In malaria-endemic areas, by young adulthood people have developed functional immunity to malaria. However, during pregnancy this immunity is breached and infection occurs, leading to increased risks for mother and child. In the past this effect has been attributed to nonspecific immunosuppression, but recent research has revealed a specific pathogenic mechanism, involving the adherence of rare parasite variants to the placenta. This commentary explores the current state of research in this area and proposes a model of immune evasion and placental colonization. This model points the way to the development of future therapeutic interventions.
Female ; Humans ; Malaria, Falciparum - immunology ; Pregnancy ; Pregnancy Complications ; Parasitic - immunology

Toll-like receptors (TLRs) have emerged as major receptor components of pattern-recognition receptors (PRRs), which are responsible for the recognition of pathogen-associated molecular patterns (PAMPs)-derived pathogenic parasites. This recognition triggers the secretion of a large amount of type I interferons (IFNs), inflammatory cytokines, and chemokines and maturation of immune cells, for effective host defense by eradicating infectious parasites. Both the myeloid differentiation factor 88 (MyD88) and the TIR domain containing the adaptor molecule (TRIF) are involved in these signaling pathways. Here, we review the latest findings on the recognition of the pathogenic parasites and activation of corresponding signaling pathways through TLRs, with special emphasis on the recognition of pathogenic protozoan and helminthes. By highlighting recent progress in these areas, we hope to provide references in future studies not only for the complexity of host-parasite interactions but also for the prevention of the pathogenic parasite infections.
Animals ; Host-Parasite Interactions ; immunology ; Humans ; Immunity, Innate ; immunology ; Malaria, Falciparum ; parasitology ; Plasmodium falciparum ; immunology ; Signal Transduction ; Toll-Like Receptors ; immunology ; Trypanosoma ; immunology ; Trypanosomiasis ; parasitology

Plasmodium falciparum liver stage antigen-1 (PfLSA-1) is one of the few antigens expressed exclusively in liver stage parasites. In this study, we evaluated the antibody responses against recombinant PfLSA-1 in naturally infected individuals in Myanmar. High levels of antibody responses (70.7%) were detected in 82 serum samples from 116 infected individuals, and IgG responses to PfLSA-1 principally composed of responses of IgG1 and IgG3 subclasses. These results show that PfLSA-1 elicits effective antibody responses in individuals infected with P. falciparum, and thus it could be not only an attractive candidate protein for vaccine development, but also a useful antigen for serodiagnosis of the infection.
Animals ; Antibodies, Protozoan/*blood/immunology ; Antigens, Protozoan/*immunology ; Humans ; Immunoglobulin G/blood ; Malaria, Falciparum/blood/epidemiology/*immunology ; Myanmar/epidemiology

Rhesus monkeys (5 in each group) were inoculated with recombinant fusion protein of cholera toxin B subunit and multi-valent epitopes of Plasmodium falciparum intranasal or intramuscular (i.m.). Immune-responses and protective effect were evaluated. The antibody titer (Geometry mean) against CTB reached 1:512 (intranasal) and 1:10000 (i.m.) 14 day after 3rd immunization, and antibodies against P. falciparum were also elucidated, the titers in i.m. group were also significantly higher than that in intranasal group. The monkeys were challenged with 1.25 x 10(8) sporozoites of P. cynomolgi, Patent infection was observed in all 5 monkeys in control group inoculated with PBS in 10 - 14 days after challenge. Patent infection was also observed in 5 animals inoculated via intranasal and 2 animals in intramuscular group 19th days after challenge, But the infection last only 4 days in 3 animals in intranasal group and 2 animals in intramuscular group. The results demonstrated that the vaccine candidate could induce protective immune-responses in rhesus monkey against the challenge of P. cynomolgi.
Animals ; Antibodies, Bacterial ; blood ; Antibodies, Protozoan ; blood ; Cholera Toxin ; genetics ; immunology ; Erythrocytes ; parasitology ; Macaca mulatta ; Malaria ; prevention & control ; veterinary ; Malaria Vaccines ; immunology ; Monkey Diseases ; prevention & control ; Plasmodium cynomolgi ; Plasmodium falciparum ; immunology ; Recombinant Fusion Proteins ; immunology ; Vaccines, Synthetic ; immunology

Prompt and accurate diagnosis of malaria is the key to prevent disease morbidity and mortality. This study was carried out to evaluate diagnostic performance of 3 commercial rapid detection tests (RDTs), i.e., Malaria Antigen Pf/Pantrade mark, Malaria Ag-Pftrade mark, and Malaria Ag-Pvtrade mark tests, in comparison with the microscopic and PCR methods. A total of 460 blood samples microscopically positive for Plasmodium falciparum (211 samples), P. vivax (218), mixed with P. falciparum and P. vivax (30), or P. ovale (1), and 124 samples of healthy subjects or patients with other fever-related infections, were collected. The sensitivities of Malaria Ag-Pftrade mark and Malaria Antigen Pf/Pantrade mark compared with the microscopic method for P. falciparum or P. vivax detection were 97.6% and 99.0%, or 98.6% and 99.0%, respectively. The specificities of Malaria Ag-Pftrade mark, Malaria Ag-Pvtrade mark, and Malaria Antigen Pf/Pantrade mark were 93.3%, 98.8%, and 94.4%, respectively. The sensitivities of Malaria Ag-Pftrade mark, Malaria Antigen Pf/Pantrade mark, and microscopic method, when PCR was used as a reference method for P. falciparum or P. vivax detection were 91.8%, 100%, and 96.7%, or 91.9%, 92.6%, and 97.3%, respectively. The specificities of Malaria Ag-Pftrade mark, Malaria Ag-Pvtrade mark, Malaria Antigen Pf/Pantrade mark, and microscopic method were 66.2%, 92.7%, 73.9%, and 78.2%, respectively. Results indicated that the diagnostic performances of all the commercial RDTs are satisfactory for application to malaria diagnosis.
Antigens, Protozoan/blood ; Cross-Sectional Studies ; *Diagnostic Techniques and Procedures/instrumentation ; Endemic Diseases/statistics & numerical data ; Humans ; Malaria/*diagnosis/epidemiology/parasitology ; Malaria, Vivax ; Plasmodium falciparum/genetics/immunology/*isolation & purification ; Reagent Kits, Diagnostic ; Thailand/epidemiology

In order to develop tools for an early serodiagnosis of Plasmodium falciparum infection, we evaluated the usefulness of P. falciparum liver stage antigen-3 (LSA-3) as a serodiagnostic antigen. A portion of LSA-3 gene was cloned, and its recombinant protein (rLSA-3) was expressed in Escherichia coli and purified by column chromatography. The purified rLSA-3 and 120 test blood/serum samples collected from inhabitants in malaria-endemic areas of Mandalay, Myanmar were used for this study. In microscopic examinations of blood samples, P. falciparum positive rate was 39.1% (47/120) in thin smear trials, and 33.3% (40/120) in thick smear trials. Although the positive rate associated with the rLSA-3 (30.8%) was lower than that of the blood stage antigens (70.8%), rLSA-3 based enzyme-linked immunosorbent assay could detect 12 seropositive cases (10.0%), in which blood stage antigens were not detected. These results indicate that the LSA-3 is a useful antigen for an early serodiagnosis of P. falciparum infection.
Recombinant Proteins/biosynthesis/genetics/*immunology ; Plasmodium vivax/isolation & purification ; Plasmodium falciparum/*immunology ; Molecular Sequence Data ; Malaria, Falciparum/blood/*diagnosis ; Humans ; Genes, Protozoan/genetics/immunology ; Fluorescent Antibody Technique, Direct/methods ; Escherichia coli/genetics ; Enzyme-Linked Immunosorbent Assay/methods ; Early Diagnosis ; DNA, Protozoan/chemistry ; DNA Primers/chemistry ; Cloning, Molecular/methods ; Base Sequence ; Antigens, Protozoan/biosynthesis/chemistry/genetics/*immunology ; Animals ; Amino Acid Sequence

Merozoite surface protein-1 (MSP-1) and merozoite surface protein-2 (MSP-2) were used to develop vaccines and to investigate the genetic diversity in Plasmodium falciparum malaria in Iran. Nested polymerase chain reaction amplification was used to determine polymorphisms of block 2 of the MSP-1 and the central domain of MSP-2 genes. A total of 67 microscopically positive P. falciparum infected individuals from a major endemic region, southeast Iran, were included in this trial. Nine alleles of MSP-1 and 11 alleles of MSP-2 were identified. The results showed that amplified product from these surface antigen genes varied in size and there was specific pattern for each isolate. Besides, regarding this pattern, 23 multiple infections with at least 2 alleles were observed. While the endemic regions of malaria in Iran is classified in low to moderate group, but extensive polymorphism was observed for each marker and the MSP-2 central repeat was the most diverse that could be considered in designing malaria vaccine.
Adolescent ; Adult ; Animals ; Antigens, Protozoan/*genetics ; Child ; Child, Preschool ; *Endemic Diseases ; Female ; Genetic Variation ; Humans ; Iran/epidemiology ; Malaria, Falciparum/*epidemiology/*parasitology ; Male ; Merozoite Surface Protein 1/*genetics ; Middle Aged ; Plasmodium falciparum/*genetics/immunology/isolation & purification ; Polymerase Chain Reaction/methods ; Polymorphism, Genetic ; Protozoan Proteins/*genetics

Merozoite surface protein-1 (MSP-1) and merozoite surface protein-2 (MSP-2) were used to develop vaccines and to investigate the genetic diversity in Plasmodium falciparum malaria in Iran. Nested polymerase chain reaction amplification was used to determine polymorphisms of block 2 of the MSP-1 and the central domain of MSP-2 genes. A total of 67 microscopically positive P. falciparum infected individuals from a major endemic region, southeast Iran, were included in this trial. Nine alleles of MSP-1 and 11 alleles of MSP-2 were identified. The results showed that amplified product from these surface antigen genes varied in size and there was specific pattern for each isolate. Besides, regarding this pattern, 23 multiple infections with at least 2 alleles were observed. While the endemic regions of malaria in Iran is classified in low to moderate group, but extensive polymorphism was observed for each marker and the MSP-2 central repeat was the most diverse that could be considered in designing malaria vaccine.
Adolescent ; Adult ; Animals ; Antigens, Protozoan/*genetics ; Child ; Child, Preschool ; *Endemic Diseases ; Female ; Genetic Variation ; Humans ; Iran/epidemiology ; Malaria, Falciparum/*epidemiology/*parasitology ; Male ; Merozoite Surface Protein 1/*genetics ; Middle Aged ; Plasmodium falciparum/*genetics/immunology/isolation & purification ; Polymerase Chain Reaction/methods ; Polymorphism, Genetic ; Protozoan Proteins/*genetics