First report of Helicotylenchus dihystera parasitizing Lady Tankerville orchids (Phaius tankervilleae) in Vietnam.

Lady Tankerville, a rare orchid species (Phaius tankervilleae (Banks ex L'Hér.) Blume) in Vietnam, not only enhances the aesthetic value of the surroundings with its enchanting blooms but also holds high economic value (Aver'janov & Averyanova, 2003). Investigating the necrosis symptom on the root system and declined Lady Tankerville in the market in Hai Duong province in Vietnam from 11/2020 to 12/2021, we discovered a substantial infestation (24/24 plants were infected) of a spiral nematode, Helicotylenchus sp. The nematode population was extracted from the rhizosphere soil, roots, and stems of a single orchid using the modified Baermann tray technique (Whitehead & Hemming, 1965), for thorough characterization. The average nematode density was measured at 525±85 (350-670) nematodes/250 cm3 of soil, 202±56 (198-264) nematodes/15 g of roots, and 80±15 (72-95) nematodes/15 g of stem. Two hundred nematodes from the same population were inoculated into another healthy orchid for preservation and further infection tests. This species was morphologically identified as Helicotylenchus dihystera according to the key of Fotedar and Kaul (1985) and the description of Sher (1966). Morphometric measurements of the females (n = 12) are as follows: body length = 632-725 (681 ± 32) µm; a = 24-34 (28 ± 3); b = 5.1-7.2 (6.0 ± 0.6); b' = 4.3-6.4 (5.3 ± 0.6); c = 33-46 (39 ± 5); c' = 1.1-1.4 (1.2 ± 0.1); V = 62-78 (65 ± 4)%; O = 30 -49 (39 ± 6); stylet length = 21-26 (24 ± 2) µm; DGO = 9.2-12.4 (10.8 ± 1.1) µm. To validate morphological observations, molecular analyses of the ITS (Vrain et al., 1992) and the D2-D3 of 28S rRNA (Subbotin et al., 2006) were conducted. The ITS and D2-D3 sequences from this study (accession number: PP060444 and PP033748) exhibited the highest similarity of 99.8% and 100% to the sequence of H. dihystera in GenBank (KM506885 and MW023215), respectively. The infection test took place in a greenhouse at 28 ± 2℃. Three-month-old Phaius tankervilleae (n=8) were individually grown in 15 x 15 cm deep pots filled with sterilized sand and inoculated with 500 gravid females of H. dihystera (Rashid & Azad, 2013). Two noninoculated plants served as controls. After 60 days of inoculation, symptoms such as sunspots and root necrosis, observed in the market, appeared in the tested plants (Fig. S1). The presence and diagnosis of H. dihystera infestation in soil, roots, and stems across growth stages of orchids indicates the nematode to be an obligate parasite. The nematodes penetrate the roots, causing characteristic necrotic lesions initially yellow, then turn reddish-brown to black, along with brown root flecks in discolored tissues. Heavy infestations post-flowering led to extensive necrosis, distortion, and decay of the roots. The average reproduction factor (final population/initial population) of H. dihystera in this study was 22.2. Control plants remained symptom-free. Notably, 100% of tested plants were infected, highlighting the severe impact of H. dihystera. The nematodes were successfully reisolated and identified as H. dihystera through molecular analyses (accession number: PP060615 (ITS) and PP033748 (D2-D3)), reaffirming its identity. In addition to 32 host plants in Vietnam (Nguyen et al., 2023), our study reveals a strain of H. dihystera parasitizing Lady Tankerville orchids with a relatively high reproduction factor and infection rate. This marks the first reported instance of H. dihystera parasitizing Lady Tankerville orchids in Vietnam, emphasizing the need for proactive measures to protect this plant.

Central Retinal Vein Occlusion after COVID-19 Infection.

INTRODUCTION: Central retinal vein occlusions are not well-known complications of SARS-CoV-2 infection. We describe a case of central retinal vein occlusion secondary to COVID-19, and a review of the literature was performed. HISTORY AND SIGNS: A 47-year-old woman with no underlying ocular or medical condition presented to the hospital complaining about sudden onset of multiple scotomas in her left eye. A COVID-19 infection was confirmed 2 days previously by a PCR test that was performed 2 days after the onset of symptoms. Medical history revealed no risk factors and no oral contraception. Her best-corrected visual acuity was 1.0 in the right eye and 0.04 in the left eye. Clinical exam showed a left relative afferent pupillary defect and a nasally localized papilledema on fundoscopy of the left eye. Multiple dot and blot hemorrhages were also present. Optical coherence tomography revealed cystoid macular edema and paracentral acute middle maculopathy. The results of the fluoresceine angiography were consistent with central retinal vein occlusion. Laboratory workup later revealed an elevated fibrinogen level, corresponding to the COVID-19-induced hypercoagulable state. No other prothrombotic conditions were found. The patient immediately received an intravitreal injection of Lucentis (ranibizumab) after diagnosis. Complete resolution of the retinal hemorrhages and papilledema was observed 1.5 months after treatment and the final visual acuity was 1.25 in the left eye. CONCLUSION: Coagulation abnormalities are frequently observed in infectious diseases such as COVID-19 infection and the resulting prothrombotic state can sometimes lead to retinal vascular complications, including central retinal vein occlusion, irrespective of the presence of other classical risk factors. The consideration of this information could help clinicians establish a prompt diagnosis and therefore appropriate treatment, which could hopefully lead to complete healing of retinal lesions.

Spectrum of mutations in the RB1 gene in Vietnamese patients with retinoblastoma.

Purpose: Retinoblastoma (RB) is a rare childhood malignant disorder caused by the biallelic inactivation of the RB1 gene. Early diagnosis and identification of carriers of heritable mutations in RB1 can improve disease outcome and management. In this study, we present the spectrum of mutations in the RB1 gene in Vietnamese patients with RB. Methods: Tumor RNA from 50 probands with RB, including 12 bilateral and 38 unilateral cases, was extracted. cDNA, after reverse transcription, was sequenced to identify the RNA mutation of the RB1 gene. At the genomic DNA level, mutational analysis of all RB1 exons, exon-intron boundaries, and the promoter region was conducted using PCR and direct sequencing. Multiplex ligation-dependent probe amplification (MLPA) analysis was performed for patients for whom the first two results were negative. For patients for whom either the sequencing or MLPA results were positive for a tumor mutation, patients' and their parents' blood DNA was analyzed to determine the germline mutation. Results: Forty-one different kinds of RB1 tumor mutations were identified in 41 probands (82.0%), including 11 of 12 bilateral cases (91.7%) and 30 of 38 unilateral cases (78.9%). The majority of the detected mutations were nonsense (15 different kinds), followed by frameshift (11 kinds), and splice site mutations (nine kinds). Each splice site mutation was confirmed to create a deletion of the corresponding exon with RNA sequencing. The single promoter mutation c.-197G>A was reported previously; however, both missense mutations identified in exon 6 (c.601G>C: p.A201P) and exon 22 (c.2264T>C: p.F755S) were novel. Gross deletions were detected with MLPA in three probands. The detection rate of germline mutations in bilateral and unilateral cases with mutations were 81.8% and 30.0%, respectively. Only one father out of the 20 parents tested was positive for a germline mutation. Conclusions: Mutations in the RB1 gene in Vietnamese patients were heterogeneous and highly prevalent with pathogenic truncated mutations. With advancement in therapeutics, early detection of RB is important for eye salvation.

Expression of HOXD9 in fibroblast-like synoviocytes from rheumatoid arthritis patients.

The proteins of homeobox (HOX) genes are transcription regulators involved in cell type-specific differentiation and patterning of the body plan in vertebrates. Particularly, the HOXD family is involved in limb formation in mice and chicks. There is also some evidence that the HOXD9 gene, a member of the HOXD family, is involved in the pathology of rheumatoid arthritis (RA). The purpose of the present study was to determine if the HOXD9 protein was expressed in RA synovium and then to characterize the HOXD9-expressing cell. Western blotting and immunohistochemical analysis showed that the HOXD9 protein was expressed in the synovium from patients with RA, but not in those from patients with osteoarthritis or healthy individuals. The HOXD9-positive cells were localized in both the lining and sublining areas of the synovium. Furthermore, fluorescent double-staining showed that the HOXD9 protein was expressed in fibroblast-like synoviocytes (FLS). These findings not only indicate that the HOXD9 gene is exclusively expressed in the RA synovium but also suggest that the HOXD9 gene contributes to the pathology of rheumatoid arthritis through the FLS.