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.     

MicroRNA‐361‐3p is a potent therapeutic target for oral squamous cell carcinoma

MicroRNAs (miRNAs) can act not only as tumor suppressor genes but also as oncogenes. Oncogenic miRNAs (oncomiRs) could therefore provide opportunities for the treatment of human malignancies. Here, we aimed to identify oncomiRs present in oral squamous cell carcinoma (OSCC) and addressed whether targeting these miRNAs might be useful in treatment for cancer. Functional screening for oncomiRs in a human OSCC cell line (GFP‐SAS) was carried out using the miRCURY LNA microRNA Knockdown Library – Human version 12.0. We identified a locked nucleic acid (LNA)/DNA antisense oligonucleotide against miR‐361‐3p (LNA‐miR‐361‐3p) which showed the largest degree of growth inhibition of GFP‐SAS cells. Transfection with a synthetic mimic of mature miR‐361‐3p resulted in an approximately 20% increase in the growth of GFP‐SAS cells. We identified odd‐skipped related 2 (OSR2) as a miR‐361‐3p target gene. Transfection of GFP‐SAS cells with LNA‐miR‐361‐3p caused a significant increase in the expression levels of OSR2. Cotransfection of a OSR2 3′‐UTR luciferase reporter plasmid and LNA‐miR‐361‐3p into GFP‐SAS cells produced higher levels of luciferase activity than in cells cotransfected with the LNA‐nontarget. We assessed the effect of LNA‐miR‐361‐3p on the in vivo growth of GFP‐SAS cells. We found that LNA‐miR‐361‐3p significantly reduced the size of s.c. xenografted GFP‐SAS tumors, compared to the control group treated with LNA‐NT. Finally, we observed that miR‐361‐3p is overexpressed in OSCC tissues. These results suggest that miR‐361‐3p supports the growth of human OSCC cells both in vitro and in vivo and that targeting miR‐361‐3p could be a useful therapeutic approach for patients with OSCC.     

Durability of humoral immune responses to rubella following MMR vaccination

BackgroundWhile administration of the measles-mumps-rubella (MMR-II®) vaccine has been effective at preventing rubella infection in the United States, the durability of humoral immunity to the rubella component of MMR vaccine has not been widely studied among older adolescents and adults.MethodsIn this longitudinal study, we sought to assess the durability of rubella virus (RV)-specific humoral immunity in a healthy population (n = 98) of adolescents and young adults at two timepoints: ~7 and ~17 years after two doses of MMR-II® vaccination. Levels of circulating antibodies specific to RV were measured by ELISA and an immune-colorimetric neutralization assay. RV-specific memory B cell responses were also measured by ELISpot.ResultsRubella-specific IgG antibody titers, neutralizing antibody titers, and memory B cell responses declined with increasing time since vaccination; however, these decreases were relatively moderate. Memory B cell responses exhibited a greater decline in men compared to women.ConclusionsCollectively, rubella-specific humoral immunity declines following vaccination, although subjects’ antibody titers remain well above the currently recognized threshold for protective immunity. Clinical correlates of protection based on neutralizing antibody titer and memory B cell ELISpot response should be defined.     

Humoral and cellular immune response induced by rVSVΔG-ZEBOV-GP vaccine among frontline workers during the 2013–2016 West Africa Ebola outbreak in Guinea

BackgroundAs part of a Phase III trial with the Ebola vaccine rVSVΔG-ZEBOV-GP in Guinea, we invited frontline workers (FLWs) to participate in a sub-study to provide additional information on the immunogenicity of the vaccine.MethodsWe conducted an open‐label, non‐randomized, single-arm immunogenicity evaluation of one dose of rVSVΔG-ZEBOV-GP among healthy FLWs in Guinea. FLWs who refused vaccination were offered to participate as a control group. We followed participants for 84 days with a subset followed-up for 180 days. The primary endpoint was immune response, as measured by ELISA for ZEBOV-glycoprotein–specific antibodies (ELISA-GP) at 28 days. We also conducted neutralization, whole virion ELISA and enzyme-linked immunospot (ELISPOT) assay for cellular response.ResultsA total of 1172 participants received one dose of vaccine and were followed-up for 84 days, among them 114 participants were followed-up for 180 days. Additionally, 99 participants were included in the control group and followed up for 180 days. Overall, 86.4% (95% CI 84.1–88.4) of vaccinated participants seroresponded at 28 days post-vaccination (ELISA- GP) with 65% of these seroresponding at 14 days post-vaccination. Among those who seroresponded at 28 days, 90.7% (95% CI 82.0–95.4) were still seropositive at 180 days. The proportion of seropositivity in the unvaccinated group was 0.0% (95% CI 0.0–3.8) at 28 days and 5.4% (95% CI 2.1–13.1) at 180 days post-vaccination. We found weak correlation between ELISA-GP and neutralization at baseline but significant pairwise correlation at 28 days post-vaccination. Among samples analysed for cellular response, only 1 (2.2%) exhibited responses towards the Zaire Ebola glycoprotein (Ebola GP ≥ 10) at baseline, 10 (13.5%) at day 28 post-vaccination and 27 (48.2%) at Day 180.ConclusionsWe found one dose of rVSVΔG-ZEBOV-GP to be highly immunogenic at 28- and 180-days post vaccination among frontline workers in Guinea. We also found a cellular response that increased with time.     

Higher mass meningococcal group C-tetanus toxoid vaccines conjugated with carbodiimide correlate with greater immunogenicity

To examine the link between meningococcal C (MenC) vaccine size and immunogenic response, a panel of MenC glycoconjugate vaccines were prepared differing in chain length, molar mass and hydrodynamic volume. The preparations consisted of different lengths of MenC polysaccharide (PS) covalently linked to monomeric purified tetanus toxoid (TT) carrier protein using the coupling reagent ethylcarbodiimide hydrochloride (EDC). Size exclusion chromatography with multi-angle light scattering (SEC-MALS) and viscometry analysis confirmed that the panel of MenC-TT conjugates spanned masses of 191,500 to 2,348,000 g/mol, and hydrodynamic radii ranging from 12.1 to 47.9 nm. The two largest conjugates were elliptical in shape, whereas the two smallest conjugates were more spherical. The larger conjugates appeared to fit a model described by multiple TTs with cross-linked PS, typical of lattice-like networks described previously for TT conjugates, while the smaller conjugates were found to fit a monomeric or dimeric TT configuration. The effect of vaccine conjugate size on immune responses was determined using a two-dose murine immunization. The two larger panel vaccine conjugates produced higher anti-MenC IgG1 and IgG2b titres after the second dose. Larger vaccine conjugate size also stimulated greater T-cell proliferative responses in an in vitro recall assay, although cytokines indicative of a T-helper response were not measurable. In conclusion, larger MenC-TT conjugates up to 2,348,000 g/mol produced by EDC chemistry correlate with greater humoral and cellular murine immune responses. These observations suggest that conjugate size can be an important modulator of immune response.     

Interchangeability of two Enterovirus 71 inactivated vaccines in Chinese children: A phase IV,open-label,and randomized controlled trial

BackgroundIn China, three inactivated Enterovirus 71 (EV71) vaccines have been approved. Although the vaccines in an immunization series should be from a single manufacture, children sometimes have to receive EV71 vaccines from more than one manufacturers. The aim of this study was to evaluate the interchangeability and safety of vaccination with EV71 vaccines from two manufacturers among Chinese children.MethodsWe conducted an open label and randomized controlled study among children aged 6–35 months from November 2018 to January 2019. The participants were randomly assigned (1:1:1:1) to receive EV71 vaccines in one of the four different schedules (two using a single vaccine for all doses from one manufacture, and two mixed schedules using vaccines from two manufactures). Blood samples were collected pre-vaccination (Day 0) and one month after the second dose (Day 60) for neutralizing antibody assay. Immunogenicity was assessed in the per-protocol cohort and safety was assessed in the total vaccinated cohort.ResultsA total of 300 children were enrolled and randomized, of whom 89.0% (267/300) were included in the per-protocol cohort for immunogenicity analysis. The seroconversion rates of the EV71 neutralizing antibody in four groups ranged from 98.4% to 100.0%, and were not significantly different among the groups. Compared with other groups, geometric mean titer was higher in group D, in which the participants received Institute of Medical Biology Chinese Academy of Medical Sciences (CAMS) vaccine in the first dose and the Sinovac vaccine in the second dose. Safety profiles were similar among the four groups and no serious adverse events related to the vaccination were reported.ConclusionsInterchangeability of EV71 vaccines from two manufactures to complete an immunization series showed good immunogenicity and safety. The antibody response levels may vary by vaccination sequences of EV71 vaccines from the two manufacturers.Trial registration: ClinicalTrials.govNCT03873740.     

A single dose glycoprotein D-based subunit vaccine against pseudorabies virus infection

Pseudorabies Virus (PRV) is the causative agent of Pseudorabies (PR), also known as Aujeszky’s Disease, one of the most important infectious diseases in swine, resulting in huge economic losses to the swine industry globally. The emergence of mutant PRV strains after 2011 resulted in a sharp decrease in the efficacy of available commercial vaccines. To develop a more effective vaccine that can prevent the spread of PRV, glycoprotein B (gB), glycoprotein C (gC) and glycoprotein D (gD) from recent PRV isolates were expressed in a baculovirus system and their protective efficacy was tested in mice and piglets. Neutralizing antibody titers (NAs) in mice vaccinated with gB, gC and gD peaked at 28 days after immunization and then slowly declined. NAs in the mice immunized with gD were remarkably higher than other groups. After a lethal challenge of 5 LD₅₀ with mutant PRV-HNLH strain, the survival rates of gB and gD were 100% and 87.5% respectively, which was significantly higher than gC group (50%). Piglets vaccinated with the gD and gB + D vaccines developed the highest NAs 7 days post immunization. No piglets in these two groups exhibited clinical symptoms, high body temperature or virus shedding following challenge with 10^6.6 TCID₅₀ with the mutant PRV-HNLH strain. Histopathology and immunohistochemistry showed remarkably reduced pathological damage and viral loads in gD and gB + D groups. Furthermore, the duration of the NAs induced by gD vaccine could maintain as long as four months after a single dose. The current study indicates that a gD-based vaccine could be developed for the efficient control of PRV.