• Parasites, Hosts and Diseases
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• v.42 no.2
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• pp.61-66
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• 2004

The plasmepsins are the aspartic proteases of malaria parasites. Treatment of aspartic protease inhibitor inhibits hemoglobin hydrolysis and blocks the parasite development in vitro suggesting that these proteases might be exploited their potentials as antimalarial drug targets. In this study, we determined the genetic variations of the aspartic proteases of Plasmodium vivax (PvPMs) of wild isolates. Two plasmepsins (PvPM4 and PvPM5) were cloned and sequenced from 20 P. vivax Korean isolates and two imported isolates. The sequences of the enzymes were highly conserved except a small number of amino acid substitutions did not modify key residues for the function or the structure of the enzymes. The high sequence conservations between the plasmepsins from the isolates support the notion that the enzymes could be reliable targets for new antimalarial chemotherapeutics.

• Parasites, Hosts and Diseases
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• v.53 no.4
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• pp.403-411
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• 2015

Plasmodium falciparum can invade all stages of red blood cells, while Plasmodium vivax can invade only reticulocytes. Although many P. vivax proteins have been discovered, their functions are largely unknown. Among them, P. vivax reticulocyte binding proteins (PvRBP1 and PvRBP2) recognize and bind to reticulocytes. Both proteins possess a C-terminal hydrophobic transmembrane domain, which drives adhesion to reticulocytes. PvRBP1 and PvRBP2 are large (>326 kDa), which hinders identification of the functional domains. In this study, the complete genome information of the P. vivax RBP family was thoroughly analyzed using a prediction server with bioinformatics data to predict B-cell epitope domains. Eleven pvrbp family genes that included 2 pseudogenes and 9 full or partial length genes were selected and used to express recombinant proteins in a wheat germ cell-free system. The expressed proteins were used to evaluate the humoral immune response with vivax malaria patients and healthy individual serum samples by protein microarray. The recombinant fragments of 9 PvRBP proteins were successfully expressed; the soluble proteins ranged in molecular weight from 16 to 34 kDa. Evaluation of the humoral immune response to each recombinant PvRBP protein indicated a high antigenicity, with 38-88% sensitivity and 100% specificity. Of them, N-terminal parts of PvRBP2c (PVX_090325-1) and PvRBP2 like partial A (PVX_090330-1) elicited high antigenicity. In addition, the PvRBP2-like homologue B (PVX_116930) fragment was newly identified as high antigenicity and may be exploited as a potential antigenic candidate among the PvRBP family. The functional activity of the PvRBP family on merozoite invasion remains unknown.

• Parasites, Hosts and Diseases
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• v.57 no.4
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• pp.329-339
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• 2019

Indonesia and South Korea have become inseparable in various respects since the 2 countries established diplomatic relation in 1973. Indonesia is a tropical region that stretches across the equator, comprised of 5 main islands (Java, Kalimantan, Sumatra, Sulawesi, and Papua) and 4 archipelagoes (Riau, Bangka Belitung, Nusa Tenggara, and Maluku). As most population of Eastern Indonesia (Sulawesi, Papua and Nusa Tenggara & Maluku) live in poor areas, it is expected that there will be many parasites. Nevertheless, little is known about the status of parasites in Indonesia. This study examines the prevalences of malaria and lymphatic filaria, which are prevalent in Indonesia, as well as those of soil-transmitted-helminths (STH). As a result, the Plasmodium falciparum and P. vivax case loads are almost equal. The current prevalence of P. vivax is uniformly low (<5%) in all age groups and annual parasite incidence (API) showed decreasing tendency as 0.84 per 1,000 population in 2016. However, more than 65 million people still live in malaria epidemic regions. Lymphatic filariasis remains an important public health problem and 236 cities were classified as endemic areas in 514 cities/districts in 2017. It is difficult to ascertain the current prevalence rate of STH in Indonesia, although West Sumba and Southwest Sumba in East Nusa Tenggara reported prevalence rate of more than 20%. The study also considers the (sero) prevalences of other parasites identified in Indonesia. This report should be useful not only to parasitologists but also to travelers and people with business in Indonesia.

• Parasites, Hosts and Diseases
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• v.54 no.3
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• pp.253-259
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• 2016

In the era of (pre) elimination setting, the prevalence of malaria has been decreasing in most of the previously endemic areas. Therefore, effective cost- and time-saving validated pooling strategy is needed for detection of malaria in low transmission settings. In this study, optimal pooling numbers and lowest detection limit were assessed using known density samples prepared systematically, followed by genomic DNA extraction and nested PCR. Pooling strategy that composed of 10 samples in 1 pool, $20{\mu}l$ in 1 sample, was optimal, and the parasite density as low as $2p/{\mu}l$ for both falciparum and vivax infection was enough for detection of malaria. This pooling method showed effectiveness for handling of a huge number of samples in low transmission settings (<9% positive rate). The results indicated that pooling of the blood samples before DNA extraction followed by usual nested PCR is useful and effective for detection of malaria in screening of hidden cases in low-transmission settings.

• Pediatric Infection and Vaccine
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• v.7 no.2
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• pp.218-224
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• 2000

Purpose : In Korea, vivax malaria has been reemerged since 1993 after being abscent for more than 10 years. There are several possibilities of casuality of recent epidemic, although it is still unclear. The epidemiologic studies including case analysis and entomological reseach have been undertaken for a successful control measure. But, unfortunately those studies have been rarely dealt with cases of children. Therefore, this study was designed to figure out the characteristics of epidemiolgic and clinical features in children with indigenous vivax malaria. Methods : The study 21 cases below 15 years of age, who were diagnosed as vivax malaria and resided in kyounggi-do province area during 1998. 9~1999. 8. We retrospectively analyzed epidemiologic data concernig with occurrence of vivax, and clinical manifestations, abnormal laboratory findings and outcomes including therapeutic responses. Results : All cases were inhabitants of the endemic areas for vivax malaria in northwestern part of Kyonggi-do or western Kangwon-do, and Paju-gun was the most prevalent. Indigenous malaria cases of this study were more prevalent in children above 10 years old age, and in male. Seasonally, vivax malaria in children occurred throughout the year except January, March and November, and the incidence was the highest in July. Clinical manifestations revealed that 48 hour cyclic fever pattern was the major fever pattern, and other symptoms such as headache, vomiting, poor appetites, chilling, abdominal pain and diarrhea were concomitantly developed. And splenomegaly revealed the main abnormal findings on physical examination, and anemia was the most frequent abnormal finding in laboratory examinations. Young trophozoite was frequently observed on peripheral blood smears. The therapeutic responses of chlorquine were very good in all cases, and no recurrence developed in follow up cases. Conclusion : Geographical and seasonal occurrence distributions of indigenous vivax malaria cases in children were very similar to those of adults as followings; Inhabitants of the endemic region, more prevalent in male, and more common during the summer season. Clinically, 48 hour cyclic fever pattern, splenomegaly and anemia were most frequent and important manifestations in children cases, and clinical courses were not serious. On blood smears, young trophozoite was most dominantly examined in children. Generally, the therapeutic outcomes were excellent, and recurrences were not observed.

• Parasites, Hosts and Diseases
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• v.54 no.6
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• pp.725-732
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• 2016

Plasmodium vivax produces numerous caveola-vesicle complex (CVC) structures beneath the membrane of infected erythrocytes. Recently, a member helical interspersed subtelomeric (PHIST) superfamily protein, $PcyPHIST/CVC-81_{95}$, was identified as CVCs-associated protein in Plasmodium cynomolgi and essential for survival of this parasite. Very little information has been documented to date about $PHIST/CVC-81_{95}$ protein in P. vivax. In this study, the recombinant $PvPHIST/CVC-81_{95}$ N and C termini were expressed, and immunoreactivity was assessed using confirmed vivax malaria patients sera by protein microarray. The subcellular localization of $PvPHIST/CVC-81_{95}$ N and C termini in blood stage parasites was also determined. The antigenicity of recombinant $PvPHIST/CVC-81_{95}$ N and C terminal proteins were analyzed by using serum samples from the Republic of Korea. The results showed that immunoreactivities to these proteins had 61% and 43% sensitivity and 96.9% and 93.8% specificity, respectively. The N terminal of $PvPHIST/CVC-81_{95}$ which contains transmembrane domain and export motif (PEXEL; RxLxE/Q/D) produced CVCs location throughout the erythrocytic-stage parasites. However, no fluorescence was detected with antibodies against C terminal fragment of $PvPHIST/CVC-81_{95}$. These results suggest that the $PvPHIST/CVC-81_{95}$ is localized on the CVCs and may be immunogenic in natural infection of P. vivax.

• Parasites, Hosts and Diseases
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• v.52 no.6
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• pp.639-644
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• 2014

Congenital malaria is assumed to be a risk factor for infant morbidity and mortality in endemic areas like Maumere, Indonesia. Infected infants are susceptible to its impact such as premature labor, low birth weight, anemia, and other unspecified symptoms. The aim of this study was to investigate the prevalence of congenital malaria and the influence of mother-infant paired parasite densities on the clinical outcome of the newborns at TC Hillers Hospital, Maumere. An analytical cross sectional study was carried out in newborns which showed criteria associated with congenital malaria. A thick and thin blood smear confirmed by nested PCR was performed in both mothers and infants. The association of congenital malaria with the newborn's health status was then assessed. From 112 mother-infant pairs included in this study, 92 were evaluated further. Thirty-nine infants (42.4%) were found to be infected and half of them were asymptomatic. Infected newborns had a 4.7 times higher risk in developing anemia compared to uninfected newborns (95% CI, 1.3-17.1). The hemoglobin level, erythrocyte amount, and hematocrit level were affected by the infants' parasite densities (P<0.05). Focusing on newborns at risk of congenital malaria, the prevalence is almost 3 times higher than in an unselected collective. Low birth weight, anemia, and pre-term birth were the most common features. Anemia seems to be significantly influenced by infant parasite densities but not by maternal parasitemia.

• Parasites, Hosts and Diseases
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• v.39 no.2
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• pp.185-192
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• 2001

To evaluate the factors that determine the transmission level of vivax malaria using vectorial capacity, entomological surveys were conducted from .lune to August, 2000. From 6 nights of human-bait collection in Paju, the human biting rate (ma) was counted as 87.5 bites/man/night. The parity of Anopheles sinensis from human baiting collections fluctuated from 41% to 71% (average 48.8%) of which the rate gradually increased as time passed on: 35.2% in Jun. ; 55.0% in July; 66.2% in Aug. From this proportion of parous, we could estimate the probability of daily survival rate of An. sinensis to be 0.79 assumed with 3 days gonotrophic cycle and the expectancy of infective life through 11 days could be defined as 0.073. Blood meal analysis was performed using ELISA to determine the blood meal source. Only 0.8% of blood meals were from human hosts. We could conclude that An. sinensis is highly zoophilic (cow 61.8%) Malaria is highly unstable (stability index < 0.5) in this area. From these data, vectorial capacity VC) was determined to be 0.081. In spite of a high human biting rate (ma), malaria transmission potential is very low due to a low human blood index. Therefore, we could conclude that malaria transmission by An. sinensis is resulted by high population density, not by high transmission potential. For this reason, we need more effort to decrease vector population and vector-human contact to eradicate malaria in Korea.

• Laboratory Medicine Online
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• v.1 no.2
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• pp.100-104
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• 2011

Background: Malaria is a problematic disease in Korea, and microscopic examination of Giemsa-stained blood smear has been used as the gold standard for its diagnosis. However, this technique is time-consuming and has low sensitivity in samples with low numbers of malarial parasites (<20 parasites/μL). Here, we evaluated the performance characteristics of the LG Advansure^TM Malaria P.f./P.v. real-time QPCR (LG life sciences, Korea). Methods: Blood samples from 173 persons who visited Korea University Ansan Hospital were evaluated. QPCR was performed in 73 malaria patients and 100 healthy subjects by using the LG Advansure Malaria P.f./P.v. real-time QPCR^R kit, and the results were compared with those of microscopy. The detection limit of this kit was determined by serial dilution of Plasmodium-infected blood with normal blood (blood not infected with Plasmodium). Results: Among the 73 patients that were microscopically confirmed to have malaria (Plasmodium vivax infection, N=70, P. falciparum infection, N=3), 69 patients were diagnosed with P. vivax infection and 3 were diagnosed with P. falciparum infection by LG Advansure^TM Malaria P.f./P.v. realtime QPCR. Both the tests indicated absence of infection in the 100 healthy subjects. The detection limit of LG Advansure^TM Malaria P.f./P.v. real-time QPCR was 0.1 parasite/μL. Conclusions: LG Advansure^TM Malaria P.f./P.v. real-time QPCRis a very sensitive and specific technique and can be used as a confirmatory test for malaria.

• Parasites, Hosts and Diseases
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• v.56 no.2
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• pp.167-173
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• 2018

Malaria is one of the most important public health problems in tropical areas on the globe. Several factors are associated with susceptibility to malaria and disease severity, including innate immunity such as blood group, hemoglobinopathy, and heme oxygenase-1 (HO-1) polymorphisms. This study was carried out to investigate association among ABO blood group, thalassemia types and HO-1 polymorphisms in malaria. The malarial blood samples were collected from patients along the Thai-Myanmar border. Determination of ABO blood group, thalassemia variants, and HO-1 polymorphisms were performed using agglutination test, low pressure liquid chromatography and polymerase chain reaction, respectively. Plasmodium vivax was the major infected malaria species in the study samples. Distribution of ABO blood type in the malaria-infected samples was similar to that in healthy subjects, of which blood type O being most prevalent. Association between blood group A and decreased risk of severe malaria was significant. Six thalassemia types (30%) were detected, i.e., hemoglobin E (HbE), ${\beta}$-thalassemia, ${\alpha}$-thalassemia 1, ${\alpha}$-thalassemia 2, HbE with ${\alpha}$-thalassemia 2, and ${\beta}$-thalassemia with ${\alpha}$-thalassemia 2. Malaria infected samples without thalassemia showed significantly higher risk to severe malaria. The prevalence of HO-1 polymorphisms, S/S, S/L and L/L were 25, 62, and 13%, respectively. Further study with larger sample size is required to confirm the impact of these 3 host genetic factors in malaria patients.