Hans J. Stauss

Most autosomal genetic causes of childhood-onset hypogammaglobulinemia are currently not well understood. Most affected individuals are simplex cases, but both autosomal-dominant and autosomal-recessive inheritance have been described. We performed genetic linkage analysis in consanguineous families affected by hypogammaglobulinemia. Four consanguineous families with childhood-onset humoral immune deficiency and features of autoimmunity shared genotype evidence for a linkage interval on chromosome 4q. Sequencing of positional candidate genes revealed that in each family, affected individuals had a distinct homozygous mutation in LRBA (lipopolysaccharide responsive beige-like anchor protein). All LRBA mutations segregated with the disease because homozygous individuals showed hypogammaglobulinemia and autoimmunity, whereas heterozygous individuals were healthy. These mutations were absent in healthy controls. Individuals with homozygous LRBA mutations had no LRBA, had disturbed B cell development, defective in vitro B cell activation, plasmablast formation, and immunoglobulin secretion, and had low proliferative responses. We conclude that mutations in LRBA cause an immune deficiency characterized by defects in B cell activation and autophagy and by susceptibility to apoptosis, all of which are associated with a clinical phenotype of hypogammaglobulinemia and autoimmunity.

Hematologic malignancies such as acute and chronic myeloid leukemia are characterized by the malignant transformation of immature CD34(+) progenitor cells. Transformation is associated with elevated expression of the Wilm's tumor gene encoded transcription factor (WT1). Here we demonstrate that WT1 can serve as a target for cytotoxic T lymphocytes (CTL) with exquisite specificity for leukemic progenitor cells. HLA-A0201- restricted CTL specific for WT1 kill leukemia cell lines and inhibit colony formation by transformed CD34(+) progenitor cells isolated from patients with chronic myeloid leukemia (CML), whereas colony formation by normal CD34(+) progenitor cells is unaffected. Thus, the tissue-specific transcription factor WT1 is an ideal target for CTL-mediated purging of leukemic progenitor cells in vitro and for antigen-specific therapy of leukemia and other WT1-expressing malignancies in vivo.

T cell responses to MHC-mismatched transplants can be mediated via direct recognition of allogeneic MHC molecules on the cells of the transplant or via recognition of allogeneic peptides presented on the surface of recipient APCs in recipient MHC molecules - a process known as indirect recognition. As CD4(+)CD25(+) Tregs play an important role in regulating alloresponses, we investigated whether mouse Tregs specific for allogeneic MHC molecules could be generated in vitro and could promote transplantation tolerance in immunocompetent recipient mice. Tregs able to directly recognize allogeneic MHC class II molecules (dTregs) were obtained by stimulating CD4(+)CD25(+) cells from C57BL/6 mice (H-2(b)) with allogeneic DCs from BALB/c mice (H-2(d)). To generate Tregs that indirectly recognized allogeneic MHC class II molecules, dTregs were retrovirally transduced with TCR genes conferring specificity for H-2K(d) presented by H-2A(b) MHC class II molecules. The dual direct and indirect allospecificity of the TCR-transduced Tregs was confirmed in vitro. In mice, TCR-transduced Tregs, but not dTregs, induced long-term survival of partially MHC-mismatched heart grafts when combined with short-term adjunctive immunosuppression. Further, although dTregs were only slightly less effective than TCR-transduced Tregs at inducing long-term survival of fully MHC-mismatched heart grafts, histologic analysis of long-surviving hearts demonstrated marked superiority of the TCR-transduced Tregs. Thus, Tregs specific for allogeneic MHC class II molecules are effective in promoting transplantation tolerance in mice, which suggests that such cells have clinical potential.

Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines show protective efficacy, which is most likely mediated by neutralizing antibodies recognizing the viral entry protein, spike. Because new SARS-CoV-2 variants are emerging rapidly, as exemplified by the B.1.1.7, B.1.351, and P.1 lineages, it is critical to understand whether antibody responses induced by infection with the original SARS-CoV-2 virus or current vaccines remain effective. In this study, we evaluate neutralization of a series of mutated spike pseudotypes based on divergence from SARS-CoV and then compare neutralization of the B.1.1.7 spike pseudotype and individual mutations. Spike-specific monoclonal antibody neutralization is reduced dramatically; in contrast, polyclonal antibodies from individuals infected in early 2020 remain active against most mutated spike pseudotypes, but potency is reduced in a minority of samples. This work highlights that changes in SARS-CoV-2 spike can alter neutralization sensitivity and underlines the need for effective real-time monitoring of emerging mutations and their effect on vaccine efficacy.