Biology subjects

Brinkkemper, M.

Publications and source records attributed to Brinkkemper, M..

9 recordsLinked to original sources

bioRxiv2026

Adjuvant selection for optimally balanced humoral and cellular immunity induced by SARS-CoV-2 Spike virosome vaccines

Current SARS-CoV-2 vaccines provide limited breadth of protection, underscoring the need for vaccine strategies that optimize immune responses. Virosomesoffer a modular vaccine platform that enables multivalent antigen display and incorporation of adjuvants which can steer immune responses. We evaluated the immune response in BALB/c mice with virosomes displaying SARS-CoV-2 Wuhan or Delta spike antigens and coupled with various distinct adjuvants. Adjuvant selection differentially influenced both humoral and cellular immune outcomes. The TLR7/8 agonist 3M -052 induced a strong Th1-biased response, characterized by elevated IgG2a/IgG1 ratios and robust type 1 cytokine induction with suppression of Th2-associated cytokines. In contrast, the saponin QS-21 enhanced antibody functional quality, illustrated by improved virus neutralization potency and breadth. Furthermore, the combined incorporation of both 3M-052 and QS-21 induced an elevated Th1-biased response without improving neutralization capacity. In conclusion, different adjuvants added onto our virosome-basedvaccine led to distinct antibody responses and splenic T-cell profiles, reflective of differences in immune programming. This information guides the selection of adjuvants for respiratory virus vaccines.

immunology↗

bioRxiv2024

Broadening sarbecovirus neutralization with bispecific antibodies combining distinct conserved targets on the receptor binding domain

Monoclonal neutralizing antibodies (mAbs) are considered an important prophylactic against SARS-CoV-2 infection in at-risk populations and a strategy to counteract future sarbecovirus-induced disease. However, most mAbs isolated so far neutralize only a few sarbecovirus strains. Therefore, there is a growing interest in bispecific antibodies (bsAbs) which can simultaneously target different spike epitopes and thereby increase neutralizing breadth and prevent viral escape. Here, we generate and characterize a panel of 30 novel broadly reactive bsAbs using an efficient controlled Fab-arm exchange protocol. We specifically combine some of the broadest mAbs described so far, which target conserved epitopes on the receptor binding domain (RBD). Several bsAbs show superior cross-binding and neutralization compared to the parental mAbs against sarbecoviruses from diverse clades, including recent SARS-CoV-2 variants. BsAbs which include mAb COVA2-02 are among the most potent and broad combinations. As a result, we study the unknown epitope of COVA2-02 and show that this mAb targets a distinct conserved region at the base of the RBD, which could be of interest when designing next-generation bsAb constructs to contribute to a better pandemic preparedness.

microbiology↗

bioRxiv2023

Triple tandem trimer immunogens for HIV-1 and influenza nucleic acid-based vaccines

Recombinant native-like HIV-1 envelope glycoprotein (Env) trimers are used in candidate vaccines aimed at inducing broadly neutralizing antibodies. While state-of-the-art SOSIP or single-chain Env designs can be expressed as native-like trimers, undesired monomers, dimers and malformed trimers that elicit non-neutralizing antibodies are also formed, implying that these designs could benefit from further modifications for gene-based vaccination approaches. Here, we describe the triple tandem trimer (TTT) design in which three Env protomers are genetically linked in a single open reading frame and express as native-like trimers. Viral vectored Env TTT induced similar neutralization titers but with a higher proportion of trimer-specific responses. The TTT design was also applied to generate influenza hemagglutinin (HA) trimers without the need for trimerization domains. Additionally, we used TTT to generate well-folded chimeric Env and HA trimers that harbor protomers from three different strains. In summary, the TTT design is a useful platform for the design of HIV-1 Env and influenza HA immunogens for a multitude of vaccination strategies.

microbiology↗

bioRxiv2022

Bispecific antibodies combine breadth, potency, and avidity of parental antibodies to neutralize sarbecoviruses

SARS-CoV-2 mutational variants evade humoral immune responses elicited by vaccines and current monoclonal antibody (mAb) therapies. Novel antibody-based treatments will thus need to exhibit broad neutralization against different variants. Bispecific antibodies (bsAbs) combine the specificities of two distinct antibodies into one antibody taking advantage of the avidity, synergy and cooperativity provided by targeting two different epitopes. Here we used controlled Fab-arm exchange (cFAE), a versatile and straightforward method, to produce bsAbs that neutralize SARS-CoV and SARS-CoV-2 variants, including Omicron and its subvariants, by combining potent SARS-CoV-2-specific neutralizing antibodies with broader but less potent antibodies that also neutralize SARS-CoV. We demonstrate that the parental IgGs rely on avidity for their neutralizing activity by comparing their potency to bsAbs containing one irrelevant "dead" Fab arm. We used single particle mass photometry to measure formation of antibody:spike complexes, and determined that bsAbs increase binding stoichiometry compared to corresponding cocktails, without a loss of binding affinity. The heterogeneous binding pattern of bsAbs to spike (S), observed by negative-stain electron microscopy and mass photometry provided evidence for both intra- and inter-spike crosslinking. This study highlights the utility of cross-neutralizing antibodies for designing bivalent or multivalent agents to provide a robust activity against circulating variants, as well as future SARS-like coronaviruses.

immunology↗

bioRxiv2022

CD4 binding-site antibodies induced by a subtype B HIV-1 envelope trimer

In the last decade considerable advances have been made towards the design of HIV-1 vaccines that induce neutralizing antibodies (NAbs). Despite the progress, no vaccine is able to consistently elicited broadly neutralizing antibodies (bNAbs). Here we present a case study of a rabbit that was immunized with a subtype B native like envelope glycoprotein (Env) trimer, AMC016 SOSIP.v4.2, with a dense and intact glycan shield, followed by a trivalent combination of subtype B trimers. After the priming phase serum from this animal neutralized several heterologous subtype B neutralization resistant (tier 2) viruses. Subsequent immunization with the trivalent combination of subtype B trimers further increased the breadth and potency of the NAb response. EM based polyclonal epitope mapping revealed that a cross reactive CD4 binding-site (CD4bs) antibody response, that was present after priming with the monovalent trimer and boosting with the trivalent combination, was most likely responsible for the broad neutralization. While anecdotal, this study provides proof-of-concept that native-like Env trimers are capable of inducing CD4bs-directed bNAb responses and should guide efforts to improve the consistency with which such responses are generated.

immunology↗

bioRxiv2021

A public antibody class recognizes a novel S2 epitope exposed on open conformations of SARS-CoV-2 spike

Delineating the origins and properties of antibodies elicited by SARS-CoV-2 infection and vaccination is critical for understanding their benefits and potential shortcomings. Therefore, we investigated the SARS-CoV-2 spike (S)-reactive B cell repertoire in unexposed individuals by flow cytometry and single-cell sequencing. We found that [~]82% of SARS-CoV-2 S-reactive B cells show a naive phenotype, which represents an unusually high fraction of total human naive B cells ([~]0.1%). Approximately 10% of these naive S-reactive B cells shared an IGHV1-69/IGKV3-11 B cell receptor pairing, an enrichment of 18-fold compared to the complete naive repertoire. A proportion of memory B cells, comprising switched ([~]0.05%) and unswitched B cells ([~]0.04%), was also reactive with S and some of these cells were reactive with ADAMTS13, which is associated with thrombotic thrombocytopenia. Following SARS-CoV-2 infection, we report an average 37-fold enrichment of IGHV1-69/IGKV3-11 B cell receptor pairing in the S-reactive memory B cells compared to the unselected memory repertoire. This class of B cells targets a previously undefined non-neutralizing epitope on the S2 subunit that becomes exposed on S proteins used in approved vaccines when they transition away from the native pre-fusion state because of instability. These findings can help guide the improvement of SARS-CoV-2 vaccines.

immunology↗

bioRxiv2021

SARS-CoV-2 infection activates dendritic cells via cytosolic receptors rather than extracellular TLRs

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), an infectious disease characterized by strong induction of inflammatory cytokines, progressive lung inflammation and potentially multi-organ dysfunction. It remains unclear whether SARS-CoV-2 is sensed by pattern recognition receptors (PRRs) leading to immune activation. Several studies suggest that the Spike (S) protein of SARS-CoV-2 might interact with Toll-like receptor 4 (TLR4) and thereby activate immunity. Here we have investigated the role of TLR4 in SARS-CoV-2 infection and immunity. Neither exposure of isolated S protein, SARS-CoV-2 pseudovirus nor a primary SARS-CoV-2 isolate induced TLR4 activation in a TLR4-expressing cell line. Human monocyte-derived dendritic cells (DCs) express TLR4 but not ACE2, and DCs were not infected by a primary SARS-CoV-2 isolate. Notably, neither S protein nor the primary SARS-CoV-2 isolate induced DC maturation or cytokines, indicating that both S protein and SARS-CoV-2 virus particles do not trigger extracellular TLRs, including TLR4. Ectopic expression of ACE2 in DCs led to efficient infection by SARS-CoV-2. Strikingly, infection of ACE2-positive DCs induced type I IFN and cytokine responses, which was inhibited by antibodies against ACE2. These data strongly suggest that not extracellular TLRs but intracellular viral sensors are key players in sensing SARS-CoV-2. These data imply that SARS-CoV-2 escapes direct sensing by TLRs, which might underlie the lack of efficient immunity to SARS-CoV-2 early during infection. Author summaryThe immune system needs to recognize pathogens such as SARS-CoV-2 to initiate antiviral immunity. Dendritic cells (DCs) are crucial for inducing antiviral immunity and are therefore equipped with both extracellular and intracellular pattern recognition receptors to sense pathogens. However, it is unknown if and how SARS-CoV-2 activates DCs. Recent research suggests that SARS-CoV-2 is sensed by extracellular Toll-like receptor 4 (TLR4). We have previously shown that DCs do not express ACE2, and are therefore not infected by SARS-CoV-2. Here we show that DCs do not become activated by exposure to viral Spike proteins or SARS-CoV-2 virus particles. These findings suggest that TLR4 and other extracellular TLRs do not sense SARS-CoV-2. Next, we expressed ACE2 in DCs and SARS-CoV-2 efficiently infected these ACE2-positive DCs. Notably, infection of ACE2-positive DCs induced an antiviral immune response. Thus, our study suggests that infection of DCs is required for induction of immunity, and thus that intracellular viral sensors rather than extracellular TLRs are important in sensing SARS-CoV-2. Lack of sensing by extracellular TLRs might be an escape mechanism of SARS-CoV-2 and could contribute to the aberrant immune responses observed during COVID-19.

immunology↗

bioRxiv2021

Probing Affinity, Avidity, Anti-Cooperativity, and Competition in Antibody and Receptor Binding to the SARS-CoV-2 Spike by Single Particle Mass Analyses

Determining how antibodies interact with the spike (S) protein of the SARS-CoV-2 virus is critical for combating COVID-19. Structural studies typically employ simplified, truncated constructs that may not fully recapitulate the behaviour of the original complexes. Here, we combine two single particle mass analysis techniques (mass photometry and charge-detection mass spectrometry) to enable measurement of full IgG binding to the trimeric SARS-CoV-2 S ectodomain. Our experiments reveal that antibodies targeting the S-trimer typically prefer stoichiometries lower than the symmetry-predicted 3:1 binding. We determine that this behaviour arises from the interplay of steric clashes and avidity effects that are not reflected in common antibody constructs (i.e. Fabs). Surprisingly, these sub-stoichiometric complexes are fully effective at blocking ACE2 binding despite containing free receptor binding sites. Our results highlight the importance of studying antibody/antigen interactions using complete, multimeric constructs and showcase the utility of single particle mass analyses in unraveling these complex interactions.

immunology↗

bioRxiv2020

Two-component spike nanoparticle vaccine protects macaques from SARS-CoV-2 infection

The SARS-CoV-2 pandemic is continuing to disrupt personal lives, global healthcare systems and economies. Hence, there is an urgent need for a vaccine that prevents viral infection, transmission and disease. Here, we present a two-component protein-based nanoparticle vaccine that displays multiple copies of the SARS-CoV-2 spike protein. Immunization studies show that this vaccine induces potent neutralizing antibody responses in mice, rabbits and cynomolgus macaques. The vaccine-induced immunity protected macaques against a high dose challenge, resulting in strongly reduced viral infection and replication in upper and lower airways. These nanoparticles are a promising vaccine candidate to curtail the SARS-CoV-2 pandemic.

immunology↗