Intranasal ChAdOx1 nCoV-19/AZD1222 vaccination reduces shedding of SARS-CoV-2 D614G in rhesus macaques

Abstract

Intramuscular vaccination with ChAdOx1 nCoV-19/AZD1222 protected rhesus macaques against pneumonia but did not reduce shedding of SARS-CoV-2. Here we investigate whether intranasally administered ChAdOx1 nCoV-19 reduces shedding, using a SARS-CoV-2 virus with the D614G mutation in the spike protein. Viral load in swabs obtained from intranasally vaccinated hamsters was significantly decreased compared to controls and no viral RNA or infectious virus was found in lung tissue, both in a direct challenge and a transmission model. Intranasal vaccination of rhesus macaques resulted in reduced shedding and a reduction in viral load in bronchoalveolar lavage and lower respiratory tract tissue. In conclusion, intranasal vaccination reduced shedding in two different SARS-CoV-2 animal models, justifying further investigation as a potential vaccination route for COVID-19 vaccines.

Figure 1.. SARS-CoV-2 challenge of Syrian hamsters vaccinated with ChAdOx1 nCoV-19.

Hamsters were vaccinated via the IN route (red), IM route (blue) or with control vaccine ChAdOx1 GFP via the IM route (green). A. Binding antibody titers against SARS-CoV-2 S protein. B. Virus neutralizing antibody titers. C. Relative weight upon challenge with SARS-CoV-2. A-B. Shown is geometric mean and 95% confidence interval. # = p-value <0.05 between IN and control group; * = p-value <0.05 between vaccinated groups and control group. D. Viral load and viral titer in oropharyngeal swabs. Shown is geometric mean (symbols) and 95% confidence interval (shade). E. Area under the curve analysis of viral load and titer shedding in oropharyngeal swabs. F. Viral load and titer in lung tissue, isolated at 5 DPI. E-F. Dashed line = median; dotted line = quartiles. Statistical analyses done using mixed-effect analyses (C), two-way ANOVA (D), or Kruskal-Wallis test (E-F). * = p value <0.05; ** = p-value < 0.01; *** = p-value < 0.001.

Figure 2.. Pulmonary effects of direct intranasal challenge with SARS-CoV-2 in Syrian hamsters.

A-C. H&E; D-F. IHC. A/B. No pathology. C. Moderate to marked interstitial pneumonia. D/E. No immunoreactivity. F. Numerous immunoreactive bronchiolar epithelial cells and Type I&II pneumocytes. Bar = 50μm.

Figure 3.. SARS-CoV-2 transmission to Syrian hamsters vaccinated with ChAdOx1 nCoV-19.

Hamsters were vaccinated via the IN route (red), IM route (blue) or with control vaccine ChAdOx1 GFP via the IM route (green). A. Experimental schedule. Hamsters received a single vaccination 28 days prior to exposure. Donor animals were challenged at −1 DPE, and hamsters were co-housed for 4 hours. one day later. B. Binding antibody titers against SARS-CoV-2 S protein. C. Virus neutralizing antibody titers. D. Relative weight upon challenge with SARS-CoV-2. Shown is geometric mean and 95% confidence interval. # = p-value <0.05 between IN and control group; * = p-value <0.05 between vaccinated groups and control group. E. Viral load and viral titer in oropharyngeal swabs. Shown is geometric mean (symbols) and 95% confidence interval (shade). F. Area under the curve analysis of viral load and titer shedding in oropharyngeal swabs. G. Viral load and titer in lung tissue, isolated at 5 DPE. F-G. Dashed line = median; dotted line = quartiles. Statistical analyses done using mixed-effect analyses (C), two-way ANOVA (D), or Kruskal-Wallis test (E-F). * = p value <0.05; ** = p-value < 0.01; *** = p-value < 0.001.

Figure 4.. Pulmonary effects of transmission of SARS-CoV-2 in Syrian hamsters.

A-C. H&E; D-F. IHC. A. No pathology. B. Mild interstitial pneumonia. C. Moderate to marked interstitial pneumonia. D. No immunoreactivity. E. Scattered immunoreactive bronchiolar epithelial cells and Type I&II pneumocytes. F. Numerous immunoreactive bronchiolar epithelial cells and Type I&II pneumocytes. Bar = 50μm

Figure 5.. Humoral response to IN vaccination with ChAdOx1 nCoV-19 in rhesus macaques.

Truncated violin plot of SARS-CoV-2-specific IgG antibodies measured in serum (A), nasosorption samples (B), and BAL (C). Truncated violin plot of SARS-CoV-2-specific IgA antibodies measured in serum (D), nasosorption samples (E), and BAL (F). G. Truncated violin plot of neutralizing antibodies in serum. H. Effector functions of antibodies in serum. Black line = median; dotted line = quartiles; blue = vaccinated animals; purple = control animals (only 0 DPI values shown); black = human convalescent sera; red = NIBSC serum control 20/130. I. Anti-RBD-specific IgG titers at 0 DPI. Orange = RBD wildtype; aqua = RBD N501Y.

Figure 6.. SARS-CoV-2 detection in samples obtained from rhesus macaques upon virus challenge.

gRNA, sgRNA and infectious virus in nasal swabs (A) and BAL (C) was determined. Dotted line = individual animals; solid line = geometric mean; shaded area = 95% confidence interval. Area under the curve (AUC) was calculated as an indication of the total amount of virus shed in nasal swabs (B) and BAL (D) and displayed as a truncated violin plot. Solid line = median; dotted line = quartiles. * = p-value <0.05 as determined via two-tailed Mann-Whitney test. Amount of gRNA and sgRNA in nasal turbinate (E) and lung tissue (F). Blue = vaccinated animals; purple = control animals; solid line = median; dotted line = quartiles. *** = p-value <0.001; **** = p-value <0.0001, as determined via two-tailed Mann-Whitney test.

Figure 7.. Influence of the vaccine-induced humoral response on viral RNA levels post challenge.

Principal component analysis (PCA) plot of the multivariate antibody (A) and AUC virology (C) profile across all animals (numbered dots). Ellipses indicate group distribution as 95% confidence levels. Mapped arrow projections indicate the influence of individual variables on the PCs; the antibody plot depicts only the top seven contributors. The complete antibody (B) and virology (D) variable loading plots for PCs 1 and 2 with a dotted line to indicate average expected contribution. Heatmap visualization of the correlations between antibody measures and viral RNA (AUC) levels (E) for the IN-vaccinated animals; R values were generated using two-sided Spearman rank correlation tests.