Anti-SUDV GP monoclonal antibody, clone 27G7

Background: Profiles of immunity developed in filovirus patients and survivors have begun to shed light on antigen-specific cellular immune responses that had been previously under-studied. However, our knowledge of the breadth and length of those responses and the viral targets which mediate long-term memory immunity still lags significantly behind. Methods: We characterized antigen-specific immune responses in whole blood samples of fifteen years post-infected survivors of the Sudan virus (SUDV) outbreak in Gulu, Uganda (2000-2001). We examined T cell and IgG responses against SUDV complete antigen and four SUDV proteins; glycoprotein (GP), nucleoprotein (NP), and viral protein 30 (VP30), and 40 (VP40). Findings: We found survivors-maintained antigen-specific CD4+ T cell memory immune responses mediated mainly by the viral protein NP. In contrast, activated CD8+ T cell responses were nearly absent in SUDV survivors, regardless of the stimulating antigen used. Analysis of anti-viral humoral immunity revealed antigen-specific IgG antibodies against SUDV and SUDV proteins. Survivor IgGs mediated live SUDV neutralization in vitro and Fc gamma RI and Fc gamma RIII antibody Fc-dependent responses, mainly via antibodies to the viral proteins GP and VP40. Interpretation: We highlight the key role of several proteins, i.e., GP, NP, and VP40, to act as mediators of distinctive and sustained cellular memory immune responses in long-term SUDV survivors. We suggest that the inclusion of these viral proteins in vaccine development may best mimic survivor native memory immune responses with the potential of protecting against viral infection.

DNA vaccination of transchromosomal bovines (TcBs) with DNA vaccines expressing the codon-optimized (co) glycoprotein (GP) genes of Ebola virus (EBOV) and Sudan virus (SUDV) produce fully human polyclonal antibodies (pAbs) that recognize both viruses and demonstrate robust neutralizing activity. Each TcB was vaccinated by intramuscular electroporation (IM-EP) a total of four times and at each administration received 10 mg of the EBOV-GP(co) DNA vaccine and 10 mg of the SUDV-GP(co) DNA vaccine at two sites on the left and right sides, respectively. After two vaccinations, robust antibody responses (titers > 1000) were detected by ELISA against whole irradiated EBOV or SUDV and recombinant EBOV-GP or SUDV-GP (rGP) antigens, with higher titers observed for the rGP antigens. Strong, virus neutralizing antibody responses (titers > 1000) were detected after three vaccinations when measured by vesicular stomatitis virus-based pseudovirion neutralization assay (PsVNA). Maximal neutralizing antibody responses were identified by traditional plaque reduction neutralization tests (PRNT) after four vaccinations. Neutralizing activity of human immunoglobulins (IgG) purified from TcB plasma collected after three vaccinations and injected intraperitoneally (IP) into mice at a 100 mg/kg dose was detected in the serum by PsVNA up to 14 days after administration. Passive transfer by IP injection of the purified IgG (100 mg/kg) to groups of BALB/c mice one day after IP challenge with mouse adapted (ma) EBOV resulted in 80% protection while all mice treated with non-specific pAbs succumbed. Similarly, interferon receptor 1 knockout (IFNAR(-/-)) mice receiving the purified IgG (100 mg/kg) by IP injection one day after IP challenge with wild type SUDV resulted in 89% survival. These results are the first to demonstrate that filovirus GP DNA vaccines administered to TcBs by IM-EP can elicit neutralizing antibodies that provide post-exposure protection. Additionally, these data describe production of fully human IgG in a large animal system, a system which is capable of producing large quantities of a clinical grade therapeutic product.