Peter Mwitari

Aflatoxin B1 (AFB1), a potent mycotoxin, is known to be an immunotoxic agent that causes various immune system disorders. It can cause immunosuppression by direct toxic effect on the host or by its ability to interfere with the immune response and thereby lead to secondary infections. The immunomodulatory effects of AFB1 and its metabolites have been reported in many studies. Yet, the exact mechanisms responsible for these immunomodulatory effects are still obscure. This review summarizes the current findings on the interaction between AFB1 and the host immune system, while also highlighting other potential mechanisms involved in AFB1-induced immunosuppression. These potential mechanisms include modulation of cytokine production, production of inflammatory mediators and their receptors, activation of pro-inflammatory pathways, alteration in cell surface receptors involved in T cell activation and regulation of apoptosis. The review also discusses the findings on natural products that have been found capable of inhibiting AFB1-induced immunosuppression in various animal models. With the latest exploration of natural products as a solution, the burden of aflatoxicosis in society is likely to subdue. Some of the promising natural products that have been highlighted to have ameliorative effects include grape seed proanthocyanidin extract (GSPE), bentonite clay, smectites clay and Spirulina plantesis among others. Considering the seriousness of aflatoxicosis in the public domain and lack of effective management approaches, there is an urgent need for more research to understand AFB1-induced immunotoxicity and possible remedies.

Aflatoxin B1 (AFB1), a potent mycotoxin, is known to be an immunotoxic agent that causes various immune system disorders. It can cause immunosuppression by direct toxic effect on the host or by its ability to interfere with the immune response and thereby lead to secondary infections. The immunomodulatory effects of AFB1 and its metabolites have been reported in many studies. Yet, the exact mechanisms responsible for these immunomodulatory effects are still obscure. This review summarizes the current findings on the interaction between AFB1 and the host immune system, while also highlighting other potential mechanisms involved in AFB1-induced immunosuppression. These potential mechanisms include modulation of cytokine production, production of inflammatory mediators and their receptors, activation of pro-inflammatory pathways, alteration in cell surface receptors involved in T cell activation and regulation of apoptosis. The review also discusses recent findings on natural products that have been found capable of inhibiting AFB1-induced immunosuppression in various animal models. With the latest exploration of natural products as a solution, the burden of aflatoxicosis in society is likely to subdue. Some of the promising natural products that have been highlighted to have ameliorative effects include grape seed proanthocyanidin extract (GSPE), bentonite clay, NovaSil Clay and Spirulina plantesis among others. Considering the seriousness of aflatoxicosis in the public domain and lack of effective management approaches, there is an urgent need for more research to understand AFB1-induced immunotoxicity and possible remedies.

Background Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ), the long-acting components of the artemisinin-based combination therapies (ACTs), are a cornerstone of malaria treatment in Africa. Studies have shown that PQ, AQ, and LM resistance may arise independently of predicted modes of action. Protein kinases have emerged as mediators of drug action and efficacy in malaria parasites; however, the link between top druggable Plasmodium kinases with LM, PQ, and AQ resistance remains unclear. Using LM, PQ, or AQ-resistant Plasmodium berghei parasites, we have evaluated the association of choline kinase (CK), pantothenate kinase 1 (PANK1), diacylglycerol kinase (DAGK), and phosphatidylinositol-4 kinase (PI4Kβ), and calcium-dependent protein kinase 1 (CDPK1) with LM, PQ, and AQ resistance in Plasmodium berghei ANKA. Methods We used in silico bioinformatics tools to identify ligand-binding motifs, active sites, and sequence conservation across the different parasites. We then used PCR and sequencing analysis to probe for single nucleotide polymorphisms (SNPs) within the predicted functional motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1. Using qPCR analysis, we measured the mRNA amount of PANK1, DAGK, and PI4Kβ at trophozoites and schizonts stages. Results We reveal sequence conservation and unique ligand-binding motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1 across malaria species. DAGK, PANK1, and PI4Kβ possessed nonsynonymous mutations; surprisingly, the mutations only occurred in the AQr parasites. PANK1 acquired Asn394His, while DAGK contained K270R and K292R mutations. PI4Kβ had Asp366Asn, Ser1367Arg, Tyr1394Asn and Asp1423Asn. We show downregulation of PANK1, DAGK, and PI4Kβ in the trophozoites but upregulation at the schizonts stages in the AQr parasites. Conclusions The selective acquisition of the mutations and the differential gene expression in AQ-resistant parasites may signify proteins under AQ pressure. The role of the mutations in the resistant parasites and their impact on drug responses require investigations using reverse genetics techniques in malaria parasites.

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ) are the essential long-acting partner drugs in the artemisinin-based combination therapies (ACTs) treatment regimens globally. The recent report on the emergence of artemisinin-resistant parasites portends an imminent failure of the partner drug in clearing the high residual parasite densities. Understanding the resistance mechanisms to partner drugs remains critical for tracking resistant parasites. Cysteine desulfurase IscS (nfs1), one of the proteins involved in the iron-sulfur (FeS) biogenesis pathway, has been implicated in mediating malaria parasite drug resistance. Methods: Using the rodent malaria parasites Plasmodium berghei ANKA in mice, we assessed whether the nfs1 gene is associated with LM, PQ, and AQ resistance. We first verified the stability of the LM, PQ, and AQ-resistant parasites in the standard 4-Day Suppressive Test. By means of PCR and sequencing analysis, we probed for single nucleotide polymorphisms (SNPs) in the nfs1 gene. Using qPCR, we then measured the expression of the nfs1 gene in resistant parasites relative to the drug-sensitive parent parasites. Results: Our analyses of nfs1 reveal a non-synonymous Gln142Arg mutation in the LM and PQ-resistant parasites. This mutation was not detected in the AQ-resistant parasites. The mRNA quantification of the nfs1 gene reveals differential expression in both LM and PQ-resistant parasites. Conversely, nfs1 expression remained unchanged in the AQ-resistant parasites. Conclusion: Our data suggest that LM and PQ selection pressure induces nonsynonymous mutation and differential expression of the nfs1 gene in Plasmodium berghei. Collectively, these findings provide a premise for investigating LM and PQ resistance mechanisms in both P. berghei and P. falciparum.

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ), the long-acting components of the artemisinin-based combination therapies (ACTs), are a cornerstone of malaria treatment in Africa. Studies have shown that PQ, AQ, and LM resistance may arise independently of predicted modes of action. Protein kinases have emerged as mediators of drug action and efficacy in malaria parasites; however, the link between top druggable Plasmodium kinases with LM, PQ, and AQ resistance remains unclear. Using LM, PQ, or AQ-resistant Plasmodium berghei parasites, we have evaluated the association of choline kinase (CK), pantothenate kinase 1 (PANK1), diacylglycerol kinase (DAGK), and phosphatidylinositol-4 kinase (PI4Kβ), and calcium-dependent protein kinase 1 (CDPK1) with LM, PQ, and AQ resistance in Plasmodium berghei ANKA. Methods: We used in silico bioinformatics tools to identify ligand-binding motifs, active sites, and sequence conservation across the different parasites. We then used PCR and sequencing analysis to probe for single nucleotide polymorphisms (SNPs) within the predicted functional motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1. Using qPCR analysis, we finally measured the mRNA amount of PANK1, DAGK, and PI4Kβ at trophozoites and schizonts stages. Results: We reveal sequence conservation and unique ligand-binding motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1 across malaria species. DAGK, PANK1, and PI4Kβ possessed nonsynonymous mutations; surprisingly, the mutations only occurred in the AQr parasites. PANK1 acquired Asn394His, while DAGK contained K270R and K292R mutations. PI4Kβ had Asp366Asn, Ser1367Arg, Tyr1394Asn and Asp1423Asn. We show downregulation of PANK1, DAGK, and PI4Kβ in the trophozoites but upregulation at the schizonts stages in the AQr parasites. Conclusions: The selective acquisition of the mutations and the differential gene expression in AQ-resistant parasites may signify proteins under AQ pressure. The role of the mutations in the resistant parasites and the impact on drug responses require further investigations in malaria parasites.

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ), the long-acting components of the artemisinin-based combination therapies (ACTs), are a cornerstone of malaria treatment in Africa. Studies have shown that PQ, AQ, and LM resistance may arise independently of predicted modes of action. Protein kinases have emerged as mediators of drug action and efficacy in malaria parasites; however, the link between top druggable Plasmodium kinases with LM, PQ, and AQ resistance remains unclear. Using LM, PQ, or AQ-resistant Plasmodium berghei parasites, we have evaluated the association of choline kinase (CK), pantothenate kinase 1 (PANK1), diacylglycerol kinase (DAGK), and phosphatidylinositol-4 kinase (PI4Kβ), and calcium-dependent protein kinase 1 (CDPK1) with LM, PQ, and AQ resistance in Plasmodium berghei ANKA. Methods: We used in silico bioinformatics tools to identify ligand-binding motifs, active sites, and sequence conservation across the different parasites. We then used PCR and sequencing analysis to probe for single nucleotide polymorphisms (SNPs) within the predicted functional motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1. Using qPCR analysis, we finally measured the mRNA amount of PANK1, DAGK, and PI4Kβ at trophozoites and schizonts stages. Results: We reveal sequence conservation and unique ligand-binding motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1 across malaria species. DAGK, PANK1, and PI4Kβ possessed nonsynonymous mutations; surprisingly, the mutations only occurred in the AQr parasites. PANK1 acquired Asn394His while DAGK contained K270R and K292R mutations. PI4Kβ had Asp366Asn, Ser1367Arg, Tyr1394Asn and Asp1423Asn. We show downregulation of PANK1, DAGK, and PI4Kβ in the trophozoites but upregulation at the schizonts stages in the AQr parasites. Conclusions: The selective acquisition of the mutations and the differential gene expression in AQ-resistant parasites may signify proteins under AQ pressure. The role of the mutations in the resistant parasites and the impact on drug responses require further investigations in malaria parasites.

Nanotechnology is an emerging field that has opened new horizons in nanomedicine. The use of silver nanoparticles is attracting much interest because of their antibacterial activity. This study involved synthesis of silver nanoparticles using Chrysanthemum cinerariaefolium flowers dichloromethane-methanol crude extract. The synthesized silver nanoparticles (Ag NPs) were characterized using UV-Vis spectroscopy, SEM, EDX, TEM and FTIR. The antibacterial potential of the nanoparticles was ascertained against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Staphylococcus aureus and Shigella sonnei. This was followed by phytochemical analyses of the crude extracts. The Ag NPs were generally spherical as observed in the SEM and TEM micrographs with an average size of 26.98 nm. The UV- absorption spectrum revealed prominent peak at 430 nm while EDX analysis showed the percentage abundance of silver nanoparticle at (81.33%). The FTIR spectroscopy confirmed absorption bands of various functional groups on the surface of Ag NPs. The absorption bands were at 3472.88 cm^-1, 3190.67 cm^-1, 1646.61 cm^-1, 1405.08 cm^-1, 1109.32 cm^-1 and 518.64 cm^-1. Antibacterial potential of the synthesized Ag NPs showed that they were more active on S. aureus with an MIC of 31.25 µg/ml. The phytochemicals observed in the crude extracts that could have been responsible for reducing silver ions into silver nanoparticles were flavonoids, phenols, tannins and glycosides.

Chemotherapy remains central in the control of malaria; however, resistance has consistently thwarted these efforts. Currently, lumefantrine (LM), and piperaquine (PQ) drugs, are essential components in the mainstay artemisinin-based therapies used for the treatment of malaria globally. Using LM and PQ-resistant Plasmodium berghei , we measured the effect of known chemosensitizers: probenecid, verapamil, or cyproheptadine on the activity of LM or PQ. Using PlasmoGEM vectors, we then evaluated the impact of deleting cysteine desulfurase (SufS) or over-expressing Ferredoxin NADP+ reductase (FNR), genes that mediate drug action. Our data showed that, only cyproheptadine at 5mgkg ⁻¹ restored LM activity by above 65% against the LM-resistant parasites (LM ^R ) but failed to reinstate PQ activity against the PQ-resistant parasites (PQ ^R ). Whereas the PQ ^R had lost significant susceptibility to LM, the three chemosensitizers; cyproheptadine, probenecid, and verapamil, restored LM potency against the PQ ^R by above 70%, 60%, and 55% respectively. We thus focused on LM resistance in PQ ^R . Deletion of the SufS or overexpression of the FNR genes in the PQ ^R abolished the impact of the chemosensitizers on the LM activity, and restored the susceptibility of the PQ ^R parasites to LM. Taken together, we demonstrate the association between SufS or FNR genes with the action of LM and chemosensitizers in PQ ^R parasites. There is, however, need to interrogate the impact of the chemosensitizers and the role of SufS or FNR genes on LM action in the human malaria parasite, Plasmodium falciparum .