Anti-PfGARP activates programmed cell death of parasites and reduces severe malaria.

Malaria caused by Plasmodium falciparum remains the leading single-agent cause of mortality in children1, yet the promise of an effective vaccine has not been fulfilled. Here, using our previously described differential screening method to analyse the proteome of blood-stage P. falciparum parasites2, we identify P. falciparum glutamic-acid-rich protein (PfGARP) as a parasite antigen that is recognized by antibodies in the plasma of children who are relatively resistant-but not those who are susceptible-to malaria caused by P. falciparum. PfGARP is a parasite antigen of 80 kDa that is expressed on the exofacial surface of erythrocytes infected by early-to-late-trophozoite-stage parasites. We demonstrate that antibodies against PfGARP kill trophozoite-infected erythrocytes in culture by inducing programmed cell death in the parasites, and that vaccinating non-human primates with PfGARP partially protects against a challenge with P. falciparum. Furthermore, our longitudinal cohort studies showed that, compared to individuals who had naturally occurring anti-PfGARP antibodies, Tanzanian children without anti-PfGARP antibodies had a 2.5-fold-higher risk of severe malaria and Kenyan adolescents and adults without these antibodies had a twofold-higher parasite density. By killing trophozoite-infected erythrocytes, PfGARP could synergize with other vaccines that target parasite invasion of hepatocytes or the invasion of and egress from erythrocytes.

Antibodies to Helminth Defense Molecule-1 are associated with inflammation, organomegaly, and decreased nutritional status in schistosomiasis japonica.

Immunomodulation enhances parasite fitness by reducing inflammation-induced morbidity in the mammalian host, as well as by attenuating parasite-targeting immune responses. Using a whole proteome differential screening method, we identified Schistosoma japonicum Helminth Defense Molecule (SjHDM-1) as a target of antibodies expressed by S. japonicum resistant, but not susceptible, individuals. In a longitudinal cohort study (N=644) conducted in a S. japonicum endemic region of the Philippines, antibody levels to SjHDM-1 did not predict resistance to reinfection but were associated with increased measures of inflammation. Individuals with high levels of anti-SjHDM-1 IgG had higher levels of C-reactive protein compared to individuals with low anti-SjHDM-1. High anti-SjHDM-1 IgG responses were also associated with reduced biomarkers of nutritional status (albumin), as well as decreased anthropometric measures of nutritional status (WAZ and HAZ) and increased measures of hepatomegaly. Our results suggest that anti-SjHDM-1 responses inhibit the immunomodulatory function of SjHDM-1, resulting in increased morbidity.

Whole-Proteome Differential Screening Identifies Novel Vaccine Candidates for Schistosomiasis japonica.

Schistosomiasis remains a leading cause of chronic morbidity in endemic regions despite decades of widespread mass chemotherapy with praziquantel. Using our whole proteome differential screening approach, and plasma and epidemiologic data from a longitudinal cohort of individuals living in a Schistosoma japonicum-endemic region of the Philippines, we interrogated the parasite proteome to identify novel vaccine candidates for Schistosoma japonicum. We identified 16 parasite genes which encoded proteins that were recognized by immunoglobulin G or immunoglobulin E antibodies in the plasma of individuals who had developed resistance to reinfection, but were not recognized by antibodies in the plasma of individuals who remained susceptible to reinfection. Antibody levels to Sj6-8 and Sj4-1 measured in the entire cohort (N = 505) 1 month after praziquantel treatment were associated with significantly decreased risk of reinfection and lower intensity of reinfection over 18 months of follow-up.

Maternally-derived Antibodies to Schizont Egress Antigen-1 and Protection of Infants From Severe Malaria.

BACKGROUND: In holoendemic areas, children suffer the most from Plasmodium falciparum malaria, yet newborns and young infants express a relative resistance to both infection and severe malarial disease (SM). This relative resistance has been ascribed to maternally-derived anti-parasite immunoglobulin G; however, the targets of these protective antibodies remain elusive. METHODS: We enrolled 647 newborns at birth from a malaria-holoendemic region of Tanzania. We collected cord blood, measured antibodies to Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), and related these antibodies to the risk of severe malaria in the first year of life. In addition, we vaccinated female mice with PbSEA-1, mated them, and challenged their pups with P. berghei ANKA parasites to assess the impact of maternal PbSEA-1 vaccination on newborns' resistance to malaria. RESULTS: Children with high cord-blood anti-PfSEA-1 antibody levels had 51.4% fewer cases of SM compared to individuals with lower anti-PfSEA-1 levels over 12 months of follow-up (P = .03). In 3 trials, pups born to PbSEA-1-vaccinated dams had significantly lower parasitemia and longer survival following a P. berghei challenge compared to pups born to control dams. CONCLUSIONS: We demonstrate that maternally-derived, cord-blood anti-PfSEA-1 antibodies predict decreased risk of SM in infants and vaccination of mice with PbSEA-1 prior to pregnancy protects their offspring from lethal P. berghei challenge. These results identify, for the first time, a parasite-specific target of maternal antibodies that protect infants from SM and suggest that vaccination of pregnant women with PfSEA-1 may afford a survival advantage to their offspring.

Maternal anemia type during pregnancy is associated with anemia risk among offspring during infancy.

BACKGROUND: We evaluated the association between etiology of maternal anemia and iron status throughout infancy. METHODS: Samples from a study designed to examine Praziquantel treatment during pregnancy were used (n = 359). All women were infected with schistosomiasis and randomized to Praziquantel or placebo at 16 ± 2 weeks' gestation. Hemoglobin, serum ferritin (SF), soluble transferrin receptor (sTfR), hepcidin, C-reactive protein, and interleukin-6 were measured in maternal and infant blood. The relationship between both maternal Praziquantel treatment and etiology of anemia and infant iron status was evaluated. RESULTS: Maternal iron-deficiency anemia was associated with increased risk of infant anemia at 6 months of age. Infants of mothers with the lowest levels of circulating hepcidin during gestation, likely a marker for iron deficiency, had higher sTfR:SF levels and lower hemoglobin levels, particularly at 12 months of age. Maternal non-iron-deficiency anemia (NIDA) did not impact infant anemia risk or iron status. Maternal treatment for schistosomiasis had no effect on infant hematologic status. CONCLUSIONS: Maternal iron deficiency anemia was associated with an increased risk for anemia or iron deficiency during late infancy. We did not observe an association between maternal NIDA and increased risk for iron deficiency during infancy.

Anemia of Inflammation during Human Pregnancy Does Not Affect Newborn Iron Endowment.

Background: To our knowledge, no studies have addressed whether maternal anemia of inflammation (AI) affects newborn iron status, and few have addressed risk factors for specific etiologies of maternal anemia. Objectives: The study aims were to evaluate 1) the contribution of AI and iron deficiency anemia (IDA) to newborn iron endowment, 2) hepcidin as a biomarker to distinguish AI from IDA among pregnant women, and 3) risk factors for specific etiologies of maternal anemia. Methods: We measured hematologic biomarkers in maternal blood at 12 and 32 wk of gestation and in cord blood from a randomized trial of praziquantel in 358 pregnant women with Schistosoma japonicum in The Philippines. IDA was defined as anemia with serum ferritin <30 ng/mL and non-IDA (NIDA), largely due to AI, as anemia with ferritin ≥30 ng/mL. We identified cutoffs for biomarkers to distinguish IDA from NIDA by using area under the curve (AUC) analyses and examined the impact of different causes of anemia on newborn iron status (primary outcome) by using multivariate regression modeling. Results: Of the 358 mothers, 38% (n = 136) had IDA and 9% (n = 32) had NIDA at 32 wk of gestation. At 32 wk of gestation, serum hepcidin performed better than soluble transferrin receptor (sTfR) in identifying women with NIDA compared with the rest of the cohort (AUCs: 0.75 and 0.70, respectively) and in identifying women with NIDA among women with anemia (0.73 and 0.72, respectively). The cutoff that optimally distinguished women with NIDA from women with IDA in our cohort was 6.1 µg/L. Maternal IDA, but not NIDA, was associated with significantly lower newborn ferritin (114.4 ng/mL compared with 148.4 µg/L; P = 0.042). Conclusions: Hepcidin performed better than sTfR in identifying pregnant women with NIDA, but its cost may limit its use. Maternal IDA, but not NIDA, is associated with decreased newborn iron stores, emphasizing the need to identify this cause and provide iron therapy. This trial was registered at www.clinicaltrials.gov as NCT00486863.

Antibody levels to recombinant VAR2CSA domains vary with Plasmodium falciparum parasitaemia, gestational age, and gravidity, but do not predict pregnancy outcomes.

BACKGROUND: Maternal malaria is a tropical scourge associated with poor pregnancy outcomes. Women become resistant to Plasmodium falciparum pregnancy malaria as they acquire antibodies to the variant surface antigen VAR2CSA, a leading vaccine candidate. Because malaria infection may increase VAR2CSA antibody levels and thereby confound analyses of immune protection, gravidity-dependent changes in antibody levels during and after infection, and the effect of VAR2CSA antibodies on pregnancy outcomes were evaluated. METHODS: Pregnant women enrolled in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali provided plasma samples at enrollment, gestational week 30-32, and delivery. Antibody levels to VAR2CSA domains were measured using a multiplex bead-based assay. RESULTS: Antibody levels to VAR2CSA were higher in multigravidae than primigravidae. Malaria infection was associated with increased antibody levels to VAR2CSA domains. In primigravidae but not in secundigravidae or multigravidae, antibodies levels sharply declined after an infection. A relationship between any VAR2CSA antibody specificity and protection from adverse pregnancy outcomes was not detected. CONCLUSIONS: During malaria infection, primigravidae acquire short-lived antibodies. The lack of an association between VAR2CSA domain antibody reactivity and improved pregnancy outcomes suggests that the recombinant proteins may not present native epitopes targeted by protective antibodies.

Systemic Inflammatory Response to Malaria During Pregnancy Is Associated With Pregnancy Loss and Preterm Delivery.

BACKGROUND: Pregnancy malaria (PM) is associated with a proinflammatory immune response characterized by increased levels of cytokines and chemokines such as tumor necrosis factor-α, interferon-γ, interleukin 10 (IL-10), and CXCL9. These changes are associated with poor outcomes including low birthweight delivery and maternal anemia. However, it is unknown if inflammatory pathways during malaria are related to pregnancy loss and preterm delivery (PTD). METHODS: Cytokine and chemokine levels were measured in maternal peripheral blood at enrollment, gestational week 30-32, and delivery, and in placental blood, of 638 women during a longitudinal cohort study in Ouelessebougou, Mali. Plasmodium falciparum infection was assessed by blood smear microscopy at all visits. RESULTS: PM was associated with increased levels of cytokines and chemokines including IL-10 and CXCL9. In a competing risks model adjusted for known covariates, high CXCL9 levels measured in the peripheral blood during pregnancy were associated with increased risk of pregnancy loss and PTD. At delivery, high IL-10 levels in maternal blood were associated with an increase in pregnancy loss, and increased IL-1ß levels in placental blood were associated with pregnancy loss and PTD. CONCLUSIONS: PM is associated with increased proinflammatory cytokine and chemokine levels in placental and maternal peripheral blood. Systemic inflammatory responses to malaria during pregnancy predict increased risk of pregnancy loss and PTD. CLINICAL TRIALS REGISTRATION: NCT01168271.

Schistosomiasis japonica during pregnancy is associated with elevated endotoxin levels in maternal and placental compartments.

Schistosomiasis affects approximately 40 million women of reproductive age and has been linked to elevated levels of circulating endotoxin in nonpregnant individuals. We have evaluated endotoxin levels in maternal, placental, and newborn blood collected from women residing in Leyte, Philippines. Endotoxin levels in both maternal and placental compartments in pregnant women with schistosomiasis were 1.3- and 2.4-fold higher, respectively, than in uninfected women. In addition, higher concentrations of endotoxin in placental blood were associated with premature birth, acute chorioamnionitis, and elevated proinflammatory cytokines. By promoting endotoxemia, schistosomiasis may exert additional, maladaptive influences on pregnancy outcomes.

T follicular helper cell profiles differ by malaria antigen and for children compared to adults.

Background: Circulating T-follicular helper (cT FH ) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum ( Pf) as they are essential to promote B cell production of long-lasting antibodies. Assessing the specificity of cT FH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates. Methods: Using spectral flow cytometry and unbiased clustering analysis we assessed antigen-specific cT FH cell recall responses in vitro to malaria vaccine candidates Pf SEA-1A and Pf GARP within a cross-section of children and adults living in a malaria holoendemic region of western Kenya. Findings: In children, a broad array of cT FH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, Pf SEA-1A and Pf GARP, while adults had a narrow profile centering on cT FH 17- and cT FH 1/17-like subsets following stimulation with Pf GARP only. Interpretation: Because T FH 17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that Pf GARP might generate longer lived antibody responses compared to Pf SEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cT FH profiles when assessing interdependent correlates of protective immunity.

Immunization with PfGBP130 generates antibodies that inhibit RBC invasion by P. falciparum parasites.

Background: Despite decades of effort, Plasmodium falciparum malaria remains a leading killer of children. The absence of a highly effective vaccine and the emergence of parasites resistant to both diagnosis as well as treatment hamper effective public health interventions. Methods and results: To discover new vaccine candidates, we used our whole proteome differential screening method and identified PfGBP130 as a parasite protein uniquely recognized by antibodies from children who had developed resistance to P. falciparum infection but not from those who remained susceptible. We formulated PfGBP130 as lipid encapsulated mRNA, DNA plasmid, and recombinant protein-based immunogens and evaluated the efficacy of murine polyclonal anti-PfGBP130 antisera to inhibit parasite growth in vitro. Immunization of mice with PfGBP130-A (aa 111-374), the region identified in our differential screen, formulated as a DNA plasmid or lipid encapsulated mRNA, but not as a recombinant protein, induced antibodies that inhibited RBC invasion in vitro. mRNA encoding the full ectodomain of PfGBP130 (aa 89-824) also generated parasite growth-inhibitory antibodies. Conclusion: We are currently advancing PfGBP130-A formulated as a lipid-encapsulated mRNA for efficacy evaluation in non-human primates.

Schistosome egg antigens elicit a proinflammatory response by trophoblast cells of the human placenta.

Schistosomiasis affects nearly 40 million women of reproductive age. Many of these women are infected while pregnant and lactating. Several studies have demonstrated transplacental trafficking of schistosome antigens; however, little is known regarding how these antigens affect the developing fetus and placenta. To evaluate the impact of schistosomiasis on trophoblasts of the human placenta, we isolated primary trophoblast cells from healthy placentas delivered at term. These trophoblasts were placed in culture and treated with Schistosoma japonicum soluble egg antigens (SEA) or plasma from S. japonicum-infected pregnant women. Outcomes measured included cytokine production and activation of signal transduction pathways. Treatment of primary human trophoblast cells with SEA resulted in upregulation of the proinflammatory cytokines interleukin 6 (IL-6) and IL-8 and the chemokine macrophage inflammatory protein 1α (MIP-1α). Cytokine production in response to SEA was dose dependent and reminiscent of production in response to other proinflammatory stimuli, such as Toll-like receptor 2 (TLR2) and TLR4 agonists. In addition, the signaling pathways extracellular signal-regulated kinase 1/2 (ERK1/2), Jun N-terminal protein kinase (JNK), p38, and NF-κB were all activated by SEA in primary trophoblasts. These effects appeared to be mediated through both carbohydrate and protein epitopes of SEA. Finally, primary trophoblasts cocultured with plasma from S. japonicum-infected pregnant women produced increased levels of IL-8 compared to trophoblasts cocultured with plasma from uninfected pregnant women. We report here a direct impact of SEA on primary human trophoblast cells, which are critical for many aspects of a healthy pregnancy. Our data indicate that schistosome antigens can activate proinflammatory responses in trophoblasts, which might compromise maternal-fetal health in pregnancies complicated by schistosomiasis.

CXC ligand 9 response to malaria during pregnancy is associated with low-birth-weight deliveries.

Placental infection with Plasmodium falciparum is associated with increased levels of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ), and previous studies have associated increased levels of these cytokines with low birth weight (LBW), especially for malaria-infected primigravidae. To define the contribution of TNF-α and IFN-γ networks to placental-malaria-associated LBW, we measured chemokines induced by TNF-α and IFN-γ and related them to birth weight in a birth cohort of 782 mother-infant pairs residing in an area of P. falciparum holoendemicity in Tanzania. Among primigravidae, levels of CCL2, CXC ligand 9 (CXCL9), and CXCL13 were significantly higher during malaria infection in both the placenta and peripheral blood. Placental CXCL9 and CXCL13 levels were also higher in placental blood from secundigravidae and multigravidae. In multivariate analyses adjusted for known predictors of birth weight, malaria-infected primigravidae with placental CXCL9 levels in the lowest tertile gave birth to babies who weighed 610 g more than babies born to mothers with high CXCL9 levels. CXCL9 expression is induced by IFN-γ, and the strong association between birth weight and placental CXCL9 is consistent with previous observations relating IFN-γ to poor pregnancy outcomes.

A newly characterized malaria antigen on erythrocyte and merozoite surfaces induces parasite inhibitory antibodies.

We previously identified a Plasmodium falciparum (Pf) protein of unknown function encoded by a single-copy gene, PF3D7_1134300, as a target of antibodies in plasma of Tanzanian children in a whole-proteome differential screen. Here we characterize this protein as a blood-stage antigen that localizes to the surface membranes of both parasitized erythrocytes and merozoites, hence its designation as Pf erythrocyte membrane and merozoite antigen 1 (PfEMMA1). Mouse anti-PfEMMA1 antisera and affinity-purified human anti-PfEMMA1 antibodies inhibited growth of P. falciparum strains by up to 68% in growth inhibition assays. Following challenge with uniformly fatal Plasmodium berghei (Pb) ANKA, up to 40% of mice immunized with recombinant PbEMMA1 self-cured, and median survival of lethally infected mice was up to 2.6-fold longer than controls (21 vs. 8 d, P = 0.005). Furthermore, high levels of naturally acquired human anti-PfEMMA1 antibodies were associated with a 46% decrease in parasitemia over 2.5 yr of follow-up of Tanzanian children. Together, these findings suggest that antibodies to PfEMMA1 mediate protection against malaria.

Can Unconventional Immunomodulatory Agents Help Alleviate COVID-19 Symptoms and Severity?

Severe acute respiratory syndrome coronavirus 2 (SARS coronavirus 2, or SARS-CoV-2) is the cause of the respiratory infection known as COVID-19. From an immunopathological standpoint, coronaviruses such as SARS-CoV-2 induce increased levels of a variety of T-helper 1 (Th1) and inflammatory cytokines and chemokines, including interleukin-1 (IL-1), IL-6, CCL2 protein, and CXCL10 protein. In the absence of proven antiviral agents or an effective vaccine, substances with immunomodulatory activity may be able to inhibit inflammatory and Th1 cytokines and/or yield an anti-inflammatory and/or Th2 immune response to counteract COVID-19 symptoms and severity. This report briefly describes the following four unconventional but commercially accessible immunomodulatory agents that can be employed in clinical trials to evaluate their effectiveness at alleviating disease symptoms and severity: low-dose oral interferon alpha, microdose DNA, low-dose thimerosal, and phytocannabinoids.

Immunoglobulin E (IgE) responses to paramyosin predict resistance to reinfection with Schistosoma japonicum and are attenuated by IgG4.

Schistosomiasis remains a public health concern in developing countries, and rapid reinfection fostered by continued exposure to contaminated water sources necessitates a vaccine to augment current mass treatment-based control strategies. We report isotype-specific (immunoglobulin A [IgA], IgE, IgG1, IgG4, and IgG) antibody responses to soluble worm antigen preparation and the recombinant vaccine candidates rSj97, rSj67, and rSj22 from a Schistosoma japonicum-infected cohort in Leyte, the Philippines, where schistosomiasis is endemic. Sera were collected from infected individuals 1 month posttreatment with praziquantel, and antibody responses were measured using a bead-based multiplex platform. Reinfection was monitored by stool sampling every 3 months, and data up to 1 year were included in the analysis (n = 553). In repeated-measures models, individuals with detectible IgE responses to rSj97 had a 26% lower intensity of reinfection at 12 months posttreatment compared to nonresponders after adjusting for age, gender, village, exposure, pretreatment infection intensity, and clustering by household (P = 0.018). In contrast, IgG4 responses to rSj97 as well as rSj67 and rSj22 were associated with markedly increased reinfection intensity. When stratified by IgG4 and IgE responder status, individuals with IgE but not IgG4 responses to rSj97 (n = 16) had a 77% lower intensity of reinfection at 12 months compared to individuals with IgG4 responses but not IgE responses (n = 274), even after adjusting for potential confounders (P = 0.016). Together with our previously described protective cytokine responses, these data further support paramyosin as a leading vaccine candidate for human schistosomiasis japonica and underscore the importance of careful adjuvant selection to avoid the generation of blocking IgG4 antibody responses.

Impact of maternally derived antibodies to Plasmodium falciparum Schizont Egress Antigen-1 on the endogenous production of anti-PfSEA-1 in offspring.

BACKGROUND: We evaluated whether maternally-derived antibodies to a malarial vaccine candidate, Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), in cord blood interfered with the development of infant anti-PfSEA-1 antibodies in response to natural exposure. METHODS: We followed 630 Tanzanian infants who were measured their antibodies against PfSEA-1 (aa 810-1023; PfSEA-1A) at birth and 6, 12, 18, and 24 months of age, and examined the changes in anti-PfSEA-1A antibody levels in response to parasitemia, and evaluated whether maternally-derived anti-PfSEA-1A antibodies in cord blood modified infant anti-PfSEA-1A immune responses. RESULTS: Infants who experienced parasitemia during the first 6 months of life had significantly higher anti-PfSEA-1A antibodies at 6 and 12 months of age compared to uninfected infants. Maternally-derived anti-PfSEA-1A antibodies in cord blood significantly modified this effect during the first 6 months. During this period, infant anti-PfSEA-1A antibody levels were significantly associated with their P. falciparum exposure when they were born with low, but not higher, maternally-derived anti-PfSEA-1A antibody levels in cord blood. Nevertheless, during the first 6 months of life, maternally-derived anti-PfSEA-1A antibodies in cord blood did not abrogate the parasitemia driven development of infant anti-PfSEA-1A: parasitemia were significantly correlated with anti-PfSEA-1A antibody levels at 6 months of age in the infants born with low maternally-derived anti-PfSEA-1A antibody levels in cord blood and borderline significantly correlated in those infants born with middle and high levels. CONCLUSIONS: Maternal vaccination with PfSEA-1A is unlikely to interfere with the development of naturally acquired anti-PfSEA-1A immune responses following exposure during infancy.

Maternal, placental and cord blood cytokines and the risk of adverse birth outcomes among pregnant women infected with Schistosoma japonicum in the Philippines.

BACKGROUND: The objectives of this study were to 1) evaluate the influence of treatment with praziquantel on the inflammatory milieu in maternal, placental, and cord blood, 2) assess the extent to which proinflammatory signatures in placental and cord blood impacts birth outcomes, and 3) evaluate the impact of other helminths on the inflammatory micro environment. METHODS/FINDINGS: This was a secondary analysis of samples from 369 mother-infant pairs participating in a randomized controlled trial of praziquantel given at 12-16 weeks' gestation. We performed regression analysis to address our study objectives. In maternal peripheral blood, the concentrations of CXCL8, and TNF receptor I and II decreased from 12 to 32 weeks' gestation, while IL-13 increased. Praziquantel treatment did not significantly alter the trajectory of the concentration of any of the cytokines examined. Hookworm infection was associated with elevated placental IL-1, CXCL8 and IFN-γ. The risk of small-for-gestational age increased with elevated IL-6, IL-10, and CXCL8 in cord blood. The risk of prematurity was increased when cord blood sTNFRI and placental IL-5 were elevated. CONCLUSIONS: Our study suggests that fetal cytokines, which may be related to infectious disease exposures, contribute to poor intrauterine growth. Additionally, hookworm infection influences cytokine concentrations at the maternal-fetal interface. CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE: ClinicalTrials.gov (NCT00486863).

Pilot-scale production and characterization of paramyosin, a vaccine candidate for schistosomiasis japonica.

Despite effective chemotherapy, schistosomiasis remains a major public health problem in the developing world, with at least 200 million active infections resulting in significant morbidity. Rapid reinfection after treatment, accompanied by extensive residual morbidity, mandates alternative control strategies, including vaccine development. Paramyosin, a myofibrillar protein found only in invertebrates, has been widely studied as a vaccine candidate for both Schistosoma mansoni and Schistosoma japonicum. Recently, we demonstrated that Th2-biased immune responses to paramyosin are associated with resistance to reinfection with S. japonicum in humans; however, challenges in the pilot-scale production of schistosome paramyosin have hampered further studies of this promising vaccine candidate. Here we report a method for the pilot-scale expression and purification of recombinant S. japonicum paramyosin (rSj97). rSj97 was extracted from Escherichia coli inclusion bodies and purified with sequential anion-exchange, hydroxyapatite, and size exclusion chromatography. The purified rSj97 was >95% pure as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis and was free of significant endotoxin contamination. We demonstrate that, like native paramyosin, rSj97 adopts an alpha-helical coiled-coil tertiary structure and binds immunoglobulin and collagen. Naïve mice infected with S. japonicum produce anti-rSj97 immunoglobulin G (IgG) antibodies as early as 4 weeks postinfection, while sera collected from S. japonicum-infected individuals contain anti-rSj97 IgE antibodies. Our method for pilot-scale production of recombinant full-length paramyosin will facilitate preclinical evaluation of paramyosin as a vaccine for schistosomiasis.

Vaccination with recombinant paramyosin in Montanide ISA206 protects against Schistosoma japonicum infection in water buffalo.

BACKGROUND: Schistosomiasis japonica is a zoonosis and presents significant public health problems in China and the Philippines. Vaccines targeting domestic animals constitute attractive control measures. METHODS: We conducted three vaccine trials to evaluate the protective efficacy of recombinant full-length paramyosin (rSj97) in water buffalo. Animals were immunized with 3 doses of rSj97 adjuvanted with ISA206 at 250µg/dose or 500µg/dose at 4wk intervals before challenge with 1000 Schistosoma japonicum cercariae. The primary outcome was worm burden assessed by portal perfusion 8-10weeks post challenge. Safety measures included weight, temperature, body condition score, hemogram and routine assays for hepatic and renal function. RESULTS: The three-dose regimen was well tolerated in all three trials. In the first trial, vaccinated buffalo had 51.5% lower worm burden post challenge compared to controls. In the second trial, buffalo immunized with 500µg/dose of rSj97 had 57.8% lower worm burden compared to controls (p=0.026). A similar but not significant reduction (60.9%) was observed with animals administered with 250ug rSj97/dose. In the third trial, buffalo immunized with a 500µg/dose of rSj97 had 57.8% lower worm burden compared to controls (p=0.014). CONCLUSIONS: These findings indicated that rSj97 is a safe and promising vaccine candidate for schistosomiasis japonica in water buffalo.