Virology
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Angiotensin converting enzyme 2 (ACE2) is the receptor that severe acute respiratory syndrome coronavirus (SARS-CoV) utilizes for target cell entry and, therefore, plays an important role in SARS pathogenesis. Since Chinese rhesus (rh) macaques do not usually develop SARS after SARS-CoV infection, it has been suggested that rh-ACE2 probably does not support viral entry efficiently. To determine the role of rh-ACE2 in early lung pathogenesis in vivo, we studied eleven Chinese rhesus monkeys experimentally infected with a pathogenic SARS-CoV(PUMC01) strain. ⋯ Moreover, introduction of the Y217N mutation into hu-ACE2 caused the down-regulation of expression and reduced viral entry efficiency. These results indicate that the Y217N mutation plays a role in modulating SARS-CoV infection. Our results provide insights for understanding the role of rh-ACE2 in SARS lung pathogenesis in a non-human primate model.
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Several small animal models have been developed for the study of severe acute respiratory syndrome coronavirus (SARS-CoV) replication and pathogenesis. Syrian golden hamsters are among the best small animal models, though little clinical illness and no mortality are observed after virus infection. ⋯ Infection with recombinant SARS-CoV viruses bearing disruptions in the gene 7 coding region showed no significant change in replication kinetics, tissue tropism, morbidity, or mortality suggesting that the ORF7a (7a) and ORF7b (7b) proteins are not required for virus replication in immunosuppressed hamsters. This modified hamster model may provide a useful tool for SARS-CoV pathogenesis studies, evaluation of antiviral therapy, and analysis of additional SARS-CoV mutants.
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The increasing number of recent outbreaks of HPAI H5N1 in birds and humans brings out an urgent need to develop potent H5N1 vaccine regimens. Here we present a study on the intranasal vaccination of recombinant baculovirus surface-displayed hemagglutinin (BacHA) or inactivated whole H5N1 viral (IWV) vaccine with a recombinant cholera toxin B subunit (rCTB) as a mucosal adjuvant in a BALB/c mouse model. Two groups of mice were vaccinated with different doses (HA titer of log 2(4) or log 2(8)) of either HA surface-displayed baculovirus or inactivated whole viral vaccine virus adjuvanted with different doses (2 mug or 10 mug) of rCTB. ⋯ The host challenge study also showed that 10 mug rCTB combined with log 2(8) HA titer of BacHA provided 100% protection against 10MLD(50) of homologous and heterologous H5N1 strains. The study shows that the combination of rH5 HA expressed on baculovirus surface and rCTB mucosal adjuvant form an effective mucosal vaccine against H5N1 infection. This baculovirus surface-displayed vaccine is more efficacious than inactivated H5N1 influenza vaccine when administered by intranasal route and has no biosafety concerns associated with isolation, purification and production of the latter vaccine.
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Ebola virus (EBOV) causes outbreaks of a highly lethal hemorrhagic fever in humans. The virus can be transmitted by direct contact as well as by aerosol and is considered a potential bioweapon. Because direct immunization of the respiratory tract should be particularly effective against infection of mucosal surfaces, we previously developed an intranasal vaccine based on replication-competent human parainfluenza virus type 3 (HPIV3) expressing EBOV glycoprotein GP (HPIV3/EboGP) and showed that it is immunogenic and protective against a high dose parenteral EBOV challenge. ⋯ This restriction appeared to be based on both neutralizing antibodies and cellular or other components of the immunity to HPIV3. Surprisingly, even though replication of HPIV3/EboGP was highly restricted in HPIV3-immune animals, it induced a high level of EBOV-specific antibodies that nearly equaled that obtained in HPIV3-naive animals. We also show that the previously demonstrated presence of functional GP in the vector particle was not associated with increased replication in the respiratory tract nor with spread beyond the respiratory tract of HPIV3-naive guinea pigs, indicating that expression and functional incorporation of the attachment/penetration glycoprotein of this systemic virus did not mediate a change in tissue tropism.
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This study evaluated the use of a chimpanzee-based adenovirus vaccine in mouse and Guinea pigs models of Zaire Ebola virus (ZEBOV) infection. Vaccine vector expressing the envelope glycoprotein of ZEBOV was created from the molecular clone of chimpanzee adenovirus pan7 (AdC7). AdC7 vaccine stimulated robust T and B cell responses to ZEBOV in naïve mice inducing complete protection to an otherwise lethal challenge of ZEBOV. ⋯ Pre-existing immunity to AdHu5 was generated in mice following pre-exposure to AdHu5 or administration of pooled human immune globulin. Pre-existing immunity to human adenoviruses severely compromised the efficacy of the human AdHu5 vaccine but not the chimpanzee AdC7 vaccine. These results validate further development of Chimpanzee-based vaccine and highlight the impact of pre-existing immunity to the vaccine carrier.