Inhibition of Human Parainfluenza Virus-3 Replication by Interferon and Human MxA

Abstract

We have investigated the IFN-mediated inhibition of human parainfluenza virus-3 (HPIV-3) replication in cultured human A549 cells. IFN-alpha inhibited the virus yield significantly with concomitant reduction of viral RNA accumulation by more than 90%. Further studies indicated that the inhibitory action of IFN was at the level of primary transcription of HPIV3 replication. Since the IFN-inducible protein, MxA, has been shown to inhibit virus replication in several RNA viruses, we examined the role of MxA in HPIV-3 replication using a stably transfected human glioblastoma cell line expressing MxA. In these cells HPIV-3 replication was decreased by more than 100-fold depending on the virus dosage used with concomitant inhibition of viral RNA synthesis by about 80%. However, the viral primary transcription was not affected in this MxA-producing cell line. In contrast, in the parental cell line IFN-mediated inhibition occurred at the primary transcription step of HPIV-3 replication. These data suggest that in addition to MxA, other IFN-inducible proteins are involved in the anti-HPIV-3 effect of IFN in both the cell lines used.

Antivirally active MxA protein sequesters La Crosse virus nucleocapsid protein into perinuclear complexes

“…As a consequence, the drop in the amount of free N below a critical concentration may block genome amplification, without affecting viral transcription. Likewise, FLUAV and parainfluenzavirus type 3 seem to be blocked by MxA at the level of genome amplification (38,39), and it is conceivable that a similar antiviral mechanism is at work. Elucidating the mechanism of MxA action should help to better understand innate immunity against RNA viruses and provide new means to control these human pathogens.…”

Polymorphisms in interferon-induced genes and the outcome of hepatitis C virus infection: roles of MxA, OAS-1 and PKR

“…1 MxA protein has selective activity against several viruses. [2][3][4] However, the precise mechanism of antiviral action has not been elucidated. Studies of in vivo MxA levels in patients treated with interferon for hepatitis C virus (HCV) have shown greater levels in virological responders than nonresponders.…”

Inhibition of human parainfluenza virus type 3 infection by novel small molecules

“…[ 35 S] Methionine-labeled HPIV3 was prepared (Wechsler et al, 1985) and used to analyze the effects of the compounds on adsorption and internalization of the virus in A549 cells as described previously (Bose et al, 2004;Zhao et al, 1996). Briefly, for the adsorption assay, 0.3 MOI of 35 S-HPIV3 (2.8×10 5 cpm) was added to chilled A549 cells in the presence of 13.75μM of compounds.…”

“…The primary transcription assay was performed as described previously (Zhao et al, 1996). In brief, confluent A549 cells were cultured in the presence of anisomycin at 100μM for 2h.…”

“…Because there was a noticeable decrease of virus titer and HN protein expression during 0-2h treatment with the compounds, especially for C7 (C5 is not nearly as potent when applied for 2h and then removed), we wanted to ascertain whether adsorption and internalization of the virus were compromised. Using purified 35 S-HPIV3 as described in Materials and Methods, we tested the adsorption and internalization processes using the standard biochemical procedures (Bose et al, 2004;Zhao et al 1996). No significant difference of radioactivity between treated and untreated cells was found associated with the cells at 4°C as well as within the cells when incubated at 37°C for 2h, strongly suggesting that the inhibitory effect is not directed at the steps of attachment and penetration in early life cycle of the virus.…”