scholarly journals Model forIn VivoAssessment of Humoral Protection against Malaria Sporozoite Challenge by Passive Transfer of Monoclonal Antibodies and Immune Serum

2013 ◽  
Vol 82 (2) ◽  
pp. 808-817 ◽  
Author(s):  
Brandon K. Sack ◽  
Jessica L. Miller ◽  
Ashley M. Vaughan ◽  
Alyse Douglass ◽  
Alexis Kaushansky ◽  
...  
Keyword(s):  
Natural Infection ◽  
Passive Transfer ◽  
Plasmodium Yoelii ◽  
Immune Serum ◽  
Liver Stage ◽  
Content Type ◽  
Mosquito Bite ◽  
Infection Inhibition ◽  
Liver Infection

ABSTRACTEvidence from clinical trials of malaria vaccine candidates suggests that both cell-mediated and humoral immunity to pre-erythrocytic parasite stages can provide protection against infection. Novel pre-erythrocytic antibody (Ab) targets could be key to improving vaccine formulations, which are currently based on targeting antigens such as the circumsporozoite protein (CSP). However, methods to assess the effects of sporozoite-specific Abs on pre-erythrocytic infectionin vivoremain underdeveloped. Here, we combined passive transfer of monoclonal Abs (MAbs) or immune serum with a luciferase-expressingPlasmodium yoeliisporozoite challenge to assess Ab-mediated inhibition of liver infection in mice. Passive transfer of aP. yoeliiCSP MAb showed inhibition of liver infection when mice were challenged with sporozoites either intravenously or by infectious mosquito bite. However, inhibition was most potent for the mosquito bite challenge, leading to a more significant reduction of liver-stage burden and even a lack of progression to blood-stage parasitemia. This suggests that Abs provide effective protection against a natural infection. Inhibition of liver infection was also achieved by passive transfer of immune serum from whole-parasite-immunized mice. Furthermore, we demonstrated that passive transfer of a MAb againstP. falciparumCSP inhibited liver-stage infection in a humanized mouse/P. falciparumchallenge model. Together, these models constitute unique and sensitivein vivomethods to assess serum-transferable protection againstPlasmodiumsporozoite challenge.

scholarly journals Chemically Attenuated Blood-Stage Plasmodium yoelii Parasites Induce Long-Lived and Strain-Transcending Protection

2016 ◽  
Vol 84 (8) ◽  
pp. 2274-2288 ◽  
Author(s):  
Amber I. Raja ◽  
Yeping Cai ◽  
Jennifer M. Reiman ◽  
Penny Groves ◽  
Sumana Chakravarty ◽  
...  
Keyword(s):  
T Cells ◽  
Strong Support ◽  
Plasmodium Yoelii ◽  
Blood Stage ◽  
Liver Stage ◽  
Content Type ◽  
Successful Vaccine ◽  
Blood Stage Infection ◽  
Induced Immunity

The development of a vaccine is essential for the elimination of malaria. However, despite many years of effort, a successful vaccine has not been achieved. Most subunit vaccine candidates tested in clinical trials have provided limited efficacy, and thus attenuated whole-parasite vaccines are now receiving close scrutiny. Here, we test chemically attenuatedPlasmodium yoelii17X and demonstrate significant protection following homologous and heterologous blood-stage challenge. Protection against blood-stage infection persisted for at least 9 months. Activation of both CD4+and CD8+T cells was shown after vaccination; however,in vivostudies demonstrated a pivotal role for both CD4+T cells and B cells since the absence of either cell type led to loss of vaccine-induced protection. In spite of significant activation of circulating CD8+T cells, liver-stage immunity was not evident. Neither did vaccine-induced CD8+T cells contribute to blood-stage protection; rather, these cells contributed to pathogenesis, since all vaccinated mice depleted of both CD4+and CD8+T cells survived a challenge infection. This study provides critical insight into whole-parasite vaccine-induced immunity and strong support for testing whole-parasite vaccines in humans.

scholarly journals Immunization of Mice with Live-Attenuated Late Liver Stage-Arresting Plasmodium yoelii Parasites Generates Protective Antibody Responses to Preerythrocytic Stages of Malaria

2014 ◽  
Vol 82 (12) ◽  
pp. 5143-5153 ◽  
Author(s):  
Gladys J. Keitany ◽  
Brandon Sack ◽  
Hannah Smithers ◽  
Lin Chen ◽  
Ihn K. Jang ◽  
...  
Keyword(s):  
T Cells ◽  
Malaria Infection ◽  
Plasmodium Yoelii ◽  
Effective Vaccine ◽  
Mouse Strains ◽  
Liver Stage ◽  
Content Type ◽  
Mosquito Bite ◽  
Experimental Immunization

ABSTRACTUnderstanding protective immunity to malaria is essential for the design of an effective vaccine to prevent the large number of infections and deaths caused by this parasitic disease. To date, whole-parasite immunization with attenuated parasites is the most effective method to confer sterile protection against malaria infection in clinical trials. Mouse model studies have highlighted the essential role that CD8+T cells play in protection against preerythrocytic stages of malaria; however, there is mounting evidence that antibodies are also important in these stages. Here, we show that experimental immunization of mice withPlasmodium yoeliifabb/f−(Pyfabb/f−), a genetically attenuated rodent malaria parasite that arrests late in the liver stage, induced functional antibodies that inhibited hepatocyte invasionin vitroand reduced liver-stage burdenin vivo. These antibodies were sufficient to induce sterile protection from challenge byP. yoeliisporozoites in the absence of T cells in 50% of mice when sporozoites were administered by mosquito bite but not when they were administered by intravenous injection. Moreover, among mice challenged by mosquito bite, a higher proportion of BALB/c mice than C57BL/6 mice developed sterile protection (62.5% and 37.5%, respectively). Analysis of the antibody isotypes induced by immunization withPyfabb/f−showed that, overall, BALB/c mice developed an IgG1-biased response, whereas C57BL/6 mice developed an IgG2b/c-biased response. Our data demonstrate for the first time that antibodies induced by experimental immunization of mice with a genetically attenuated rodent parasite play a protective role during the preerythrocytic stages of malaria. Furthermore, they highlight the importance of considering both the route of challenge and the genetic background of the mouse strains used when interpreting vaccine efficacy studies in animal models of malaria infection.

scholarly journals Characterization of a Lipopolysaccharide-Targeted Monoclonal Antibody and Its Variable Fragments as Candidates for Prophylaxis against the Obligate Intracellular Bacterial Pathogen Coxiella burnetii

2014 ◽  
Vol 82 (11) ◽  
pp. 4530-4541 ◽  
Author(s):  
Ying Peng ◽  
Laura Schoenlaub ◽  
Alexandra Elliott ◽  
William J. Mitchell ◽  
Guoquan Zhang
Keyword(s):  
Monoclonal Antibody ◽  
Coxiella Burnetii ◽  
Natural Infection ◽  
Bacterial Pathogen ◽  
Passive Transfer ◽  
Single Chain Variable Fragment ◽  
Single Chain ◽  
Fab Fragment ◽  
Content Type ◽  
Aerosol Infection

ABSTRACTOur previous study demonstrated that treatment ofCoxiella burnetiiwith the phase I lipopolysaccharide (PI-LPS)-targeted monoclonal antibody (MAb) 1E4 significantly inhibitedC. burnetiiinfection in mice, suggesting that 1E4 is a protective MAb. To determine whether passive transfer of antibodies (Abs) can provide protection againstC. burnetiinatural infection, we examined if passive transfer of 1E4 would protect SCID mice againstC. burnetiiaerosol infection. The results indicated that 1E4 conferred significant protection against aerosolizedC. burnetii, suggesting that 1E4 may be useful for preventingC. burnetiinatural infection. To further understand the mechanisms of 1E4-mediated protection and to test the possibility of using humanized 1E4 to preventC. burnetiiinfection, we examined whether the Fab fragment of 1E4 (Fab1E4), a recombinant murine single-chain variable fragment (muscFv1E4), and a humanized single-chain variable fragment (huscFv1E4) retained the ability of 1E4 to inhibitC. burnetiiinfection. The results indicated that Fab1E4, muscFv1E4, and huscFv1E4 were able to inhibitC. burnetiiinfection in mice but that their ability to inhibitC. burnetiiinfection was lower than that of 1E4. In addition, treatment ofC. burnetiiwith Fab1E4, muscFv1E4, or huscFv1E4 can blockC. burnetiiinfection of macrophages. Interestingly, treatment ofC. burnetiiwith huscFv1E4 can significantly reduceC. burnetiiinfectivity in human macrophages. This report provides the first evidence to demonstrate that the humanized variable fragments of an LPS-specific MAb can neutralizeC. burnetiiinfection and appears to be a promising step toward the potential use of a humanized MAb as emergency prophylaxis againstC. burnetiiexposure.

scholarly journals Role of sapA and yfgA in Susceptibility to Antibody-Mediated Complement-Dependent Killing and Virulence of Salmonella enterica Serovar Typhimurium

2017 ◽  
Vol 85 (9) ◽  
Author(s):  
Edna M. Ondari ◽  
Jennifer N. Heath ◽  
Elizabeth J. Klemm ◽  
Gemma Langridge ◽  
Lars Barquist ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Protein Translocation ◽  
Invasive Disease ◽  
Immune Serum ◽  
Insertion Mutant ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Serum Killing ◽  
Increased Sensitivity

ABSTRACT The ST313 pathovar of Salmonella enterica serovar Typhimurium contributes to a high burden of invasive disease among African infants and HIV-infected adults. It is characterized by genome degradation (loss of coding capacity) and has increased resistance to antibody-dependent complement-mediated killing compared with enterocolitis-causing strains of S. Typhimurium. Vaccination is an attractive disease-prevention strategy, and leading candidates focus on the induction of bactericidal antibodies. Antibody-resistant strains arising through further gene deletion could compromise such a strategy. Exposing a saturating transposon insertion mutant library of S. Typhimurium to immune serum identified a repertoire of S. Typhimurium genes that, when interrupted, result in increased resistance to serum killing. These genes included several involved in bacterial envelope biogenesis, protein translocation, and metabolism. We generated defined mutant derivatives using S. Typhimurium SL1344 as the host. Based on their initial levels of enhanced resistance to killing, yfgA and sapA mutants were selected for further characterization. The S. Typhimurium yfgA mutant lost the characteristic Salmonella rod-shaped appearance, exhibited increased sensitivity to osmotic and detergent stress, lacked very long lipopolysaccharide, was unable to invade enterocytes, and demonstrated decreased ability to infect mice. In contrast, the S. Typhimurium sapA mutants had similar sensitivity to osmotic and detergent stress and lipopolysaccharide profile and an increased ability to infect enterocytes compared with the wild type, but it had no increased ability to cause in vivo infection. These findings indicate that increased resistance to antibody-dependent complement-mediated killing secondary to genetic deletion is not necessarily accompanied by increased virulence and suggest the presence of different mechanisms of antibody resistance.

scholarly journals Computational Chemogenomics Drug Repositioning Strategy Enables the Discovery of Epirubicin as a New Repurposed Hit for Plasmodium falciparum and P. vivax

2020 ◽  
Vol 64 (9) ◽  
Author(s):  
Letícia Tiburcio Ferreira ◽  
Juliana Rodrigues ◽  
Gustavo Capatti Cassiano ◽  
Tatyana Almeida Tavella ◽  
Kaira Cristina Peralis Tomaz ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
In Silico ◽  
Antimalarial Activity ◽  
Drug Repositioning ◽  
Dna Gyrase ◽  
Plasmodium Yoelii ◽  
Computer Assisted ◽  
Content Type

ABSTRACT Widespread resistance against antimalarial drugs thwarts current efforts for controlling the disease and urges the discovery of new effective treatments. Drug repositioning is increasingly becoming an attractive strategy since it can reduce costs, risks, and time-to-market. Herein, we have used this strategy to identify novel antimalarial hits. We used a comparative in silico chemogenomics approach to select Plasmodium falciparum and Plasmodium vivax proteins as potential drug targets and analyzed them using a computer-assisted drug repositioning pipeline to identify approved drugs with potential antimalarial activity. Among the seven drugs identified as promising antimalarial candidates, the anthracycline epirubicin was selected for further experimental validation. Epirubicin was shown to be potent in vitro against sensitive and multidrug-resistant P. falciparum strains and P. vivax field isolates in the nanomolar range, as well as being effective against an in vivo murine model of Plasmodium yoelii. Transmission-blocking activity was observed for epirubicin in vitro and in vivo. Finally, using yeast-based haploinsufficiency chemical genomic profiling, we aimed to get insights into the mechanism of action of epirubicin. Beyond the target predicted in silico (a DNA gyrase in the apicoplast), functional assays suggested a GlcNac-1-P-transferase (GPT) enzyme as a potential target. Docking calculations predicted the binding mode of epirubicin with DNA gyrase and GPT proteins. Epirubicin is originally an antitumoral agent and presents associated toxicity. However, its antiplasmodial activity against not only P. falciparum but also P. vivax in different stages of the parasite life cycle supports the use of this drug as a scaffold for hit-to-lead optimization in malaria drug discovery.

scholarly journals In VitroAnalysis of the Interaction between Atovaquone and Proguanil against Liver Stage Malaria Parasites

2016 ◽  
Vol 60 (7) ◽  
pp. 4333-4335 ◽  
Author(s):  
Lídia Barata ◽  
Pascal Houzé ◽  
Khadija Boutbibe ◽  
Gigliola Zanghi ◽  
Jean-François Franetich ◽  
...  
Keyword(s):  
Plasmodium Yoelii ◽  
Human Hepatocytes ◽  
High Efficacy ◽  
Liver Stage ◽  
Content Type ◽  
Cytochrome P450 Activity ◽  
Main Target ◽  
P450 Activity ◽  
Pharmacological Basis

ABSTRACTThe interaction between atovaquone and proguanil has never been studied against liver stage malaria, which is the main target of this drug combination when used for chemoprevention. Using human hepatocytes lacking cytochrome P450 activity, and thus avoiding proguanil metabolizing into potent cycloguanil, we showin vitrothat the atovaquone-proguanil combination synergistically inhibits the growth of rodentPlasmodium yoeliiparasites. These results provide a pharmacological basis for the high efficacy of atovaquone-proguanil used as malaria chemoprevention.

scholarly journals Coxiella burnetii Interaction with Neutrophils and MacrophagesIn Vitroand in SCID Mice following Aerosol Infection

2013 ◽  
Vol 81 (12) ◽  
pp. 4604-4614 ◽  
Author(s):  
Alexandra Elliott ◽  
Ying Peng ◽  
Guoquan Zhang
Keyword(s):  
Immune Response ◽  
Coxiella Burnetii ◽  
Q Fever ◽  
Natural Infection ◽  
Scid Mice ◽  
Innate Immune ◽  
Content Type ◽  
Aerosol Infection

ABSTRACTCoxiella burnetiiis an obligate intracellular bacterium that causes acute and chronic Q fever in humans. Human Q fever is mainly transmitted by aerosol infection. However, there is a fundamental gap in the knowledge regarding the mechanisms of pulmonary immunity againstC. burnetiiinfection. This study focused on understanding the interaction betweenC. burnetiiand innate immune cellsin vitroandin vivo. Both virulentC. burnetiiNine Mile phase I (NMI) and avirulent Nine Mile phase II (NMII) were able to infect neutrophils, while the infection rates were lower than 29%, suggesting thatC. burnetiican infect neutrophils, but infection is limited. Interestingly,C. burnetiiinside neutrophils can infect and replicate within macrophages, suggesting that neutrophils cannot killC. burnetiiandC. burnetiimay be using infection of neutrophils as an evasive strategy to infect macrophages. To elucidate the mechanisms of the innate immune response toC. burnetiinatural infection, SCID mice were exposed to aerosolizedC. burnetii. Surprisingly, neutrophil influx into the lungs was delayed until day 7 postinfection in both NMI- and NMII-infected mice. This result suggests that neutrophils may play a unique role in the early immune response against aerosolizedC. burnetii. Studying the interaction betweenC. burnetiiand the innate immune system can provide a model system for understanding how the bacteria evade early immune responses to cause infection.

scholarly journals A Plasmodium yoelii Mei2-Like RNA Binding Protein Is Essential for Completion of Liver Stage Schizogony

2016 ◽  
Vol 84 (5) ◽  
pp. 1336-1345 ◽  
Author(s):  
Dorender A. Dankwa ◽  
Marshall J. Davis ◽  
Stefan H. I. Kappe ◽  
Ashley M. Vaughan
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Plasmodium Yoelii ◽  
Parasite Development ◽  
Mammalian Host ◽  
Mosquito Vector ◽  
Wild Type ◽  
Liver Stage ◽  
Content Type ◽  
Stage Development

Plasmodiumparasites employ posttranscriptional regulatory mechanisms as their life cycle transitions between host cell invasion and replication within both the mosquito vector and mammalian host. RNA binding proteins (RBPs) provide one mechanism for modulation of RNA function. To explore the role ofPlasmodiumRBPs during parasite replication, we searched for RBPs that might play a role during liver stage development, the parasite stage that exhibits the most extensive growth and replication. We identified a parasite ortholog of theMei2(Meiosisinhibited 2) RBP that is conserved amongPlasmodiumspecies (PlasMei2) and exclusively transcribed in liver stage parasites. Epitope-taggedPlasmodium yoeliiPlasMei2 was expressed only during liver stage schizogony and showed an apparent granular cytoplasmic location. Knockout ofPlasMei2(plasmei2−) inP. yoeliionly affected late liver stage development. TheP. yoeliiplasmei2−liver stage size increased progressively until late in development, similar to wild-type parasite development. However,P. yoeliiplasmei2−liver stage schizonts exhibited an abnormal DNA segregation phenotype and failed to form exoerythrocytic merozoites. Consequently the cellular integrity ofP. yoeliiplasmei2−liver stages became increasingly compromised late in development and the majority ofP. yoeliiplasmei2−underwent cell death by the time wild-type liver stages mature and release merozoites. This resulted in a complete block ofP. yoeliiplasmei2−transition from liver stage to blood stage infection in mice. Our results show for the first time the importance of aPlasmodiumRBP in the coordinated progression of late liver stage schizogony and maturation of new invasive forms.

scholarly journals Sontochin as a Guide to the Development of Drugs against Chloroquine-Resistant Malaria

2012 ◽  
Vol 56 (7) ◽  
pp. 3475-3480 ◽  
Author(s):  
Sovitj Pou ◽  
Rolf W. Winter ◽  
Aaron Nilsen ◽  
Jane Xu Kelly ◽  
Yuexin Li ◽  
...  
Keyword(s):  
Multidrug Resistant ◽  
Plasmodium Yoelii ◽  
Significant Activity ◽  
Drug Resistant ◽  
Content Type ◽  
Resistant Strains ◽  
Drug Resistant Strains ◽  
Derivatives Of

ABSTRACTSontochin was the original chloroquine replacement drug, arising from research by Hans Andersag 2 years after chloroquine (known as “resochin” at the time) had been shelved due to the mistaken perception that it was too toxic for human use. We were surprised to find that sontochin, i.e., 3-methyl-chloroquine, retains significant activity against chloroquine-resistant strains ofPlasmodium falciparum in vitro. We prepared derivatives of sontochin, “pharmachins,” with alkyl or aryl substituents at the 3 position and with alterations to the 4-position side chain to enhance activity against drug-resistant strains. Modified with an aryl substituent in the 3 position of the 7-chloro-quinoline ring, Pharmachin 203 (PH-203) exhibits low-nanomolar 50% inhibitory concentrations (IC50s) against drug-sensitive and multidrug-resistant strains andin vivoefficacy against patent infections ofPlasmodium yoeliiin mice that is superior to chloroquine. Our findings suggest that novel 3-position aryl pharmachin derivatives have the potential for use in treating drug resistant malaria.

scholarly journals Menoctone Resistance in Malaria Parasites Is Conferred by M133I Mutations in Cytochrome b That Are Transmissible through Mosquitoes

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
Lynn D. Blake ◽  
Myles E. Johnson ◽  
Sasha V. Siegel ◽  
Adonis McQueen ◽  
Iredia D. Iyamu ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Synthesis Method ◽  
Cross Resistance ◽  
Liver Stage ◽  
Content Type ◽  
Transmission Potential ◽  
The Past ◽  
Related Mortality

ABSTRACT Malaria-related mortality has slowly decreased over the past decade; however, eradication of malaria requires the development of new antimalarial chemotherapies that target liver stages of the parasite and combat the emergence of drug resistance. The diminishing arsenal of anti-liver-stage compounds sparked our interest in reviving the old and previously abandoned compound menoctone. In support of these studies, we developed a new convergent synthesis method that was facile, required fewer steps, produced better yields, and utilized less expensive reagents than the previously published method. Menoctone proved to be highly potent against liver stages of Plasmodium berghei (50 percent inhibitory concentration [IC50] = 0.41 nM) and erythrocytic stages of Plasmodium falciparum (113 nM). We selected for resistance to menoctone and found M133I mutations in cytochrome b of both P. falciparum and P. berghei. The same mutation has been observed previously in atovaquone resistance, and we confirmed cross-resistance between menoctone and atovaquone in vitro (for P. falciparum) and in vivo (for P. berghei). Finally, we assessed the transmission potential of menoctone-resistant P. berghei and found that the M133I mutant parasites were readily transmitted from mouse to mosquitoes and back to mice. In each step, the M133I mutation in cytochrome b, inducing menoctone resistance, was confirmed. In summary, this study is the first to show the mechanism of resistance to menoctone and that menoctone and atovaquone resistance is transmissible through mosquitoes.

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