Antagonistic antiviral activity between IFN-lambda and IFN-alpha against lethal Crimean-Congo hemorrhagic fever virus in vitro

Abstract

Background and aims: Crimean Congo Hemorrhagic fever virus (CCHFV) is the causative agent of Crimean-Congo hemorrhagic fever, a severe disease with a mortality rate of around 30% in humans. Previous studies demonstrate that pre-treatment with type I IFNs have an antiviral effect against CCHFV, while established CCHFV infection is almost insensitive to subsequent IFN-α treatment. No data concerning type III IFNs antiviral activity against CCHFV are available so far. The aim of the present study was to explore the capability of IFN-λ1 to inhibit the replication of CCHFV and the possible synergism/antagonism between IFN-α and IFN-λ1 both in the inhibition of CCHFV replication and in the activation of intracellular pathways of IFN response.

Methods: Human A549 and HuH7 cells were treated with increasing amounts of IFN-λ1, or IFN-α or a combination of them, infected with CCHF; the extent of virus yield inhibition and the induction of MxA and 2'-5'OAS mRNA was measured.

Results and conclusions: Our study pointed out that type III IFN possess an antiviral activity against CCHFV, even if lower than type I IFN. Moreover, a clear antagonism between IFN-λ and IFN-α was observed in both cell lines (A549 and HuH7 cells), in terms of antiviral effect and activation of pivotal ISGs, i.e. MxA and 2'-5'OAS. Elucidating the interplay between type I and III IFNs will help to better understand innate defence mechanisms against viral infections and may provide novel scientific evidence for a more rational planning of available and future treatments, particularly against human diseases caused by high concern viruses.

Fig 1. Dose-dependent inhibition of CCHFV replication by recombinant IFN-α, IFN-λ1 and IFN-α+IFN-λ1.

A549 (a) and HuH7 cells (b) were treated for 1 day with increasing amounts of either IFN type, alone or in combination, then infected with CCHFV at MOI 0.01; infectious virus yield was measured after overnight incubation. One out of three experiments is shown. Dotted lines: IFN-α (●) or IFN-λ1 (▲) used alone; continuous line: IFN-α and IFN-λ1 (■) used in combination.

Fig 2. Dose-dependent induction of MxA and 2’-5’OAS mRNA levels following treatment with recombinant IFN-α, IFN-λ1 and IFN-α +IFN-λ1.

A549 (a), (c) and HuH7 cells (b), (d) were exposed 3h to increasing amounts of either IFN type, alone or in combination, then mRNA levels for MxA (a), (b) and 2’-5’OAS (c), (d) were measured, expressed as fold induction vs. untreated cells. One out of three experiments is shown. Dotted lines: IFN-α (●) or IFN-λ1 (▲) used alone; continuous line: IFN-α and IFN-λ1 (■) used in combination.