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Melioidosis, an infection with the bacterium Burkholderia pseudomallei, is highly endemic in the Top End of the Northern Territory of Australia. The indirect haemagglutination assay (IHA) is the most widely used serology test globally, but it is not standardised among the limited number of laboratories that perform it. While concerns have been raised about the sensitivity of IHA early in melioidosis infections, the advantage of IHA over more recently developed ELISAs is that testing serial dilutions allows a titre to be recorded. While in Australia a titre of 1:40 or higher is considered positive, the specificity at these low positive titres remains uncertain. However, a high titre is considered to represent recent or past true infection with B. pseudomallei, rather than cross-rection with other environmental Burkholderia species. Also, the natural history of IHA titres over time, in both asymptomatic infection and melioidosis has been little studied. We have assessed the clinical status and serology time courses of all 534 patients who had an IHA titre of 1:640 or higher, over a 20-year period. Of these, 324 (60.7%) were diagnosed with culture-confirmed melioidosis, with varying time courses of diagnosis of melioidosis in relation to the high serology. Of the 210 without confirmed melioidosis, 22 (10.5%) were considered highly likely to be melioidosis despite being culture-negative, and these were all treated as melioidosis. In the remainder, titres mostly gradually decreased over time, but the majority remained seropositive. A small number who had not been treated for melioidosis continued to have high IHA titres over years and activation from latency with a new diagnosis of melioidosis was occasionally documented. This study highlights the importance of a full clinical workup in those found to have high titre melioidosis serology as well as subsequent close clinical surveillance and where resources allow, yearly IHA in those not confirmed or treated as melioidosis. Full article

Schistosomiasis is a neglected tropical disease despite of being a major public health problem affecting nearly 240 million people in the world. Due to the migratory flow from endemic countries to Western countries, an increasing number of cases is being diagnosed in non-endemic areas, generally in migrants or people visiting these areas. Serology is the recommended method for screening and diagnosis of schistosomiasis in migrants from endemic regions. However, serological techniques have a highly variable sensitivity. The aim of this study was to evaluate retrospectively the sensitivity of three different serological tests used in real clinical practice for the screening and diagnosis of imported schistosomiasis in sub-Saharan migrant patients, using the detection of schistosome eggs in urine, faeces or tissues as the gold standard. We evaluated three different serological techniques in 405 sub-Saharan patients with confirmed schistosomiasis treated between 2004 and 2022: an enzyme-linked immunosorbent assay (ELISA), an indirect haemagglutination assay (IHA) and an immunochromatographic test (ICT). The overall sensitivity values obtained with the different techniques were: 44.4% for IHA, 71.2% for ELISA and 94.7% for ICT, respectively. According to species, ICT showed the highest sensitivity (S. haematobium: 94%, S. mansoni: 93.3%; and S. intercalatum/guineensis: 100%). In conclusion, our study shows that Schistosoma ICT has the best performance in real clinical practice, when compared to ELISA and IHA, in both S. mansoni and S. haematobium infections. Full article

Developing new vaccine candidates is considered the best strategy for protecting poultry against artificial haemagglutinin (A/H5N1) strains. The transient expression system in plants has been a very efficient method for rapidly producing haemagglutinin-based recombinant vaccines. In this study, two novel artificial trimeric haemagglutinin constructs representing A/H5N1 strains that were detected in poultry from 2005 to 2015 in Vietnam, H5.c1 (representing all of the subclades 1.1, 1.1.1, and 1.1.2) and H5.c2 (representing all of the subclades 2.3.2.1, 2.3.2.1a, 2.3.2.1b, and 2.3.2.1c), were designed for transient expression in Nicotiana benthamiana via agroinfiltration. However, only the H5.c1 protein, which showed the best expression and biofunction via the haemagglutination test, was selected for purification by immobilized metal ion affinity chromatography (IMAC). The trimeric structure of the IMAC-purified H5.c1 protein was well characterized by cross-linking reaction and size exclusion chromatography. An indirect ELISA and Western blot analysis of vaccinated mouse sera demonstrated that the H5.c1 protein strongly induced HA-specific Immunoglobulin G (IgG) immune responses. Notably, the H5.c1 protein induced strongly neutralizing antibodies against homologous H5.c1 protein and that of three heterologous native strains of clade, 1, 1.1, and 2.3.2.1c, in haemagglutination inhibition assays. Therefore, the plant-based artificial H5.c1 protein can be a promising vaccine candidate for conferring poultry resistance against A/H5N1 viruses in Vietnam. Full article