Some Challenges to Progressive Control of Foot and Mouth Disease in Pakistan – Findings of a Pilot Survey

Pakistan is at an initial stage for progressive control of foot and mouth disease (FMD). Understanding the risk factors for introduction, spread and persistence of the infection is important to design an evidence‐based disease control programme. A rapid appraisal method was adopted, and a convenient sample of twenty commercial dairy farmers was interviewed. The following were considered to contribute in secondary transmission of infection: (i) intermediaries and service providers [animal health workers, animal traders and transporters, raw milk collectors, persons who remove skin of dead animals], (ii) places where animals come in close contact [livestock markets, animal fairs, communal grazing pastures, routes in villages where livestock move, watering points, animal transport vehicles], (iii) use of bulls immediately after recovery from FMD infection, (iv) range land/desert livestock production, (v) small holder sheep and goat production, (vi) purchase of replacement stock and fodder from infected locations. This article reveals contacts within and between villages, some of which may act as routes of transmission of FMD. The study suggests the need for zoosanitary education of the livestock keepers.     

Alternative splicing encodes functional intracellular CD59 isoforms that mediate insulin secretion and are down-regulated in diabetic islets

Human pancreatic islets highly express CD59, which is a glycosylphosphatidylinositol (GPI)-anchored cell-surface protein and is required for insulin secretion. How cell-surface CD59 could interact with intracellular exocytotic machinery has so far not been described. We now demonstrate the existence of CD59 splice variants in human pancreatic islets, which have unique C-terminal domains replacing the GPI-anchoring signal sequence. These isoforms are found in the cytosol of β-cells, interact with SNARE proteins VAMP2 and SNAP25, colocalize with insulin granules, and rescue insulin secretion in CD59-knockout (KO) cells. We therefore named these isoforms IRIS-1 and IRIS-2 (Isoforms Rescuing Insulin Secretion 1 and 2). Antibodies raised against each isoform revealed that expression of both IRIS-1 and IRIS-2 is significantly lower in islets isolated from human type 2 diabetes (T2D) patients, as compared to healthy controls. Further, glucotoxicity induced in primary, healthy human islets led to a significant decrease of IRIS-1 expression, suggesting that hyperglycemia (raised glucose levels) and subsequent decreased IRIS-1 expression may contribute to relative insulin deficiency in T2D patients. Similar isoforms were also identified in the mouse CD59B gene, and targeted CRISPR/Cas9-mediated knockout showed that these intracellular isoforms, but not canonical CD59B, are involved in insulin secretion from mouse β-cells. Mouse IRIS-2 is also down-regulated in diabetic db/db mouse islets. These findings establish the endogenous existence of previously undescribed non–GPI-anchored intracellular isoforms of human CD59 and mouse CD59B, which are required for normal insulin secretion.

Type 2 diabetes (T2D) is a metabolic disorder characterized by persistent hyperglycemia due to insufficient insulin secretion unable to compensate for insulin resistance in peripheral tissues. Complement proteins are components of innate immunity, responsible for host defense and inflammation (1, 2); however, the complement system also contributes to T2D, which develops after years of prediabetes during which increased glucose levels (glucotoxicity), as well as oxidative, metabolic, and inflammatory stress impair insulin secretion (3, 4). Pancreatic islets are richly vascularized and constantly exposed to high concentrations of serum complement proteins; therefore, protection of islets from complement-mediated damage is necessary. Such protection is served by CD59, a ubiquitously expressed, glycosylphosphatidylinositol (GPI)-anchored cell surface protein, that inhibits formation of the complement membrane attack complex (5), a multimeric pore-forming complex of complement proteins that breaches lipid membranes. We previously found that the complement inhibitor CD59 was highly expressed in pancreatic islets (6). Unexpectedly, CD59 knockdown in a rat β-cell line strongly suppressed glucose-stimulated insulin secretion (GSIS). Enzymatic removal of cell-surface CD59 did not affect insulin secretion, leading to the conclusion that an intracellular pool of CD59 was involved in insulin secretion. In β-cells with CRISPR/Cas9-mediated knockout of GPI-anchor synthesis, GSIS still occurred but was CD59 dependent (7), implying involvement of non–GPI-anchored CD59 in insulin secretion. However, this previous data did not identify how endogenous forms of non–GPI-anchored CD59 are produced in β-cells. In the current study we discovered human and mouse CD59 splice variants with alternative C-terminal domains in place of the GPI-anchoring site. Both isoforms are found in primary pancreatic islets and rescue insulin secretion when transfected into CD59 knockout (KO) cells. We named these isoforms IRIS-1 and IRIS-2 (Isoforms Rescuing Insulin Secretion 1 and 2). Our data prove the existence of previously undescribed non–GPI-anchored isoforms of CD59 in human and mouse and demonstrate their involvement in the molecular machinery of β-cell exocytosis. Moreover, a lack of or decreased expression of IRIS isoforms may be involved in the development of T2D.