Bivalent mRNA COVID vaccines elicit predominantly cross-reactive CD4+ T cell clonotypes

Bivalent COVID vaccines containing mRNA for ancestral and Omicron BA.5 spike proteins do not induce stronger T cell responses to Omicron BA.5 spike proteins than monovalent vaccines that contain only ancestral spike mRNA. The reasons for this finding have not been elucidated. Here, we show that healthy donors (HDs) and people living with HIV (PLWH) on antiretroviral therapy mostly target T cell epitopes that are not affected by BA.5 mutations. We use the functional expansion of specific T cells (FEST) assay to determine the percentage of CD4+ T cells that cross-recognize both spike proteins and those that are monoreactive for each protein. We show a predominance of cross-reactive CD4+ T cells; less than 10% percent of spike-specific CD4+ T cell receptors were BA.5 monoreactive in most HDs and PLWH. Our data suggest that the current bivalent vaccines do not induce robust BA.5-monoreactive T cell responses.

Proviral location affects cognate peptide-induced virus production and immune recognition of HIV-1-infected T cell clones

BACKGROUNDHIV-1-infected CD4+ T cells contribute to latent reservoir persistence by proliferating while avoiding immune recognition. Integration features of intact proviruses in elite controllers (ECs) and people on long-term therapy suggest that proviruses in specific chromosomal locations can evade immune surveillance. However, direct evidence of this mechanism is missing.METHODSIn this case report, we characterized integration sites and full genome sequences of expanded T cell clones in an EC before and after chemoradiation. We identified the cognate peptide of infected clones to investigate cell proliferation and virus production induced by T cell activation, and susceptibility to autologous CD8+ T cells.RESULTSThe proviral landscape was dominated by 2 large clones with replication-competent proviruses integrated into zinc finger (ZNF) genes (ZNF470 and ZNF721) in locations previously associated with deeper latency. A third nearly intact provirus, with a stop codon in Pol, was integrated into an intergenic site. Upon stimulation with cognate Gag peptides, infected clones proliferated extensively and produced virus, but the provirus in ZNF721 was 200-fold less inducible. While autologous CD8+ T cells decreased the proliferation of cells carrying the intergenic provirus, they had no effect on cells with the provirus in the ZNF721 gene.CONCLUSIONSWe provide direct evidence that upon activation of infected clones by cognate antigen, the lower inducibility of intact proviruses in ZNF genes can result in immune evasion and persistence.FUNDINGOffice of the NIH Director and National Institute of Dental & Craniofacial Research; NIAID, NIH; Johns Hopkins University Center for AIDS Research.

Lung tumor-infiltrating Treg have divergent transcriptional profiles and function linked to checkpoint blockade response

Regulatory T cells (Treg) are conventionally viewed as suppressors of endogenous and therapy-induced antitumor immunity; however, their role in modulating responses to immune checkpoint blockade (ICB) is unclear. In this study, we integrated single-cell RNA-seq/T cell receptor sequencing (TCRseq) of >73,000 tumor-infiltrating Treg (TIL-Treg) from anti-PD-1-treated and treatment-naive non-small cell lung cancers (NSCLC) with single-cell analysis of tumor-associated antigen (TAA)-specific Treg derived from a murine tumor model. We identified 10 subsets of human TIL-Treg, most of which have high concordance with murine TIL-Treg subsets. Only one subset selectively expresses high levels of TNFRSF4 (OX40) and TNFRSF18 (GITR), whose engangement by cognate ligand mediated proliferative programs and NF-κB activation, as well as multiple genes involved in Treg suppression, including LAG3. Functionally, the OX40hiGITRhi subset is the most highly suppressive ex vivo, and its higher representation among total TIL-Treg correlated with resistance to PD-1 blockade. Unexpectedly, in the murine tumor model, we found that virtually all TIL-Treg-expressing T cell receptors that are specific for TAA fully develop a distinct TH1-like signature over a 2-week period after entry into the tumor, down-regulating FoxP3 and up-regulating expression of TBX21 (Tbet), IFNG, and certain proinflammatory granzymes. Transfer learning of a gene score from the murine TAA-specific TH1-like Treg subset to the human single-cell dataset revealed a highly analogous subcluster that was enriched in anti-PD-1-responding tumors. These findings demonstrate that TIL-Treg partition into multiple distinct transcriptionally defined subsets with potentially opposing effects on ICB-induced antitumor immunity and suggest that TAA-specific TIL-Treg may positively contribute to antitumor responses.

Distinct Myeloid Derived Suppressor Cell Populations Promote Tumor Aggression in Glioblastoma

The diversity of genetic programs and cellular plasticity of glioma-associated myeloid cells, and thus their contribution to tumor growth and immune evasion, is poorly understood. We performed single cell RNA-sequencing of immune and tumor cells from 33 glioma patients of varying tumor grades. We identified two populations characteristic of myeloid derived suppressor cells (MDSC), unique to glioblastoma (GBM) and absent in grades II and III tumors: i) an early progenitor population (E-MDSC) characterized by strong upregulation of multiple catabolic, anabolic, oxidative stress, and hypoxia pathways typically observed within tumor cells themselves, and ii) a monocytic MDSC (M-MDSC) population. The E-MDSCs geographically co-localize with a subset of highly metabolic glioma stem-like tumor cells with a mesenchymal program in the pseudopalisading region, a pathognomonic feature of GBMs associated with poor prognosis. Ligand-receptor interaction analysis revealed symbiotic cross-talk between the stemlike tumor cells and E-MDSCs in GBM, whereby glioma stem cells produce chemokines attracting E-MDSCs, which in turn produce growth and survival factors for the tumor cells. Our large-scale single-cell analysis elucidated unique MDSC populations as key facilitators of GBM progression and mediators of tumor immunosuppression, suggesting that targeting these specific myeloid compartments, including their metabolic programs, may be a promising therapeutic intervention in this deadly cancer.

One-Sentence Summary

Aggressive glioblastoma harbors two unique myeloid populations capable of promoting stem-like properties of tumor cells and suppressing T cell function in the tumor microenvironment.

Engineered human cytokine/antibody fusion proteins expand regulatory T cells and confer autoimmune disease protection

Low-dose human interleukin-2 (hIL-2) treatment is used clinically to treat autoimmune disorders due to the cytokine's preferential expansion of immunosuppressive regulatory T cells (Tregs). However, off-target immune cell activation and short serum half-life limit the clinical potential of IL-2 treatment. Recent work showed that complexes comprising hIL-2 and the anti-hIL-2 antibody F5111 overcome these limitations by preferentially stimulating Tregs over immune effector cells. Although promising, therapeutic translation of this approach is complicated by the need to optimize dosing ratios and by the instability of the cytokine/antibody complex. We leverage structural insights to engineer a single-chain hIL-2/F5111 antibody fusion protein, termed F5111 immunocytokine (IC), which potently and selectively activates and expands Tregs. F5111 IC confers protection in mouse models of colitis and checkpoint inhibitor-induced diabetes mellitus. These results provide a roadmap for IC design and establish a Treg-biased immunotherapy that could be clinically translated for autoimmune disease treatment.

Abstract 595: Distinct tumor infiltrating Treg lineages are associated with response to anti-PD1 checkpoint blockade in NSCLC

Immune-checkpoint blockade (ICB) has proved a major success, especially in highly mutated tumors such as lung cancer. Nevertheless, not all patients respond to ICB. It is possible that regulatory T cells (Tregs) play a role in this lack of response by suppressing tumor-reactive cytotoxic T cells, however the specific mechanisms that lead to this suppression remain elusive. It is therefore necessary to understand the functional programming and suppressive nature of Treg subsets in the tumor microenvironment to define targetable molecules for future biomarker-driven therapeutics. In this study we performed single cell RNA-sequencing on T cells isolated from resected tissue and peripheral blood from 15 neoadjuvant nivolumab (anti-PD1)-treated and 10 untreated non-small cell lung cancer (NSCLC) patients. We identified and analyzed 71,251 CD4+ FoxP3+ Tregs. Refined clustering was performed, and we used pseudotime and differential gene analyses to understand the transcriptional relationship between clusters and patient groups. With our highly refined clustering approach, we identified 8 separate Treg clusters that reflect differing functionalities within the tumor microenvironment. We demonstrate distinct Treg subsets that diverge towards either an activated state, expressing members of the tumor necrosis factor receptor (TNFR) superfamily: OX40, 41BB, GITR, or a resting state. Patients who respond to ICI have a decreased activated Treg score and demonstrate RNA velocity trajectory from activated Tregs towards more in-active and resting populations. Untreated patients conversely show a high activated Treg score with RNA velocity demonstrating activated Tregs are a terminal differentiation state. We hypothesize that ICI treatment pushes Tregs away from an activated phenotype towards more quiescent and that the efficiency of this transition may predict response to ICI. We plan to stimulate receptors associated with non-response using TNFR agonist ligands and hypothesize that their induced signaling will result in transcriptional program changes altering the suppressive ability of Tregs. In addition, we show that Tregs who experience antigen within the tumor microenvironment are more suppressive than bystander Tregs that home to the tumor without antigen stimulation. Together, this study provides an in-depth look at the Treg-derived suppressive mechanisms governing their function in the TME of anti-PD-1-treated vs. untreated tumors. This in-depth analysis of tumor Tregs has identified specific targetable biomarkers which could be used to improve ICB response while mitigating off-target immune adverse events by specifically inhibiting a small subset of Tregs without disturbing systemic immune homeostasis.

Citation Format: Arbor G. Dykema, Jiajia Zhang, Boyang Zhang, Taibo Li, Justina X. Caushi, Laurene S. Cheung, Hongkai Ji, Zhicheng Ji, Kellie N. Smith, Drew M. Pardoll. Distinct tumor infiltrating Treg lineages are associated with response to anti-PD1 checkpoint blockade in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 595.

SARS-CoV-2 vaccination diversifies the CD4+ spike-reactive T cell repertoire in patients with prior SARS-CoV-2 infection

BACKGROUND

COVID-19 mRNA vaccines elicit strong T and B cell responses to the SARS-CoV-2 spike glycoprotein in both SARS-CoV-2 naïve and experienced patients. However, it is unknown whether the post-vaccine CD4+ T cell responses seen in patients with a history of COVID-19 are due to restimulation of T cell clonotypes that were first activated during natural infection or if they are the result of new clones activated by the vaccine.

METHODS

To address this question, we analyzed the SARS-CoV-2 spike glycoprotein-specific CD4+ T cell receptor repertoire before and after vaccination in 10 COVID-19 convalescent patients and 4 SARS-CoV-2 naïve healthy donor vaccine recipients. We used the viral Functional Expansion of Specific T cells (ViraFEST) assay to quantitatively identify specific SARS-CoV-2 and common cold coronavirus CD4+ T cell clonotypes post COVID-19 disease resolution and post mRNA SARS-CoV-2 vaccination.

FINDINGS

We found that while some preexisting T cell receptor clonotypes persisted, the post-vaccine repertoire consisted mainly of vaccine-induced clones and was largely distinct from the repertoire induced by natural infection. Vaccination-induced clones led to an overall maintenance of the total number of SARS-CoV-2 reactive clonotypes over time through expansion of novel clonotypes only stimulated through vaccination. Additionally, we demonstrated that the vaccine preferentially induces T cells that are only specific for SARS-CoV-2 antigens, rather than T cells that cross-recognize SARS-CoV-2/common cold coronaviruses.

INTERPRETATION

These data demonstrate that SARS-CoV-2 vaccination in patients with prior SARS-CoV-2 infection induces a new antigen-specific repertoire and sheds light on the differential immune responses induced by vaccination versus natural infection.

FUNDING

Bloomberg∼Kimmel Institute for Cancer Immunotherapy, The Johns Hopkins University, The Bill and Melinda Gates Foundation, NCI U54CA260492, NIH.

SARS-CoV-2-specific immune responses in boosted vaccine recipients with breakthrough infections during the Omicron variant surge

BackgroundBreakthrough SARS-CoV-2 infections in vaccinated individuals have been previously associated with suboptimal humoral immunity. However, less is known about breakthrough infections with the Omicron variant.MethodsWe analyzed SARS-CoV-2-specific antibody and cellular responses in healthy vaccine recipients who experienced breakthrough infections a median of 50 days after receiving a booster mRNA vaccine with an ACE2 binding inhibition assay and an ELISpot assay, respectively.ResultsWe found that high levels of antibodies inhibited vaccine strain spike protein binding to ACE2 but that lower levels inhibited Omicron variant spike protein binding to ACE2 in 4 boosted vaccine recipients prior to infection. The levels of antibodies that inhibited vaccine strain and Omicron spike protein binding after breakthrough in 18 boosted vaccine recipients were similar to levels seen in COVID-19-negative boosted vaccine recipients. In contrast, boosted vaccine recipients had significantly stronger T cell responses to both vaccine strain and Omicron variant spike proteins at the time of breakthrough.ConclusionOur data suggest that breakthrough infections with the Omicron variant can occur despite robust immune responses to the vaccine strain spike protein.FundingThis work was supported by the Johns Hopkins COVID-19 Vaccine-related Research Fund and by funds from the National Institute of Allergy and Infectious Disease intramural program as well as awards from the National Cancer Institute (U54CA260491) and the National Institutes of Allergy and Infectious Disease (K08AI156021 and U01AI138897).

CD4+ T-cells from COVID-19 mRNA vaccine recipients recognize a conserved epitope present in diverse coronaviruses

Recent studies have shown that vaccinated individuals harbor T cells that can cross-recognize SARS-CoV-2 and endemic human common cold coronaviruses. However, it is still unknown whether CD4⁺ T cells from vaccinated individuals recognize peptides from bat coronaviruses that may have the potential of causing future pandemics. In this study, we identified a SARS-CoV-2 spike protein epitope (S_815-827) that is conserved in coronaviruses from different genera and subgenera, including SARS-CoV, MERS-CoV, multiple bat coronaviruses, and a feline coronavirus. Our results showed that S_815-827 was recognized by 42% of vaccinated participants in our study who received the Pfizer-BioNTech (BNT162b2) or Moderna (mRNA-1273) COVID-19 vaccines. Using T cell expansion and T cell receptor sequencing assays, we demonstrated that S_815-827-reactive CD4⁺ T cells from the majority of responders cross-recognized homologous peptides from at least 6 other diverse coronaviruses. Our results support the hypothesis that the current mRNA vaccines elicit T cell responses that can cross-recognize bat coronaviruses and thus might induce some protection against potential zoonotic outbreaks. Furthermore, our data provide important insights that inform the development of T cell–based pan-coronavirus vaccine strategies.

Functional characterization of CD4+ T cell receptors crossreactive for SARS-CoV-2 and endemic coronaviruses

BACKGROUNDRecent studies have reported T cell immunity to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in unexposed donors, possibly due to crossrecognition by T cells specific for common cold coronaviruses (CCCs). True T cell crossreactivity, defined as the recognition by a single TCR of more than one distinct peptide-MHC ligand, has never been shown in the context of SARS-CoV-2.METHODSWe used the viral functional expansion of specific T cells (ViraFEST) platform to identify T cell responses crossreactive for the spike (S) glycoproteins of SARS-CoV-2 and CCCs at the T cell receptor (TCR) clonotype level in convalescent COVID-19 patients (CCPs) and SARS-CoV-2-unexposed donors. Confirmation of SARS-CoV-2/CCC crossreactivity and assessments of functional avidity were performed using a TCR cloning and transfection system.RESULTSMemory CD4+ T cell clonotypes that crossrecognized the S proteins of SARS-CoV-2 and at least one other CCC were detected in 65% of CCPs and unexposed donors. Several of these TCRs were shared among multiple donors. Crossreactive T cells demonstrated significantly impaired SARS-CoV-2-specific proliferation in vitro relative to monospecific CD4+ T cells, which was consistent with lower functional avidity of their TCRs for SARS-CoV-2 relative to CCC.CONCLUSIONSOur data confirm, for what we believe is the first time, the existence of unique memory CD4+ T cell clonotypes crossrecognizing SARS-CoV-2 and CCCs. The lower avidity of crossreactive TCRs for SARS-CoV-2 may be the result of antigenic imprinting, such that preexisting CCC-specific memory T cells have reduced expansive capacity upon SARS-CoV-2 infection. Further studies are needed to determine how these crossreactive T cell responses affect clinical outcomes in COVID-19 patients.FUNDINGNIH funding (U54CA260492, P30CA006973, P41EB028239, R01AI153349, R01AI145435-A1, R21AI149760, and U19A1088791) was provided by the National Institute of Allergy and Infectious Diseases, the National Cancer Institute, and the National Institute of Biomedical Imaging and Bioengineering. The Bloomberg~Kimmel Institute for Cancer Immunotherapy, The Johns Hopkins University Provost, and The Bill and Melinda Gates Foundation provided funding for this study.

Student Perceptions of M.D.-Ph.D. Programs: A Qualitative Identification of Barriers Facing Prospective M.D.-Ph.D. Applicants

Phenomenon: Despite a high degree of interest in research among matriculating M.D. students, very few apply to combined M.D.-Ph.D. training programs. Even fewer of those applicants are female, leading to a gender disparity among M.D.-Ph.D. trainees. We used a qualitative approach to understand why students choose not to apply or matriculate to M.D.-Ph.D. programs. Approach: We recruited recently matriculated medical students at a private research university with a self-reported interest in academic medicine and biomedical research to participate in focus groups, in which students discussed their career and life goals, general knowledge and sources of information for M.D.-Ph.D. programs, perceived benefits and downsides, and barriers to applying to such programs. Findings: Twenty-two students participated in focus groups. Participants desired careers combining clinical work, research, and teaching. Students had knowledge of the structure and goals of M.D.-Ph.D. training and received information about dual-degree programs from research mentors, the Internet, and peers. Tuition remission and increased grant access were cited as benefits of M.D.-Ph.D. programs, whereas duration, perceived excessive research training, and early commitment were downsides. Perceived competitiveness, misconceptions about training, a lack of M.D.-Ph.D. program-specific advising, discouragement from applying, and duration of training all served as barriers preventing students from pursuing dual-degree training. Insights: Through this qualitative study, we identified perceptions and misconceptions that recent medical school applicants have about M.D.-Ph.D. programs. These findings suggest targetable barriers to increase applications from interested students, such as improving awareness of programs, increased accessibility of advising and resources, and addressing concerns over training length, with the goal of improving training access for aspiring physician-scientists.