Therapeutic Effect of Duck Interferon-Alpha Against H5N1 Highly Pathogenic Avian Influenza Virus Infection in Peking Ducks.

The antiviral cytokine interferon-alpha (IFN-α) plays a critical role in the innate immune system. Previous studies have shown that recombinant chicken IFN-α inhibits avian influenza virus (AIV) replication in vivo; however, the antiviral effect of recombinant duck IFN-α (rDuIFN-α) on highly pathogenic AIV remains unknown. In this study, the duck IFN-α gene was cloned, expressed, and purified. The antiviral effects of the resulting rDuIFN-α were further evaluated in vitro and in vivo. Our results showed that rDuIFN-α inhibited the replication of vesicular stomatitis virus (VSV) and AIV in duck embryo fibroblasts in vitro, with antiviral activities against VSV and AIV of 2.1 × 105 and 4.1 × 105 U/mg, respectively. We next investigated the anti-H5N1 AIV effect of intramuscular injection of rDuIFN-α in vivo. rDuIFN-α reduced viral titers in the brains, lungs, and spleens of 2-day-old (2D) ducks compared with that in the virus-challenged control group, and pretreatment with rDuIFN-α reduced mortality from 60% to 10% in 2D ducks. Moreover, rDuIFN-α increased the expression of IFN-stimulated genes in the brains and spleens of 2D ducks. Our results demonstrate that rDuIFN-α blocks VSV and H5N1 influenza virus infection in vitro and exhibits antiviral effects against H5N1 influenza virus infection in 2D ducks.

14-Deoxy-11,12-didehydroandrographolide attenuates excessive inflammatory responses and protects mice lethally challenged with highly pathogenic A(H5N1) influenza viruses.

Traditional Chinese medicine (TCM) has been an excellent treasury for centuries' accumulation of clinical experiences, which deserves to be tapped for potential drugs and improved using modern scientific methods. 14-Deoxy-11,12-didehydroandrographolide (DAP), a major component of an important TCM named Andrographis paniculata, with non-toxic concentration of 1000 mg/kg/day, effectively reduced the mortality and weight loss of mice lethally challenged with A/chicken/Hubei/327/2004 (H5N1) or A/PR/8/34 (H1N1) influenza A viruses (IAV) when initiated at 4 h before infection, or A/duck/Hubei/XN/2007 (H5N1) when initiated at 4 h or 48 h before infection, or 4 h post-infection (pi). DAP (1000 or 500 mg/kg/day) also significantly diminished lung virus titres of infected mice when initiated at 4 h or 48 h before infection, or 4 h pi. In the infection of A/duck/Hubei/XN/2007 (H5N1), DAP (1000 mg/kg/day) treatment initiated at 48 h before infection gained the best efficacy that virus titres in lungs of mice in log10TCID50/mL reduced from 2.61 ± 0.14 on 3 days post-infection (dpi), 2.98 ± 0.17 on 5 dpi, 3.54 ± 0.19 on 7 dpi to 1.46 ± 0.14 on 3 dpi, 1.86 ± 0.18 on 5 dpi, 2.03 ± 0.21 on 7 dpi. Moreover, DAP obviously alleviated lung histopathology and also strongly inhibited proinflammatory cytokines/chemokines expression. The mRNA levels of TNF-α, IL-1ß, IL-6, CCL-2/MCP-1, IFN-α, IFN-ß, IFN-γ, MIP-1α, MIP-1ß in lungs of A/duck/Hubei/XN/2007 (H5N1)-infected mice and serum protein expression of TNF-α, IL-1ß, IL-6, CCL-2/MCP-1 and CXCL-10/IP-10 in mice infected with all the three strains of IAV were all significantly reduced by DAP. Results demonstrated that DAP could restrain both the host intense inflammatory responses and high viral load, which were considered to contribute to the pathogenesis of H5N1 virus and should be controlled together in a clinical setting. Considering the anti-inflammatory and anti-IAV activities of DAP, DAP may be a promising active component obtained from A. paniculata, which can be further investigated as a useful constitute of curative strategies in the future against IAV, the H5N1 strains in particular.

The NF-kappaB inhibitor SC75741 protects mice against highly pathogenic avian influenza A virus.

The appearance of pandemic H1N1 and highly pathogenic avian H5N1 viruses in humans as well as the emergence of seasonal H1N1 variants resistant against neuraminidase inhibitors highlight the urgent need for new and amply available antiviral drugs. We and others have demonstrated that influenza virus misuses the cellular IKK/NF-kappaB signaling pathway for efficient replication suggesting that this module may be a suitable target for antiviral intervention. Here, we show that the novel NF-kappaB inhibitor SC75741 significantly protects mice against infection with highly pathogenic avian influenza A viruses of the H5N1 and H7N7 subtypes. Treatment was efficient when SC75741 was given intravenously in a concentration of 5mg/kg/day. In addition, application of SC75741 via the intraperitoneal route resulted in a high bioavailability and was also efficient against influenza when given 15 mg/kg/day or 7.5 mg/kg/twice a day. Protection was achieved when SC75741 was given for seven consecutive days either prior to infection or as late as four days after infection. SC75741 treatment showed no adverse effects in the concentrations required to protect mice against influenza virus infection. Although more pre-clinical studies are needed SC75741 might be a promising candidate for a novel antiviral drug against influenza viruses that targets the host cell rather than the virus itself.

Effects of a nutrient mixture on infectious properties of the highly pathogenic strain of avian influenza virus A/H5N1.

Numerous outbreaks of avian influenza virus infection (A/H5N1) have occurred recently, infecting domestic birds, chicken and ducks. The possibility of the emergence of a new strain of influenza virus capable of causing a pandemic in humans is high and no vaccine effective against such a strain currently exists. A unique nutrient mixture (NM), containing lysine, proline, ascorbic acid, green tea extract, N-acetyl cysteine, selenium among other micro nutrients, has been shown to exert a wide range of biochemical and pharmacological effects, including an inhibitory effect on replication of influenza virus and HIV. This prompted us to investigate the potential anti-viral activity of a nutrient mixture (NM) and its components on avian influenza virus A/H5N1at viral dosages of 1.0, 0.1 and 0.01 TCID(50). Antiviral activity was studied in cultured cell lines PK, BHK-21, and Vero-E6. Virus lysing activity was determined by co-incubation of virus A/H5N1 with NM for 0-60 min, followed residual virulence titration in cultured SPEV or BHK-21 cells. NM demonstrated high antiviral activity evident even at prolonged periods after infection. NM antiviral properties were comparable to those of conventional drugs (amantadine and oseltamivir); however, NM had the advantage of affecting viral replication at the late stages of the infection process.

Limitations of current prophylaxis against influenza virus infection.

Avian influenza has been a source of worldwide concern since Hong Kong authorities detected the first outbreak in 1997. Mainly as a result of poultry-to-human transmission, more than 200 cases of infection in humans have been attributed to the A/H5, A/H7, and A/H9 viral subtypes, with a case fatality rate for A/H5N1 infections exceeding 50%. A mutant or reassortant virus capable of efficient human-to-human transmission can set off a pandemic. Increased attention to prophylaxis against viral infection has identified several potentially complementary approaches: nonpharmacologic measures (eg, travel restrictions), vaccination, chemotherapeutic agents, and herbal/natural products. All have significant limitations that point out the need for additional modalities. Herbal/natural products, particularly those based on green tea extract, offer promise as adjuncts or alternatives to current interventions and warrant further evaluation in well-controlled human trials.