First report and characterization of Tenacibaculum maritimum isolates recovered from rainbow trout (Oncorhynchus mykiss) farmed in Chile.

The present study reports on the first isolation of Tenacibaculum maritimum in rainbow trout (Oncorhynchus mykiss) farmed in Chile. In March 2020, two cages raising rainbow trout (~250 g) in the Los Lagos Region suffered a disease outbreak. In total, 17,554 fish died (3.5%-4.8% accumulated mortality). Microbiological analysis of the diseased fish obtained two representative isolates (i.e. Tm-035 and Tm-036). These were obtained from the external gross skin lesions-typical of tenacibaculosis-of two fish. Phenotyping, PCR tests and sequencing of the 16S rRNA and housekeeping genes confirmed the isolates as T. maritimum. The pathogenic potential of Tm-035 was further assessed by bath challenging Atlantic salmon (Salmo salar), which killed 70 ± 15% of fish within 11 days. Dead fish presented the same external clinical signs as did the farmed rainbow trout specimens. This research further broadens the known host distribution of this pathogen. Furthermore, the virulence experiments demonstrated that T. maritimum does not have a specific host. Additional studies are needed to evaluate the risk of T. maritimum for the O. mykiss farming industry.

Yellow fever virus envelope protein expressed in insect cells is capable of syncytium formation in lepidopteran cells and could be used for immunodetection of YFV in human sera.

BACKGROUND: Yellow fever is an haemorrhagic disease caused by a virus that belongs to the genus Flavivirus (Flaviviridae family) and is transmitted by mosquitoes. Among the viral proteins, the envelope protein (E) is the most studied one, due to its high antigenic potencial. Baculovirus are one of the most popular and efficient eukaryotic expression system. In this study a recombinant baculovirus (vSynYFE) containing the envelope gene (env) of the 17D vaccine strain of yellow fever virus was constructed and the recombinant protein antigenicity was tested. RESULTS: Insect cells infected with vSynYFE showed syncytium formation, which is a cytopathic effect characteristic of flavivirus infection and expressed a polypeptide of around 54 kDa, which corresponds to the expected size of the recombinant E protein. Furthermore, the recombinant E protein expression was also confirmed by fluorescence microscopy of vSynYFE-infected insect cells. Total vSynYFE-infected insect extracts used as antigens detected the presence of antibodies for yellow fever virus in human sera derived from yellow fever-infected patients in an immunoassay and did not cross react with sera from dengue virus-infected patients. CONCLUSIONS: The E protein expressed by the recombinant baculovirus in insect cells is antigenically similar to the wild protein and it may be useful for different medical applications, from improved diagnosis of the disease to source of antigens for the development of a subunit vaccine.