Extra-embryonic human Wharton's jelly stem cells do not induce tumorigenesis, unlike human embryonic stem cells.

Tumorigenesis is the major obstacle of tissues derived from human embryonic stem cells (ESC) and human induced pluripotent stem cell (IPSC) for transplantation therapy. This prompted a search for other sources of ESC. This study isolated and characterized stem cells from the extra-embryonic human umbilical cord Wharton's jelly (WJSC). These cells are non-controversial, available in abundance, proliferative, multipotent and hypoimmunogenic. However, their tumorigenic potential has not been properly addressed. Their tumour-producing capabilities were compared with human ESC using the immunodeficient mouse model. Unlabelled human ESC+matrigel (2×10(6)cells/site), labelled human WJSC (red fluorescent protein; 5×10(6)cells/site) and unlabelled human WJSC+matrigel (5×10(6)cells/site) were injected via three routes (s.c., i.m. and i.p.). Animals that received human ESC+matrigel developed teratomas in 6 weeks (s.c. 85%; i.m. 75%; i.p. 100%) that contained tissues of ectoderm, mesoderm and endoderm. No animal that received human WJSC developed tumours or inflammatory reactions at the injection sites when maintained for a prolonged period (20 weeks). Human WJSC produced increases in anti-inflammatory cytokines in contrast to human ESC, which increased pro-inflammatory cytokines. Human WJSC, being hypoimmunogenic and non-tumorigenic, have the potential for safe cell-based therapies.

Monoclonal antibodies for the S2 subunit of spike of SARS-CoV cross-react with the newly-emerged SARS-CoV-2

The emergence of a novel coronavirus, SARS-CoV-2, at the end of 2019 has resulted in widespread human infections across the globe. While genetically distinct from SARS-CoV, the etiological agent that caused an outbreak of severe acute respiratory syndrome (SARS) in 2003, both coronaviruses exhibit receptor binding domain (RBD) conservation and utilize the same host cell receptor, angiotensin-converting enzyme 2 (ACE2), for virus entry. Therefore, it will be important to test the cross-reactivity of antibodies that have been previously generated against the surface spike (S) glycoprotein of SARS-CoV in order to aid research on the newly emerged SARS-CoV-2. Here, we show that an immunogenic domain in the S2 subunit of SARS-CoV S is highly conserved in multiple strains of SARS-CoV-2. Consistently, four murine monoclonal antibodies (mAbs) raised against this immunogenic SARS-CoV fragment were able to recognise the S protein of SARS-CoV-2 expressed in a mammalian cell line. Importantly, one of them (mAb 1A9) was demonstrated to detect S in SARS-CoV-2-infected cells. To our knowledge, this is the first study showing that mAbs targeting the S2 domain of SARS-CoV can cross-react with SARS-CoV-2 and this observation is consistent with the high sequence conservation in the S2 subunit. These cross-reactive mAbs may serve as tools useful for SARS-CoV-2 research as well as for the development of diagnostic assays for its associated coronavirus disease COVID-19.