Evaluation of a new automated viral RNA extraction platform for hepatitis A virus and human norovirus in testing of berries, lettuce, and oysters

Fruits, vegetables, and shellfish are often associated with outbreaks of illness caused particularly by human norovirus (HuNoV) and hepatitis A virus (HAV), the leading causative agents of foodborne illness worldwide. The aim of this study was to evaluate a new automated nucleic acid extraction platform (EGENE-UP EASYPREP) for enteric viruses in several at-risk food matrices and to test its limit of detection in comparison to a semi-automated method (EGENE-UP) using Boom methodology for nucleic acid extraction as suggested in the reference method ISO 15216-2:2019. Fresh and frozen raspberries, frozen blackberries, romaine lettuce and oyster digestive glands were artificially contaminated with HAV, HuNoV GII.4 or HuNoV GI.7 at 102, 103 or 104 genome copies/sample. Virus was then recovered from the food matrix using the ISO method. Viral RNA extracted from frozen berry samples by the automated system was purified on a column for additional removal of RT-qPCR inhibitors. For fresh raspberry, oysters, and romaine lettuce, the two extraction platforms were deemed equivalent. For frozen raspberry, the automated platform appeared to be more efficient for viral recovery, particularly for HAV and HuNoV GI at lower concentrations. With frozen blackberries, the two platforms may be considered equivalent for all targeted viruses. However, the automated method led to less sample-associated inhibition of the PCR, 56.5 % of samples versus 95.0 % for the semi-automated. We thus found that the automated extraction can be performed easily by users while obtaining equivalent or even superior results to the ISO 15216-2:2019 method, and therefore appears to be suitable for routine sanitary monitoring in food processing and for tracing outbreaks of illness.

Concentration of foodborne viruses eluted from fresh and frozen produce: Applicability of ultrafiltration

Foodborne illnesses involving raw and minimally processed foods are often caused by human noroviruses (HuNoV) and hepatitis A virus (HAV). Since food is contaminated usually with small numbers of virions, these must be eluted from the food surface and then concentrated for detection. The objective of this study was to optimize an ultrafiltration (UF) concentration method for HAV and HuNoVs present on various fresh and frozen produce. The detection range of the optimized method and its applicability to different food matrices was compared to the reference method ISO 15216-1:2017. Strawberry, raspberry, blackberry, lettuce, and green onion (25 g) were contaminated with HAV, HuNoV GI.7 and HuNoV GII.4 and then recovered therefrom by elution. A commercial benchtop UF device was used for the concentration step. Viral RNA was extracted and detected by RT-qPCR. From fresh strawberries, recovery of HAV loaded at 104 genome copies per sample was 30 ± 13 %, elution time had no significant impact, and UF membrane with an 80-100 kDa cut-off in combination with Tris-glycine elution buffer at pH 9.5 was found optimal. At lower copy numbers on fresh strawberry, at least 1 log lower numbers of HuNoV were detectable by the UF method (103 vs 104 GII.4 copies/sample and 101 vs 103 GI.7 copies/sample), while HAV was detected at 101 genome copies/sample by both methods. Except on raspberry, the UF method was usually equivalent to the ISO method regardless of the virus tested. The UF method makes rapid viral concentration possible, while supporting the filtration of large volume of sample. With fewer steps and shorter analysis time than the ISO method, this method could be suitable for routine analysis of viruses throughout the food production and surveillance chain.

Photodynamic therapy with verteporfin following transpupillary thermotherapy for CNV evolving from an initially occult to a predominantly classic form, in patients with AMD

The purpose of this paper is to evaluate photodynamic therapy (PDT) in the management of choroidal neovascularization (CNV) due to age-related macular degeneration (AMD) that converted from occult CNV to classic CNV after treatment with transpupillary thermotherapy (TTT). One hundred and fifty-four eyes of 130 patients with symptomatic occult CNV were treated between June 2000 and August 2001. We have analyzed data from patients treated with PDT because of a conversion from occult to classic CNV after TTT. The results were that twenty-four of 154 eyes developed a predominantly classic CNV; 20 eyes of 19 consecutive patients were treated with PDT with verteporfin. The mean follow-up period was 10 months. The mean delay for retreatment with TTT was 3 months; 3 eyes initially presented a pure occult CNV, 15 a minimally classic CNV, 1 an occult CNV with pigment epithelial detachment, and 1 a large macular subretinal hemorrhage with a subfoveal focal hot spot. The average classic component within a lesion before TTT was 20%. Recurrence of classic CNV was noted in the first 3 months for 14 eyes. Visual acuity improved in 5 eyes by >/=2 lines, and in 2 eyes by 1 line; 4 of 20 eyes had stabilized visual acuity; 7 eyes had a visual acuity decline of >/=2 lines; 2 eyes lost 1 line. All patients had reduction of metamorphopsia and reduction of exudation; 14 eyes had a little subretinal fibrosis and some partially atrophic areas; 6 eyes had slightly increased leakage in the late phase of the angiogram. In conclusion, association of TTT and PDT appears to be safe and may help practitioners to manage some difficult cases. This study seems to confirm the great efficacy of PDT in CNV with recent activity.

Factors affecting the stability of tPA and PAI-1 during storage and handling of human plasma for in vitro studies: implications in the determination of tPA and PAI-1 activities

Factors that influence the physico-chemical conditions of plasma (e.g. pH, dilution, freezing, storage) and thereby the stability of tPA and PAI-1 activities, have been studied and optimized using a solid-phase fibrin-tPA activity assay. Optimal recovery of tPA activity was at a pH of 6.8 +/- 0.2, while at the pHs usually found in thawed plasma, i.e. pH 7.6-8.2, the activity was lower and showed great variability. Free tPA activity was tested in undiluted plasma, while plasma diluted 1:20 was used to recover maximal tPA activity. The corrected value for the diluted plasma and the value for the euglobulin suspensions were similar. In both cases the pH optimum was 7.4. PAI activity levels were tested in undiluted plasma and showed no variations after venous occlusion. Our results indicate that the in vitro determination of tPA activity is directly related to the pH of thawed plasma and not to the freezing procedure or the temperature of storage. Therefore, thawed plasma should be tested at a pH giving the maximal recovery of tPA activity in a particular assay method.