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PloS One 2023Antimalarial drugs that can block the transmission of Plasmodium gametocytes to mosquito vectors would be highly beneficial for malaria elimination efforts. Identifying...
Assessment of the transmission blocking activity of antimalarial compounds by membrane feeding assays using natural Plasmodium falciparum gametocyte isolates from West-Africa.
Antimalarial drugs that can block the transmission of Plasmodium gametocytes to mosquito vectors would be highly beneficial for malaria elimination efforts. Identifying transmission-blocking drugs currently relies on evaluation of their activity against gametocyte-producing laboratory parasite strains and would benefit from a testing pipeline with genetically diverse field isolates. The aims of this study were to develop a pipeline to test drugs against P. falciparum gametocyte field isolates and to evaluate the transmission-blocking activity of a set of novel compounds. Two assays were designed so they could identify both the overall transmission-blocking activity of a number of marketed and experimental drugs by direct membrane feeding assays (DMFA), and then also discriminate between those that are active against the gametocytes (gametocyte killing or sterilizing) or those that block development in the mosquito (sporontocidal). These DMFA assays used venous blood samples from naturally infected Plasmodium falciparum gametocyte carriers and locally reared Anopheles gambiae s.s. mosquitoes. Overall transmission-blocking activity was assessed following a 24 hour incubation of compound with gametocyte infected blood (TB-DMFA). Sporontocidal activity was evaluated following addition of compound directly prior to feeding, without incubation (SPORO-DMFA); Gametocyte viability was retained during 24-hour incubation at 37°C when gametocyte infected red blood cells were reconstituted in RPMI/serum. Methylene-blue, MMV693183, DDD107498, atovaquone and P218 showed potent transmission-blocking activity in the TB-DMFA, and both atovaquone and the novel antifolate P218 were potent inhibitors of sporogonic development in the SPORO-DMA. This work establishes a pipeline for the integral use of field isolates to assess the transmission-blocking capacity of antimalarial drugs to block transmission that should be validated in future studies.
Topics: Animals; Humans; Plasmodium falciparum; Antimalarials; Atovaquone; Folic Acid Antagonists; Malaria, Falciparum; Africa, Western
PubMed: 37494413
DOI: 10.1371/journal.pone.0284751 -
Infectious Diseases of Poverty Jul 2023Human babesiosis is a worldwide disease caused by intraerythrocytic protozoa of the genus Babesia. It is transmitted by bites from ixodid ticks, and mechanically...
Successful treatment with doxycycline monotherapy for human infection with Babesia venatorum (Babesiidae, Sporozoa) in China: a case report and proposal for a clinical regimen.
BACKGROUND
Human babesiosis is a worldwide disease caused by intraerythrocytic protozoa of the genus Babesia. It is transmitted by bites from ixodid ticks, and mechanically transmitted by blood transfusion. It is primarily treated with quinine and/or atovaquone, which are not readily available in China. In this study, we developed a novel treatment regimen involving doxycycline monotherapy in a patient with severe Babesia venatorum infection as an alternative therapeutic medication. The aim of our study is to provide a guidance for clinical practice treatment of human babesiosis.
CASE PRESENTATION
A 73-year-old man who had undergone splenectomy and blood transfusion 8 years prior, presented with an unexplained fever, headache, and thrombocytopenia, and was admitted to the Fifth Medical Center of the PLA General Hospital. He was diagnosed with B. venatorum infection by morphological review of thin peripheral blood smears, which was confirmed by multi-gene polymerase chain reaction (PCR), and sequencing of the entire 18s rRNA and partial β-tubulin encoding genes, as well as isolation by animal inoculation. The doxycycline monotherapy regimen (peros, 0.1 g bisindie) was administered following pharmacological guidance and an effective outcome was observed. The patient recovered rapidly following the doxycycline monotherapy. The protozoan load in peripheral blood samples decreased by 88% in hematocrit counts after 8 days, and negative PCR results were obtained after 90 days of follow-up at the hospital. The treatment lasted for 3 months without any side effects or sequelae. The nine-month follow-up survey of the patient did not reveal any signs of recrudescence or anti-babesial tolerance.
CONCLUSIONS
We have reported a clinical case of successful doxycycline monotherapy for human babesiosis caused by B. venatorum, which provides an optional medical intervention for human babesiosis.
Topics: Male; Animals; Humans; Aged; Babesia; Babesiosis; Doxycycline; Ixodidae; China
PubMed: 37443058
DOI: 10.1186/s40249-023-01111-1 -
Heliyon Jun 2023Babesiosis is a protozoal disease affect livestock and pet animals such as cattle, buffaloes, sheep, goats, horses, donkeys, mules, dogs, and cats. It causes severe... (Review)
Review
Babesiosis is a protozoal disease affect livestock and pet animals such as cattle, buffaloes, sheep, goats, horses, donkeys, mules, dogs, and cats. It causes severe economic losses in livestock as well as in pet animals. A large number of dairy animals are imported in order to fulfill the demands of milk, milk, meat and its products. In addition, different pet animals are transported from Pakistan to various parts of the world, therefore, it is important to identify the current status and distribution of babesiosis throughout Pakistan in order to control the disease and draw attention for future research, diagnosis, treatment and control of this diseases. No work has been done on a complete review on up-to-date on blood protozoal disease burden in Pakistan. This article will provide about the complete background of babesiosis in ruminants, equines and pet animals, its current status, distribution, vectors in Pakistan and allopathic and ethnoveterinary treatments used against babesiosis. Babesiosis may be subclinical (apparently normal) and may be clinical with acute to chronic disease and sometimes fatal. Babesia is found and develops inside the erythrocytes (red blood cells). Clinically, it causes fever, fatigue, lethargy, pallor mucus membranes, malaise, cachexia, respiratory distress, jaundice, icterus, hemolytic anemia, hemoglobinuria, lymphadenopathy, chollangocytitis, hepatomegaly, and splenomegaly. Chemotherapy for babesiosis includes Imidocarb dipropionate, Diaminazine aceturate Atovaquone and Bupravaquone, Azithromycin, Quinuronium sulfate and Amicarbalidesio-thionate are most widely used. Supportive therapy includes multivitamins, fluid therapy, antipyretics intravenous fluids, and blood transfusions are used if necessary. In addition, there are certain ethnoveterinary (homeopathic) ingredients which having anti-babesial activity. As the resistance against these drugs is developing every day. New more specific long-lasting drugs should be developed for the treatment of Babesiosis. Further studies should be done on disease genome of different species of for vaccine development like malarial parasites.
PubMed: 37441378
DOI: 10.1016/j.heliyon.2023.e17172 -
International Journal of Nanomedicine 2023Reversing the hypoxic and immunosuppressive tumor microenvironment (TME) is crucial for treating malignant melanoma. Seeking a robust platform for the effective...
RATIONALE
Reversing the hypoxic and immunosuppressive tumor microenvironment (TME) is crucial for treating malignant melanoma. Seeking a robust platform for the effective reversion of hypoxic and immunosuppressive TME may be an excellent solution to revolutionizing the current landscape of malignant melanoma treatment. Here, we demonstrated a transdermal and intravenous dual-administration paradigm. A tailor-made Ato/cabo@PEG-TK-PLGA NPs were administrated transdermally to melanoma with the help of a gel spray containing a skin-penetrating material borneol. Nanoparticles encased Ato and cabo were released and thereby reversed the hypoxic and immunosuppressive tumor microenvironment (TME).
METHODS
Ato/cabo@PEG-TK-PLGA NPs were synthesized through a self-assembly emulsion process, and the transdermal ability was assessed using Franz diffusion cell assembly. The inhibition effect on cell respiration was measured by OCR, ATP, and pO detection and in vivo photoacoustic (PA) imaging. The reversing of the immunosuppressive was detected through flow cytometry analysis of MDSCs and T cells. At last, the in vivo anti-tumor efficacy and histopathology, immunohistochemical analysis and safety detection were performed using tumor-bearing mice.
RESULTS
The transdermally administrated Ato/cabo@PEG-TK-PLGA NPs successfully spread to the skin surface of melanoma and then entered deep inside the tumor with the help of a gel spray and a skin puncturing material borneol. Atovaquone (Ato, a mitochondrial-respiration inhibitor) and cabozantinib (cabo, a MDSCs eliminator) were concurrently released in response to the intratumorally overexpressed HO. The released Ato and cabo respectively reversed the hypoxic and immunosuppressive TME. The reversed hypoxic TME offered sufficient O for the intravenously administrated indocyanine green (ICG, an FDA-approved photosensitizer) to produce adequate amount of ROS. In contrast, the reversed immunosuppressive TME conferred amplified systemic immune responses.
CONCLUSION
Taken together, we developed a transdermal and intravenous dual-administration paradigm, which effectively reversed the hypoxic and immunosuppressive tumor microenvironment in the treatment of the malignant melanoma. We believe our study will open a new path for the effective elimination of the primary tumors and the real-time control of tumor metastasis.
Topics: Animals; Mice; Hydrogen Peroxide; Tumor Microenvironment; Melanoma; Immunosuppressive Agents; Melanoma, Cutaneous Malignant
PubMed: 37435153
DOI: 10.2147/IJN.S414882 -
Antibiotics (Basel, Switzerland) Jun 2023This study aimed to demonstrate that severe neurological motor deficits in the context of late tick-borne disease with mixed microorganism involvement are eligible for...
Complete Remission in Paralytic Late Tick-Borne Neurological Disease Comprising Mixed Involvement of , and : Use of Long-Term Treatments with Antibiotics and Antiparasitics in a Series of 10 Cases.
This study aimed to demonstrate that severe neurological motor deficits in the context of late tick-borne disease with mixed microorganism involvement are eligible for long-term combined antibiotic/antiparasitic treatments. The inclusion criteria were: 1. neurological limb paralysis with a disability score >4 according to the EDSS Kurtzke disability scale; 2. serological tests pointing to an involvement of the main tick-borne microorganisms s.l., , , and ; 3. a general disease for more than 6 months with fatigue, pain and subjective cognitive deficit. The patients were administered long-term treatments with repeated cycles (at least three) of 35-day IV ceftriaxone and repeated oral regimens of azithromycin-doxycycline and azithromycin-doxycycline-rifampicin. For , repeated courses of atovaquone-azithromycin were administered. Ten patients had intractable or severe motor deficits before treatment in the context of (two cases) (four cases), (two cases), (one case) and (one case). For several months, five had been in wheelchairs, and four had been walking with sticks. Seven patients out of 10 (70%) showed complete remission after a mean active treatment duration of 20.1 + 6.6 months, with a mean number of 4 ceftriaxone cycles. Three patients showed an initial remission but suffered secondary antibiotic/antiparasitic-resistant motor recurrences. Among the nine patients with serologic positivity, treatments obtained complete remission in seven cases (77%). The findings of this ten-case series suggest the usefulness of long-term antibiotic/antiparasitic treatments in patients with severe late tick-borne neurological deficits with highly significant elements of tick-borne involvement.
PubMed: 37370340
DOI: 10.3390/antibiotics12061021 -
International Journal of Antimicrobial... Sep 2023In the absence of a highly efficacious vaccine, chemotherapy remains the cornerstone to control malaria morbidity and mortality. The threat of the emergence of parasites...
In the absence of a highly efficacious vaccine, chemotherapy remains the cornerstone to control malaria morbidity and mortality. The threat of the emergence of parasites resistant to artemisinin-based combination therapies highlights the need for new antimalarial drugs ideally with superior properties. The killing rate reflects the speed of action of antimalarial drugs, which can be measured in vitro through the parasite reduction ratio (PRR) assay to shortlist interesting candidates. As a standard, the in vitro PRR assay is performed by measuring [H]hypoxanthine incorporation of Plasmodium falciparum. This methodology is restricted to specialised laboratories owing to the handling of radioactive material. In this work, we describe a sandwich enzyme-linked immunosorbent assay to detect P. falciparum histidine-rich protein 2 (HRP-2) as an alternative methodology to assess the PRR. We first validated the methodology with established antimalarial drugs (artesunate, chloroquine, pyrimethamine and atovaquone) by comparing our results with previous results of the [H]hypoxanthine incorporation readout provided by an expert laboratory, and subsequently assessed the speed of action of four new antimalarial candidates (compound 22, chlorotonil A, boromycin and ivermectin). The HRP-2 PRR assay achieved comparable results to the [H]hypoxanthine incorporation readout in terms of parasite growth rate over time, lag phase and parasite clearance time. In addition, parasite growth following drug exposure was quantified after 7, 14, 21 and 28 days of recovery time. In conclusion, the PRR assay based on HRP-2 is similar to [H]hypoxanthine in determining a drug's parasite killing rate and can be widely used in all research laboratories.
Topics: Animals; Antimalarials; Parasites; Plasmodium falciparum; Hypoxanthine; Chloroquine; Malaria, Falciparum
PubMed: 37348620
DOI: 10.1016/j.ijantimicag.2023.106894 -
Antimicrobial Agents and Chemotherapy Jul 2023Ivermectin is an endectocide used widely to treat a variety of internal and external parasites. Field trials of ivermectin mass drug administration for malaria...
Ivermectin is an endectocide used widely to treat a variety of internal and external parasites. Field trials of ivermectin mass drug administration for malaria transmission control have demonstrated a reduction of mosquito survival and human malaria incidence. Ivermectin will mostly be deployed together with artemisinin-based combination therapies (ACT), the first-line treatment of falciparum malaria. It has not been well established if ivermectin has activity against asexual stage Plasmodium falciparum or if it interacts with the parasiticidal activity of other antimalarial drugs. This study evaluated antimalarial activity of ivermectin and its metabolites in artemisinin-sensitive and artemisinin-resistant P. falciparum isolates and assessed drug-drug interaction with artemisinins and its partner drugs. The concentration of ivermectin causing half of the maximum inhibitory activity (IC) on parasite survival was 0.81 μM with no significant difference between artemisinin-sensitive and artemisinin-resistant isolates ( = 0.574). The ivermectin metabolites were 2-fold to 4-fold less active than the ivermectin parent compound ( < 0.001). Potential pharmacodynamic drug-drug interactions of ivermectin with artemisinins, ACT-partner drugs, and atovaquone were studied using mixture assays providing isobolograms and derived fractional inhibitory concentrations. There were no synergistic or antagonistic pharmacodynamic interactions when combining ivermectin and antimalarial drugs. In conclusion, ivermectin does not have clinically relevant activity against the asexual blood stages of P. falciparum. It also does not affect the antimalarial activity of artemisinins or ACT-partner drugs against asexual blood stages of P. falciparum.
Topics: Animals; Humans; Antimalarials; Plasmodium falciparum; Ivermectin; Artemisinins; Malaria, Falciparum; Malaria; Drug Combinations; Drug Resistance
PubMed: 37338381
DOI: 10.1128/aac.01730-22 -
BMC Infectious Diseases Jun 2023One of the key obstacles to malaria elimination is largely attributed to Plasmodium vivax's ability to form resilient hypnozoites in the host liver that cause relapsing...
One of the key obstacles to malaria elimination is largely attributed to Plasmodium vivax's ability to form resilient hypnozoites in the host liver that cause relapsing infections. As a result, interruption of P. vivax transmission is difficult. P. vivax transmission occurs in Duffy-positive individuals and have been mainly thought to be absent in Africa. However, increasing studies using molecular tools detected P. vivax among Duffy-negative individuals in various African countries. Studies on the African P. vivax has been severely limited because most of malaria control program focus mainly on falciparum malaria. In addition, there is a scarcity of laboratory infrastructures to overcome the biological obstacles posed by P. vivax. Herein, we established field transmission of Ethiopian P. vivax for routine sporozoite supply followed by liver stage infection in Mali. Furthermore, we evaluated local P. vivax hypnozoites and schizonts susceptibilities to reference antimalarial drugs. The study enabled the assessment of local African P. vivax hypnozoite production dynamics. Our data displayed the ability of the African P. vivax to produce hypnozoite forms ex-vivo at different rates per field isolate. We report that while tafenoquine (1µM) potently inhibited both hypnozoites and schizont forms; atovaquone (0.25µM) and the phosphatidylinositol-4-OH kinase (PI4K)-specific inhibitor KDU691 (0.5µM) showed no activity against hypnozoites forms. Unlike hypnozoites forms, P. vivax schizont stages were fully susceptible to both atovaquone (0.25µM) and the (PI4K)-specific inhibitor KDU691 (0.5µM). Together, the data revealed the importance of the local platform for further biological investigation and implementation of drug discovery program on the African P. vivax clinical isolates.
Topics: Humans; Antimalarials; Plasmodium vivax; Atovaquone; Malaria, Vivax; Mali
PubMed: 37312065
DOI: 10.1186/s12879-023-08381-y -
Open Forum Infectious Diseases May 2023Sensitive molecular assays, such as quantitative reverse-transcription polymerase chain reaction (qRT-PCR) of 18S ribosomal RNA (rRNA), are increasingly the primary...
BACKGROUND
Sensitive molecular assays, such as quantitative reverse-transcription polymerase chain reaction (qRT-PCR) of 18S ribosomal RNA (rRNA), are increasingly the primary method of detecting infections in controlled human malaria infection (CHMI) trials. However, thick blood smears (TBSs) remain the main method for confirming clearance of parasites after curative treatment, in part owing to uncertainty regarding biomarker clearance rates.
METHODS
For this analysis, 18S rRNA qRT-PCR data were compiled from 127 -infected participants treated with chloroquine or atovaquone-proguanil in 6 CHMI studies conducted in Seattle, Washington, over the past decade. A survival analysis approach was used to compare biomarker and TBS clearance times among studies. The effect of the parasite density at which treatment was initiated on clearance time was estimated using linear regression.
RESULTS
The median time to biomarker clearance was 3 days (interquartile range, 3-5 days), while the median time to TBS clearance was 1 day (1-2 days). Time to biomarker clearance increased with the parasite density at which treatment was initiated. Parasite density did not have a significant effect on TBS clearance.
CONCLUSIONS
The 18S rRNA biomarker clears quickly and can be relied on to confirm the adequacy of Food and Drug Administration-approved treatments in CHMI studies at nonendemic sites.
PubMed: 37265668
DOI: 10.1093/ofid/ofad202 -
The Journal of Biological Chemistry Jul 2023Among the various components of the protozoan Plasmodium mitochondrial respiratory chain, only Complex III is a validated cellular target for antimalarial drugs. The...
Among the various components of the protozoan Plasmodium mitochondrial respiratory chain, only Complex III is a validated cellular target for antimalarial drugs. The compound CK-2-68 was developed to specifically target the alternate NADH dehydrogenase of the malaria parasite respiratory chain, but the true target for its antimalarial activity has been controversial. Here, we report the cryo-EM structure of mammalian mitochondrial Complex III bound with CK-2-68 and examine the structure-function relationships of the inhibitor's selective action on Plasmodium. We show that CK-2-68 binds specifically to the quinol oxidation site of Complex III, arresting the motion of the iron-sulfur protein subunit, which suggests an inhibition mechanism similar to that of P-type Complex III inhibitors such as atovaquone, stigmatellin, and UHDBT. Our results shed light on the mechanisms of observed resistance conferred by mutations, elucidate the molecular basis of the wide therapeutic window of CK-2-68 for selective action of Plasmodium vs. host cytochrome bc, and provide guidance for future development of antimalarials targeting Complex III.
Topics: Animals; Antimalarials; Electron Transport Complex III; Plasmodium falciparum; Plasmodium; Cytochromes; Mammals
PubMed: 37236355
DOI: 10.1016/j.jbc.2023.104860