Intranasal ChAdOx1 nCoV-19/AZD1222 vaccination reduces viral shedding after SARS-CoV-2 D614G challenge in preclinical models

Abstract

ChAdOx1 nCoV-19/AZD1222 is an approved adenovirus-based vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) currently being deployed globally. Previous studies in rhesus macaques revealed that intramuscular vaccination with ChAdOx1 nCoV-19/AZD1222 provided protection against pneumonia but did not reduce shedding of SARS-CoV-2 from the upper respiratory tract. Here, we investigated whether intranasally administered ChAdOx1 nCoV-19 reduces detection of virus in nasal swabs after challenging vaccinated macaques and hamsters with SARS-CoV-2 carrying a D614G mutation in the spike protein. Viral loads in swabs obtained from intranasally vaccinated hamsters were decreased compared to control hamsters, and no viral RNA or infectious virus was found in lung tissue after a direct challenge or after direct contact with infected hamsters. Intranasal vaccination of rhesus macaques resulted in reduced virus concentrations in nasal swabs and a reduction in viral loads in bronchoalveolar lavage and lower respiratory tract tissue. Intranasal vaccination with ChAdOx1 nCoV-19/AZD1222 reduced virus concentrations in nasal swabs in two different SARS-CoV-2 animal models, warranting further investigation as a potential vaccination route for COVID-19 vaccines.

Fig. 1.. IN ChAdOx1 nCoV-19 vaccination protects Syrian hamsters from SARS-CoV-2 infection.

Hamsters (n = 10 per group) were vaccinated via the IN route (purple), IM route (blue), or with control (C) vaccine ChAdOx1 GFP via the IM route (green). (A) Binding antibody titers against SARS-CoV-2 S protein in serum are shown for day 28 after vaccination. (B) VN antibody titers in serum are shown for day 28 after vaccination. For (A) and (B), the geometric mean and 95% confidence interval are shown. Dotted line, limit of detection. (C) Relative weight was measured as a percent of starting weight at indicated days postinoculation (DPI) with SARS-CoV-2. #P < 0.05 between IN and control group; *P < 0.05 between vaccinated groups and control group. Geometric mean and 95% confidence interval are shown. (D) Viral load and viral titer in oropharyngeal swabs are shown as geometric mean (symbols) and 95% confidence interval (shade). *P < 0.05, **P < 0.01, and ***P < 0.001 relative to controls at the same time point. Dotted line, limit of detection. (E) Area under the curve (AUC) analysis is shown for viral load and titer detection in oropharyngeal swabs over 7 days postinoculation. (F) Viral load and titer in lung tissue isolated at 5 DPI are shown. For (E) and (F), the dashed line within the violin plots indicate median; dotted lines within the violin plot indicate quartiles. Statistical analyses are done using mixed-effect analyses (C), two-way ANOVA (D), or Kruskal-Wallis test (E and F).

Fig. 2.. Lung pathology is reduced in ChAdOx1 nCoV-19 IN-vaccinated Syrian hamsters after direct IN challenge with SARS-CoV-2.

(A) Hematoxylin and eosin (H&E)–stained lung sections from control hamsters 5 days after SARS-CoV-2 infection reveals moderate to marked interstitial pneumonia. (B and C) H&E-stained sections of lungs isolated from IN-vaccinated (B) or IM-vaccinated (C) hamsters reveal no pathology after infection. (D) Numerous immunoreactive (brown) bronchiolar epithelial cells and types I and II pneumocytes are observed in control hamsters. (E and F) No immunoreactivity is present in sections of lungs isolated from IN-vaccinated (E) or IM-vaccinated (F) hamsters. Scale bars, 50 μm.

Fig. 3.. IN ChAdOx1 nCoV-19 vaccination protects Syrian hamsters from SARS-CoV-2 infection by transmission.

Hamsters (n = 14 per group) were vaccinated via the IN route (purple), IM route (blue), or with control (C) vaccine ChAdOx1 GFP via the IM route (green). (A) Hamsters received a single vaccination 28 days before exposure. Donor animals were challenged at −1 days postexposure (DPE), and hamsters were cohoused for 4 hours, 1 day later. (B) Binding antibody titers against SARS-CoV-2 S protein in serum are shown for day 28 after vaccination. ns, not significant. (C) VN antibody titers in serum are shown for day 28 after vaccination. For (B) and (C), the geometric mean and 95% confidence interval are shown. Dotted line, limit of detection. (D) Relative weight was measured as a percent of starting weight at indicated DPE with SARS-CoV-2. #P < 0.05 between IN and control group; *P < 0.05 between vaccinated groups and control group. Geometric mean and 95% confidence interval are shown. (E) Viral load and viral titers in oropharyngeal swabs are shown as geometric mean (symbols) and 95% confidence interval (shade). **P < 0.01, and ***P < 0.001, relative to controls at the same time point. Dotted line, limit of detection. (F) AUC analysis is shown for viral load and titer detection in oropharyngeal swabs over 7 DPE. (G) Viral load and titer in lung tissue isolated at 5 DPI are shown. For (F) and (G), the dashed line within the violin plots indicate median; dotted lines within the violin plot indicate quartiles. Statistical analyses done using mixed-effect analyses (D), two-way ANOVA (E), or Kruskal-Wallis test (F and G).

Fig. 4.. Lung pathology is reduced in ChAdOx1 nCoV-19 IN-vaccinated Syrian hamsters cohoused with SARS-CoV-2 infected hamsters.

(A) H&E-stained lung sections from control hamsters 5 days after SARS-CoV-2 infection reveal moderate to marked interstitial pneumonia. (B) H&E-stained sections of lungs isolated from IN-vaccinated hamsters reveal no pathology after infection. (C) H&E-stained sections of lungs isolated from IM-vaccinated hamsters reveal mild interstitial pneumonia after infection. (D) Numerous immunoreactive (brown) bronchiolar epithelial cells and types I and II pneumocytes are observed in control hamsters. (E) No immunoreactivity is present in sections of lungs isolated from IN-vaccinated. (F) Scattered immunoreactive bronchiolar epithelial cells and types I and II pneumocytes are observed in IM-vaccinated hamsters. Scale bars, 50 μm.

Fig. 5.. IN vaccination with ChAdOx1 nCoV-19 in rhesus macaques induces humoral and cellular immune responses.

(A to C) Truncated violin plot of SARS-CoV-2–specific IgG antibodies measured in serum (A), nasosorption samples (B), and BAL (C) shows evidence of S- and RBD-specific IgG in all three tissues at the indicated days postprime vaccination (DPV) in animals receiving IN ChAdOx1 nCoV-19 (blue, n = 4) but no serum IgG in control animals (purple, n = 4). (D to F) Truncated violin plot of SARS-CoV-2–specific IgA antibodies measured in serum (D), nasosorption samples (E), and BAL (F) shows induction of IgA at all three sites in IN-vaccinated animals. (G) Truncated violin plot of neutralizing antibodies in serum is shown compared to convalescent sera (C, black) from individuals with COVID-19. The red triangle indicates NIBSC serum control 20/130. (H) Truncated violin plot of effector functions of antibodies in serum are shown. Antibody-dependent NK cell activation (ADNKA) is shown based on expression of CD107a, IFN-γ, and MIP-1β. ADCP, antibody-dependent cellular phagocytosis; ADCD, antibody-dependent complement deposition. (I) Truncated violin plots of S protein–specific T cell responses in PBMCs isolated from vaccinated or controls animals at −14 DPI minus −56 DPI response. SFU, spot-forming units. Black lines indicate median; dotted lines indicate quartiles. Blue indicates vaccinated animals and purple indicates control animals (only 56 DPV values are shown).

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

(A) gRNA, sgRNA, and infectious virus concentrations were measured in nasal swabs at indicated days postinoculation (DPI). (B) AUC was calculated as an indication of the total amount of virus shed in nasal swabs. (C) gRNA, sgRNA, and infectious virus concentrations were measured in BAL. (D) AUC was calculated as an indication of the total amount of virus shed in BAL. (E and F) Amount of gRNA and sgRNA in nasal turbinates (E) and lung tissue (F) is shown. For all panels, blue indicates vaccinated animals and purple indicates control animals. For (A) and (C), dotted lines indicate individual animals and solid lines indicate geometric mean; shaded areas indicate 95% confidence intervals. For (B) and (D) to (F), solid lines indicate median and dotted lines indicate quartiles. *P < 0.05, ***P < 0.001, and ****P < 0.0001, as determined by two-tailed Mann-Whitney test.

Fig. 7.. Lung pathology is reduced in ChAdOx1 nCoV-19 IN-vaccinated rhesus macaques after SARS-CoV-2 challenge.

(A and B) Lung tissue sections isolated from IN-vaccinated (A) and control (B) rhesus macaques were stained with H&E. Scale bars, 200 μm. (A) Interstitial pneumonia (arrowhead) and lymphocytic perivascular cuffing (arrows) were observed in control samples. (B) No pathology was observed in IN-vaccinated lung samples. (C and D) Immunohistochemistry for SARS-CoV-2 antigen (brown) reveals rare type I pneumocyte immunoreactivity (arrow) in control samples (C) but no immunoreactivity in IN-vaccinated samples (D). Scale bars, 20 μm.

Fig. 8.. Vaccine-induced humoral responses influence viral RNA titers after SARS-CoV-2 challenge.

(A) Principal components analysis (PCA) plot of the multivariate antibody profile across all animals (numbered dots) is shown. Ellipses indicate group distribution as 95% confidence interval. Mapped arrow projections indicate the influence of individual variables on the principal components (PCs); the plot depicts only the top seven contributors. (B) The complete antibody variable loading plots for PC1 and PC2 are shown with a dotted line to indicate average expected contribution. (C) PCA plot of the multivariate AUC virology profile across all animals (numbered dots) is shown. Ellipses indicate group distribution as 95% confidence interval. Mapped arrow projections indicate the influence of individual variables on the PCs. (D) The complete virology variable loading plots for PCs 1 and 2 are shown with a dotted line to indicate average expected contribution. (E) A heatmap visualization is shown of the correlations between antibody measures and viral RNA (AUC) titers for the IN-vaccinated animals. R values were generated using two-sided Spearman rank correlation tests. Naso, nasosorption samples; VN, virus neutralization titer.