Detection of chikungunya virus antigen by a novel rapid immunochromatographic test.

Chikungunya fever is a mosquito-borne disease of key public health importance in tropical and subtropical countries. Although severe joint pain is the most distinguishing feature of chikungunya fever, diagnosis remains difficult because the symptoms of chikungunya fever are shared by many pathogens, including dengue fever. The present study aimed to develop a new immunochromatographic diagnosis test for the detection of chikungunya virus antigen in serum. Mice were immunized with isolates from patients with Thai chikungunya fever, East/Central/South African genotype, to produce mouse monoclonal antibodies against chikungunya virus. Using these monoclonal antibodies, a new diagnostic test was developed and evaluated for the detection of chikungunya virus. The newly developed diagnostic test reacted with not only the East/Central/South African genotype but also with the Asian and West African genotypes of chikungunya virus. Testing of sera from patients suspected to have chikungunya fever in Thailand (n = 50), Laos (n = 54), Indonesia (n = 2), and Senegal (n = 6) revealed sensitivity, specificity, and real-time PCR (RT-PCR) agreement values of 89.4%, 94.4%, and 91.1%, respectively. In our study using serial samples, a new diagnostic test showed high agreement with the RT-PCR within the first 5 days after onset. A rapid diagnostic test was developed using mouse monoclonal antibodies that react with chikungunya virus envelope proteins. The diagnostic accuracy of our test is clinically acceptable for chikungunya fever in the acute phase.

Temporal Change of SARS-CoV-2 in Clinical Specimens of COVID-19 Pneumonia Patients.

The quality and type of specimen collection affect the sensitivity of real-time reverse transcriptase-PCR (rRT-PCR) for the diagnosis of SARS-CoV-2. In this report, the course over time of rRT-PCR for SARS-CoV-2 in 26 clinical specimens collected from the upper (nasopharyngeal and throat swabs) and lower (sputum) respiratory tracts of COVID-19 cases with pneumonia was investigated along with the clinical course. The preliminary results revealed that higher SARS-CoV-2 RNA concentration and longer time for detection make self-collected sputum a preferable specimen for the diagnosis and follow-up of COVID-19 pneumonia. Self-collection of sputum can minimize the risk of unnecessary exposure to healthcare workers, preserve the shortage of personal protective equipment, and limit viral transmission to the environment.

PirAB toxin from Photorhabdus asymbiotica as a larvicide against dengue vectors.

We have evaluated Photorhabdus insect-related protein (Pir) from Photorhabdus asymbiotica against dengue vectors. PirAB shows larvicidal activity against both Aedes aegypti and Aedes albopictus larvae but did not affect the Mesocyclops thermocyclopoides predator. PirAB expressed the strongest toxicity compared to PirA, PirB, or the mixture of PirA plus PirB. Whether the presence of an enterobacterial repetitive intergenic consensus sequence in PirAB, but not in PirA, PirB, or the mixture of PirA plus PirB, has any impact on biological control efficacy needs further investigation.

Dengue virus infection-enhancing antibody activities against Indonesian strains in inhabitants of central Thailand.

Dengue virus (DENV) infection-enhancing antibodies are a hypothetic factor to increase the dengue disease severity. In this study, we investigated the enhancing antibodies against Indonesian strains of DENV-1-4 in 50 healthy inhabitants of central Thailand (Bangkok and Uthai Thani). Indonesia and Thailand have seen the highest dengue incidence in Southeast Asia. The infection history of each subject was estimated by comparing his/her neutralizing antibody titers against prototype DENV-1-4 strains. To resolve the difficulty in obtaining foreign live viruses for use as assay antigens, we used a recombinant system to prepare single-round infectious dengue viral particles based on viral sequence information. Irrespective of the previously infecting serotype(s), most serum samples showed significantly higher enhancement titers against Indonesian DENV-2 strains than against Thai DENV-2 strains, whereas the opposite effect was observed for the DENV-3 strains. Equivalent enhancing activities were observed against both DENV-1 and DENV-4. These results suggest that the genotype has an impact on enhancing antibody activities against DENV-2 and DENV-3, because the predominant circulating genotypes of each serotype differ between Indonesia and Thailand.