh. The local cattle breeds from the area (North Bengal Gray and Deshi) and crosses between the local breeds and Holstein cattle were predominantly screened. In total, 192 cattle serum samples were collected in two areas of Rajshahi Division, the Rajshahi District (n=147) and Natore District (n=45).

Removal of extracellular Toxoplasma gondii tachyzoites from suspended cell culture.

Tachyzoites of Toxoplasma gondii, an obligate intracellular parasite, actively invade a broad spectrum of cell types. T. gondii infects leukocytes and spreads to distant organs such as the brain, lungs and muscles.

The distribution pattern of α2,3- and α2,6-linked sialic acids affects host cell preference in Toxoplasma gondii.

Tachyzoites of Toxoplasma gondii, an obligate intracellular parasite, actively invade almost all types of nucleated cells. However, T. gondii tachyzoites preferentially infect particular types of animal tissue cells.

Age-specificity of Toxoplasma gondii seroprevalence in sheep, goats and cattle on subsistence farms in Bangladesh.

Toxoplasma gondii is a zoonotic protozoan parasite that infects humans and domestic animals. In this study, the seroprevalence of T. gondii antibodies was investigated using serum samples collected from 83 sheep, 146 goats and 37 cattle from a dozen subsistence farms in Bangladesh.

CD44 mediated hyaluronan adhesion of Toxoplasma gondii-infected leukocytes.

Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects humans and animals. Ingested parasites cross the intestinal epithelium, invade leukocytes and are then disseminated to peripheral organs. However, the mechanism of extravasation of the infected leukocytes remains poorly understood.