The Santa Lucia strain of Plasmodium falciparum as a model for vaccine studies. I. Development in Aotus lemurinus griseimembra monkeys

The Santa Lucia strain of Plasmodium falciparum and the Aotus lemurinus griseimembra monkey are proposed as models for the testing of sporozoite vaccines and transmission-blocking vaccines. Approximately 85% of splenectomized monkeys were infected when fed upon by 10 or more heavily infected Anopheles freeborni mosquitoes. Sporozoite-induced infections in monkeys with or without previous infection with P. vivax readily infected mosquitoes, thus making them candidates for testing transmission-blocking vaccines.

Regulation of cyclin E transcription by E2Fs and retinoblastoma protein

Cyclin E is critical for the advance of cells through the G1 phase of their growth cycle. Transcription of the cyclin E gene is known to be cell cycle-dependent. We have shown previously that mRNA levels of cyclin E are regulated positively by mitogens and negatively by TGF-beta. Much circumstantial evidence implicates both E2F transcription factors and the retinoblastoma protein (pRB) in the control of cyclin E expression. However, the molecular basis of this control has remained unclear. We report here the cloning of the cyclin E promoter and the identification of several putative E2F binding sites within the promoter sequence. We have found that cell cycle regulation of cyclin E transcription is mediated by E2F binding sites present in the promoter. The activity of this promoter can be regulated negatively by pRB. Our results suggest the operation of a positive-feedback loop in late G1 that functions to ensure continued cyclin E expression and pRB inactivation.

Fasting serum triglycerides, free fatty acids, and malondialdehyde are increased in preeclampsia, are positively correlated, and decrease within 48 hours post partum

OBJECTIVE

We tested the hypothesis that serum free (nonesterified) fatty acid and triglyceride concentrations are increased in nulliparous women with preeclampsia relative to women with uncomplicated pregnancies and that these lipids decrease post partum, consistent with the known resolution of clinical symptoms. The relationships between serum concentrations of these lipids and the lipid peroxidation metabolite malondialdehyde were also examined.

STUDY DESIGN

Predelivery and 24 to 48 hour postpartum venous blood samples were collected from eight women with preeclampsia and nine women with uncomplicated pregnancies after an 8- to 10-hour fast. Sera were analyzed for concentrations of triglycerides, free fatty acids, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and malondialdehyde.

RESULTS

Antepartum serum triglyceride and free fatty acid concentrations were increased approximately twofold in women with preeclampsia relative to uncomplicated pregnancies (p <0.02 and 0.004, respectively). Total, high-density lipoprotein, and low-density lipoprotein cholesterol concentrations did not differ between groups. Concentrations of all lipids decreased significantly in both groups within 48 hours post partum. However, triglyceride and free fatty acid concentrations remained higher in women with preeclampsia (p<0.006, both variables). Triglyceride and free fatty acid concentrations correlated positively, both ante partum (R2 0.42, p<0.01) and post partum (R2 0.39, p<0.02). Antepartum concentrations of malondialdehyde were 50% higher in women with preeclampsia (p<0.01) and decreased post partum (p <0.02) but did not decrease in controls (p = 0.07). Antepartum serum triglycerides and free fatty acids correlated positively with malondialdehyde concentrations (R2 0.38, p <0.02, both cases).

CONCLUSION

Triglycerides and free fatty acids, but not cholesterol, are increased in preeclampsia and correlate with the lipid peroxidation metabolite malondialdehyde. We speculate that these interactions may contribute to endothelial cell dysfunction in preeclampsia.

Urine but not plasma nitric oxide metabolites are decreased in women with preeclampsia

OBJECTIVE

Nitric oxide is a potent vasorelaxant produced by endothelial cells. We tested the hypothesis that urinary and perhaps plasma nitric oxide metabolites would be reduced in women with preeclampsia.

STUDY DESIGN

Plasma and urine from 14 women meeting strict clinical criteria for the diagnosis of preeclampsia and 20 normal nulliparous women were assayed for the stable metabolites of nitric oxide, nitrate and nitrite.

RESULT

There was no significant difference of plasma concentrations of nitrate and nitrite between women with preeclampsia and women with normal pregnancies (32.7 +/- 3.1 vs 25.8 +/- 2.4 micromol/L). Plasma creatinine levels were elevated in women with preeclampsia (0.85 +/- 0.09 vs 0.66 +/- 0.02 mg/dl, p<0.01), indicating a reduced glomerular filtration rate. Urine concentrations of nitrate and nitrite normalized by creatinine excretion were significantly lower in women with preeclampsia compared with normal pregnant women (0.37 +/- 0.06 vs 0.69 +/- 0.11 micromol of nitrite per milligram creatinine, p. <0.05).

CONCLUSIONS

Our study using concomitant measurement of plasma and urine nitrate and nitrite suggests a reduced production of nitric oxide in women with preeclampsia compared with normal pregnant women.

The length of the cervix and the risk of spontaneous premature delivery. National Institute of Child Health and Human Development Maternal Fetal Medicine Unit Network

BACKGROUND

The role of the cervix in the pathogenesis of premature delivery is controversial. In a prospective, multicenter study of pregnant women, we used vaginal ultrasonography to measure the length of the cervix; we also documented the incidence of spontaneous delivery before 35 weeks' gestation.

METHODS

At 10 university-affiliated prenatal clinics, we performed vaginal ultrasonography at approximately 24 and 28 weeks of gestation in women with singleton pregnancies. We then assessed the relation between the length of the cervix and the risk of spontaneous preterm delivery.

RESULTS

We examined 2915 women at approximately 24 weeks of gestation and 2531 of these women again at approximately 28 weeks. Spontaneous preterm delivery (at less than 35 weeks) occurred in 126 of the women (4.3 percent) examined at 24 weeks. The length of the cervix was normally distributed at 24 and 28 weeks (mean [+/- SD], 35.2 +/- 8.3 mm and 33.7 +/- 8.5 mm, respectively). The relative risk of preterm delivery increased as the length of the cervix decreased. When women with shorter cervixes at 24 weeks were compared with women with values above the 75th percentile, the relative risks of preterm delivery among the women with shorter cervixes were as follows: 1.98 for cervical lengths at or below the 75th percentile (40 mm), 2.35 for lengths at or below the 50th percentile (35 mm), 3.79 for lengths at or below the 25th percentile (30 mm), 6.19 for lengths at or below the 10th percentile (26 mm), 9.49 for lengths at or below the 5th percentile (22 mm), and 13.99 for lengths at or below the 1st percentile (13 mm) (P < 0.001 for values at or below the 50th percentile; P = 0.008 for values at or below the 75th percentile). For the lengths measured at 28 weeks, the corresponding relative risks were 2.80, 3.52, 5.39, 9.57, 13.88, and 24.94 (P < 0.001 for values at or below the 50th percentile; P = 0.003 for values at the 75th percentile).

CONCLUSIONS

The risk of spontaneous preterm delivery is increased in women who are found to have a short cervix by vaginal ultrasonography during pregnancy.

Mechanical stress eliminates the effects of plasma from patients with preeclampsia on endothelial cells

OBJECTIVE

Our purpose was to determine whether mechanical deformation alters in vitro effects of plasma from patients with preeclampsia on endothelial cell function to produce a paradigm similar to the in vivo disease state.

STUDY DESIGN

The effects of 2% plasma from 12 patients with preeclampsia and 12 normal pregnant women on prostacyclin, nitric oxide, and endothelin production by cultured endothelial cells were measured in the presence or absence of cyclic stretch and laminar shear stress.

RESULTS

In the absence of mechanical stress plasma from patients with preeclampsia resulted in greater prostacyclin and nitric oxide production (but no change in endothelin production) compared with plasma from normal pregnant women. Cyclic stretch did not affect prostacyclin or endothelin production but produced similar increases in nitric oxide production in cells exposed to plasma from the two groups. Shear stress markedly increased prostacyclin and nitric oxide production (but did not alter endothelin production). In the presence of shear stress there were no differences in production rates of nitric oxide or prostacyclin between cells exposed to plasma from the two groups.

CONCLUSION

Shear stress alters the effects of plasma on endothelial cells. This is an important caveat in the interpretation of previous static in vitro culture studies and may partially explain the dichotomy between in vitro studies and in vivo findings in preeclampsia.

Plasma of preeclamptic women stimulates and then inhibits endothelial prostacyclin

We propose that the dichotomy between the in vivo reduction in intravascular prostacyclin production that occurs in preeclampsia and the in vitro stimulatory effect of plasma from preeclamptic patients on endothelial cell prostacyclin production is due to differential effects of chronic versus acute exposure to the plasma. We studied the acute versus chronic effects of 2% plasma from healthy pregnant and preeclamptic subjects by measuring endothelial prostacyclin production at different time periods after exposure to plasma. To determine whether such effects were specific to prostacyclin, we also measured prostaglandin E2 production. To determine whether chronic changes in prostacyclin production resulted from altered cellular responsiveness, we stimulated cells that had been exposed to plasma for 72 hours with arachidonic acid and measured prostaglandin production. Preliminary characterization of the plasma factor or factors responsible for alterations in prostaglandin production was performed. After 24 hours cells exposed to plasma from preeclamptic women produced more prostacyclin and prostaglandin E2 than cells exposed to plasma from healthy pregnant women. In contrast, after 72 hours exposure to plasma from preeclamptic women resulted in less endothelial cell prostacyclin production than exposure to plasma from healthy pregnant women, but there were no such differences in prostaglandin E2 production. Cells that had been exposed to plasma from preeclamptic women for 72 hours produced less prostacyclin but the same quantity of prostaglandin E2 after stimulation with arachidonic acid than cells exposed to plasma from healthy pregnant women. The plasma factor or factors responsible for altered prostacyclin production were sensitive to heat, acid, and proteases. In contrast to acute exposure, chronic exposure to plasma from preeclamptic women alters endothelial cells to result in decreased prostacyclin production, an observation consistent with in vivo findings.

Hyperuricemia and xanthine oxidase in preeclampsia, revisited

Hyperuricemia is associated with the severity of preeclampsia and with fetal outcome. Traditionally the high uric acid concentration in preeclampsia has been attributed soley to renal dysfunction. Preeclampsia is also characterized by increased free radical formation and elevated oxidative stress. Xanthine dehydrogenase/oxidase produces uric acid. Xanthine dehydrogenase/oxidase is present as two isoforms in vivo. Uric acid production is coupled with formation of reactive oxygen species when the enzyme is in the oxidase form. Several factors can increase the holoenzyme activity and the conversion of xanthine dehydrogenase/oxidase to its oxidase form. These factors include hypoxia-reperfusion, cytokines, and increased substrate availability (xanthine and hypoxanthine). Preeclampsia is characterized by hyperuricemia and signs of increased formation of reactive oxygen species and decreased levels of antioxidants. Preeclampsia is also characterized by shallow implantation, producing a relatively hypoxic maternal-fetal interface, and increased turnover of trophoblast tissue, which can result in higher xanthine and hypoxanthine concentrations and higher levels of circulating cytokines. These mechanisms can lead to increased production of uric acid and free radicals and contribute to the hyperuricemia and increased oxidative stress present in preeclampsia.

Long-term use of permethrin-impregnated nets does not increase Anopheles gambiae permethrin tolerance

Previous use of permethrin-impregnated bednets (mosquito nets) and curtains in four Kenyan villages for one year, 1990-91, raised the permethrin LT50 of Anopheles gambiae to 2.4-fold above its baseline value, designated permethrin tolerance (PT), as measured by exposure to 0.25% permethrin-impregnated papers in W.H.O. test-kits. During 1992-93, with ongoing use of permethrin-impregnated nets and curtains, PT regressed slightly compared with the contemporary susceptibility level of An.gambiae from non-intervention villages, to 1.8-fold in 1992 and only 1.6-fold in 1993. Thus the selection pressure of impregnated nets for PT in An.gambiae appears to be minimal in our study villages, although the impact of permethrin was demonstrated by a significantly lower parous-rate of An.gambiae females in the intervention (63-66%) than in non-intervention (79%) villages, and by reduced malaria transmission (reported elsewhere). In a selected stock of An.gambiae from the study area, PT did not affect the susceptibility to deltamethrin, fenitrothion, propoxur or DDT. Bioassays described herein provide easy procedures for field-monitoring of mosquito susceptibility/tolerance/resistance to insecticides used for net impregnation in operational programmes.

Preeclampsia: not simply pregnancy-induced hypertension

Once classified as a seizure disorder and later as a hypertensive condition, preeclampsia is actually a multisystem disease. It remains a leading cause of maternal and neonatal morbidity. Clinical challenges include identifying patients who are at risk of serious complications and deciding whether it is safer for the fetus to be delivered or to remain in the uterus.

Elevated serum levels of vascular endothelial growth factor in patients with preeclampsia

OBJECTIVE

To determine whether altered levels of vascular endothelial growth factor (VEGF) may be implicated in the pathogenesis of preeclampsia, and whether VEGF mediates the endothelial cell activation that is involved in the pathogenesis of the clinical syndrome.

METHODS

In a cross-sectional study, maternal serum samples in late pregnancy (at the time of clinical disease) were collected from 78 nulliparous women. These subjects were subdivided into those with preeclampsia (n = 27), nonproteinuric pregnancy-induced hypertension (n = 15), and normal pregnant women (n = 36). In a nested case-control study, in addition to samples taken before delivery, samples were obtained in early pregnancy (before clinical disease) and 24-48 hours postpartum from 12 of the patients with preeclampsia, 12 of those with nonproteinuric pregnancy-induced hypertension, and 12 of the normal pregnant subjects. Umbilical cord blood was sampled from 14 of the preeclamptic and 16 of the normal pregnant subjects. We measured VEGF levels in all samples using an immunofluorometric assay.

RESULTS

In most samples collected before delivery, VEGF levels were below the lower limit of detection. However, the proportion of detectable levels was higher in the preeclampsia group (seven of 27) than in the normotensive group (one of 36, P < .05). The proportion in the nonproteinuric pregnancy-induced hypertension group (two of 15) did not differ significantly from the other groups. Levels in the patients with preeclampsia were not elevated before clinical disease. Levels of VEGF in umbilical blood samples were higher than in maternal venous blood, although there were no significant differences between groups.

CONCLUSION

Serum VEGF levels were elevated in patients with preeclampsia, which suggests that the growth factor has a role in the endothelial cell activation that occurs in the disease.

Sertraline treatment of comorbid posttraumatic stress disorder and alcohol dependence

BACKGROUND

Posttraumatic stress disorder (PTSD) often co-occurs with alcohol dependence, yet little is known about treatment of this comorbidity. The serotonin selective reuptake inhibitors have been shown preliminarily to be effective in decreasing symptoms of PTSD but have not been studied in individuals with comorbid alcohol dependence. This is of particular interest as the SSRIs also have a modest effect in decreasing alcohol consumption.

METHOD

In this preliminary trial, nine subjects with comorbid PTSD and alcohol dependence were treated in an open-label trial with sertraline for a 12-week period. Symptoms of PTSD and depression were monitored monthly with the Impact of Event Scale and the Hamilton Rating Scale for Depression (HAM-D). Alcohol consumption was monitored by a self-report instrument (Time-Line Follow-Back).

RESULTS

There were significant decreases in all three symptom clusters of PTSD measured by overall PTSD symptom scores (p < or = .001) and in HAM-D scores (p < or = .001) during the follow-up period. Days of abstinence increased and average number of drinks decreased during the follow-up period. Four subjects claimed total abstinence during the follow-up period.

CONCLUSION

While limited by small sample size and the open-label, nonblinded study design, this study suggests that sertraline may be useful in the treatment of PTSD complicated by alcoholism. The medication was well tolerated and subjects showed improvement in PTSD symptoms as well as decreased alcohol consumption. A controlled trial of sertraline in this population would be of interest.

Malaria surveillance--United States, 1992

PROBLEM/CONDITION

Malaria is caused by one of four species of Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, or P. malariae) and is transmitted by the bite of an infective female Anopheles sp. mosquito. Most malaria cases in the United States occur among persons who have traveled to areas that have ongoing transmission. However, cases are transmitted occasionally through exposure to infected blood products, by congenital transmission, or by local mosquito-borne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to guide prevention recommendations.

REPORTING PERIOD COVERED

Cases with onset of illness during 1992.

DESCRIPTION OF SYSTEM

Malaria cases were identified at the local level (i.e., by healthcare providers or through laboratory-based surveillance). All suspected cases were confirmed by slide diagnosis and then reported to the respective state health department and to CDC.

RESULTS

CDC received reports of 910 cases of malaria that had onset of symptoms during 1992 among persons in the United States and its territories. In comparison, 1,046 cases were reported for 1991, representing a decrease of 13% in 1992. P. vivax, P. falciparum, P. malariae, and P. ovale were identified in 51%, 33%, 4%, and 3% of cases, respectively. The species was not identified in the remaining 9% of cases. The number of reported malaria cases that had been acquired in Africa by U.S. civilians decreased 38%, primarily because the number of P. falciparum cases declined. Of U.S. civilians whose illnesses were diagnosed as malaria, 81% had not taken a chemoprophylactic regimen recommended by CDC. Seven patients had acquired their infections in the United States. Seven deaths were attributed to malaria.

INTERPRETATION

The decrease in the number of P. falciparum cases in U.S. civilians could have resulted from a change in travel patterns, reporting errors, or increased use of more effective chemoprophylaxis regimens.

ACTIONS TAKEN

Additional information was obtained concerning the seven fatal cases and the seven cases acquired in the United States. Malaria prevention guidelines were updated and disseminated to health-care providers. Persons traveling to a malaria-endemic area should take the recommended chemoprophylaxis regimen and use personal protection measures to prevent mosquito bites. Any person who has been to a malarious area and who subsequently develops a fever or influenza-like symptoms should seek medical care, which should include a blood smear for malaria. The disease can be fatal if not diagnosed and treated at an early stage of infection. Recommendations concerning prevention and treatment of malaria can be obtained from CDC.

NOS expression is increased in endothelial cells exposed to plasma from women with preeclampsia

Endothelial cell function is proposed to be altered by a factor(s) in the maternal circulation of women with the pregnancy disorder preeclampsia. Our initial hypothesis was that in preeclampsia, such factor(s) would reduce synthesis of nitric oxide (NO) by endothelial cells. However, we previously observed increased NO synthase activity in endothelial cells exposed to plasma from preeclamptic women. This study tested whether exposing cells to plasma from preeclamptic women increased transcription and/or translation of endothelial NO synthase. Cultured bovine coronary microvascular endothelial cells were exposed to 2% plasma from patients with preeclampsia and patients with uncomplicated pregnancies. Nitrite production was greater in endothelial cells exposed to plasma from preeclamptic women (8.97 +/- 0.54 vs. 6.39 +/- 0.59 nmol nitrites.10(6) cells-1 x 24 h-1; P < 0.05). Similarly, endothelial NO synthase mass as measured by Western immunoblotting was significantly increased (20,980 +/- 1,406 vs. 15,047 +/- 1,003 absorbancy units; P < 0.02). There was no detectable difference in mRNA for endothelial NO synthase. However, actinomycin (3 micrograms/ml), a transcription inhibitor, significantly decreased nitrite production only in cells exposed to plasma from preeclamptic women (5.28 +/- 0.52 vs. 3.56 +/- 0.36 nmol.10(6) cells-1 x 24 h-1, P < 0.05). These findings indicate a regulation of the "constitutive" isoform of NO synthase by factor(s) in the blood of preeclamptic women, which may have significance in this pathological condition of pregnancy.

TEL and KIP1 define the smallest region of deletions on 12p13 in hematopoietic malignancies

Unbalanced translocations as well as interstitial deletions of the short arm of chromosome 12 [del(12p)] are found as recurring chromosomal changes in a broad spectrum of hematopoietic malignancies. These changes result in the hemizygous deletion of genetic material from 12p. We mapped a yeast artificial chromosome containing the TEL gene, a cosmid contig containing part of TEL and a P1 contig containing the KIP1 gene to 12p13. These probes were used for fluorescence in situ hybridization to analyze samples from 47 patients with various hematologic malignancies who had unbalanced translocations (25 patients) leading to loss of 12p or deletions (22 patients) involving 12p13. The patients had acute lymphoblastic leukemia (8 cases), myelodysplastic syndrome (MDS; 11 cases), acute myeloid leukemia (AML; 10 cases), myeloproliferative disorders (4 cases), therapy-related MDS or AML (7 cases), non-Hodgkin's lymphoma (2 cases), and other hematopoietic malignancies (5 cases). All three probes were hemizygously detected in 26 cases and were completely retained in only 9 cases. In 12 cases probes for one of the two genes were deleted, allowing us to map the smallest region of overlap of these deletions to a small genomic region that is bordered on the telomeric side by the TEL gene and on the centromeric side by KIP1. The genomic distance between TEL and KIP1 is estimated to be about 1 to 2 Mbp.

Plasma from women with preeclampsia increases endothelial cell nitric oxide production

In preeclampsia, a factor in the maternal circulation alters endothelial function via a reduction in nitric oxide synthesis. We measured the in vitro effects of 2% plasma from women with preeclampsia, compared with 2% plasma from normotensive pregnant women, on cultured endothelial cell nitrite production and nitric oxide synthase activity. On finding differential effects, we measured the effects on cellular viability (assessed by lactate dehydrogenase levels) and performed a time course study. Endothelial cell nitrite production was found to be higher after exposure to plasma from the preeclamptic group than the normotensive pregnant group. The effects of long-term exposure (120 hours) were similar to those of short-term exposure (24 hours). In addition, nitric oxide synthase activity was significantly greater after exposure to preeclamptic plasma than after exposure to normotensive pregnant plasma. No differential effect on cellular viability was found. Contrary to our hypothesis, exposure of endothelial cells to preeclamptic plasma resulted in increased nitric oxide production and nitric oxide synthase activity.

Mitogenic effect of basic fibroblast growth factor and estradiol on cultured human myometrial and leiomyoma cells

OBJECTIVE

We compared the mitogenic effect of basic fibroblast growth factor with and without estradiol on myometrial and leiomyometrial cells.

STUDY DESIGN

The mitogenic effect of basic fibroblast growth factor on myometrial cells was measured by thymidine incorporation and cell count. The mitogenic effect of basic fibroblast growth factor with and without estradiol as measured by thymidine incorporation was compared between myometrial and leiomyometrial cells.

RESULTS

Both human myometrial and leiomyometrial cells showed significant (p = 0.004 and p = 0.001, respectively), dose-dependent incorporation of thymidine in response to basic fibroblast growth factor. Leiomyometrial cells showed significantly (p = 0.04) less thymidine incorporation compared with matched normal myometrial cells. The addition of estradiol with basic fibroblast growth factor did not result in a further increase in thymidine incorporation.

CONCLUSIONS

Both myometrial and leiomyometrial cells respond to basic fibroblast growth factor with increased thymidine incorporation; however leiomyometrial cells are less responsive than are matched normal myometrial cells. The addition of estradiol is not synergistic with basic fibroblast growth factor.

Nitric oxide produced by endothelial cells increases production of eicosanoids through activation of prostaglandin H synthase

The endothelium serves many functional roles, including the modulation of vascular smooth muscle tone through the release of vasoactive agents such as nitric oxide (NO) and the eicosanoids. We proposed that NO produced by endothelial cells would increase the production of eicosanoids through enhanced expression and/or activation of prostaglandin H synthase. NO and eicosanoid synthesis were stimulated in a bovine coronary microvessel endothelial cell line with the calcium ionophore A23187 (1 mumol/L). Our data demonstrated the following: (1) A23187 stimulated NO synthesis along with prostacyclin and thromboxane production. (2) Inhibition of NO synthesis with NG-nitro-L-arginine methyl ester (0.1 mmol/L) significantly diminished both prostacyclin and thromboxane production. (3) Cells incubated with hemoglobin (2 micrograms/mL), which inactivates NO, decreased A23187-stimulated prostacyclin production, whereas cells incubated with superoxide dismutase (20 U/mL), which protects NO from superoxide anions, enhanced prostacyclin production. (4) Exogenous NO stimulated prostacyclin production. (5) The interaction of NO with prostacyclin persisted in the presence of excess exogenous arachidonic acid (100 mumol/L). (6) Cyclooxygenase activity in cell lysates increased in the first hour of NO stimulation. (7) NO stimulation of prostacyclin occurred within 1 hour and continued for 8 hours. (8) Neither constitutive nor inducible prostaglandin H synthase enzyme expression was altered by NO. (9) Cycloheximide (10 mumol/L) had no effect on A23187 stimulation of prostacyclin production. (10) Exogenous cGMP (10 mumol/L) or a phosphodiesterase inhibitor (1 mmol/L) did not affect prostacyclin production. These data indicate that stimulating synthesis of endogenous NO in cultured endothelial cells increased eicosanoid production through activation of prostaglandin H synthase.

Antibodies to a Plasmodium falciparum blood-stage antigen as a tool for predicting the protection levels of two malaria-exposed populations

To evaluate the ability of antibodies to Plasmodium falciparum ring-infected erythrocyte surface antigen (Pf155/RESA) epitopes to discriminate between individuals well protected or poorly protected against malaria, a receiver operating characteristic analysis was performed in two populations living in Madagascar and Malawi. The definition of protection was based on longitudinal measurements of clinical malarial attacks during the season of high malaria transmission in the Madagascar study, and on a cross-sectional measurement of parasitemia in the Malawi study. Antibodies to peptides reproducing the 4-mer, 8-mer, and 11-mer of the Pf155/RESA were tested for their reactivities using the Falcon assay screening test-enzyme-linked immunosorbent assay. Maximal detection of poorly protected individuals (specificity = 100%) corresponded to high cutoff antibody titers (range = 1.65-3.0 optical density [OD] units in the Madagascar study and 0.67-1.42 OD units in the Malawi study) and a sensitivity less than 50%. For a given sensitivity of 50%, specificity ranged from 55% to 62% in the Madagascar study, and from 67% to 94% in the Malawi study. The antibody cutoff titers corresponding to minimal misclassification rates ranged from 0.24 to 1.73 OD units in the Madagascar study and from 0.15 to 0.55 OD units in the Malawi study. For each antibody, the highest detectability value as measured by the area under the curve was obtained for anti-R11 in the Malawi study (0.838). In demonstrating such qualities, antibodies to Pf155/RESA epitopes could be used for screening poorly protected populations in which malaria control programs have to be implemented.