Biology subjects

Esterbauer, R.

Publications and source records attributed to Esterbauer, R..

8 recordsLinked to original sources

bioRxiv2026

Immunogen selection and prior immunity shape antibody breadth following immunisation with avian H5 hemagglutinin

Avian influenza A viruses pose a persistent zoonotic threat to humans owing to their expanding host range and high case fatality rates. In particular, viruses from the 2.3.4.4b clade of the H5 subtype have now been detected in over 60 mammalian species, raising serious pandemic concerns. Understanding immune recognition of the H5 hemagglutinin (HA) is therefore critical for effective vaccine design and pandemic preparedness. To understand the breadth of cross-recognition induced by different H5 strains, we selected genetically diverse H5 human isolates from 2003-2023 and assessed neutralising antibody responses elicited by adjuvanted recombinant HA protein-based vaccines in C57BL/6 mice. Neutralisation activity of sera was determined against seven H5 HA variants using pseudotyped viruses and a PR8-reassortant virus in micro-neutralisation assays. Our results showed a wide variety of cross-strain neutralisation across H5 HA antigen variants. The conventional vaccine strain A/Indonesia/05/2005 displayed narrow activity against emerging clade 2.3.4.4b viruses, whereas ancestral variants exhibited cross-neutralisation profiles showing a diversity of breath but with limited potency. Polyvalent H5 HA formulations and nanoparticle-displayed H5 HA platforms substantially broadened cross-neutralisation against diverse H5 strains. To examine the impact of pre-existing immunity on H5 vaccine immunogenicity in mouse models, mice were primed with either seasonal influenza infection or quadrivalent influenza vaccine (QIV) prior to H5 HA immunisation. QIV pre-vaccination, but not prior influenza infection, enhanced subsequent neutralizing responses towards A/Fujian-Sanyuan/21099/2017 (clade 2.3.4.4b) H5. Collectively, our results demonstrate that immunogen selection and prior immunity shape antibody breadth following immunisation with avian A(H5) hemagglutinin.

immunology↗

bioRxiv2026

Novel monoclonal antibodies targeting distinct sites on placental binding P. falciparum antigen VAR2CSA synergistically enhance parasite phagocytosis

Placental malaria, due to the sequestration of Plasmodium falciparum-infected erythrocytes (IE), causes adverse pregnancy outcomes. The sequestration is mediated by VAR2CSA, a protein that binds to placental chondroitin sulfate A (CSA). VAR2CSA antibodies protect against adverse pregnancy outcomes; however, no licensed VAR2CSA-based vaccine or therapeutic exists to date. We identified and expressed VAR2CSA-specific IgG1 monoclonal antibodies (mAbs) using B cells of malaria-exposed Papua New Guinean women. VAR2CSA mAbs were characterised by their ability to recognise eight heterologous CSA-binding P. falciparum strains, to neutralise CSA binding and/or to induce phagocytosis of IEs by THP-1 monocytes. We identified 16 mAbs, all of which targeted just two of the six domains of VAR2CSA, DBL3X and DBL5{varepsilon}. Cross-reactivity varied between mAbs, but was highest among mAbs to DBL5{varepsilon}, with four of eight of these mAbs binding to all eight strains. Although individual mAbs did not promote phagocytosis, combinations of mAbs recognising distinct epitopes either on the same domain or over different domains did. None of the mAbs inhibited IEs from binding to CSA. Our findings suggest that a combination of mAbs recognising more than one epitope would be needed for a therapeutic aiming to promote parasite clearance by phagocytosis; that DBL5{varepsilon} could be considered for a VAR2CSA vaccine that aims to elicit cross-reactive antibodies that promote phagocytosis; and that identification of binding-inhibitory mAbs requires thoughtful B-cell bait design.

microbiology↗

bioRxiv2025

Immunodominance is a poor predictor of vaccine-induced T follicular helper cell quality

Rational engineering of vaccine immunogens to focus B cell responses on potently neutralizing epitopes is a promising approach to improve the potency, breadth and durability of viral vaccines. Such strategies, however, can compromise vaccine immunogenicity through the unintended exclusion of CD4+ T cell epitopes, which are critical for the development of T follicular helper (TFH) cells and to support high affinity antibody production. Using a prototypic influenza HA stem immunogen lacking effective CD4+ T cell help in BL6 mice, we interrogated the minimal requirements for T cell help needed to drive serological responses to vaccination. We find that priming of naive CD4 T cells is markedly efficient, however the immunodominance of a given CD4 T cell epitope is not predictive of the propensity to provide high quality help to antigen-specific B cells. In the context of soluble antigens, provision of a single MHC class II epitope is sufficient to drive robust germinal centre responses and serum IgG titres. However not all CD4 epitopes provide equivalent levels of B cell help, despite priming comparable numbers of antigen-specific CD4 T cells. Finally, we show multimerizing and arraying antigens on nanoparticle scaffolds unlocks highly subdominant, near-undetectable CD4 T cell helper responses to support a T-dependent antibody response. Our findings emphasize the importance of CD4+ T cell help for programing robust and durable humoral immunity, and provide crucial insights to guide the rational incorporation of favorable T cell epitopes into vaccines.

immunology↗

bioRxiv2025

A novel chimeric coronavirus spike vaccine combining SARS-CoV-2 RBD and scaffold domains from HKU-1 elicits potent neutralising antibody responses

The receptor binding domain (RBD) of the SARS-CoV-2 spike is the major target for neutralising antibodies elicited by current vaccines. Using small domains such as the RBD as vaccine immunogens, however, may constrain the availability of CD4 T follicular helper (TFH) cells and impact immunogenicity. We engineered a novel chimeric trimeric RBD (CTR) glycoprotein, replacing the RBD of human coronavirus HKU-1 spike with SARS-CoV-2 RBD of either ancestral (WT) or Omicron BA.2 strains. This strategy maintains a native trimeric conformation of the RBD, while providing additional sources of CD4 T cell help via the HKU-1 spike scaffold. In C57BL/6 mice, CTR-BA.2 prime-boost vaccination elicited high anti-BA.2-RBD IgG and neutralising titres, matching responses in animals immunised with native SARS-CoV-2 spike proteins. GC B cells elicited by CTR-BA.2 were predominantly WT+/BA.2+ cross- reactive, and TFH cells predominantly recognised HKU-1 epitopes, demonstrating scaffold-directed T cell help. Macaques prime-boost immunised with CTR-WT similarly elicited high anti-RBD IgG, anti-spike IgG and neutralising responses, comparable to native spike-vaccinated animals. In draining lymph nodes of CTR-WT vaccinated macaques, RBD-specific GC B cells were present at elevated levels. In contrast to the murine studies, lymph node-draining TFH responses in macaques were broadly elicited against RBD, NTD/S2 or HKU-1-derived peptides. Although native SARS- CoV-2 spike was also highly immunogenic in animal models, our findings establish the chimeric glycoprotein design as a strategy to overcome the poor immunogenicity of the SARS-CoV-2 RBD by engaging CD4 TFH cells, while maintaining the ability to elicit protective neutralising responses. One sentence summaryA chimeric glycoprotein design preserves SARS-CoV-2 RBD antigenic conformation enabling elicitation of neutralising responses, while allowing recruitment of HKU-1 scaffold-directed CD4 helper responses to support the humoral response.

immunology↗

bioRxiv2025

Memory T and B cells with recognition of avian influenza hemagglutinins are poorly responsive to existing seasonal influenza vaccines

Immunisation remains the most cost-effective mechanism to combat global influenza infection and is widely employed against seasonal influenza viruses. Zoonotic transmission of avian influenza A viruses represents a significant threat to human health given the lack of population level immunity, which could translate into an influenza pandemic. Therefore, there is a need to better understand pre-existing human immunity against avian influenza strains. as highlighted by the recent rapid, global spread of avian H5Nx clade 2.3.4.4b variants. Here, we sought to quantify the frequencies and specificities of B cells recognising avian hemagglutinin (HA) within unexposed adults, and to characterise the ability of seasonal immunisation to boost cross-reactive immune responses to H5Nx strains, including from clade 2.3.4.4b. Low but detectable serum antibody titres against H5 and H7 avian influenza HA were observed in donors. The frequency of memory B cells with cross-reactive recognition of H5 and H7 HA was low and 2-5 fold lower than populations of seasonal H1N1 and H3N2 HA-specific B cells. Boosting of B cell responses against H5Nx clade 2.3.4.4b HA following seasonal immunisation were sporadic with only 3 out of 19 individuals showing an increased population of probe-positive cells. Cross-reactive B cells generally expressed immunoglobulins drawn from variable heavy chain genes associated with recognition of the HA stem (VH6-1, VH1-69, VH1-18). CD4+ T cell responses towards H5 HA were also weakly boosted with little to no increase in circulating T follicular helper cell populations. These findings highlight the need for avian influenza-specific vaccine products to bolster immunity in human populations, with consideration for use in pre-pandemic preparedness to expand baseline frequencies of avian influenza-specific memory B and T lymphocytes.

immunology↗

bioRxiv2023

Monoclonal antibodies against human coronavirus NL63 spike

The COVID-19 pandemic has illustrated the potential for monoclonal antibody therapeutics as prophylactic and therapeutic agents against pandemic viruses. No such therapeutics currently exist for other human coronaviruses. NL63 is a human alphacoronavirus that typically causes the common cold and uses the same receptor, ACE2, as the highly pathogenic SARS-CoV and SARS-CoV-2 pandemic viruses. In a cohort of healthy adults, we characterised humoral responses against the NL63 spike protein. While NL63 spike and receptor binding domain-specific binding antibodies and neutralisation activity could be detected in plasma of all subjects, memory B cells against NL63 spike were variable and relatively low in frequency compared to that against SARS-CoV-2 spike. From these donors, we isolated a panel of antibodies against NL63 spike and characterised their neutralising potential. We identified potent neutralising antibodies that recognised the receptor binding domain (RBD) and other non-RBD epitopes within spike.

microbiology↗

bioRxiv2020

Prime-boost protein subunit vaccines against SARS-CoV-2 are highly immunogenic in mice and macaques

SARS-CoV-2 vaccines are advancing into human clinical trials, with emphasis on eliciting high titres of neutralising antibodies against the viral spike (S). However, the merits of broadly targeting S versus focusing antibody onto the smaller receptor binding domain (RBD) are unclear. Here we assessed prototypic S and RBD subunit vaccines in homologous or heterologous prime-boost regimens in mice and non-human primates. We find S is highly immunogenic in mice, while the comparatively poor immunogenicity of RBD was associated with limiting germinal centre and T follicular helper cell activity. Boosting S-primed mice with either S or RBD significantly augmented neutralising titres, with RBD-focussing driving moderate improvement in serum neutralisation. In contrast, both S and RBD vaccines were comparably immunogenic in macaques, eliciting serological neutralising activity that generally exceed levels in convalescent humans. These studies confirm recombinant S proteins as promising vaccine candidates and highlight multiple pathways to achieving potent serological neutralisation.

immunology↗

bioRxiv2020

Coformulation with tattoo ink for immunological assessment of vaccine immunogenicity in the draining lymph node

Characterisation of germinal centre B and T cell responses yields critical insights into vaccine immunogenicity. Non-human primates are a key pre-clinical animal model for human vaccine development, allowing both lymph node and circulating immune responses to be longitudinally sampled for correlates of vaccine efficacy. However, patterns of vaccine antigen drainage via the lymphatics after intramuscular immunisation can be stochastic, driving uneven deposition between lymphoid sites, and between individual lymph nodes within larger clusters. In order to improve the accurate isolation of antigen-exposed lymph nodes during biopsies and necropsies, we developed and validated a method for co-formulating candidate vaccines with tattoo ink, which allows for direct visual identification of vaccine-draining lymph nodes and evaluation of relevant antigen-specific B and T cell responses by flow cytometry. This approach improves the assessment of vaccine-induced immunity in highly relevant non-human primate models.

immunology↗