To understand the nature of negative responses through the B-cell antigen receptor (BCR), we have screened an expression cDNA library for the ability to block BCR-induced growth arrest and apoptosis in the immature B-cell line, WEHI-231. We isolated multiple copies of full-length, unmutated Bcl10, a signaling adaptor molecule encoded by a gene found to translocate to the immunoglobulin heavy chain (IgH) locus in some mucosa-associated lymphoid tissue ( IntroductionProper regulation of apoptosis is critical for the normal function of the immune system and for the prevention of bloodborne malignancies. B and T lymphocytes are normally subject to the induction of apoptotic cell death in the primary lymphoid organs, as exemplified by B-cell receptor/T-cell receptor (BCR/TCR)-induced apoptosis; and in the periphery, as exemplified by Fas-or cytokine deprivationinduced cell death. 1,2 Genetic changes that cause loss of apoptotic susceptibility are likely early events in the pathogenesis of many lymphoid cancers.To understand the regulation of B-cell apoptosis, WEHI-231, a lymphoma-derived B-cell line with an immature B-cell phenotype, has been frequently studied because it exhibits growth arrest and essentially 100% apoptosis in response to BCR crosslinking. 3 A number of factors known to be involved in B-cell oncogenesis have been shown to relieve or prevent BCR-induced growth arrest and/or apoptosis in WEHI-231 cells. These include the cell-cycle regulator c-Myc 4 and the B-cell lymphoma-2 (Bcl-2) family member, Bcl-xL. 5,6 Another lymphoma-related gene, BCL6, which inhibits B-cell terminal differentiation, displays abnormality at its genomic locus in these cells. 7 BCR-induced growth arrest and apoptosis of these cells are prevented by immunologic stimuli that promote activation of normal B cells, including lipopolysaccharide stimulation via Toll-like receptor 4 (TLR4) and helper T-cell stimulation via cytokines and CD40. 8 To understand the molecular events controlling B-cell fate in this system, we have taken a function-based approach and screened a cDNA expression library for genes that can abrogate BCR-induced apoptosis of WEHI-231 cells. From this screen, we isolated multiple copies of full-length, unmutated Bcl10.The human BCL10 gene was initially discovered via its involvement in a chromosomal translocation associated with a fraction of extranodal marginal zone B-cell lymphomas of mucosaassociated lymphoid tissue (MALT) and was also found to be mutated in some lymphoid and nonlymphoid malignancies. [9][10][11][12] Paradoxically, overexpression of Bcl10 in cell lines causes apoptosis. [13][14][15][16][17] Thus, the mechanism underlying the role of Bcl10 in lymphomagenesis remains to be clarified. Surprisingly, Bcl10-deficient mice were not found to have a defect in apoptosis, but they were found to have decreased numbers of all 3 types of mature B cells and to be defective in antigen receptor-induced activation of lymphocytes. 18,19 Subsequent studies have indicated that Bcl10 functions downstream of lympho...

Signaling by the BCR causes proliferation and resistance to Fas-induced apoptosis in mature B cells, but growth arrest and apoptosis in immature B cells. We have identified a variant of the immature B cell line WEHI 231 that retains the apoptotic response to the BCR but has acquired susceptibility to Fas-induced apoptosis. The Fas susceptibility was associated with increased Fas expression on the cell surface and down-regulated IgD expression. These cells exhibited a distinctive functional relationship in response to signals from the BCR, Fas and CD40: BCR stimulation markedly promoted Fas-mediated apoptosis (and vice versa) and Fas-induced apoptosis was not subject to modulation by CD40 signaling. While BCR-induced apoptosis was effectively rescued by CD40, it was not affected by the expression of a dominant-negative FADD. The mechanistic distinctions between BCR- and Fas-induced apoptosis were further characterized by the differential effects of different caspase inhibitors on these two processes which imply the involvement of different subsets of caspases. For BCR-induced apoptosis, we provide evidence that the final apoptotic destruction phase can be inhibited by the pan-caspase inhibitor BOC-Asp-FMK (BD) and that, in the presence of BD, the BCR only induces growth arrest which is reversible. The striking enhancing effects of Fas on BCR-induced apoptosis seen in the variant cells prompted us to examine if a similar cooperation in induction of apoptosis occurs in the highly tolerizable immature B cells of the spleen. We found that the splenic immature B population contains a significant number of Fas-expressing cells, but neither Fas-induced apoptosis nor an enhancing effect of Fas on BCR-induced apoptosis of these cells was detected in vitro.

The Src homology (SH2 and SH3) domains of v-Src are required for transformation of Rat-2 cells and for wild-type (morph') transformation of chicken embryo fibroblasts (CEFs). We report herein that the N-terminal domains of v-Src, when expressed in trans, cannot complement the transformation defect of a deletion mutant lacking the "unique," SH3, and SH2 regions. However, the same regions of Src can promote transformation when translocated to the C terminus of v-Src, although the transformation of CEFs is somewhat slower. We conclude that the SH3 and SH2 domains must be present in cis to the catalytic domain to promote transformation but that transformation is not dependent on the precise intramolecular location of these domains. In CEFs and in Rat-2 cells, the expression of wild-type v-Src results in tyrosine phosphorylation of proteins that bind to the v-Src SH3 and SH2 domains in vitro; mutations in the SH2 or SH3 and SH2 domains prevent the phosphorylation of these proteins. These findings are most consistent with models in which the SH3 and SH2 domains of v-Src directly or indirectly target the catalytic domain to substrates involved in transformation. However, the N-terminal domains of v-Src can promote tyrosine phosphorylation of certain proteins, in particular pl3oCas, even when expressed in the absence of the catalytic domain, indicating that the N-terminal domains of v-Src have effects that are independent of the catalytic domain.

Successful COVID-19 prevention requires additional measures beyond vaccination, social distancing, and masking. A nasal spray solution containing human IgG1 antibodies against SARS-CoV-2 (COVITRAP™) was developed to strengthen other COVID-19 preventive arsenals. Here, we evaluated its pseudovirus neutralization potencies, preclinical and clinical safety profiles, and intranasal SARS-CoV-2 inhibitory effects in healthy volunteers (NCT05358873). COVITRAP™ exhibited broadly potent neutralizing activities against SARS-CoV-2 with PVNT50 values ranging from 0.0035 to 3.1997 μg/ml for the following variants of concern (ranked from lowest to highest): Alpha, Beta, Gamma, Ancestral, Delta, Omicron BA.1, Omicron BA.2, Omicron BA.4/5, and Omicron BA.2.75. It demonstrated satisfactory preclinical safety profiles based on evaluations of in vitro cytotoxicity, skin sensitization, intracutaneous reactivity, and systemic toxicity. Its intranasal administration in rats did not yield any detected circulatory levels of the human IgG1 anti-SARS-CoV-2 antibodies at any time point during the 120 hours of follow-up. A double-blind, randomized, placebo-controlled trial (RCT) was conducted on 36 healthy volunteers who received either COVITRAP™ or a normal saline nasal spray at a 3:1 ratio. Safety of the thrice-daily intranasal administration for 7 days was assessed using nasal sinuscopy, adverse event recording, and self-reporting questionnaires. COVITRAP™ was well tolerated, with no significant adverse effects in healthy volunteers for the entire 14 days of the study. The intranasal SARS-CoV-2 inhibitory effects of COVITRAP™ were evaluated in nasal fluids taken from volunteers pre- and post-administration using a SARS-CoV-2 surrogate virus neutralization test. SARS-CoV-2 inhibitory effects in nasal fluids collected immediately or six hours after COVITRAP™ application were significantly increased from baseline for all three variants tested, including Ancestral, Delta, and Omicron BA.2. In conclusion, COVITRAP™ was safe for intranasal use in humans to provide SARS-CoV-2 inhibitory effects in nasal fluids that lasted at least six hours. Therefore, COVITRAP™ can be considered an integral instrument for COVID-19 prevention.