Anti-DPP4 monoclonal antibody, clone M-A261

Hepatitis E virus (HEV) is a common cause of acute viral hepatitis worldwide. Most HEV infections are asymptomatic, but immunocompromised patients infected with HEV genotype 3 (HEV3), HEV4, or HEV7 may develop chronic infections. The HEV particles in stools are naked (nHEV), while those in the serum and culture supernatants (eHEV) are associated with lipids. Hepatocytes are polarized epithelial cells that have basolateral (oriented toward the blood) and apical (oriented toward the bile) exosomal pathways. We isolated a subclone, F2, from the human hepatocarcinoma cell line HepG2/C3A that grew as a polarized monolayer culture and had better HEV production than HepG2/C3A cells. F2 cells cultured on semipermeable collagen inserts and infected basolaterally with nHEV3 released 94.6% of virus particles apically, those infected with eHEV3 released 96.8% apically, and eHEV1-infected cells released 99.3% apically. Transcytosis was not involved. Density gradient centrifugation and NP-40 treatment showed that HEV particles released both apically and basolaterally were lipid associated. The apically released HEV3 and HEV1 particles were six and nine times more infectious than those released basolaterally, respectively. Confocal microscopy indicated that the open reading frame 2 (ORF2) capsid protein colocalized apically with ORF3 virus protein, the apical marker DPP4, and the recycling endosome GTPase Rab27a. The amounts of soluble glycosylated ORF2 secreted apically and basolaterally were similar. These polarized-hepatocyte data suggest that infectious HEV particles are mainly released into bile, while the small fraction released into blood could spread HEV throughout the host. IMPORTANCE Hepatitis E virus (HEV) in stools is naked, while that in culture supernatants and patients' blood is lipid associated. Its life cycle in hepatocytes, polarized cells with a basolateral side communicating with blood and an apical side connected with bile, is incompletely understood. We have developed a polarized hepatocyte model and used the cells to analyze the supernatants bathing the apical and basolateral sides and HEV subcellular distribution. HEV particles from both sides were lipid associated, and most infectious HEV particles left the cell via its apical side. Similar amounts of the open reading frame 2 (ORF2) soluble capsid protein were secreted from both sides of the hepatocytes. This model mimicking physiological conditions should help clarify the HEV cell cycle in polarized hepatocytes.

Bullous pemphigoid (BP) is an organ-specific autoantibody-mediated blistering skin disease that mainly affects the elderly. Typical clinical features include the widespread blisters, often preceded by and/or associated with itchy urticarial or eczema-like lesions. BP patients have circulating autoantibodies against BP180 and/or the plakin family protein BP230 both of which are components of hemidesmosomes in basal keratinocytes. Most BP autoantibodies particularly target the epitopes within the non-collagenous NC16A domain of BP180. Clinical findings and murine models of BP have provided evidence of a pathogenic role of anti-NC16A autoantibodies. However, it is largely unknown what triggers the breakage of immunotolerance against BP180 in elderly individuals. The incidence of BP has been increased over the past two decades in several countries. Aside from aging populations, the factors behind this phenomenon are still not fully understood. Neurodegenerative diseases such as multiple sclerosis, Parkinson's disease, and certain dementias are independent risk factors for BP. Recently several case reports have described BP in patients with diabetes mellitus (DM) patients who have been treated with dipeptidyl peptidase-4 inhibitors (DPP-4i or gliptins), which are a widely used class of anti-DM drugs. The association between the use of DPP-4is, particularly vildagliptin, and BP risk has been confirmed by several epidemiological studies. Evidence suggests that cases of gliptin-associated BP in Japan display certain features that set them apart from cases of "regular" BP. These include a "non-inflammatory" phenotype, targeting by antibodies of different immunodominant BP180 epitopes, and a specific association with the human leukocyte antigen (HLA) types. However, recent studies in European populations have found no major differences between the clinical and immunological characteristics of gliptin-associated BP and "regular" BP. The DPP-4 protein (also known as CD26) is ubiquitously expressed and has multiple functions in various cell types. The different effects of the inhibition of DPP-4/CD26 activity include, for example, tissue modeling and regulation of inflammatory cells such as T lymphocytes. Although the pathomechanism of gliptin-associated BP is currently largely unknown, investigation of the unique effect of gliptins in the induction of BP may provide a novel route to better understanding of how immunotolerance against BP180 breaks down in BP.