Anti-Influenza Effect of Nanosilver in a Mouse Model

Abstract

The present study assesses copper metabolism of the host organism as a target of antiviral strategy, basing on the "virocell" concept. Silver nanoparticles (AgNPs) were used as a specific active agent because they reduce the level of holo-ceruloplasmin, the main extracellular cuproenzyme. The mouse model of influenza virus A infection was used with two doses: 1 LD₅₀ and 10 LD₅₀. Three treatment regimens were used: Scheme 1-mice were pretreated 4 days before infection and then every day during infection development; Scheme 2-mice were pretreated four days before infection and on the day of virus infection; Scheme 3-virus infection and AgNP treatment started simultaneously, and mice were injected with AgNPs until the end of the experiment. The mice treated by Scheme 1 demonstrated significantly lower mortality, the protection index reached 60-70% at the end of the experiment, and mean lifespan was prolonged. In addition, the treatment of the animals with AgNPs resulted in normalization of the weight dynamics. Despite the amelioration of the infection, AgNP treatment did not influence influenza virus replication. The possibility of using nanosilver as an effective indirectly-acting antiviral drug is discussed.

Keywords: ceruloplasmin; copper status; indirectly-acting antiviral drug; influenza; influenza virus replication; prophylaxis and treatment; silver nanoparticles.

Figure 1

Schedules of treatment of mice with silver nanoparticles (AgNPs). Red arrow—intraperitoneal administration of AgNPs. Blue arrow—inoculation of the virus.

Figure 2

Test groups of mice.

Figure 3

The percentage of lung area affected in mice inoculated with A/South Africa/3626/2013 (H1N1) pdm09 (SA).

Figure 4

The physical properties of fabricated AgNPs: UV/Vis spectrum (A) and transmission electron microscopy image (B).

Figure 5

Oxidase activity of blood serum of mice against the background of influenza infection. (A–C)—mice were treated with AgNPs according to Schemes 1–3, correspondingly. Abscissa, mice groups: 1—without treatment; 2—treatment with AgNPs for 4 days; 3—treatment with AgNPs for 7 days; 4—infected with 1 LD₅₀; 5—treatment with AgNPs + 1 LD₅₀; 6—infected with 10 LD₅₀; 7—treatment with AgNPs + 10 LD_50.

Figure 6

Protection of mice from lethal primary viral pneumonia by AgNPs. Mean weight loss ± SEM (p < 0.05) (A,C) and survival, % ± SE (p < 0.05) (B,D), were monitored daily for 14 days. Mice were inoculated intranasally with 1 LD₅₀ (A,B) or 10 LD₅₀ (C,D).

Figure 7

Virus replication in the lungs of mice on D3 post-infection with 10⁻², 10⁻¹, 1, and 10 LD₅₀ as measured by titration in chicken embryos (mean ± SD, p > 0.05). Mice were infected with the dose of (A) 10⁻² LD₅₀; (B) 10⁻¹ LD₅₀; (C) 1 LD₅₀; and (D) 10 LD₅₀; red circles—virus titer in lung tissue of control mice; blue circles—virus titer in lung tissue of mice treated by AgNPs according to Scheme 1; gray—the limit of virus detection (1.9 log₁₀ EID₅₀/mL/g).

Figure 8

Target-dependent types of anti-influenza virus compounds.