Macrophage migration inhibitory factor is required for NLRP3 inflammasome activation.

Macrophage migration inhibitory factor (MIF) exerts multiple effects on immune cells, as well as having functions outside the immune system. MIF can promote inflammation through the induction of other cytokines, including TNF, IL-6, and IL-1 family cytokines. Here, we show that inhibition of MIF regulates the release of IL-1α, IL-1ß, and IL-18, not by affecting transcription or translation of these cytokines, but via activation of the NLRP3 inflammasome. MIF is required for the interaction between NLRP3 and the intermediate filament protein vimentin, which is critical for NLRP3 activation. Further, we demonstrate that MIF interacts with NLRP3, indicating a role for MIF in inflammasome activation independent of its role as a cytokine. These data advance our understanding of how MIF regulates inflammation and identify it as a factor critical for NLRP3 inflammasome activation.

P. falciparum infection and maternofetal antibody transfer in malaria-endemic settings of varying transmission.

INTRODUCTION: During pregnancy, immunoglobulin G (IgG) is transferred from the mother to the fetus, providing protection from disease in early infancy. Plasmodium falciparum infections may reduce maternofetal antibody transfer efficiency, but mechanisms remain unclear. METHODS: Mother-cord paired serum samples collected at delivery from Papua New Guinea (PNG) and the Thailand-Myanmar Border Area (TMBA) were tested for IgG1 and IgG3 to four P. falciparum antigens and measles antigen, as well as total serum IgG. Multivariable linear regression was conducted to assess the association of peripheral P. falciparum infection during pregnancy or placental P. falciparum infection assessed at delivery with maternofetal antibody transfer efficiency. Path analysis assessed the extent to which associations between P. falciparum infection and antibody transfer were mediated by gestational age at delivery or levels of maternal total serum IgG. RESULTS: Maternofetal antibody transfer efficiency of IgG1 and IgG3 was lower in PNG compared to TMBA (mean difference in cord antibody levels (controlling for maternal antibody levels) ranged from -0.88 to 0.09, median of -0.20 log2 units). Placental P. falciparum infections were associated with substantially lower maternofetal antibody transfer efficiency in PNG primigravid women (mean difference in cord antibody levels (controlling for maternal antibody levels) ranged from -0.62 to -0.10, median of -0.36 log2 units), but not multigravid women. The lower antibody transfer efficiency amongst primigravid women with placental infection was only partially mediated by gestational age at delivery (proportion indirect effect ranged from 0% to 18%), whereas no mediation effects of maternal total serum IgG were observed. DISCUSSION: Primigravid women may be at risk of impaired maternofetal antibody transport with placental P. falciparum infection. Direct effects of P. falciparum on the placenta, rather than earlier gestational age and elevated serum IgG, are likely responsible for the majority of the reduction in maternofetal antibody transfer efficiency with placental infection.

Optimal antimalarial dose regimens for chloroquine in pregnancy based on population pharmacokinetic modelling.

Despite extensive use and accumulated evidence of safety, there have been few pharmacokinetic studies from which appropriate chloroquine (CQ) dosing regimens could be developed specifically for pregnant women. Such optimised CQ-based regimens, used as treatment for acute malaria or as intermittent preventive treatment in pregnancy (IPTp), may have a valuable role if parasite CQ sensitivity returns following reduced drug pressure. In this study, population pharmacokinetic/pharmacodynamic modelling was used to simultaneously analyse plasma concentration-time data for CQ and its active metabolite desethylchloroquine (DCQ) in 44 non-pregnant and 45 pregnant Papua New Guinean women treated with CQ and sulfadoxine/pyrimethamine or azithromycin (AZM). Pregnancy was associated with 16% and 49% increases in CQ and DCQ clearance, respectively, as well as a 24% reduction in CQ relative bioavailability. Clearance of DCQ was 22% lower in those who received AZM in both groups. Simulations based on the final multicompartmental model demonstrated that a 33% CQ dose increase may be suitable for acute treatment for malaria in pregnancy as it resulted in equivalent exposure to that in non-pregnant women receiving recommended doses, whilst a double dose would likely be required for an effective duration of post-treatment prophylaxis when used as IPTp especially in areas of CQ resistance. The impact of co-administered AZM was clinically insignificant in simulations. The results of past/ongoing trials employing recommended adult doses of CQ-based regimens in pregnant women should be interpreted in light of these findings, and consideration should be given to using increased doses in future trials.

Risk factors for malaria and adverse birth outcomes in a prospective cohort of pregnant women resident in a high malaria transmission area of Papua New Guinea.

BACKGROUND: Low birth weight (LBW), anaemia and malaria are common in Papua New Guinean women. METHODS: To identify risk factors for LBW, anaemia and preterm delivery (PTD), pregnant women recruited into a cohort study in Madang, Papua New Guinea, were followed to delivery. RESULTS: Of 470 women enrolled, delivery data were available for 328 (69.7%). By microscopy, 34.4% (113/328) of women had malaria parasitaemia at enrolment and 12.5% (41/328) at delivery; at each time point, PCR detected sub-microscopic parasitaemia in substantially more. Most infections were with Plasmodium falciparum; the remainder being predominantly P. vivax. Anaemia and smoking were associated with lower birth weight, and LBW (16.7%; 51/305) and PTD (21.8%; 63/290) were common. Histopathologically diagnosed chronic placental malaria was associated with LBW (adjusted odds ratio [aOR] 3.3; p=0.048) and PTD (aOR 4.2; p=0.01). Lack of maternal education predisposed to PTD. Sub-microscopic parasitaemia at delivery appeared to increase the risk of LBW. Of the genetic polymorphisms, Southeast Asian ovalocytosis, α(+)-thalassaemia and complement receptor 1 (CR1) deficiency, a CR1 heterozygous genotype was associated with decreased risk of anaemia and substantial but non-significant effects were noted in other comparisons. CONCLUSIONS: In coastal Papua New Guinea, malaria and anaemia are important causes of adverse pregnancy outcomes.

High numbers of circulating pigmented polymorphonuclear neutrophils as a prognostic marker for decreased birth weight during malaria in pregnancy.

During gestational malaria, Plasmodium falciparum-infected erythrocytes can sequester within the placenta, contributing to poor pregnancy outcomes, especially low birth weight. In children and non-pregnant adults, pigmented leukocytes may serve as markers of sequestered parasite burden and predict clinical outcomes. Here, we investigated circulating pigmented leukocyte numbers as predictors of clinical outcomes in pregnant women presenting with malaria at enrolment. The number of circulating pigmented neutrophils at enrolment negatively correlated with birth weight (Rho=-25, P=.04), suggesting these cells may have a pathogenic role in, and could serve as prognostic markers for, malaria-associated low birth weight.

Does malaria affect placental development? Evidence from in vitro models.

BACKGROUND: Malaria in early pregnancy is difficult to study but has recently been associated with fetal growth restriction (FGR). The pathogenic mechanisms underlying malarial FGR are poorly characterized, but may include impaired placental development. We used in vitro methods that model migration and invasion of placental trophoblast into the uterine wall to investigate whether soluble factors released into maternal blood in malaria infection might impair placental development. Because trophoblast invasion is enhanced by a number of hormones and chemokines, and is inhibited by pro-inflammatory cytokines, many of which are dysregulated in malaria in pregnancy, we further compared concentrations of these factors in blood between malaria-infected and uninfected pregnancies. METHODOLOGY/PRINCIPAL FINDINGS: We measured trophoblast invasion, migration and viability in response to treatment with serum or plasma from two independent cohorts of Papua New Guinean women infected with Plasmodium falciparum or Plasmodium vivax in early pregnancy. Compared to uninfected women, serum and plasma from women with P. falciparum reduced trophoblast invasion (P = .06) and migration (P = .004). P. vivax infection did not alter trophoblast migration (P = .64). The P. falciparum-specific negative effect on placental development was independent of trophoblast viability, but associated with high-density infections. Serum from P. falciparum infected women tended to have lower levels of trophoblast invasion promoting hormones and factors and higher levels of invasion-inhibitory inflammatory factors. CONCLUSION/SIGNIFICANCE: We demonstrate that in vitro models of placental development can be adapted to indirectly study the impact of malaria in early pregnancy. These infections could result in impaired trophoblast invasion with reduced transformation of maternal spiral arteries due to maternal hormonal and inflammatory disturbances, which may contribute to FGR by limiting the delivery of maternal blood to the placenta. Future prevention strategies for malaria in pregnancy should include protection in the first half of pregnancy.

Placental malaria-associated inflammation disturbs the insulin-like growth factor axis of fetal growth regulation.

BACKGROUND: The pathogenetic mechanisms of fetal growth restriction associated with placental malaria are largely unknown. We sought to determine whether placental malaria and related inflammation were associated with disturbances in the insulin-like growth factor (IGF) axis, a major regulator of fetal growth. METHOD: We measured IGF-1 and IGF-2 concentrations in plasma from 88 mother-neonate pairs at delivery and IGF binding proteins 1 and 3 (IGFBP-1 and IGFBP-3, respectively) in cord plasma from a cohort of Papua New Guinean women with and without placental malaria. Messenger RNA levels of IGF-1, IGF-2, and the IGF receptors were measured in matched placental biopsy specimens. RESULTS: Compared with those for uninfected pregnancies, IGF-1 levels were reduced by 28% in plasma samples from women with placental Plasmodium falciparum infection and associated inflammation (P = .007) and by 25% in their neonates (P = .002). Levels of fetal IGFBP-1 were elevated in placental malaria with and without inflammation (P = .08 and P = .006, respectively) compared with uninfected controls. IGF-2 and IGFBP-3 plasma concentrations and placental IGF ligand and receptor messenger RNA transcript levels were similar across groups. CONCLUSION: Placental malaria-associated inflammation disturbs maternal and fetal levels of IGFs, which regulate fetal growth. This may be one mechanism by which placental malaria leads to fetal growth restriction.

Pharmacokinetic properties of azithromycin in pregnancy.

Azithromycin (AZI) is an azalide antibiotic with antimalarial activity that is considered safe in pregnancy. To assess its pharmacokinetic properties when administered as intermittent preventive treatment in pregnancy (IPTp), two 2-g doses were given 24 h apart to 31 pregnant and 29 age-matched nonpregnant Papua New Guinean women. All subjects also received single-dose sulfadoxine-pyrimethamine (SP) (1,500 mg or 75 mg) or chloroquine (450-mg base daily for 3 days). Blood samples were taken at 0, 1, 2, 3, 6, 12, 24, 32, 40, 48, and 72 h and on days 4, 5, 7, 10, and 14 for AZI assay by ultra-high-performance liquid chromatography-tandem mass spectrometry. The treatments were well tolerated. Using population pharmacokinetic modeling, a three-compartment model with zero-order followed by first-order absorption and no lag time provided the best fit. The areas under the plasma concentration-time curve (AUC(0-infinity)) (28.7 and 31.8 mg.h liter(-1) for pregnant and nonpregnant subjects, respectively) were consistent with the results of previous studies, but the estimated terminal elimination half-lives (78 and 77 h, respectively) were generally longer. The only significant relationship for a range of potential covariates, including malarial parasitemia, was with pregnancy, which accounted for an 86% increase in the volume of distribution of the central compartment relative to bioavailability without a significant change in the AUC(0-infinity). These data suggest that AZI can be combined with compounds with longer half-lives, such as SP, in combination IPTp without the need for dose adjustment.

Transfer of chloroquine and desethylchloroquine across the placenta and into milk in Melanesian mothers.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: The literature on placental and milk transfer of chloroquine and its major bioactive metabolite desethylchloroquine is sparse and incomplete. WHAT THIS STUDY ADDS: We have provided data on the transplacental transfer of chloroquine and desethylchloroquine in Melanesian women (n = 19), measured transfer of these drugs into breast milk (n = 16) and estimated absolute and relative infant doses for the breastfed infant. The data for desethylchloroquine are novel. In all three areas we have significantly increased both quantity and quality of the available database. AIMS: To investigate the transfer of chloroquine and its major bioactive metabolite desethylchloroquine across the placenta and into breast milk. METHODS: In Papua New Guinea, chloroquine (CQ; 25 mg base kg(-1)) is recommended for prophylaxis of malaria during pregnancy, and at the Alexishafen Health Centre women are routinely prescribed CQ at the time of delivery. Fetal-cord and maternal serum samples were collected at delivery (n = 19) and milk samples were collected from day 3 to day 17-21 after delivery (n = 16). CQ and its primary active metabolite desethylchloroquine (DECQ) were quantified by high-performance liquid chromatography. For both CQ and DECQ cord/maternal ratios (C/M) were calculated to characterize placental transfer, and infant exposure via milk was estimated by standard methods. RESULTS: The median (interquartile range) C/M was 1.1 (0.9, 1.6) for CQ and 1.2 (0.5, 1.8) for DECQ. The average concentration in milk over the time of sampling was 167 microg l(-1) (27, 340) for CQ and 54 microg l(-1) (22, 106) for DECQ. Estimated absolute and relative infant doses were 34 microg kg(-1) day(-1) (7, 50) and 15 microg kg(-1) day(-1) (4, 26), and 2.3% (0.5, 3.6) and 1.0% (0.4, 2.0) for CQ and DECQ (as CQ equivalents), respectively. CONCLUSION: Infant exposure to CQ and DECQ during pregnancy will be similar to that in the maternal circulation, and dependent on maternal dose and frequency. The median CQ + DECQ relative infant dose of 3.2% (as CQ equivalents) was low, confirming that use of CQ during lactation is compatible with breastfeeding.