rAAV expressing recombinant antibody for emergency prevention and long-term prophylaxis of COVID-19

IntroductionNumerous agents for prophylaxis of SARS-CoV-2-induced diseases are currently registered for the clinical use. Formation of the immunity happens within several weeks following vaccine administration which is their key disadvantage. In contrast, drugs based on monoclonal antibodies, enable rapid passive immunization and therefore can be used for emergency pre- and post-exposure prophylaxis of COVID-19. However rapid elimination of antibody-based drugs from the circulation limits their usage for prolonged pre-exposure prophylaxis.MethodsIn current work we developed a recombinant adeno-associated viral vector (rAAV), expressing a SARS-CoV-2 spike receptor-binding domain (RBD)-specific antibody P2C5 fused with a human IgG1 Fc fragment (P2C5-Fc) using methods of molecular biotechnology and bioprocessing.Results and discussionsA P2C5-Fc antibody expressed by a proposed rAAV (rAAV-P2C5-Fc) was shown to circulate within more than 300 days in blood of transduced mice and protect animals from lethal SARS-CoV-2 virus (B.1.1.1 and Omicron BA.5 variants) lethal dose of 105 TCID50. In addition, rAAV-P2C5-Fc demonstrated 100% protective activity as emergency prevention and long-term prophylaxis, respectively. It was also demonstrated that high titers of neutralizing antibodies to the SARS-CoV-2 virus were detected in the blood serum of animals that received rAAV-P2C5-Fc for more than 10 months from the moment of administration.Our data therefore indicate applicability of an rAAV for passive immunization and induction of a rapid long-term protection against various SARS-CoV-2 variants

Safety and immunogenicity of rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine against SARS-CoV-2 in healthy adolescents: an open-label, non-randomized, multicenter, phase 1/2, dose-escalation study

To protect young individuals against SARS-CoV-2 infection, we conducted an open-label, prospective, non-randomised dose-escalation Phase 1/2 clinical trial to evaluate the immunogenicity and safety of the prime-boost “Sputnik V” vaccine administered at 1/10 and 1/5 doses to adolescents aged 12–17 years. The study began with the vaccination of the older cohort (15-to-17-year-old participants) with the lower (1/10) dose of vaccine and then expanded to the whole group (12-to-17-year-old participants). Next, 1/5 dose was used according to the same scheme. Both doses were well tolerated by all age groups. No serious or severe adverse events were detected. Most of the solicited adverse reactions were mild. No significant differences in total frequencies of adverse events were registered between low and high doses in age-pooled groups (69.6% versus 66.7%). In contrast, the 1/5 dose induced significantly higher humoral and T cell-mediated immune responses than the 1/10 dose. The 1/5 vaccine dose elicited higher antigen-binding (both S and RBD-specific) as well as virus-neutralising antibody titres at the maximum of response (day 42), also resulting in a statistically significant difference at a distanced timepoint (day 180) compared to the 1/10 vaccine dose. Higher dose resulted in increased cross-neutralization of Delta and Omicron variants.;Clinical Trial RegistrationClinicalTrials.gov, NCT04954092, LP-007632

Stimulation of Dectin-1 and Dectin-2 during Parenteral Immunization, but Not Mincle, Induces Secretory IgA in Intestinal Mucosa

Induction of a robust and long-lived mucosal immune response during vaccination is critical to achieve protection against numerous pathogens. However, traditional injected vaccines are generally poor inducers of mucosal immunity. One of the effective strategies to improve vaccine efficacy is incorporation of adjuvant molecules that enhance and polarize adaptive immune reactions. Effects of Syk-coupled lectin receptor agonists as adjuvants to induce mucosal immune reactions during parenteral immunization are not fully studied. We now report that the agonists trehalose-6,6-dibehenate (TDB), curdlan, and furfurman, which stimulate Dectin-1, Dectin-2, and Mincle, respectively, activate transcription factors (NF-κB, NFAT, and AP-1) to various extents in murine RAW 264.7 macrophages, even though similar pathways are activated. The agonists also elicit differential expression of maturation markers in bone marrow-derived dendritic cells, as well as differential cytokine secretion from these cells and from splenic mononuclear cells. In vivo assays also show that agonists of Dectin-1 and Dectin-2, but not Mincle, induce heavy IgA secretion in intestinal mucosa even when delivered parenterally. Strikingly, this effect appears to be formulation-independent. Collectively, the data suggest that adjuvants based on Dectin-1 and Dectin-2 agonists may significantly improve the efficacy of parenteral vaccines by inducing robust local immune reactions in intestinal mucosa

Chlamydial Type III Secretion System Needle Protein Induces Protective Immunity against Chlamydia muridarum Intravaginal Infection

Chlamydia trachomatis imposes serious health problems and causes infertility. Because of asymptomatic onset, it often escapes antibiotic treatment. Therefore, vaccines offer a better option for the prevention of unwanted inflammatory sequelae. The existence of serologically distinct serovars of C. trachomatis suggests that a vaccine will need to provide protection against multiple serovars. Chlamydia spp. use a highly conserved type III secretion system (T3SS) composed of structural and effector proteins which is an essential virulence factor. In this study, we expressed the T3SS needle protein of Chlamydia muridarum, TC_0037, an ortholog of C. trachomatis CdsF, in a replication-defective adenoviral vector (AdTC_0037) and evaluated its protective efficacy in an intravaginal Chlamydia muridarum model. For better immune responses, we employed a heterologous prime-boost immunization protocol in which mice were intranasally primed with AdTC_0037 and subcutaneously boosted with recombinant TC_0037 and Toll-like receptor 4 agonist monophosphoryl lipid A mixed in a squalene nanoscale emulsion. We found that immunization with TC_0037 antigen induced specific humoral and T cell responses, decreased Chlamydia loads in the genital tract, and abrogated pathology of upper genital organs. Together, our results suggest that TC_0037, a highly conserved chlamydial T3SS protein, is a good candidate for inclusion in a Chlamydia vaccine

Chlamydial Type III Secretion System Needle Protein Induces Protective Immunity against Chlamydia muridarum Intravaginal Infection

Chlamydia trachomatis imposes serious health problems and causes infertility. Because of asymptomatic onset, it often escapes antibiotic treatment. Therefore, vaccines offer a better option for the prevention of unwanted inflammatory sequelae. The existence of serologically distinct serovars of C. trachomatis suggests that a vaccine will need to provide protection against multiple serovars. Chlamydia spp. use a highly conserved type III secretion system (T3SS) composed of structural and effector proteins which is an essential virulence factor. In this study, we expressed the T3SS needle protein of Chlamydia muridarum, TC_0037, an ortholog of C. trachomatis CdsF, in a replication-defective adenoviral vector (AdTC_0037) and evaluated its protective efficacy in an intravaginal Chlamydia muridarum model. For better immune responses, we employed a heterologous prime-boost immunization protocol in which mice were intranasally primed with AdTC_0037 and subcutaneously boosted with recombinant TC_0037 and Toll-like receptor 4 agonist monophosphoryl lipid A mixed in a squalene nanoscale emulsion. We found that immunization with TC_0037 antigen induced specific humoral and T cell responses, decreased Chlamydia loads in the genital tract, and abrogated pathology of upper genital organs. Together, our results suggest that TC_0037, a highly conserved chlamydial T3SS protein, is a good candidate for inclusion in a Chlamydia vaccine

Camelid VHHs Fused to Human Fc Fragments Provide Long Term Protection Against Botulinum Neurotoxin A in Mice

The bacterium Clostridium botulinum is the causative agent of botulism—a severe intoxication caused by botulinum neurotoxin (BoNT) and characterized by damage to the nervous system. In an effort to develop novel C. botulinum immunotherapeutics, camelid single-domain antibodies (sdAbs, VHHs, or nanobodies) could be used due to their unique structure and characteristics. In this study, VHHs were produced using phage display technology. A total of 15 different monoclonal VHHs were selected based on their comlementarity-determining region 3 (CDR3) sequences. Different toxin lethal dose (LD50) challenges with each selected phage clone were conducted in vivo to check their neutralizing potency. We demonstrated that modification of neutralizing VHHs with a human immunoglobulin G (IgG)1 Fc (fragment crystallizable) fragment (fusionbody, VHH-Fc) significantly increased the circulation time in the blood (up to 14 days). At the same time, VHH-Fc showed the protective activity 1000 times higher than monomeric form when challenged with 5 LD50. Moreover, VHH-Fcs remained protective even 14 days after antibody administration. These results indicate that this VHH-Fc could be used as an effective long term antitoxin protection against botulinum type A

Genetic Passive Immunization with Adenoviral Vector Expressing Chimeric Nanobody-Fc Molecules as Therapy for Genital Infection Caused by Mycoplasma hominis.

Developing pathogen-specific recombinant antibody fragments (especially nanobodies) is a very promising strategy for the treatment of infectious disease. Nanobodies have great potential for gene therapy application due to their single-gene nature. Historically, Mycoplasma hominis has not been considered pathogenic bacteria due to the lack of acute infection and partially due to multiple studies demonstrating high frequency of isolation of M. hominis samples from asymptomatic patients. However, recent studies on the role of latent M. hominis infection in oncologic transformation, especially prostate cancer, and reports that M. hominis infects Trichomonas and confers antibiotic resistance to Trichomonas, have generated new interest in this field. In the present study we have generated specific nanobody against M. hominis (aMh), for which the identified target is the ABC-transporter substrate-binding protein. aMh exhibits specific antibacterial action against M. hominis. In an attempt to improve the therapeutic properties, we have developed the adenoviral vector-based gene therapy approach for passive immunization with nanobodies against M. hominis. For better penetration into the mucous layer of the genital tract, we fused aMh with the Fc-fragment of IgG. Application of this comprehensive approach with a single systemic administration of recombinant adenovirus expressing aMh-Fc demonstrated both prophylactic and therapeutic effects in a mouse model of genital M. hominis infection

Identification of HI-Like Loop in CELO Adenovirus Fiber for Incorporation of Receptor Binding Motifs▿

Vectors based on the chicken embryo lethal orphan (CELO) avian adenovirus (Ad) have two attractive properties for gene transfer applications: resistance to preformed immune responses to human Ads and the ability to grow in chicken embryos, allowing low-cost production of recombinant viruses. However, a major limitation of this technology is that CELO vectors demonstrate decreased efficiency of gene transfer into cells expressing low levels of the coxsackie-Ad receptor (CAR). In order to improve the efficacy of gene transfer into CAR-deficient cells, we modified viral tropism via genetic alteration of the CELO fiber 1 protein. The αv integrin-binding motif (RGD) was incorporated at two different sites of the fiber 1 knob domain, within an HI-like loop that we identified and at the C terminus. Recombinant fiber-modified CELO viruses were constructed containing secreted alkaline phosphatase (SEAP) and enhanced green fluorescent protein genes as reporter genes. Our data show that insertion of the RGD motif within the HI-like loop of the fiber resulted in significant enhancement of gene transfer into CAR-negative and CAR-deficient cells. In contrast, CELO vectors containing the RGD motif at the fiber 1 C terminus showed reduced transduction of all cell lines. CELO viruses modified with RGD at the HI-like loop transduced the SEAP reporter gene into rabbit mammary gland cells in vivo with an efficiency significantly greater than that of unmodified CELO vector and similar to that of Ad type 5 vector. These results illustrate the potential for efficient CELO-mediated gene transfer into a broad range of cell types through modification of the identified HI-like loop of the fiber 1 protein

Powerful Complex Immunoadjuvant Based on Synergistic Effect of Combined TLR4 and NOD2 Activation Significantly Enhances Magnitude of Humoral and Cellular Adaptive Immune Responses

<div><p>Binding of pattern recognition receptors (PRRs) by pathogen-associated molecular patterns (PAMPs) activates innate immune responses and contributes to development of adaptive immunity. Simultaneous stimulation of different types of PRRs can have synergistic immunostimulatory effects resulting in enhanced production of molecules that mediate innate immunity such as inflammatory cytokines, antimicrobial peptides, etc. Here, we evaluated the impact of combined stimulation of PRRs from different families on adaptive immunity by generating alum-based vaccine formulations with ovalbumin as a model antigen and the Toll-like receptor 4 (TLR4) agonist MPLA and the Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) agonist MDP adsorbed individually or together on the alum-ovalbumin particles. Multiple <i>in vitro</i> and <i>in vivo</i> readouts of immune system activation all showed that while individual PRR agonists increased the immunogenicity of vaccines compared to alum alone, the combination of both PRR agonists was significantly more effective. Combined stimulation of TLR4 and NOD2 results in a stronger and broader transcriptional response in THP-1 cells compared to individual PRR stimulation. Immunostimulatory composition containing both PRR agonists (MPLA and MDP) in the context of the alum-based ovalbumin vaccine also enhanced uptake of vaccine particles by bone marrow derived dendritic cells (BMDCs) and promoted maturation (up-regulation of expression of CD80, CD86, MHCII) and activation (production of cytokines) of BMDCs. Finally, immunization of mice with vaccine particles containing both PRR agonists resulted in enhanced cellular immunity as indicated by increased proliferation and activation (IFN-γ production) of splenic CD4+ and CD8+ T cells following <i>in vitro</i> restimulation with ovalbumin and enhanced humoral immunity as indicated by higher titers of ovalbumin-specific IgG antibodies. These results indicate that combined stimulation of TLR4 and NOD2 receptors dramatically enhances activation of both the humoral and cellular branches of adaptive immunity and suggests that inclusion of agonists of these receptors in standard alum-based adjuvants could be used to improve the effectiveness of vaccination.</p></div