Highly pathogenic avian influenza A H5N1 viruses caused outbreaks of disease in domestic poultry and humans in Hong Kong in 1997. Direct transmission of the H5N1 viruses from birds to humans resulted in 18 documented cases of respiratory illness, including six deaths. Here we evaluated two of the avian H5N1 viruses isolated from humans for their ability to replicate and cause disease in outbred ferrets. A/Hong Kong/483/97 virus was isolated from a fatal case and was highly pathogenic in the BALB/c mouse model, whereas A/Hong Kong/486/97 virus was isolated from a case with mild illness and exhibited a low-pathogenicity phenotype in mice. Ferrets infected intranasally with 10 7 50% egg infectious doses (EID 50 ) of either H5N1 virus exhibited severe lethargy, fever, weight loss, transient lymphopenia, and replication in the upper and lower respiratory tract, as well as multiple systemic organs, including the brain. Gastrointestinal symptoms were seen in some animals. In contrast, weight loss and severe lethargy were not noted in ferrets infected with 10 7 EID 50 of two recent human H3N2 viruses, although these viruses were also isolated from the brains, but not other extrapulmonary organs, of infected animals. The results demonstrate that both H5N1 viruses were highly virulent in the outbred ferret model, unlike the differential pathogenicity documented in inbred BALB/c mice. We propose the ferret as an alternative model system for the study of these highly pathogenic avian viruses.

Two different severe acute respiratory syndrome (SARS) vaccine strategies were evaluated for their ability to protect against live SARS coronavirus (CoV) challenge in a murine model of infection. A whole killed (inactivated by b-propiolactone) SARS-CoV vaccine and a combination of two adenovirus-based vectors, one expressing the nucleocapsid (N) and the other expressing the spike (S) protein (collectively designated Ad S/N), were evaluated for the induction of serum neutralizing antibodies and cellular immune responses and their ability to protect against pulmonary SARS-CoV replication. The whole killed virus (WKV) vaccine given subcutaneously to 129S6/SvEv mice was more effective than the Ad S/N vaccine administered either intranasally or intramuscularly in inhibiting SARS-CoV replication in the murine respiratory tract. This protective ability of the WKV vaccine correlated with the induction of high serum neutralizing-antibody titres, but not with cellular immune responses as measured by gamma interferon secretion by mouse splenocytes. Titres of serum neutralizing antibodies induced by the Ad S/N vaccine administered intranasally or intramuscularly were significantly lower than those induced by the WKV vaccine. However, Ad S/N administered intranasally, but not intramuscularly, significantly limited SARS-CoV replication in the lungs. Among the vaccine groups, SARS-CoV-specific IgA was found only in the sera of mice immunized intranasally with Ad S/N, suggesting that mucosal immunity may play a role in protection for the intranasal Ad S/N delivery system. Finally, the sera of vaccinated mice contained antibodies to S, further suggesting a role for this protein in conferring protective immunity against SARS-CoV infection. (Marra et al., 2003;Rota et al., 2003) and by experimental infection of macaques to fulfil Koch's postulates . 0008-1579 G 2006 SGM Printed in Great BritainCurrently, there is no effective treatment for SARS. Prevention through contact-reduction or transmission-blocking measures has been the only means available to modify the devastating impact of this illness. Prevention through vaccination would be an attractive alternative that is less reliant on individual case detection to be effective. No vaccines are currently licensed for any of the human CoVs, but effective vaccines have been produced for some animal CoVs, such as certain strains of Infectious bronchitis virus (poultry), Bovine coronavirus and Canine coronavirus (Cavanagh, 2003;Enjuanes et al., 1995;Pratelli et al., 2003;Saif, 2004;Takamura et al., 2002). Individuals convalescing from SARS develop high titres of neutralizing antibodies (Tan et al., 2004) and the appearance of antibodies coincides with the onset of resolution of SARS pneumonia Woo et al., 2004). Thus, there is some optimism that an effective vaccine against SARS-CoV may also be possible.Coronavirus spike (S) proteins have long been known to be a major determinant in coronavirus pathogenesis, given that this viral protein interacts with cellular receptors as well as con...

Conjugative transposon Tn916 from Enterococcus faecalis DS16 encodes tetracycline resistance (Tet M) as well as determinants necessary for its own movement. Determination of the nucleotide sequence of Tn916 has been completed. The element is 18,032 bp in length and has an overall G+C content of 38.8%. Twenty-four potential open reading frames (ORFs) were identified based on sequence analysis. Similarities of the ORFs to other known determinants, which were revealed by database searches, are discussed.

Although the 2003 severe acute respiratory syndrome (SARS) outbreak was controlled, repeated transmission of SARS coronavirus (CoV) over several years makes the development of a SARS vaccine desirable. We performed a comparative evaluation of two SARS vaccines for their ability to protect against live SARS-CoV intranasal challenge in ferrets. Both the whole killed SARS-CoV vaccine (with and without alum) and adenovirus-based vectors encoding the nucleocapsid (N) and spike (S) protein induced neutralizing antibody responses and reduced viral replication and shedding in the upper respiratory tract and progression of virus to the lower respiratory tract. The vaccines also diminished haemorrhage in the thymus and reduced the severity and extent of pneumonia and damage to lung epithelium. However, despite high neutralizing antibody titres, protection was incomplete for all vaccine preparations and administration routes. Our data suggest that a combination of vaccine strategies may be required for effective protection from this pathogen. The ferret may be a good model for SARS-CoV infection because it is the only model that replicates the fever seen in human patients, as well as replicating other SARS disease features including infection by the respiratory route, clinical signs, viral replication in upper and lower respiratory tract and lung damage. INTRODUCTIONSevere acute respiratory syndrome (SARS) caused 8098 reported cases and 774 deaths in 26 countries (WHO, 2004a) in a single autumn-to-spring period from 2002 to 2003, and had significant effects on the global economy. Serological evidence suggests zoonotic transmission of SARS coronavirus (CoV) into the human population for several years before this outbreak (Zheng et al., 2004); transmission to humans has continued, resulting in at least four independent non-laboratory associated cases in (Che et al., 2006Fleck, 2004; Guan et al., 2005; WHO, 2004b). The aetiological agent of SARS has been identified as a novel human CoV by sequencing of its genome (Marra et al., 2003;Rota et al., 2003) and by experimental infection of macaques to fulfil Koch's postulates (Fouchier et al., 2003). It is of particular concern as a zoonosis because it can replicate in a large number of animals including cats, pigs, ferrets, foxes, monkeys and rats (Chen et al., 2005; et al., 1996;Olsen, 1993). Although antibodies to CoV N proteins have no virus-neutralizing activity, there is evidence that the protein may provide protection in vivo by induction of cell-mediated immunity, although it has also been suggested to induce eosinophilic infiltrates resulting in immunopathology (Deming et al., 2006;Enjuanes et al., 1995; Stohlman et al., 1995;Wesseling et al., 1993). N protein has been shown to generate CoV-specific CD8 + T cells (Boots et al., 1991;Seo et al., 1997; Stohlman et al., 1993 Stohlman et al., , 1995; it also provides protection in animals in response to infection by animal CoV (Collisson et al., 2000;Seo et al., 1997). In addition, vaccination with SARS N protein decre...