We determined the presence of neutralizing antibodies to Middle East respiratory syndrome coronavirus in persons in Qatar with and without dromedary contact. Antibodies were only detected in those with contact, suggesting dromedary exposure as a risk factor for infection. Findings also showed evidence for substantial underestimation of the infection in populations at risk in Qatar.

Background: The city of Doha in Qatar has a high density of feral cats and there is a high risk of toxoplasmosis for the resident human population. No data currently exist for the prevalence of infection with Toxoplasma gondii in the city.

Feline calicivirus (FCV) is responsible for an acute upper respiratory tract disease in cats. The FCV capsid protein is synthesized as a precursor (76 kDa) that is post-translationally processed into the mature 62 kDa capsid protein by removal of the N-terminal 124 amino acids. Our previous studies have also detected a 40 kDa protein, related to the FCV capsid protein, produced during infection. Here we demonstrate that cleavage of the FCV capsid protein, during infection of cells in culture, was prevented by caspase inhibitors. In addition, caspase-2, -3 and -7 were activated during FCV infection, as shown by pro-form processing, an increase in N-acetyl-Asp-Glu-Val-Asp-7-amido-4-trifluoromethylcoumarin cleavage activity and in situ poly(ADP-ribose) polymerase cleavage. Caspase activation coincided with the induction of apoptosis and capsid cleavage to the 40 kDa fragment. An in vitro cleavage assay, using recombinant human caspases and in vitroderived FCV capsid protein, revealed that caspase-2, and to a lesser extent caspase-6, cleaved the capsid protein to generate a 40 kDa fragment. Taken together, these results suggest that FCV triggers apoptosis within infected cells and that caspase-induced capsid cleavage occurs concomitantly with apoptosis. The possible role of capsid cleavage in the pathogenesis of FCV infection is discussed. INTRODUCTIONThe family Caliciviridae includes several significant pathogens of man and animals. Feline calicivirus (FCV) is a major cause of upper respiratory tract disease in cats. The genome is a single-stranded positive sense RNA of about 7?5 kb (Carter et al., 1992a). The genome is polyadenylated and covalently linked to a 15 kDa viral protein, termed VPg, at the 59 end and contains three open reading frames (ORF). ORF1 encodes the non-structural proteins, ORF2 encodes the capsid protein and ORF3 a small highly basic structural protein (reviewed in Clarke & Lambden, 1997). ORF2 and ORF3 are expressed from a single subgenomic mRNA (Herbert et al., 1996). Calicivirus particles contain a single capsid protein (58-76 kDa). The capsid of members of the vesivirus genus, such as FCV and San Miguel sea lion virus (SMSV), is formed initially as a larger precursor which is cleaved by the viral protease into the mature capsid protein (62 kDa in the case of FCV; Neill, 1992;Neill et al., 1991; Carter et al., 1992b; Sosnovstev et al., 1998). The mature FCV protein is created by removal of the N-terminal 124 amino acids from the precursor (Carter, 1989). The mature protein is incorporated into virions.A smaller form of the capsid protein (approx. 40 kDa by SDS-PAGE; called p40) has been observed during FCV infection in cell culture at late times post-infection (Carter et al., 1989). Similar truncated forms of the capsid protein have been reported in the late stages of rabbit haemorrhagic disease virus (RHDV) infection (reviewed in Carter & Cubbitt, 1998). In addition, cleaved soluble forms of the Norwalk virus (NLV) capsid protein have been associated with enteric infection in man (Hardy ...

Caliciviruses are important pathogens of man and animals; feline calicivirus (FCV) is responsible for an acute upper respiratory tract disease in cats. To date, little is known about the mechanism of cell damage induced by these viruses. We set out to determine if apoptosis played any role in cell death in FCV infection of cultured cells. We demonstrate that caspase-2, -3, and -7 were activated during FCV infection, as evidenced by pro-form processing and an increase in acetyl-Asp-Glu-Val-Asp-7-amido-4-trifluoromethylcoumarin cleavage activity, as well as cleavage of poly(ADP-ribose)polymerase. Caspase activation coincided with the condensation of chromatin. At about 8 h post infection we also detected cleavage of the FCV capsid protein; this was prevented by caspase inhibitors. Taken together these results suggest that FCV triggers apoptosis within infected cells and that caspases are involved in the cleavage of the capsid protein.