Vulnerable newborn types: analysis of subnational, population-based birth cohorts for 541 285 live births in 23 countries, 2000-2021

OBJECTIVE

To examine prevalence of novel newborn types among 541 285 live births in 23 countries from 2000 to 2021.

DESIGN

Descriptive multi-country secondary data analysis.

SETTING

Subnational, population-based birth cohort studies (n = 45) in 23 low- and middle-income countries (LMICs) spanning 2000-2021.

POPULATION

Liveborn infants.

METHODS

Subnational, population-based studies with high-quality birth outcome data from LMICs were invited to join the Vulnerable Newborn Measurement Collaboration. We defined distinct newborn types using gestational age (preterm [PT], term [T]), birthweight for gestational age using INTERGROWTH-21st standards (small for gestational age [SGA], appropriate for gestational age [AGA] or large for gestational age [LGA]), and birthweight (low birthweight, LBW [<2500 g], nonLBW) as ten types (using all three outcomes), six types (by excluding the birthweight categorisation), and four types (by collapsing the AGA and LGA categories). We defined small types as those with at least one classification of LBW, PT or SGA. We presented study characteristics, participant characteristics, data missingness, and prevalence of newborn types by region and study.

RESULTS

Among 541 285 live births, 476 939 (88.1%) had non-missing and plausible values for gestational age, birthweight and sex required to construct the newborn types. The median prevalences of ten types across studies were T+AGA+nonLBW (58.0%), T+LGA+nonLBW (3.3%), T+AGA+LBW (0.5%), T+SGA+nonLBW (14.2%), T+SGA+LBW (7.1%), PT+LGA+nonLBW (1.6%), PT+LGA+LBW (0.2%), PT+AGA+nonLBW (3.7%), PT+AGA+LBW (3.6%) and PT+SGA+LBW (1.0%). The median prevalence of small types (six types, 37.6%) varied across studies and within regions and was higher in Southern Asia (52.4%) than in Sub-Saharan Africa (34.9%).

CONCLUSIONS

Further investigation is needed to describe the mortality risks associated with newborn types and understand the implications of this framework for local targeting of interventions to prevent adverse pregnancy outcomes in LMICs.

Prevalence and risk factors for Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis infection in pregnant women in Papua New Guinea

OBJECTIVE

To determine the prevalence of, and risk factors associated with, Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis infection in pregnant women in Madang, Papua New Guinea (PNG).

METHODS

A cross-sectional survey was conducted among 400 pregnant women presenting to antenatal clinics. Sociodemographic and behavioural data were collected and real-time PCR diagnostic methods were used to detect the presence of chlamydia, gonorrhoea and trichomonas in self-collected vaginal swabs. The relationships between symptoms, sociodemographic and behavioural factors and infection were assessed.

RESULTS

The prevalence of C. trachomatis was 11.1%, N. gonorrhoeae was 9.7% and T. vaginalis was 21.3%. One-third of women (33.7%) had at least one infection. The most common symptom was abdominal pain (48.0%), but only abnormal vaginal discharge was consistently associated with infection (p<0.001). Women diagnosed with vaginal discharge syndrome were more likely to have at least one treatable infection (50.0% (47/94)  vs 26.8% (68/254), p<0.001), yet 59.1% of women with infection would have been missed by the current clinically-based syndromic diagnosis. Risk factors included having a partner at perceived risk of infection, maternal extramarital intercourse, early sexual debut, lack of formal education, urban residence and smoking. 78.8% of women reported never using condoms.

CONCLUSIONS

The prevalences of T. vaginalis, C. trachomatis and N. gonorrhoeae were high among pregnant women in coastal PNG. The poor performance of clinically based syndromic diagnosis suggests that alternative strategies are urgently required to improve detection and reduce the burden of sexually transmitted infections and their associated adverse pregnancy outcomes in this population.

The impact of maternal malaria on newborns

BACKGROUND

Each year, malaria threatens 125 million pregnancies, and gestational malaria is responsible for up to 200,000 infant deaths in sub-Saharan Africa. With advancing knowledge of malaria in pregnancy and its impact on newborns, improved preventive and therapeutic interventions are possible.

METHODS

We reviewed and, by consensus, evaluated published literature relevant to malaria and newborns. Important findings are summarised.

RESULTS

Pregnant women are more likely than others to be inoculated with and infected by malaria parasites. Poor outcomes are particularly common in primigravid women and their offspring. The placenta is affected through cellular adhesion, cytokine production and mononuclear cell infiltrates. As a result, newborns may have low birthweight owing to intrauterine growth retardation or prematurity. Recent evidence suggests that a subset of these infants is also at higher risk of malaria infections later in life. Preventive strategies to improve maternal and fetal outcomes include intermittent preventive treatment and insecticide-treated bed nets. Asymptomatic malaria infection is not uncommon in newborns, and symptomatic disease occurs. Fever and death are possible during the early days of life, and presentation with a sepsis-like illness can occur during the 1st 2 months of life. Malaria-affected infants face higher than usual risks of infantile anaemia, subsequent malaria infection and death during the 1st year of life.

CONCLUSIONS

Malaria is common during pregnancy and can have serious consequences for neonatal health. Neonatal morbidity and mortality can be significantly reduced by proper implementation of insecticide-treated nets and intermittent preventive treatment.

An alternative agglutination assay to measure antibodies to variant surface antigens of Plasmodium falciparum-infected erythrocytes

Agglutination assays detect antibodies to variant parasite antigens expressed on the surface of Plasmodium falciparum-infected erythrocytes. Standard techniques require immediate analysis limiting the number of samples that can be processed simultaneously and preclude re-examination of slides. Fixed Giemsa-stained smears allow long-term storage and re-examination, without fluorescence microscopy.

Chondroitin sulphate A as an adherence receptor for Plasmodium falciparum-infected erythrocytes

Until recently, the sequestration of erythrocytes infected with Plasmodium falciparum has been thought to be due to one of a number of protein-protein interactions. In this article, Stephen Rogerson and Graham Brown summarize the emerging evidence that, in vitro, infected erythrocytes can also adhere to the glycosaminoglycan chondroitin sulphate A (CSA) expressed on the surface of cells and immobilized on plastic. In vivo, binding of infected erythrocytes to CSA could be crucial to the development of malarial infection of the placenta, and possibly to sequestration in the lung and brain. The consequences of this may include maternal morbidity and mortality, low birth weight in the infant, pulmonary oedema and cerebral malaria. They discuss the need to characterize the molecular basis of this interaction, and to investigate the possible therapeutic role of CSA in malaria. Chondroitin sulphates are nontoxic compounds already in use for other diseases in humans. Vaccines based on inhibiting this receptor-ligand interaction could also be appropriate.

Immune mimicry in malaria: Plasmodium falciparum secretes a functional histamine-releasing factor homolog in vitro and in vivo

The Plasmodium falciparum translationally controlled tumor protein (TCTP) is a homolog of the mammalian histamine-releasing factor (HRF), which causes histamine release from human basophils and IL-8 secretion from eosinophils. Histamine, IL-8, and eosinophils have been reported to be elevated in patients with malaria. This study was undertaken to determine whether malarial TCTP is found in the plasma of malaria-infected patients and to determine whether it has HRF biologic activity. Malarial TCTP was found in lightly infected human volunteers and in heavily infected Malawian children, but not in uninfected patients. Recombinant malarial TCTP, like HRF, stimulated histamine release from basophils and IL-8 secretion from eosinophils in vitro. Whereas malarial TCTP was less active than HRF, the concentrations that were effective in vitro could be achievable in vivo. These data suggest that malarial TCTP, present in human plasma during a malarial illness, may affect host immune responses in vivo.

Parasite adhesion and immune evasion in placental malaria

Parasite sequestration in the placenta is a key feature of infection by Plasmodium falciparum during pregnancy and is associated with severe adverse outcomes for both mother and baby. Here, James Beeson and colleagues draw together the findings of recent studies on parasite mechanisms that mediate this process. They review evidence for novel parasite variants that appear able to evade pre-existing immunity, for the adhesion of P. falciparum-infected erythrocytes to placental glycosaminoglycans (and the molecular basis of these parasite properties) and for the expression of var genes encoding the variant antigen and adhesive ligand P. falciparum-erythrocyte membrane protein 1 (PfEMP1).

Mapping of the region of complement receptor (CR) 1 required for Plasmodium falciparum rosetting and demonstration of the importance of CR1 in rosetting in field isolates

The malaria parasite Plasmodium falciparum induces a number of novel adhesion properties in the erythrocytes that it infects. One of these properties, the ability of infected erythrocytes to bind uninfected erythrocytes to form rosettes, is associated with severe malaria and may play a direct role in the pathogenesis of disease. Previous work has shown that erythrocytes deficient in complement receptor (CR) 1 (CR1, CD35; C3b/C4b receptor) have greatly reduced rosetting capacity, indicating an essential role for CR1 in rosette formation. Using deletion mutants and mAbs, we have localized the region of CR1 required for the formation of P. falciparum rosettes to the area of long homologous repeat regions B and C that also acts as the binding site for the activated complement component C3b. This result raises the possibility that C3b could be an intermediary in rosetting, bridging between the infected erythrocyte and CR1. We were able to exclude this hypothesis, however, as parasites grown in C3-deficient human serum formed rosettes normally. We have also shown in this report that rosettes can be reversed by mAb J3B11 that recognizes the C3b binding site of CR1. This rosette-reversing activity was demonstrated in a range of laboratory-adapted parasite strains and field isolates from Kenya and Malawi. Thus, we have mapped the region of CR1 required for rosetting and demonstrated that the CR1-dependent rosetting mechanism occurs commonly in P. falciparum isolates, and could therefore be a potential target for future therapeutic interventions to treat severe malaria.

Intermittent sulfadoxine-pyrimethamine in pregnancy: effectiveness against malaria morbidity in Blantyre, Malawi, in 1997-99

Plasmodium falciparum malaria in pregnancy predisposes to maternal and foetal morbidity. In 1993 Malawi adopted intermittent presumptive therapy with sulfadoxine-pyrimethamine (SP) as malaria prophylaxis for all pregnant women. To assess operational effectiveness of SP, we examined (in 1997-99) the relationship between number of doses of SP prescribed in antenatal clinic and indicators of malaria infection and morbidity at delivery, including peripheral and placental parasitaemia, maternal and neonatal anaemia, and birthweight. Among Malawian women delivering in a large urban hospital, SP prescription was associated with a decrease in placental malaria prevalence (from 31.9% with no SP prescription to 22.8% with > or = 2 doses SP) and density, decreased prevalence of low birthweight (from 23% in women not receiving SP to 10.3% in women given > or = 2 doses), and higher maternal haemoglobin concentrations. These effects were most marked in first and second pregnancies, in which malaria prevalence was highest. Maternal and cord blood malaria prevalence and mean cord blood haemoglobin concentrations did not differ with SP usage. Implementation of the SP administration policy was incomplete: 24% of women were not prescribed any SP, and only 30% were prescribed at least 2 doses as recommended. Intermittent presumptive treatment with SP is having a positive impact on some, but not all indicators of malaria infection and morbidity in Malawi. Improved implementation and continued surveillance are essential.

Anaemia in pregnancy in southern Malawi: prevalence and risk factors

OBJECTIVE

To determine prevalence of anaemia in pregnancy in southern Malawi, and to establish if an 'at risk' group can be identified for targeted intervention.

DESIGN

Prospective cross-sectional study.

SETTING

A semi-urban hospital and a rural health clinic in southern Malawi.

POPULATION

Pregnant women attending the antenatal clinic for their booking visit.

METHODS

Haemoglobin concentration (g/dL) measured from a capillary blood sample (fingerprick) by battery operated HemoCue machine.

RESULTS

In urban Blantyre 57% of women were anaemic by WHO standards (haemoglobin < 11.0 g/dL) and 3.6% were severely anaemic (haemoglobin < 7.0 g/dL). The prevalence was higher in the rural area; 72% and 4.0%, respectively. Primiparae were at slightly increased risk for overall anaemia and severe anaemia but the effect of targeting this group alone for interventions would mean at least 65% of anaemic women and over half of the women with severe anaemia would be excluded. When the effect of age was examined separate from gravidity, adolescents were not found to be at increased risk of anaemia. Anaemia was more prevalent in the wet season and in women who booked late for antenatal care.

CONCLUSION

The prevalence of anaemia in pregnancy in our population is unacceptably high and deserves more attention. Prophylaxis of all women rather than an 'at risk' group based on age or gravidity is recommended.

Malaria and anemia in antenatal women in Blantyre, Malawi: a twelve-month survey

Malaria and anemia are common in pregnant African women. We screened 4,764 Malawian women at first antenatal visits for malaria and anemia. A total of 42.7% had a malaria infection, which was more common and of higher density in primigravidae (prevalence = 47.3%, geometric mean = 332 parasites/microl) and teenagers (49.8%, 390/microl) than in multigravidae (40.4%, 214/microl) or older women (40.6%, 227/microl). However, 35% of gravida 3+ women were parasitemic. A total of 57.2% of the women was anemic (hemoglobin < 11 g/dl), with moderate anemia (7.0-8.9 g/dl) in 14.9% and severe anemia (< 7 g/dl) in 3.2%. Prevalences of malaria and anemia were highest in the rainy season. Women with moderate/severe anemia had higher parasite prevalences and densities than women with mild/no anemia. Logistic regression showed that age, season, and trimester of presentation were significantly associated with the prevalence of malaria, but gravidity was not. In this urban setting, age and season are more important than gravidity as predictors of malaria at first antenatal visit, and parasitemia is frequent in women of all gravidities.

Adhesion of Plasmodium falciparum-infected erythrocytes to hyaluronic acid in placental malaria

Infection with Plasmodium falciparum during pregnancy leads to the accumulation of parasite-infected erythrocytes in the placenta, and is associated with excess perinatal mortality, premature delivery and intrauterine growth retardation in the infant, as well as increased maternal mortality and morbidity. P. falciparum can adhere to specific receptors on host cells, an important virulence factor enabling parasites to accumulate in various organs. We report here that most P. falciparum isolates from infected placentae can bind to hyaluronic acid, a newly discovered receptor for parasite adhesion that is present on the placental lining. In laboratory isolates selected for specific high-level adhesion, binding to hyaluronic acid could be inhibited by dodecamer or larger oligosaccharide fragments or polysaccharides, treatment of immobilized receptor with hyaluronidase, or treatment of infected erythrocytes with trypsin. In vitro flow-based assays demonstrated that high levels of adhesion occurred at low wall shear stress, conditions thought to prevail in the placenta. Our findings indicate that adhesion to hyaluronic acid is involved in mediating placental parasite accumulation, thus changing the present understanding of the mechanisms of placental infection, with implications for the development of therapeutic and preventative interventions.

Plasmodium falciparum rosette formation is uncommon in isolates from pregnant women

We examined the formation of Plasmodium falciparum erythrocyte rosettes using parasite isolates from placental or peripheral blood of pregnant Malawian women and from peripheral blood of children. Five of 23 placental isolates, 23 of 38 maternal peripheral isolates, and 136 of 139 child peripheral isolates formed rosettes. Placental isolates formed fewer rosettes than maternal isolates (range, 0 to 7. 5% versus 0 to 33.5%; P = 0.002), and both formed fewer rosettes than isolates cultured from children (range, 0 to 56%; P < 0.0001). Rosette formation is common in infections of children but uncommon in pregnancy and rarely detected in placental isolates.

The placenta in malaria: mechanisms of infection, disease and foetal morbidity

There is still much to discover about the reasons for the increased susceptibility of pregnant women to malaria or the pathogenesis of placental malaria. More systematic and detailed examination of the placenta may help. In many ways, the placenta can be seen as the flight recorder of the pregnancy; by examining it carefully it should be possible to tell much about how smooth a 'flight' the mother and baby experienced. It is hoped that, by probing the secrets of this 'squishy black box', the causes of adverse effects in pregnancy are elucidated, and the safe 'travel' of babies and their mothers in the future is ensured. In this review, the features of parasite accumulation in the placenta, parasite adherence, and hormonal and inflammatory responses to placental malaria are discussed, focussing on infection with Plasmodium falciparum. The results of recent research indicating an interaction between HIV and malaria in pregnancy are summarized. Ten questions for basic researchers are posed. The answers may help direct future efforts to control malaria in pregnancy.

Cytoadherence characteristics of Plasmodium falciparum-infected erythrocytes from Malawian children with severe and uncomplicated malaria

Cytoadherence of Plasmodium falciparum-infected erythrocytes to the microvascular endothelium is believed to be a key factor in the development of cerebral malaria. Erythrocyte rosette formation has been correlated with malaria severity in studies from east and west Africa. We cultured fresh isolates from Malawian children with severe (n = 76) or uncomplicated (n = 79) malaria to pigmented trophozoite stage and examined rosette formation and adherence to CD36, intercellular adhesion molecule-1 (ICAM-1), chondroitin sulfate A (CSA), and thrombomodulin (TM). Most (126 of 148) isolates bound to CD36, and 76 of 136 bound to ICAM-1. Fewer bound to CSA (40 of 148) or TM (23 of 148). After controlling for parasitemia, there was an inverse association between binding to CD36 (P = 0.004) or ICAM-1 (P = 0.001) and disease severity. Parasites from children with severe malaria anemia bound least to CD36, whereas ICAM-1 binding was lowest in children with cerebral malaria. There was no difference in rosette formation between any of the groups. In Malawian children, there was no evidence of a positive association between adherence to any of the receptors examined and disease severity. The negative association found raises the possibility that adherence to certain receptors could instead be an indicator of a less pathogenic infection.

Plasmodium falciparum isolates from infected pregnant women and children are associated with distinct adhesive and antigenic properties

Plasmodium falciparum malaria during pregnancy is an important cause of maternal and infant morbidity and mortality. Accumulation of large numbers of P. falciparum-infected erythrocytes in the maternal blood spaces of the placenta may be mediated by adhesion of infected erythrocytes to molecules presented on the syncytiotrophoblast surface. In this study, isolates from placentas and peripheral blood of infected pregnant women and from children were tested for binding to purified receptors and for agglutination with adult sera. Results suggest that adhesion to chondroitin sulfate A may be involved in placental parasite sequestration in most cases, but other factors are also likely to be important. Agglutination assay results suggest that parasites infecting pregnant women are antigenically distinct from those common in childhood disease. The prevalence of agglutinating antibodies to pregnancy isolates was generally low, but it was highest in multigravidae who are likely to have had the greatest exposure.

The adhesion of Plasmodium falciparum-infected erythrocytes to chondroitin sulfate A is mediated by P. falciparum erythrocyte membrane protein 1

Chondroitin sulfate A (CSA) is an important receptor for the sequestration of Plasmodium falciparum in the placenta, but the parasite ligand involved in adhesion has not previously been identified. Here we report the identification of a var gene transcribed in association with binding to CSA and present evidence that the P. falciparum erythrocyte membrane protein 1 product of the gene is the parasite ligand mediating CSA binding. Description of this gene and the implication of P. falciparum erythrocyte membrane protein 1 as the parasite ligand paves the way to a more detailed understanding of the pathogenesis of placental infection and potential therapeutic strategies targeting the interaction.

The effect of Plasmodium falciparum malaria on HIV-1 RNA blood plasma concentration

OBJECTIVES

This study was undertaken to determine the relative effect of malaria infection on HIV concentration in blood plasma, and prospectively to monitor viral concentrations after antimalarial therapy.

DESIGN

A prospective, double cohort study was designed to compare the blood HIV-1 RNA concentrations of HIV-positive individuals with and without acute malaria illness. Subjects were followed for 4 weeks after successful malaria therapy, or for 4 weeks from enrollment (controls).

METHODS

Malawian adults with symptomatic Plasmodium falciparum parasitemia (malaria group) and asymptomatic, aparasitemic blood donors (control group) were tested for HIV-1 antibodies to identify appropriate study groups. The malaria group received antimalarial chemotherapy only and were followed with sequential blood films. In both groups, blood plasma HIV-1 RNA viral concentrations were determined at enrollment and again at 1, 2 and 4 weeks.

RESULTS

Forty-seven malaria patients and 42 blood donors were enrolled. At enrollment blood plasma HIV-1 RNA concentrations were approximately sevenfold higher in patients with malaria than in blood donors (medians 15.1 x 10(4) and 2.24 x 10(4) copies/ml, respectively, P = 0.0001). No significant changes in median HIV-1 concentrations occurred in the 21 blood donors followed to week 4 (P = 0.68). In the 27 subjects successfully treated for malaria who were followed to week 4, a reduction in plasma HIV-1 RNA was observed from a median of 19.1 x 10(4) RNA copies/ml at enrollment, to 12.0 x 10(4) copies/ml at week 4, (P = 0.02). Plasma HIV-1 concentrations remained higher in malaria patients than controls (median 12.0 x 10(4) compared with 4.17 x 10(4) copies/ml, P = 0.086).

CONCLUSIONS

HIV-1 blood viral burden is higher in patients with P. falciparum malaria than in controls and this viral burden can, in some patients, be partly reduced with antimalarial therapy.

Inhibition of binding of malaria-infected erythrocytes by a tetradecasaccharide fraction from chondroitin sulfate A

Adherence of parasite-infected erythrocytes (IEs) to the microvascular endothelium of various organs, a process known as sequestration, is a feature of Plasmodium falciparum malaria. This event is mediated by specific adhesive interactions between parasite proteins, expressed on the surface of IEs, and host molecules. P. falciparum IEs can bind to purified chondroitin sulfate A (CS-A), to the proteoglycan thrombomodulin through CS-A side chains, and to CS-A present on the surface of brain and lung endothelial cells and placental syncytiotrophoblasts. In order to identify structural characteristics of CS-A important for binding, oligosaccharide fragments ranging in size from 2 to 20 monosaccharide units were isolated from CS-A and CS-C, following controlled chondroitin lyase digestion, and used as competitive inhibitors of IE binding to immobilized ligands. Inhibition of binding to CS-A was highly dependent on molecular size: a CS-A tetradecasaccharide fraction was the minimum length able to almost completely inhibit binding. The effect was dose dependent and similar to that of the parent polysaccharide, and the same degree of inhibition was not found with the CS-C oligosaccharides. There was no effect on binding of IEs to other ligands, e.g., CD36 and intercellular adhesion molecule 1. Hexadeca- and octadecasaccharide fractions of CS-A were required for maximum inhibition of binding to thrombomodulin. Analyses of oligosaccharide fractions and polysaccharides by electrospray mass spectrometry and high-performance liquid chromatography suggest that the differences between the activities of CS-A and CS-C oligosaccharides can be attributed to differences in sulfate content and sulfation pattern and that iduronic acid is not involved in IE binding.

The age-specific prevalence of Plasmodium falciparum in migrants to Irian Jaya is not attributable to agglutinating antibody repertoire

Previous observations have shown that individuals migrating from a malaria free area to a malaria endemic region in North Eastern Irian Jaya quickly acquire anti-parasite immunity, in an age-dependent manner. Sera from migrants and long-term residents in this area were examined for their ability to agglutinate a range of Plasmodium falciparum isolates and to disrupt erythrocyte rosettes. Antibody responses to merozoite surface protein 2 (MSP2) and ring-infected erythrocyte surface antigen (RESA) were also determined. The range of isolates agglutinated by sera from the migrants approached that seen in long-term residents. No difference was found between migrant adults and children in the range of agglutinating antibody, size of agglutinates, nor disruption of rosettes. Anti-MSP2 and anti-RESA antibodies were the only factors examined which showed a correlation with age. We conclude that although antibody to parasite neoantigens expressed on the surface of infected erythrocytes may play a role in the acquisition of immunity, the humoral response to other P. falciparum antigens is more likely to account for the age-dependent prevalence of parasitaemia observed.

Plasmodium falciparum-infected erythrocytes adhere to the proteoglycan thrombomodulin in static and flow-based systems

Plasmodium falciparum-infected erythrocytes can bind to the glycosaminoglycan chondroitin sulfate A. In this paper, we demonstrate that thrombomodulin, a proteoglycan present on endothelial cells and placental syncytiotrophoblasts, supports binding of selected lines of P. falciparum-infected erythrocytes in both static and flow-based assays, and that adhesion is dependent on the presence of the chondroitin sulfate A chain of thrombomodulin. Chondroitinase treatment of thrombomodulin abolished binding, and free chondroitin sulfate A prevented it, whereas other soluble glycosaminoglycans had little or no effect. Soluble thrombomodulin (with, but not without, its chondroitin sulfate chain) inhibited binding at 40 micrograms/ml, but not at physiological concentrations. Parasitized erythrocytes bound to cells expressing thrombomodulin, including human umbilical vein endothelial cells and A549 cells, and binding was inhibited by free chondroitin sulfate A. Established binding to A549 cells or to immobilized thrombomodulin was substantially reversed by chondroitin sulfate A at 10 micrograms/ml. The chondroitin sulfate chain of thrombomodulin is a receptor for malaria-infected erythrocytes in static assays and under physiological flow.

Adhesion of malaria-infected red blood cells to chondroitin sulfate A under flow conditions

Adhesion of parasitized red blood cells (PRBCs) to microvascular endothelial cells (ECs) is a distinctive feature of Plasmodium falciparum malaria and is a central event in the development of life-threatening complications such as cerebral malaria. PRBCs adhere to several EC-expressed molecules in vitro, but the relative importance of these interactions in vivo remains unclear. Chondroitin sulfate A (CSA) is the most recent EC surface-associated molecule to be implicated in the adhesive process. Accordingly, we have studied adhesion of PRBCs to CSA in vitro using a parallel-plate flow chamber. Under controlled flow conditions, PRBCs adhered to CSA in a concentration-dependent manner at wall-shear stresses up to 0.2 Pa, a value that is within the physiological range for venules. Once adhered, PRBCs remained stationary (rather than rolling) and continued to remain stationary even when the wall-shear stress was raised to supravenular levels. The adhesive interaction was strong and a proportion of adherent PRBCs could withstand detachment at stresses up to 2.5 Pa. Soluble CSA at pharmacological concentrations prevented adhesion of flowing PRBCs in a concentration-dependent manner but failed to reverse established adhesion. Adhesion of PRBCs to CSA could contribute to the pathogenesis of malaria, and soluble CSA may have a useful therapeutic effect.

Cytoadherence characteristics of Plasmodium falciparum isolates from Thailand: evidence for chondroitin sulfate a as a cytoadherence receptor

The association between cytoadherence of Plasmodium falciparum-infected erythrocytes and the severity of malaria has been evaluated. In this study, we investigate adherence to C32 melanoma cells, CD36, intracellular adhesion molecule-1 (ICAM-1), thrombospondin (TSP), E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and chondroitin sulfate A (CSA) of 36 P. falciparum isolates from patients suffering from acute falciparum malaria. Adherence to purified adhesion molecules varied greatly among different parasite isolates. All isolates but one adhered to CD36, but none bound to E-selectin and VCAM-1 beyond control levels. Some P. falciparum isolates adhered to ICAM-1 and to CSA, a newly identified receptor for adherence. There was no correlation between in vitro binding to any one receptor and the patients' conditions. In addition, we investigated the characteristics of adherence to CSA and to C32 melanoma cells. Infected erythrocytes continued to adhere after trypsin digestion and soluble CSA inhibited adherence to C32 melanoma cells in a dose-dependent manner. The results imply a role for CSA in the natural infection of P. falciparum.

Disruption of erythrocyte rosettes and agglutination of erythrocytes infected with Plasmodium falciparum by the sera of Papua New Guineans

People living in areas endemic for Plasmodium falciparum develop humoral responses which may contribute to protection against clinical disease but the specificity of such protective antibody responses remains to be defined. Antibodies disrupting erythrocyte rosettes have been associated with protection against cerebral malaria, and antibodies agglutinating infected erythrocytes with reduced episodes of clinical disease. We have studied the capacity of serum from Papua New Guinean adults and children with a spectrum of malaria exposure, including children and adults at the time of clinical disease, to disrupt erythrocyte rosettes and cause agglutination of infected erythrocytes. Using a single parasite isolate, almost all sera from adults from highly endemic areas agglutinated infected erythrocytes, and the majority disrupted rosettes, in some cases at greater titres than hitherto described. There was a correlation between rosette disruption and agglutination in highly exposed adults. Rosette disrupting antibodies were equally frequent in children with cerebral and uncomplicated malaria. Antibodies causing rosette disruption were frequent only in adults with a long history of malarial exposure. Rosette disrupting antibodies do not appear to protect Papua New Guinean children or adults against cerebral malaria.

Chondroitin sulfate A is a cell surface receptor for Plasmodium falciparum-infected erythrocytes

Adherence of Plasmodium falciparum-infected erythrocytes to cerebral postcapillary venular endothelium is believed to be a critical step in the development of cerebral malaria. Some of the possible receptors mediating adherence have been identified, but the process of adherence in vivo is poorly understood. We investigated the role of carbohydrate ligands in adherence, and we identified chondroitin sulfate (CS) as a specific receptor for P. falciparum-infected erythrocytes. Parasitized cells bound to Chinese hamster ovary (CHO) cells and C32 melanoma cells in a chondroitin sulfate-dependent manner, whereas glycosylation mutants lacking chondroitin sulfate A (CSA) supported little or no binding. Chondroitinase treatment of wild-type CHO cells reduced binding by up to 90%. Soluble CSA inhibited binding to CHO cells by 99.2 +/- 0.2% at 10 mg/ml and by 72.5 +/- 3.8% at 1 mg/ml, whereas a range of other glycosaminoglycans such as heparan sulfate had no effect. Parasite lines selected for increased binding to CHO cells and most patient isolates bound specifically to immobilized CSA. We conclude that P. falciparum can express or expose proteins at the surface of the infected erythrocyte that mediate specific binding to CSA. This mechanism of adherence may contribute to the pathogenesis of P. falciparum malaria, but has wider implications as an example of an infectious agent with the capacity to bind specifically to cell-associated or immobilized CS.

Chemoprophylaxis and treatment of malaria

Prevention of malaria morbidity relies on the use of personal protection from mosquito bites, appropriate chemoprophylactic drugs, and early investigation of symptoms in returning travellers. Malaria chemoprophylaxis must be tailored to the individual patient's travel and personal needs, and no chemoprophylaxis is completely effective. Chloroquine alone is adequate for those areas with P vivax, or sensitive P falciparum but in most circumstances the choice will be between mefloquine and doxycycline. The specific area visited, the time spent there and the individual's medical history will help determine the final choice.

Sulfated glycoconjugates as disrupters of Plasmodium falciparum erythrocyte rosettes

Some strains of Plasmodium falciparum form erythrocyte rosettes that are believed to result from a lectin interaction between malaria-infected and uninfected erythrocytes. The sulfated glycoconjugate heparin and certain heparin derivatives have been observed to disrupt rosettes. To investigate this interaction further, we have studied the effects of four sulfated glycoconjugates on 15 fresh isolates of P. falciparum from Papua New Guinea. A broader range of sulfated glycoconjugates has been tested against a laboratory strain. A concentration of 1,000 micrograms/ml of dextran sulfate (molecular weight [MW] 500,000) was the most potent disrupter of rosettes. Fucoidan, heparin, and dextran sulfate (MW 5,000) were of decreasing effectiveness in 14 of 15 fresh isolates. The same relationship was true for the laboratory strain. Pentosan polysulfate and sulfatide also disrupted rosettes; chondroitin sulfates A, B, and C and keratan sulfate gave either minimal or no rosette disruption. Thus, some sulfated glycoconjugates are potent disrupters of P. falciparum erythrocyte rosettes. Sulfated glycoconjugates that are potent disrupters of P. falciparum rosettes may prove useful in identifying ligands involved in rosette formation.

Diversity of agglutinating phenotype, cytoadherence, and rosette-forming characteristics of Plasmodium falciparum isolates from Papua New Guinean children

The relationship between antigenic variation, cytoadherence, rosette formation, and the pathogenesis of malaria has led to great interest in the diversity of these properties in Plasmodium falciparum isolates from different communities. In this study, we extend previous investigations by delineating the spectrum of agglutinating phenotypes, adherence to C32 melanoma cells, human umbilical vein endothelial cells (HUVEC), CD36, and intracellular adhesion molecule-1 (ICAM-1), and rosette-forming ability of a group of 20 P. falciparum isolates from Papua New Guinean children. Agglutination phenotypes were determined by using both the children's convalescent serum and a panel of adult immune sera. The wide range of variant antigenic types in the community was demonstrated by the failure of the agglutination assays to identify any two isolates with the same agglutinating phenotype in this, the largest study of its kind. Comparison of agglutination profiles from fresh and cryopreserved isolates demonstrated the general acceptability of cryopreservation before testing, but cautioned that some isolates may undergo selection and phenotypic change during the process. Nineteen isolates were able to bind to at least one of the four ligands studied and showed marked variation in both avidity and specificity of binding. The purified proteins ICAM-1 and CD36 proved to be the most useful assay ligands for investigating field isolates, with 18 isolates binding to at least one protein and 14 to both. No correlation was found between the binding of isolates to any two ligands nor between the binding of a standardized inoculum and the level of the patient's presenting parasitemia. All isolates from the study group were found to form rosettes (at a mean rate of 14.6% of cultured trophozoites involved in rosettes). A lack of correlation between rosette formation and CD36 binding suggests that the previously reported role of CD36 as a rosette formation receptor may not be important for isolates from Papua New Guinea.

Autonomic neuropathy is common in human immunodeficiency virus infection

We prospectively evaluated autonomic nervous system function in 17 consecutive ambulant patients with HIV infection [mean age (S.D.) 34.5 (5.5) years] and 17 controls matched for sex and age [31.2 (7.4) years]. A questionnaire was administered, and neurological examination and standard bedside autonomic function tests were performed. Eleven of 17 HIV-infected individuals (64.7%) had symptoms suggestive of autonomic dysfunction, particularly urogenital problems. Thirteen of 17 (76.5%) had autonomic neuropathy (one or more abnormal tests), including nine of 11 symptomatic individuals. Only two controls had any autonomic symptoms, and all had normal tests. Autonomic dysfunction is common in those with HIV infection and AIDS.

The platelet count as a simple measure to distinguish inflammatory bowel disease from infective diarrhoea

A total of 212 adult patients with infective diarrhoea and 27 with inflammatory bowel disease (IBD), admitted consecutively to an infectious disease unit, were studied in order to determine whether clinical features and laboratory measurements performed on admission identified cases of IBD. Long-standing diarrhoea, blood in the faeces, anaemia, leucocytosis, thrombocytosis, raised ESR and a reduced concentration of serum albumin were more common in patients with IBD (P less than 0.05). The most striking difference was in the platelet count with 59% patients with IBD and 1.6% patients with infective diarrhoea having platelet counts greater than 450 x 10(9)/l. A raised platelet count in a patient admitted to hospital with 'acute gastro-enteritis' suggests IBD.

Hydrocortisone in chloramphenicol-treated severe typhoid fever in Papua New Guinea

We investigated the effect of hydrocortisone on mortality and complications in chloramphenicol-treated severe typhoid fever (STF) in Goroka, Papua New Guinea. Of 374 culture-positive patients, 146 formed a retrospective comparison group, of whom 41 had STF. Of 228 patients in the intervention group, 58 had STF. Patients without STF had low mortality (2.5%) with standard treatment. In the intervention group, hydrocortisone was used in two dosage schedules, 100 mg for 12 doses (23 patients) and 400 mg for 12 doses (23 patients). There was no difference in mortality between steroid-treated and comparison STF patients (44.8% versus 43.9%) or in complications, and we conclude that moderate doses of steroids are not beneficial in severe typhoid fever.

Acute gastroenteritis: the need to remember alternative diagnoses

Five hundred and ninety-four patients were consecutively admitted to an infectious disease unit over a 2-year period with a referral diagnosis of acute gastroenteritis or food poisoning. In 175 (29%) patients, gastrointestinal symptoms were associated with a condition other than gastrointestinal infection. Non-infective gastrointestinal disease was present in 90 patients, systemic infection in 50 and systemic disease in 35. Four illustrative case histories are presented to emphasize the need for a high index of suspicion if diseases such as malaria, septicaemia or appendicitis are not to be missed.

Reactive arthritis complicating group G streptococcal septicaemia

We describe a case of group G streptococcal septicaemia complicated by sterile polyarthritis and pericarditis. We suggest that this organism may cause a 'reactive arthritis' type of illness, and that this is in keeping with known properties of the organism. We note that our patient's clinical features fit the modified Jones criteria for the diagnosis of rheumatic fever.