Abstracts of Presentations to the Working Session on Improving Predictive Modeling of Mycotoxin Risk for Africa Held at the 3rd ASM2022 on 7 September 2022, in Stellenbosch, South Africa

In 2008, the African Postharvest Losses Information Systems project (APHLIS, accessed on 6 September 2022) developed an algorithm for estimating the scale of cereal postharvest losses (PHLs). The relevant scientific literature and contextual information was used to build profiles of the PHLs occurring along the value chains of nine cereal crops by country and province for 37 sub-Saharan African countries. The APHLIS provides estimates of PHL figures where direct measurements are not available. A pilot project was subsequently initiated to explore the possibility of supplementing these loss estimates with information on the aflatoxin risk. Using satellite data on drought and rainfall, a time series of agro-climatic aflatoxin risk warning maps for maize was developed covering the countries and provinces of sub-Saharan Africa. The agro-climatic risk warning maps for specific countries were shared with mycotoxin experts from those countries for review and comparison with their aflatoxin incidence datasets. The present Work Session was a unique opportunity for African food safety mycotoxins experts, as well as other international experts, to meet and deepen the discussion about prospects for using their experience and their data to validate and improve agro-climatic risk modeling approaches.

First application of a microsphere-based immunoassay to the detection of genetically modified organisms (GMOs): quantification of Cry1Ab protein in genetically modified maize

An innovative covalent microsphere immunoassay, based on the usage of fluorescent beads coupled to a specific antibody, was developed for the quantification of the endotoxin Cry1Ab present in MON810 and Bt11 genetically modified (GM) maize lines. In particular, a specific protocol was developed to assess the presence of Cry1Ab in a very broad range of GM maize concentrations, from 0.1 to 100% [weight of genetically modified organism (GMO)/weight]. Test linearity was achieved in the range of values from 0.1 to 3%, whereas fluorescence signal increased following a nonlinear model, reaching a plateau at 25%. The limits of detection and quantification were equal to 0.018 and 0.054%, respectively. The present study describes the first application of quantitative high-throughput immunoassays in GMO analysis.

Development of an innovative immunoassay for CP4EPSPS and Cry1AB genetically modified protein detection and quantification

An innovative immunoassay, called enzyme-linked immunoabsorbant assay (ELISA) Reverse, based on a new conformation of the solid phase, was developed. The solid support was expressly designed to be immersed directly in liquid samples to detect the presence of protein targets. Its application is proposed in those cases where a large number of samples have to be screened simultaneously or when the simultaneous detection of different proteins is required. As a first application, a quantitative immunoassay for Cry1AB protein in genetically modified maize was optimized. The method was tested using genetically modified organism concentrations from 0.1 to 2.0%. The limit of detection and limit of quantitation of the method were determined as 0.0056 and 0.0168 (expressed as the percentage of genetically modified organisms content), respectively. A qualitative multiplex assay to assess the presence of two genetically modified proteins simultaneously was also established for the case of the Cry1AB and the CP4EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) present in genetically modified maize and soy, respectively.

Differential expression of MMP-2/MMP-9 and potential benefit of an MMP inhibitor in experimental acute kidney allograft rejection

Acute cellular allograft rejection is characterized by leukocyte invasion and tissue destruction, associated with qualitative and quantitative alterations in the extracellular matrix (ECM) compartment. Metabolism of ECM proteins is mainly regulated by matrix metalloproteinases (MMP), that are zinc depended endoproteinases. MMP, especially basement membrane degrading MMP-2 and MMP-9, also facilitate tissue invasion of leukocytes. In addition, MMP-2 exerts a direct pro-inflammatory effect upon glomerular mesangial cells. Therefore, the investigation of the role of MMP in transplant rejection may lead to novel approaches in the therapy of rejection processes. To our knowledge, this is the first study of acute allograft rejection, formally addressing expression and activity of MMP, including the effect of a MMP inhibiting agent. For our studies, we used the orthotopic kidney allograft model in the stringent Dark Agouti-to-Lewis rat strain combination. Animals were divided into four groups: group A, healthy untreated Lewis rats (n=3); group B, sham operated Lewis rats (n=3); group C, transplanted Lewis rats treated with vehicle solution only (n=12); group D, transplanted Lewis rats treated with MMP inhibitor BB-94 (n=12). Respective animals were treated once daily intraperitonealy with BB-94 (30 mg/kg) or vehicle solution only. Treatment lasted from the third preoperative day until the end of the experiment, the time of severe rejection at day +7. Acute kidney allograft rejection led to alterations in the expression and activity of MMP. Overall MMP activity slightly increased despite severe destruction of kidney histology. The MMP inhibitor BB-94 successfully inhibited MMP activity to a high extent. MMP expression did not show uniform findings, since acute rejection led to differential expression of MMP-2 and MMP-9. During the rejection process, MMP-9 showed a small but significant increase, whereas MMP-2 production decreased substantially. Interestingly, BB-94 was able to keep proteinuria at a low level in transplanted animals. In conclusion, MMP-especially MMP-9-appear to represent new mediators involved in acute kidney transplant rejection.

Nickel, cobalt and chromium-induced cytotoxicity and intracellular accumulation in human hacat keratinocytes

Nickel, cobalt and chromium can induce allergic contact dermatitis (ACD) and may provoke irritant reactions in the skin. This study aimed at investigating cytotoxicity and cell viability along with intracellular metal accumulation in HaCaT human keratinocytes exposed to soluble forms of nickel, cobalt or chromium. The EC50 (24 h) values as detected by MTT test were 30 microM for sodium chromate (Na2CrO4), 475 microM for cobalt chloride (CoCl2) and 600 microM for nickel chloride (NiCl2). Chromium chloride (CrCl3) was not toxic up to 1 mM. No clear effects were observed after 4 h, but 24-h treatments with 1 mM CoCl2 or 10 microM Na2CrO(4) were found to almost completely abolish the ability of the cells to form colonies, whilst 1 mM NiCl2 reduced cellular survival to only 70% of control cultures. Intracellular accumulation of metals was evaluated by the use of radioisotopes at the EC50 value and at 1/10-1/5 of this concentration. Accumulation of Na2(51)CrO4 was linear with increasing dose. This was not the case for 63NiCl2 and 58CoCl2. All the metals were accumulated preferentially in the cytosols; 96% or more for 63NiCl2, approximately 90% for 58CoCl2 and 60-70% for Na2(51)CrO4. Finally, it was observed that HaCaT human keratinocytes can concentrate the metals present in the media up to 3.9 and 12.5 times for NiCl2 and CoCl2, respectively, and up to 167 for Na2CrO4. These striking metal intracellular accumulation patterns, which have not been earlier described in keratinocytes, highlight the relevance of searching for specific biomarkers of early cellular toxic effects, such as cytosolic proteins that bind the metals.

Nickel-induced proteins in human HaCaT keratinocytes: annexin II and phosphoglycerate kinase

It has been established in previous in vitro experiments with human HaCaT keratinocytes that nickel becomes cytotoxic at concentrations higher than 100 microM and that it is accumulated mainly in the cytosolic fraction (Ermolli et al., 2000). The aim of this work was to search possible biomarkers of metal insult, i.e. nickel-binding proteins or proteins differentially expressed in the cytosolic fraction of nickel-exposed cells (up to 1 mM nickel) as compared to controls. Cytosolic proteins were studied by isoelectric focusing (IEF) and two-dimensional gel electrophoresis (2-DE). Separation by IEF revealed nickel-induced changes in the abundance of cytosolic proteins as visualised with nickel-nitrilo-triacetic-alkaline phosphatase (Ni-NTA-AP) in blots. The cytosolic fraction of cells incubated with nickel, at concentrations over 100 microM, showed nickel binding components which were absent or present in significantly lower amounts in control cells. These proteins had isoelectric points (pIs) 6.9, 7.7 and 8.5. After 2-DE silver- and protein staining significantly increased abundance of four proteins was observed. Their pI values corresponded to those of the nickel binding ones seen after IEF. A protein with pI 6.9 had a molecular weight estimated to 38 kDa, two proteins with pI around 7.7 showed molecular weights of 57 and 22 kDa, respectively and another protein with pI of 8.5 had a molecular weight of 33 kDa. The increased abundance of these components, both in IEF experiments and in 2-DE, correlated with the nickel concentration in the culture media. N-terminal amino acid sequencing and database search allowed identification of one a protein as phosphoglycerate kinase and another one as annexin II. The involvement of these proteins in cellular functions and their possible implications in the mechanism of nickel toxicity in keratinocytes are discussed. Some of these proteins may be biomarker candidates for effects of nickel exposure in human keratinocytes.

[Indications for cerebral revascularization surgery (author's transl)]

Cerebrovascular diseases are among the most widespread. In the USA alone there is at any time a population of 1.6 million people with current stroke syndrome or the sequelae thereof. The most effective weapon to combat this disease is prevention, and here reference is made in particular to surgical prevention, especially through endoarterectomy of the extracranial internal carotid, and to vertebrobasilar circulatory failure.

[Portal cavernoma. Observation of a case and clinico-nosographic considerations (author's transl)]

The clinical case of a sixty-two year old woman suffering for about six years from rare episodes of cramplike pains in the right hypochondriac region, radiated to the homolateral scapula, is described. After diagnosis of biliary calculosis, the patient was admitted to hospital and her gallbladder removed. During the operation a number of venous ectasias of the portal system were evidenced at the hepatic hilus, and their biopsy led to a diagnosis of portal cavernoma. The possible part played by the cavernoma in producing the patient's clinical picture is discussed, with reference also to other cases of cavernoma of varying location. This is followed by a review of the literature, in which stress is placed on the different aetiopathogenetic interpretations of angiomas and in particular of portal cavernomas. The possible evolution of angiomas and present treatment trends are also mentioned.