Long-term storage stability of multiplex immunochromatographic assay strips for serologic monitoring of infectious diseases in laboratory rodents.

Serological monitoring of infectious diseases in laboratory rodents is vital for ensuring animal health. Therefore, we have previously developed a multiplex immunochromatographic assay (ICA) to detect antibodies against six pathogens as follows: mouse hepatitis virus, Sendai virus, and Clostridium piliforme (Tyzzer's disease) in mice, and Seoul type orthohantavirus, Sendai virus, and sialodacryoadenitis virus in rats. However, the preparation of these strips is time-consuming and labor-intensive. Therefore, this study aimed to determine the long-term storage conditions for the developed multiplex ICA strips. The multiplex ICA strips stored in the polyethylene zipper-sealed bags (poly_bags) at -30°C maintained detectable reactivity for all six targeted pathogens for 36 months, regardless of the presence or absence of desiccants, oxygen absorbers, or a vacuum state. However, when stored at 18-28°C (room temperature) and 4°C, the detectable reactivity of the multiplex ICA strips stored in poly_bags was reduced for some of the six targets pathogens at 18 months after storage. This reduction was not prevented by the storage with the desiccants and in the vacuum-sealed poly_bags (vacuum_bags). The oxygen absorber reduced detectability of the multiplex ICA strips. These results indicate that storing ICA strips in poly_bags at -30°C, which is a simple method, is able to maintain detectability long-term for the strips format and pathogen targets examined in this study.