Pre-existing cross-reactive neutralizing activity against SARS-CoV-2 and seasonal coronaviruses prior to the COVID-19 pandemic (2014-2019) with limited immunity against recent emerging SARS-CoV-2 variants, Vietnam.

OBJECTIVES: SARS-CoV-2 transmission and epidemic potential is related to the population's immunity levels. As such, assessing different regions' preexisting immune responses to SARS-CoV-2 is important to understand the transmission potential of emerging SARS-CoV-2 variants. DESIGN: In 975 serum samples from Vietnam (2014 to 2019), anti-SARS-CoV-2 Immunoglobulin G levels were determined by enzyme-linked immunosorbent assay. Plaque reduction neutralization test (PRNT) was performed using Wuhan strain and variants of concern (VOCs). Cross-reactivity was confirmed by analyzing B-cell receptor (BCR) repertoire sequences and identifying BCR repertoire sequences-derived T-cell epitopes. RESULTS: Overall, 20.9% (n = 76/364) and 9.2% (n = 7) demonstrated SARS-CoV-2 neutralizing activity (PRNT50) against the Wuhan and Alpha strain, respectively. Neutralizing activity against Beta, Gamma, and Delta strains was absent (PRNT50<5) in all samples. Cross-reactive epitopes against SARS-CoV-2 and other coronavirus spike proteins were detected in the N-terminal domain, S2, and receptor-binding domain regions. CONCLUSIONS: Following BCR and major histocompatibility complex analysis, T-cell receptor-recognized epitope motif (TREM) among pathogenic coronaviruses and coronaviruses spike proteins were the top TREM peptide, suggesting that pre-existing immunity against SARS-CoV-2 in Vietnam was due to exposure to common cold coronaviruses. With limited immunity against emerging VOCs, further monitoring, and control of the epidemic, along with COVID-19 vaccine programs against VOCs, are necessary.

Stability and Infectivity of SARS-CoV-2 and Viral RNA in Water, Commercial Beverages, and Bodily Fluids.

The stability and infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in liquid samples are of great concern to virus transmission via common beverages and sewage water. Here, we investigated the stability of SARS-CoV-2 in 32 liquids including common beverages, bodily fluids, and commonly used viral transport media. Our results showed that the infectious virus could be recovered up to 77-days from common beverages including milk and water. Viral RNA could be detected at high levels in all samples up to 28-days, indicating that while viral RNA demonstrates higher stability than infectivity, viral RNA levels do not reflect the infectious capability of SARS-CoV-2. These results indicate that SARS-CoV-2 is highly stable in optimal conditions and a sufficient control measure is needed in reducing the risk of exposure and controlling and preventing future outbreaks.

Discrepancies in Infectivity of Flavivirus and SARS-CoV-2 Clinical Samples: An Improved Assay for Infectious Virus Shedding and Viremia Assessment.

Infectivity and neutralizing antibody titers of flavivirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are frequently measured using the conventional plaque assay. While the assay is useful in the determination of infectivity, conventional plaque assays generally possess lower sensitivity and are time-consuming compared to nucleic acid amplification tests. In this study, a microcrystalline cellulose (MCC), Avicel, was evaluated as an alternative to the conventional virus overlay medium, methylcellulose, for a plaque assay. The plaque assay was performed using dengue and COVID-19 clinical samples and laboratory-established flavivirus and SARS-CoV-2 strains. In virus titration of clinical samples, the plaques were significantly larger, and the virus titers were higher when Avicel MCC-containing overlay medium was used than with conventional methylcellulose overlay medium. In addition, for some clinical samples and laboratory virus strains, infectious particles were detected as plaques in the Avicel MCC-containing medium, but not in the conventional methylcellulose medium. The results suggest that the viremia titer determined using the new overlay medium containing Avicel MCC may better reflect the innate infectious and plaque-forming capabilities of clinical samples and better reflect virus infectivity.

Direct Viral RNA Detection of SARS-CoV-2 and DENV in Inactivated Samples by Real-Time RT-qPCR: Implications for Diagnosis in Resource Limited Settings with Flavivirus Co-Circulation.

The RT-qPCR method remains the gold standard and first-line diagnostic method for the detection of SARS-CoV-2 and flaviviruses, especially in the early stage of viral infection. Rapid and accurate viral detection is a starting point in the containment of the COVID-19 pandemic and flavivirus outbreaks. However, the shortage of diagnostic reagents and supplies, especially in resource-limited countries that experience co-circulation of SARS-CoV-2 and flaviviruses, are limitations that may result in lesser availability of RT-qPCR-based diagnostic tests. In this study, the utility of RNA-free extraction methods was assessed for the direct detection of SARS-CoV-2 and DENV-2 in heat-inactivated or chemical-inactivated samples. The findings demonstrate that direct real-time RT-qPCR is a feasible option in comparison to conventional real-time RT-qPCR based on viral genome extraction-based methods. The utility of heat-inactivation and direct real-time RT-qPCR for SARS-CoV-2, DENV-2 viral RNA detection was demonstrated by using clinical samples of SARS-CoV-2 and DENV-2 and spiked cell culture samples of SARS-CoV-2 and DENV-2. This study provides a simple alternative workflow for flavivirus and SARS-CoV-2 detection that includes heat inactivation and viral RNA extraction-free protocols, with aims to reduce the risk of exposure during processing of SARS-CoV-2 biological specimens and to overcome the supply-chain bottleneck, particularly in resource limited settings with flavivirus co-circulation.

Emergence of a Novel Dengue Virus 3 (DENV-3) Genotype-I Coincident with Increased DENV-3 Cases in Yangon, Myanmar between 2017 and 2019.

Dengue fever, caused by the mosquito-borne dengue virus (DENV), has been endemic in Myanmar since 1970 and it has become a significant public health burden. It is crucial that circulating DENV strains are identified and monitored, and that their transmission efficiency and association with disease severity is understood. In this study, we analyzed DENV-1, DENV-2, DENV-3, and DENV-4 serotypes in 1235 serum samples collected in Myanmar between 2017 and 2019. Whole-genome sequencing of DENV-1-4 demonstrated that most DENV-1-4 strains had been circulating in Myanmar for several years. We also identified the emergence of DENV-3 genotype-I in 2017 samples, which persisted through 2018 and 2019. The emergence of the strain coincided with a period of increased DENV-3 cases and marked changes in the serotype dynamics. Nevertheless, we detected no significant differences between serum viral loads, disease severity, and infection status of individuals infected with different DENV serotypes during the 3-year study. Our results not only identify the spread of a new DENV-3 genotype into Yangon, Myanmar, but also support the importance of DENV evolution in changing the epidemic dynamics in endemic regions.

Pancreaticoduodenectomy after distal gastrectomy: A case series.

INTRODUCTION: Pancreatoduodenectomy (PD) after gastrectomy requires more attention during surgery than ordinary PD due to anatomical variation with different types of gastrointestinal anastomoses, the complication of anatomical dissection, and the extent of adhesions present. Herein, we describe the PD strategies we used in three patients who strategy for three patients who had previously undergone distal gastrectomy for gastric cancer treatment. DISCUSSION: Generally, reconstruction following PD in patients who have undergone a prior Billroth I reconstruction is simple, as there is no previous afferent loop. By comparison, reconstruction after a Billroth II or R-Y reconstruction requires special consideration of the point of circulation and length of the remnant intestine used for pancreaticojejunostomy, choledochojejunostomy or gastrojejunostomy. CONCLUSION: There is no consensus regarding the best method for performing PD and reconstruction in patients with a prior history of gastrectomy. The appropriateness of using the existing afferent loop for reconstruction depends on whether the jejunum is of sufficient length for bile duct and pancreatic anastomosis. Regardless of the approach used, it is necessary to avoid excessive tension during reconstruction. Based on our experience and previous studies published in the English literature, we propose that reconstruction needs to be considered on a case-by-case basis.

Secondary aorto-duodenal fistula successfully treated with a novel surgical method: A case report.

INTRODUCTION: Secondary aorto-duodenal fistula (sADF) is a complication of abdominal aorta artificial blood vessel replacement that often leads to death. However, an optimal operative method has not yet been established. We describe a patient who underwent artificial blood vessel reimplantation and duodenectomy after endovascular aneurysmal repair (EVAR) with positive outcomes. PRESENTATION OF CASE: An 84-year-old man underwent artificial blood vessel replacement in 2015. In September 2016, he visited our emergency department and was diagnosed with sADF based on computed tomography. Urgent EVAR was performed, followed by duodenal segmental resection on the next day without opening the syringeal part to minimize the pollution of the operative field. Artificial blood vessel reimplantation and omental flap transposition were performed. As of 2020, about 3 years after surgery, there has been no relapse of the infection. DISCUSSION: Using our novel operative method, we can minimize exposure of the artificial blood vessel and surrounding tissue to intestinal juice and pus. We believe that this reduces the risk of postoperative artificial blood vessel reinfection. CONCLUSION: Controlling bleeding by EVAR and resection of the duodenum and artificial blood vessels as a group without opening the syringeal part can contribute to positive long-term results as this method minimizes the pollution of the duodenectomy surgical field.

Unresectable Advanced Gastric Cancer with Skin Invasion followed by Total Gastrectomy after Second-Line Chemotherapy.

Conversion surgery has been reported but few cases have undergone surgical R0 resection after second-line chemotherapy. We report a case of an unresectable locally advanced gastric cancer in a patient who finally underwent the operation (R0) after second-line chemotherapy. The 77-year-old male was diagnosed with gastric cancer (cT4 [SI; Skin, Liver] N0M0 c Stage IIIA) with invasion to the skin of the abdominal wall, and chemotherapy was initially performed because of his poor performance status and due to the large defect in the abdominal wall that might occur if an operation was performed. Partial response (PR) was observed after S-1+CDDP (SP) therapy, which was then stopped after which progressive disease (PD) was observed. Ramucirumab+Paclitaxel (RAM/PTX) therapy was chosen as second-line therapy, and PR was obtained again, following which total gastrectomy was performed (D2 dissection of lymph nodes, Roux-en-Y reconstruction, and combined resection of the partial skin and the affected region of the liver). At 30 months postoperatively, no recurrence has occurred and the patient is alive after the operation without chemotherapy.

Inhibitory effect of nifedipine on tumor necrosis factor alpha-induced neovascularization in cultured choroidal explants of streptozotocin-diabetic rat.

We have previously reported that the Nepsilon (carboxymethyl)lysine (CML) adduct, a major structure of an advanced glycation end product, facilitates proliferation of CD34+ endothelial progenitor cells budded from cultured choroidal explants and produces immature vessel-like structures in fibrin gel. The CML adduct is accumulated and facilitates immature neovascularization in cultured choroidal explants of streptozotocin (STZ)-induced diabetic rat. The CML-enhanced neovascularization activity is associated with the actions of tumor necrosis factor (TNF) alpha, vascular endothelial growth factor and platelet-derived growth factor released from the choroidal explant (Kobayashi et al., Biol. Pharm. Bull., 27, 1382-1387 (2004); 27, 1565-1571 (2004)). The present study was investigated an inhibitory effect of a dihydropyridine calcium antagonist nifedipine on TNF alpha-induced choroidal neovascularization in the STZ-diabetic rat. TNF alpha (1-100 ng/ml) increased neovascularization of cultured choroidal explants in the age-matched normal rat but did not increase it in the diabetic rat. Anti-TNF alpha antibody (1 : 1000) decreased the neovascularization in the diabetic rat but not in the normal rat. Nifedipine (1 microM) inhibited TNF alpha-induced neovascularization of the normal choroidal explant in a non-competitive manner. Nifedipine (1 microM) also inhibited the diabetic state-induced neovascularization and its inhibitory action was reversed by TNF alpha (1-10 ng/ml). In conclusion, STZ-diabetic state facilitated choroidal neovascularization through the release of TNF alpha. Nifedipine inhibited the action of TNF alpha probably by blocking voltage-dependent Ca2+ channels in the endothelial progenitor cells of the diabetic choroid.