Enhanced In Vitro and In Vivo Potency of a T Cell Epitope in the Ebola Virus Glycoprotein Following Amino Acid Replacement at HLA-A*02:01 Binding Positions.

Studies on Ebola virus disease (EVD) survivors and clinical studies on Ebola virus (EBOV) vaccine candidates have pinpointed the importance of a strong antibody response in protection and survival from EBOV infection. However, little is known about the T cell responses to EBOV or EBOV vaccines. We used HLA-A*02:01 (HLA-A2) transgenic mice to study HLA-A2-specific T cell responses elicited following vaccination with EBOV glycoprotein (EBOV-GP) presented with three different systems: (i) recombinant protein (rEBOV-GP), (ii) vesicular stomatitis replication-competent recombinant virus (VSV-EBOV-GP), and (iii) modified vaccinia Ankara virus recombinant (MVA-EBOV-GP). T cells from immunized animals were analyzed using peptide pools representing the entire GP region and individual peptides. Regardless of the vaccine formulation, we identified a minimal 9mer epitope containing an HLA-A2 motif (FLDPATTS), which was confirmed through HLA-A2 binding affinity and immunization studies. Using binding prediction software, we identified substitutions surrounding position 9 (S9V, P10V, and Q11V) that predicted enhanced binding to the HLA-A2 molecule. This enhanced binding was confirmed through in vitro binding studies and enhanced potency was shown with in vivo immunization studies using the enhanced sequences and the wild-type sequence. Of note, in silico studies predicted the enhanced 9mer epitope carrying the S9V substitution as the best overall HLA-A2 epitope for the full-length EBOV-GP. These results suggest that EBOV-GP-S9V and EBOV-GP-P10V represent more potent in vivo immunogens. Identification and enhancement of EBOV-specific human HLA epitopes could lead to the development of tools and reagents to induce more robust T cell responses in human subjects. IMPORTANCE Vaccine efficacy and immunity to viral infection are often measured by neutralizing antibody titers. T cells are specialized subsets of immune cells with antiviral activity, but this response is variable and difficult to track. We showed that the HLA-A2-specific T cell response to the Ebola virus glycoprotein can be enhanced significantly by a single residue substitution designed to improve an epitope binding affinity to one of the most frequent MHC alleles in the human population. This strategy could be applied to improve T cell responses to Ebola vaccines designed to elicit antibodies and adapted to target MHC alleles of populations in regions where endemic infections, like Ebola virus disease, are still causing outbreaks with concerning pandemic potential.

Assessing the impact of hepatitis B immune globulin (HBIG) on responses to hepatitis B vaccine during co-administration.

INTRODUCTION: A hepatitis B vaccination (HepB) series with an initial dose of hepatitis B immune globulin (HBIG) is the recommended prophylaxis for infants born to mothers with chronic hepatitis B virus (HBV) infection and for HBV-exposed persons without known protection. The HepB and HBIG are administered at different sites (limbs). Instances of HepB and HBIG administered at the same site are documented but the impact on immune responses to HepB remains unanswered. METHODS: Newborn and adult BALB/c mice received one dose of HepB at time zero alone or with HBIG in the same or different sites, followed by 2 additional doses of HepB at 3 and 10 weeks (newborn mice) or 4 and 16 weeks (adult mice). To study memory responses mice were given a 4th, booster, dose of HepB at 26 weeks and B cells analyzed. RESULTS: Administration of HepB with HBIG resulted in reduced responses to HepB following the first 2 doses, regardless of site, compared to mice that received HepB only. Lower levels of antibody to HBV surface antigen (anti-HBs) were observed at the end of the 3-dose series (p < 0.0001) in all groups of newborn mice that received HepB and HBIG. In adult mice, this difference was only seen when HepB and HBIG were delivered at the same site. However, following a HepB booster at 26 weeks, HBsAg-specific B-cell expansion and memory phenotype were not impacted by initial HBIG administration CONCLUSION: Administration of HBIG with HepB can delay and reduce responses to HepB in mice. Our findings suggest that the initial circulating levels of HBIG could prevent infection despite an impaired response to vaccine and support the current recommendation of assessing seroprotection after series completion for infants born to HBV carrier mothers, including in cases where vaccine and HBIG are administered incorrectly at the same site.

NUMB as a Therapeutic Target for Melanoma.

The upregulation of the adaptor protein NUMB triggers melanocytic differentiation from multipotent skin stem cells, which share many properties with aggressive melanoma cells. Although NUMB acts as a tumor suppressor in various human cancer types, little is known about its role in melanoma. In this study, we investigated the role of NUMB in melanoma progression and its regulatory mechanism. Analysis of The Cancer Genome Atlas melanoma datasets revealed that high NUMB expression in melanoma tissues correlates with improved patient survival. Moreover, NUMB expression is downregulated in metastatic melanoma cells. NUMB knockdown significantly increased the invasion potential of melanoma cells in a three-dimensional collagen matrix in vitro and in the lungs of a mouse model in vivo; it also significantly upregulated the expression of the NOTCH target gene CCNE. Previous studies suggested that Wnt signaling increases NUMB expression. By mimicking Wnt stimulation through glycogen synthase kinase-3 inhibition, we increased NUMB expression in melanoma cells. Furthermore, a glycogen synthase kinase-3 inhibitor reduced the invasion of melanoma cells in a NUMB-dependent manner. Together, our results suggest that NUMB suppresses invasion and metastasis in melanoma, potentially through its regulation of the NOTCH‒CCNE axis and that the inhibitors that upregulate NUMB can exert therapeutic effects in melanoma.