Si-Wook Kim

Pathobiological features of a novel, highly pathogenic avian influenza A(H5N8) virus.

The endemicity of highly pathogenic avian influenza (HPAI) A(H5N1) viruses in Asia has led to the generation of reassortant H5 strains with novel gene constellations. A newly emerged HPAI A(H5N8) virus caused poultry outbreaks in the Republic of Korea in 2014. Because newly emerging high-pathogenicity H5 viruses continue to pose public health risks, it is imperative that their pathobiological properties be examined. Here, we characterized A/mallard duck/Korea/W452/2014 (MDk/W452(H5N8)), a representative virus, and evaluated its pathogenic and pandemic potential in various animal models. We found that MDk/W452(H5N8), which originated from the reassortment of wild bird viruses harbored by migratory waterfowl in eastern China, replicated systemically and was lethal in chickens, but appeared to be attenuated, albeit efficiently transmitted, in ducks. Despite predominant attachment to avian-like virus receptors, MDk/W452(H5N8) also exhibited detectable human virus-like receptor binding and replicated in human respiratory tract tissues. In mice, MDk/W452(H5N8) was moderately pathogenic and had limited tissue tropism relative to previous HPAI A(H5N1) viruses. It also induced moderate nasal wash titers in inoculated ferrets; additionally, it was recovered in extrapulmonary tissues and one of three direct-contact ferrets seroconverted without shedding. Moreover, domesticated cats appeared to be more susceptible than dogs to virus infection. With their potential to become established in ducks, continued circulation of A(H5N8) viruses could alter the genetic evolution of pre-existing avian poultry strains. Overall, detailed virological investigation remains a necessity given the capacity of H5 viruses to evolve to cause human illness with few changes in the viral genome.

Virulence and transmissibility of H1N2 influenza virus in ferrets imply the continuing threat of triple-reassortant swine viruses

Efficient worldwide swine surveillance for influenza A viruses is urgently needed; the emergence of a novel reassortant pandemic H1N1 (pH1N1) virus in 2009 demonstrated that swine can be the direct source of pandemic influenza and that the pandemic potential of viruses prevalent in swine populations must be monitored. We used the ferret model to assess the pathogenicity and transmissibility of predominant Korean triple-reassortant swine (TRSw) H1N2 and H3N2 influenza viruses genetically related to North American strains. Although most of the TRSw viruses were moderately pathogenic, one [A/Swine/Korea/1204/2009; Sw/1204 (H1N2)] was virulent in ferrets, causing death within 10 d of inoculation, and was efficiently transmitted to naive contact ferrets via respiratory droplets. Although molecular analysis did not reveal known virulence markers, the Sw/1204 virus acquired mutations in hemagglutinin (HA) (Asp-225-Gly) and neuraminidase (NA) (Ser-315-Asn) proteins during the single ferret passage. The contact-Sw/1204 virus became more virulent in mice, replicated efficiently in vitro, extensively infected human lung tissues ex vivo, and maintained its ability to replicate and transmit in swine. Reverse-genetics studies further indicated that the HA225G and NA315N substitutions contributed substantially in altering virulence and transmissibility. These findings support the continuing threat of some field TRSw viruses to human and animal health, reviving concerns on the capacity of pigs to create future pandemic viruses. Apart from warranting continued and enhanced global surveillance, this study also provides evidence on the emerging roles of HA225G and NA315N as potential virulence markers in mammals.

The diagnostic efficacy and safety of endobronchial ultrasound-guided transbronchial needle aspiration as an initial diagnostic tool

Background/Aims Real-time, convex probe endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is used for the staging of malignant mediastinal lymph nodes. We evaluated the diagnostic efficacy and safety of EBUS-TBNA when used as an initial diagnostic tool. Methods We retrospectively studied 56 patients who underwent EBUS-TBNA as an initial diagnostic tool between August 2010 and December 2011. Procedure purpose were classified into four categories: 1) intrathoracic masses adjacent to the central airway; 2) enlarged lymph nodes for concurrent diagnosis and staging in suspected malignancy; 3) enlarged lymph nodes in suspected malignancy cases with inability to perform percutaneous core needle biopsy (PCNB); and 4) solely mediastinal masses/lymph nodes in lieu of mediastinoscopy. Results The diagnostic accuracy of EBUS-TBNA regardless of procedure purpose was calculated to be 83.9%. Furthermore, the diagnostic accuracy of malignant disease was significantly higher than benign disease (93.9% vs. 70.6%, p < 0.001). The diagnostic accuracy of EBUS-TBNA for each disease is as follows: tuberculosis, 50%; sarcoidosis, 60%; aspergillosis, 100%; lung abscess, 100%; lung cancer, 93%; and lymphoma, 100%. There were minor complications in seven patients during the EBUS-TBNA procedure. The complications included mild hypoxia and bleeding. Conclusions In conclusion, EBUS-TBNA is a useful initial diagnostic tool for both benign and malignant diseases. EBUS-TBAN is also a very safe procedure and less invasive compared to mediastinoscopy or PCNB.

Comparison of the pathogenic potential of highly pathogenic avian influenza (HPAI) H5N6, and H5N8 viruses isolated in South Korea during the 2016–2017 winter season

Highly pathogenic avian influenza (HPAI) A(H5N6) and A(H5N8) virus infections resulted in the culling of more than 37 million poultry in the Republic of Korea during the 2016/17 winter season. Here we characterize two representative viruses, A/Environment/Korea/W541/2016 [Em/W541(H5N6)] and A/Common Teal/Korea/W555/2017 [CT/W555(H5N8)], and evaluate their zoonotic potential in various animal models. Both Em/W541(H5N6) and CT /W555(H5N8) are novel reassortants derived from various gene pools of wild bird viruses present in migratory waterfowl arising from eastern China. Despite strong preferential binding to avian virus–type receptors, the viruses were able to grow in human respiratory tract tissues. Em/W541(H5N6) was found to be highly pathogenic in both chickens and ducks, while CT/W555(H5N8) caused lethal infections in chickens but did not induce remarkable clinical illness in ducks. In mice, both viruses appeared to be moderately pathogenic and displayed limited tissue tropism relative to HPAI H5N1 viruses. Em/W541(H5N6) replicated to moderate levels in the upper respiratory tract of ferrets and was detected in the lungs, brain, spleen, liver, and colon. Unexpectedly, two of three ferrets in direct contact with Em/W541(H5N6)-infected animals shed virus and seroconverted at 14 dpi. CT/W555(H5N8) was less pathogenic than the H5N6 virus in ferrets and no transmission was detected. Given the co-circulation of different, phenotypically distinct, subtypes of HPAI H5Nx viruses for the first time in South Korea, detailed virologic investigations are imperative given the capacity of these viruses to evolve and cause human infections.

Genetic diversity and pathogenic potential of low pathogenic H7 avian influenza viruses isolated from wild migratory birds in Korea.

To detect the circulation of H7 avian influenza viruses, we characterized H7 viruses found in migratory birds and live poultry markets of South Korea from 2005 to 2014. Phylogenic analysis revealed that while all viruses clustered into the Eurasian-lineage of H7 avian viruses, at least 12 distinct genotypes were represented. Most H7 viruses contained at least one gene segment from the highly-pathogenic A/Sck/Hong Kong/YU100/02(H5N1)-like avian virus, and they could be separated into at least two antigenic groups. Although we did not detect genetically identical strains, HI assay demonstrated close cross-reactivity of some isolates with the H7N9 viruses from China. Animal studies revealed that most of the genotypes could replicate in the lungs of mice and chickens without prior adaptation and some, particularly H7N4 and H7N7 subtypes, induced mortality in mice. These results reinforce growing pandemic concerns regarding recent H7 viruses and emphasize the importance of continued surveillance of avian influenza viruses in the wild.

Left Ventricular Apical Lipoma Resected Under the Guidance of a Mediastinoscope

We report a 57-year-old man who was found to have a left ventricular apical mass during a routine check-up. He previously had neither any subjective symptom nor hemodynamic problem. The mass was located deeply in the left ventricular cavity. With exploration using a mediastinoscope, we successfully resected the tumor, which was a yellowish lipoid mass that adhered to the trabeculae near the apex. Histopathologic examination of the tumor was consistent with a lipoma, a very rare benign primary cardiac tumor. The mediastinoscope can be useful for surgical resection of tumors located deeply in the left ventricle.

Primary Pulmonary Amyloidosis with Mediastinal Lymphadenopathy

We report a case of inadvertent hoarseness after surgery for primary pulmonary amyloidosis. A 55-year-old male was transferred to our facility due to a lung mass. Chest computed tomography revealed a solitary pulmonary nodule. Positron emission tomography–computed tomography showed fluorodeoxyglucose uptake in the main mass and in the mediastinal lymph nodes. To confirm the pathology of the mass, wedge resection and thorough lymph node dissection were performed via video-assisted thoracic surgery (VATS). No complications except for hoarseness were observed; hoarseness developed soon after surgery and lasted for 3 months. The main mass was diagnosed as amyloidosis, but this was not found in the lymph nodes. In conclusion, VATS wedge resection for peripheral amyloidosis is a feasible and safe procedure. However, mediastinal lymph node dissection is not recommended unless there is evidence of a clear benefit.

Unintended Pulmonary Artery Ligation during PDA Ligation

A 10-day-old boy was transferred to our hospital due to tachypnea. Patent ductus arteriosus (PDA), 4.8 mm in diameter, with small ASD was diagnosed on echocardiography. Surgical ligation of the ductus was performed after failure of three cycles of ibuprofen. However, the ductus remained open on routine postoperative echocardiography on the second postoperative day, and chest CT revealed inadvertent ligation of the left pulmonary artery (LPA) rather than the PDA. Emergent operation successfully reopened the clipped LPA and ligated the ductus on the same (second postoperative) day.Mechanical ventilator support was weaned on postoperative day 21, and the baby was discharged on postoperative day 47 with a normal left lung shadow.

Mediastinal Paraganglioma: Complete Resection Using Video-Assisted Thoracoscopic Surgery

Mediastinal paragangliomas are very rare neuroendocrine tumors. Complete resection is the standard treatment of a paraganglioma because of the tumors potential malignancy and poor response to chemo- or radiotherapy. However, the highly vascular nature of the tumor and its characteristic anatomic location make complete resection difficult. We report a case of an anterior mediastinal paraganglioma, which was incidentally found on a chest computed tomography scan for chronic cough work-up of a 55-year-old woman. Complete resection was accomplished using video-assisted thoracoscopic surgery, and the patient recovered without any complications.

Rapid growing huge teratoma: complete surgical resection.

We report successful total resection of a huge mediastinal teratoma. An 11-year-old male underwent chest computed tomography that revealed a 14-cm mediastinal mass occupying the right thoracic cavity. The mass was successfully removed without any postoperative postoperative complication.