SCB-2019 protein vaccine as heterologous booster of neutralizing activity against SARS-CoV-2 Omicron variants after immunization with other COVID-19 vaccines.

We assessed the non-inferiority of homologous boosting compared with heterologous boosting with the recombinant protein vaccine, SCB-2019, in adults previously immunized with different COVID-19 vaccines. Three equal cohorts (N ~ 420) of Philippino adults (18-80 years) previously immunized with Comirnaty, CoronaVac or Vaxzevria COVID-19 vaccines were randomized 1:1 to receive homologous or heterologous (SCB-2019) boosters. Neutralizing antibodies against prototype SARS-CoV-2 (Wuhan-Hu-1) were measured in all participants and against Delta variant and Omicron sub-lineages in subsets (30‒50 per arm) 15 days after boosting. Participants recorded solicited adverse events for 7 days and unsolicited and serious adverse events until Day 60. Prototype SARS-CoV-2 neutralizing responses on Day 15 after SCB-2019 were statistically non-inferior to homologous Vaxzevria boosters, superior to CoronaVac, but lower than homologous Comirnaty. Neutralizing responses against Delta and Omicron BA.1, BA.2, BA.4 and BA.5 variants after heterologous SCB-2019 were higher than homologous CoronaVac or Vaxzevria, but lower than homologous Comirnaty. Responses against Omicron BF.7, BQ.1.1.3, and XBB1.5 following heterologous SCB-2019 were lower than after homologous Comirnaty booster but significantly higher than after Vaxzevria booster. SCB-2019 reactogenicity was similar to CoronaVac or Vaxzevria, but lower than Comirnaty; most frequent events were mild/moderate injection site pain, headache and fatigue. No vaccine-related serious adverse events were reported. Heterologous SCB-2019 boosting was well tolerated and elicited neutralizing responses against all tested SARS-COV-2 viruses including Omicron BA.1, BA.2, BA.4, BA.5, BF.7, BQ.1.1.3, and XBB1.5 sub-lineages that were non-inferior to homologous boosting with CoronaVac or Vaxzevria, but not homologous Comirnaty booster.

Superior Boosting of Neutralizing Titers Against Omicron SARS-CoV-2 Variants by Heterologous SCB-2019 Vaccine vs a Homologous Booster in CoronaVac-Primed Adults.

BACKGROUND: We compared homologous and heterologous boosting in adults in the Philippines primed with 2 or 3 doses of CoronaVac, with recombinant protein vaccine, SCB-2019. METHODS: CoronaVac-immunized adults (18-72 years) received a homologous or heterologous full or half dose SCB-2019 booster. We assessed all neutralizing antibody (NAb) responses against prototype SARS-CoV-2 after 15 days and NAb against SARS-CoV-2 Delta and Omicron variants in subsets (30‒50 per arm). Participants recorded adverse events. RESULTS: In 2-dose CoronaVac-primed adults prototype NAb geometric mean titers (GMT) were 203 IU/mL (95% confidence interval [CI], 182-227) and 939 IU/mL (95% CI, 841-1049) after CoronaVac and SCB-2019 boosters; the GMT ratio (4.63; 95% CI, 3.95-5.41) met predefined noninferiority and post-hoc superiority criteria. After 3-dose CoronaVac-priming prototype NAb GMTs were 279 IU/mL (95% CI, 240-325), 1044 IU/mL (95% CI, 898-1213), and 668 IU/mL (95% CI, 520-829) following CoronaVac, full and half-dose SCB-2019 boosters, respectively. NAb GMT ratios against Delta and Omicron comparing SCB-2019 with CoronaVac were all greater than 2. Mild to moderate reactogenicity was evenly balanced between groups. No vaccine-related serious adverse events were reported. CONCLUSIONS: Full or half dose SCB-2019 boosters were well tolerated with superior immunogenicity than homologous CoronaVac, particularly against newly emerged variants. Clinical Trials Registration. NCT05188677.

Immunogenicity of an adjuvanted SARS-CoV-2 trimeric S-protein subunit vaccine (SCB-2019) in SARS-CoV-2-naïve and exposed individuals in a phase 2/3, double-blind, randomized study.

BACKGROUND: We evaluated immunogenicity of SCB-2019, a subunit vaccine candidate containing a pre-fusion trimeric form of the SARS-CoV-2 spike (S)-protein adjuvanted with CpG-1018/alum. METHODS: The phase 2/3, double-blind, randomized SPECTRA trial was conducted in five countries in participants aged ≥ 18 years, either SARS-CoV-2-naïve or previously exposed. Participants were randomly assigned to receive two doses of SCB-2019 or placebo administered intramuscularly 21 days apart. In the phase 2 part of the study, on days 1, 22, and 36, neutralizing antibodies were measured by pseudovirus and wild-type virus neutralization assays to SARS-CoV-2 prototype and variants, and ACE2-receptor-binding antibodies and SCB-2019-binding antibodies were measured by ELISA. Cell-mediated immunity was measured by intracellular cytokine staining via flow cytometry. RESULTS: 1601 individuals were enrolled between 24 March and 13 September 2021 and received at least one vaccine dose. Immunogenicity analysis was conducted in a phase 2 subset of 691 participants, including 428 SARS-CoV-2-naïve (381 vaccine and 47 placebo recipients) and 263 SARS-CoV-2-exposed (235 vaccine and 28 placebo recipients). In SARS-CoV-2-naïve participants, GMTs of neutralizing antibodies against prototype virus increased 2 weeks post-second dose (day 36) compared to baseline (224 vs 12.7 IU/mL). Seroconversion rate was 82.5 %. In SARS-CoV-2-exposed participants, one SCB-2019 dose increased GMT of neutralizing antibodies by 48.3-fold (1276.1 IU/mL on day 22) compared to baseline. Seroconversion rate was 92.4 %. Increase was marginal post-second dose. SCB-2019 also showed cross-neutralization capability against nine variants, including Omicron, in SARS-CoV-2-exposed participants at day 36. SCB-2019 stimulated Th1-biased cell-mediated immunity to the S-protein in both naïve and exposed participants. The vaccine was well tolerated, no safety concerns were raised from the study. CONCLUSIONS: A single dose of SCB-2019 was immunogenic in SARS-CoV-2-exposed individuals, whereas two doses were required to induce immune response in SARS-CoV-2-naïve individuals. SCB-2019 elicited a cross-neutralizing response against emergent SARS-CoV-2 variants at antibody levels associated with clinical protection, underlining its potential as a booster. CLINICALTRIALS: gov: NCT04672395; EudraCT: 2020-004272-17.

Impact of previous exposure to SARS-CoV-2 and of S-Trimer (SCB-2019) COVID-19 vaccination on the risk of reinfection: a randomised, double-blinded, placebo-controlled, phase 2 and 3 trial.

BACKGROUND: We previously reported the efficacy of the adjuvanted-protein COVID-19 vaccine candidate S-Trimer (SCB-2019) in adults who showed no evidence of previous exposure to SARS-CoV-2. In this study, we aimed to investigate the extent of protection afforded by previous exposure to SARS-CoV-2 on subsequent COVID-19 infection, as well as the efficacy, safety, and reactogenicity of SCB-2019 in participants who were enrolled in the Study evaluating Protective-Efficacy and safety of Clover's Trimeric Recombinant protein-based and Adjuvanted COVID-19 vaccine (SPECTRA) trial who had already been exposed to SARS-CoV-2 before vaccination. METHODS: In a phase 2 and 3 multicentre, double-blind, randomised, placebo-controlled trial (SPECTRA) done at 31 sites in five countries, participants were randomly assigned 1:1 using the Cenduit Interactive Response Technology system (IQVIA, Durham, NC, USA), with a block size of six, to receive two doses of either SCB-2019 or placebo 21 days apart. The primary outcomes of the SPECTRA trial were vaccine efficacy, measured by real-time PCR (rtPCR)-confirmed COVID-19 of any severity, with onset from 14 days after the second vaccine dose, as well as the safety and solicited local and systemic adverse events in the phase 2 subset. Here, we present secondary analyses to calculate the protective efficacy due to previous exposure to SARS-CoV-2 against reinfection with COVID-19 according to severity in SPECTRA participants who had evidence of exposure to SARS-CoV-2 at baseline, including efficacy against identified viral variants, as well as efficacy of SCB-2019 vaccination in this population. FINDINGS: We enrolled 30 174 participants between March 24, 2021, and Aug 10, 2021. In the 14 670 participants who were randomly assigned to receive placebo, there were 418 (2·8%) confirmed cases of COVID-19; 65 (0·9%) of 7339 SARS-CoV-2-exposed participants, and 353 (4·8%) of 7331 SARS-CoV-2-naive participants (attack rates of 5·5 cases per 100 person-years for SARS-CoV-2-exposed participants and 32·4 cases per 100 person-years for SARS-CoV-2-naive participants). Protective efficacy due to previous exposure to SARS-CoV-2 was 83·2% (95% CI 78·0-87·3) against any COVID-19, 92·5% (82·9-97·3) against moderate-to-severe COVID-19, and 100% (59·3-100) against severe COVID-19; no SARS-CoV-2-exposed participants had hospitalisation associated with COVID-19. Protective efficacy against variants were 100% for alpha (B.1.1.7) and lambda (C.37) variants, 88·6% (14·9-99·7) for B.1.623, 93·6% (80·1-98·7) for gamma (P.1), and 92·4% (81·2-97·6) for mu (B.1.621) variants, and lowest against beta (B.1.351; 72·2% [33·1-89·9]) and delta (B.1.617.2; 77·2% [61·3-87·2]) variants. In addition, one dose of SCB-2019 had 49·9% (1·5-75·6) efficacy against any symptomatic COVID-19, and two doses had 64·2% (26·5-83·8) efficacy. SCB-2019 was well tolerated in SARS-CoV-2-exposed participants, but was associated with higher rates of injection site pain (89 [33·8%] of 263 participants) than placebo (16 [6·7%] of 239 participants). Rates of solicited systemic adverse events, severe adverse events, and serious adverse events were similar between vaccine and placebo groups, and with rates in SARS-CoV-2-naive vaccine recipients. INTERPRETATION: Previous exposure to SARS-CoV-2 decreased the risk and severity of subsequent COVID-19 infection, even against newly emerging variants. Protection is further enhanced by one or two doses of SCB-2019. FUNDING: Clover Biopharmaceuticals, The Coalition for Epidemic Preparedness Innovations (CEPI).

Efficacy of the adjuvanted subunit protein COVID-19 vaccine, SCB-2019: a phase 2 and 3 multicentre, double-blind, randomised, placebo-controlled trial.

BACKGROUND: A range of safe and effective vaccines against SARS CoV 2 are needed to address the COVID 19 pandemic. We aimed to assess the safety and efficacy of the COVID-19 vaccine SCB-2019. METHODS: This ongoing phase 2 and 3 double-blind, placebo-controlled trial was done in adults aged 18 years and older who were in good health or with a stable chronic health condition, at 31 sites in five countries (Belgium, Brazil, Colombia, Philippines, and South Africa). The participants were randomly assigned 1:1 using a centralised internet randomisation system to receive two 0·5 mL intramuscular doses of SCB-2019 (30 µg, adjuvanted with 1·50 mg CpG-1018 and 0·75 mg alum) or placebo (0·9% sodium chloride for injection supplied in 10 mL ampoules) 21 days apart. All study staff and participants were masked, but vaccine administrators were not. Primary endpoints were vaccine efficacy, measured by RT-PCR-confirmed COVID-19 of any severity with onset from 14 days after the second dose in baseline SARS-CoV-2 seronegative participants (the per-protocol population), and the safety and solicited local and systemic adverse events in the phase 2 subset. This study is registered on EudraCT (2020-004272-17) and ClinicalTrials.gov (NCT04672395). FINDINGS: 30 174 participants were enrolled from March 24, 2021, until the cutoff date of Aug 10, 2021, of whom 30 128 received their first assigned vaccine (n=15 064) or a placebo injection (n=15 064). The per-protocol population consisted of 12 355 baseline SARS-CoV-2-naive participants (6251 vaccinees and 6104 placebo recipients). Most exclusions (13 389 [44·4%]) were because of seropositivity at baseline. There were 207 confirmed per-protocol cases of COVID-19 at 14 days after the second dose, 52 vaccinees versus 155 placebo recipients, and an overall vaccine efficacy against any severity COVID-19 of 67·2% (95·72% CI 54·3-76·8), 83·7% (97·86% CI 55·9-95·4) against moderate-to-severe COVID-19, and 100% (97·86% CI 25·3-100·0) against severe COVID-19. All COVID-19 cases were due to virus variants; vaccine efficacy against any severity COVID-19 due to the three predominant variants was 78·7% (95% CI 57·3-90·4) for delta, 91·8% (44·9-99·8) for gamma, and 58·6% (13·3-81·5) for mu. No safety issues emerged in the follow-up period for the efficacy analysis (median of 82 days [IQR 63-103]). The vaccine elicited higher rates of mainly mild-to-moderate injection site pain than the placebo after the first (35·7% [287 of 803] vs 10·3% [81 of 786]) and second (26·9% [189 of 702] vs 7·4% [52 of 699]) doses, but the rates of other solicited local and systemic adverse events were similar between the groups. INTERPRETATION: Two doses of SCB-2019 vaccine plus CpG and alum provides notable protection against the entire severity spectrum of COVID-19 caused by circulating SAR-CoV-2 viruses, including the predominating delta variant. FUNDING: Clover Biopharmaceuticals and the Coalition for Epidemic Preparedness Innovations.

Immunogenicity of SCB-2019 Coronavirus Disease 2019 Vaccine Compared With 4 Approved Vaccines.

A significant correlation has been shown between the binding antibody responses against original severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and vaccine efficacy of 4 approved coronavirus disease 2019 vaccines. We therefore assessed the immune response against original SARS-CoV-2 elicited by the adjuvanted S-Trimer vaccine, SCB-2019 + CpG/alum, in the same assay and laboratory. Responses to SCB-2019 were comparable or superior for antibody to original and Alpha variant when compared with 4 approved vaccines. The comparison accurately predicted success of the recently reported efficacy trial of SCB-2019 vaccine. Immunogenicity comparisons to original strain and variants of concern should be considered as a basis for authorization of vaccines.

Towards a population-based threshold of protection for COVID-19 vaccines.

Correlates of protection for COVID-19 vaccines are urgently needed to license additional vaccines. We measured immune responses to four COVID-19 vaccines of proven efficacy using a single serological platform. IgG anti-Spike antibodies were highly correlated with ID50 neutralization in a validated pseudoviral assay and correlated significantly with efficacies for protection against infection with wild-type, alpha and delta variant SARS-CoV-2 virus. The protective threshold for each vaccine was calculated for IgG anti-Spike antibody. The mean protective threshold for all vaccine studies for WT virus was 154 BAU/ml (95 %CI 42-559), and for studies with antibody distributions that enabled precise estimation of thresholds (i.e. leaving out 2-dose mRNA regimens) was 60 BAU/ml (95 %CI 35-102). We propose that the proportion of individuals with responses above the appropriate protective threshold together with the geometric mean concentration can be used in comparative non-inferiority studies with licensed vaccines to ensure that new vaccines will be efficacious.

Evidence for antibody as a protective correlate for COVID-19 vaccines.

A correlate of protection (CoP) is urgently needed to expedite development of additional COVID-19 vaccines to meet unprecedented global demand. To assess whether antibody titers may reasonably predict efficacy and serve as the basis of a CoP, we evaluated the relationship between efficacy and in vitro neutralizing and binding antibodies of 7 vaccines for which sufficient data have been generated. Once calibrated to titers of human convalescent sera reported in each study, a robust correlation was seen between neutralizing titer and efficacy (ρ = 0.79) and binding antibody titer and efficacy (ρ = 0.93), despite geographically diverse study populations subject to different forces of infection and circulating variants, and use of different endpoints, assays, convalescent sera panels and manufacturing platforms. Together with evidence from natural history studies and animal models, these results support the use of post-immunization antibody titers as the basis for establishing a correlate of protection for COVID-19 vaccines.

Consensus summary report for CEPI/BC March 12-13, 2020 meeting: Assessment of risk of disease enhancement with COVID-19 vaccines.

A novel coronavirus (CoV), Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in late 2019 in Wuhan, China and has since spread as a global pandemic. Safe and effective vaccines are thus urgently needed to reduce the significant morbidity and mortality of Coronavirus Disease 2019 (COVID-19) disease and ease the major economic impact. There has been an unprecedented rapid response by vaccine developers with now over one hundred vaccine candidates in development and at least six having reached clinical trials. However, a major challenge during rapid development is to avoid safety issues both by thoughtful vaccine design and by thorough evaluation in a timely manner. A syndrome of "disease enhancement" has been reported in the past for a few viral vaccines where those immunized suffered increased severity or death when they later encountered the virus or were found to have an increased frequency of infection. Animal models allowed scientists to determine the underlying mechanism for the former in the case of Respiratory syncytial virus (RSV) vaccine and have been utilized to design and screen new RSV vaccine candidates. Because some Middle East respiratory syndrome (MERS) and SARS-CoV-1 vaccines have shown evidence of disease enhancement in some animal models, this is a particular concern for SARS-CoV-2 vaccines. To address this challenge, the Coalition for Epidemic Preparedness Innovations (CEPI) and the Brighton Collaboration (BC) Safety Platform for Emergency vACcines (SPEAC) convened a scientific working meeting on March 12 and 13, 2020 of experts in the field of vaccine immunology and coronaviruses to consider what vaccine designs could reduce safety concerns and how animal models and immunological assessments in early clinical trials can help to assess the risk. This report summarizes the evidence presented and provides considerations for safety assessment of COVID-19 vaccine candidates in accelerated vaccine development.

History of passive antibody administration for prevention and treatment of infectious diseases.

PURPOSE OF REVIEW: We describe the history of passive immunization to provide context for the series of articles to follow. The history of passive immunization with antibodies to prevent or treat infectious diseases is a story of different eras. There was an extraordinary era of discovery and clinical implementation before the chemical nature of antibodies was even known. This empirical process provided the resources and reagents used to describe and characterize humoral immunity, better define the chemical properties and structure of antibodies, and extend the clinical use of immunoglobulin products to treat or prevent multiple viral and bacterial diseases over the ensuing several decades. The next distinct era came with the discovery of processes to produce monoclonal antibodies (mAbs), and development of more specific therapies. Interestingly, mAb technology resulted in many products to treat autoimmune and allergic diseases, but only one common infectious disease, respiratory syncytial virus, and only in a restricted population of high-risk infants. RECENT FINDINGS: The current era began in 2003 with a series of publications demonstrating processes for rapidly producing human mAbs. SUMMARY: This technology combined with new sequencing technology, advances in structural biology, atomic-level molecular design, and increased capacity for synthetic biology, promises new opportunities to apply passive immunization to the prevention and treatment of infectious diseases.

High-throughput sequencing analysis of post-liver transplantation HCV E2 glycoprotein evolution in the presence and absence of neutralizing monoclonal antibody.

Chronic hepatitis C virus (HCV) infection is the most common cause of end-stage liver disease, often leading to liver transplantation, in which case circulating virions typically infect the transplanted liver within hours and viral concentrations can quickly exceed pre-transplant levels. MBL-HCV1 is a fully human monoclonal antibody recognizing a linear epitope of the HCV E2 envelope glycoprotein (amino acids 412-423). The ability of MBL-HCV1 to prevent HCV recurrence after liver transplantation was investigated in a phase 2 randomized clinical trial evaluating six MBL-HCV1-treated subjects and five placebo-treated subjects. MBL-HCV1 treatment significantly delayed time to viral rebound compared with placebo treatment. Here we report results from high-throughput sequencing on the serum of each of the eleven enrolled subjects prior to liver transplantation and after viral rebound. We further sequenced the sera of the MBL-HCV1-treated subjects at various interim time points to study the evolution of antibody-resistant viral variants. We detected mutations at one of two positions within the antibody epitope--mutations of N at position 415 to D, K or S, or mutation of N at position 417 to S. It has been previously reported that N415 is not glycosylated in the wild-type E2 protein, but N417S can lead to glycosylation at position 415. Thus N415 is a key position for antibody recognition and the only routes we identified for viral escape, within the constraints of HCV fitness in vivo, involve mutating or glycosylating this position. Evaluation of mutations along the entire E1 and E2 proteins revealed additional positions that changed moderately before and after MBL-HCV1 treatment for subsets of the six subjects, yet underscored the relative importance of position 415 in MBL-HCV1 resistance.

Identification of human monoclonal antibodies specific for human SOD1 recognizing distinct epitopes and forms of SOD1.

Mutations in the gene encoding human SOD1 (hSOD1) can cause amyotrophic lateral sclerosis (ALS) yet the mechanism by which mutant SOD1 can induce ALS is not fully understood. There is currently no cure for ALS or treatment that significantly reduces symptoms or progression. To develop tools to understand the protein conformations present in mutant SOD1-induced ALS and as possible immunotherapy, we isolated and characterized eleven unique human monoclonal antibodies specific for hSOD1. Among these, five recognized distinct linear epitopes on hSOD1 that were not available in the properly-folded protein but were available on forms of protein with some degree of misfolding. The other six antibodies recognized conformation-dependent epitopes that were present in the properly-folded protein with two different recognition profiles: three could bind hSOD1 dimer or monomer and the other three were specific for hSOD1 dimer only. Antibodies with the capacity to bind hSOD1 monomer were able to prevent increased hydrophobicity when mutant hSOD1 was exposed to increased temperature and EDTA, suggesting that the antibodies stabilized the native structure of hSOD1. Two antibodies were tested in a G93A mutant hSOD1 transgenic mouse model of ALS but did not yield a statistically significant increase in overall survival. It may be that the two antibodies selected for testing in the mouse model were not effective for therapy or that the model and/or route of administration were not optimal to produce a therapeutic effect. Therefore, additional testing will be required to determine therapeutic potential for SOD1 mutant ALS and potentially some subset of sporadic ALS.

Human monoclonal antibody HCV1 effectively prevents and treats HCV infection in chimpanzees.

Hepatitis C virus (HCV) infection is a leading cause of liver transplantation and there is an urgent need to develop therapies to reduce rates of HCV infection of transplanted livers. Approved therapeutics for HCV are poorly tolerated and are of limited efficacy in this patient population. Human monoclonal antibody HCV1 recognizes a highly-conserved linear epitope of the HCV E2 envelope glycoprotein (amino acids 412-423) and neutralizes a broad range of HCV genotypes. In a chimpanzee model, a single dose of 250 mg/kg HCV1 delivered 30 minutes prior to infusion with genotype 1a H77 HCV provided complete protection from HCV infection, whereas a dose of 50 mg/kg HCV1 did not protect. In addition, an acutely-infected chimpanzee given 250 mg/kg HCV1 42 days following exposure to virus had a rapid reduction in viral load to below the limit of detection before rebounding 14 days later. The emergent virus displayed an E2 mutation (N415K/D) conferring resistance to HCV1 neutralization. Finally, three chronically HCV-infected chimpanzees were treated with a single dose of 40 mg/kg HCV1 and viral load was reduced to below the limit of detection for 21 days in one chimpanzee with rebounding virus displaying a resistance mutation (N417S). The other two chimpanzees had 0.5-1.0 log(10) reductions in viral load without evidence of viral resistance to HCV1. In vitro testing using HCV pseudovirus (HCVpp) demonstrated that the sera from the poorly-responding chimpanzees inhibited the ability of HCV1 to neutralize HCVpp. Measurement of antibody responses in the chronically-infected chimpanzees implicated endogenous antibody to E2 and interference with HCV1 neutralization although other factors may also be responsible. These data suggest that human monoclonal antibody HCV1 may be an effective therapeutic for the prevention of graft infection in HCV-infected patients undergoing liver transplantation.

G glycoprotein amino acid residues required for human monoclonal antibody RAB1 neutralization are conserved in rabies virus street isolates.

Replacement of polyclonal anti-rabies immunoglobulin (RIG) used in rabies post-exposure prophylaxis (PEP) with a monoclonal antibody will eliminate cost and availability constraints that currently exist using RIG in the developing world. The human monoclonal antibody RAB1 has been shown to neutralize all rabies street isolates tested; however for the laboratory-adapted fixed strain, CVS-11, mutation in the G glycoprotein of amino acid 336 from asparagine (N) to aspartic acid (D) resulted in resistance to neutralization. Interestingly, this same mutation in the G glycoprotein of a second laboratory-adapted fixed strain (ERA) did not confer resistance to RAB1 neutralization. Using cell surface staining and lentivirus pseudotyped with rabies virus G glycoprotein (RABVpp), we identified an amino acid alteration in CVS-11 (K346), not present in ERA (R346), which was required in combination with D336 to confer resistance to RAB1. A complete analysis of G glycoprotein sequences from GenBank demonstrated that no identified rabies isolates contain the necessary combination of G glycoprotein mutations for resistance to RAB1 neutralization, consistent with the broad neutralization of RAB1 observed in direct viral neutralization experiments with street isolates. All combinations of amino acids 336 and 346 reported in the sequence database were engineered into the ERA G glycoprotein and RAB1 was able to neutralize RABVpp bearing ERA G glycoprotein containing all known combinations at these critical residues. These data demonstrate that RAB1 has the capacity to neutralize all identified rabies isolates and a minimum of two distinct mutations in the G glycoprotein are required for abrogation of RAB1 neutralization.

Treatment with monoclonal antibodies against Clostridium difficile toxins.

BACKGROUND: New therapies are needed to manage the increasing incidence, severity, and high rate of recurrence of Clostridium difficile infection. METHODS: We performed a randomized, double-blind, placebo-controlled study of two neutralizing, fully human monoclonal antibodies against C. difficile toxins A (CDA1) and B (CDB1). The antibodies were administered together as a single infusion, each at a dose of 10 mg per kilogram of body weight, in patients with symptomatic C. difficile infection who were receiving either metronidazole or vancomycin. The primary outcome was laboratory-documented recurrence of infection during the 84 days after the administration of monoclonal antibodies or placebo. RESULTS: Among the 200 patients who were enrolled (101 in the antibody group and 99 in the placebo group), the rate of recurrence of C. difficile infection was lower among patients treated with monoclonal antibodies (7% vs. 25%; 95% confidence interval, 7 to 29; P<0.001). The recurrence rates among patients with the epidemic BI/NAP1/027 strain were 8% for the antibody group and 32% for the placebo group (P=0.06); among patients with more than one previous episode of C. difficile infection, recurrence rates were 7% and 38%, respectively (P=0.006). The mean duration of the initial hospitalization for inpatients did not differ significantly between the antibody and placebo groups (9.5 and 9.4 days, respectively). At least one serious adverse event was reported by 18 patients in the antibody group and by 28 patients in the placebo group (P=0.09). CONCLUSIONS: The addition of monoclonal antibodies against C. difficile toxins to antibiotic agents significantly reduced the recurrence of C. difficile infection. (ClinicalTrials.gov number, NCT00350298.)

Serum anti-toxin B antibody correlates with protection from recurrent Clostridium difficile infection (CDI).

BACKGROUND: Previous studies have demonstrated a correlation between Clostridium difficile anti-toxin A serum antibodies and protection against symptomatic disease and recurrence. METHODS: A neutralizing monoclonal antibody to C. difficile toxin A (CDA1) developed by MBL and Medarex, Inc. was studied in a phase II, randomized, double-blind, placebo-controlled trial in patients receiving standard of care treatment for C. difficile infection (CDI). Twenty-nine subjects received a single intravenous infusion of 10mg/kg CDA1 and 17 subjects received placebo and were evaluated for recurrence of CDI during the 56-day study period. Serum antibodies against C. difficile toxin A and B were measured by ELISA and cytotoxicity assay at various time points before and after infusion. FINDINGS: CDI recurrence occurred in 5 of 29 (17%) in the CDA1 group and 3 of 17 (18%) (p=NS) in the placebo group with a trend toward delay in time to recurrence in the group treated with CDA1. The geometric mean concentration of antibody to an epitope of the receptor-binding domain of toxin B (0.300 and 1.20microg/ml, respectively; p=0.02) and geometric mean titer of neutralizing B antibody (8.00 and 100, respectively; p=0.02) at study day 28 were lower for those subjects with recurrence compared to those who did not recur. In addition, a significantly greater proportion of subjects who recurred were infected with the epidemic BI/NAP1/027 strain compared with those that did not recur (88% vs. 22%; p=0.002). Finally, in a multiple logistic regression analysis neutralizing anti-toxin B at day 14 (p<0.001), anti-toxin A at day 28 (p<0.001) and infection with the BI/NAP1/027 strain at enrollment (p=0.002) were all predictive of CDI recurrence. INTERPRETATION: In this prospective study, lower concentrations of neutralizing anti-toxin B and anti-toxin A antibody and infection with the BI/NAP1/027 strain of C. difficile were significantly associated with recurrence of CDI.

Identification and characterization of broadly neutralizing human monoclonal antibodies directed against the E2 envelope glycoprotein of hepatitis C virus.

Nearly all livers transplanted into hepatitis C virus (HCV)-positive patients become infected with HCV, and 10 to 25% of reinfected livers develop cirrhosis within 5 years. Neutralizing monoclonal antibody could be an effective therapy for the prevention of infection in a transplant setting. To pursue this treatment modality, we developed human monoclonal antibodies (HuMAbs) directed against the HCV E2 envelope glycoprotein and assessed the capacity of these HuMAbs to neutralize a broad panel of HCV genotypes. HuMAb antibodies were generated by immunizing transgenic mice containing human antibody genes (HuMAb mice; Medarex Inc.) with soluble E2 envelope glycoprotein derived from a genotype 1a virus (H77). Two HuMAbs, HCV1 and 95-2, were selected for further study based on initial cross-reactivity with soluble E2 glycoproteins derived from genotypes 1a and 1b, as well as neutralization of lentivirus pseudotyped with HCV 1a and 1b envelope glycoproteins. Additionally, HuMAbs HCV1 and 95-2 potently neutralized pseudoviruses from all genotypes tested (1a, 1b, 2b, 3a, and 4a). Epitope mapping with mammalian and bacterially expressed proteins, as well as synthetic peptides, revealed that HuMAbs HCV1 and 95-2 recognize a highly conserved linear epitope spanning amino acids 412 to 423 of the E2 glycoprotein. The capacity to recognize and neutralize a broad range of genotypes, the highly conserved E2 epitope, and the fully human nature of the antibodies make HuMAbs HCV1 and 95-2 excellent candidates for treatment of HCV-positive individuals undergoing liver transplantation.

Recombinant protein-based assays for detection of antibodies to severe acute respiratory syndrome coronavirus spike and nucleocapsid proteins.

Recombinant severe acute respiratory syndrome (SARS) nucleocapsid and spike protein-based immunoglobulin G immunoassays were developed and evaluated. Our assays demonstrated high sensitivity and specificity to the SARS coronavirus in sera collected from patients as late as 2 years postonset of symptoms. These assays will be useful not only for routine SARS coronavirus diagnostics but also for epidemiological and antibody kinetic studies.

Identification and characterization of a human monoclonal antibody that potently neutralizes a broad panel of rabies virus isolates.

Rabies is a zoonosis that results in millions of human exposures worldwide each year. Human monoclonal antibodies (HuMAbs) that neutralize rabies virus may represent one viable strategy for post-exposure prophylaxis in humans, and have many advantages over current human or equine rabies immune globulin. Transgenic mice carrying human immunoglobulin genes were used to isolate human monoclonal antibodies that neutralized rabies virus. Several HuMAbs were identified that neutralized rabies virus variants from a broad panel of isolates of public health significance. HuMAb 17C7 was the most promising antibody identified because it neutralized all rabies virus isolates tested. HuMAb 17C7 recognizes a conformational epitope on the rabies virus glycoprotein which includes antigenic site III. HuMAb 17C7 protected hamsters from a lethal dose of rabies virus in a well-established in vivo model of post-exposure prophylaxis.