Protective Effects of Astodrimer Sodium 1% Nasal Spray Formulation against SARS-CoV-2 Nasal Challenge in K18-hACE2 Mice

Abstract

Strategies to combat COVID-19 require multiple ways to protect vulnerable people from infection. SARS-CoV-2 is an airborne pathogen and the nasal cavity is a primary target of infection. The K18-hACE2 mouse model was used to investigate the anti-SARS-CoV-2 efficacy of astodrimer sodium formulated in a mucoadhesive nasal spray. Animals received astodrimer sodium 1% nasal spray or PBS intranasally, or intranasally and intratracheally, for 7 days, and they were infected intranasally with SARS-CoV-2 after the first product administration on Day 0. Another group was infected intranasally with SARS-CoV-2 that had been pre-incubated with astodrimer sodium 1% nasal spray or PBS for 60 min before the neutralisation of test product activity. Astodrimer sodium 1% significantly reduced the viral genome copies (>99.9%) and the infectious virus (~95%) in the lung and trachea vs. PBS. The pre-incubation of SARS-CoV-2 with astodrimer sodium 1% resulted in a significant reduction in the viral genome copies (>99.9%) and the infectious virus (>99%) in the lung and trachea, and the infectious virus was not detected in the brain or liver. Astodrimer sodium 1% resulted in a significant reduction of viral genome copies in nasal secretions vs. PBS on Day 7 post-infection. A reduction in the viral shedding from the nasal cavity may result in lower virus transmission rates. Viraemia was low or undetectable in animals treated with astodrimer sodium 1% or infected with treated virus, correlating with the lack of detectable viral replication in the liver. Similarly, low virus replication in the nasal cavity after treatment with astodrimer sodium 1% potentially protected the brain from infection. Astodrimer sodium 1% significantly reduced the pro-inflammatory cytokines IL-6, IL-1α, IL-1β, TNFα and TGFβ and the chemokine MCP-1 in the serum, lung and trachea vs. PBS. Astodrimer sodium 1% nasal spray blocked or reduced SARS-CoV-2 replication and its sequelae in K18-hACE2 mice. These data indicate a potential role for the product in preventing SARS-CoV-2 infection or for reducing the severity of COVID-19.

Keywords: COVID-19; SARS-CoV-2; SPL7013; animal model; antiviral; astodrimer; dendrimer; nasal.

Figure 1

A seven-day time course of viraemia in SARS-CoV-2 (USA-WA1/2020) infected K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation: (a) Groups 1.1 and 1.2, intranasal administration only; (b) Groups 2.1 and 2.2, intranasal and intratracheal administration. Viraemia was detected by a qRT-PCR for SARS-CoV-2. Points and error bars represent means ± SD.

Figure 2

A seven-day time course of viraemia in K18-hACE2 mice infected with SARS-CoV-2 (USA-WA1/2020) inoculum incubated with PBS or astodrimer sodium 1% nasal spray for 60 min prior to the neutralisation procedure—virucidal evaluation. Viraemia was detected by a qRT-PCR for SARS-CoV-2. Points and error bars represent means ± SD.

Figure 3

The number of SARS-CoV-2 (USA-WA1/2020) viral genome copies (qRT-PCR) on Day 7 per nasal swab from K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation: Group 1, intranasal administration only; Group 2, intranasal and intratracheal administration; and Group 3, virucidal evaluation. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent mean ± SEM. * p < 0.05, *** p < 0.001, paired t-tests.

Figure 4

The number of viral genome copies (qRT-PCR) per mg of lung, trachea, brain and liver tissue from SARS-CoV-2 (USA-WA1/2020) infected K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation: (a) Groups 1.1 and 1.2, intranasal administration only; (b) Groups 2.1 and 2.2, intranasal and intratracheal administration. Tissue collected on Day 7. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent means ± SEM. * p < 0.05, ** p < 0.01, *** p < 0.001, paired t-tests.

Figure 5

The amount of infectious virus (pfu) per mL of lung, trachea, brain and liver tissue homogenate from SARS-CoV-2 (USA-WA1/2020) infected K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation: (a) Groups 1.1 and 1.2, intranasal administration only; (b) Groups 2.1 and 2.2, intranasal and intratracheal administration. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent means ± SEM. * p < 0.05, ** p < 0.01, paired t-tests.

Figure 6

The amount of virus in the K18-hACE2 mice infected with SARS-CoV-2 (USA-WA1/2020) inoculum incubated with PBS (Group 3.1) or astodrimer sodium 1% nasal spray (Group 3.2) for 60 min prior to the neutralisation procedure—virucidal evaluation: (a) number of viral genome copies (qRT-PCR) per mg of lung, trachea, brain and liver tissue; (b) amount of infectious virus (pfu) per mL of lung, trachea, brain and liver tissue homogenate. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent means ± SEM. * p < 0.05, ** p < 0.01, *** p < 0.001, paired t-tests.

Figure 7

A seven-day time course of the amount of cytokine/chemokine (pg/mL) in the serum of SARS-CoV-2 (USA-WA1/2020) infected K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation via intranasal administration only (Groups 1.1 [PBS] and 1.2): (a) IL-6 (b) IL-1α (c) IL-1β (d) TNFα (e) TGFβ (f) MCP-1. Points and error bars represent means ± SD.

Figure 7

A seven-day time course of the amount of cytokine/chemokine (pg/mL) in the serum of SARS-CoV-2 (USA-WA1/2020) infected K18-hACE2 mice treated with PBS or astodrimer sodium 1% nasal spray formulation via intranasal administration only (Groups 1.1 [PBS] and 1.2): (a) IL-6 (b) IL-1α (c) IL-1β (d) TNFα (e) TGFβ (f) MCP-1. Points and error bars represent means ± SD.

Figure 8

The amount of cytokine/chemokine in the lung and trachea tissue homogenates from K18-hACE2 mice infected with SARS-CoV-2 (USA-WA1/2020) inoculum incubated with PBS (Group 3.1) or astodrimer sodium 1% nasal spray (Group 3.2) for 60 min prior to the neutralisation procedure—virucidal evaluation: (a) IL-6 (b) IL-1α (c) IL-1β (d) TNFα (e) TGFβ (f) MCP-1. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent means ± SEM. * p < 0.05, ** p < 0.01, *** p < 0.001, paired t-tests.

Figure 8

The amount of cytokine/chemokine in the lung and trachea tissue homogenates from K18-hACE2 mice infected with SARS-CoV-2 (USA-WA1/2020) inoculum incubated with PBS (Group 3.1) or astodrimer sodium 1% nasal spray (Group 3.2) for 60 min prior to the neutralisation procedure—virucidal evaluation: (a) IL-6 (b) IL-1α (c) IL-1β (d) TNFα (e) TGFβ (f) MCP-1. The first (grey) column of each matched data set is the group treated with PBS and the second (blue) column is the group treated with astodrimer sodium 1% nasal spray. Columns and error bars represent means ± SEM. * p < 0.05, ** p < 0.01, *** p < 0.001, paired t-tests.