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Measles virus induces persistent infection by autoregulation of viral replication

View Article: PubMed Central - PubMed

ABSTRACT

Natural infection with measles virus (MV) establishes lifelong immunity. Persistent infection with MV is likely involved in this phenomenon, as non-replicating protein antigens never induce such long-term immunity. Although MV establishes stable persistent infection in vitro and possibly in vivo, the mechanism by which this occurs is largely unknown. Here, we demonstrate that MV changes the infection mode from lytic to non-lytic and evades the innate immune response to establish persistent infection without viral genome mutation. We found that, in the persistent phase, the viral RNA level declined with the termination of interferon production and cell death. Our analysis of viral protein dynamics shows that during the establishment of persistent infection, the nucleoprotein level was sustained while the phosphoprotein and large protein levels declined. The ectopic expression of nucleoprotein suppressed viral replication, indicating that viral replication is self-regulated by nucleoprotein accumulation during persistent infection. The persistently infected cells were able to produce interferon in response to poly I:C stimulation, suggesting that MV does not interfere with host interferon responses in persistent infection. Our results may provide mechanistic insight into the persistent infection of this cytopathic RNA virus that induces lifelong immunity.

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Effect of MV N overexpression on MV replication.(a) Expression of MV N protein and P protein in 293SLAM cells, stably MV N-expressing 293SLAM cells (293SLAM-MV-N), and 293SLAM cell clones expressing MV N and P protein with different expression levels (293SLAM-NP clones #3, 6, 8, and 9). GAPDH was used as an internal control. (b) 293SLAM, 293SLAM-MV-N cells, and 293SLAM-NP clones were infected with rMV-EGFP at a MOI of 0.1. Representative fluorescence microscopy images of four independent infections are shown.
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f6: Effect of MV N overexpression on MV replication.(a) Expression of MV N protein and P protein in 293SLAM cells, stably MV N-expressing 293SLAM cells (293SLAM-MV-N), and 293SLAM cell clones expressing MV N and P protein with different expression levels (293SLAM-NP clones #3, 6, 8, and 9). GAPDH was used as an internal control. (b) 293SLAM, 293SLAM-MV-N cells, and 293SLAM-NP clones were infected with rMV-EGFP at a MOI of 0.1. Representative fluorescence microscopy images of four independent infections are shown.

Mentions: Based on these observations and the fact that N protein has known a binding capacity for P protein, viral genome, and cellular factors34, we hypothesised that the over-accumulation of N protein competes with the viral genome for binding to the P-L complex and to the cellular factors that are required for MV replication. To examine this possibility, we established 293SLAM cells stably expressing N protein with or without different levels of P protein (293SLAM-N, 293SLAM-NP clones #3, 6, 8, and 9; Fig. 6a) and then infected these cells with rMV-EGFP to monitor viral replication. The viral replication was suppressed by the overexpression of N protein in 293SLAM-N cells, but the expression levels of N protein in 293SLAM-NP clones #8 and 9 were not sufficient to block MV replication. Although the expression levels of N protein in clones #3 and 6 were comparable to that in the 293SLAM-N cells, the suppression of MV was restored by the co-expression of P protein (Fig. 6b). Thus, the accumulation of N protein to sufficiently higher levels than that of P protein causes a downregulation of MV viral replication.


Measles virus induces persistent infection by autoregulation of viral replication
Effect of MV N overexpression on MV replication.(a) Expression of MV N protein and P protein in 293SLAM cells, stably MV N-expressing 293SLAM cells (293SLAM-MV-N), and 293SLAM cell clones expressing MV N and P protein with different expression levels (293SLAM-NP clones #3, 6, 8, and 9). GAPDH was used as an internal control. (b) 293SLAM, 293SLAM-MV-N cells, and 293SLAM-NP clones were infected with rMV-EGFP at a MOI of 0.1. Representative fluorescence microscopy images of four independent infections are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5121633&req=5

f6: Effect of MV N overexpression on MV replication.(a) Expression of MV N protein and P protein in 293SLAM cells, stably MV N-expressing 293SLAM cells (293SLAM-MV-N), and 293SLAM cell clones expressing MV N and P protein with different expression levels (293SLAM-NP clones #3, 6, 8, and 9). GAPDH was used as an internal control. (b) 293SLAM, 293SLAM-MV-N cells, and 293SLAM-NP clones were infected with rMV-EGFP at a MOI of 0.1. Representative fluorescence microscopy images of four independent infections are shown.
Mentions: Based on these observations and the fact that N protein has known a binding capacity for P protein, viral genome, and cellular factors34, we hypothesised that the over-accumulation of N protein competes with the viral genome for binding to the P-L complex and to the cellular factors that are required for MV replication. To examine this possibility, we established 293SLAM cells stably expressing N protein with or without different levels of P protein (293SLAM-N, 293SLAM-NP clones #3, 6, 8, and 9; Fig. 6a) and then infected these cells with rMV-EGFP to monitor viral replication. The viral replication was suppressed by the overexpression of N protein in 293SLAM-N cells, but the expression levels of N protein in 293SLAM-NP clones #8 and 9 were not sufficient to block MV replication. Although the expression levels of N protein in clones #3 and 6 were comparable to that in the 293SLAM-N cells, the suppression of MV was restored by the co-expression of P protein (Fig. 6b). Thus, the accumulation of N protein to sufficiently higher levels than that of P protein causes a downregulation of MV viral replication.

View Article: PubMed Central - PubMed

ABSTRACT

Natural infection with measles virus (MV) establishes lifelong immunity. Persistent infection with MV is likely involved in this phenomenon, as non-replicating protein antigens never induce such long-term immunity. Although MV establishes stable persistent infection in vitro and possibly in vivo, the mechanism by which this occurs is largely unknown. Here, we demonstrate that MV changes the infection mode from lytic to non-lytic and evades the innate immune response to establish persistent infection without viral genome mutation. We found that, in the persistent phase, the viral RNA level declined with the termination of interferon production and cell death. Our analysis of viral protein dynamics shows that during the establishment of persistent infection, the nucleoprotein level was sustained while the phosphoprotein and large protein levels declined. The ectopic expression of nucleoprotein suppressed viral replication, indicating that viral replication is self-regulated by nucleoprotein accumulation during persistent infection. The persistently infected cells were able to produce interferon in response to poly I:C stimulation, suggesting that MV does not interfere with host interferon responses in persistent infection. Our results may provide mechanistic insight into the persistent infection of this cytopathic RNA virus that induces lifelong immunity.

No MeSH data available.


Related in: MedlinePlus