Using multi-criteria risk ranking methodology to select case studies for a generic risk assessment framework for exotic disease incursion and spread through Europe

We present a novel approach of using the multi-criteria pathogen prioritisation methodology as a basis for selecting the most appropriate case studies for a generic risk assessment framework. The approach uses selective criteria to rank exotic animal health pathogens according to the likelihood of introduction and the impact of an outbreak if it occurred in the European Union (EU). Pathogens were evaluated based on their impact on production at the EU level and international trade. A subsequent analysis included criteria of relevance to quantitative risk assessment case study selection, such as the availability of data for parameterisation, the need for further research and the desire for the case studies to cover different routes of transmission. The framework demonstrated is flexible with the ability to adjust both the criteria and their weightings to the user's requirements. A web based tool has been developed using the RStudio shiny apps software, to facilitate this.

Long term substrate reduction therapy with ezetimibe alone or associated with statins in three adult patients with lysosomal acid lipase deficiency

BACKGROUND

Lysosomal acid lipase deficiency is an autosomal recessive metabolic disease with a wide range of severity from Wolman Disease to Cholesterol Ester Storage Disease. Recently enzyme replacement therapy with sebelipase alpha has been approved by drug agencies for treatment of this lysosomal disease. Ezetimibe is an azetidine derivative which blocks Niemann Pick C1-Like 1 Protein; as its consequence, plasmatic concentration of low density lipoproteins and other apoB-containing lipoproteins, that are the substrate of lysosomal acid lipase, are decreased. Furthermore, ezetimibe acts by blocking inflammasome activation which is the cause of liver fibrosis in steatohepatitis and in lysosomal storage diseases.

RESULTS

Two patients with Cholesterol Ester Storage Disease were treated with ezetimibe for 9 years and a third patients for 10 years. Treatment was supplemented with low dose of atorvastatin in the first two patients during the last 6 years. All patients showed a significant reduction of alanine aminotransferase, cholesterol and triglyceride. Furthermore, no progression of liver fibrosis was demonstrated.

CONCLUSION

In this observational case series, ezetimibe is effective, safe, and sustainable treatment for lysosomal acid lipase deficiency. Further studies are warranted to demonstrate that ezetimibe is an alternative therapy to enzyme replacement therapy.

Autosomal Recessive Hypercholesterolemia: Long-Term Cardiovascular Outcomes

BACKGROUND

Autosomal recessive hypercholesterolemia (ARH) is a rare lipid disorder characterized by premature atherosclerotic cardiovascular disease (ASCVD). There are sparse data for clinical management and cardiovascular outcomes in ARH.

OBJECTIVES

Evaluation of changes in lipid management, achievement of low-density lipoprotein cholesterol (LDL-C) goals and cardiovascular outcomes in ARH.

METHODS

Published ARH cases were identified by electronic search. All corresponding authors and physicians known to treat these patients were asked to provide follow-up information, using a standardized protocol.

RESULTS

We collected data for 52 patients (28 females, 24 males; 31.1 ± 17.1 years of age; baseline LDL-C: 571.9 ± 171.7 mg/dl). During a mean follow-up of 14.1 ± 7.3 years, there was a significant increase in the use of high-intensity statin and ezetimibe in combination with lipoprotein apheresis; in 6 patients, lomitapide was also added. Mean LDL-C achieved at nadir was 164.0 ± 85.1 mg/dl (-69.6% from baseline), with a better response in patients taking lomitapide (-88.3%). Overall, 23.1% of ARH patients reached LDL-C of <100 mg/dl. During follow-up, 26.9% of patients had incident ASCVD, and 11.5% had a new diagnosis of aortic valve stenosis (absolute risk per year of 1.9% and 0.8%, respectively). No incident stroke was observed. Age (≥30 years) and the presence of coronary artery disease at diagnosis were the major predictors of incident ASCVD.

CONCLUSIONS

Despite intensive treatment, LDL-C in ARH patients remains far from targets, and this translates into a poor long-term cardiovascular prognosis. Our data highlight the importance of an early diagnosis and treatment and confirm the fact that an effective treatment protocol for ARH is still lacking.

Molecular and clinical characterization of a series of patients with childhood-onset lysosomal acid lipase deficiency. Retrospective investigations, follow-up and detection of two novel LIPA pathogenic variants

BACKGROUND AND AIMS

Childhood/Adult-onset Lysosomal Acid Lipase Deficiency (LAL-D) is a recessive disorder due to loss of function variants of LAL, the enzyme which hydrolyses cholesteryl esters, derived from internalized apoB containing lipoproteins. The disease is characterized by multi-organ involvement including the liver, spleen, intestine and cardiovascular system. The aim of this study was the clinical and molecular characterization of 14 (13 unrelated) previously unreported patients with childhood-onset LAL-D.

METHODS

Data collected included clinical and laboratory investigations, liver imaging, liver biopsy and LIPA gene analysis. The response to lipid-lowering medications, liver transplantation and enzyme replacement therapy (ERT) was reported for some patients.

RESULTS

LAL-D was suspected at 4.4 ± 3.3 years of age for the presence of hepatomegaly, elevated serum transaminases and hypercholesterolemia, and was confirmed by liver biopsy/imaging and LAL assay. The follow up period ranged from 3 to 40 years (mean 7.8 ± 4.0 years in 13 cases). Patients treated with statins with or without ezetimibe showed 28% reduction of plasma LDL-cholesterol without a tangible effect on liver enzymes; some patients receiving ERT showed normalized lipoprotein profile and transaminase levels. The common c.894G > A variant was observed in homozygosity or compound heterozygosity in 10 patients. We found seven previously reported variants: p.(Trp140*), p.(Arg218*), p.(Gly266*), p.(Thr288Ile), p.(Leu294Ser), p.(His295Tyr) and p.(Gly342Arg) and two novel variants: p.(Asp345Asn), affecting the LAL catalytic triad, and c.229+3A > C, affecting splicing. Homozygosity for p.(Thr288Ile) or c.229+3A > C was associated with a severe phenotype.

CONCLUSIONS

This study provides additional data on the features of childhood-onset LAL-D and describes two novel pathogenic variants of the LIPA gene.

Incidental finding of severe hypertriglyceridemia in children. Role of multiple rare variants in genes affecting plasma triglyceride

BACKGROUND

The incidental finding of severe hypertriglyceridemia (HyperTG) in a child may suggest the diagnosis of familial chylomicronemia syndrome (FCS), a recessive disorder of the intravascular hydrolysis of triglyceride (TG)-rich lipoproteins. FCS may be due to pathogenic variants in lipoprotein lipase (LPL), as well as in other proteins, such as apolipoprotein C-II and apolipoprotein A-V (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface) and LMF1 (a factor required for intracellular formation of active LPL).

OBJECTIVE

Molecular characterization of 5 subjects in whom HyperTG was an incidental finding during infancy/childhood.

METHODS

We performed the parallel sequencing of 20 plasma TG-related genes.

RESULTS

Three children with severe HyperTG were found to be compound heterozygous for rare pathogenic LPL variants (2 nonsense, 3 missense, and 1 splicing variant). Another child was found to be homozygous for a nonsense variant of APOA5, which was also found in homozygous state in his father with longstanding HyperTG. The fifth patient with a less severe HyperTG was found to be heterozygous for a frameshift variant in LIPC resulting in a truncated Hepatic Lipase. In addition, 1 of the patients with LPL deficiency and the patient with APOA-V deficiency were also heterozygous carriers of a pathogenic variant in LIPC and LPL gene, respectively, whereas the patient with LIPC variant was also a carrier of a rare APOB missense variant.

CONCLUSIONS

Targeted parallel sequencing of TG-related genes is recommended to define the molecular defect in children presenting with an incidental finding of HyperTG.

Impact of rare variants in autosomal dominant hypercholesterolemia causing genes

PURPOSE OF REVIEW

The systematic analysis of the major candidate genes in autosomal dominant hypercholesterolemia (ADH) and the use of next-generation sequencing (NGS) technology have made possible the discovery of several rare gene variants whose pathogenic effect in most cases remains poorly defined.

RECENT FINDINGS

One major advance in the field has been the adoption of a set of international guidelines for the assignment of pathogenicity to low-density lipoprotein receptor (LDLR) gene variants based on the use of softwares, complemented with data available from literature and public databases. The clinical impact of several novel rare variants in LDLR, APOB, PCSK9, APOE genes have been reported in large studies describing patients with ADH found to be homozygotes/compound heterozygotes, double heterozygotes, or simple heterozygotes. In-vitro functional studies have been conducted to clarify the effect of some rare ApoB variants on LDL binding to LDLR and the impact of a rare ApoE variant on the uptake of VLDL and LDL by hepatocytes.

SUMMARY

The update of the ADH gene variants database and the classification of variants in categories of pathogenicity is a major advance in the understanding the pathophysiology of ADH and in the management of this disorder. The studies of molecularly characterized patients with ADH have emphasized the impact of a specific variant and the variable clinical expression of different genotypes. The functional studies of some variants have increased our understanding of the molecular bases of some forms of ADH.

A complex phenotype in a child with familial HDL deficiency due to a novel frameshift mutation in APOA1 gene (apoA-IGuastalla)

BACKGROUND

We describe a kindred with high-density lipoprotein (HDL) deficiency due to APOA1 gene mutation in which comorbidities affected the phenotypic expression of the disorder.

METHODS

An overweight boy with hypertriglyceridemia (HTG) and HDL deficiency (HDL cholesterol 0.39 mmol/L, apoA-I 40 mg/dL) was investigated. We sequenced the candidate genes for HTG (LPL, APOC2, APOA5, GPIHBP1, LMF1) and HDL deficiency (LCAT, ABCA1 and APOA1), analyzed HDL subpopulations, measured cholesterol efflux capacity (CEC) of sera and constructed a model of the mutant apoA-I.

RESULTS

No mutations in HTG-related genes, ABCA1 and LCAT were found. APOA1 sequence showed that the proband, his mother and maternal grandfather were heterozygous of a novel frameshift mutation (c.546_547delGC), which generated a truncated protein (p.[L159Afs*20]) containing 177 amino acids with an abnormal C-terminal tail of 19 amino acids. Trace amounts of this protein were detectable in plasma. Mutation carriers had reduced levels of LpA-I, preβ-HDL and large HDL and no detectable HDL-2 in their plasma; their sera had a reduced CEC specifically the ABCA1-mediated CEC. Metabolic syndrome in the proband explains the extremely low HDL cholesterol level (0.31 mmol/L), which was half of that found in the other carriers. The proband's mother and grandfather, both presenting low plasma low-density lipoprotein cholesterol, were carriers of the β-thalassemic trait, a condition known to be associated with a reduced low-density lipoprotein cholesterol and a reduced prevalence of cardiovascular disease. This trait might have delayed the development of atherosclerosis related to HDL deficiency.

CONCLUSIONS

In these heterozygotes for apoA-I truncation, the metabolic syndrome has deleterious effect on HDL system, whereas β-thalassemia trait may delay the onset of cardiovascular disease.

The history of Autosomal Recessive Hypercholesterolemia (ARH). From clinical observations to gene identification

The most frequent form of monogenic hypercholesterolemia, also known as Familial Hypercholesterolemia (FH), is characterized by plasma accumulation of cholesterol transported in Low Density Lipoproteins (LDLs). FH has a co-dominant transmission with a gene-dosage effect. FH heterozygotes have levels of plasma LDL-cholesterol (LDL-C) twice normal and present xanthomas and coronary heart disease (CHD) in adulthood. In rare FH homozygotes plasma LDL-C level is four times normal, while xanthomas and CHD are present from infancy. Most FH patients are carriers of mutations of the LDL receptor (LDLR); a minority of them carry either mutations in the Apolipoprotein B (ApoB), the protein constituent of LDLs which is the ligand for LDLR, or gain of function mutations of PCSK9, the protein responsible for the intracellular degradation of the LDLR. From 1970 to the mid 90s some publications described children with the clinical features of homozygous FH, who were born from normocholesterolemic parents, strongly suggesting a recessive transmission of FH. In these patients the involvement of LDLR and APOB genes was excluded. Interestingly, several patients were identified in the island of Sardinia (Italy), whose population has a peculiar genetic background due to geographical isolation. In this review, starting from the early descriptions of patients with putative recessive hypercholesterolemia, we highlight the milestones that led to the identification of a novel gene involved in LDL metabolism and the characterization of its encoded protein. The latter turned out to be an adaptor protein required for the LDLR-mediated endocytosis of LDLs in hepatocytes. The loss of function of this protein is the cause of Autosomal Recessive Hypercholesterolemia (ARH).

Pharmacological treatment of a Sardinian patient affected by Autosomal Recessive Hypercholesterolemia (ARH)

BACKGROUND AND AIM

Previous studies have shown that patients with autosomal recessive hypercholesterolemia (ARH) resulting from mutations in LDLRAP1 gene have a less severe cardiovascular involvement than familial hypercholesterolemia homozygotes, lower levels of low-density lipoprotein cholesterol (LDL-C), and higher levels of high-density lipoprotein cholesterol (HDL-C). In addition, ARH patients seem to be more responsive to the lipid-lowering drugs. The aim was to test the effect of a combined drug treatment in an ARH patient in the absence of plasmapheresis.

METHODS AND RESULTS

Here we report the lipid-lowering effect of rosuvastatin (60 mg/day) associated with ezetimibe (10 mg/day) in a single ARH patient. The sequencing of LDLRAP1 gene showed that the patient was homozygous for the c.432insA mutation. During a 6-month treatment, we observed an 80% reduction of LDL-C and a significant increase of HDL-C and ApoA-I. Some sequence variations in PCSK9 and NPC1L1 genes found in this patient may have contributed to the success of drug treatment.

CONCLUSIONS

Our findings, although limited to a single case, suggest that in many ARH patients the LDL-C goal may be reached with the more potent statins associated with ezetimibe in the absence of extracorporeal procedures.

Microsomal transfer protein (MTP) inhibition-a novel approach to the treatment of homozygous hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) represents the most severe lipoprotein disorder, generally attributable to mutation(s) of the low-density lipoprotein receptor (LDL-R), i.e. autosomal dominant hypercholesterolemia type 1 (ADH1). Much lower percentages are due to alterations of apolipoprotein B (ADH2), or gain-of-function mutations of proprotein convertase subtilisin/kexin type 9 (PCSK9) (ADH3). In certain geographical areas a significant number of patients may be affected by an autosomal recessive hypercholesterolemia (ARH). Mutations may be also combined (two mutations of the same gene, compound heterozygosity), or two in different genes (double heterozygosity). Among the most innovative therapeutic approaches made available recently, inhibitors of the microsomal transfer protein (MTP) system have shown a high clinical potential. MTP plays a critical role in the assembly/secretion of very-low-density lipoproteins (VLDL), and its absence leads to apo B deficiency. MTP antagonists dramatically lower LDL-cholesterol (LDL-C) in animals, although a reported increase of liver fat delayed their clinical development. Lomitapide, the best-studied MTP inhibitor, reduces LDL-C by 50% or more in HoFH patients, with modest, reversible, liver steatosis. Recent US approval has confirmed an acceptable tolerability, provided patients adhere to a strictly low-fat regimen. There are no clinical data on atherosclerosis reduction/regression, but animal models provide encouraging results.

A 3-day-old neonate with severe hypertriglyceridemia from novel mutations of the GPIHBP1 gene

BACKGROUND

Familial chylomicronemia is a genetic defect of the intravascular lipolysis of triglyceride (TG)-rich lipoproteins. Intravascular lipolysis involves the TG-hydrolase lipoprotein lipase (LPL) as well as other factors such as apolipoprotein CII and apolipoprotein AV (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface), and LMF1 (a factor required for intracellular formation of active LPL).

METHODS

We sequenced the familial chylomicronemia candidate genes in a neonate with chylomicronemia.

RESULTS

A 3-day-old newborn was found to have chylomicronemia (plasma TG 18.8 mmol/L, 1.667 mg/dL). The discontinuation of breastfeeding for 24 hours reduced plasma TG to 2.3 mmol/L (201 mg/dL), whereas its resumption induced a sharp TG increase (7.9 mmol/L, 690 mg/dL). The child was switched to a low-fat diet, which was effective in maintaining TG level below 3.5 mmol/L (294 mg/dL) during the first months of life. The child was found to be a compound heterozygous for 2 novel mutations in GPIHBP1 gene. The first mutation was a 9-bp deletion and 4-bp insertion in exon 2, causing a frameshift that abolished the canonical termination codon TGA. The predicted translation product of the mutant messenger RNA is a peptide that contains 51 amino acids of the N-terminal end of the wild-type protein followed by 252 novel amino acids. The second mutation was a nucleotide change (c.319T>C), causing an amino acid substitution p.(Ser107Pro) predicted in silico to be damaging.

CONCLUSIONS

GPIHBP1 mutations should be considered in neonates with chylomicronemia negative for mutations in LPL gene.

Serological and virological survey of hepatitis E virus in wild boar populations in northwestern Italy: detection of HEV subtypes 3e and 3f

Although rare in developed countries, most acquired human cases of hepatitis E virus (HEV) infection are associated with travel to developing countries where HEV is endemic. Increasingly, however, sporadic, non-travel-related HEV cases have been reported in developed countries. In Italy, only two studies to date have investigated the presence of HEV in wild boars. Here, we report a serological and virological survey of HEV in wild boar populations in northwestern Italy. During the hunting season, 594 serum and 320 liver samples were collected and screened for antibodies to HEV and HEV RNA. Overall, the seroprevalence was 4.9 %, and HEV RNA was detected in 12 liver samples (p = 3.7 %). No serum samples tested positive for HEV RNA. Phylogenetic analysis of the ORF2 region revealed that the isolates clustered within genotype 3, subtypes 3e and 3f, and were closely related to HEV strains previously detected in domestic pigs farmed in the same geographic area. Although the routes of viral transmission are still poorly understood, our data show that HEV genotypes 3e and 3f circulate in wild boars in northwestern Italy. Also, they provide evidence that autochthonous HEV infections in Italy could also be linked to wild boar populations, suggesting an increased risk for domestically acquired HEV infection in humans through wild animals. The HEV sequences determined in this study may be useful for comparing present and future human isolates to identify transmission events between wild boar, humans, and farmed pigs. Similarly to other more commonly known zoonotic agents, HEV should be included in national or regional disease surveillance programs for wild animals.

Mosquito surveillance in northwestern Italy to monitor the occurrence of tropical vector-borne diseases

Mosquito-borne arboviruses (MBV) represent an important health problem, causing diseases and deaths both in human and animals mainly in tropical and subtropical countries. In recent years, they have emerged also in temperate regions where they have caused epidemics. Of mounting concern among public health authorities in Europe are zoonotic mosquito-borne viruses belonging to the Flavivirus genus. The aim of this study was to carry out active surveillance on mosquitoes in two regions of northwestern Italy (Liguria and Piedmont) to gain a better knowledge of the mosquito populations by identifying potential vectors of arboviruses and to investigate arbovirus infection. A network of 61 CO₂ CDC traps was placed in the study area; sampling was conducted from May to October 2011. A total of 46,677 mosquitoes was collected, identified to species level, and classified according to their vector competence. Mosquitoes collected from 16 traps, selected according to risk-based factors, were tested by biomolecular analysis to detect flavivirus infection. This study highlights the importance of entomological surveillance in northwestern Italy because most of the mosquitoes collected were found to have high vector competence. Moreover, the risk-based virological surveillance allowed to detect the presence of mosquito flavivirus RNA, phylogenetically closely related to the MMV Spanish isolate, in three pools and USUV RNA in one pool in new areas where it has not been reported previously. The availability of continuous data on mosquito populations provides invaluable information for use in cases of an epidemic emergency. Maintenance of this integrated system for the next years will provide stronger data that can inform the design of a risk-based surveillance for the early detection of the occurrence of outbreaks of tropical MBDs.

Whole exome sequencing of familial hypercholesterolaemia patients negative for LDLR/APOB/PCSK9 mutations

Background

Familial hypercholesterolaemia (FH) is an autosomal dominant disease of lipid metabolism, which leads to early coronary heart disease. Mutations in LDLR, APOB and PCSK9 can be detected in 80% of definite FH (DFH) patients. This study aimed to identify novel FH-causing genetic variants in patients with no detectable mutation.

Methods and results

Exomes of 125 unrelated DFH patients were sequenced, as part of the UK10K project. First, analysis of known FH genes identified 23 LDLR and two APOB mutations, and patients with explained causes of FH were excluded from further analysis. Second, common and rare variants in genes associated with low-density lipoprotein cholesterol (LDL-C) levels in genome-wide association study (GWAS) meta-analysis were examined. There was no clear rare variant association in LDL-C GWAS hits; however, there were 29 patients with a high LDL-C SNP score suggestive of polygenic hypercholesterolaemia. Finally, a gene-based burden test for an excess of rare (frequency <0.005) or novel variants in cases versus 1926 controls was performed, with variants with an unlikely functional effect (intronic, synonymous) filtered out.

Conclusions

No major novel locus for FH was detected, with no gene having a functional variant in more than three patients; however, an excess of novel variants was found in 18 genes, of which the strongest candidates included CH25H and INSIG2 (p<4.3×10⁻⁴ and p<3.7×10⁻³, respectively). This suggests that the genetic cause of FH in these unexplained cases is likely to be very heterogeneous, which complicates the diagnostic and novel gene discovery process.