Record Maximum Oscillation Frequency in C-face Epitaxial Graphene Transistors

The maximum oscillation frequency (fmax) quantifies the practical upper bound for useful circuit operation. We report here an fmax of 70 GHz in transistors using epitaxial graphene grown on the C-face of SiC. This is a significant improvement over Si-face epitaxial graphene used in the prior high frequency transistor studies, exemplifying the superior electronics potential of C-face epitaxial graphene. Careful transistor design using a high {\kappa} dielectric T-gate and self-aligned contacts, further contributed to the record-breaking fmax

Robust and prototypical immune responses towards COVID-19 BNT162b2 vaccines in Indigenous people

SARS-CoV-2 has led to >270 million infections and >5 million deaths globally. Indigenous people are disproportionately affected by infectious diseases, therefore also more susceptible to the COVID-19 pandemic. There are an estimated 476 million indigenous people globally, including an estimated 798,365 Aboriginal and Torres Strait Islander in Australia. With the high vulnerability to COVID-19, this knowledge is urgently needed to better protect indigenous populations. We evaluated a breadth of immune responses in indigenous (n=57) and non-indigenous (n=49) individuals after COVID-19 vaccination. We tested RBD antibodies, spike/RBD-probe-specific B cells, peptide stimulations with activation-induced marker (AIM) assay and intracellular cytokine staining. We found 22% and 34% seroconversion rates after 1st dose of BNT162b2 vaccine for Indigenous and non-indigenous individuals, respectively, which increased to 100% at 1-mth after 2nd dose for both groups. RBD-specific IgG levels in indigenous individuals at 1-mth after 2nd dose positively correlated with their body mass index. At 1-mth after the 2nd COVID-19 vaccination, CD4+ and CD8+ T cell responses via AIM expression and IFN-γ+TNF+ production was comparable between indigenous and non-indigenous individuals. We are also going to assess the longevity of antibodies and T cells. Therefore, COVID-19 vaccination induced similar immune responses in indigenous and non-indigenous individuals

Broad spectrum SARS‐CoV ‐2‐specific immunity in hospitalized First Nations peoples recovering from COVID ‐19

Indigenous peoples globally are at increased risk of COVID‐19‐associated morbidity and mortality. However, data that describe immune responses to SARS‐CoV‐2 infection in Indigenous populations are lacking. We evaluated immune responses in Australian First Nations peoples hospitalized with COVID‐19. Our work comprehensively mapped out inflammatory, humoral and adaptive immune responses following SARS‐CoV‐2 infection. Patients were recruited early following the lifting of strict public health measures in the Northern Territory, Australia, between November 2021 and May 2022. Australian First Nations peoples recovering from COVID‐19 showed increased levels of MCP‐1 and IL‐8 cytokines, IgG‐antibodies against Delta‐RBD and memory SARS‐CoV‐2‐specific T cell responses prior to hospital discharge in comparison with hospital admission, with resolution of hyperactivated HLA‐DR+CD38+ T cells. SARS‐CoV‐2 infection elicited coordinated ASC, Tfh and CD8+ T cell responses in concert with CD4+ T cell responses. Delta and Omicron RBD‐IgG, as well as Ancestral N‐IgG antibodies, strongly correlated with Ancestral RBD‐IgG antibodies and Spike‐specific memory B cells. We provide evidence of broad and robust immune responses following SARS‐CoV‐2 infection in Indigenous peoples, resembling those of non‐Indigenous COVID‐19 hospitalized patients

SARS-CoV-2-specific T cell memory with common TCRαβ motifs is established in unvaccinated children who seroconvert after infection

As establishment of SARS-CoV-2-specific T cell memory in children remains largely unexplored, we recruited convalescent COVID-19 children and adults to define their circulating memory SARS-CoV-2-specific CD4+ and CD8+ T cells prior to vaccination. We analysed epitope-specific T cells directly ex vivo using seven HLA class-I and class-II tetramers presenting SARS-CoV-2 epitopes, together with Spike-specific B cells. Unvaccinated children who seroconverted had comparable spike-specific, but lower ORF1a- and N-specific memory T cell responses compared to adults. This agreed with our TCR sequencing data showing reduced clonal expansion in children. A strong stem cell memory phenotype and common T cell receptor motifs were detected within tetramer-specific T cells in seroconverted children. Conversely, children who did not seroconvert had tetramer-specific T cells of predominantly naïve phenotypes and diverse TCRαβ repertoires. Our study demonstrates generation of SARS-CoV-2-specific T cell memory with common TCRαβ motifs in unvaccinated seroconverted children after their first virus encounter

CD8+ T cells specific for an immunodominant SARS-CoV-2 nucleocapsid epitope display high naive precursor frequency and TCR promiscuity

To better understand primary and recall T cell responses during coronavirus disease 2019 (COVID-19), it is important to examine unmanipulated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells. By using peptide-human leukocyte antigen (HLA) tetramers for direct ex vivo analysis, we characterized CD8+ T cells specific for SARS-CoV-2 epitopes in COVID-19 patients and unexposed individuals. Unlike CD8+ T cells directed toward subdominant epitopes (B7/N257, A2/S269, and A24/S1,208) CD8+ T cells specific for the immunodominant B7/N105 epitope were detected at high frequencies in pre-pandemic samples and at increased frequencies during acute COVID-19 and convalescence. SARS-CoV-2-specific CD8+ T cells in pre-pandemic samples from children, adults, and elderly individuals predominantly displayed a naive phenotype, indicating a lack of previous cross-reactive exposures. T cell receptor (TCR) analyses revealed diverse TCRαβ repertoires and promiscuous αβ-TCR pairing within B7/N105+CD8+ T cells. Our study demonstrates high naive precursor frequency and TCRαβ diversity within immunodominant B7/N105-specific CD8+ T cells and provides insight into SARS-CoV-2-specific T cell origins and subsequent responses

Robust and prototypical immune responses toward COVID-19 vaccine in First Nations peoples are impacted by comorbidities

High-risk groups, including Indigenous people, are at risk of severe COVID-19. Here we found that Australian First Nations peoples elicit effective immune responses to COVID-19 BNT162b2 vaccination, including neutralizing antibodies, receptor-binding domain (RBD) antibodies, SARS-CoV-2 spike-specific B cells, and CD4+ and CD8+ T cells. In First Nations participants, RBD IgG antibody titers were correlated with body mass index and negatively correlated with age. Reduced RBD antibodies, spike-specific B cells and follicular helper T cells were found in vaccinated participants with chronic conditions (diabetes, renal disease) and were strongly associated with altered glycosylation of IgG and increased interleukin-18 levels in the plasma. These immune perturbations were also found in non-Indigenous people with comorbidities, indicating that they were related to comorbidities rather than ethnicity. However, our study is of a great importance to First Nations peoples who have disproportionate rates of chronic comorbidities and provides evidence of robust immune responses after COVID-19 vaccination in Indigenous people

Robust SARS-CoV-2 T cell responses with common TCR?? motifs toward COVID-19 vaccines in patients with hematological malignancy impacting B cells

Immunocompromised hematology patients are vulnerable to severe COVID-19 and respond poorly to vaccination. Relative deficits in immunity are, however, unclear, especially after 3 vaccine doses. We evaluated immune responses in hematology patients across three COVID-19 vaccination doses. Seropositivity was low after a first dose of BNT162b2 and ChAdOx1 (∼26%), increased to 59%–75% after a second dose, and increased to 85% after a third dose. While prototypical antibody-secreting cells (ASCs) and T follicular helper (Tfh) cell responses were elicited in healthy participants, hematology patients showed prolonged ASCs and skewed Tfh2/17 responses. Importantly, vaccine-induced expansions of spike-specific and peptide-HLA tetramer-specific CD4+/CD8+ T cells, together with their T cell receptor (TCR) repertoires, were robust in hematology patients, irrespective of B cell numbers, and comparable to healthy participants. Vaccinated patients with breakthrough infections developed higher antibody responses, while T cell responses were comparable to healthy groups. COVID-19 vaccination induces robust T cell immunity in hematology patients of varying diseases and treatments irrespective of B cell numbers and antibody response