Probes for INS

Cassava brown streak disease (CBSD) is a destructive disease of cassava in Eastern and Central Africa. Because there was no source of resistance in African varieties to provide complete protection against the viruses causing the disease, we searched in South American germplasm and identified cassava lines that did not become infected with the cassava brown streak viruses. These findings motivated further investigations into the mechanism of virus resistance. We used RNAscope in situ hybridization to localize cassava brown streak virus in cassava germplasm lines that were highly resistant (DSC 167, immune) or that restricted virus infections to stems and roots only (DSC 260). We show that the resistance in those lines is not a restriction of long-distance movement but due to preventing virus unloading from the phloem into parenchyma cells for replication, thus restricting the virus to the phloem cells only. When DSC 167 and DSC 260 were compared for virus invasion, only a low CBSV signal was found in phloem tissue of DSC 167, indicating that there is no replication in this host, while the presence of intense hybridization signals in the phloem of DSC 260 provided evidence for virus replication in companion cells. In neither of the two lines studied was there evidence of virus replication outside the phloem tissues. Thus, we conclude that in resistant cassava lines, CBSV is confined to the phloem tissues only, in which virus replication can still take place or is arrested.

Cassava Brown Streak Virus (CBSV) and Ugandan Cassava Brown Streak Virus (UCBSV) are the two among six virus species speculated to cause the most catastrophic Brown Streak Disease of Cassava (CBSD) in Africa and Asia. For unknown reasons, Cassava Brown Streak Virus (CBSV) is hard to breed resistance for compared to Ugandan Cassava Brown Streak Virus (UCBSV) species. This exemplified by incidences of CBSV species rather than UCBSV species in elite breeding line, KBH 2006/0026 at Bagamoyo, Tanzania. It is not yet understood as to why CBSV species could cause resistance-breakdown in the KBH 2006/0026, unlike the UCBSV species. This marks the first in in silico study conducted to understand molecular basis for the trait discrepancy between CBSV and UCBSV species from structural biology view point, as trait disparity between them might have an interplay in the observed phenomenon. Following ab initio modelling and analysis of physical-chemical properties of second 6-kilodalton (6K2) protein encoded by CBSV and UCBSV species, using ROBETTA server and Protein Parameters tool, respectively we report that; three dimensional (3D) structures and polarity of the protein differs significantly between the two virus species. (95% and 5%) and (85% and 15%) strains of 20 CBSV and 20 UCBSV species respectively, expressed the protein in homo-trimeric and homo-tetrameric forms, correspondingly. 95% and 85% of studied strain population of the two virus species expressed hydrophilic and hydrophobic 6K2, respectively. The hydrophilic 6K2 expressed by the CBSV species, favour its faster systemic spread via vascular tissues of cassava compared to the hydrophobic 6K2 expressed by the UCBSV species. We hypothesize that, the hydrophilic 6K2 gives CBSV species interaction advantage with Nuclear Inclusion b protease domain (NIb) and Viral genome-linked protein (VPg), components of Virus Replication Complex (VRC) than the hydrophobic 6K2 expressed by UCBSV species. Experimental studies are needed to resolve 3D structures of 6K2, VPg and NIb and comprehend complex molecular interactions between them. We suggest that, 6K2 gene should be targeted for improvement of RNA interference (RNAi)-directed transgenesis of virus-resistant cassava as a more effective way to control the CBSD besides breeding.

Despite occasional reports of SARS-CoV-2 vertical transmission during pregnancy, the question of placental infection and its consequences for the newborn remain questionable. Here, we analyzed the placentas of 31 COVID-19-positive mothers by RT-PCR, immunohistochemistry and in situ hybridization. We only detected one case of placental infection, which was associated with intrauterine demise of the fetus. We then isolated and differentiated primary trophoblasts from non-pathological human placentas at term, and exposed them to SARS-CoV-2 virions. Unlike for positive control cells Vero E6, we were not able to detect the virus inside cytotrophoblasts and syncytiotrophoblasts or in the supernatant four days after infection. As a mechanism of defense, we hypothesized that trophoblasts at term do not express ACE2 and TMPRSS, the two main host membrane receptors for SARS-CoV-2 entry. The quantification of these proteins in the placenta during pregnancy confirmed the absence of TMPRSS2 at the surface of the syncytium. Surprisingly, a transiently induced experimental expression of TMPRSS2 did not allow the entry or replication of the virus in differentiated trophoblasts. Altogether, these results underline that trophoblasts are not likely to be infected by SARS-CoV-2 at term, but the reported case raises concern about preterm infection.

It is unclear whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can directly infect human kidney, thus leading to acute kidney injury (AKI). Here, we perform a retrospective analysis of clinical parameters from 85 patients with laboratory-confirmed coronavirus disease 2019 (COVID-19); moreover, kidney histopathology from six additional COVID-19 patients with post-mortem examinations was performed. We find that 27% (23/85) of patients exhibited AKI. The elderly patients and cases with comorbidities (hypertension and heart failure) are more prone to develop AKI. Haematoxylin & eosin staining shows that the kidneys from COVID-19 autopsies have moderate to severe tubular damage. In situ hybridization assays illustrate that viral RNA accumulates in tubules. Immunohistochemistry shows nucleocapsid and spike protein deposits in the tubules, and immunofluorescence double staining shows that both antigens are restricted to the angiotensin converting enzyme-II-positive tubules. SARS-CoV-2 infection triggers the expression of hypoxic damage-associated molecules, including DP2 and prostaglandin D synthase in infected tubules. Moreover, it enhances CD68+ macrophages infiltration into the tubulointerstitium, and complement C5b-9 deposition on tubules is also observed. These results suggest that SARS-CoV-2 directly infects human kidney to mediate tubular pathogenesis and AKI.