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John C. Beier - One of the best experts on this subject based on the ideXlab platform.
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Plasmodium yoelii Sporozoite infectivity varies as a function of Sporozoite loads in Anopheles stephensi mosquitoes.
The Journal of parasitology, 1997Co-Authors: Charles B. Pumpuni, Chandana Mendis, John C. BeierAbstract:Mechanisms by which Plasmodium Sporozoites survive and maintain their infectivity within the salivary glands of mosquitoes are unknown. In this study we establish a relationship between the number of Sporozoites present in the salivary glands of individual mosquitoes (Sporozoite load) and Sporozoite infectiousness (or "quality") as measured by infections in BALB/c or ICR mice. When Plasmodium yoelii-infected Anopheles stephensi mosquitoes were each allowed to feed on a single mouse, we noted that Sporozoites from mosquitoes with higher Sporozoite loads were more infectious in 13 of 30 (43%) mice. In a second experiment, we inoculated mice with known numbers of Sporozoites from individual mosquitoes. Eleven of 18 (61%) and 16 of 18 (89%) mice that received 25 and 100 Sporozoites, respectively, became infected. For inoculations using 100 Sporozoites, again we noted that Sporozoites from mosquitoes with higher Sporozoite loads were more infectious to mice. In a third and final experiment, the overall infectiousness of Sporozoites from individual mosquitoes was evaluated first by allowing individual mosquitoes to feed on individual mice and then by intravenous inoculations of 100 Sporozoites in a second mouse. There was a significant difference in host infections as a function of Sporozoite loads in 14 of 19 (74%) mice. Analysis of the feeding times for infected versus noninfected mosquitoes did not show a significant difference between the 2 groups. The mean total feeding times for 50 infected and 45 noninfected An. stephensi mosquitoes were 306 (standard deviation [SD] = +/-230) and 441 (SD = +/-273) sec, respectively. Further, among infected An. stephensi mosquitoes there was no difference in probing times between cohorts that transmitted infectious Sporozoites to mice and cohorts that failed to transmit infectious Sporozoites. Our findings that Sporozoite load influences Sporozoite infectiousness or quality suggest that this may be an important factor in malaria parasite transmission.
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Sporozoite loads of naturally infected Anopheles in Kilifi District, Kenya.
Journal of the American Mosquito Control Association, 1997Co-Authors: Ephantus W. Kabiru, Charles M. Mbogo, Samuel K. Muiruri, John H. Ouma, J.i. Githure, John C. BeierAbstract:The number of salivary gland malaria Sporozoites (Sporozoite load) was determined by hemacytometer counts for 2,055 field-collected Anopheles mosquitoes from Kilifi District, Kenya. Of 48 gland-positive Anopheles gambiae s.l., Sporozoite loads ranged from 125 to 79,875, with a geometric mean of 1,743 Sporozoites per infected mosquito. About half of the infected mosquitoes had Sporozoite loads < 1,000. Following hemacytometer examination of salivary gland samples, the same samples were subsequently tested for Plasmodium falciparum circumSporozoite (CS) protein by enzyme-linked immunosorbent assay (ELISA). The confirmation by ELISA of CS protein in 89.6% (43/48) of the salivary gland-positive samples compared to only 1.4% (28/2,007) of the dissection-negative mosquitoes indicated that dissection methods with hemacytometer counts of Sporozoites were adequate for detecting even low numbers of Sporozoites in field-collected mosquitoes. Detection of 17 or fewer Sporozoites in blood meals of 7 freshly bloodfed An. gambiae s.l. provides a further indication that the actual number of Sporozoites transmitted during bloodfeeding may be quite low.
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Noninfectious Sporozoites in the salivary glands of a minimally susceptible anopheline mosquito.
The Journal of parasitology, 1995Co-Authors: Bruce H. Noden, Jefferson A. Vaughan, Charles B. Pumpuni, John C. BeierAbstract:In studies to evaluate vector-malaria parasite relationships, we have found that Anopheles albimanus is minimally susceptible to the rodent malaria parasite Plasmodium yoelii. Normally, less than 10% of A. albimanus develop oocyst infections compared to 80-100% for Anopheles stephensi and Anopheles freeborni mosquitoes. Although Sporozoites produced in A. albimanus invade the salivary glands, they are not infectious to BALB/c or ICR mice. In 11 experiments with Sporozoites from A. albimanus, intravenous inoculations of up to 24,000 Sporozoites in individual mice failed to produce host infections. In contrast, inoculation of 300 Sporozoites obtained from the salivary glands of A. stephensi and A. freeborni always infected mice. The noninfectious Sporozoites from A. albimanus were morphologically similar to the infectious Sporozoites from A. stephensi and yielded 4+ circumSporozoite precipitin reactions when incubated with a monoclonal antibody against the circumSporozoite protein of P. yoelii. The presence of noninfectious Sporozoites in the salivary glands of A. albimanus suggests that this minimally susceptible vector either possesses a toxic factor that abolishes Sporozoite infectiousness or lacks a critical substance needed by the Sporozoite to become infectious. Sporozoite infectiousness was neither attenuated by incubation of infectious Sporozoites with A. albimanus salivary glands nor restored when noninfectious Sporozoites were incubated with A. stephensi salivary glands. These studies provide a starting point for defining the biological basis of Sporozoite infectivity.
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Long-term survival of Plasmodium Sporozoites in vitro
Parasitology research, 1995Co-Authors: Charles B. Pumpuni, John C. BeierAbstract:PIasmodium Sporozoites in mosquitoes are adapted for long-term survival in the salivary glands; however, they quickly lose their infectivity when removed. Previous studies show that the type of media used for holding Sporozoites during experimental manipulations is critical for maintenace of short-term infectivity (Tonkin 1947; Whitman 1948; Porter et al. 1952; Vanderberg 1974). In the mosquito the development of Sporozoite infectivity is time-dependent rather than site-dependent (Vanderberg 1975), and Sporozoite infectivity progressively decreases over time (Boyd et al. 1936; Porter et al. 1954). Furthermore, Sporozoite motility is associated with infectivity and circumSporozoite-precipitate (CSP) reactivity (Vanderberg 1974). Beyond these few key studies, little is known about factors in the mosquito that promote Sporozoite survival and the maintenance of infectivity. As a step toward evaluating the biologic basis of Sporozoite infectivity, we initiated this study to define further in vitro conditions that promote Sporozoites' viability and infectivity. Laboratory-reared Anopheles stephensi (Dutch strain) mosquitoes were fed blood mixed with P. falciparum NF54 gametocyte cultures using standard methods (Ponnudurai et al. 1982), with modifications (Beier et al. 1991). Briefly, a suspension of P. falciparum gametocyte-enriched blood was diluted 1:8 in equal volumes of washed human red cells and heat-inactivated human sera and then placed in a prewarmed (38~ water-jacketed membrane feeder. Mosquitoes fed readily within 15 rain and were subsequently held at 27~ (70% relative humidity) with access to sugar solution. Two rodent malaria parasites used in this study, P. berghei (ANKA) and P. yoelii (17XNL), were maintained in BALB/c mice by blood and Sporozoite passage. After feeding on gametocytemic mice, P. bergheiand P. yoelii-infected A. ste-
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effects of ingested human anti Sporozoite sera on plasmodium falciparum sporogony in anopheles stephensi
American Journal of Tropical Medicine and Hygiene, 1993Co-Authors: Jonathan R. Davis, Charles B. Pumpuni, John C. Beier, Magda S. Beier, Robert R Edelman, D A Herrington, David F ClydeAbstract:Abstract We investigated the effects of human anti-Sporozoite antibodies on the sporogonic development of Plasmodium falciparum in Anopheles stephensi. Equal volumes of washed human erythrocytes and human sera from 1) volunteers with protective immunity induced by immunization with irradiated P. falciparum Sporozoites, 2) the same volunteers before immunization, or 3) Kenyans exposed to natural Sporozoite transmission, were fed to cohorts of P. falciparum-infected A. stephensi on either day 5, 8, or 11 after infection. A fourth group of infected mosquitoes from the same cohort were not refed. In two experiments, the effects of anti-Sporozoite antibodies were evaluated by determining the infection rates and parasite densities for oocysts and salivary gland Sporozoites. There was no evidence that anti-Sporozoite antibodies had any effect on the development or intensity of P. falciparum infection in A. stephensi. However, accelerated oocyst maturation was associated with mosquitoes taking a second blood meal, independent of serum source. Salivary gland Sporozoites from mosquitoes that fed on immune human sera contained bound human IgG, which was detectable by indirect immunofluorescence assay. The infectivity and transmission potential of human IgG-coated Sporozoites is unknown.
Photini Sinnis - One of the best experts on this subject based on the ideXlab platform.
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experimental determination of the force of malaria infection reveals a non linear relationship to mosquito Sporozoite loads
PLOS Pathogens, 2020Co-Authors: Maya Aleshnick, Vitaly V Ganusov, Gibran Nasir, Gayane Yenokyan, Photini SinnisAbstract:Plasmodium Sporozoites are the infective stage of the malaria parasite. Though this is a bottleneck for the parasite, the quantitative dynamics of transmission, from mosquito inoculation of Sporozoites to patent blood-stage infection in the mammalian host, are poorly understood. Here we utilize a rodent model to determine the probability of malaria infection after infectious mosquito bite, and consider the impact of mosquito parasite load, blood-meal acquisition, probe-time, and probe location, on infection probability. We found that infection likelihood correlates with mosquito Sporozoite load and, to a lesser degree, the duration of probing, and is not dependent upon the mosquito’s ability to find blood. The relationship between Sporozoite load and infection probability is non-linear and can be described by a set of models that include a threshold, with mosquitoes harboring over 10,000 salivary gland Sporozoites being significantly more likely to initiate a malaria infection. Overall, our data suggest that the small subset of highly infected mosquitoes may contribute disproportionally to malaria transmission in the field and that quantifying mosquito Sporozoite loads could aid in predicting the force of infection in different transmission settings.
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lymph node resident cd8α dendritic cells capture antigens from migratory malaria Sporozoites and induce cd8 t cell responses
PLOS Pathogens, 2015Co-Authors: Andrea J Radtke, Photini Sinnis, Wolfgang Kastenmuller, Diego A Espinosa, Michael Y Gerner, Ronald N Germain, Fidel P Zavala, Ian A CockburnAbstract:Malaria infection begins when a female Anopheles mosquito injects Plasmodium Sporozoites into the skin of its host during blood feeding. Skin-deposited Sporozoites may enter the bloodstream and infect the liver, reside and develop in the skin, or migrate to the draining lymph nodes (DLNs). Importantly, the DLN is where protective CD8+ T cell responses against malaria liver stages are induced after a dermal route of infection. However, the significance of parasites in the skin and DLN to CD8+ T cell activation is largely unknown. In this study, we used genetically modified parasites, as well as antibody-mediated immobilization of Sporozoites, to determine that active Sporozoite migration to the DLNs is required for robust CD8+ T cell responses. Through dynamic in vivo and static imaging, we show the direct uptake of parasites by lymph-node resident DCs followed by CD8+ T cell-DC cluster formation, a surrogate for antigen presentation, in the DLNs. A few hours after Sporozoite arrival to the DLNs, CD8+ T cells are primed by resident CD8α+ DCs with no apparent role for skin-derived DCs. Together, these results establish a critical role for lymph node resident CD8α+ DCs in CD8+ T cell priming to Sporozoite antigens while emphasizing a requirement for motile Sporozoites in the induction of CD8+ T cell-mediated immunity.
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The skin: where malaria infection and the host immune response begin
Seminars in Immunopathology, 2012Co-Authors: Photini Sinnis, Fidel ZavalaAbstract:Infection by malaria parasites begins with the inoculation of Sporozoites into the skin of the host. The early events following Sporozoite deposition in the dermis are critical for both the establishment of malaria infection and for the induction of protective immune responses. The initial Sporozoite inoculum is generally low, and only a small percentage of these Sporozoites successfully reach the liver and grow to the next life cycle stage, making this a significant bottleneck for the parasite. Recent studies highlight the importance of Sporozoite motility and host cell traversal in dermal exit. Importantly, protective immune responses against Sporozoites and liver stages of Plasmodium are induced by dendritic cells in the lymph node draining the skin inoculation site. The cellular, molecular, and immunological events that occur in the skin and associated lymph nodes are the topic of this review.
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Plasmodium Sporozoites trickle out of the injection site.
Cellular microbiology, 2007Co-Authors: Lucy Megumi Yamauchi, Alida Coppi, Georges Snounou, Photini SinnisAbstract:Plasmodium Sporozoites make a remarkable journey from the skin, where they are deposited by an infected Anopheline mosquito, to the liver, where they invade hepatocytes and develop into exoerythrocytic stages. Although much work has been done to elucidate the molecular mechanisms by which Sporozoites invade hepatocytes, little is known about the interactions between host and parasite before the Sporozoite enters the blood circulation. It has always been assumed that Sporozoites rapidly exit the injection site, making their interactions with the host at this site, brief and difficult to study. Using quantitative PCR, we determined the kinetics with which Sporozoites leave the injection site and arrive in the liver and found that the majority of infective Sporozoites remain in the skin for hours. We then performed sub-inoculation experiments which confirmed these findings and showed that the pattern of Sporozoite exit from the injection site resembles a slow trickle. Last, we found that drainage of approximately 20% of the Sporozoite inoculum to the lymphatics is associated with a significant enlargement of the draining lymph node, a response not observed after intravenous inoculation. These findings indicate that there is ample time for host and parasite to interact at the inoculation site and are of relevance to the pre-erythrocytic stage malaria vaccine effort.
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Transgenic Plasmodium berghei Sporozoites expressing β-galactosidase for quantification of Sporozoite transmission
Molecular and biochemical parasitology, 2005Co-Authors: Sabine Engelmann, Photini Sinnis, Kai MatuschewskiAbstract:Malaria transmission occurs during a blood-meal of an infected Anopheles mosquito. Visualization and quantification of Sporozoites along the journey from the mosquito midgut, where they develop, to the vertebrate liver, their final target organ, is important for understanding many aspects of Sporozoite biology. Here we describe the generation of Plasmodium berghei parasites that express the reporter gene lacZ as a stable transgene, under the control of the Sporozoite-specific CSP promoter. Transgenic Sporozoites expressing β-galactosidase can be simply visualized and quantified in an enzymatic assay. In addition, these Sporozoites can be used to quantify Sporozoites deposited in subcutaneous tissue during natural infection.
Charles B. Pumpuni - One of the best experts on this subject based on the ideXlab platform.
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Plasmodium yoelii Sporozoite infectivity varies as a function of Sporozoite loads in Anopheles stephensi mosquitoes.
The Journal of parasitology, 1997Co-Authors: Charles B. Pumpuni, Chandana Mendis, John C. BeierAbstract:Mechanisms by which Plasmodium Sporozoites survive and maintain their infectivity within the salivary glands of mosquitoes are unknown. In this study we establish a relationship between the number of Sporozoites present in the salivary glands of individual mosquitoes (Sporozoite load) and Sporozoite infectiousness (or "quality") as measured by infections in BALB/c or ICR mice. When Plasmodium yoelii-infected Anopheles stephensi mosquitoes were each allowed to feed on a single mouse, we noted that Sporozoites from mosquitoes with higher Sporozoite loads were more infectious in 13 of 30 (43%) mice. In a second experiment, we inoculated mice with known numbers of Sporozoites from individual mosquitoes. Eleven of 18 (61%) and 16 of 18 (89%) mice that received 25 and 100 Sporozoites, respectively, became infected. For inoculations using 100 Sporozoites, again we noted that Sporozoites from mosquitoes with higher Sporozoite loads were more infectious to mice. In a third and final experiment, the overall infectiousness of Sporozoites from individual mosquitoes was evaluated first by allowing individual mosquitoes to feed on individual mice and then by intravenous inoculations of 100 Sporozoites in a second mouse. There was a significant difference in host infections as a function of Sporozoite loads in 14 of 19 (74%) mice. Analysis of the feeding times for infected versus noninfected mosquitoes did not show a significant difference between the 2 groups. The mean total feeding times for 50 infected and 45 noninfected An. stephensi mosquitoes were 306 (standard deviation [SD] = +/-230) and 441 (SD = +/-273) sec, respectively. Further, among infected An. stephensi mosquitoes there was no difference in probing times between cohorts that transmitted infectious Sporozoites to mice and cohorts that failed to transmit infectious Sporozoites. Our findings that Sporozoite load influences Sporozoite infectiousness or quality suggest that this may be an important factor in malaria parasite transmission.
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Noninfectious Sporozoites in the salivary glands of a minimally susceptible anopheline mosquito.
The Journal of parasitology, 1995Co-Authors: Bruce H. Noden, Jefferson A. Vaughan, Charles B. Pumpuni, John C. BeierAbstract:In studies to evaluate vector-malaria parasite relationships, we have found that Anopheles albimanus is minimally susceptible to the rodent malaria parasite Plasmodium yoelii. Normally, less than 10% of A. albimanus develop oocyst infections compared to 80-100% for Anopheles stephensi and Anopheles freeborni mosquitoes. Although Sporozoites produced in A. albimanus invade the salivary glands, they are not infectious to BALB/c or ICR mice. In 11 experiments with Sporozoites from A. albimanus, intravenous inoculations of up to 24,000 Sporozoites in individual mice failed to produce host infections. In contrast, inoculation of 300 Sporozoites obtained from the salivary glands of A. stephensi and A. freeborni always infected mice. The noninfectious Sporozoites from A. albimanus were morphologically similar to the infectious Sporozoites from A. stephensi and yielded 4+ circumSporozoite precipitin reactions when incubated with a monoclonal antibody against the circumSporozoite protein of P. yoelii. The presence of noninfectious Sporozoites in the salivary glands of A. albimanus suggests that this minimally susceptible vector either possesses a toxic factor that abolishes Sporozoite infectiousness or lacks a critical substance needed by the Sporozoite to become infectious. Sporozoite infectiousness was neither attenuated by incubation of infectious Sporozoites with A. albimanus salivary glands nor restored when noninfectious Sporozoites were incubated with A. stephensi salivary glands. These studies provide a starting point for defining the biological basis of Sporozoite infectivity.
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Long-term survival of Plasmodium Sporozoites in vitro
Parasitology research, 1995Co-Authors: Charles B. Pumpuni, John C. BeierAbstract:PIasmodium Sporozoites in mosquitoes are adapted for long-term survival in the salivary glands; however, they quickly lose their infectivity when removed. Previous studies show that the type of media used for holding Sporozoites during experimental manipulations is critical for maintenace of short-term infectivity (Tonkin 1947; Whitman 1948; Porter et al. 1952; Vanderberg 1974). In the mosquito the development of Sporozoite infectivity is time-dependent rather than site-dependent (Vanderberg 1975), and Sporozoite infectivity progressively decreases over time (Boyd et al. 1936; Porter et al. 1954). Furthermore, Sporozoite motility is associated with infectivity and circumSporozoite-precipitate (CSP) reactivity (Vanderberg 1974). Beyond these few key studies, little is known about factors in the mosquito that promote Sporozoite survival and the maintenance of infectivity. As a step toward evaluating the biologic basis of Sporozoite infectivity, we initiated this study to define further in vitro conditions that promote Sporozoites' viability and infectivity. Laboratory-reared Anopheles stephensi (Dutch strain) mosquitoes were fed blood mixed with P. falciparum NF54 gametocyte cultures using standard methods (Ponnudurai et al. 1982), with modifications (Beier et al. 1991). Briefly, a suspension of P. falciparum gametocyte-enriched blood was diluted 1:8 in equal volumes of washed human red cells and heat-inactivated human sera and then placed in a prewarmed (38~ water-jacketed membrane feeder. Mosquitoes fed readily within 15 rain and were subsequently held at 27~ (70% relative humidity) with access to sugar solution. Two rodent malaria parasites used in this study, P. berghei (ANKA) and P. yoelii (17XNL), were maintained in BALB/c mice by blood and Sporozoite passage. After feeding on gametocytemic mice, P. bergheiand P. yoelii-infected A. ste-
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effects of ingested human anti Sporozoite sera on plasmodium falciparum sporogony in anopheles stephensi
American Journal of Tropical Medicine and Hygiene, 1993Co-Authors: Jonathan R. Davis, Charles B. Pumpuni, John C. Beier, Magda S. Beier, Robert R Edelman, D A Herrington, David F ClydeAbstract:Abstract We investigated the effects of human anti-Sporozoite antibodies on the sporogonic development of Plasmodium falciparum in Anopheles stephensi. Equal volumes of washed human erythrocytes and human sera from 1) volunteers with protective immunity induced by immunization with irradiated P. falciparum Sporozoites, 2) the same volunteers before immunization, or 3) Kenyans exposed to natural Sporozoite transmission, were fed to cohorts of P. falciparum-infected A. stephensi on either day 5, 8, or 11 after infection. A fourth group of infected mosquitoes from the same cohort were not refed. In two experiments, the effects of anti-Sporozoite antibodies were evaluated by determining the infection rates and parasite densities for oocysts and salivary gland Sporozoites. There was no evidence that anti-Sporozoite antibodies had any effect on the development or intensity of P. falciparum infection in A. stephensi. However, accelerated oocyst maturation was associated with mosquitoes taking a second blood meal, independent of serum source. Salivary gland Sporozoites from mosquitoes that fed on immune human sera contained bound human IgG, which was detectable by indirect immunofluorescence assay. The infectivity and transmission potential of human IgG-coated Sporozoites is unknown.
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Ingestion of Plasmodium Falciparum Sporozoites during Transmission by Anopheline Mosquitoes
The American journal of tropical medicine and hygiene, 1992Co-Authors: Magda S. Beier, Charles B. Pumpuni, Jonathan R. Davis, B H Noden, John C. BeierAbstract:We investigated the process of Sporozoite transmission during blood feeding for Anopheles gambiae and An. stephensi experimentally infected with Plasmodium falciparum. When infective mosquitoes were fed 22-25 days postinfection on an anesthetized rat, Sporozoites were detected in the midgut of 96.5% of 57 An. gambiae (geometric mean [GM] = 32.5, range 3-374) and in 96.2% of 26 An. stephensi (GM = 19.5, range 1-345). There were no significant differences between species either in salivary gland Sporozoite loads or in the number of ingested Sporozoites. There was a significant linear relationship between Sporozoite loads and the numbers of ingested Sporozoites for both An. gambiae (r = 0.38) and An. stephensi (r = 0.69). Subsequently, An. gambiae were tested for Sporozoite transmission by allowing them to feed individually on a suspended capillary tube containing 10 microliters of blood. A total of 83.3% of 18 infective mosquitoes transmitted a GM of 5.9 (range 1-36) Sporozoites. The same mosquitoes contained a GM of 23.4 (range 2-165) ingested Sporozoites. The number of ingested Sporozoites was related to Sporozoite loads (r = 0.42) but not to the number of Sporozoites ejected into capillary tubes. Ingested Sporozoites remained in the midgut up to 10 hr after feeding. The comparable numbers of Sporozoites ingested by infective mosquitoes in both experiments indicates that the actual number of Sporozoites transmitted to the vertebrate host during blood feeding is significantly reduced by the blood ingestion process.(ABSTRACT TRUNCATED AT 250 WORDS)
Stephen L Hoffman - One of the best experts on this subject based on the ideXlab platform.
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plasmodium liver load following parenteral Sporozoite administration in rodents
Vaccine, 2013Co-Authors: Ivo H J Ploemen, Stephen L Hoffman, Chris J Janse, Sumana Chakravarty, Geertjan Van Gemert, Takeshi Annoura, Shahid M Khan, Cornelus C Hermsen, Robert W SauerweinAbstract:One of the bottlenecks in the development of a whole Sporozoite malaria vaccine is the route and method of Sporozoite administration. Immunization and challenge of human volunteers by mosquito bites is effective, but cannot be used as a vaccine. Intravenous immunization with Sporozoites is effective in rodents and non-human primates, and being studied in humans, but is not yet used for licensed vaccines for infectious diseases. Intradermal and subcutaneous immunization regimens show a strong decrease in protective efficacy, which in rodents, is associated with a decreased degree of parasite liver infection during immunization. The objective of this study was to explore alternative routes of Sporozoite administration to increase efficiency of liver infection. Using in vivo imaging, we found that IM injection of Sporozoites resulted in a greater parasite liver load compared to ID and SC injection. The use of small inoculation volumes and multiple injections further increased the subsequent liver load. These observations were corroborated in a Plasmodium yoelii model using cryopreserved Sporozoites administered ID. Our findings provide a rationale for the design of clinical trials to optimize needle and syringe administration of Plasmodium falciparum Sporozoites.
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plasmodium yoelii infected a stephensi inefficiently transmit malaria compared to intravenous route
PLOS ONE, 2010Co-Authors: Solomon Conteh, Rana Chattopadhyay, Charles T Anderson, Stephen L HoffmanAbstract:It was recently reported that when mosquitoes infected with P. berghei Sporozoites feed on mice, they deposit approximately 100–300 Sporozoites in the dermis. When we inoculate P. yoelii (Py) Sporozoites intravenously (IV) into BALB/c mice, the 50% infectious dose (ID50) is often less than 3 Sporozoites, indicating that essentially all Py Sporozoites in salivary glands are infectious. Thus, it should only take the bite of one infected mosquito to infect 100% of mice. In human subjects, it takes the bite of at least 5 P. falciparum-infected mosquitoes to achieve 100% blood stage infection. Exposure to 1–2 infected mosquitoes only leads to blood stage infection in approximately 50% of subjects. If mosquitoes carrying Py Sporozoites inoculate 100–300 Sporozoites per bite, and 1 to 2 mosquito bites achieve 50% blood stage infection rates, then this would suggest that the majority of Sporozoites inoculated by mosquitoes into the dermis are not responsible for a productive infection, or that a significant number of Sporozoite-infected mosquitoes do not inoculate any Sporozoites. The objective of this study was to determine if this is the case. We therefore studied the infectivity to mice of the bites of 1, 2, 4, or 5–8 Py-infected mosquitoes. The bite of one Py Sporozoite-infected mosquito caused blood stage infection in 41.4% (12/29) of mice, two bites infected 66.7% (22/33), four bites infected 75% (18/24), and five to eight bites infected 100% (21/21). These findings demonstrate that inoculation of Sporozoites by mosquito bite is much less efficient than IV inoculation of Py Sporozoites by needle and syringe. Such data may have implications for determining the best route and dose of administration to humans of our attenuated P. falciparum Sporozoite vaccine, the scientific basis of which is immunity by bites from irradiated infected mosquitoes, and suggest that the challenge is to develop a method of administration that approximates IV inoculation, not one that mimics mosquito bite.
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characterization of plasmodium falciparum Sporozoite surface protein 2
Proceedings of the National Academy of Sciences of the United States of America, 1992Co-Authors: William O Rogers, Masamichi Aikawa, Anita Malik, Sylvie Mellouk, Kenichiro Nakamura, Miriam D Rogers, Ana Szarfman, Daniel M Gordon, Andreas K Nussler, Stephen L HoffmanAbstract:Immunization of mice with Plasmodium yoelii Sporozoite surface protein 2 (PySSP2) and circumSporozoite protein protects completely against P. yoelii. The amino acid sequence of PySSP2 suggested that the thrombospondin-related anonymous protein (TRAP) [Robson, K. J. H., Hall, J. R. S., Jennings, M. W., Harris, T. J. R., Marsh, K., Newbold, C. I., Tate, V. E. & Weatherall, D. J. (1988) Nature (London) 335, 79-82] is the Plasmodium falciparum homolog of PySSP2. We report data confirming that TRAP is P. falciparum SSP2 (PfSSP2). Murine antibodies against recombinant PfSSP2 identify a 90-kDa protein in extracts of P. falciparum Sporozoites, recognize Sporozoites and infected hepatocytes by immunofluorescence, localize PfSSP2 to the Sporozoite micronemes by immunoelectron microscopy and to the surface membrane by live immunofluorescence, and inhibit Sporozoite invasion and development in hepatocytes in vitro. Human volunteers immunized with irradiated Sporozoites and protected against malaria develop antibody and proliferative T-cell responses to PfSSP2, suggesting that, like PySSP2, PfSSP2 is a target of protective immunity, and supporting inclusion of PfSSP2 in a multicomponent malaria vaccine.
Robert Ménard - One of the best experts on this subject based on the ideXlab platform.
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Role of host cell traversal by the malaria Sporozoite during liver infection
Journal of Experimental Medicine, 2013Co-Authors: Joana Tavares, Nico Van Rooijen, Pauline Formaglio, Sabine Thiberge, Elodie Mordelet, Alexander Medvinsky, Robert Ménard, Rogerio AminoAbstract:Malaria infection starts when the Sporozoite stage of the Plasmodium parasite is injected into the skin by a mosquito. Sporozoites are known to traverse host cells before finally invading a hepatocyte and multiplying into erythrocyte-infecting forms, but how Sporozoites reach hepatocytes in the liver and the role of host cell traversal (CT) remain unclear. We report the first quantitative imaging study of Sporozoite liver infection in rodents. We show that Sporozoites can cross the liver sinusoidal barrier by multiple mechanisms, targeting Kupffer cells (KC) or endothelial cells and associated or not with the parasite CT activity. We also show that the primary role of CT is to inhibit Sporozoite clearance by KC during locomotion inside the sinusoid lumen, before crossing the barrier. By being involved in multiple steps of the Sporozoite journey from the skin to the final hepatocyte, the parasite proteins mediating host CT emerge as ideal antibody targets for vaccination against the parasite.
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Serial Analysis of Gene Expression in Plasmodium berghei salivary gland Sporozoites.
BMC Genomics, 2007Co-Authors: Isabelle Rosinski-chupin, Robert Ménard, Bertrand Boisson, Thomas Chertemps, Sylvie Perrot, Emmanuel Bischoff, Jérôme Briolay, Pierre Couble, Paul Brey, Patricia BaldacciAbstract:BACKGROUND: The invasion of Anopheles salivary glands by Plasmodium Sporozoites is an essential step for transmission of the parasite to the vertebrate host. Salivary gland Sporozoites undergo a developmental programme to express genes required for their journey from the site of the mosquito bite to the liver and subsequent invasion of, and development within, hepatocytes. A Serial Analysis of Gene Expression was performed on Anopheles gambiae salivary glands infected or not with Plasmodium berghei and we report here the analysis of the Plasmodium Sporozoite transcriptome. RESULTS: Annotation of 530 tag sequences homologous to Plasmodium berghei genomic sequences identified 123 genes expressed in salivary gland Sporozoites and these genes were classified according to their transcript abundance. A subset of these genes was further studied by quantitative PCR to determine their expression profiles. This revealed that Sporozoites modulate their RNA amounts not only between the midgut and salivary glands, but also during their storage within the latter. Among the 123 genes, the expression of 66 is described for the first time in Sporozoites of rodent Plasmodium species. CONCLUSION: These novel Sporozoite expressed genes, especially those expressed at high levels in salivary gland Sporozoites, are likely to play a role in Plasmodium infectivity in the mammalian host.
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plasmodium Sporozoite invasion into insect and mammalian cells is directed by the same dual binding system
The EMBO Journal, 2002Co-Authors: Kai Matuschewski, Victor Nussenzweig, A C Nunes, Robert MénardAbstract:Plasmodium Sporozoites, the transmission form of the malaria parasite, successively invade salivary glands in the mosquito vector and the liver in the mammalian host. Sporozoite capacity to invade host cells is mechanistically related to their ability to glide on solid substrates, both activities depending on the transmembrane protein TRAP. Here, we show that loss-of- function mutations in two adhesive modules of the TRAP ectodomain, an integrin-like A-domain and a thrombospondin type I repeat, specifically decrease Sporozoite invasion of host cells but do not affect Sporozoite gliding and adhesion to cells. Irrespective of the target cell, i.e. in mosquitoes, rodents and cultured human or hamster cells, Sporozoites bearing mutations in one module are less invasive, while those bearing mutations in both modules are non-invasive. In Chinese hamster ovary cells, the TRAP modules interact with distinct cell receptors during Sporozoite invasion, and thus act as independently active pass keys. As these modules are also present in other members of the TRAP family of proteins in Apicomplexa, they may account for the capacity of these parasites to enter many cell types of phylogenetically distant origins.
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trap is necessary for gliding motility and infectivity of plasmodium Sporozoites
Cell, 1997Co-Authors: Ali A. Sultan, Andrea Crisanti, Ruth S. Nussenzweig, Ute Frevert, Victor Nussenzweig, Vandana Thathy, Kathryn J H Robson, Robert MénardAbstract:Many protozoans of the phylum Apicomplexa are invasive parasites that exhibit a substrate-dependent gliding motility. Plasmodium (malaria) Sporozoites, the stage of the parasite that invades the salivary glands of the mosquito vector and the liver of the vertebrate host, express a surface protein called thrombospondin-related anonymous protein (TRAP) that has homologs in other Apicomplexa. By gene targeting in a rodent Plasmodium, we demonstrate that TRAP is critical for Sporozoite infection of the mosquito salivary glands and the rat liver, and is essential for Sporozoite gliding motility in vitro. This suggests that in Plasmodium Sporozoites, and likely in other Apicomplexa, gliding locomotion and cell invasion have a common molecular basis.
