Novel H7N9 influenza immunogen design enhances mobilization of seasonal influenza T cell memory in H3N2 pre-immune mice

Strategies that improve influenza vaccine immunogenicity are critical for the development of vaccines for pandemic preparedness. Hemagglutinin (HA)-specific CD4⁺ T cell epitopes support protective B cell responses against seasonal influenza. However, in the case of avian H7N9, which poses a pandemic threat, HA elicits only weak neutralizing antibody responses in infection and vaccination without adjuvant. We hypothesized that an immune-engineered H7N9 HA incorporating a broadly reactive H3N2 HA-specific memory CD4⁺ T cell epitope that replaces a regulatory T cell-inducing epitope at the corresponding position in H7N9 HA could harness preexisting influenza T cell immunity to increase CD4⁺ T cells that are needed for protective antibody development. We designed and produced a virus-like particle (VLP) vaccine that carries the epitope augmented H7N9 HA (OPT1) and immunized HLA-DR3 transgenic mice with established H3N2 immunity. OPT1-VLPs stimulated higher stem cell, central, and effector memory CD4⁺ T cell levels over wild type VLP immunization. In addition, activated, IL-21-producing follicular helper T cell frequencies were enhanced. This novel immunogen design strategy illustrates that site-specific modifications aimed to augment T cell epitope content enhance CD4⁺ T cell responses among critical subpopulations capable of aiding protective immune responses upon antigen re-encounter and that mobilization of immune memory can be used to overcome the poor immunogenicity of avian influenza viruses.

Highly conserved, non-human-like, and cross-reactive SARS-CoV-2 T cell epitopes for COVID-19 vaccine design and validation

Natural and vaccine-induced SARS-CoV-2 immunity in humans has been described but correlates of protection are not yet defined. T cells support the SARS-CoV-2 antibody response, clear virus-infected cells, and may be required to block transmission. In this study, we identified peptide epitopes associated with SARS-CoV-2 T-cell immunity. Using immunoinformatic methods, T-cell epitopes from spike, membrane, and envelope were selected for maximal HLA-binding potential, coverage of HLA diversity, coverage of circulating virus, and minimal potential cross-reactivity with self. Direct restimulation of PBMCs collected from SARS-CoV-2 convalescents confirmed 66% of predicted epitopes, whereas only 9% were confirmed in naive individuals. However, following a brief period of epitope-specific T-cell expansion, both cohorts demonstrated robust T-cell responses to 97% of epitopes. HLA-DR3 transgenic mouse immunization with peptides co-formulated with poly-ICLC generated a potent Th1-skewed, epitope-specific memory response, alleviating safety concerns of enhanced respiratory disease associated with Th2 induction. Taken together, these epitopes may be used to improve our understanding of natural and vaccine-induced immunity, and to facilitate the development of T-cell-targeted vaccines that harness pre-existing SARS-CoV-2 immunity.

Immune-engineered H7N9 influenza hemagglutinin improves protection against viral influenza virus challenge

The influenza hemagglutinin (HA) isolated from avian H7N9 influenza virus strains elicit weak immune responses. This low immunogenicity may be due to a regulatory T cell (T_reg)-stimulating epitopes in HA from the H7N9 isolate A/Anhui/1/2013 (Anh/13). In this report, this T_reg stimulating sequence was removed from the wild-type (WT) H7 HA amino acid sequence and replaced with a conserved CD4 + T cell stimulating sequences from human seasonal H3N2 strains and designed OPT1 H7 HA. The effectiveness of this optimized H7 HA protein was determined using a humanized mouse (HLA-DR3) expressing the human leukocyte antigen (HLA) DR3 allele. HLA-DR3 mice were pre-immunized by infecting with H3N2 influenza virus, A/Hong Kong/4108/2014 and then vaccinated intramuscularly with either the WT H7 HA from Anh/13 or the OPT1 H7 HA antigen without adjuvant. The OPT1 H7 HA vaccination group elicited higher H7 HA-specific IgG titers that resulted in a lower mortality, weight loss, and lung viral titer following lethal challenge with the H7N9 Anh/13 influenza virus compared to WT-vaccinated mice. Overall, T-cell epitope-engineered vaccines can improve the immunogenicity of H7 HA antigens resulting in enhanced survival and lower morbidity against H7N9 influenza virus challenge.

Multi-element composition of soils of seasonal wetlands across North Dakota, USA

The main goal of this study was to assess if the soils of wetlands of different condition varied in terms of element composition. The rationale was that compared to wetlands of good condition, wetlands of poor condition-which in the region have typically been disturbed by agricultural activities, are lower in biodiversity and have fewer native species-would have been altered in their physical and chemical soil characteristics. This in turn would have altered the element composition of the soils. The concentrations of about 50 elements in the topsoil of 43 seasonal wetlands of varying condition, as measured by plant community based assessments, across North Dakota were determined. Organic matter content of the soils increased as condition increased, and it was the most important variable explaining 40 % of variation in the concentrations of elements. This can be partly explained by binding of elements to organic matter (S, Se) and for most other elements (that bind mostly to the inorganic fraction) by displacement by organic matter. The biogeochemistry of S is further implicated in the distribution of Ca, most likely via formation of insoluble gypsum (calcium sulfate).