Effectiveness of CHIKV vaccine VLA1553 demonstrated by passive transfer of human sera.

Chikungunya virus (CHIKV) is a reemerging mosquito-borne alphavirus responsible for numerous outbreaks. Chikungunya can cause debilitating acute and chronic disease. Thus, the development of a safe and effective CHIKV vaccine is an urgent global health priority. This study evaluated the effectiveness of the live-attenuated CHIKV vaccine VLA1553 against WT CHIKV infection by using passive transfer of sera from vaccinated volunteers to nonhuman primates (NHP) subsequently exposed to WT CHIKV and established a serological surrogate of protection. We demonstrated that human VLA1553 sera transferred to NHPs conferred complete protection from CHIKV viremia and fever after challenge with homologous WT CHIKV. In addition, serum transfer protected animals from other CHIKV-associated clinical symptoms and from CHIKV persistence in tissue. Based on this passive transfer study, a 50% micro-plaque reduction neutralization test titer of ≥ 150 was determined as a surrogate of protection, which was supported by analysis of samples from a seroepidemiological study. In conclusion, considering the unfeasibility of an efficacy trial due to the unpredictability and explosive, rapidly moving nature of chikungunya outbreaks, the definition of a surrogate of protection for VLA1553 is an important step toward vaccine licensure to reduce the medical burden caused by chikungunya.

Novel conserved group A streptococcal proteins identified by the antigenome technology as vaccine candidates for a non-M protein-based vaccine.

Group A streptococci (GAS) can cause a wide variety of human infections ranging from asymptomatic colonization to life-threatening invasive diseases. Although antibiotic treatment is very effective, when left untreated, Streptococcus pyogenes infections can lead to poststreptococcal sequelae and severe disease causing significant morbidity and mortality worldwide. To aid the development of a non-M protein-based prophylactic vaccine for the prevention of group A streptococcal infections, we identified novel immunogenic proteins using genomic surface display libraries and human serum antibodies from donors exposed to or infected by S. pyogenes. Vaccine candidate antigens were further selected based on animal protection in murine lethal-sepsis models with intranasal or intravenous challenge with two different M serotype strains. The nine protective antigens identified are highly conserved; eight of them show more than 97% sequence identity in 13 published genomes as well as in approximately 50 clinical isolates tested. Since the functions of the selected vaccine candidates are largely unknown, we generated deletion mutants for three of the protective antigens and observed that deletion of the gene encoding Spy1536 drastically reduced binding of GAS cells to host extracellular matrix proteins, due to reduced surface expression of GAS proteins such as Spy0269 and M protein. The protective, highly conserved antigens identified in this study are promising candidates for the development of an M-type-independent, protein-based vaccine to prevent infection by S. pyogenes.

Chemokine degradation by the Group A streptococcal serine proteinase ScpC can be reconstituted in vitro and requires two separate domains.

Streptococcus pyogenes is one of the most common human pathogens and possesses diverse mechanisms to evade the human immune defence. One example of its immune evasion is the degradation of the chemokine IL (interleukin)-8 by ScpC, a serine proteinase that prevents the recruitment of neutrophils to an infection site. By applying the ANTIGENome technology and using human serum antibodies, we identified Spy0416, annotated as ScpC, as a prominent antigen that induces protective immune responses in animals. We demonstrate here for the first time that the recombinant form of Spy0416 is capable of IL-8 degradation in vitro in a concentration- and time-dependent manner. Mutations in the conserved amino acid residues of the catalytic triad of Spy0416 completely abolished in vitro activity. However, the isolated predicted proteinase domain does not exhibit IL-8-degrading activity, but is dependent on the presence of the C-terminal region of Spy0416. Binding to IL-8 is mainly mediated by the catalytic domain. However, the C-terminal region modulates substrate binding, indicating that the proteolytic activity is amenable to regulation via the non-catalytic regions. The specificity for human substrates is not restricted to IL-8, since we also detected in vitro protease activity for another CXC chemokine GRO-alpha (growth-related oncogene alpha), but not for NAP-2 (neutrophil-activating protein 2), SDF (stromal-cell-derived factor)-1alpha, PF-4 (platelet factor 4), I-TAC (interferon-gamma-inducible T-cell alpha-chemoattractant), IP-10 (interferon-gamma-inducible protein 10) and MCP-1 (monocyte chemoattractant protein 1). The degradation of two human CXC chemokines in vitro, the high sequence conservation, the immunogenicity of the protein in humans and the shown protection in animal studies suggest that Spy0416 is a promising vaccine candidate for the prevention of infections by S. pyogenes.

Single-shot live-attenuated chikungunya vaccine in healthy adults: a phase 1, randomised controlled trial.

BACKGROUND: Chikungunya disease, which results in incapacitating arthralgia, has been reported worldwide. We developed a live-attenuated chikungunya virus (CHIKV) vaccine candidate designed for active immunisation of the general population living in endemic regions, as well as serving as a prophylactic measure for travellers to endemic areas. METHODS: This single-blind, randomised, dose-escalation, phase 1 study investigated as primary outcome safety of a live-attenuated CHIKV vaccine candidate. At two professional clinical trial centres in Illinois and Alabama, USA, healthy volunteers aged 18-45 years were randomly assigned (1:1:2) to one of three escalating dose groups (low dose 3·2 × 103 per 0·1 mL; medium dose 3·2 × 104 per 1 mL; or high dose 3·2 × 105 50% tissue culture infection dose per 1 mL) and received a single-shot immunisation on day 0. Individuals in all groups were revaccinated with the highest dose on either month 6 or 12, and followed up for 28 days after revaccination. The safety analysis included all individuals who received the single vaccination; the immunogenicity analysis, which was a secondary outcome, included all individuals who completed the study without major protocol deviations (per-protocol population). The study is registered with ClinicalTrials.gov, NCT03382964, and is complete. FINDINGS: The study was done between March 5, 2018, and Jul 23, 2019, with 120 adults recruited and enrolled between March 5 and June 21, 2018, and assigned to receive a low (n=31), medium (n=30), or high (n=59) dose of the vaccine. The vaccine was safe in the high-dose group and well tolerated in the low-dose and medium-dose groups. Four (7%) of 59 vaccinees in the high-dose group reported any local reaction, and 11 (36%), 12 (40%), and 40 (68%) volunteers in the low-dose, medium-dose, and high-dose groups, respectively, reported any solicited systemic reaction. No vaccine-related serious adverse events were reported. Data up to month 12 after a single immunisation of the 120 healthy volunteers showed a good immunogenicity profile with 100% seroconversion rates achieved at day 14 (103 [100%] of 103) and sustained for 1 year across all dose groups. Mean peak antibody titres at day 28 ranged from 592·6 to 686·9 geometric mean titres from the low-dose to high-dose groups, respectively. A single vaccination was sufficient to induce sustaining high-titre neutralising antibodies, as shown by the absence of an anamnestic response after any revaccination ranging from 94% to 100% of participants. Following revaccination, vaccinees were protected from vaccine-induced viraemia. INTERPRETATION: A novel live-attenuated CHIKV vaccine was well tolerated and highly immunogenic in an adult population and could be an effective intervention for prophylaxis of chikungunya disease worldwide. FUNDING: Valneva, Vienna, Austria; Coalition for Epidemic Preparedness Innovation and EU Horizon 2020.

Mining the human autoantibody repertoire: isolation of potent IL17A-neutralizing monoclonal antibodies from a patient with thymoma.

Anti-cytokine autoantibodies have been widely reported to be present in human plasma, both in healthy subjects and in patients with underlying autoimmune conditions, such as autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) or thymic epithelial neoplasms. While often asymptomatic, they can cause or facilitate a wide range of diseases including opportunistic infections. The potential therapeutic value of specific neutralizing anti-cytokine autoantibodies has not been thoroughly investigated. Here we used mammalian cell display to isolate IL17A-specific antibodies from a thymoma patient with proven high-titer autoantibodies against the same. We identified 3 distinct clonotypes that efficiently neutralized IL17A in a cell-based in vitro assay. Their potencies were comparable to those of known neutralizing antibodies, including 2, AIN457 (secukinumab) and ixekizumab that are currently in clinical development for the treatment of various inflammatory disorders. These data clearly demonstrate that the human autoantibody repertoire can be mined for antibodies with high therapeutic potential for clinical development.