Plasmacytoid dendritic cells (pDCs), a main source of type I interferon in response to viral infection, are an early cell target during lymphocytic choriomeningitis virus (LCMV) infection, which has been associated with the LCMV's ability to establish chronic infections. Human blood-derived pDCs have been reported to be refractory to ex vivo LCMV infection. In the present study we show that human pDC CAL-1 cells are refractory to infection with cell-free LCMV, but highly susceptible to infection with recombinant LCMVs carrying the surface glycoprotein of VSV, indicating that LCMV infection of CAL-1 cells is restricted at the cell entry step. Co-culture of uninfected CAL-1 cells with LCMV-infected HEK293 cells enabled LCMV to infect CAL-1 cells. This cell-to-cell spread required direct cell-cell contact and did not involve exosome pathway. Our findings indicate the presence of a novel entry pathway utilized by LCMV to infect pDC.

浆细胞样树突状细胞（pDC）是响应病毒感染的I型干扰素的主要来源，是淋巴细胞性脉络膜脑膜炎病毒（LCMV）感染期间的早期细胞靶标，这与LCMV建立慢性感染的能力有关。据报道，人血源性pDC对体外难治LCMV感染。在本研究中，我们显示人pDC CAL-1细胞难于感染无细胞LCMV，但高度易受携带VSV表面糖蛋白的重组LCMV感染，表明CAL-1细胞的LCMV感染仅限于单元格输入步骤。未感染的CAL-1细胞与LCMV感染的HEK293细胞共培养使LCMV能够感染CAL-1细胞。这种细胞间扩散需要直接的细胞间接触，并且不涉及外泌体途径。我们的发现表明存在由LCMV感染pDC的新型进入途径。