Growth of H5N1 Influenza A Viruses in the Upper Respiratory Tracts of Mice

Highly pathogenic avian H5N1 influenza A viruses have spread throughout Asia, Europe, and Africa, raising serious worldwide concern about their pandemic potential. Although more than 250 people have been infected with these viruses, with a consequent high rate of mortality, the molecular mechanisms responsible for the efficient transmission of H5N1 viruses among humans remain elusive. We used a mouse model to examine the role of the amino acid at position 627 of the PB2 viral protein in efficient replication of H5N1 viruses in the mammalian respiratory tract. Viruses possessing Lys at position 627 of PB2 replicated efficiently in lungs and nasal turbinates, as well as in cells, even at the lower temperature of 33 °C. Those viruses possessing Glu at this position replicated less well in nasal turbinates than in lungs, and less well in cells at the lower temperature. These results suggest that Lys at PB2–627 confers to avian H5N1 viruses the advantage of efficient growth in the upper and lower respiratory tracts of mammals. Therefore, efficient viral growth in the upper respiratory tract may provide a platform for the adaptation of avian H5N1 influenza viruses to humans and for efficient person-to-person virus transmission, in the context of changes in other viral properties including specificity for human (sialic acid α-2,6-galactose containing) receptors

The Effect of Olive Leaf Extract on Hepatic Fat Accumulation in Sprague-Dawley Rats Fed a High-fat Diet

Oleuropein, the active constituent of olive leaf extract, possesses anti-oxidant, hypoglycemic, and hypolipidemic activities. We aimed to assess whether the effect of olive leaf extract on hepatic fat accumulation is preventive or therapeutic. Sprague-Dawley (SD) rats were fed a high-fat diet with (ODOD group) or without (HDHD group) olive leaf extract (1,000 mg/kg diet) for 38 weeks. Another group of rats were fed a high-fat diet for 23 weeks, followed by a high-fat diet with olive leaf extract (1,000 mg/kg diet) for 15 weeks (HDOD group). Serology, histopathology, anti-oxidative activity, and liver fatty acid synthesis were compared to those fed a standard diet (LDLD group) at 26 and 41 weeks of age. The serum levels of total cholesterol, triglyceride and aspartate aminotransferase tended to be lower in the ODOD group as compared to the HDHD and HDOD groups, although there were no significant differences. Histopathologically, hepatic steatosis tended to be less evident in the HDOD and ODOD groups as compared to the HDHD group, and lobular inflammation was not observed in the ODOD group at 26 weeks of age. Hepatic thioredoxin-1 staining tended to be less evident in the ODOD group than in the HDHD and HDOD groups at 41 weeks of age. There were no significant differences in hepatic lipogenic enzyme activities between the ODOD group and HDHD/HDOD groups. Our data suggest that olive leaf extract had a preventive, rather than therapeutic, effect on hepatic steatohepatitis in SD rats fed a high-fat diet

Viral Replication Rate Regulates Clinical Outcome and CD8 T Cell Responses during Highly Pathogenic H5N1 Influenza Virus Infection in Mice

Since the first recorded infection of humans with H5N1 viruses of avian origin in 1997, sporadic human infections continue to occur with a staggering mortality rate of >60%. Although sustained human-to-human transmission has not occurred yet, there is a growing concern that these H5N1 viruses might acquire this trait and raise the specter of a pandemic. Despite progress in deciphering viral determinants of pathogenicity, we still lack crucial information on virus/immune system interactions pertaining to severe disease and high mortality associated with human H5N1 influenza virus infections. Using two human isolates of H5N1 viruses that differ in their pathogenicity in mice, we have defined mechanistic links among the rate of viral replication, mortality, CD8 T cell responses, and immunopathology. The extreme pathogenicity of H5N1 viruses was directly linked to the ability of the virus to replicate rapidly, and swiftly attain high steady-state titers in the lungs within 48 hours after infection. The remarkably high replication rate of the highly pathogenic H5N1 virus did not prevent the induction of IFN-β or activation of CD8 T cells, but the CD8 T cell response was ineffective in controlling viral replication in the lungs and CD8 T cell deficiency did not affect viral titers or mortality. Additionally, BIM deficiency ameliorated lung pathology and inhibited T cell apoptosis without affecting survival of mice. Therefore, rapidly replicating, highly lethal H5N1 viruses could simply outpace and overwhelm the adaptive immune responses, and kill the host by direct cytopathic effects. However, therapeutic suppression of early viral replication and the associated enhancement of CD8 T cell responses improved the survival of mice following a lethal H5N1 infection. These findings suggest that suppression of early H5N1 virus replication is key to the programming of an effective host response, which has implications in treatment of this infection in humans

Live Bivalent Vaccine for Parainfluenza and Influenza Virus Infections

Influenza and human parainfluenza virus infections are of both medical and economical importance. Currently, inactivated vaccines provide suboptimal protection against influenza, and vaccines for human parainfluenza virus infection are not available, underscoring the need for new vaccines against these respiratory diseases. Furthermore, to reduce the burden of vaccination, the development of multivalent vaccines is highly desirable. Thus, to devise a single vaccine that would elicit immune responses against both influenza and parainfluenza viruses, we used reverse genetics to generate an influenza A virus that possesses the coding region for the hemagglutinin/neuraminidase ectodomain of parainfluenza virus instead of the influenza virus neuraminidase. The recombinant virus grew efficiently in eggs but was attenuated in mice. When intranasally immunized with the recombinant vaccine, all mice developed antibodies against both influenza and parainfluenza viruses and survived an otherwise lethal challenge with either of these viruses. This live bivalent vaccine has obvious advantages over combination vaccines, and its method of generation could, in principle, be applied in the development of a “cocktail” vaccine with efficacy against several different infectious diseases