scholarly journals Stable Artesunate Resistance in A Humanized Mouse Model of Plasmodium falciparum

2021 ◽  
Author(s):  
Sheetal Saini ◽  
Rajinder Kumar ◽  
Rajeev K. Tyagi
Keyword(s):  
Plasmodium Falciparum ◽  
Combination Therapy ◽  
Malaria Infection ◽  
Artemisinin Resistance ◽  
Antimalarial Drugs ◽  
Humanized Mouse ◽  
Humanized Mouse Model ◽  
Human Malaria

Plasmodium falciparum, the most devastating human malaria parasite, confers higher morbidity and mortality. Although efforts have been made to develop an effective malaria vaccine, stage- and species-specific short-lived immunity crippled these efforts. Hence, antimalarial drug treatment becomes a mainstay for the treatment of malaria infection in the wake of the unavailability of an effective vaccine. Further, there has been a wide array of antimalarial drugs effective against various developmental stages of P. falciparum due to their different structures, modes of action, and pharmacodynamics as well as pharmacokinetics. The development of resistance against almost all frontline drugs by P. falciparum indicates the need for combination therapy (artemisinin-based combination therapy; ACT) to treat patients with P. falciparum. A higher pool of parasitemia under discontinuous in vivo artemisinin drug pressure in a developed humanized mouse allows the selection of artesunate resistant (ART-R) P. falciparum. Intravenously administered artesunate, using either single flash doses or a 2-day regimen, to the P. falciparum-infected human blood chimeric NOD/SCID.IL-2Rγ−/− immunocompromised (NSG) mice, with progressive dose increments upon parasite recovery, was the strategy deployed to select resistant parasites. Parasite susceptibility to artemisinins and other antimalarial compounds was characterized in vitro and in vivo. P. falciparum has shown to evolve extreme artemisinin resistance as well as co-resistance to antimalarial drugs. Overall, the present information shall be very useful in devising newer therapeutic strategies to treat human malaria infection.

scholarly journals Preclinical characterization and target validation of the antimalarial pantothenamide MMV693183

2021 ◽  
Author(s):  
Laura E de Vries ◽  
Patrick AM Jansen ◽  
Catalina Barcelo ◽  
Justin Munro ◽  
Julie MJ Verhoef ◽  
...  
Keyword(s):  
Malaria Infection ◽  
Clinical Development ◽  
Target Validation ◽  
Humanized Mouse ◽  
Preclinical Development ◽  
Humanized Mouse Model ◽  
Pharmacodynamic Modelling ◽  
Biochemical Studies

Drug resistance and a dire lack of transmission-blocking antimalarials hamper malaria elimination. Here, we present the pantothenamide MMV693183 as a first-in-class acetyl-CoA synthetase (ACS) inhibitor to enter preclinical development. Our studies demonstrated attractive drug-like properties and in vivo efficacy in a humanized mouse model of Plasmodium falciparum infection. The compound showed exceptional in vitro activity against P. falciparum and P. vivax clinical isolates, and potently blocked P. falciparum transmission to Anopheles mosquitoes. Genetic and biochemical studies identified ACS as the target of the MMV693183-derived antimetabolite, CoA-MMV693183. MMV693183 was well adsorbed after oral administration in mice, rats and dogs. Pharmacokinetic-pharmacodynamic modelling predicted that a single 30 mg oral dose is sufficient to cure a malaria infection in humans. In conclusion, the ACS-targeting compound MMV693183 represents a promising addition to the portfolio of antimalarials in (pre)clinical development with a novel mode of action for the treatment of malaria and blocking transmission.

scholarly journals Evaluation of antimalarial prescription pattern and susceptibility of Plasmodium falciparum isolates in Kaduna, Nigeria

2020 ◽  
Vol 13 (7) ◽  
pp. 3398-3410
Author(s):  
O. Ifeoluwa Akanni ◽  
J.O. Ehinmidu ◽  
R.O. Bolaji
Keyword(s):  
Plasmodium Falciparum ◽  
Combination Therapy ◽  
Antimalarial Drug ◽  
Drug Prescription ◽  
Artemisinin Combination Therapy ◽  
Therapy Resistance ◽  
Antimalarial Drugs ◽  
In Vitro Susceptibility

Nigeria carries the highest burden of malaria in terms of morbidity and mortality. This is compounded by continuous resistance of Plasmodium falciparum to antimalarial drugs. This study was designed to evaluate the profile of malaria patients’ antimalarial drug prescription and in vitro susceptibility of P. falciparum isolates to commonly prescribed antimalarial drugs in Kaduna, Nigeria. Three years’ records of patients antimalarial drug prescriptions were collated (2013 to 2015) and the in vitro antimalarial agent susceptibility was determined for 28 clinical isolates using WHO Mark III microtest. Artemisinin-based combination therapy (ACT) was the most prescribed antimalarial for the period under review (92.3-93.7%). Among the ACTs, Artemether-lumefantrine was most prescribed. Of the 28 P. falciparum isolates evaluated, 3 (10.71%) were resistant to chloroquine with a median IC50 of 4.82μM (4.60-8.14μM), while five (17.86%) were resistant to mefloquine with a median IC50 of 25μM (10.3-41μM), 7(25.00%) to artemether with a median IC50 of 2.69μM (2.09-8.77μM), 9 (32.14%) to artesunate-mefloquine combination with a median IC50 of 9.0μM (7.98-35μM) and to artesunate, 11(39.29%) were resistant with a median IC50 of 2.4μM (1.56-5.65μM). This result shows a decline in resistance of P. falciparum to chloroquine compared to period prior to artemisinin-combination therapy as well as reduced susceptibility to artesunate and artemether. Further in vitro and in vivo monitoring will be required to inform antimalarial drug policy change.Keywords: Antimalarial, Artemisinin-combination therapy, resistance, susceptibility, microtest.

scholarly journals Mammalian deubiquitinating enzyme inhibitors display in vitro and in vivo activity against malaria parasites and potentiate artemisinin action

2020 ◽  
Author(s):  
Nelson V. Simwela ◽  
Katie R. Hughes ◽  
Michael T. Rennie ◽  
Michael P. Barrett ◽  
Andrew P. Waters
Keyword(s):  
Anticancer Agents ◽  
Drug Targets ◽  
Reverse Genetics ◽  
Enzyme Inhibitors ◽  
Artemisinin Resistance ◽  
Drug Repurposing ◽  
Antimalarial Drugs ◽  
Malaria Parasites

AbstractCurrent malaria control efforts rely significantly on artemisinin combinational therapies which have played massive roles in alleviating the global burden of the disease. Emergence of resistance to artemisinins is therefore, not just alarming but requires immediate intervention points such as development of new antimalarial drugs or improvement of the current drugs through adjuvant or combination therapies. Artemisinin resistance is primarily conferred by Kelch13 propeller mutations which are phenotypically characterised by generalised growth quiescence, altered haemoglobin trafficking and downstream enhanced activity of the parasite stress pathways through the ubiquitin proteasome system (UPS). Previous work on artemisinin resistance selection in a rodent model of malaria, which we and others have recently validated using reverse genetics, has also shown that mutations in deubiquitinating enzymes, DUBs (upstream UPS component) modulates susceptibility of malaria parasites to both artemisinin and chloroquine. The UPS or upstream protein trafficking pathways have, therefore, been proposed to be not just potential drug targets, but also possible intervention points to overcome artemisinin resistance. Here we report the activity of small molecule inhibitors targeting mammalian DUBs in malaria parasites. We show that generic DUB inhibitors can block intraerythrocytic development of malaria parasites in vitro and possess antiparasitic activity in vivo and can be used in combination with additive effect. We also show that inhibition of these upstream components of the UPS can potentiate the activity of artemisinin in vitro as well as in vivo to the extent that ART resistance can be overcome. Combinations of DUB inhibitors anticipated to target different DUB activities and downstream 20s proteasome inhibitors are even more effective at improving the potency of artemisinins than either inhibitors alone providing proof that targeting multiple UPS activities simultaneously could be an attractive approach to overcoming artemisinin resistance. These data further validate the parasite UPS as a target to both enhance artemisinin action and potentially overcome resistance. Lastly, we confirm that DUB inhibitors can be developed into in vivo antimalarial drugs with promise for activity against all of human malaria and could thus further exploit their current pursuit as anticancer agents in rapid drug repurposing programs.Graphical abstract

scholarly journals Human anti-CAIX antibodies mediate immune cell inhibition of renal cell carcinoma in vitro and in a humanized mouse model in vivo

2015 ◽  
Vol 14 (1) ◽  
Author(s):  
De-Kuan Chang ◽  
Raymond J. Moniz ◽  
Zhongyao Xu ◽  
Jiusong Sun ◽  
Sabina Signoretti ◽  
...  
Keyword(s):  
Renal Cell Carcinoma ◽  
Mouse Model ◽  
Cell Carcinoma ◽  
Renal Cell ◽  
Immune Cell ◽  
Humanized Mouse ◽  
Humanized Mouse Model ◽  
Cell Inhibition

scholarly journals Plasmodium falciparum K13 mutations in Africa and Asia present varying degrees of artemisinin resistance and an elevated fitness cost in African parasites

2021 ◽  
Author(s):  
Barbara H. Stokes ◽  
Kelly Rubiano ◽  
Satish K. Dhingra ◽  
Sachel Mok ◽  
Judith Straimer ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Southeast Asia ◽  
Survival Rates ◽  
Point Mutations ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Definitive Evidence ◽  
The Impact

AbstractThe emergence of artemisinin (ART) resistance in Plasmodium falciparum parasites has led to increasing rates of treatment failure with first-line ART-based combination therapies (ACTs) in Southeast Asia. In this region, select mutations in K13 can result in delayed parasite clearance rates in vivo and enhanced survival in the ring-stage survival assay (RSA) in vitro. Our genotyping of 3,299 P. falciparum isolates across 11 sub-Saharan countries reveals the continuing dominance of wild-type K13 and confirms the emergence of a K13 R561H variant in Rwanda. Using gene editing, we provide definitive evidence that this mutation, along with M579I and C580Y, can confer variable degrees of in vitro ART resistance in African P. falciparum strains. C580Y and M579I were both associated with substantial fitness costs in African parasites, which may counter-select against their dissemination in high-transmission settings. We also report the impact of multiple K13 mutations, including the predominant variant C580Y, on RSA survival rates and fitness in multiple Southeast Asian strains. No change in ART susceptibility was observed upon editing point mutations in ferrodoxin or mdr2, earlier associated with ART resistance in Southeast Asia. These data point to the lack of an evident biological barrier to mutant K13 mediating ART resistance in Africa, while identifying their detrimental impact on parasite growth.

scholarly journals Expansion of the Plasmodium falciparum Kelch 13 R622I mutation in Northwest Ethiopia

2021 ◽  
Author(s):  
Aberham A. Alemayehu ◽  
Daniel Castaneda-Mogollon ◽  
Habtie Tesfa ◽  
Sisay Getie ◽  
Abu Naser Mohon ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Artemisinin Resistance ◽  
Northwest Ethiopia ◽  
Efficacy Trial ◽  
North West ◽  
North West Ethiopia ◽  
Parasitological Response ◽  
Kelch 13

Abstract According to the WHO, almost two thirds of the Ethiopian population are at risk of contracting malaria, where infection with Plasmodium falciparum accounts for approximately 60% of cases today. The risk of artemisinin resistance spreading from SE Asia to Africa is a major concern. We conducted a 28-day in vivo efficacy trial of Artemether-Lumefantrine (Co-Artem) for treatment of uncomplicated malaria (n = 97) in the Gondar Region, North West Ethiopia in 2017–2018. Our results confirmed 100% adequate clinical and parasitological response (ACPR) with no parasites observed at day 3 by microscopy. Further analysis of day 0 samples showed the expansion of a kelch13 mutation R622I to 9.5% from 2.4% of isolates reported three years earlier. Closer examination of the R622I mutation in vitro is warranted.

scholarly journals Modification of an atypical clathrin-independent AP-2 adaptin complex of Plasmodium falciparum reduces susceptibility to artemisinin

2019 ◽  
Author(s):  
Ryan C. Henrici ◽  
Rachel L. Edwards ◽  
Martin Zoltner ◽  
Donelly A. van Schalkwyk ◽  
Melissa N. Hart ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Artemisinin Resistance ◽  
Conditional Knockout ◽  
Parental Line ◽  
Ring Stage ◽  
Intracellular Traffic ◽  
Reduced Ring ◽  
Kelch Domain

SummaryThe efficacy of current antimalarial drugs is threatened by reduced susceptibility of Plasmodium falciparum to artemisinin. In the Mekong region this is associated with mutations in the kelch propeller-encoding domain of pfkelch13, but variants of other parasite proteins are also thought to modulate the response to drug. Evidence from human and rodent studies suggests that the μ-subunit of the AP-2 adaptin trafficking complex is one such protein of interest. We generated transgenic Plasmodium falciparum parasites encoding the I592T variant of pfap2μ, orthologous to the I568T mutation associated with in vivo artemisinin resistance in P. chabaudi. When exposed to a four-hour pulse of dihydroartemisin in the ring-stage survival assay, two P. falciparum clones expressing AP-2μ I592T displayed significant and reproducible survival of 8.0% and 10.3%, respectively, compared to <2% for the 3D7 parental line (P = 0.0011 for each clone). In immunoprecipitation and localisation studies of HA-tagged AP-2μ, we identified interacting partners including AP-2α, AP-1/2β, AP-2σ and a kelch-domain protein encoded on chromosome 10 of P. falciparum, K10. Conditional knockout indicates that the AP-2 trafficking complex in P. falciparum is essential for the fidelity of merozoite biogenesis and membrane organisation in the mature schizont. We also show that while other heterotetrameric AP-complexes and secretory factors interact with clathrin, AP-2 complex subunits do not. Thus, the AP-2 complex may be diverted from a clathrin-dependent endocytic role seen in most eukaryotes into a Plasmodium-specific function. These findings represent striking divergences from eukaryotic dogma and support a role for intracellular traffic in determining artemisinin sensitivity in vitro, confirming the existence of multiple functional routes to reduced ring-stage artemisinin susceptibility. Therefore, the utility of pfkelch13 variants as resistance markers is unlikely to be universal, and phenotypic surveillance of parasite susceptibility in vivo may be needed to identify threats to our current combination therapies.

scholarly journals Controlled Human Malaria Infection in Semi-Immune Kenyan Adults (CHMI-SIKA): a study protocol to investigate in vivo Plasmodium falciparum malaria parasite growth in the context of pre-existing immunity

2018 ◽  
Vol 3 ◽  
pp. 155 ◽  
Author(s):  
Melissa C. Kapulu ◽  
Patricia Njuguna ◽  
Mainga M. Hamaluba ◽  
Keyword(s):  
Plasmodium Falciparum ◽  
Immune Responses ◽  
Malaria Infection ◽  
Malaria Vaccine ◽  
Parasite Growth ◽  
Host Immunity ◽  
Human Malaria ◽  
Controlled Human Malaria Infection ◽  
Adult Volunteers

Malaria remains a major public health burden despite approval for implementation of a partially effective pre-erythrocytic malaria vaccine. There is an urgent need to accelerate development of a more effective multi-stage vaccine. Adults in malaria endemic areas may have substantial immunity provided by responses to the blood stages of malaria parasites, but field trials conducted on several blood-stage vaccines have not shown high levels of efficacy.  We will use controlled human malaria infection (CHMI) studies with malaria-exposed volunteers to identify correlations between immune responses and parasite growth rates in vivo.  Immune responses more strongly associated with control of parasite growth should be prioritized to accelerate malaria vaccine development. We aim to recruit up to 200 healthy adult volunteers from areas of differing malaria transmission in Kenya, and after confirming their health status through clinical examination and routine haematology and biochemistry, we will comprehensively characterize immunity to malaria using >100 blood-stage antigens. We will administer 3,200 aseptic, purified, cryopreserved Plasmodium falciparum sporozoites (PfSPZ Challenge) by direct venous inoculation. Serial quantitative polymerase chain reaction to measure parasite growth rate in vivo will be undertaken. Clinical and laboratory monitoring will be undertaken to ensure volunteer safety. In addition, we will also explore the perceptions and experiences of volunteers and other stakeholders in participating in a malaria volunteer infection study. Serum, plasma, peripheral blood mononuclear cells and extracted DNA will be stored to allow a comprehensive assessment of adaptive and innate host immunity. We will use CHMI in semi-immune adult volunteers to relate parasite growth outcomes with antibody responses and other markers of host immunity. Registration: ClinicalTrials.gov identifier NCT02739763.

scholarly journals Evaluation of 4-Amino 2-Anilinoquinazolines against Plasmodium and Other Apicomplexan Parasites In Vitro and in a P. falciparum Humanized NOD-scid IL2Rγnull Mouse Model of Malaria

2018 ◽  
Vol 63 (3) ◽  
Author(s):  
Paul R. Gilson ◽  
William Nguyen ◽  
William A. Poole ◽  
Jose E. Teixeira ◽  
Jennifer K. Thompson ◽  
...  
Keyword(s):  
Mouse Model ◽  
Babesia Bovis ◽  
Parasite Line ◽  
Humanized Mouse ◽  
Humanized Mouse Model ◽  
Content Type ◽  
Apicomplexan Parasites ◽  
Micromolar Range

ABSTRACT A series of 4-amino 2-anilinoquinazolines optimized for activity against the most lethal malaria parasite of humans, Plasmodium falciparum, was evaluated for activity against other human Plasmodium parasites and related apicomplexans that infect humans and animals. Four of the most promising compounds from the 4-amino 2-anilinoquinazoline series were equally as effective against the asexual blood stages of the zoonotic P. knowlesi, suggesting that they could also be effective against the closely related P. vivax, another important human pathogen. The 2-anilinoquinazoline compounds were also potent against an array of P. falciparum parasites resistant to clinically available antimalarial compounds, although slightly less so than against the drug-sensitive 3D7 parasite line. The apicomplexan parasites Toxoplasma gondii, Babesia bovis, and Cryptosporidium parvum were less sensitive to the 2-anilinoquinazoline series with a 50% effective concentration generally in the low micromolar range, suggesting that the yet to be discovered target of these compounds is absent or highly divergent in non-Plasmodium parasites. The 2-anilinoquinazoline compounds act as rapidly as chloroquine in vitro and when tested in rodents displayed a half-life that contributed to the compound’s capacity to clear P. falciparum blood stages in a humanized mouse model. At a dose of 50 mg/kg of body weight, adverse effects to the humanized mice were noted, and evaluation against a panel of experimental high-risk off targets indicated some potential off-target activity. Further optimization of the 2-anilinoquinazoline antimalarial class will concentrate on improving in vivo efficacy and addressing adverse risk.

scholarly journals Blocking HIV-1 Infection by Chromosomal Integrative Expression of Human CD4 on the Surface of Lactobacillus acidophilus ATCC 4356

2019 ◽  
Vol 93 (8) ◽  
Author(s):  
Wenzhong Wei ◽  
Joshua Wiggins ◽  
Duoyi Hu ◽  
Vladimir Vrbanac ◽  
Dane Bowder ◽  
...  
Keyword(s):  
Mouse Model ◽  
Lactobacillus Acidophilus ◽  
Sexual Transmission ◽  
Effective Vaccine ◽  
Humanized Mouse ◽  
Humanized Mouse Model ◽  
Antiviral Proteins ◽  
Hiv 1

ABSTRACT Lactobacillus bacteria are potential delivery vehicles for biopharmaceutical molecules because they are well-recognized as safe microorganisms that naturally inhabit the human body. The goal of this study was to employ these lactobacilli to combat human immunodeficiency virus type 1 (HIV-1) infection and transmission. By using a chromosomal integration method, we engineered Lactobacillus acidophilus ATCC 4356 to display human CD4, the HIV-1 receptor, on the cell surface. Since human CD4 can bind to any infectious HIV-1 particles, the engineered lactobacilli can potentially capture HIV-1 of different subtypes and prevent infection. Our data demonstrate that the CD4-carrying bacteria are able to adsorb HIV-1 particles and reduce infection significantly in vitro and also block intrarectal HIV-1 infection in a humanized mouse model in preliminary tests in vivo. Our results support the potential of this approach to decrease the efficiency of HIV-1 sexual transmission. IMPORTANCE In the absence of an effective vaccine, alternative approaches to block HIV-1 infection and transmission with commensal bacteria expressing antiviral proteins are being considered. This report provides a proof-of-concept by using Lactobacillus bacteria stably expressing the HIV-1 receptor CD4 to capture and neutralize HIV-1 in vitro and in a humanized mouse model. The stable expression of antiviral proteins, such as CD4, following genomic integration of the corresponding genes into this Lactobacillus strain may contribute to the prevention of HIV-1 sexual transmission.

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