Background: Relapses of Plasmodium vivax (P. vivax) infections are major causes of malaria morbidity, and tools for distinguishing relapses from reinfections are needed in malaria endemic areas. Methods: Herein, a panel of plasmas of 72 P. vivax-infected pregnant women, of whom 31 had had at least a recurrence of P. vivax infection, was used in a serology for IgM and IgG against 6 P. vivax-merozoite surface protein-1 (P. vivax-MSP1-Block 2) haplotype-specific peptides, in order to identify re-expositions to same haplotypes in the recurrences during the pregnancy. In parallel, we used the amplicon deep sequencing (ADS) with P. vivax-MSP1-Block 2 amplicons of the in eight blood samples of non-pregnant P. vivax-infected patients to identify multi or monoclonal infections based on MSP1-Block-2 haplotypes, and to quantify the reads of different haplotypes between those with multiclonal infections. We synthetized a new panel of overlapping peptides mapping each one of the six P. vivax-MSP1-Block 2 haplotypes and we validated with new IgM and IgG serology. Results: Most pregnant women presented IgM that recognized more than one peptide, thus indicating multiple infections by P. vivax-MSP1-Block 2 haplotypes. The same IgM anti-peptides remained in several women in the recurrent episodes most likely indicates re-exposure to the same haplotype of MSP1 Block 2. The IgG reactivity the IgM to IgG switch were low. The ADS using next-generation sequencing (NGS) identified multi- and monoinfection by P. vivax-MSP1-Block 2 haplotypes. Of eight patients, two of them had had the first P. vivax-infection. Monoinfections with P. vivax-MSP1-Block 2 haplotypes were observed in two prime-infected patients and three of patients with previous malaria. In all P. vivax-MSP1-Block 2 haplotype-monoinfected patients, the reactivity of IgM was observed only against overlapped peptides of the same haplotype detected in ADS, while for IgG, no reactivity was observed for any of the peptides of the same haplotype or the others.We were able to identify multiclonal infections through three haplotypes of P. vivax MSP1 Block 2 in three remaining patients, among which, there was always one majority haplotype that predominated with more of 95% of high-quality reads. The levels of haplotype-specific IgM in the serology correlated with the read ratios of each haplotype, but IgG levels not, including in one of the multiclonal infections, a minority haplotype was recognized with higher levels of IgG than that of the majority one. Conclusion: Our findings suggest that the combination of ADS and serology for P. vivax-MSP1-Block 2 haplotypes may be used as a new tool for distinguishing reinfections from relapses in malaria.
Due to unique biological features, the Plasmodium vivax enhanced its ability to survive and propagate further transmission. The efforts toward malaria control to eradication of the disease should pass through identification of vivax relapses and asymptomatic malaria infections. Objective: Amongst lessons learnt from studies with the Plasmodium vivax MSP1, we could design two novel approaches to be used as diagnostic tools that aim at reducing transmission. Methodology: The quantification and genotyping of parasite based on MSP1 haplotypes using the new generation sequencing and comparison with a haplotype-specific serology against a broad set of Block 2 PvMSP1 peptides. The humoral response based on isotype, subclass and avidity profiles against a set of recombinant proteins PvMSP1, such as MSP1-19, N-terminal PvMSP1 and set of Block 2 PvMSP1 variants. Results: In case of vivax relapse, we developed a methodology to quantify haplotype MSP1 by new generation sequencing and comparing with a haplotype-specific serology against a broad set of peptides to estimate if the haplotype might be originated from hypnozoites. This concept proof needed to be compared with gold-standard microsatellite protocols during a cohort of six months to be used as molecular diagnostic tool especially to evaluate hipnozoiticidal therapies. Moreover, the potential of serologic profiles (isotype, subclass and avidity) against different domains of MSP1 to detect asymptomatic malaria infections. Conclusion: Our lessons learnt from the PvMSP1 ensure us to provide an adequate insight into the epidemiology of malaria to aid elimination efforts.
Numerous mechanisms have been proposed to explain why patients with malaria are more susceptible to bloodstream invasions by Salmonella spp., however there are still several unknown critical factors regarding the pathogenesis of coinfection. From a coinfection model, in which an S. enterica serovar Typhi (S_Typhi) was chosen to challenge mice that had been infected 24 h earlier with Plasmodium berghei ANKA (P.b_ANKA), we evaluated the influence of malaria on cytokine levels, the functional activity of femoral bone marrow-derived macrophages and neutrophils, and intestinal permeability. The cytokine profile over eight days of coinfection showed exacerbation in the cytokines MCP-1, IFNγ and TNFα in relation to the increase seen in animals with malaria. The cytokine profile was associated with a considerably reduced neutrophil and macrophage count and a prominent dysfunction, especially in ex vivo neutrophils in coinfected mice, though without bacterial modulation that could influence the invasion capacity of ex vivo S_Typhi obtained from liver macerate in non-phagocyte cells. Finally, irregularities in the integrity of intestinal tissue evidenced ruptures in the enterocyte layer, a presence of mononuclear leukocytes in the enterocyte layer, an increase of goblet cells in the enterocyte layer and a high volume of leukocyte infiltrate in the sub-mucosa were greatly increased in coinfected animals. Increases of mononuclear leukocytes in the enterocyte layer and volume of leukocyte infiltrate in the sub-mucosa were also seen in monoinfected animals with P. berghei ANKA. Our findings suggest malaria causes a disarrangement of intestinal homeostasis, exacerbation of proinflammatory cytokines and dysfunction in neutrophils that render the host susceptible to bacteremia by Salmonella spp.
As phagocytosis is the first line of defense against malaria, we developed a phagocytosis assay with Plasmodium vivax (P. vivax) merozoites that can be applied to evaluate vaccine candidates. Briefly, after leukocyte removal with loosely packed cellulose powder in a syringe, P. vivax trophozoites matured to the merozoite-rich schizont stages in the presence of the E64 protease inhibitor. The Percoll gradient-enriched schizonts were chemically disrupted to release merozoites that were submitted to merozoite opsonin-dependent phagocytosis in two phagocytic lines with human and mouse antibodies against the N- and C-terminus of P. vivax Merozoite Surface Protein-1 (Nterm-PvMSP1 and MSP119). The resulting assay is simple and efficient for use as a routine phagocytic assay for the evaluation of merozoite stage vaccine candidates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.