Development of immunohistochemistry and in situ hybridisation for the detection of SARS-CoV and SARS-CoV-2 in formalin-fixed paraffin-embedded specimens.

The rapid emergence of SARS-CoV-2, the causative agent of COVID-19, and its dissemination globally has caused an unprecedented strain on public health. Animal models are urgently being developed for SARS-CoV-2 to aid rational design of vaccines and therapeutics. Immunohistochemistry and in situ hybridisation techniques that facilitate reliable and reproducible detection of SARS-CoV and SARS-CoV-2 viral products in formalin-fixed paraffin-embedded (FFPE) specimens would be of great utility. A selection of commercial antibodies generated against SARS-CoV spike protein and nucleoprotein, double stranded RNA, and RNA probe for spike genes were evaluated for the ability to detect FFPE infected cells. We also tested both heat- and enzymatic-mediated virus antigen retrieval methods to determine the optimal virus antigen recovery as well as identifying alternative retrieval methods to enable flexibility of IHC methods. In addition to using native virus infected cells as positive control material, the evaluation of non-infected cells expressing coronavirus (SARS, MERS) spike as a biosecure alternative to assays involving live virus was undertaken. Optimized protocols were successfully applied to experimental animal-derived tissues. The diverse techniques for virus detection and control material generation demonstrated in this study can be applied to investigations of coronavirus pathogenesis and therapeutic research in animal models.

Análisis de sondas y técnicas de amplificación de genes para el diagnóstico y control del tratamiento en la lepra infantil / No disponible

Se detectaron secuencias de ácidos nucleídos de Mycobacterium leprae utilizando sonda de genes que hibridan con secuencias diana RNA ribosómicas (16SrRNA), DNA ribosómico (16S rDNA) y técnicas de amplificación de genes (PCR) en lesiones cutáneas de pacientes de lepra infantil y el efecto del tratamiento farmacológico sobre estas técnicas. Se incluyeron en este trabajo 80 pacientes de lepra infantil. La mayoría de caso (79%) tenía entre 9-16 años. Se dividieron los caso en 3 grupos de acuerdo con el tratamiento, sin tratar (30) en tratamiento (39) y al finalizar el tratamiento (20). Se efectuaron exámenes clínicos y baciloscopia para la detección de bacilos ácido-alcohol resistente BAAR y de las biopsias se extrajeron y fraccionaron los ácidos nucleídos. Se detectó rRNA y rDNA 16S específico de M.leprae mediante hibridación con sondas, mientras que la secuencia del gen 36 kDa se detectó mediante técnicas de amplificación de genes (PCR). Los casos se clasificaron en lepra paucibacilar (PB) y multibacilar (MB) de acuerdo a los criterios de la OMS (1988). La positividad del rRNA 16S en los casos PB disminuyó desde 60% en los casos no tratados al 10,5% después de 4-8 meses de tratamietno, mientras el rDNA 16S disminuyó del 50% al 21% y con PCR desde 70% al 36.8% para la misma muestra y todos se negativizaron al año. La misma tendencia se observó en el grupo MB, donde la positividad en los casos baciloscopia positivos decreció desde el 100% al 56,2% con rRNA 16S y al 42,8% con rDNA 16S y PCR respectivamente, después de los 9-12 meses de tratamiento, siendo a los 2 años todos negativos, menos un caso que permaneció positivo con PCR. Los casos MB con baciloscopia negativa siguieron la misma tendencia, 100% de positividad detectado por rRNA 16S y PCR, 75% detectado por rDNA 16S y decreció hasta la negatividad a los 9-12 meses de tratamiento. Estos resultados apuntan hacia un posible potencial de estas técnicas como apoyo molecular para el diagnóstico de casos MB baciloscopia negativos y el control de la respuesta al tratamiento. Sin embargo, la prueba definitiva exige ser valorada mediante estudios prospectivos de seguimiento

Nucleic acid sequences of Mycobacterium leprae were detected using gene probes hybridizing with targeting ribosomal RNA (16S rRNA), ribosomal DNA (16s rDNA) and gene amplification techniques (PCR) in skin lesion of paediatric leprosy patients and the effect of treatment on the by these methods. Eighty paediatric leprosy patients were included in the study. Most cases (79%) were between 9 and 16 years of age. Cases were divided into three groups according to treatment status, viz- untreated (30=, undergoing treatment (30), and at the end to treatment (20). Clinical and slit smear examination for acid fast bacilli (AFB) was performed and nucleic acids were extracted and fractionated form skin biopsies. M. leprae specific 16S rRNA and 16S rDNA was detected by hybridization with gene probes whereas the 36kKa gene sequence was detected by a gene amplification assay (PCR). The cases were classified as paucibacillary (PB) and multibacillary (MB) by the standard criteria of WHO (1988). Positivity of 16S rRNA in PB cases decreased from 60% in untreated to 10.5% after 4-8 months of treatment whereas for 16S rDNA, it decreased from 50% to 21% for PCR form 70% to 36.8% for the same specimen, and all became negative at 1 year. Similar trends were seen in MB cases where positivity in smear positive untreated cases decreased from 100% to 56.2% with 16S rRNA and 42.8% with 16S rDNA and PCR, respectively, after 9-12 months of treatment and all became negative at 2 years except one case which remained positive with PCR. Similar results were observed in smear negative MB cases, 100% positivity detected by 16S r RNA and PCR, 75% detected by 16S rDNA decreased to zero after 9-12 months of therapy. This study suggests the potential usefulness of gene probes targeting 16S rRNA and 16S rDNA and PCR as supportive molecular tools for diagnosis of smear negative evolving MB disease and also monitoring the response to treatment, these observation however, needs to be validated in prospective follow up studies