Poliovirus nonpermissive CD155 knockout cells derived from RD cell line for handling poliovirus potentially infectious materials in virology laboratories.

Destruction of all poliovirus containing materials, safe and secure handling of retained polioviruses for vaccine production, and research will be obligatory to eliminate facility-associated risks. Polioviruses and poliovirus potentially infectious materials (PIM) including fecal or respiratory samples requiring containment have been defined in World Health Organization-Global Action Plan (GAP III) documents. Non-polio laboratories culturing viruses from PIM are most affected as cell cultures of human and monkey origin are also poliovirus permissive. CRISPR gene-editing technology was used to knockout the poliovirus receptor (PVR/CD155) gene in the rhabdomyosarcoma (RD) cell line. PVR knockout RD cell susceptibility was tested using known non-polio enterovirus (NPEV) types. A selected clone (RD-SJ40) was field evaluated for virus isolation from 626 stool samples of acute flaccid paralysis cases. Poliovirus nonpermissive cells derived from the RD cell line did not show CD155-specific cell-surface immunofluorescence. CD155 gene sequencing confirmed nucleotide base pair deletions within exon2 and exon3. The CD155 knockout RD-SJ40 cells did not support the growth of poliovirus from positive stool samples. All NPEV types were isolated in RD and RD-SJ40 cells. CRISPR correctly edited the CD155 gene of RD cells to render them poliovirus nonpermissive while susceptibility to NPEV remained unchanged. RD-SJ40 cells are safe for NPEV isolation from poliovirus PIM without derogating GAP III containment requirements.

Development of a RT-LAMP assay for detection of SARS-CoV-2.

Background & objectives: The pandemic of SARS-COV-2 began in Wuhan, China in December 2019 and has caused more than 101 million cases worldwide. Diagnostic technologies possessing sensitivity and specificity equivalent to real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) assays are needed to ramp up testing capacity in most countries. Newer platforms need to be technically less demanding, require minimum equipment and reduce turn-around time for reporting results. The objective of this study was to exploit loop-mediated isothermal amplification (LAMP) for the detection of SARS-CoV-2 and evaluate its performance by comparison with rRT-PCR. Methods: Reverse-transcription LAMP (RT-LAMP) assay primers were designed to detect envelop (E) and nucleocapsid (N) genes of SARS-CoV-2. Positive control RNA was prepared by in vitro transcription of E and N genes clones. RT-LAMP amplification reactions were incubated at 65°C for 30 min. Results were recorded visually. RT-LAMP results were evaluated by comparing the results obtained with a commercial rRT-PCR kit. Results: The RT-LAMP assay for E and N genes was carried out in separate tubes. RT-LAMP detected about 40 copies of SARS-CoV-2 RNA per reaction. A total of 253 throat swabs were tested using the RT-LAMP assay. The overall diagnostic sensitivity and specificity of the LAMP assay were 98.46 and 100 per cent, respectively, as compared to the rRT-PCR. Interpretation & conclusions: SARS-CoV-2 RT-LAMP assay was designed, standardized and evaluated. The assay showed diagnostic sensitivity and specificity equivalent to rRT-PCR assays. The assay will be useful to increase testing capacity for the detection of SARS-CoV-2 in the country.

A multiplex SNaPshot assay for the detection of single nucleotide polymorphism associated with clinical severity of enterovirus infections.

Non-polio enterovirus infections are known to cause a variety of diseases and neurological complications. It is also known that the severity of these diseases largely differs among individuals with different genotypes and alleles. The Single Nucleotide Polymorphisms (SNPs) within specific genes have a considerable effect on the immune response to enteroviruses and on the outcome of disease, leading to variations in complications and infection susceptibility. Knowing the distribution of such SNPs can be valuable for individual case management and studying epidemiological parameters of enterovirus infections. In this feasibility study, a multiplex version of the primer extension-based technique called the SNaPshot Assay has been developed to examine SNPs in various relevant genes for predicting the clinical severity of enterovirus infections. It is already established that this technique is precise, consistent, scalable, and likely to exhibit high throughput. The multiplex SNaPshot can investigate multiple genetic susceptibility markers simultaneously, and the assay can be used to identify vulnerable populations, understand the epidemiology of infections, and manage the outbreaks of enteroviruses. Based on the literature, 15 SNPs were identified which are suspected for higher susceptibility to the worst outcomes after enterovirus infection and the assay was developed. Blood samples of 100 healthy volunteers were collected and tested for assay feasibility as well as to know the proportions of 15 selected SNPs. After the analysis, seven SNPs have been identified and suggested to be considered for future assays. Based on the pilot test results, it appears that positivity for any three out of the identified seven SNPs might indicate a higher risk, and future studies correlated with clinical studies among patients with and without severe diseases utilizing this assay will provide robust parameters to determine at-risk individuals more accurately.

CD155: A Key Receptor Playing Diversified Roles.

Cluster of differentiation (CD155), formerly identified as poliovirus receptor (PVR) and later as immunoglobulin molecule, is involved in cell adhesion, proliferation, invasion and migration. It is a surface protein expressed mostly on normal and transformed malignant cells. The expression of the receptor varies based on the origin of tissue. The expression of the protein is determined by factors involved in the sonic hedgehog pathway, Ras-MEK-ERK pathway and during stressful conditions like DNA damage response. The protein uses an alternate splicing mechanism, producing four isoforms, two being soluble (CD155ß and CD155γ) and two being transmembrane protein (CD155α and CD155δ). Apart from being a viral receptor, researchers have identified CD155 to play important roles in cancer research and the cell signaling field. The receptor is recognized as a biomarker for identifying cancerous tissue. The receptor interacts with molecules involved in the cells' defense mechanism. The immunesurveillance role of CD155 is being deciphered to understand the mechanistic approach it utilizes as an onco-immunologic molecule. CD155 is a non-MHC-I ligand which helps in identifying non-self to NK cells via an inhibitory TIGIT ligand. The TIGIT-CD155 pathway is a novel MHC-I-independent education mechanism for cell tolerance and activation of NK cells. The receptor also has a role in metastasis of cancer and transendothelial mechanism. In this review, the authors discuss the virus-host interaction that occurs via a single transmembrane receptor, the poliovirus infection pathway, which is being exploited as a therapeutic pathway. The oncolytic virotherapy is now a promising modality for curing cancer.