Genetic diversity of merozoite surface protein-1 C-terminal 42 kDa of Plasmodium falciparum (PfMSP-142) may be greater than previously known in global isolates

Targeting the Plasmodium falciparum proteome and organelles for potential antimalarial drug candidates

There is an unmet need to unearth alternative treatment options for malaria, wherein this quest is more pressing in recent times due to high morbidity and mortality data arising mostly from the endemic countries coupled with partial diversion of attention from the disease in view of the SARS-Cov-2 pandemic. Available therapeutic options for malaria have been severely threatened with the emergence of resistance to almost all the antimalarial drugs by the Plasmodium falciparum parasite in humans, which is a worrying situation. Artemisinin combination therapies (ACT) that have so far been the mainstay of malaria have encountered resistance by malaria parasite in South East Asia, which is regarded as a notorious ground zero for the emergence of resistance to antimalarial drugs. This review analyzes a few key druggable targets for the parasite and the potential of specific inhibitors to mitigate the emerging antimalarial drug resistance problem by providing a concise assessment of the essential proteins of the malaria parasite that could serve as targets. Moreover, this work provides a summary of the advances made in malaria parasite biology and the potential to leverage these findings for antimalarial drug production.

Genetic polymorphism of merozoite surface protein-3 in Myanmar Plasmodium falciparum field isolates

Background

Plasmodium falciparum merozoite surface protein-3 (PfMSP-3) is a target of naturally acquired immunity against P. falciparum infection and is a promising vaccine candidate because of its critical role in the erythrocyte invasion of the parasite. Understanding the genetic diversity of pfmsp-3 is important for recognizing genetic nature and evolutionary aspect of the gene in the natural P. falciparum population and for designing an effective vaccine based on the antigen.

Methods

Blood samples collected from P. falciparum-infected patients in Naung Cho and Pyin Oo Lwin, Myanmar, in 2015 were used in this study. The pfmsp-3 was amplified by polymerase chain reaction, cloned, and sequenced. Genetic polymorphism and natural selection of Myanmar pfmsp-3 were analysed using the programs DNASTAR, MEGA6, and DnaSP 5.10.00. Genetic diversity and natural selection of the global pfmsp-3 were also comparatively analysed.

Results

Myanmar pfmsp-3 displayed 2 different alleles, 3D7 and K1. The 3D7 allelic type was predominant in the population, but genetic polymorphism was less diverse than for the K1 allelic type. Polymorphic characters in both allelic types were caused by amino acid substitutions, insertions, and deletions. Amino acid substitutions were mainly occurred at the alanine heptad repeat domains, whereas most insertions and deletions were found at the glutamate rich domain. Overall patterns of amino acid polymorphisms detected in Myanmar pfmsp-3 were similar in the global pfmsp-3 population, but novel amino acid changes were observed in Myanmar pfmsp-3 with low frequencies. Complicated patterns of natural selection and recombination events were predicted in the global pfmsp-3, which may act as major driving forces to maintain and generate genetic diversity of the global pfmsp-3 population.

Conclusion

Global pfmsp-3 revealed genetic polymorphisms, suggesting that the functional and structural consequences of the polymorphisms should be considered in designing a vaccine based on PfMSP-3. Further examination of genetic diversity of pfmsp-3 in the global P. falciparum population is necessary to gain in-depth insight for the population structure and evolutionary aspect of global pfmsp-3.

Changing pattern of the genetic diversities of Plasmodium falciparum merozoite surface protein-1 and merozoite surface protein-2 in Myanmar isolates

BACKGROUND

Plasmodium falciparum merozoite surface protein-1 (PfMSP-1) and -2 (PfMSP-2) are major blood-stage vaccine candidate antigens. Understanding the genetic diversity of the genes, pfmsp-1 and pfmsp-2, is important for recognizing the genetic structure of P. falciparum, and the development of an effective vaccine based on the antigens. In this study, the genetic diversities of pfmsp-1 and pfmsp-2 in the Myanmar P. falciparum were analysed.

METHODS

The pfmsp-1 block 2 and pfmsp-2 block 3 regions were amplified by polymerase chain reaction from blood samples collected from Myanmar patients who were infected with P. falciparum in 2013-2015. The amplified gene fragments were cloned into a T&A vector, and sequenced. Sequence analysis of Myanmar pfmsp-1 block 2 and pfmsp-2 block 3 was performed to identify the genetic diversity of the regions. The temporal genetic changes of both pfmsp-1 and pfmsp-2 in the Myanmar P. falciparum population, as well as the polymorphic diversity in the publicly available global pfmsp-1 and pfmsp-2, were also comparatively analysed.

RESULTS

High levels of genetic diversity of pfmsp-1 and pfmsp-2 were observed in the Myanmar P. falciparum isolates. Twenty-eight different alleles of pfmsp-1 (8 for K1 type, 14 for MAD20 type, and 6 for RO33 type) and 59 distinct alleles of pfmsp-2 (18 for FC27, and 41 for 3D7 type) were identified in the Myanmar P. falciparum population in amino acid level. Comparative analyses of the genetic diversity of the Myanmar pfmsp-1 and pfmsp-2 alleles in the recent (2013-2015) and past (2004-2006) Myanmar P. falciparum populations indicated the dynamic genetic expansion of the pfmsp-1 and pfmsp-2 in recent years, suggesting that a high level of genetic differentiation and recombination of the two genes may be maintained. Population genetic structure analysis of the global pfmsp-1 and pfmsp-2 also suggested that a high level of genetic diversity of the two genes was found in the global P. falciparum population.

CONCLUSION

Despite the recent remarkable decline of malaria cases, the Myanmar P. falciparum population still remains of sufficient size to allow the generation and maintenance of genetic diversity. The high level of genetic diversity of pfmsp-1 and pfmsp-2 in the global P. falciparum population emphasizes the necessity for continuous monitoring of the genetic diversity of the genes for better understanding of the genetic make-up and evolutionary aspect of the genes in the global P. falciparum population.

Diversity analysis of MSP1 identifies conserved epitope organization in block 2 amidst high sequence variability in Indian Plasmodium falciparum isolates

Background

Despite its immunogenicity, the polymorphic nature of merozoite surface protein 1, an important vaccine candidate for Plasmodium falciparum malaria, remains a concern. This study analyses the impact of genetic variability and parasite population structure on epitope organization of different MSP1 segments.

Methods

Altogether 98 blood samples collected from P. falciparum infected mild and severe malaria patients of Chhattisgarh and West Bengal were used to sequence regions encoding block 2 and MSP1-19 of msp1. Sequences were analysed using MEGA7, DnaSPv5, Arlequin3.5 and BepiPred.

Results

All three major MSP1 block 2 allele families namely K1, MAD20 and RO33 were detected in the samples and they together resulted in 41 indel variants. Chhattisgarh samples displayed an average MOI of 2.07 ± 1.59 which was higher in mild malaria and in age group < 18 years. Ultra-structure of block 2 alleles revealed that mutation and repeat expansion were two major mechanisms responsible for allelic variability of K1 and MAD20. Regions flanking block 2 were highly variable in Chhattisgarh with average mismatch differences (k) ranging from 1.198 to 5.156 for three families. In contrast, region encompassing MSP1-19 exhibited limited heterogeneity (k_Chhattisgarh = 1.45, k_{West Bengal} = 1.363). Of the 50 possible B cell linear epitopes predicted from block 2 variants, 94.9% (131 of 138) of the parasites could be represented by three conserved antigens.

Conclusions

Present data indicates that natural selection and transmission intensity jointly play a role in controlling allelic diversity of MSP1 in Indian parasite isolates. Despite remarkable genetic variability, a limited number of predominant and conserved epitopes are present in Indian parasite isolates reinstating the importance of MSP1 as a promising malaria vaccine candidate.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2592-y) contains supplementary material, which is available to authorized users.