Abstract NDV-HXP-S is a recombinant Newcastle disease virus based-vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which expresses an optimized (HexaPro) spike protein on its surface. The vaccine can be produced in embryonated chicken eggs using the same process as that employed for the production of influenza virus vaccines. Here we performed a secondary analysis of the antibody responses after vaccination with inactivated NDV-HXP-S in a Phase I clinical study in Thailand. The SARS-CoV-2 neutralizing and spike binding activity of NDV-HXP-S post-vaccination serum samples was compared to that of matched samples from mRNA BNT162b2 (Pfizer) vaccinees. Neutralizing activity of sera from NDV-HXP-S vaccinees was comparable to that of individuals vaccinated with BNT162b2. Interstingly, the spike binding activity of the NDV-HXP-S vaccinee samples was lower than that of sera obtained from individuals vaccinated with the mRNA vaccine. This let us to calculate ratios between binding and neutralizing antibody titers. Samples from NDV-HXP-S vaccinees had binding to neutralizing activity ratios similar to those of convalescent sera suggesting a very high proportion of neutralizing antibodies and low non-neutralizing antibody titers. Further analysis showed that, in contrast to mRNA vaccination, which induces strong antibody titers to the receptor binding domain (RBD), the N-terminal domain, and the S2 domain, NDV-HXP-S vaccination induces a very RBD focused response with little reactivity to S2. This explains the high proportion of neutralizing antibodies since most neutralizing epitopes are located in the RBD. In conclusion, vaccination with inactivated NDV-HXP-S induces a high proportion of neutralizing antibodies and absolute neutralizing antibody titers comparable to those after mRNA vaccination.
ABSTRACT Transmission of pathogenic avian influenza viruses (AIV) from wild birds to domestic poultry and humans is continuing in multiple countries around the world. In preparation for a potential AIV pandemic, multiple vaccine candidates are under development. In the case of H5N1 AIV, a clear shift in transmission from clade 1 to clade 2 viruses occurred in recent years. The virus-like particle (VLP) represents an economical approach to pandemic vaccine development. In the current study, we evaluated the humoral immune response in humans vaccinated with H5N1 A/Indonesia/05/2005 (clade 2.1) VLP vaccine manufactured in Sf9 insect cells. The VLPs were comprised of the influenza virus hemagglutinin (HA), neuraminidase (NA), and matrix 1 (M1) proteins. In an FDA-approved phase I/II human clinical study, two doses of H5N1 VLPs at 15, 45, or 90 μg HA/dose resulted in seroconversion and production of functional antibodies. Moreover, cross-reactivity against other clade 2 subtypes was demonstrated using virus neutralization assays. H5N1 whole-genome fragment phage display libraries (GFPDL) were used to elucidate the antibody epitope repertoire in postvaccination human sera. Diverse epitopes in HA1/HA2 and NA were recognized by postvaccination sera from the two high-dose groups, including large segments spanning the HA1 receptor binding domain. Importantly, the vaccine elicited sera that preferentially bound to an oligomeric form of recombinant HA1 compared with monomeric HA1. The oligomeric/monomeric HA1 binding ratios of the sera correlated with the virus neutralizing titers. Additionally, the two high-dose VLP vaccine groups generated NA-inhibiting antibodies that were associated with binding to a C-terminal epitope close to the sialic acid binding site. These findings represent the first report describing the quality of the antibody responses in humans following AIV VLP immunization and support further development of such vaccines against emerging influenza virus strains.
Production of affordable coronavirus disease 2019 (COVID-19) vaccines in low- and lower-middle-income countries is needed. NDV-HXP-S is an inactivated egg-based recombinant Newcastle disease virus vaccine expressing the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A public sector manufacturer in Vietnam assessed the immunogenicity of NDV-HXP-S (COVIVAC) relative to an authorized vaccine. Healthy males and non-pregnant females, 18 years of age and older, were eligible. Participants were randomised by age (18-59, ≥60 years) to receive one of three treatments by intramuscular injection twice, 28 days apart: COVIVAC at 3 µg or 6 µg, or AstraZeneca COVID-19 vaccine VAXZEVRIA. ClinicalTrials.gov NCT05940194.During August 10-23, 2021, 737 individuals were screened, and 374 were randomised (124-125 per group); all received dose one, and three missed dose two. On day 43, the geometric mean fold rise of 50% neutralising antibody titers for subjects age 18-59 years was 31·20 (COVIVAC 3 μg N=82, 95% CI 25·14-38·74), 35·80 (COVIVAC 6 μg; N=83, 95% CI 29·03-44·15), 18·85 (VAXZEVRIA; N=82, 95% CI 15·10-23·54), and for subjects age ≥60 years was 37·27 (COVIVAC 3 μg; N=42, 95% CI 27·43-50·63), 50·10 (COVIVAC 6 μg; N=40, 95% CI 35·46-70·76), 16·11 (VAXZEVRIA; N=40, 95% CI 11·73-22·13). Among subjects seronegative for anti-S IgG at baseline, the day 43 geometric mean titer ratio of neutralising antibody (COVIVC 6 μg/VAXZEVRIA) was 1·77 (95% CI 1·30-2·40) for subjects age 18-59 years and 3·24 (95% CI 1·98-5·32) for subjects age ≥60 years. On day 197, the age-specific ratios were 1·11 (95% CI 0·51-2·43) and 2·32 (0·69-7·85). Vaccines were well tolerated; reactogenicity was predominantly mild and transient. Considering that induction of neutralising antibodies against SARS-CoV-2 has been correlated with the efficacy of COVID-19 vaccines, including VAXZEVRIA, our results suggest that vaccination with COVIVAC may afford clinical benefit matching or exceeding that of the VAXZEVRIA vaccine.
Abstract Background . New strategies are needed to reduce the incidence of malaria, and promising approaches include the development of vaccines and monoclonal antibodies (mAbs) that target the circumsporozoite protein (CSP). To select the best candidates and speed development, it is essential to standardize preclinical assays to measure the potency of such interventions in animal models. Method . Two assay configurations were studied using transgenic P. berghei expressing P. falciparum full-length circumsporozoite protein. The assays measured 1) reduction in parasite infection of the liver (liver burden) following an intravenous (i.v) administration of sporozoites and 2) protection from parasitemia following mosquito bite challenge. Two human CSP mAbs, AB311 and AB317, were compared for their ability to inhibit infection. Multiple independent experiments were conducted to define assay variability and resultant impact on the ability to discriminate differences in mAb functional activity. Results . Overall, the assays produced highly consistent results in that all individual experiments showed greater functional activity for AB317 compared to AB311 as calculated by the dose required for 50 % inhibition (ID50) as well as the serum concentration required for 50% inhibition (IC50). The data were then used to model experimental designs with adequate statistical power to rigorously screen, compare, and rank order novel anti-CSP mAbs. Conclusion . Our results indicate that in vivo assays described here can provide reliable information for comparing the functional activity of mAbs. Our results also provide guidance regarding selection of the appropriate experimental design, dose selection, and group sizes.
Production of affordable coronavirus disease 2019 (COVID-19) vaccines in low- and lower-middle-income countries is needed. NDV-HXP-S is an inactivated egg-based recombinant Newcastle disease virus vaccine expressing the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A public sector manufacturer in Vietnam assessed the immunogenicity of NDV-HXP-S (COVIVAC) relative to an authorized vaccine. This phase 2 stage of a randomised, observer-blind, controlled, phase 1/2 trial was conducted at three community health centers in Thai Binh Province, Vietnam. Healthy males and non-pregnant females, 18 years of age and older, were eligible. Participants were randomised by age (18-59, ≥60 years) to receive one of three treatments by intramuscular injection twice, 28 days apart: COVIVAC at 3 μg or 6 μg, or AstraZeneca COVID-19 vaccine VAXZEVRIA™. Participants and personnel assessing outcomes were masked to treatment. The vaccine dose was selected based on Phase 1 results. A 6 μg dose was chosen to explore the immunogenicity gain over the 3-μg dose. The study's aim is to evaluate the safety and immunogenicity of COVIVAC at two dose levels compared to VAXZEVRIA, the most commonly used COVID-19 vaccine in Vietnam. The main outcome was the induction of 50% neutralising antibody titers against vaccine-homologous pseudotyped virus 14 days (day 43) and 6 months (day 197) after the second vaccination by age group. The primary immunogenicity and safety analyses included all participants who received one dose of the vaccine. ClinicalTrials.govNCT05940194. During August 10-23, 2021, 737 individuals were screened, and 374 were randomised (124-125 per group); all subjects received vaccine dose one and all but three received doses two four weeks later. Subjects 18-59 years of age achieved the following geometric mean titers of PNA 14 days after vaccine dose two: 153⋅28 (95 % CI 124·2-189⋅15) for COVIVAC 3 μg, 176⋅2 (95 % CI 141⋅45-220.27) for COVIVAC 6 μg, and 99⋅92(95 % CI 80.80-123⋅56) for VAXZEVRIA. Subjects ≥60 years of age also achieved potent geometric mean titers of PNA at the same timepoint: 183⋅57 (95 % CI 133.4-252⋅61) for COVIVAC 3 μg, 257⋅87 (95 % CI 181⋅6-367⋅18) for COVIVAC 6 μg, and 79⋅49(95 % CI 55⋅68-113⋅4) for VAXZEVRIA. On day 43, the geometric mean fold rise of 50 % neutralising antibody titers for subjects age 18-59 years was 31·20 (COVIVAC 3 μg N = 82, 95 % CI 25·14-38·74), 35·80 (COVIVAC 6 μg; N = 83, 95 % CI 29·03-44·15), 18·85 (VAXZEVRIA; N = 82, 95 % CI 15·10-23·54), and for subjects age ≥ 60 years was 37·27 (COVIVAC 3 μg; N = 42, 95 % CI 27·43-50·63), 50·10 (COVIVAC 6 μg; N = 40, 95 % CI 35·46-70·76), 16·11 (VAXZEVRIA; N = 40, 95 % CI 11·73-22·13). Among subjects seronegative for anti-S IgG at baseline, the day 43 geometric mean titer ratio of neutralising antibody (COVIVC 6 μg/VAXZEVRIA) was 1·77 (95 % CI 1·30-2·40) for subjects age 18-59 years and 3·24 (95 % CI 1·98-5·32) for subjects age ≥ 60 years. On day 197, the age-specific ratios were 1·11 (95 % CI 0·51-2·43) and 2·32 (0·69-7·85). Vaccines were well tolerated; reactogenicity was predominantly mild and transient. The percentage of subjects with unsolicited adverse events (AEs) during 28 days after vaccinations was similar among treatments (COVIVAC 3 μg 29·0 %, COVIVAC 6 μg 23·2 %, VAXZEVRIA 31·2 %); no vaccine-related AE was reported. Considering that induction of neutralising antibodies against SARS-CoV-2 has been correlated with the efficacy of COVID-19 vaccines, including VAXZEVRIA, our results suggest that vaccination with COVIVAC may afford clinical benefit matching or exceeding that of the VAXZEVRIA vaccine. ClinicalTrials.govNCT05940194.
NDV-HXP-S is a recombinant Newcastle disease virus–based vaccine against SARS-CoV-2, which expresses an optimized (HexaPro) spike protein on its surface. The vaccine can be produced in embryonated chicken eggs using the same process as that used for the production of the vast majority of influenza virus vaccines. Here, we performed a secondary analysis of the antibody responses after vaccination with inactivated NDV-HXP-S in a phase 1 clinical study in Thailand. The SARS-CoV-2 neutralizing and spike protein binding activity of NDV-HXP-S postvaccination serum samples was compared to that of samples from mRNA BNT162b2 (Pfizer) vaccinees. Neutralizing activity of sera from NDV-HXP-S vaccinees was comparable to that of BNT162b2 vaccinees, whereas spike protein binding activity of the NDV-HXP-S vaccinee samples was lower than that of sera obtained from mRNA vaccinees. This led us to calculate ratios between binding and neutralizing antibody titers. Samples from NDV-HXP-S vaccinees had binding to neutralizing activity ratios that were lower than those of BNT162b2 sera, suggesting that NDV-HXP-S vaccination elicits a high proportion of neutralizing antibodies and low non-neutralizing antibody titers. Further analysis showed that, in contrast to mRNA vaccination, which induces strong antibody titers to the receptor binding domain (RBD), the N-terminal domain, and the S2 domain, NDV-HXP-S vaccination induced an RBD-focused antibody response with little reactivity to S2. This finding may explain the high proportion of neutralizing antibodies. In conclusion, vaccination with inactivated NDV-HXP-S induces a high proportion of neutralizing antibodies and absolute neutralizing antibody titers that are comparable to those elicited by mRNA vaccination.
Respiratory Syncytial Virus (RSV) is an important viral agent causing severe respiratory tract disease in infants and children as well as in the elderly and immunocompromised individuals. The lack of a safe and effective RSV vaccine represents a major unmet medical need. RSV fusion (F) surface glycoprotein was modified and cloned into a baculovirus vector for efficient expression in Sf9 insect cells. Recombinant RSV F was glycosylated and cleaved into covalently linked F2 and F1 polypeptides that formed homotrimers. RSV F extracted and purified from insect cell membranes assembled into 40 nm protein nanoparticles composed of multiple RSV F oligomers arranged in the form of rosettes. The immunogenicity and protective efficacy of purified RSV F nanoparticles was compared to live and formalin inactivated RSV in cotton rats. Immunized animals induced neutralizing serum antibodies, inhibited virus replication in the lungs, and had no signs of disease enhancement in the respiratory track of challenged animals. RSV F nanoparticles also induced IgG competitive for binding of palivizumab neutralizing monoclonal antibody to RSV F antigenic site II. Antibodies to this epitope are known to protect against RSV when passively administered in high risk infants. Together these data provide a rational for continued development a recombinant RSV F nanoparticle vaccine candidate.
Respiratory syncytial virus (RSV) is a leading cause of respiratory illness among children and infants worldwide, yet no licensed vaccine exists to reduce the risk of disease. At least 16 RSV vaccine candidates are currently in clinical development and many are designed to induce robust virus neutralizing immune responses. RSV neutralizing antibody (nAb)-mediated interventions such as intravenous immunoglobulin (IVIG) and palivizumab provide passive protection against serious lower respiratory tract disease due to RSV, validating nAbs as a correlate of protection. To identify correlates of protection for vaccine candidates that have demonstrated their protective efficacy, an investigator can use assays designed to measure nAb responses. However, there is no standard method of measurement; individual laboratories have developed their own methods to measure the ability of nAbs to reduce the infectivity of a defined virus dose in a variety of cell lines, leading to establishment of the broad variety of RSV neutralization assay formats currently in use. Standardizing the RSV neutralization assay is an essential step toward better assessment of nAb responses to vaccine candidates. Use of a common reference standard by all makes comparing the immunogenicity of different vaccine candidates feasible. In the context of vaccine development, the WHO 1st International Standard for Antiserum to RSV (RSV IS) has been shown to be suitable for harmonizing results across laboratories and assay formats used to measure nAb titers to RSV/A and RSV/B in human sera. This review describes the broad variety of RSV virus neutralization assay formats currently in use and the importance of the RSV IS for harmonization of results across formats and across laboratories. It also outlines good practices for key assay components and data analysis to promote the quality and consistency of measuring RSV nAb titers in serum specimens.
Summary Background Production of affordable coronavirus disease 2019 (COVID-19) vaccines in low- and lower-middle-income countries is needed. NDV-HXP-S is an inactivated egg-based recombinant Newcastle disease virus vaccine expressing the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A public sector manufacturer in Vietnam assessed the immunogenicity of NDV-HXP-S (COVIVAC) relative to an authorized vaccine. Methods This phase 2 stage of a randomised, observer-blind, controlled, phase 1/2 trial was conducted at three community health centers in Thai Binh Province, Vietnam. Healthy males and non-pregnant females, 18 years of age and older, were eligible. Participants were randomised by age (18-59, ≥60 years) to receive one of three treatments by intramuscular injection twice, 28 days apart: COVIVAC at 3 µg or 6 µg, or AstraZeneca COVID-19 vaccine VAXZEVRIA. Participants and personnel assessing outcomes were masked to treatment. The main outcome was the induction of 50% neutralising antibody titers against vaccine-homologous pseudotyped virus 14 days (day 43) and 6 months (day 197) after the second vaccination by age group. The primary immunogenicity and safety analyses included all participants who received one dose of the vaccine. ClinicalTrials.gov NCT05940194 . Findings During August 10-23, 2021, 737 individuals were screened, and 374 were randomised (124-125 per group); all received dose one, and three missed dose two. On day 43, the geometric mean fold rise of 50% neutralising antibody titers for subjects age 18-59 years was 31·20 (COVIVAC 3 μg N=82, 95% CI 25·14-38·74), 35·80 (COVIVAC 6 μg; N=83, 95% CI 29·03-44·15), 18·85 (VAXZEVRIA; N=82, 95% CI 15·10-23·54), and for subjects age ≥60 years was 37·27 (COVIVAC 3 μg; N=42, 95% CI 27·43-50·63), 50·10 (COVIVAC 6 μg; N=40, 95% CI 35·46-70·76), 16·11 (VAXZEVRIA; N=40, 95% CI 11·73-22·13). Among subjects seronegative for anti-S IgG at baseline, the day 43 geometric mean titer ratio of neutralising antibody (COVIVC 6 μg/VAXZEVRIA) was 1·77 (95% CI 1·30-2·40) for subjects age 18-59 years and 3·24 (95% CI 1·98-5·32) for subjects age ≥60 years. On day 197, the age-specific ratios were 1·11 (95% CI 0·51-2·43) and 2·32 (0·69-7·85). Vaccines were well tolerated; reactogenicity was predominantly mild and transient. The percentage of subjects with unsolicited adverse events (AEs) during 28 days after vaccinations was similar among treatments (COVIVAC 3 μg 29·0%, COVIVAC 6 μg 23·2%, VAXZEVRIA 31·2%); no vaccine-related AE was reported. Interpretation Considering that induction of neutralising antibodies against SARS-CoV-2 has been correlated with the efficacy of COVID-19 vaccines, including VAXZEVRIA, our results suggest that vaccination with COVIVAC may afford clinical benefit matching or exceeding that of the VAXZEVRIA vaccine. Funding Vietnam’s Institute of Vaccines and Medical Biologicals (including support from Vietnam’s national COVID-19 vaccine fund and a charitable contribution from the Thien Tam fund of Vin group), Coalition for Epidemic Preparedness Innovations, a charitable contribution from Bayer AG, US National Institutes of Health.
