Long-term efficacy of the peptide-based COVID-19 T cell activator CoVac-1 in healthy adults (preprint)

Background: T cell immunity is key for the control of viral infections including SARS-CoV-2, in particular with regard to immune memory and protection against arising genetic variants. Method: We recently evaluated a peptide-based SARS-CoV-2 T cell activator termed CoVac-1 in a first-in-human clinical trial and observed a favorable safety profile and induction of poly-specific T cell responses until month 3. Here, we report on long-term safety and efficacy data of CoVac-1 in healthy adults until month 12. Findings: CoVac-1 is well tolerated without long-term immune-related side effects and induces long-lasting anti-viral T cell responses in 100% of study participants. Potent expandability of CD4+ and CD8+ T cells targeting multiple different CoVac-1 T cell epitopes was observed 6 and 12 months after one single dose of CoVac-1. T cell responses were associated with the severity and the number of local adverse events at injection site. Beyond induction of T cell immunity, 89% of study participants developed CoVac-1-specific IgG antibody titers which associated with the intensity of the T cell response, indicating that CoVac-1-specific CD4+ T cells support the induction of B cell responses. Vaccination with approved COVID-19 vaccines boosted CoVac-1-specific T cell responses. Overall, a low SARS-CoV-2 infection rate was observed in the study population (8.3% of participants until month 12). Interpretation: Together, a single application of CoVac-1 elicits long-lived and broad SARS-CoV-2-specific T cell immunity, which further supports the current evaluation of our T cell activator in patients with congenital or acquired B cell defects (NCT04954469). Funding: This trial is funded by the Ministry of Science, Research and the Arts Baden-Wuerttemberg., Germany

Phase I/II trial of a peptide-based COVID-19 T-cell activator in patients with B-cell deficiency (preprint)

T-cell immunity is central for the control of COVID-19, in particular in patients incapable to mount a humoral immune response. We previously reported on the favorable safety profile and efficacy in terms of induction of SARS-CoV-2-specific T-cell responses by CoVac-1, a peptide-based T-cell activator, composed of SARS-CoV-2 T-cell epitopes derived from various viral proteins, combined with the toll-like receptor 1/2 agonist XS151. We conducted a Phase I/II open-label trial recruiting 54 patients with congenital or acquired B-cell deficiency who received one single subcutaneous dose of CoVac-1. Immunogenicity until day 28 in terms of CoVac-1-induced T-cell responses was the primary endpoint; safety until day 56 was assessed as secondary endpoint. Neither serious nor grade 4 CoVac-1-related adverse events were observed. The expected local granuloma formation was observed in 94% of study subjects, whereas systemic reactogenicity was mostly mild or absent. SARS-CoV-2-specific Tcell responses were induced in 86% of the patients and directed to multiple CoVac-1 peptides, not affected by any current Omicron variants and mediated by multifunctional T-helper 1 CD4+ T cells. CoVac-1-induced T-cell responses exceeded spike-specific T-cell responses after vaccination with mRNA vaccines in B-cell deficient patients and also that of immunocompetent COVID-19 convalescents with and without seroconversion. CoVac-1 induces broad and potent T-cell responses in patients with Bcell/antibody deficiency independently of current variants of concern, with a favorable safety profile. Our data warrant advancement to a pivotal Phase II/III safety and efficacy evaluation.

Phase I Trial of a Multi-Peptide COVID-19 Vaccine for the Induction of SARS-CoV-2 T-Cell Immunity (preprint)

T-cell immunity is central for the control of viral infections. CoVac-1 is a peptide-based vaccine candidate, composed of SARS-CoV-2 T-cell epitopes derived from various viral proteins, combined with the toll-like receptor 1/2 agonist XS15 emulsified in Montanide TM ISA51 VG, aiming to induce superior SARS-CoV-2 T-cell immunity to combat COVID-19. We conducted a Phase I open-label trial, including 36 participants aged 18 to 80 years, who received one single subcutaneous CoVAC-1 vaccination. The primary endpoint was safety analyzed until day 56. Immunogenicity in terms of CoVac-1-induced T-cell response was analyzed as main secondary endpoint until day 28. No serious adverse events and no grade 4 adverse events were observed. Expected local granuloma formation was observed in all study subjects, while systemic reactogenicity was absent or mild. SARS-CoV-2-specific T-cell responses targeting multiple vaccine peptides were induced in all study participants, mediated by multifunctional T-helper 1 CD4 + and CD8 + T cells. CoVac-1-induced interferon-γ T-cell responses by far surpassed those detected in COVID-19 convalescents and were unaffected by current SARS-CoV-2 variants of concern (VOC). Together, CoVac-1 showed a favorable safety profile and induced broad, potent, and VOC-independent T-cell responses, supporting the presently ongoing evaluation in a Phase II trial for patients with B-cell/antibody deficiency. Funded by the Ministry of Science, Research and the Arts Baden-Württemberg, Germany; ClinicalTrials.gov number, NCT04546841.

Pre-existing and post-COVID-19 immune responses to SARS-CoV-2 in cancer patients (preprint)

Cancer patients, in particular patients with hematological malignancies, are at increased risk for critical illness upon COVID-19. We here assessed antibody as well as CD4+ and CD8+ T cell responses in unexposed and SARS-CoV-2-infected cancer patients to characterize SARS-CoV‑2 immunity and to identify immunological parameters contributing to COVID-19 outcome. Unexposed patients with hematological malignancies presented with reduced prevalence of pre-existing SARS-CoV-2 cross-reactive CD4+ T cell responses and signs of T cell exhaustion when compared to solid tumor patients and healthy volunteers. Whereas SARS-CoV-2 antibody responses did not differ between COVID-19 cancer patients and healthy volunteers, intensity, expandability, and diversity of SARS-CoV-2 T cell responses were profoundly reduced in cancer patients, and the latter associated with a severe course of COVID-19. This identifies impaired SARS-CoV-2 T cell immunity as determinant for dismal outcome of COVID-19 in cancer patients.

Differential kinetics of T cell and antibody responses delineate dominant T cell epitopes in long-term immunity after COVID-19 (preprint)

Long-term immunity to SARS-CoV-2 is crucial for the development of herd immunity and the aim of vaccination approaches. Reports on rapidly decreasing antibody titers question the efficacy of humoral immunity. The relevance of T cell memory after COVID-19 is yet unclear. Longitudinal analysis of SARS-CoV-2 immunity in convalescents up to six months post-infection revealed decreasing and stable spike and nucleocapsid antibody responses, respectively. In contrast, T cell responses remained robust and even increased in frequency and intensity. Single epitope mapping of T cell diversity over time identified ORF-independent, dominant T cell epitopes mediating long-term SARS-CoV-2 T cell responses and may be fundamental for vaccine design.

Differential Kinetics of T Cell and Antibody Responses Delineate Dominant T Cell Epitopes in Long-Term Immunity after COVID-19 (preprint)

Long-term immunity to SARS-CoV-2 is crucial for the development of herd immunity and the aim of vaccination approaches. Reports on rapidly decreasing antibody titers question the efficacy of humoral immunity. The relevance of T cell memory after COVID-19 is yet unclear. Longitudinal analysis of SARS-CoV-2 immunity in convalescents up to six months post-infection revealed decreasing and stable spike and nucleocapsid antibody responses, respectively. In contrast, T cell responses remained robust and even increased in frequency and intensity. Single epitope mapping of T cell diversity over time identified ORF-independent, dominant T cell epitopes mediating long-term SARS-CoV-2 T cell responses and may be fundamental for vaccine design.Funding: This work was supported by the Bundesministerium für Bildung und Forschung (BMBF, FKZ:01KI20130; J.W.), the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, Grant WA 4608/1-2; J.W.), the Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy (Grant EXC2180-390900677; S.S., H.-G.R., H.R.S., J.W.), the German Cancer Consortium (DKTK; S.S., H.-G.R., H.R.S.), the Wilhelm Sander Stiftung (Grant 2016.177.2; J.W.), the José Carreras Leukämie-Stiftung (Grant DJCLS 05 R/2017; J.W.) and the Fortüne Program of the University of Tübingen (Fortüne number 2451-0-0 and 2581-0-0; J.W.). Conflict of Interest: H.-G.R. is shareholder of Immatics Biotechnologies GmbH and Curevac AG. A.N., T.B., H.-G.R., and J.S.W. hold patents on peptides described in this manuscript secured under the numbers 20 169 047.6 and 20 190 070.1. The other authors declare no competing interests.Ethical Approval: The study was approved by and performed according to the guidelines of the local ethics committees (179/2020/BO2).

Integrin activation enables simultaneous and sensitive detection of functional virus-specific CD4+ and CD8+ T cells (preprint)

We have previously shown that beta2-integrin conformational change is a very early activation marker that can be detected with fluorescent multimers of its ligand ICAM-1 for a rapid assessment of antigen-specific CD8+ T cells. Here, we describe a modified protocol of this assay for sensitive detection of functional antigen-specific CD4+ T cells using a monoclonal antibody (clone m24) specific for the open, high affinity conformation of the beta2-integrin. Kinetics of beta2-integrin activation were different on CD4+ and CD8+ T cells (several hours vs. few minutes, respectively), however, m24 antibody readily stained both cell types 4-6 hours after antigen stimulation. With this protocol, we were able to monitor CD4+ and CD8+ virus-specific T cells specific for CMV, EBV, HBV, and SARS-CoV-2 in whole blood or cryopreserved PBMCs of infected or vaccinated individuals. By costaining with m24 and CD154 antibodies, we assessed extremely low frequencies of polyfunctional CD4+ T cell responses to SARS-CoV-2 derived peptides. Our novel assay thus allows very sensitive and simultaneous screening of both CD4+ and CD8+ T cell reactivities with versatile applicability in clinical and vaccination studies, and for epitope discovery.

Going beyond clinical routine in SARS-CoV-2 antibody testing - A multiplex corona virus antibody test for the evaluation of cross-reactivity to endemic coronavirus antigens (preprint)

Given the importance of the humoral immune response to SARS-CoV-2 as a global benchmark for immunity, a detailed analysis is needed to (i) monitor seroconversion in the general population, (ii) understand manifestation and progression of the disease, and (iii) predict the outcome of vaccine development. Currently available serological assays utilize single analyte technologies such as ELISA to measure antibodies against SARS-CoV-2 antigens including spike (S) or nucleocapsid (N) protein. To measure individual antibody (IgG and IgA) responses against SARS-CoV-2 and the endemic human coronaviruses (hCoVs) NL63, 229E, OC43, and HKU1, we developed a multiplexed immunoassay (CoVi-plex), for which we included S and N proteins of these coronaviruses in an expanded antigen panel. Compared to commercial in vitro diagnostic (IVD) tests our CoVi-plex achieved the highest sensitivity and specificity when analyzing 310 SARS-CoV-2 infected and 866 uninfected individuals. Simultaneously we see high IgG responses against hCoVs throughout all samples, whereas no consistent cross reactive IgG response patterns can be defined. In summary, our CoVi-plex is highly suited to monitor vaccination studies and will facilitate epidemiologic screenings for the humoral immunity toward pandemic as well as endemic coronaviruses.

SARS-CoV-2 T-cell epitopes define heterologous and COVID-19-induced T-cell recognition (preprint)

The SARS-CoV-2 pandemic calls for the rapid development of diagnostic, preventive, and therapeutic approaches. CD4+ and CD8+ T cell-mediated immunity is central for control of and protection from viral infections[1-3]. A prerequisite to characterize T-cell immunity, but also for the development of vaccines and immunotherapies, is the identification of the exact viral T-cell epitopes presented on human leukocyte antigens (HLA)[2-8]. This is the first work identifying and characterizing SARS-CoV-2-specific and cross-reactive HLA class I and HLA-DR T-cell epitopes in SARS-CoV-2 convalescents (n = 180) as well as unexposed individuals (n = 185) and confirming their relevance for immunity and COVID-19 disease course. SARS-CoV-2-specific T-cell epitopes enabled detection of post-infectious T-cell immunity, even in seronegative convalescents. Cross-reactive SARS-CoV-2 T-cell epitopes revealed preexisting T-cell responses in 81% of unexposed individuals, and validation of similarity to common cold human coronaviruses provided a functional basis for postulated heterologous immunity[9] in SARS-CoV-2 infection[10,11]. Intensity of T-cell responses and recognition rate of T-cell epitopes was significantly higher in the convalescent donors compared to unexposed individuals, suggesting that not only expansion, but also diversity spread of SARS-CoV-2 T-cell responses occur upon active infection. Whereas anti-SARS-CoV-2 antibody levels were associated with severity of symptoms in our SARS-CoV-2 donors, intensity of T-cell responses did not negatively affect COVID-19 severity. Rather, diversity of SARS-CoV-2 T-cell responses was increased in case of mild symptoms of COVID-19, providing evidence that development of immunity requires recognition of multiple SARS-CoV-2 epitopes. Together, the specific and cross-reactive SARS-CoV-2 T-cell epitopes identified in this work enable the identification of heterologous and post-infectious T-cell immunity and facilitate the development of diagnostic, preventive, and therapeutic measures for COVID-19.

Designing a therapeutic SARS-CoV-2 T-cell-inducing vaccine for high-risk patient groups (preprint)

Here, we describe the preliminary results of an experimental vaccination of a self-experimenting healthy volunteer with eight SARS-CoV-2-derived peptides: five predicted to bind to HLA class I molecules (CD8 peptides) and three predicted to bind to HLA-DR molecules (CD4 peptides). The vaccine formulation also included one long and one short CMV-pp65-derived peptide that had previously been administered to the same individual and could thus act as positive controls. It further contained the new adjuvant XS15 and was administered as an emulsion in Montanide as a single subcutaneous (s.c.) injection. Peripheral blood mononuclear cells (PBMCs) isolated from blood drawn on day 36 before vaccination and day 19 after vaccination were assessed using an ex vivo Interferon-γ ELISpot assay. We detected strong vaccine-induced T-cell responses against all four CD4 peptides and against the recall CMV CD8 epitope, but found no immune responses against the five predicted SARS-CoV-2 CD8 peptides. Antibody reactivity against all the SARS-CoV-2 CD4 peptides, as detected using ELISA, was negative or marginal. We interpret these results in terms of the prospects of a therapeutic vaccine to be applied in symptomatic COVID-19 patients. An advantage of this approach is the possibility to assess efficacy or failure within a short time after vaccination.