A Next-Generation Adenoviral Vaccine Elicits Mucosal and Systemic Immunogenicity and Reduces Viral Shedding after SARS-CoV-2 Challenge in Nonhuman Primates

As new SARS-CoV-2 variants continue to emerge and impact communities worldwide, next-generation vaccines that enhance protective mucosal immunity may have a significant impact on productive infection and transmission. We have developed recombinant non-replicating adenovirus serotype 5 (rAd5) vaccines delivered by mucosal administration that express both target antigen and a novel molecular adjuvant within the same cell. Here, we describe the immunogenicity of three unique SARS-CoV-2 rAd5 vaccine candidates and their efficacy following viral challenge in non-human primates (NHPs). Intranasal immunization with rAd5 vaccines expressing Wuhan, or Beta variant spike alone, or Wuhan spike and nucleocapsid elicited strong antigen-specific serum IgG and IgA with neutralizing activity against multiple variants of concern (VOC). Robust cross-reactive mucosal IgA was detected after a single administration of rAd5, which showed strong neutralizing activity against multiple VOC. Additionally, mucosal rAd5 vaccination increased spike-specific IFN-γ producing circulating T-cells. Upon Beta variant SARS-CoV-2 challenge, all the vaccinated NHPs exhibited significant reductions in viral load and infectious particle shedding in both the nasal passages and lower airways. These findings demonstrate that mucosal rAd5 immunization is highly immunogenic, confers protective cross-reactive antibody responses in the circulation and mucosa, and reduces viral load and shedding after SARS-CoV-2 challenge.

1960. Mucosal rAd5 Immunization against SARS-CoV-2 Spike Elicits Cross-Reactive Nasal and Serum Neutralizing Antibodies and Protects Against Beta Variant Challenge in African Green Monkeys

Background

Mucosal vaccination may offer increased protection against SARS-CoV-2 compared to parental immunization. Here, we describe immunogenicity and efficacy following viral challenge in non-human primates after intranasal delivery of three unique non-replicating adenoviral vector vaccine (rAd5) candidates.

Methods

African green monkeys (AMG) were prime boost immunized 29 days apart with vaccine candidates either expressing the parental spike protein alone (Wuhan-S), spike plus nucleocapsid (Wuhan-S-N), or the spike protein from the beta variant (beta-S). Serum and nasal swabs were collected every 14 days and humoral responses to full length spike (S) and receptor binding domain (RBD) were assessed. All AMGs were challenged with SARS-CoV-2 B.1.351 (beta variant) on day 56. Viral loads measured every two days by TCID₅₀ in nasal washes and bronchial lavage fluid post challenge.

Results

Mucosal immunization with Wuhan-S induced significant increases in serum IgG and IgA responses against the homologous parental lineage, as well as beta, delta, and omicron variants. In nasal samples, Wuhan-S immunization elicited over 500-fold increases in in cross-reactive IgA against multiple variants of concern including delta and omicron. While the beta-S rAd5 vaccine candidate induced enhanced serum IgG responses to homologous S and RBD proteins, this approach resulted in less cross-reactive antibodies to other variants compared to Wuhan-S rAd5 vaccine. Despite the differences in the ability to elicit cross-reactive antibody responses, all vaccinated AMGs challenged with SARS-CoV-2 B.1.351 (beta variant), had a significant reduction in viral titers by TCID₅₀ in the nasal passages and reduced viral load in bronchial lavage fluid compared to unvaccinated controls.

Conclusion

These results demonstrate mucosal administration of rAd5 clinical candidate vaccine, Wuhan-S, is immunogenic and offers cross-protective humoral responses in both serum and nasal compartments against a mismatched SARS-CoV-2 challenge virus.

Disclosures

Becca A. Flitter, PhD, MPH, Vaxart Inc: Stocks/Bonds Sarah N. Tedjakusuma, n/a, Vaxart Inc: Stocks/Bonds Colin A. Lester, n/a, Vaxart Inc: Stocks/Bonds Elena D. Neuhaus, n/a, Vaxart Inc: Stocks/Bonds Susan Johnson, PhD, Vaxart Inc: Stocks/Bonds Emery G. Dora, n/a, Vaxart Inc: Stocks/Bonds Nadine Peinovich, MPH, Vaxart Inc: Stocks/Bonds Clara B. Jegede, n/a, Vaxart Inc: Stocks/Bonds Sean N. Tucker, PhD, Vaxart Inc: Stocks/Bonds.

Hyaluronan synthesis inhibition impairs antigen presentation and delays transplantation rejection

A coat of pericellular hyaluronan surrounds mature dendritic cells (DC) and contributes to cell-cell interactions. We asked whether 4-methylumbelliferone (4MU), an oral inhibitor of HA synthesis, could inhibit antigen presentation. We find that 4MU treatment reduces pericellular hyaluronan, destabilizes interactions between DC and T-cells, and prevents T-cell proliferation in vitro and in vivo. These effects were observed only when 4MU was added prior to initial antigen presentation but not later, consistent with 4MU-mediated inhibition of de novo antigenic responses. Building on these findings, we find that 4MU delays rejection of allogeneic pancreatic islet transplant and allogeneic cardiac transplants in mice and suppresses allogeneic T-cell activation in human mixed lymphocyte reactions. We conclude that 4MU, an approved drug, may have benefit as an adjunctive agent to delay transplantation rejection.

Lay CPR trainees: retraining, confidence and willingness to attempt resuscitation 4 years after training

Two independent samples of 800 lay CPR trainees from an original cohort of 7584 were surveyed postally 4 years after training. Only 2% of respondents had used CPR, but 92 had used other aspects of their life support training. Those who had retrained were more confident than those who had not and 89% of those who had not retrained were willing to do so. More than 80% expressed willingness to perform full CPR on casualties who were unknown to them, but this fell to 40% where facial blood was present and 48% where the victim was a gay man.

Evaluating CPR performance in basic life support: the VIDRAP protocol

This paper presents the second part of the validated Cardiff test for one rescuer basic life support skills, based on observation of video recording combined with the Recording Resusci Anne printout (VIDRAP). The authors believe that this is a robust evaluation tool which is capable of assessing the potential value to a casualty of a simulated resuscitation. The adoption of a widely accepted test methodology would facilitate comparison of research in different centres, which is not possible at present.

Assessing with CARE: an innovative method of testing the approach and casualty assessment components of basic life support, using video recording

The resuscitation community is now moving towards a set of basic life support guidelines but different countries and training centres have their own individual methods of instruction. It would be advantageous if a universal testing method were available to facilitate intercentre comparison. This could lead to an international course which had been rigorously assessed and evaluated. Taking this as a starting point, the Cardiff Assessment of Response and Evaluation (CARE) was developed. CARE is an innovative assessment technique using video recording for testing the preliminary steps of life support as outlined by the European Resuscitation Council. The assessment was validated by testing 67 members of the public who had been trained in cardiopulmonary resuscitation, 27 shortly after instruction and 40 between 6 and 18 months after instruction. All subjects were tested without prior warning and video recorded for independent scoring by two researchers and a paramedic training officer. Scores were compared using the k correlation which showed a high level of agreement between observers. Video recording and marking using the CARE schedule and guidelines is a reliable method for assessing the preliminary steps in life support.

Effectiveness of the BBC's 999 training roadshows on cardiopulmonary resuscitation: video performance of cohort of unforewarned participants at home six months afterwards

OBJECTIVE

To examine the competence of a cohort trained in cardiopulmonary resuscitation by the BBC's 999 training roadshows.

DESIGN

Descriptive cohort study applying an innovative testing procedure to a nationwide systematic sample. The test sample received an unsolicited home visit and without warning were required to perform cardiopulmonary resuscitation on a manikin while being videoed. The videos were then analysed for effectiveness and safety using the new test.

SETTING

Nine cities and surrounding areas in the United Kingdom.

SUBJECTS

280 people aged between 11 and 72.

RESULTS

Thirty three (12%) trainees were able to perform effective cardiopulmonary resuscitation, but of these 14 (5%) performed one or more elements in a way that was deemed to be potentially injurious. Thus only 19 (7%) trainees were able at six months to provide safe cardiopulmonary resuscitation. In addition, large numbers of subjects failed to shout for help, effectively assess the status of the patient, or alert an ambulance. Significantly better performances were recorded by those under 45 years old (31 (14%) v 2 (4%) gave effective performances respectively, P < 0.05), those who had attended a subsequent cardiopulmonary resuscitation course (8 (40%) v 25 (10%) gave effective performances respectively, P < 0.0001), and those confident in their initial ability (26 (20%) v 7 (6%) gave effective performances respectively, P < 0.005). Females were significantly less likely than males to perform procedures in a harmful way (117 (62%) v 10 (12%) performed safely respectively, P < 0.005).

CONCLUSION

Television is an effective means of generating large training cohorts. Volunteers will cooperate with unsolicited testing in their home, such testing being a realistic simulation of the stress and lack of forewarning that would surround a real event. Under such conditions the performance of cardiopulmonary resuscitation was disappointing. However, retraining greatly improves performance.

The need for wider dissemination of CPR skills: are schools the answer?

The value of instructing members of the public in CPR is now widely recognised, but community training schemes which rely largely on volunteers may fail to reach their targets. CPR training for lay people is often a once only activity and it has been shown that, without revision, skills deteriorate rapidly. By teaching CPR in secondary schools all social classes and ethnic groups could be reached, and retention of skills improved by regular revision. Health education has shown that it may be beneficial to use older pupils as instruction assistants.

Monitoring performance in the NHS. The district neural tube defect screening service

A small medical school team has developed a six item system (SIS) for monitoring the neural tube defect (NTD) screening service. SIS is discussed in relation to possible alternative monitoring systems and the advantages which led to its implementation are described. In July 1982 the system was introduced in three districts in South Wales and the first year's results are presented. These permit the local provision, written policies and clinical and management responsibility of the service to be examined and deficiencies in the relevant information systems to be identified. Of particular concern is the discovery that districts have no way of knowing the number of terminations for NTD, and thus their current NTD incidence. In view of these findings, it would seem advisable for all districts providing NTD screening to monitor their service. SIS provides a simple, cheap and effective monitoring system which could be easily implemented throughout England and Wales.