In vitro evaluation of the binding activity of novel mouse IgG1 opsonic monoclonal antibodies to Mycobacterium tuberculosis and other selected mycobacterial species

Antimicrobial resistance alongside other challenges in tuberculosis (TB) therapeutics have stirred renewed interest in host-directed interventions, including the role of antibodies as adjunct therapeutic agents. This study assessed the binding efficacy of two novel IgG1 opsonic monoclonal antibodies (MABs; GG9 & JG7) at 5, 10, and 25 µg/mL to live cultures of Mycobacterium tuberculosis, M. avium, M. bovis, M. fortuitum, M. intracellulare, and M. smegmatis American Type Culture Collection laboratory reference strains, as well as clinical susceptible, multi-drug resistant, and extensively drug resistant M. tuberculosis strains using indirect enzyme-linked immunosorbent assays. These three MAB concentrations were selected from a range of concentrations used in previous optimization (binding and functional) assays. Both MABs bound to all mycobacterial species and sub-types tested, albeit to varying degrees. Statistically significant differences in MAB binding activity were observed when comparing the highest and lowest MAB concentrations (p < 0.05) for both MABs GG9 and JG7, irrespective of the M. tuberculosis resistance profile. Binding affinity increased with an increase in MAB concentration, and optimal binding was observed at 25 µg/mL. JG7 showed better binding activity than GG9. Both MABs also bound to five MOTT species, albeit at varied levels. This non-selective binding to different mycobacterial species suggests a potential role for GG9 and JG7 as adjunctive agents in anti-TB chemotherapy with the aim to enhance bacterial killing.

Unconjugated Multi-Epitope Peptides Adjuvanted with ALFQ Induce Durable and Broadly Reactive Antibodies to Human and Avian Influenza Viruses

An unconjugated composite peptide vaccine targeting multiple conserved influenza epitopes from hemagglutinin, neuraminidase, and matrix protein and formulated with a safe and highly potent adjuvant, Army Liposome formulation (ALFQ), generated broad and durable immune responses in outbred mice. The antibodies recognized specific epitopes in influenza peptides and several human, avian, and swine influenza viruses. Comparable antibody responses to influenza viruses were observed with intramuscular and intradermal routes of vaccine administration. The peptide vaccine induced cross-reactive antibodies that recognized influenza virus subtypes A/H1N1, A/H3N2, A/H5N1, B/Victoria, and B/Yamagata. In addition, immune sera neutralized seasonal and pandemic influenza strains (Group 1 and Group 2). This composite multi-epitope peptide vaccine, formulated with ALFQ and administered via intramuscular and intradermal routes, provides a high-performance supra-seasonal vaccine that would be cost-effective and easily scalable, thus moving us closer to a viable strategy for a universal influenza vaccine and pandemic preparedness.

2318. A Composite Peptide Vaccine Comprised of Conserved SARS-CoV-2 and Influenza Epitopes Generated Antisera Reponses to Both Coronavirus and Influenza

Background

While influenza and SARS-CoV-2 virus can be severe, co-infection with these viruses has the potential for worsening the clinical outcome. The combined infection of influenza A virus (IAV) and SARS-CoV-2 in animal models has also shown elevated SARS-CoV-2 viral load and pneumonia. Co-vaccination may provide a useful option in prevention of combined infection. In this study, a composite peptide vaccine comprised of highly conserved influenza neuraminidase (NA) and matrix protein (M2e) epitopes, in combination with either conserved spike protein (SP) or RNA polymerase (POL) epitopes of SARS-CoV-2 generated robust immune responses to both coronavirus and influenza virus.

Methods

Mice were immunized with 20µg of Coronavirus Pep02 (CorPep02, comprised of POL) or Coronavirus Pep05 (CorPep05, comprised of POL and NA+M2e) or Coronavirus Pep11 (CorPep11, comprised of SP and NA+M2e), formulated with AddaVax™. Serum antibody titers to both coronavirus and influenza peptides, and whole viruses were analyzed using ELISA. Antisera neutralizing activity against IAV was determined using microneutralization assay (MNA).

Results

CorPep05 immunization generated enhanced IgG1 and IgG2b antisera responses to the immunogens compared to CorPep02, starting at Day-21. Immunization with CorPep05 or CorPep11 induced strong IgG1 and IgG2b immune responses to the composite coronavirus peptides, influenza NA and M2e peptides, coronavirus POL and SP peptides. Antisera from CorPep05 and CorPep11 groups bound to both viruses (IAV and human coronavirus NL-63 (HCoV NL-63)) and demonstrated neutralizing activity against IAV, with titers >5000.

Conclusion

A composite peptide vaccine comprised of both influenza (NA+M2e) and coronavirus (POL) epitopes generated enhanced immune responses in comparison to peptide containing only POL. Th1 and Th2 immune responses to coronavirus POL and SP were observed. Serum neutralizing activity was demonstrated against IAV. Studies are underway to examine neutralizing antibodies against HCoV NL-63 and multiple variants of SARS-CoV-2. Highly conserved epitopes in these composite peptide vaccines may provide an important strategy to prevent infections with IAV or SARS-CoV-2 and mitigate the threat of co-infection.

Disclosures

All Authors: No reported disclosures.

1706. IgM Monoclonal Antibodies Targeting Peptidoglycan May Provide Therapeutic Strategies against Antimicrobial Resistant Bacteria

Background

Antimicrobial resistance (AMR) poses a substantial global threat to human health and development. In addition to death and disability, the cost of AMR to the global economy is significant. Prolonged illness results in longer hospital stays and the need for more expensive medicines and financial challenges for those impacted. Therapeutics such as monoclonal antibodies (mAbs) may offer prevention and control measures against microbial infections without the use of antibiotics. In this study, we developed human antibodies (serum and mAbs) against components of staphylococcus aureus (SA) and Mycobacterium tuberculosis (MTB) and evaluated their capabilities.

Methods

Humanized DRAGA mice were immunized with 20μg of a combination vaccine comprised of Ultrapure peptidoglycan (PGN, derived from SA) and TB Pep01 peptide (targeting MTB HSP16.3), formulated with AddaVax™ adjuvant. Serum antibody responses to PGN, TB Pep01, and various whole bacteria were analyzed using ELISA. Mice with high antisera titers was selected for hybridoma production. Hybridomas were screened for binding to PGN, TB Pep01, and whole bacteria using ELISA and high producing clones were selected for monoclonal antibody development.

Results

Early and enhanced serum IgM responses to PGN were observed by Day-21, while IgG responses to PGN were detected at Day-35. Antisera binding to TB Pep01 was demonstrated, albeit lower than PGN. In addition, antisera recognition of whole bacteria was shown. Hybridoma clones (IgM) targeting PGN were identified for monoclonal antibody production.

Conclusion

Hybridomas developed in humanized DRAGA mice immunized with PGN and TBPep01 bound to the immunogens and showed broad recognition of various microbes. Ongoing studies to evaluate mAb functional activity against various microbes to include mycobacteria and staphylococci are in progress. IgM mAbs that recognize and whole bacteria, and opsonize and kill multiple bacterial strains, may provide an effective antimicrobial strategy for treatment of drug resistant bacterial infections.

Disclosures

All Authors: No reported disclosures.

Conserved Influenza Hemagglutinin, Neuraminidase and Matrix Peptides Adjuvanted with ALFQ Induce Broadly Neutralizing Antibodies

A universal influenza candidate vaccine that targets multiple conserved influenza virus epitopes from hemagglutinin (HA), neuraminidase (NA) and matrix (M2e) proteins was combined with the potent Army liposomal adjuvant (ALFQ) to promote induction of broad immunity to seasonal and pandemic influenza strains. The unconjugated and CRM-conjugated composite peptides formulated with ALFQ were highly immunogenic and induced both humoral and cellular immune responses in mice. Broadly reactive serum antibodies were induced across various IgG isotypes. Mice immunized with the unconjugated composite peptide developed antibody responses earlier than mice immunized with conjugated peptides, and the IgG antibodies were broadly reactive and neutralizing across Groups 1 and 2 influenza viruses. Multi-epitope unconjugated influenza composite peptides formulated with ALFQ provide a novel strategy for the development of a universal influenza vaccine. These synthetic peptide vaccines avoid the pitfalls of egg-produced influenza vaccines and production can be scaled up rapidly and economically.

2752. Peptide Vaccines Utilizing Conserved Hemagglutinin, Neuraminidase, and Matrix Ectodomain Influenza Epitopes Demonstrate Functional Activity Against Group 1 and 2 Influenza Strains

Background

Globally, prevention and control of seasonal influenza has faced many challenges in the selection of a vaccine composition that antigenically matches circulating viruses. A universal influenza vaccine approach that targets small conserved influenza virus epitopes/peptides such as the extracellular domain of Matrix 2 (M2e) and induces broadly reactive antibodies may be helpful for both seasonal influenza outbreaks and pandemics. Here we report the ability of two composite peptide vaccines, individually and in combination, to induce broadly reactive antibodies that have binding and functional activity across several contemporary influenza strains in Group 1 and 2.

Methods

Mice were immunized with peptide composite vaccines against Hemagglutinin (HA), Neuraminidase (NA) and M2e, individually and in combination. Peptide composite vaccines, conjugated to CRM were administered subcutaneously with adjuvant and at least two booster doses. Serum antibody titers were analyzed using an anti-influenza ELISA for binding activity to peptides and live influenza viruses (H3N2 and H1N1) and functional activity was evaluated in vitro using Microneutralization, Hemagglutination Inhibition (HAI), and Antibody-Dependent Cellular Cytotoxicity (ADCC) assays.

Results

Mice given the peptide composite conjugate vaccines, individually and in combination, had strong humoral responses producing high serum anti-influenza titers post-booster immunization. Anti-influenza serum antibodies demonstrated functional activity against influenza A (H3N2 and H1N1) contemporary strains showing neutralization, HAI and ADCC activity.

Conclusion

Peptide conjugate vaccines were highly immunogenic in mice. Broadly reactive serum antibodies against the peptides and live influenza viruses were detected. These vaccines individually or in combination, induced antibodies that demonstrated functional activity against contemporary influenza strains in Group 1 and 2 and induced functional anti-influenza monoclonal antibodies. A vaccine that targets one or more HA, NA and M2e influenza epitopes may more closely approach the goal for a true universal influenza vaccine. In vivo protection studies are currently being designed.

Disclosures

All authors: No reported disclosures.

Opsonic monoclonal antibodies enhance phagocytic killing activity and clearance of Mycobacterium tuberculosis from blood in a quantitative qPCR mouse model

Background

Patients with impaired immunity often have rapid progression of tuberculosis (TB) which can lead to highly lethal Mycobacterium tuberculosis (MTB) sepsis. Opsonic monoclonal antibodies (MABs) directed against MTB that enhance phagocytic killing activity and clearance of MTB from blood may be useful to enhance TB immunity.

Methods

BALB/c mice were immunized with ethanol-killed MTB (EK-MTB) and MABs were produced and screened by ELISA for binding to killed and live Mycobacterium smegmatis (SMEG) and MTB. MAB opsonophagocytic killing activity (OPKA) was examined using SMEG with HL60 and U-937 cells and MTB with U-937 cells. Clearance of MTB from blood was evaluated in Institute of Cancer Research (ICR) mice given opsonic anti-MTB MABs or saline (control) 24 h prior to intravenous infusion with 10⁸ CFUs gamma-irradiated MTB (HN878). MTB levels in murine blood collected 0.25, 4 and 24 h post-challenge were assessed by qPCR. MAB binding to peptidoglycan (PGN) was examined by ELISA using PGN cell wall mixture and ultra-pure PGN.

Results

Two MABs (GG9 and JG7) bound to killed and live SMEG and MTB (susceptible and resistant), and promoted OPKA with live MTB. MAB JG7 significantly enhanced OPKA of MTB. Both MABs significantly enhanced clearance of killed MTB from murine blood at 4 and 24 h as measured by qPCR. These opsonic MABs bound to PGN, a major cell wall constituent.

Conclusions

Anti-MTB MABs that promote bactericidal phagocytic activity of MTB and enhance clearance of killed MTB from the blood, may offer an immunotherapeutic approach for treatment of MTB bacteremia or sepsis, and augment treatment of multi-drug resistant (MDR) or extensively drug resistant (XDR) TB.