Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 213
Filtrar
1.
Vaccine ; 42(9): 2135-2137, 2024 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-38453618

RESUMO

The COVID-19 pandemic has affected people of all ages worldwide. However, there is still no information on the vaccine effectiveness (VE) of inactivated COVID-19 vaccines in children aged less than 3 years old. This study highlighted that 2 doses of CoronaVac were effective in preventing COVID-19, with a VE of 83.1 %.


Assuntos
Vacinas contra COVID-19 , COVID-19 , Vacinas de Produtos Inativados , Criança , Humanos , Pré-Escolar , COVID-19/prevenção & controle , Hong Kong/epidemiologia , Pandemias
2.
Trop Biomed ; 40(3): 295-300, 2023 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-37897161

RESUMO

In Malaysia presently, the main cause of human malaria is by the zoonotic monkey parasite Plasmodium knowlesi. A previous study has suggested that the P. knowlesi merozoite surface protein 1 (Pkmsp-1) block IV to be a suitable multiplicity of infection (MOI) genotyping marker for knowlesimalaria. This study therefore aimed to investigate the usefulness of Pkmsp-1 block IV in assessing the MOI of P. knowlesi in clinical isolates from Malaysia. Two allele-specific PCR primer pairs targeting the two allelic families of block IV (T1 and T2) were designed, and used to genotype P. knowlesi in 200 blood samples (100 from Peninsular Malaysia and 100 from Malaysian Borneo). Results showed that the mean MOI in Malaysian Borneo was slightly higher as compared to Peninsular Malaysia (1.58 and 1.40, respectively). Almost half of the total blood samples from Malaysian Borneo (52%) had polyclonal infections (i.e., more than one allele of any family type) as compared to Peninsular Malaysia (33%) samples. The T1 allelic family was more prevalent in Peninsular Malaysia (n=75) than in Malaysian Borneo (n=60). The T2 allelic family, however, was more prevalent in the Malaysian Borneo (n=87 vs n=53 respectively). This study shows that the single locus Pkmsp-1 block IV can serve as a simple alternative genetic marker for estimating knowlesi malaria MOI in a population. Future MOI studies should focus on macaque populations as macaques are the natural host of P. knowlesi.


Assuntos
Malária , Plasmodium knowlesi , Humanos , Variação Genética , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Malásia , Genótipo , Malária/veterinária , Malária/parasitologia
3.
Trop Biomed ; 40(1): 37-44, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-37356002

RESUMO

Circumsporozoite protein (CSP) central repeat region is one of the main target regions of the RTS,S/AS01 vaccine for falciparum infection as it consists of immunodominant B cell epitopes. However, there is a lack of study for P. knowlesi CSP central repeat region. This study aims to characterise the CSP repeat motifs of P. knowlesi isolates in Peninsular Malaysia. CSP repeat motifs of 64 P. knowlesi isolates were identified using Rapid Automatic Detection and Alignment of Repeats (RADAR). Antigenicity of the repeat motifs and linear B cell epitopes were predicted using VaxiJen 2.0, BepiPred-2.0 and BCPred, respectively. A total of 35 dominant repeat motifs were identified. The repeat motif "AGQPQAQGDGANAGQPQAQGDGAN" has the highest repeat frequency (n=15) and antigenicity index of 1.7986. All the repeat regions were predicted as B cell epitopes. In silico approaches revealed that all repeat motifs were antigenic and consisted of B cell epitopes which could be designed as knowlesi malaria vaccine.


Assuntos
Vacinas Antimaláricas , Plasmodium knowlesi , Epitopos de Linfócito B , Proteínas de Protozoários , Vacinas Antimaláricas/genética , Vacinas Antimaláricas/metabolismo , Plasmodium falciparum
4.
Trop Biomed ; 39(2): 209-214, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35838092

RESUMO

Circumsporozoite protein (CSP) is a sporozoite major surface protein of Plasmodium species. The protein showed promising protection level as a vaccine candidate against Plasmodium falciparum infection. There is a lack of studies on P. knowlesi CSP (PkCSP) as a vaccine candidate due to the high polymorphic characteristic of central repeat region. Recent studies showed the protein has a relatively conserved region at the C-terminal, which consists of T- and B-cell epitopes. This could be the target region for vaccine development against the pre-erythrocytic stage of the parasite. In this study, recombinant PkCSP was expressed using Escherichia coli system. Recombinant PkCSP was immunized in animal models and the antiserum was evaluated using immunoblot analysis. Results showed that PkCSP can be successfully expressed using the bacterial system. Endpoint titre of the antiserum were ranged up to 1:819200. Immunoblot analysis showed the antiserum recognized recombinant PkCSP but not total protein extract from P. knowlesi erythrocytic stage. In conclusion, PkCSP could elicit strong immune response in animal models. However, serum antibodies could not recognize protein from the parasite's erythrocytic stage extract indicating it is not expressed at the erythrocytic stage. Therefore, PkCSP remains as a potential pre-erythrocytic vaccine candidate against P. knowlesi infection.


Assuntos
Malária Falciparum , Plasmodium knowlesi , Animais , Anticorpos Antiprotozoários , Antígenos de Protozoários/genética , Clonagem Molecular , Plasmodium falciparum , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Proteínas de Protozoários/genética , Esporozoítos/metabolismo
5.
Trop Biomed ; 39(1): 66-72, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-35507927

RESUMO

Recent reports of natural human infection by Plasmodium cynomolgi indicate the increased risk of zoonotic transmission by this simian parasite. The P. cynomolgi Duffy binding protein 2 (PcDBP2) has a potential role in the invasion pathway of host erythrocytes, and it is a possible vaccine candidate against cynomolgi malaria. This study investigates the genetic diversity, haplotypes, and natural selection of PcDBP2 region II from isolates collected from wild macaques in Peninsular Malaysia. Blood samples from 50 P. cynomolgi -infected wild macaques were used in the study. Genomic DNA extracted from the blood samples was used as template for PCR amplification of the PcDBP2 region II. The amplicons were cloned into a plasmid vector and sequenced. MEGA X and DnaSP ver.6.12.03 programmes were used to analyse the DNA sequences. A genealogical relationship of PcDBP2 region II were determined using haplotype network tree on NETWORK ver.10.2. Result showed high genetic diversity (ð = 0.017 ± 0.002; Hd = 1.000 ± 0.001) of the PcDBP2 region II. The Z-test indicates a purifying selection, with population expansion as shown in Tajima's D analysis. A total of 146 haplotypes of PcDBP2 region II were observed. Phylogenetic tree analysis showed that these haplotypes were grouped into three allelic types (136 for Strain B type, 9 for Berok type, and 1 recombinant type). In the haplotype network, PcDBP2 region II revealed no geographical groupings but was divided into two distinct clusters.


Assuntos
Plasmodium knowlesi , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Variação Genética , Macaca/metabolismo , Malásia , Filogenia , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo
8.
Vaccine ; 40(7): 967-969, 2022 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-35063284

RESUMO

Vaccines against COVID-19 are now available for adolescents in Hong Kong but vaccine hesitancy is a major barrier to herd immunity. This survey study explores Hong Kong adolescents' attitudes towards the COVID-19 vaccination. 2609 adolescents from across Hong Kong completed an online survey focused on the intent to vaccinate and the reasons for their choice. 39% of adolescents intended to take the COVID-19 vaccination and significant factors for this decision include: having at least one parent vaccinated, knowing somebody diagnosed with COVID-19 and receiving the influenza vaccine. Adolescents' major concerns were either the safety and efficacy of the vaccine or the risk of infection. This study has proved that even in adolescents the vaccine hesitancy model is prominent with adolescents' intentions highly related to confidence in the vaccine and perception of disease risk. Future interventions should target these specific concerns to ensure adolescents are well educated to overcome vaccine hesitancy.


Assuntos
COVID-19 , Vacinas contra Influenza , Adolescente , Atitude , Vacinas contra COVID-19 , Estudos Transversais , Humanos , SARS-CoV-2 , Vacinação
9.
Trop Biomed ; 39(4): 504-510, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36602208

RESUMO

The Plasmodium knowlesi secreted protein with an altered thrombospondin repeat (PkSPATR) is an important protein that helps in the parasite's invasion into the host cell. This protein has been regarded as one of the potential vaccine candidates against P. knowlesi infection. This study investigates the genetic diversity and natural selection of PkSPATR gene of P. knowlesi clinical isolates from Malaysia. PCR amplification of the full length PkSPATR gene was performed on 60 blood samples of infected P. knowlesi patients from Peninsular Malaysia and Malaysian Borneo. The amplified PCR products were cloned and sequenced. Sequence analysis of PkSPATR from Malaysia showed higher nucleotide diversity (CDS p: 0.01462) than previously reported Plasmodium vivax PvSPATR (p = 0.0003). PkSPATR from Peninsular Malaysia was observed to have slightly higher diversity (CDS p: 0.01307) than those from Malaysian Borneo (CDS p: 0.01212). Natural selection analysis on PkSPATR indicated significant purifying selection. Multiple amino acid sequence alignment revealed 69 polymorphic sites. The phylogenetic tree and haplotype network did not show any distinct clustering of PkSPATR. The low genetic diversity level, natural selection and absence of clustering implied functional constrains of the PkSPATR protein.


Assuntos
Plasmodium knowlesi , Proteínas de Protozoários , Humanos , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Variação Genética , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Malásia , Trombospondinas/genética , Trombospondinas/metabolismo , Filogenia
10.
Trop Biomed ; 38(3): 248-253, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34362867

RESUMO

Through the regional control programme, Malaysia has been successfully reducing the incidence of Plasmodium falciparum and Plasmodium vivax infections. However, the incidence of zoonotic malaria Plasmodium knowlesi infection is increasing and now has been the major cause of malaria in Malaysia especially Malaysian Borneo. The emergence of knowlesi infection has threatened the malaria elimination programme which the government aims to reduce the overall malaria infections by 2020. Unlike other benign human Plasmodium spp., P. knowlesi can cause fatal infections. The aim of this study was to determine the incidence and distribution of five human malaria parasites including P. knowlesi in Peninsular Malaysia and Malaysian Borneo. A total of 112 blood samples were collected from seven states and district hospitals in Peninsular Malaysia and Malaysian Borneo from year 2015 to 2016. The samples were examined by microscopy and further confirmed by nested PCR assay targeting 18S rRNA gene of Plasmodium spp. Following the nested PCR assays, a total of 54 (48.2%) samples were positive for P. knowlesi infections, 12 (10.7%) cases were positive for P. vivax infections, followed by 7 (6.3%) cases of P. falciparum and 4 (3.5%) cases of P. malariae. There were 3 cases (2.7%) of mixed infections (P. knowlesi/P. vivax). However, no cases were identified as P. ovale. A total of 32 (28.6%) cases were found as negative infections. LoopMediated Isothermal Amplification Assay (LAMP) was performed to confirm inconclusive results produced by microscopy and nested PCR. P. knowlesi showed the highest prevalence in Sarawak (n= 30), Sabah (n=13), Pulau Pinang (n=5) and Pahang (n=6). PCR and LAMP was not able to detect a large number of microscopy positive samples due to DNA degradation during storage and shipping. Among all the states involved in this study, the highest prevalence of P. knowlesi infection was found in Sabah and Sarawak.


Assuntos
Malária , Plasmodium knowlesi , Hospitais , Humanos , Incidência , Malária/epidemiologia , Malária Falciparum , Malária Vivax , Malásia/epidemiologia , Plasmodium knowlesi/genética , Plasmodium knowlesi/isolamento & purificação
12.
Trop Biomed ; 38(2): 143-148, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34172703

RESUMO

Normocyte binding protein Xa (NBPXa) has been implied to play a significant role in parasite invasion of human erythrocytes. Previous phylogenetic studies have reported the existence of three types of NBPXa for Plasmodium knowlesi (PkNBPXa). PkNBPXa region II (PkNBPXaII) of type 1, type 2 and type 3 were expressed on mammalian cell surface and interacted with human and macaque (Macaca fascicularis) erythrocytes. The binding activities of PkNBPXaII towards human and macaque erythrocytes were evaluated using erythrocyte-binding assay (EBA). Three parameters were evaluated to achieve the optimal protein expression of PkNBPXaII and erythrocyte binding activity in EBA: types of mammalian cells, post transfection time and erythrocyte incubation time. COS-7, HEK-293, and CHO-K1 cells showed successful expression of PkNBPXaII, despite the protein expression is weak compared to the positive control. COS-7 was used in EBA. All three types of PkNBPXaII showed rosette formation with macaque erythrocytes but not with human erythrocytes. Future studies to enhance the PkNBPXaII expression on surface of mammalian cells is indeed needed in order to elucidate the specific role of PkNBPXaII in erythrocytes invasion.


Assuntos
Eritrócitos/parasitologia , Proteínas de Membrana/metabolismo , Plasmodium knowlesi , Proteínas de Protozoários/metabolismo , Animais , Antígenos de Protozoários , Células CHO , Células COS , Chlorocebus aethiops , Cricetulus , Eritrócitos/metabolismo , Células HEK293 , Humanos , Proteínas de Membrana/genética , Filogenia , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Ligação Proteica , Proteínas de Protozoários/genética
13.
Trop Biomed ; 38(2): 159-164, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34172705

RESUMO

The Plasmodium knowlesi apical membrane antigen-1 (PkAMA-1) plays an important role in the invasion of the parasite into its host erythrocyte, and it has been regarded as a potential vaccine candidate against human knowlesi malaria. This study investigates genetic diversity and natural selection of the full length PkAMA-1 of P. knowlesi clinical isolates from Peninsular Malaysia. Blood samples were collected from P. knowlesi malaria patients from Peninsular Malaysia. The PkAMA-1 gene was amplified from DNA samples using PCR, cloned into a plasmid vector and sequenced. Results showed that nucleotide diversity of the full length PkAMA-1 from Peninsular Malaysia isolates (π: 0.006) was almost similar to that of Sarawak (π: 0.005) and Sabah (π: 0.004) isolates reported in other studies. Deeper analysis revealed Domain I (π: 0.007) in the PkAMA-1 had the highest diversity as compared to Domain II (π: 0.004) and Domain III (π: 0.003). Z-test indicated negative (purifying) selection of the gene. Combined alignment analysis at the amino acid level for the Peninsular Malaysia and Sarawak PkAMA-1 sequences revealed 34 polymorphic sites. Thirty-one of these sites were dimorphic, and 3 were trimorphic. The amino acid sequences could be categorised into 31 haplotypes. In the haplotype network, PkAMA-1 from Peninsular Malaysia and Sarawak were separated into two groups.


Assuntos
Antígenos de Protozoários/genética , Variação Genética , Proteínas de Membrana/genética , Plasmodium knowlesi , Proteínas de Protozoários/genética , Haplótipos , Humanos , Malária/parasitologia , Malásia , Plasmodium knowlesi/genética
14.
Trop Biomed ; 38(1): 33-35, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33797521

RESUMO

In recent years, increasing cases of Plasmodium vivax complications had been reported all over the world. This former benign Plasmodium species is now recognized to be one of the human malaria parasites that can produce severe disease. In this article, we report two cases of sub-microscopic P. vivax malaria confirmed by PCR. Both patients were asymptomatic before treatment. They showed unusual presentations few days after initiation of antimalarial treatment. Both patients had subsequently completed antimalarial treatment and recovered completely.


Assuntos
Antimaláricos/uso terapêutico , Malária Vivax/complicações , Injúria Renal Aguda/parasitologia , Adolescente , Adulto , Etnicidade , Feminino , Humanos , Pneumopatias/parasitologia , Malária Vivax/tratamento farmacológico , Plasmodium vivax
15.
Trop Biomed ; 38(1): 142-144, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33797537

RESUMO

Enteral myiasis or intestinal myiasis is acquired by ingesting food or water contaminated with dipteran fly eggs or larvae. Here, we describe a patient with intestinal myiasis presenting with acute dysentery caused by the larva of Hermetia illucens. The larva was identified morphologically, and its species confirmed through molecular analysis using polymerase chain reaction and sequencing based on mitochondrial cytochrome c oxidase subunit I gene (COI).


Assuntos
Disenteria/parasitologia , Miíase/complicações , Adulto , Humanos , Masculino
17.
Asian Pac J Allergy Immunol ; 39(4): 241-248, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-31310149

RESUMO

BACKGROUND: Peanut allergy is common in Chinese children, yet the most predictive diagnostic cut-offs for skin prick test (SPT) and blood testing in this population are unclear. OBJECTIVES: We aimed to determine the optimal cut-off values for whole-peanut SPT, specific IgE (sIgE) and component-resolved diagnostics (CRD) for Chinese children based on outcomes of open oral food challenges (OFC) to peanut. METHODS: We recruited ethnic-Chinese patients 1-18 years old who were suspected of having peanut allergy based on a history of reactions after exposure or sensitization although peanut naïve. Considering the AUC value of 0.8, 80% power and 5% level of significance with two tails, 26 patients were needed. Sensitivities, specificities, positive and negative predictive values, and receiver operating characteristic curves (ROCs) and their area-under-curves (AUCs) for SPT, peanut sIgE, and CRD were compared. RESULTS: Thirty-one subjects participated. Only SPT reached statistical significance (AUC 0.91, p = 0.0001), but not the other tests. Seven retrospective data were added to optimize the power. SPT remained to be the best predictor, followed by Ara h 2 sIgE (AUC 0.72, p = 0.02). An SPT wheal size of 3 mm and Ara h 2 sIgE of 0.14 kU(A)/L yielded the highest Youden's index. The specificity of SPT and Ara h 2 sIgE reached 94% at 6 mm and 0.74 kU(A)/L, respectively. Comparisons of ROCs revealed that SPT was significantly better than Ara h 2 sIgE (p = 0.03) and whole-peanut sIgE (AUC 0.61, p = 0.26). CONCLUSION: In Chinese children, SPT appeared to be the best predictor for peanut allergy, followed by Ara h 2 sIgE.

18.
Trop Biomed ; 38(4): 590-593, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-35001925

RESUMO

Ectoparasitic infestations including pediculosis capitis are common in people of disadvantaged communities as they live in overcrowded institutions, a condition that often favourable for disease transmission. In this study, we evaluated the prevalence of head lice infestation among disadvantaged children aged between five to 14 years-old living in five poor conditions located across the Klang Valley, Malaysia. Of total 335 children examined, 14% were positively infected with head lice. Molecular analysis using the universal cytochrome c oxidase subunit I ( COI) barcoding gene on total of 167 head lice collected in this study indicated they are belonging to the A and C clades; confirming the global distribution of clade A and expansion of clade C in Southeast Asia, which is reported for the first time in Malaysia.


Assuntos
Infestações por Piolhos , Pediculus , Adolescente , Animais , Criança , Pré-Escolar , Humanos , Infestações por Piolhos/epidemiologia , Malásia/epidemiologia , Pediculus/genética , Inquéritos e Questionários , Populações Vulneráveis
19.
Trop Biomed ; 38(4): 594-604, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-35001926

RESUMO

The United Nations High Commissioner for Refugees (UNHCR) reports over 80 million people are displaced worldwide with approximately 26.3 million categorized as refugees and over a million residing temporarily in South East Asia. Despite the lack of national legislative framework in place for refugees and asylum seekers (RAS), Malaysia hosts approximately 178,140 as registered with UNHCR and the majority originate from Myanmar. In this review, we examine refugees from South East Asia, particularly from Myanmar that have contributed to the largest influx of refugees to this region with a focus on their health status. The present study traces barriers to the health care of refugees in the country of asylum and also the challenges faced by these communities in accessing health services.


Assuntos
Nível de Saúde , Refugiados , Ásia Oriental/etnologia , Humanos , Malásia/epidemiologia , Mianmar/etnologia
20.
Front Immunol ; 11: 1411, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32765500

RESUMO

The clinical experience gathered throughout the years has raised awareness of primary immunodeficiency diseases (PIDD). T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) assays for thymic and bone marrow outputs measurement have been widely implemented in newborn screening (NBS) programs for Severe Combined Immunodeficiency. The potential applications of combined TREC and KREC assay in PIDD diagnosis and immune reconstitution monitoring in non-neonatal patients have been suggested. Given that ethnicity, gender, and age can contribute to variations in immunity, defining the reference intervals of TREC and KREC levels in the local population is crucial for setting up cut-offs for PIDD diagnosis. In this retrospective study, 479 healthy Chinese sibling donors (240 males and 239 females; age range: 1 month-74 years) from Hong Kong were tested for TREC and KREC levels using a simultaneous quantitative real-time PCR assay. Age-specific 5th-95th percentile reference intervals of TREC and KREC levels (expressed in copies per µL blood and copies per 106 cells) were established in both pediatric and adult age groups. Significant inverse correlations between age and both TREC and KREC levels were observed in the pediatric age group. A significant higher KREC level was observed in females than males after 9-12 years of age but not for TREC. Low TREC or KREC levels were detected in patients diagnosed with mild or severe PIDD. This assay with the established local reference intervals would allow accurate diagnosis of PIDD, and potentially monitoring immune reconstitution following haematopoietic stem cell transplantation or highly active anti-retroviral therapy in the future.


Assuntos
Linfócitos B , Biomarcadores/sangue , DNA Circular/sangue , Imunodeficiência Combinada Severa/diagnóstico , Linfócitos T , Adolescente , Criança , Pré-Escolar , Feminino , Voluntários Saudáveis , Hong Kong , Humanos , Lactente , Recém-Nascido , Masculino , Triagem Neonatal/métodos , Valores de Referência
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA