Rapidly Increasing Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence and Limited Clinical Disease in 3 Malian Communities: A Prospective Cohort Study.

BACKGROUND: The extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure and transmission in Mali and the surrounding region is not well understood. We aimed to estimate the cumulative incidence of SARS-CoV-2 in 3 communities and understand factors associated with infection. METHODS: Between July 2020 and January 2021, we collected blood samples and demographic, social, medical, and self-reported symptoms information from residents aged 6 months and older over 2 study visits. SARS-CoV-2 antibodies were measured using a highly specific 2-antigen enzyme-linked immunosorbent assay optimized for use in Mali. We calculated cumulative adjusted seroprevalence for each community and evaluated factors associated with serostatus at each visit by univariate and multivariate analysis. RESULTS: Overall, 94.8% (2533/2672) of participants completed both study visits. A total of 31.3% (837/2672) were aged <10 years, 27.6% (737/2672) were aged 10-17 years, and 41.1% (1098/2572) were aged ≥18 years. The cumulative SARS-CoV-2 exposure rate was 58.5% (95% confidence interval, 47.5-69.4). This varied between sites and was 73.4% in the urban community of Sotuba, 53.2% in the rural town of Bancoumana, and 37.1% in the rural village of Donéguébougou. Study site and increased age were associated with serostatus at both study visits. There was minimal difference in reported symptoms based on serostatus. CONCLUSIONS: The true extent of SARS-CoV-2 exposure in Mali is greater than previously reported and may now approach hypothetical "herd immunity" in urban areas. The epidemiology of the pandemic in the region may be primarily subclinical and within background illness rates.

Severe Acute Respiratory Syndrome Coronavirus 2 Seroassay Performance and Optimization in a Population With High Background Reactivity in Mali.

BACKGROUND: False positivity may hinder the utility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological tests in sub-Saharan Africa. METHODS: From 312 Malian samples collected before 2020, we measured antibodies to the commonly tested SARS-CoV-2 antigens and 4 other betacoronaviruses by enzyme-linked immunosorbent assay (ELISA). In a subset of samples, we assessed antibodies to a panel of Plasmodium falciparum antigens by suspension bead array and functional antiviral activity by SARS-CoV-2 pseudovirus neutralization assay. We then evaluated the performance of an ELISA using SARS-CoV-2 spike protein and receptor-binding domain developed in the United States using Malian positive and negative control samples. To optimize test performance, we compared single- and 2-antigen approaches using existing assay cutoffs and population-specific cutoffs. RESULTS: Background reactivity to SARS-CoV-2 antigens was common in prepandemic Malian samples. The SARS-CoV-2 reactivity varied between communities, increased with age, and correlated negligibly/weakly with other betacoronavirus and P falciparum antibodies. No prepandemic samples demonstrated functional activity. Regardless of the cutoffs applied, test specificity improved using a 2-antigen approach. Test performance was optimal using a 2-antigen assay with population-specific cutoffs (sensitivity, 73.9% [95% confidence interval {CI}, 51.6-89.8]; specificity, 99.4% [95% CI, 97.7-99.9]). CONCLUSIONS: We have addressed the problem of SARS-CoV-2 seroassay performance in Africa by using a 2-antigen assay with cutoffs defined by performance in the target population.

Positron emission tomography and magnetic resonance imaging in experimental human malaria to identify organ-specific changes in morphology and glucose metabolism: A prospective cohort study.

BACKGROUND: Plasmodium vivax has been proposed to infect and replicate in the human spleen and bone marrow. Compared to Plasmodium falciparum, which is known to undergo microvascular tissue sequestration, little is known about the behavior of P. vivax outside of the circulating compartment. This may be due in part to difficulties in studying parasite location and activity in life. METHODS AND FINDINGS: To identify organ-specific changes during the early stages of P. vivax infection, we performed 18-F fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) at baseline and just prior to onset of clinical illness in P. vivax experimentally induced blood-stage malaria (IBSM) and compared findings to P. falciparum IBSM. Seven healthy, malaria-naive participants were enrolled from 3 IBSM trials: NCT02867059, ACTRN12616000174482, and ACTRN12619001085167. Imaging took place between 2016 and 2019 at the Herston Imaging Research Facility, Australia. Postinoculation imaging was performed after a median of 9 days in both species (n = 3 P. vivax; n = 4 P. falciparum). All participants were aged between 19 and 23 years, and 6/7 were male. Splenic volume (P. vivax: +28.8% [confidence interval (CI) +10.3% to +57.3%], P. falciparum: +22.9 [CI -15.3% to +61.1%]) and radiotracer uptake (P. vivax: +15.5% [CI -0.7% to +31.7%], P. falciparum: +5.5% [CI +1.4% to +9.6%]) increased following infection with each species, but more so in P. vivax infection (volume: p = 0.72, radiotracer uptake: p = 0.036). There was no change in FDG uptake in the bone marrow (P. vivax: +4.6% [CI -15.9% to +25.0%], P. falciparum: +3.2% [CI -3.2% to +9.6%]) or liver (P. vivax: +6.2% [CI -8.7% to +21.1%], P. falciparum: -1.4% [CI -4.6% to +1.8%]) following infection with either species. In participants with P. vivax, hemoglobin, hematocrit, and platelet count decreased from baseline at the time of postinoculation imaging. Decrements in hemoglobin and hematocrit were significantly greater in participants with P. vivax infection compared to P. falciparum. The main limitations of this study are the small sample size and the inability of this tracer to differentiate between host and parasite metabolic activity. CONCLUSIONS: PET/MRI indicated greater splenic tropism and metabolic activity in early P. vivax infection compared to P. falciparum, supporting the hypothesis of splenic accumulation of P. vivax very early in infection. The absence of uptake in the bone marrow and liver suggests that, at least in early infection, these tissues do not harbor a large parasite biomass or do not provoke a prominent metabolic response. PET/MRI is a safe and noninvasive method to evaluate infection-associated organ changes in morphology and glucose metabolism.

Haematological response in experimental human Plasmodium falciparum and Plasmodium vivax malaria.

BACKGROUND: Malaria-associated anaemia, arising from symptomatic, asymptomatic and submicroscopic infections, is a significant cause of morbidity worldwide. Induced blood stage malaria volunteer infection studies (IBSM-VIS) provide a unique opportunity to evaluate the haematological response to early Plasmodium falciparum and Plasmodium vivax infection. METHODS: This study was an analysis of the haemoglobin, red cell counts, and parasitaemia data from 315 participants enrolled in IBSM-VIS between 2012 and 2019, including 269 participants inoculated with the 3D7 strain of P. falciparum (Pf3D7), 15 with an artemisinin-resistant P. falciparum strain (PfK13) and 46 with P. vivax. Factors associated with the fractional fall in haemoglobin (Hb-FF) were evaluated, and the malaria-attributable erythrocyte loss after accounting for phlebotomy-related losses was estimated. The relative contribution of parasitized erythrocytes to the malaria-attributable erythrocyte loss was also estimated. RESULTS: The median peak parasitaemia prior to treatment was 10,277 parasites/ml (IQR 3566-27,815), 71,427 parasites/ml [IQR 33,236-180,213], and 34,840 parasites/ml (IQR 13,302-77,064) in participants inoculated with Pf3D7, PfK13, and P. vivax, respectively. The median Hb-FF was 10.3% (IQR 7.8-13.3), 14.8% (IQR 11.8-15.9) and 11.7% (IQR 8.9-14.5) in those inoculated with Pf3D7, PfK13 and P. vivax, respectively, with the haemoglobin nadir occurring a median 12 (IQR 5-21), 15 (IQR 7-22), and 8 (IQR 7-15) days following inoculation. In participants inoculated with P. falciparum, recrudescence was associated with a greater Hb-FF, while in those with P. vivax, the Hb-FF was associated with a higher pre-treatment parasitaemia and later day of anti-malarial treatment. After accounting for phlebotomy-related blood losses, the estimated Hb-FF was 4.1% (IQR 3.1-5.3), 7.2% (IQR 5.8-7.8), and 4.9% (IQR 3.7-6.1) in participants inoculated with Pf3D7, PfK13, and P. vivax, respectively. Parasitized erythrocytes were estimated to account for 0.015% (IQR 0.006-0.06), 0.128% (IQR 0.068-0.616) and 0.022% (IQR 0.008-0.082) of the malaria-attributable erythrocyte loss in participants inoculated with Pf3D7, PfK13, and P. vivax, respectively. CONCLUSION: Early experimental P. falciparum and P. vivax infection resulted in a small but significant fall in haemoglobin despite parasitaemia only just at the level of microscopic detection. Loss of parasitized erythrocytes accounted for < 0.2% of the total malaria-attributable haemoglobin loss.

An Experimental Human Blood-Stage Model for Studying Plasmodium malariae Infection.

BACKGROUND: Plasmodium malariae is considered a minor malaria parasite, although its global disease burden is underappreciated. The aim of this study was to develop an induced blood-stage malaria (IBSM) model of P. malariae to study parasite biology, diagnostic assays, and treatment. METHODS: This clinical trial involved 2 healthy subjects who were intravenously inoculated with cryopreserved P. malariae-infected erythrocytes. Subjects were treated with artemether-lumefantrine after development of clinical symptoms. Prior to antimalarial therapy, mosquito-feeding assays were performed to investigate transmission, and blood samples were collected for rapid diagnostic testing and parasite transcription profiling. Serial blood samples were collected for biomarker analysis. RESULTS: Both subjects experienced symptoms and signs typical of early malaria. Parasitemia was detected 7 days after inoculation, and parasite concentrations increased until antimalarial treatment was initiated 25 and 21 days after inoculation for subjects 1 and 2 respectively (peak parasitemia levels, 174 182 and 50 291 parasites/mL, respectively). The parasite clearance half-life following artemether-lumefantrine treatment was 6.7 hours. Mosquito transmission was observed for 1 subject, while in vivo parasite transcription and biomarkers were successfully profiled. CONCLUSIONS: An IBSM model of P. malariae has been successfully developed and may be used to study the biology of, diagnostic testing for, and treatment of this neglected malaria species. CLINICAL TRIALS REGISTRATION: ACTRN12617000048381.

Early Endothelial Activation Precedes Glycocalyx Degradation and Microvascular Dysfunction in Experimentally Induced Plasmodium falciparum and Plasmodium vivax Infection.

Endothelial activation and microvascular dysfunction are key pathogenic processes in severe malaria. We evaluated the early role of these processes in experimentally induced Plasmodium falciparum and P. vivax infection. Participants were enrolled in induced blood-stage malaria clinical trials. Plasma osteoprotegerin, angiopoietin-2, and von Willebrand Factor (vWF) levels were measured as biomarkers of endothelial activation. Microvascular function was assessed using peripheral arterial tonometry and near-infrared spectroscopy, and the endothelial glycocalyx was assessed by sublingual videomicroscopy and measurement of biomarkers of degradation. Forty-five healthy, malaria-naive participants were recruited from 5 studies. Osteoprotegerin and vWF levels increased in participants following inoculation with P. vivax (n = 16) or P. falciparum (n = 15), with the angiopoietin-2 level also increasing in participants following inoculation with P. falciparum For both species, the most pronounced increase was seen in osteoprotegerin. This was particularly marked in participants inoculated with P. vivax, where the osteoprotegerin level correlated with the levels of parasitemia and the malaria clinical score. There were no changes in measures of endothelial glycocalyx or microvascular function. Plasma biomarkers of endothelial activation increased in early P. falciparum and P. vivax infection and preceded changes in the endothelial glycocalyx or microvascular function. The more pronounced increase in osteoprotegerin suggests that this biomarker may play a role in disease pathogenesis.

A Phase 1, Placebo-controlled, Randomized, Single Ascending Dose Study and a Volunteer Infection Study to Characterize the Safety, Pharmacokinetics, and Antimalarial Activity of the Plasmodium Phosphatidylinositol 4-Kinase Inhibitor MMV390048.

BACKGROUND: MMV390048 is the first Plasmodium phosphatidylinositol 4-kinase inhibitor to reach clinical development as a new antimalarial. We aimed to characterize the safety, pharmacokinetics, and antimalarial activity of a tablet formulation of MMV390048. METHODS: A 2-part, phase 1 trial was conducted in healthy adults. Part 1 was a double-blind, randomized, placebo-controlled, single ascending dose study consisting of 3 cohorts (40, 80, 120 mg MMV390048). Part 2 was an open-label volunteer infection study using the Plasmodium falciparum induced blood-stage malaria model consisting of 2 cohorts (40 mg and 80 mg MMV390048). RESULTS: Twenty four subjects were enrolled in part 1 (n = 8 per cohort, randomized 3:1 MMV390048:placebo) and 15 subjects were enrolled in part 2 (40 mg [n = 7] and 80 mg [n = 8] cohorts). One subject was withdrawn from part 2 (80 mg cohort) before dosing and was not included in analyses. No serious or severe adverse events were attributed to MMV390048. The rate of parasite clearance was greater in subjects administered 80 mg compared to those administered 40 mg (clearance half-life 5.5 hours [95% confidence interval {CI}, 5.2-6.0 hours] vs 6.4 hours [95% CI, 6.0-6.9 hours]; P = .005). Pharmacokinetic/pharmacodynamic modeling estimated a minimum inhibitory concentration of 83 ng/mL and a minimal parasiticidal concentration that would achieve 90% of the maximum effect of 238 ng/mL, and predicted that a single 120-mg dose would achieve an adequate clinical and parasitological response with 92% certainty. CONCLUSIONS: The safety, pharmacokinetics, and pharmacodynamics of MMV390048 support its further development as a partner drug of a single-dose combination therapy for malaria. CLINICAL TRIALS REGISTRATION: NCT02783820 (part 1); NCT02783833 (part 2).

Determining Pneumocystis jirovecii Colonisation from Infection Using PCR-Based Diagnostics in HIV-Negative Individuals.

BACKGROUND: Pneumocystis jirovecii pneumonia is increasingly diagnosed with highly sensitive PCR diagnostics in immunocompromised, HIV-negative individuals. We assessed the performance of our in-house quantitative PCR with the aim to optimise interpretation. METHODS: Retrospective audit of all positive P. jirovecii qPCRs on induced sputum or BAL fluid at a single centre from 2012 to 2023. Medical and laboratory records were analysed and people with HIV were excluded. Cases were categorised as colonisation, high-probability PCP or uncertain PCP infection against a clinical gold standard incorporating clinico-radiological data. Quantitative PCR assay targeting the 5s gene was utilised throughout the time period. RESULTS: Of the 82 positive qPCRs, 28 were categorised as high-probability PCP infection, 30 as uncertain PCP and 24 as colonisation. There was a significant difference in qPCR values stratified by clinical category but not respiratory sample type. Current assay performance with a cutoff of 2.5 × 105 copies/mL had a sensitivity of 50% (95% CI, 30.65-69.35%) and specificity of 83.33% (95% CI, 62.62-95.26%). Youden Index calculated at 6.5 × 104 copies/mL had a sensitivity of 75% (56.64-87.32%, 95% CI) and specificity of 66.67% (46.71-82.03%, 95% CI). High and low cutoffs were explored. Significant variables associated with infection were age > 70 years old, the presence of fever, hypoxia or ground glass changes. CONCLUSIONS: A single qPCR cutoff cannot reliably determine P. jirovecii infection from colonisation. Low and high cutoffs are useful, however, a large "possible infection" cohort will remain where interpretation of clinic-radiological factors remains essential. Standardisation of assays with prospective validation in specific immunocompromised groups will allow greater generalisability and allow large-scale prospective assay validation to be performed.

Osteoprotegerin (OPG) and its ligands RANKL and TRAIL in falciparum, vivax and knowlesi malaria: correlations with disease severity, and B cell production of OPG.

Osteoprotegerin (OPG) is a soluble decoy receptor for receptor activator of NF-ƙB ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL), and is increasingly recognised as a marker of poor prognosis in a number of diseases. Here we demonstrate that in Malaysian adults with falciparum and vivax malaria, OPG is increased, and its ligands TRAIL and RANKL decreased, in proportion to disease severity. In volunteers experimentally infected with P. falciparum and P. vivax, RANKL was suppressed, while TRAIL was unexpectedly increased, suggesting binding of OPG to RANKL prior to TRAIL. We also demonstrate that P. falciparum stimulates B cells to produce OPG in vitro, and that B cell OPG production is increased ex vivo in patients with falciparum, vivax and knowlesi malaria. Our findings provide further evidence of the importance of the OPG/RANKL/TRAIL pathway in pathogenesis of diseases involving systemic inflammation, and may have implications for adjunctive therapies. Further evaluation of the role of B cell production of OPG in host responses to malaria and other inflammatory diseases is warranted.

Tracking SARS-CoV-2 seropositivity in rural communities using blood-fed mosquitoes: a proof-of-concept study.

Background: The spread of SARS-CoV-2 cannot be well monitored and understood in areas without capacity for effective disease surveillance. Countries with a young population will have disproportionately large numbers of asymptomatic or pauci-symptomatic infections, further hindering detection of infection. Sero-surveillance on a country-wide scale by trained medical professionals may be limited in a resource-limited setting such as Mali. Novel ways of broadly sampling the human population in a non-invasive method would allow for large-scale surveillance at a reduced cost. Approach: Here we evaluate the collection of naturally blood-fed mosquitoes to test for human anti-SARS-CoV-2 antibodies in the laboratory and at five field locations in Mali. Results: Immunoglobulin-G antibodies to multiple SARS-CoV-2 antigens were readily detected in mosquito bloodmeals by bead-based immunoassay through at least 10 h after feeding [mean sensitivity of 0.92 (95% CI 0.78-1) and mean specificity of 0.98 (95% CI 0.88-1)], indicating that most blood-fed mosquitoes collected indoors during early morning hours (and likely to have fed the previous night) are viable samples for analysis. We found that reactivity to four SARS-CoV-2 antigens rose during the pandemic from pre-pandemic levels. The crude seropositivity of blood sampled via mosquitoes was 6.3% in October and November 2020 across all sites, and increased to 25.1% overall by February 2021, with the most urban site reaching 46.7%, consistent with independent venous blood-based sero-surveillance estimates. Conclusions: We have demonstrated that using mosquito bloodmeals, country-wide sero-surveillance of human diseases (both vector-borne and non-vector-borne) is possible in areas where human-biting mosquitoes are common, offering an informative, cost-effective, and non-invasive sampling option.

Positron emission tomography and magnetic resonance imaging of the brain in experimental human malaria, a prospective cohort study.

Cerebral malaria is the most serious manifestation of severe falciparum malaria. Sequestration of infected red blood cells and microvascular dysfunction are key contributing processes. Whether these processes occur in early stage disease prior to clinical manifestations is unknown. To help localize and understand these processes during the early stages of infection, we performed 18-F fluorodeoxyglucose positron emission tomography/magnetic resonance imaging in volunteers with Plasmodium falciparum induced blood stage malaria (IBSM) infection, and compared results to individuals with P. vivax infection, in whom coma is rare. Seven healthy, malaria-naïve participants underwent imaging at baseline, and at early symptom onset a median 9 days following inoculation (n = 4 P. falciparum, n = 3 P. vivax). Participants with P. falciparum infection demonstrated marked lability in radiotracer uptake across all regions of the brain, exceeding expected normal variation (within subject coefficient of variation (wCV): 14.4%) compared to the relatively stable uptake in participants with P. vivax infection (wCV: 3.5%). No consistent imaging changes suggestive of microvascular dysfunction were observed in either group. Neuroimaging in early IBSM studies is safe and technically feasible, with preliminary results suggesting that differences in brain tropism between P. falciparum and P. vivax may occur very early in infection.

Recent malaria does not substantially impact COVID-19 antibody response or rates of symptomatic illness in communities with high malaria and COVID-19 transmission in Mali, West Africa.

Malaria has been hypothesized as a factor that may have reduced the severity of the COVID-19 pandemic in sub-Saharan Africa. To evaluate the effect of recent malaria on COVID-19 we assessed a subgroup of individuals participating in a longitudinal cohort COVID-19 serosurvey that were also undergoing intensive malaria monitoring as part of antimalarial vaccine trials during the 2020 transmission season in Mali. These communities experienced a high incidence of primarily asymptomatic or mild COVID-19 during 2020 and 2021. In 1314 individuals, 711 were parasitemic during the 2020 malaria transmission season; 442 were symptomatic with clinical malaria and 269 had asymptomatic infection. Presence of parasitemia was not associated with new COVID-19 seroconversion (29.7% (211/711) vs. 30.0% (181/603), p=0.9038) or with rates of reported symptomatic seroconversion during the malaria transmission season. In the subsequent dry season, prior parasitemia was not associated with new COVID-19 seroconversion (30.2% (133/441) vs. 31.2% (108/346), p=0.7499), with symptomatic seroconversion, or with reversion from seropositive to seronegative (prior parasitemia: 36.2% (64/177) vs. no parasitemia: 30.1% (37/119), p=0.3842). After excluding participants with asymptomatic infection, clinical malaria was also not associated with COVID-19 serostatus or symptomatic seroconversion when compared to participants with no parasitemia during the monitoring period. In communities with intense seasonal malaria and a high incidence of asymptomatic or mild COVID-19, we did not demonstrate a relationship between recent malaria and subsequent response to COVID-19. Lifetime exposure, rather than recent infection, may be responsible for any effect of malaria on COVID-19 severity.

SARS-CoV-2 seroassay optimization and performance in a population with high background reactivity in Mali.

Serological tests are an indispensable tool to understand the epidemiology of the SARS-CoV-2 pandemic, particularly in areas where molecular diagnostics are limited. Poor assay performance may hinder the utility of these tests, including high rates of false-positivity previously reported in sub-Saharan Africa. From 312 Malian samples collected prior to 2020, we measured antibodies to the commonly tested SARS-CoV-2 antigens and four other betacoronaviruses by ELISA, and assessed functional cross-reactivity in a subset by SARS-CoV-2 pseudovirus neutralization assay. We then evaluated the performance of an ELISA developed in the US, using two-antigen SARS-CoV-2 spike protein and receptor-binding domain. To optimize test performance, we compared single and two-antigen approaches using existing assay cutoffs and population-specific cutoffs for Malian control samples (positive and negative). Background reactivity to SARS-CoV-2 antigens was common in pre-pandemic samples compared to US controls (43.4% (135/311) for spike protein, 22.8% (71/312) for RBD, and 33.9% (79/233) for nucleocapsid protein). SARS-CoV-2 reactivity correlated weakly with other betacoronavirus reactivity, varied between Malian communities, and increased with age. No pre-pandemic samples demonstrated functional activity. Regardless of the cutoffs applied, specificity improved using a two-antigen approach. Test performance was optimal using a two-antigen assay with population-specific cutoffs derived from ROC curve analysis [Sensitivity: 73.9% (51.6-89.8), Specificity: 99.4% (97.7-99.9)]. In the setting of high background reactivity, such as sub-Saharan Africa, SARS-CoV-2 serological assays need careful qualification is to characterize the epidemiology of disease, prevent unnecessary harm, and allocate resources for targeted control measures.

Rapidly increasing SARS-CoV-2 seroprevalence and limited clinical disease in three Malian communities: a prospective cohort study.

Background: The extent of SARS-CoV-2 exposure and transmission in Mali and the surrounding region is not well understood, although infection has been confirmed in nearly 14,000 symptomatic individuals and their contacts since the first case in March 2020. We aimed to estimate the cumulative incidence of SARS-CoV-2 in three Malian communities, and understand factors associated with infection. Methods: Between 27 July 2020 and 29 January 2021, we collected blood samples along with demographic, social, medical and self-reported symptoms information from residents aged 6 months and older in three study communities at two study visits. SARS-CoV-2 antibodies were measured using a highly specific two-antigen ELISA optimized for use in Mali. We calculated cumulative adjusted seroprevalence for each site and evaluated factors associated with serostatus at each visit by univariate and multivariate analysis. Findings: Overall, 94.8% (2533/2672) of participants completed both study visits. A total of 50.3% (1343/2672) of participants were male, and 31.3% (837/2672) were aged <10 years, 27.6% (737/2672) were aged 10-17 years, and 41.1% (1098/2572) were aged ≥18 years. The cumulative SARS-CoV-2 exposure rate was 58.5% (95% CI: 47.5 to 69.4). This varied between sites and was 73.4% (95% CI: 59.2 to 87.5) in the urban community of Sotuba, 53.2% (95% CI: 42.8 to 63.6) in the rural town of Bancoumana, and 37.1% (95% CI: 29.6 to 44.5) in the rural village of Donéguébougou. This equates to an infection rate of approximately 1% of the population every three days in the study communities between visits. Increased age and study site were associated with serostatus at both study visits. There was minimal difference in reported symptoms based on serostatus. Interpretation: The true extent of SARS-CoV-2 exposure in Mali is greater than previously reported and now approaches hypothetical herd immunity in urban areas. The epidemiology of the pandemic in the region may be primarily subclinical and within background illness rates. In this setting, ongoing surveillance and augmentation of diagnostics to characterize locally circulating variants will be critical to implement effective mitigation strategies like vaccines. Funding: This project was funded by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases, National Institute of Biomedical Imaging and Bioengineering, and National Cancer Institute.

Safety, tolerability, pharmacokinetics, and antimalarial efficacy of a novel Plasmodium falciparum ATP4 inhibitor SJ733: a first-in-human and induced blood-stage malaria phase 1a/b trial.

BACKGROUND: (+)-SJ000557733 (SJ733) is a novel, orally bioavailable inhibitor of Plasmodium falciparum ATP4. In this first-in-human and induced blood-stage malaria phase 1a/b trial, we investigated the safety, tolerability, pharmacokinetics, and antimalarial activity of SJ733 in humans. METHODS: The phase 1a was a single-centre, dose-escalation, first-in-human study of SJ733 allowing modifications to dose increments and dose-cohort size on the basis of safety and pharmacokinetic results. The phase 1a took place at St Jude Children's Research Hospital and at the University of Tennessee Clinical Research Center (Memphis, TN, USA). Enrolment in more than one non-consecutive dose cohort was allowed with at least 14 days required between doses. Participants were fasted in seven dose cohorts and fed in one 600 mg dose cohort. Single ascending doses of SJ733 (75, 150, 300, 600, 900, or 1200 mg) were administered to participants, who were followed up for 14 days after SJ733 dosing. Phase 1a primary endpoints were safety, tolerability, and pharmacokinetics of SJ733, and identification of an SJ733 dose to test in the induced blood-stage malaria model. The phase 1b was a single-centre, open-label, volunteer infection study using the induced blood-stage malaria model in which fasted participants were intravenously infected with blood-stage P falciparum and subsequently treated with a single dose of SJ733. Phase 1b took place at Q-Pharm (Herston, QLD, Australia) and was initiated only after phase 1a showed that exposure exceeding the threshold minimum exposure could be safely achieved in humans. Participants were inoculated on day 0 with P falciparum-infected human erythrocytes (around 2800 parasites in the 150 mg dose cohort and around 2300 parasites in the 600 mg dose cohort), and parasitaemia was monitored before malaria inoculation, after inoculation, immediately before SJ733 dosing, and then post-dose. Participants were treated with SJ733 within 24 h of reaching 5000 parasites per mL or at a clinical score higher than 6. Phase 1b primary endpoints were calculation of a parasite reduction ratio (PRR48) and parasite clearance half-life, and safety and tolerability of SJ733 (incidence, severity, and drug-relatedness of adverse events). In both phases of the trial, SJ733 hydrochloride salt was formulated as a powder blend in capsules containing 75 mg or 300 mg for oral administration. Healthy men and women (of non-childbearing potential) aged 18-55 years were eligible for both studies. Both studies are registered with ClinicalTrials.gov (NCT02661373 for the phase 1a and NCT02867059 for the phase 1b). FINDINGS: In the phase 1a, 23 healthy participants were enrolled and received one to three non-consecutive doses of SJ733 between March 14 and Dec 7, 2016. SJ733 was safe and well tolerated at all doses and in fasted and fed conditions. 119 adverse events were recorded: 54 (45%) were unrelated, 63 (53%) unlikely to be related, and two (2%) possibly related to SJ733. In the phase 1b, 17 malaria-naive, healthy participants were enrolled. Seven participants in the 150 mg dose cohort were inoculated and dosed with SJ733. Eight participants in the 600 mg dose cohort were inoculated, but two participants could not be dosed with SJ733. Two additional participants were subsequently inoculated and dosed with SJ733. SJ733 exposure increased proportional to the dose through to the 600 mg dose, then was saturable at higher doses. Fasted participants receiving 600 mg exceeded the target area under the concentration curve extrapolated to infinity (AUC0-∞) of 13 000 µg × h/L (median AUC0-∞ 24 283 [IQR 16 135-31 311] µg × h/L, median terminal half-life 17·4 h [IQR 16·1-24·0], and median timepoint at which peak plasma concentration is reached 1·0 h [0·6-1·3]), and this dose was tested in the phase 1b. All 15 participants dosed with SJ733 had at least one adverse event. Of the 172 adverse events recorded, 128 (74%) were mild. The only adverse event attributed to SJ733 was mild bilateral foot paraesthesia that lasted 3·75 h and resolved spontaneously. The most common adverse events were related to malaria. Based on parasite clearance half-life, the derived log10PRR48 and corresponding parasite clearance half-lives were 2·2 (95% CI 2·0-2·5) and 6·47 h (95% CI 5·88-7·18) for 150 mg, and 4·1 (3·7-4·4) and 3·56 h (3·29-3·88) for 600 mg. INTERPRETATION: The favourable pharmacokinetic, tolerability, and safety profile of SJ733, and rapid antiparasitic effect support its development as a fast-acting component of combination antimalarial therapy. FUNDING: Global Health Innovative Technology Fund, Medicines for Malaria Venture, and the American Lebanese Syrian Associated Charities.

The Dynamics of Liver Function Test Abnormalities after Malaria Infection: A Retrospective Observational Study.

Liver dysfunction has long been recognized as a clinical feature of malaria. We have observed delayed elevation in the transaminase portion of liver function tests (LFTs) after treatment in some participants undergoing induced blood stage malaria infection. We sought to determine whether similar LFT elevations occur after naturally acquired infection. We performed a retrospective audit of confirmed cases of Plasmodium falciparum and Plasmodium vivax in Queensland, Australia, from 2006 to 2016. All LFT results from malaria diagnosis until 28 days after diagnosis were collected with demographic and clinical information to describe longitudinal changes. The timing of peak LFT elevations was classified as early (0-3 days), delayed (4-11 days), or late (12-28 days) with respect to the day of diagnosis. Among 861 cases with LFT evaluated, an elevated bilirubin level was identified in 12.4% (N = 107/861), whereas elevated alanine transaminase (ALT) and aspartate transaminase levels were observed in 15.1% (N = 130/861) and 14.8% (N = 127/861) of cases, respectively. All peak bilirubin results occurred in the early period, whereas ALT elevations were biphasic, with elevations in the early and delayed periods, with 35.4% (N = 46/130) of cases delayed. Univariate and paired stepwise logistic regression analyses were performed to investigate factors associated with the incidence and timing of transaminase elevation. A raised ALT level at diagnosis was strongly associated with the timing of transaminase elevation. No other demographic, parasitic, or treatment factors were associated. Liver function test abnormalities are likely an inherent although variable aspect of human malaria, and individual-specific factors may confer susceptibility to hepatocyte injury.