Initiation of primary cell cultures from embryonic Haemaphysalis bispinosa ticks

Abstract

Tick cell cultures have been widely used as an important tool for the study of tick-associated microorganisms, specifically for medically important bacteria or viruses that may be difficult to isolate or culture in axenic conditions. In this study, primary embryonic tick cell cultures were initiated separately from each of the egg batches laid by 10 female ticks belonging to the hard tick genus Haemaphysalis. All cultures were maintained at 28°C. After 10 months, 4 healthy cultures were identified with the potential for developing into continuous tick cell lines. These cultures comprise large cells predominantly forming floating cell clumps with multicellular vesicles, which are morphologically similar to cell lines derived from the soft tick Ornithodoros moubata. Subculture has not yet been performed due to the low cell density at the time of writing. Amplification and sequencing of a fragment of the 16S rRNA gene from DNA extracted from the parent ticks showed 99%-100% similarity to published sequences of Haemaphysalis bispinosa. This is the first report of the initiation of embryonic cell cultures from Haemaphysalis ticks found in Malaysia. Such tick cell cultures will be useful for studies of tick-borne pathogens in this region, where recent studies have shown that Haemaphysalis ticks are highly represented and harbor medically important bacteria.