Calcium Ionophore A23187 Inhibits Human Parainfluenza Virus Type 2 Growth and Monoclonal Antibody against CD98 Heavy Chain Recovers the Inhibition

Abstract

Calcium ionophore A23187 (A23187) inhibited human parainfluenza virus type 2 (hPIV-2) replication in LLCMK2 cells and the inhibition was almost completely recovered by monoclonal antibody (mAb) against CD98 heavy chain (CD98HC). A23187 considerably reduced the number of viruses released from the cells. Virus nucleoprotein (NP), fusion (F) and hemaggulutinin-neuraminidase (HN) gene syntheses were not inhibited. However, a direct immunofluorescence study showed that A23187 largely inhibited virus NP, F and HN protein syntheses. Using a recombinant green fluorescence protein (GFP)-expressing hPIV-2 without matrix (M) protein (rghPIV-2i„M), it was found that virus entry into the cells was not inhibited, and that cell-to-cell spreading of virus was not blocked by A23187 either. The effects of A23187 on both actin microfilaments and microtubules were observed, and it was found to cause disruption of both of them. The effect of CD98HC mAb on the inhibition induced by A23187 was analyzed. CD98HC mAb recovered the inhibition by A23187. Virus production was considerably recovered. Virus protein was synthesized by the addition of CD98HC mAb. Almost normal actin microfilaments and microtubules were observed in the presence of CD98HC mAb. These results suggested that the inhibitory effect of A23187 was mainly caused by the inhibition of virus protein synthesis and disruption of cytoskeleton. The precise mechanisms of the inhibitory effect of A23187 and recovery from A23187-induced inhibition by CD98HC mAb are unclear, but the modulation of cytosolic Ca2+ concentration may be important for viral protein synthesis and for the preservation of cytoskeleton.