Serine protease inhibitors interact with IFN-γ through up-regulation of FasR; a novel therapeutic strategy against cancer.

Among the many immunomodulatory and anti-tumor activities, IFN-γ up-regulates tumor cell death mediated by Fas receptor (FasR). Our and several other studies have demonstrated the involvement of trypsin-like proteases (TLPs) in the mode of action of IFN-γ. In the present study, we tried to unravel the role of serine proteases in IFN-γ induced Fas-mediated cell death. Our present results show that both tosyl-l-Lysine chloromethylketone (TLCK), a trypsin like protease inhibitor and tosyl-l-phenylalanine chloromethylketone (TPCK) - a chymotrypsin like protease (CLP) inhibitor, sensitize HeLa cells to Fas-mediated cell death. The combined effect of these protease inhibitors with anti-Fas was stronger than additive. In contrast, elastase inhibitor III (EI), which also contains the chloromethyl ketone moiety, was not active. Furthermore, co-addition of TLCK or TPCK with IFN-γ markedly enhanced Fas-induced cell death. IFN-γ led to up-regulation of FasR on its own, which was further enhanced by the co-addition of TLCK or TPCK. This was evident both by increased expression of Fas receptor on cell surface and by elevated Fas mRNA level. This study may provide the basis for the design of a novel combinatory therapeutic strategy that could enhance the eradication of tumors.

Functional reconstitution of the MERS CoV receptor binding motif.

In the early 1960's the first human coronaviruses (designated 229E and OC43) were identified as etiologic agents of the common cold, to be followed by the subsequent isolation of three more human coronaviruses similarly associated with cold-like diseases. In contrast to these "mild" coronaviruses, over the last 20 years there have been three independent events of emergence of pandemic severe and acute life-threatening respiratory diseases caused by three novel beta-coronaviruses, SARS CoV, MERS CoV and most recently SARS CoV2. Whereas the first SARS CoV appeared in November 2002 and spontaneously disappeared by the summer of 2003, MERS CoV has continued persistently to spill over to humans via an intermediary camel vector, causing tens of cases annually. Although human-to-human transmission is rare, the fatality rate of MERS CoV disease is remarkably higher than 30%. COVID-19 however, is fortunately much less fatal, despite that its etiologic agent, SARS CoV2, is tremendously infectious, particularly with the recent evolution of the Omicron variants of concern (BA.1 and BA.2). Of note, MERS CoV prevalence in camel populations in Africa and the Middle East is extremely high. Moreover, MERS CoV and SARS CoV2 co-exist in the Middle East and especially in Saudi Arabia and the UAE, where sporadic incidences of co-infection have already been reported. Co-infection, either due to reverse spill-over of SARS CoV2 to camels or in double infected humans could lead to recombination between the two viruses, rendering either SARS CoV2 more lethal or MERS CoV more transmittable. In an attempt to prepare for what could develop into a catastrophic event, we have focused on developing a novel epitope-based immunogen for MERS CoV. Implementing combinatorial phage-display conformer libraries, the Receptor Binding Motif (RBM) of the MERS CoV Spike protein has been successfully reconstituted and shown to be recognized by a panel of seven neutralizing monoclonal antibodies.