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. 2021 Feb 12;20(1):86.
doi: 10.1186/s12936-021-03626-0.

Natural infections with different Plasmodium species induce antibodies reactive to a chimeric Plasmodium vivax recombinant protein

Jessica N McCaffery  1 , Balwan Singh  2 , Douglas Nace  2 , Alberto Moreno  1   3 , Venkatachalam Udhayakumar  2 , Eric Rogier  4
Affiliations

Natural infections with different Plasmodium species induce antibodies reactive to a chimeric Plasmodium vivax recombinant protein

Jessica N McCaffery et al. Malar J. .

Abstract

Background: As malaria incidence and transmission in a region decreases, it becomes increasingly difficult to identify areas of active transmission. Improved methods for identifying and monitoring foci of active malaria transmission are needed in areas of low parasite prevalence in order to achieve malaria elimination. Serological assays can provide population-level infection history to inform elimination campaigns.

Methods: A bead-based multiplex antibody detection assay was used to evaluate a chimeric Plasmodium vivax MSP1 protein (PvRMC-MSP1), designed to be broadly immunogenic for use in vaccine studies, to act as a pan-malaria serological tool based on its ability to capture IgG in plasma samples obtained from naturally exposed individuals. Samples from 236 US travellers with PCR confirmed infection status from all four major Plasmodium species infecting humans, Plasmodium falciparum (n = 181), Plasmodium vivax (n = 38), Plasmodium malariae (n = 4), and Plasmodium ovale (n = 13) were tested for IgG capture using PvRMC-MSP1 as well as the four recombinant MSP1-19 kD isoforms representative of these Plasmodium species.

Results: Regardless of infecting Plasmodium species, a large proportion of plasma samples from infected US travellers provided a high assay signal to the PvRMC-MSP1 chimeric protein, with 115 high responders out of 236 samples assessed (48.7%). When grouped by active infection, 38.7% P. falciparum-, 92.1% of P. vivax-, 75.0% P. malariae-, and 53.4% of P. ovale-infected individuals displayed high assay signals in response to PvRMC-MSP1. It was also determined that plasma from P. vivax-infected individuals produced increased assay signals in response to the PvRMC-MSP1 chimera as compared to the recombinant PvMSP1 for 89.5% (34 out of 38) of individuals. PvRMC-MSP1 also showed improved ability to capture IgG antibodies from P. falciparum-infected individuals when compared to the capture by recombinant PvMSP1, with high assay signals observed for 38.7% of P. falciparum-infected travellers in response to PvRMC-MSP1 IgG capture compared to just 1.1% who were high responders to capture by the recombinant PvMSP1 protein.

Conclusions: These results support further study of designed antigens as an approach for increasing sensitivity or broadening binding capacity to improve existing serological tools for determining population-level exposure to Plasmodium species. Including both broad-reacting and Plasmodium species-specific antigen-coated beads in an assay panel could provide a nuanced view of population-level exposure histories, an extensive IgG profile, and detailed seroestimates. A more sensitive serological tool for detection of P. vivax exposure would aid malaria elimination campaigns in co-endemic areas and regions where P. vivax is the dominant parasite.

Keywords: Chimeric protein; Malaria; Multiplex; Plasmodium vivax; Seroepidemiology; Serology.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Schematic of the PvRMC-MSP1 chimeric protein and alignments of orthologous sequences. a The entire length of the chimera shown with T cell epitopes represented as blue boxes with the P. vivax T cell epitope designation (PvT) listed inside each box. b Alignment of PvRMC-MSP1 T cell epitopes with orthologous regions from other human Plasmodium species. c Alignment of 19 kD fragment within PvRMC-MSP1 with MSP119 regions in other human Plasmodium species and the partial 33 kD segment
Fig. 2
Fig. 2
Capture of rabbit and murine anti-PvRMC-MSP1 antibodies with MSP1 proteins from the four Plasmodium species. a IgG assay signal for purified total IgG obtained from rabbits following four immunizations with the PvRMC-MSP1 protein. Median fluorescence intensity minus background (MFI-bg) assay signal is shown for each of the four MSP1 proteins derived from human Plasmodium species in comparison to the PvRMC-MSP1 used for immunization. b IgG assay signal for mouse sera obtained after three immunizations with PvRMC-MSP1 with MSP1 proteins from the four human Plasmodium species. c Plasmodium falciparum NF54-infected red blood cells smeared on glass slides were incubated with sera obtained from immunized rabbits (top), and plasma from individuals living in malaria-endemic regions (bottom). Panels show staining for DNA (DAPI, blue), IgG (AlexaFluor 488, green), and merge. All images are shown at 100 × magnification, and the scale bar indicates 5 µm
Fig. 3
Fig. 3
IgG assay signal for malaria naïve persons for PvRMC-MSP1, PfMSP1, PmMSP1, PoMSP1, and PvMSP1 antigens. Histograms display MFI-bg assay signal for a panel of 92 blood samples from persons never infected with malaria parasites. Note that x-axis is the same for all plots
Fig. 4
Fig. 4
Comparison of MFI-bg assay signal for PvRMC-MSP1 and MSP1s recombinant proteins from the four human Plasmodium species for individuals with active malaria infection. Each point of the scatterplot displays an individual’s MFI-bg IgG response against PvRMC-MSP1 (y-axis) and the MFI-bg response from the same individual against the recombinant MSP1 19 kD proteins from one of the four human Plasmodium species (x-axis). Data was generated using plasma samples obtained from 236 returning US travellers with active malaria infection
Fig. 5
Fig. 5
MFI-bg assay signal for PvRMC-MSP1 or Plasmodium MSP1 19 kD proteins grouped by active infection. Assay signal for IgG binding to a particular antigen is shown by each panel: PvRMC-MSP1 (top left), PvMSP1 (top right), PfMSP1 (bottom left), PmMSP1 (bottom middle), PoMSP1 (bottom right). Persons with active malaria infection categorized by infecting species: P. falciparum (n = 181, blue circles), P. malariae (n = 4, red circles), P. ovale (n = 13, black circles), P. vivax (n = 38, green circles)
Fig. 6
Fig. 6
Recognition of recombinant PvMSP1 and PvRMC-MSP1 by individual P. vivax patients. Assay signals for individual patients are plotted as MFI minus background for both P. vivax MSP1 recombinant proteins tested. Each coloured line represents the change in signal between antigens for a single patient
Fig. 7
Fig. 7
Cross-binding of anti-PfCSP IgG with PvRMC-MSP1. A scatterplot of the PfCSP signal in comparison with PvRMC-MSP1 for the 181 individuals with P. falciparum infection. The dashed reference line is shown as y = x for the assay signal
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References

    1. WHO. World malaria report 2020. Geneva, World Health Organization, 2020.
    1. Geiger C, Agustar HK, Compaoré G, Coulibaly B, Sié A, Becher H, et al. Declining malaria parasite prevalence and trends of asymptomatic parasitaemia in a seasonal transmission setting in north-western Burkina Faso between 2000 and 2009–2012. Malar J. 2013;12:27. doi: 10.1186/1475-2875-12-27. - DOI - PMC - PubMed
    1. Harris I, Sharrock WW, Bain LM, Gray K-A, Bobogare A, Boaz L, et al. A large proportion of asymptomatic Plasmodium infections with low and sub-microscopic parasite densities in the low transmission setting of Temotu Province, Solomon Islands: challenges for malaria diagnostics in an elimination setting. Malar J. 2010;9:254. doi: 10.1186/1475-2875-9-254. - DOI - PMC - PubMed
    1. Lindblade KA, Steinhardt L, Samuels A, Kachur SP, Slutsker L. The silent threat: asymptomatic parasitemia and malaria transmission. Expert Rev Anti Infect Ther. 2013;11:623–639. doi: 10.1586/eri.13.45. - DOI - PubMed
    1. Niang M, Thiam LG, Sane R, Diagne N, Talla C, Doucoure S, et al. Substantial asymptomatic submicroscopic Plasmodium carriage during dry season in low transmission areas in Senegal: Implications for malaria control and elimination. PLoS ONE. 2017;12:e0182189. doi: 10.1371/journal.pone.0182189. - DOI - PMC - PubMed