Anti-Plasmodium vivax merozoite surface protein 3 ϒ (PvMSP3 ϒ) antibodies upon natural infection.

Merozoite surface protein 3 of Plasmodium vivax (PvMSP3) contains a repertoire of protein members with unique sequence organization. While the biological functions of these proteins await elucidation, PvMSP3 has been suggested to be potential vaccine targets. To date, studies on natural immune responses to this protein family have been confined to two members, PvMSP3α and PvMSP3ß. This study analyzed natural IgG antibody responses to PvMSP3γ recombinant proteins derived from two variants: one containing insert blocks (CT1230nF) and the other without insert domain (NR25nF). The former variant was also expressed as two subfragment proteins: one encompassing variable domain I and insert block A (CT1230N) and the other spanning from insert block B to conserved block III (CT1230C). Serum samples were obtained from 246 symptomatic vivax malaria patients in Tak (n = 50) and Ubon Ratchathani (n = 196) Provinces. In total, 176 (71.5%) patients could mount antibodies to at least one recombinant PvMSP3γ antigen. IgG antibodies directed against antigens CT1230nF, CT1230N, CT1230C and NR25nF occurred in 96.6%, 61.4%, 71.6% and 68.2% of samples, respectively, suggesting the widespread occurrence of B-cell epitopes across PvMSP3γ. The rates of seropositivity seemed to correlate with the number of previous malaria episodes. Isotype analysis of anti-PvMSP3γ antibodies has shown predominant cytophilic subclass responses, accounting for 75.4-81.7% for IgG1 and 63.6-77.5% for IgG3. Comparing with previous studies in the same cohort, the numbers of serum samples reactive to antigens derived from P. vivax merozoite surface protein 9 (PvMSP9) and thrombospondin-related anonymous protein (PvTRAP) were higher than those to PvMSP3γ, being 92.7% and 87.0% versus 71.5%, respectively. Three (1.22%) serum samples were nonresponsive to all these malarial proteins. Nevertheless, the relevance of naturally acquired antibodies to PvMSP3γ in host protection requires further studies.

The effectiveness of community-based interprofessional education for undergraduate medical and health promotion students.

BACKGROUND: Community-based interprofessional education (CBIPE) has been proven effective in enhancing the interprofessional competencies of medical and health professional students. However, there is a lack of evaluation on the impact of experiential CBIPE among undergraduate medical and health promotion students in Thailand. Therefore, the objective of this study is to assess the influence of CBIPE learning on the collaborative competencies of these students. METHODS: A one-group pre-posttest design in 193 (152 medical students and 41 health promotion) students were involved in the CBIPE program, later divided into 12 groups. Data was collected by direct observations of mentors using the Interprofessional Collaborative Competencies Attainment Survey (ICCAS). The Wilcoxon matched-pairs signed-rank test was conducted to evaluate the effectiveness of the CBIPE program. RESULTS: A total of 175 (90.67%) completed ICCAS and satisfaction questions before and after the CBIPE program. The mean age of respondents was 20.29 ± 1.63 years; 60.57% were women and 39.43% were men. The results showed a significant increase in collaborative competencies before and after the 2-week course. Gender-stratified analysis showed an improvement after CBIPE training for all subscales in women, while the communication, collaboration, conflict management, and functioning team skills segment score was significantly higher in the post-assessment among men. CONCLUSION: The implementation of CBIPE learning was successful in enhancing collaborative competencies among both medical and health promotion students. These findings will provide valuable insights for the design and improvement of CBIPE learning programs in other universities.

Genotyping of Entamoeba nuttalli strains from the wild rhesus macaques of Myanmar and comparison with those from the wild rhesus macaques of Nepal and China.

Entamoeba nuttalli found in macaques is phylogenetically the closest species to Entamoeba histolytica and is potentially pathogenic. In this study, the prevalence of Entamoeba infections was examined in wild rhesus macaques by examining 73 and 90 fecal samples collected from two sites, Popa Taung Kalat (PTK) and Pho Win Taung (PWT), in Myanmar. The positive rates of E. nuttalli detected using PCR were 49% and 31% in PTK and PWT, respectively, but no infections of E. histolytica and E. moshkovskii were found. Entamoeba dispar was detected in 6% of samples only from PWT. Positive rates of E. chattoni and E. coli were both 70% in PWT and 67% and 79% in PTK, respectively. Six E. nuttalli strains from PTK and eight from PWT were obtained in the culture with xenic medium and then, one and two strains, respectively, were axenized and finally cloned. The genotypic analysis of serine-rich protein genes revealed two genotypes each in both sites. The genotypes found in five of six strains from PTK were similar to those from the strains found in Nepal, whereas the remaining one from PTK and two from PWT were similar to those obtained from macaques in China. The sequence of the 18S rDNA of strains with these four genotypes was identical to that of the strains from China. Six loci of tRNA-linked short tandem repeats were analyzed for further genotyping of the strains. Although there were two types in locus A-L in PTK isolates, one of each type for PTK and PWT was found in the other loci, including locus A-L in PWT strains. These results demonstrated that the E. nuttalli strains from Myanmar are closer to the strains from macaques in China rather than those from macaques in Nepal.

Correction: Spatial variation in genetic diversity and natural selection on the thrombospondin-related adhesive protein locus of Plasmodium vivax (PvTRAP).

[This corrects the article DOI: 10.1371/journal.pone.0110463.].

Naturally acquired IgG antibodies to thrombospondin-related anonymous protein of Plasmodium vivax (PvTRAP) in Thailand predominantly elicit immunological cross-reactivity.

BACKGROUND: Thrombospondin-related anonymous protein (TRAP) is a prime candidate for a malaria vaccine. Antibodies to Plasmodium vivax TRAP (PvTRAP) occur upon natural infection while specific antigenic domains remain to be addressed. METHODS: The PvTRAP sequences were determined from 73 P. vivax isolates from Tak and Ubon Ratchathani provinces collected in 2013. The recombinant proteins representing four variants each for domain II (A domain) and domain IV (thrombospondin repeat region) of PvTRAP circulating in these areas were used as antigens in enzyme-linked immunosorbent assay against 246 serum samples from P. vivax-infected patients in both provinces collected during 2013 and 2014. RESULTS: The prevalence of total IgG antibodies to at least one variant antigen of domain II and domain IV was 63.8% and 71.5%, respectively. Differential IgG antibody responses to these variant antigens of each domain were observed. Total IgG antibody responses to the variant antigens of each domain upon pairwise comparisons were highly correlated, suggesting immunological cross-reactivity in the majority of serum samples. A smaller proportion of serum samples contained non-cross-reactive antibodies to variants of each domain; particularly domain II in which amino acid differences significantly influenced antibody recognition. Previous malaria exposure positively affected antibody responses to domain IV. Positive seroconversion and rising antibody titres occurred within a few weeks after resolution of infections. CONCLUSIONS: Both domains II and IV are targets of naturally acquired IgG antibodies. Despite sequence variation in these domains, most antibody responses were cross-reactive. A cross-sectional evaluation of antibodies to PvTRAP during acute infection could underestimate the seroprevalence.

Spatial variation in genetic diversity and natural selection on the thrombospondin-related adhesive protein locus of Plasmodium vivax (PvTRAP).

Thrombospondin-related adhesive protein (TRAP) of malaria parasites is essential for sporozoite motility and invasions into mosquito's salivary gland and vertebrate's hepatocyte; thereby, it is a promising target for pre-erythrocytic vaccine. TRAP of Plasmodium vivax (PvTRAP) exhibits sequence heterogeneity among isolates, an issue relevant to vaccine development. To gain insights into variation in the complete PvTRAP sequences of parasites in Thailand, 114 vivax malaria patients were recruited in 2006-2007 from 4 major endemic provinces bordering Myanmar (Tak in the northwest, n = 30 and Prachuap Khirikhan in the southwest, n = 25), Cambodia (Chanthaburi in the east, n = 29) and Malaysia (Yala and Narathiwat in the south, n = 30). In total, 26 amino acid substitutions were detected and 9 of which were novel, resulting in 44 distinct haplotypes. Haplotype and nucleotide diversities were lowest in southern P. vivax population while higher levels of diversities were observed in other populations. Evidences of positive selection on PvTRAP were demonstrated in domains II and IV and purifying selection in domains I, II and VI. Genetic differentiation was significant between each population except that between populations bordering Myanmar where transmigration was common. Regression analysis of pairwise linearized Fst and geographic distance suggests that P. vivax populations in Thailand have been isolated by distance. Sequence diversity of PvTRAP seems to be temporally stable over one decade in Tak province based on comparison of isolates collected in 1996 (n = 36) and 2006-2007. Besides natural selection, evidences of intragenic recombination have been supported in this study that could maintain and further generate diversity in this locus. It remains to be investigated whether amino acid substitutions in PvTRAP could influence host immune responses although several predicted variant T cell epitopes drastically altered the epitope scores. Knowledge on geographic diversity in PvTRAP constitutes an important basis for vaccine design provided that vaccination largely confers variant-specific immunity.

Clonal diversity in Giardia duodenalis isolates from Thailand: evidences for intragenic recombination and purifying selection at the beta giardin locus.

The beta giardin locus of Giardia duodenalis encodes a structural component of ventral disc and exhibits sequence variation among isolates rendering it a useful marker for genotypic analysis. To determine the distribution of genotypes of G. duodenalis in Thailand and to explore the extent of sequence variation in this locus, we deployed the PCR-RFLP method and sequence analysis of recombinant subclones from 30 clinical isolates. In total, assemblage B was more prevalent than assemblage A. Sequence analysis revealed that 13 isolates had clonal mixtures, comprising three to five distinct sequences per isolate. Nucleotide diversity of assemblage B was greater than that of assemblage A. A striking transitional bias was noted at the first and the third positions of codons in both assemblages; however, they differed in the patterns of nucleotide diversity at 0-fold and 4-fold-degenerate sites. Most amino acid exchanges were conservative in terms of polarity, charge and volume. Both assemblages have evolved under purifying selection as evidenced by a significantly greater number of mean synonymous substitutions per synonymous site (d(S)) than that of nonsynonymous substitutions per nonsynonymous site (d(N)) as well as significant negative Tajima's D values and its related statistics. The significant negative Tajima's D test at nonsynonymous sites further suggests that elimination of slightly deleterious mutations at these sites by purifying selection is ongoing as predicted in the nearly neutral theory. Furthermore, a minimum number of seven recombination sites was detected by the four gamete test in assemblage B, consistent with previous reports on meiotic recombination in G. duodenalis. Therefore, accurate subassemblage assignment of clinical isolates that has practical consequence for disease control could be complicated by the presence of intra-isolate clonal diversity and interallelic recombination.