Genesis of placental sequestration in malaria and possible targets for drugs for placental malaria

Imported malaria in pregnancy in Europe: A systematic review of the literature of the last 25 years

BACKGROUND

Malaria during pregnancy is associated with a greater risk of complications for the mother and fetus. The aim of the study is to analyze the features of imported cases of malaria in pregnant women in Europe and evaluate which factors are associated with a non-favourable outcome.

METHODS

A computerized search of the literature was performed combining the terms plasmod*, malaria, pregnan*, maternal, gravid, parturient, expectant, and congenital, from January 1997 to July 2023.

RESULTS

28 articles reporting 57 cases of malaria in pregnant women immigrant in non-endemic areas were included. The patients mainly came from Sub-Saharan Africa. There were 10 asymptomatic cases, while the predominant clinical syndrome among the symptomatic women was fever associated with anaemia. The median latency period from permanence in endemic areas and diagnosis in European countries was 180 days (IQR 15-730). Pregnancy outcomes were favourable in 35 cases (61 %): all term pregnancies, no low-birth-weight newborns. There were 4 abortions; 1 child was delivered pre-term; 7 babies were reported to have a low birth weight; 10 cases of congenital malaria were documented. P. falciparum was found with a higher frequency in women with a favourable outcome, while P. vivax was, in all cases, associated with a worse prognosis.

CONCLUSIONS

Diagnosis of malaria in pregnant woman in non-endemic countries may be challenging and a delay in diagnosis may lead to an adverse outcome. Screening for malaria should be performed in pregnant women from endemic areas, especially if they present anaemia or fever.

Nanocarrier based active targeting strategies against erythrocytic stage of malaria

The Global Technical Strategy for Malaria 2016-2030 aims to achieve a 90% reduction in malaria cases, and strategic planning and execution are crucial for accomplishing this target. This review aims to understand the complex interaction between erythrocytic receptors and parasites and to use this knowledge to actively target the erythrocytic stage of malaria. The review provides insight into the malaria life cycle, which involves various receptors such as glycophorin A, B, C, and D (GPA/B/C/D), complement receptor 1, basigin, semaphorin 7a, Band 3/ GPA, Kx, and heparan sulfate proteoglycan for parasite cellular binding and ingress in the erythrocytic and exo-erythrocytic stages. Synthetic peptides mimicking P. falciparum receptor binding ligands, human serum albumin, chondroitin sulfate, synthetic polymers, and lipids have been utilized as ligands and decorated onto nanocarriers for specific targeting to parasite-infected erythrocytes. The need of the hour for treatment and prophylaxis against malaria is a broadened horizon that includes multiple targeting strategies against the entry, proliferation, and transmission stages of the parasite. Platform technologies with established pre-clinical safety and efficacy should be translated into clinical evaluation and formulation scale-up. Future development should be directed towards nanovaccines as proactive tools against malaria infection.

Immunohistopathological changes in the placenta of malaria-infected women in unstable transmission setting of Aligarh

INTRODUCTION

Pregnant women are more susceptible to malaria due to a combination of physiological and immunological changes. The infection may even affect the growth and survival of the foetus, which mainly occur when parasite enters the placenta. The sequestration of infected erythrocytes may trigger the host response, leading to placental inflammation and altered development, affecting the structure and nutrient transport of placenta. These factors collectively impair placental functions and affect foetal growth.

METHODS

Pregnant women with peripheral parasitaemia for P. falciparum and P. vivax (20 each) were included in the present study, along with 15 age-matched uninfected healthy pregnant women. Placentae were analysed for the presence of local parasitaemia along with pathological lesions caused due to the parasite. Immunohistochemical staining for CD20, CD45 and CD68 cells was performed for examining the specific leucocytes in the intervillous space of the placenta.

RESULTS

Of the 20 individuals with P. falciparum, only seven placentae showed parasitaemia, whereas individuals with P. vivax showed no placental infection. The pathological changes observed in the P. falciparum-infected placenta include syncytial knotting, excess fibrinoid deposition, syncytiotrophoblast necrosis, syncytial rupture, thickening of trophoblast basement membrane and increased collagen deposition. Immunohistochemical staining showed a significant increase in B cells (CD20), leucocytes (CD45) and monocytes and macrophages (CD68) in the P. falciparum-infected placenta (p < 0.0001).

DISCUSSION

The result implies that P. falciparum is responsible for pathological alterations in placenta, affecting the nutrient transport across placenta and foetal growth. The immune cells also migrate to the placenta and accumulate in the intervillous space to show humoral and cell-mediated immunity against the parasite.

Anti-inflammatory effects of a SERP 30 polysaccharide from the residue of Sarcandra glabra against lipopolysaccharide-induced acute respiratory distress syndrome in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Sarcandra glabra (Thunb.) Nakai, a valuable dietetic Chinese herb, is still widely used today. Multiple ingredients of S. glabra with a variety of activities such as anti-inflammatory, antiviral, and antitumor were studied. However, the Sarcandra glabra (Thunb.) Nakai polysaccharide hasn't been reported for its anti-inflammatory effect.

AIM OF THE STUDY

In this study, the anti-inflammatory activity of Sarcandra glabra (Thunb.) Nakai polysaccharide was assessed in LPS-induced ARDS mice.

MATERIALS AND METHODS

A polysaccharide coded as SERP 30 was obtained by water extraction, alcohol precipitation, and gel filtration. After the physicochemical properties determination and structural characterization, LPS induced-mice ARDS model was used to evaluate the anti-inflammatory and associated antioxidant activities of SERP 30. H&E staining was used to observe the seriousness of lung injury in mice. The ELISA method was used to measure the expression of inflammatory factors (TNF-α and IL-6) in the serum of the mice. The TBA method and the WST-1 method were used to evaluate the oxidative stress injury. Immunohistochemistry was used to distinguish the expression of metalloproteinase-9 (MMP-9), heparinase (HPA), syndecan-1, and decorin in ARDS-mice lung tissue. Western blotting was used to confirm the expression of related proteins in mouse lung tissue.

RESULTS

SERP 30 had a potential role in improving lung damage, reducing inflammation, and preventing oxidative stress. Moreover, SERP 30 significantly attenuated the damage to the endothelial glycocalyx and maintained the integrity of the glycocalyx. The western blotting result implied that the main anti-inflammatory mechanism is directed towards NF-κB and MAPK signaling pathways with inhibiting the activation of associated proteins.

CONCLUSION

This research provides a theoretical basis for treating ARDS by using a byproduct from food resource.

Safety of Treating Malaria with Artemisinin-Based Combination Therapy in the First Trimester of Pregnancy

There have been recent calls for the use of artemisinin-based combination therapies (ACTs) for uncomplicated malaria in the first trimester of pregnancy. Nevertheless, the 2021 WHO Guidelines for Malaria reaffirmed their position that there is not adequate clinical safety data on artemisinins to support that usage. The WHO's position is consistent with several issues with the existing clinical data. First, first trimester safety results from multiple ACTs were lumped in a meta-analysis which does not demonstrate that each of the included ACTs is equally safe. Second, safety results from all periods of the first trimester were lumped in the meta-analysis which does not demonstrate the same level of safety for all subperiods, particularly gestational Weeks 6 to 8 which is likely to be the most sensitive period. Third, even if there is evidence of a lack of an effect on miscarriage for a particular ACT, it does not follow then there are no developmental effects for any ACT. In monkeys, artesunate caused marked embryonal anemia leading to embryo death but the long-term consequences of lower levels of embryonal anemia are not known. Fourth, there have been advances in the sensitivity and usage of rapid diagnostic tests that will lead to diagnoses of malaria earlier in gestation which is less well studied and more likely sensitive to artemisinins. Any clinical studies of the safety of ACTs in the first trimester need to evaluate the results of treatment with individual ACTs during different 1- to 2-week periods of the first trimester.

Age-modified factors associated with placental malaria in rural Burkina Faso

BACKGROUND

Malaria in pregnancy can result in placental infection with fetal implications. This study aimed at assessing placental malaria (PM) prevalence and its associated factors in a cohort of pregnant women with peripheral malaria and their offspring.

METHOD

The data were collected in the framework of a clinical trial on treatments for malaria in pregnant women . Placental malaria (PM) was diagnosed by histopathological detection of parasites and/or malaria pigment on placenta biopsies taken at delivery. Factors associated with PM were assessed using logistic regression.

RESULTS

Out of 745 biopsies examined, PM was diagnosed in 86.8 % of women. Acute, chronic and past PM were retrieved in 11 (1.5 %), 170 (22.8 %), and 466 (62.6 %) women, respectively. A modifying effect was observed in the association of gravidity or anemia at the study start with pooled PM (presence of parasites and/or malaria pigment). In women under 30, gravidity ≤ 2 was associated with an increased prevalence of pooled PM but in women aged 30 years or more, gravidity was no more associated with pooled PM (OR 6.81, 95 % CI 3.18 - 14.60; and OR 0.52, 95 % CI 0.10 - 2.76, respectively). Anemia was associated with pooled PM in women under 30 (OR 1.96, 95 % CI 1.03 - 3.72) but not in women aged 30 years or more (OR 0.68, 95 % CI 0.31 - 1.49). Similarly, the association of gravidity with past-chronic PM depended also on age. A higher prevalence of active PM was observed in women under 30 presenting with symptomatic malaria (OR 3.79, 95 % CI 1.55 - 9.27), while there was no significant increase in the prevalence of active PM (presence of parasites only) in women with symptomatic malaria when aged 30 years or more (OR 0.42, 95 % CI 0.10 - 1.75). In women with chronic PM, the prevalence of low birth weight or prematurity was the highest (31.2 %) as compared with past PM or no PM.

CONCLUSION

Despite the rapid diagnosis and efficacious treatment of peripheral infection, the prevalence of placental malaria remained high in women with P. falciparum peripheral infection in Nanoro, especially in younger women This underlines the importance of preventive measures in this specific group.

Diagnosis of malaria in pregnancy: accuracy of CareStart™ malaria Pf/PAN against light microscopy among symptomatic pregnant women at the Central Hospital in Yaoundé, Cameroon

Background

The need to start treatment early for pregnant women who present with clinical features of malaria usually conflicts with the need to confirm diagnosis by microscopy (MP) before treatment, due to delays in obtaining results. Parasite sequestration in the placenta is also a problem. Rapid diagnostic tests (RDT), which detect soluble antigens, are a valuable alternative. The objective of this study was to evaluate pretreatment parasite prevalence by microscopy and by RDT and to assess the accuracy of RDT with MP as reference.

Methods

A prospective cross-sectional study was carried out at the obstetrical unit of the Central Hospital in Yaoundé, during the period January-August 2015. Consenting patients with symptoms of suspected malaria in pregnancy were recruited and a blood sample taken for MP and RDT before treatment was started. The estimates of diagnostic performance (with 95% confidence interval) were calculated in OpenEpi online software using the Wilson’s score. The agreement, as reflected by the Cohen’s kappa, was calculated and interpreted using known intervals.

Results

The results showed that, out of the 104 patients recruited, 69.2% (95%CI: 59.1–77.5) were MP positive while 77.94% (95%CI: 63.1–80.9) were RDT positive. The sensitivity of the malaria RDT was 91.67% (95%CI: 83.69–96.77) while the specificity was 53.13% (95%CI: 31.39–65.57). The diagnostic accuracy of the RDT with MP as reference was 79.81% (95%CI: 70.0–86.1). All cases were due to Plasmodium falciparum. A Cohen’s kappa of 0.45 (95%CI: 0.26–0.64) was obtained, consistent with a moderate agreement between the tests.

Conclusions

The diagnostic accuracy of the CareStart™ malaria Pf/PAN compared to microscopy was high, but not as desirable, with a false negative RDT at very high parasitaemia. In tertiary facilities, RDTs appear to provide a better diagnostic solution compared to microscopy. However, future studies with larger sample sizes should make this observation more generalizable; as missing a case could have serious consequences on pregnancy outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04109-6.

Syndecan-1 Shedding by Matrix Metalloproteinase-9 Signaling Regulates Alveolar Epithelial Tight Junction in Lipopolysaccharide-Induced Early Acute Lung Injury

Introduction

Alveolar epithelial tight junction damage and glycocalyx syndecan-1 (SDC-1) degrading are key factors to pulmonary edema of acute lung injury (ALI). Matrix metalloproteinase-9 (MMP-9) was involved in glycocalyx shedding, which was vital in SDC-1 degrading. This study aimed to investigate the effects of MMP-9-mediated SDC-1 shedding on tight junction in LPS-induced ALI.

Methods

Mice were intratracheally atomized with 5 mg/kg LPS to stimulate different periods and LPS stimulation for 6 hours for further studies. A549 cells was stimulated for 6 hours by active MMP-9 protein to assess the effects of active MMP-9 protein on SDC-1 and tight junction. Afterward, the mice treated with MMP-9 shRNA or A549 cells were treated with MMP-9 siRNA before LPS stimulation for 6 hours to explore the effects on glycocalyx SDC-1 and tight junction. Moreover, the mice were treated with recombinant SDC-1 protein or A549 cells were over-expressed by pc-SDC-1 before LPS stimulation for 6 hours to explore the effects of SDC-1 on tight junction.

Results

The mice persistent exposure to LPS showed that MMP-9 expression, glycocalyx SDC-1 shedding (SDC-1 decreased in alveolar epithelium and increased in the BALF), tight junction impairment, FITC-albumin infiltration, and other phenomena began to appear after 6 hours of LPS treatment in this study. The levels of SDC-1 and tight junction significantly decreased by active MMP-9 protein stimulation for 6 hours in the A549 cells. Therefore, LPS stimulation for six hours was selected for investigating the underlying effects of MMP-9-mediated SDC-1 shedding on the alveolar epithelial tight junction and pulmonary edema. Further vivo analysis showed that down regulation MMP-9 expression by MMP-9 shRNA significantly alleviated glycocalyx SDC-1 shedding (SDC-1 increased in alveolar epithelium and decreased in the BALF), tight junction (occludin and ZO-1) damage, and FITC-albumin infiltration in LPS-induced early ALI mice. The vitro results also showed that MMP-9 siRNA alleviated glycocalyx SDC-1 shedding (SDC-1 increased in cell culture medium and decreased in cell surface) and tight junction damage by downregulating MMP-9 expression in LPS-stimulated A549 cells. In addition, pretreatment with recombinant mouse SDC-1 protein significantly alleviated glycocalyx (SDC-1 increased in alveolar epithelium) and tight junction damage, and FITC-albumin infiltration in LPS-induced early ALI mice. Overexpression SDC-1 by pc-SDC-1 also significantly decreased tight junction damage in LPS-stimulated A549 cells.

Conclusion

Glycocalyx SDC-1 shedding mediated by MMP-9 significantly aggravated tight junction damage, which further increased the pulmonary edema.

Congenital Transmission of Apicomplexan Parasites: A Review

Apicomplexans are a group of pathogenic protists that cause various diseases in humans and animals that cause economic losses worldwide. These unicellular eukaryotes are characterized by having a complex life cycle and the ability to evade the immune system of their host organism. Infections caused by some of these parasites affect millions of pregnant women worldwide, leading to various adverse maternal and fetal/placental effects. Unfortunately, the exact pathogenesis of congenital apicomplexan diseases is far from being understood, including the mechanisms of how they cross the placental barrier. In this review, we highlight important aspects of the diseases caused by species of Plasmodium, Babesia, Toxoplasma, and Neospora, their infection during pregnancy, emphasizing the possible role played by the placenta in the host-pathogen interaction.

Assessing field performance of ultrasensitive rapid diagnostic tests for malaria: a systematic review and meta-analysis

Background

To overcome the limitations of conventional malaria rapid diagnostic tests (cRDTs) in diagnosing malaria in patients with low parasitaemia, ultrasensitive malaria rapid diagnostic tests (uRDTs) have recently been developed, with promising results under laboratory conditions. The current study is the first meta-analysis comparing the overall sensitivity, and specificity of newly developed ultrasensitive Plasmodium falciparum malaria RDT (Alere™ Ultra-sensitive Malaria Ag P. falciparum RDT) with the cRDT conducted in the same field conditions.

Methods

PubMed, EMBASE, Cochrane infectious diseases group specialized register, and African Journals Online (AJOL) were searched up to 20^th April 2021. Studies with enough data to compute sensitivity and specificity of uRDT and cRDT were retrieved. A random-effect model for meta-analysis was used to obtain the pooled sensitivity and specificity.

Results

Overall, 15 data sets from 14 studies were included in the meta-analysis. The overall sensitivity of the Alere™ ultra-sensitive Malaria Ag P. falciparum RDT regardless of the reference test and the clinical presentation of participants, was 55.5% (95% confidence interval [CI]: 45.5; 65.0), while the sensitivity regardless of the reference test and the clinical presentation of participants, was 42.9% (95% CI: 31.5; 55.2) for the cRDT performed in the same field conditions. When PCR was used as reference test, the sensitivity of uRDT was 60.4% (95% CI: 50.8; 69.2), while the sensitivity was 49.4% (95% CI: 38.2; 60.6) for the cRDT. The pooled specificity of uRDT regardless of the reference test and the clinical presentation of participants was 98.6% (95% CI: 97.1; 99.4), and the pooled specificity of cRDT regardless of the reference test and the clinical presentation of participants was 99.3% (95% CI: 98.1; 99.7). When PCR was used as reference test the specificity of uRDT and cRDT was 97.5% (95% CI: 94.1; 98.9) and 98.2% (95% CI: 95.5; 99.3). Regardless of the reference test used, the sensitivity of Alere™ Ultra-sensitive Malaria Ag P. falciparum RDT in symptomatic patients was 72.1% (95%CI: 67.4; 76.4), while sensitivity of cRDT was 67.4% (95%CI: 57.6; 75.9).

Conclusion

Findings of the meta-analysis show that Alere™ Ultra-sensitive Malaria Ag P. falciparum RDT compared to cRDT performed in the same field conditions has higher sensitivity but lower specificity although the difference is not statistically significant.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03783-2.

Teratogen update: Malaria in pregnancy and the use of antimalarial drugs in the first trimester

Malaria is a particular problem in pregnancy because of enhanced sensitivity, the possibility of placental malaria, and adverse effects on pregnancy outcome. Artemisinin-containing combination therapies (ACTs) are the most effective antimalarials known. WHO recommends 7-day quinine therapy for uncomplicated Plasmodium falciparum malaria in the first trimester despite the superior tolerability and efficacy of 3-day ACT regimens because artemisinins caused embryolethality and/or cardiovascular malformations at relatively low doses in rats, rabbits, and monkeys. The developmental toxicity of artesunate, artemether, and DHA were similar in rats but artesunate was embryotoxic at lower doses in rabbits (5 mg/kg/day) than artemether (no effect level = 25 mg/kg/day). In clinical studies in Africa, treatment with artemether-lumefantrine in the first trimester was observed to be highly efficacious and the miscarriage rate (≤3.1%) was similar to no antimalarial treatment (2.6%). When data from the first-trimester use of largely artesunate-based therapies in Thailand were pooled together, there was no difference in miscarriage rate compared to quinine. However, individually, artesunate-mefloquine was associated with a higher miscarriage rate (15/71 = 21%) compared to other artemisinin-based therapies including 7-day artesunate + clindamycin (2/50 = 4%) and quinine (92/842 = 11%). Thus, appropriate statistical comparisons of individual ACT groups are needed prior to assuming that they all have the same risk for developmental toxicity. Current limitations in the assessment of the safety of ACTs in the first trimester are a lack of exposures early in gestation (gestational weeks 6-7), limited postnatal evaluation for cardiovascular malformations, and the pooling of all ACTs for the assessment of risk.

Placental Malaria

Purpose of Review

Placental malaria is the primary mechanism through which malaria in pregnancy causes adverse perinatal outcomes. This review summarizes recent work on the significance, pathogenesis, diagnosis, and prevention of placental malaria.

Recent Findings

Placental malaria, characterized by the accumulation of Plasmodium-infected red blood cells in the placental intervillous space, leads to adverse perinatal outcomes such as stillbirth, low birth weight, preterm birth, and small-for-gestational-age neonates. Placental inflammatory responses may be primary drivers of these complications. Associated factors contributing to adverse outcomes include maternal gravidity, timing of perinatal infection, and parasite burden.

Summary

Placental malaria is an important cause of adverse birth outcomes in endemic regions. The main strategy to combat this is intermittent preventative treatment in pregnancy; however, increasing drug resistance threatens the efficacy of this approach. There are studies dissecting the inflammatory response to placental malaria, alternative preventative treatments, and in developing a vaccine for placental malaria.

Safety of Artemisinin Derivatives in the First Trimester of Pregnancy: A Controversial Story

Artemisinin combination therapy (ACT) is recommended by the World Health Organization (WHO) as first line treatment for uncomplicated malaria both in adults and children. During pregnancy, ACT is considered safe only in the second and third trimester, since animal studies have demonstrated that artemisinin derivatives can cause foetal death and congenital malformation within a narrow time window in early embryogenesis. During this period, artemisinin derivatives induce defective embryonic erythropoiesis and vasculogenesis/angiogenesis in experimental models. However, clinical data on the safety profile of ACT in pregnant women have not shown an increased risk of miscarriage, stillbirth, or congenital malformation, nor low birth weight, associated with exposure to artemisinins in the first trimester. Although further studies are needed, the evidence collected up to now is prompting the WHO towards a change in the guidelines for the treatment of uncomplicated malaria, allowing the use of ACT also in the first trimester of pregnancy.

Genesis of placental sequestration in malaria and possible targets for drugs for placental malaria

Malaria during pregnancy results in intrauterine growth restriction, fetal anemia, and infant mortality. Women are more susceptible to malaria during pregnancy due to malaria‐induced inflammation and the sequestration of infected red blood cells in the placenta, which bind to the chondroitin sulfate portion of syndecan‐1 on the syncytiotrophoblast and in the intervillous space. Syndecan‐1 is a dimeric proteoglycan with an extracellular ectodomain that is cleaved from the transmembrane domain (referred to as “shedding”) by matrix metalloproteinases (MMPs), likely the secreted MMP‐9. The ectodomain includes four binding sites for chondroitin sulfate, which are proximal to the transmembrane domain, and six distal binding sites primarily for heparan sulfate. This “shedding” of syndecan‐1 is inhibited by the presence of the heparan sulfate chains, which can be removed by heparanase. The intervillous space contains fibrin strands and syndecan‐1 ectodomains free of heparan sulfate. The following is proposed as the sequence of events that leads to and is primarily responsible for sequestration in the intervillous space of the placenta. Inflammation associated with malaria triggers increased heparanase activity that degrades the heparan sulfate on the membrane‐bound syndecan‐1. Inflammation also upregulates MMP‐9 and the removal of heparan sulfate gives MMP‐9 access to cleave syndecan‐1, thereby releasing dimeric syndecan‐1 ectodomains with at least four chondroitin sulfate chains attached. These multivalent ectodomains bind infected RBCs together leading to their aggregation and entrapment in intervillous fibrin. This mechanism suggests possible new targets for anti‐placental malaria drugs such as the inhibition of MMP‐9. Doxycycline is an antimalarial drug which inhibits MMP‐9.