AIM To test whether a simple animal, Caenorhabditis elegans(C. elegans), can be used as an alternative model to study the interaction between hepatitis B virus antigens(HBs Ag) and host factors. METHODS Three plasmids that were able to express the large, middle and small forms of HBs Ags(LHBs Ag, MHBs Ag, and SHBs Ag, respectively) driven by a ubiquitous promoter(fib-1) and three that were able to express SHBs Ag driven by different tissue-specific promoters were constructed and microinjected into worms. The brood size, egglaying rate, and gonad development of transgenic worms were analyzed using microscopy. Levels of m RNA related to endoplasmic reticulum stress, enpl-1, hsp-4, pdi-3 and xbp-1, were determined using reverse transcription polymerase reaction(RT-PCRs) in three lines of transgenic worms and dithiothreitol(DTT)-treated wild-type worms. RESULTS Severe defects in egg-laying, decreases in brood size, and gonad retardation were observed in transgenic worms expressing SHBs Ag whereas moderate defects were observed in transgenic worms expressing LHBs Ag and MHBs Ag. RT-PCR analysis revealed that enpl-1, hsp-4 and pdi-3 transcripts were significantly elevated in worms expressing LHBs Ag and MHBs Ag and in wild-type worms pretreated with DTT. By contrast, only pdi-3 was increased in worms expressing SHBs Ag. To further determine which tissue expressing SHBs Ag could induce gonad retardation, we substituted the fib-1 promoter with three tissue-specific promoters(myo-2 for the pharynx, est-1 for the intestines and mec-7 for the neurons) and generated corresponding transgenic animals. Moderate defective phenotypes were observed in worms expressing SHBs Ag in the pharynx and intestines but not in worms expressing SHBs Ag in the neurons, suggesting that the secreted SHBs Ag may trigger a cross-talk signal between the digestive track and the gonad resulting in defective phenotypes. CONCLUSION Ectopic expression of three forms of HBs Ag that causes recognizable phenotypes in transgenic worms suggests that C. elegans can be used as an alternative model for studying virus-host interactions because the resulting phenotype is easily detected through microscopy. AIM To test whether a simple animal, Caenorhabditis elegans (C. elegans), can be used as an alternative model to study the interaction between hepatitis B virus antigens (HBs Ag) and host factors. METHODS Three plasmids that were able to express the large , middle and small forms of HBs Ags (LHBs Ag, MHBs Ag, and SHBs Ag, respectively) driven by a ubiquitous promoter (fib-1) and three that were able to express SHBs Ag driven by different tissue-specific promoters were constructed and Microinjected into worms. The brood size, egglaying rate, and gonad development of transgenic worms were analyzed using microscopy. Levels of m RNA related to endoplasmic reticulum stress, enpl-1, hsp-4, pdi-3 and xbp- using reverse transcription polymerase reaction (RT-PCRs) in three lines of transgenic worms and dithiothreitol (DTT) -treated wild-type worms. RESULTS Severe defects in egg-laying, decreasing in brood size, and gonad retardation were observed in transgenic worms expressing SHBs Ag when moderate defects were observed in transgenic worms expressing LHBs Ag and MHBs Ag. RT-PCR analysis revealed that enpl-1, hsp-4 and pdi-3 transcripts were significantly elevated in worms expressing LHBs Ag and MHBs Ag and in wild-type worms By contrast, only pdi-3 was increased in worms expressing SHBs Ag could induce gonad retardation, we substituted the fib-1 promoter with three tissue-specific promoters (myo-2 for the pharynx, est-1 for the intestines and mec-7 for the neurons) and generated corresponding transgenic animals. Moderate defective phenotypes were observed in worms expressing SHBs Ag in the pharynx and intestines but not in worms expressing SHBs Ag in the neurons, suggesting that the secreted SHBs Ag may trigger a cross-talk signal between the digestive track and the gonad resulting in defective phenotypes. CONCLUSION Ectopic expression of three forms of HBs Ag that causes recognizable phenotypes in transgenic worms suggests that C. elegans can be used as an alternative model for studying virus-host interactions because the resulting phenotype is easily detected through microscopy.