Virucidal activity of Haemaphysalis longicornis longicin P4 peptide against tick-borne encephalitis virus surrogate Langat virus

Abstract

BackgroundLongicin is a defensin-like peptide, identified from the midgut epithelium of hard tick Haemaphysalis longicornis. Several studies have already shown the antimicrobial and parasiticidal activities of longicin peptide and one of its synthetic partial analogs, longicin P4. In this study, longicin peptides were tested for potential antiviral activity against Langat virus (LGTV), a tick-borne flavivirus.MethodsLongicin P1 and P4 peptides were chemically synthesized. Antiviral activity of the longicin peptides against LGTV was evaluated through in vitro virucidal assays, wherein the antiviral efficacy was determined by reduction in number of viral foci and virus yield. Additionally, longicin P4 was also tested for its activity against human adenovirus, a non-enveloped virus. Lastly, to assess the importance of longicin on the innate antiviral immunity of H. longicornis ticks, gene silencing through RNAi was performed.ResultsLongicin P4 produced significant viral foci reduction and lower virus yield against LGTV, while longicin P1 failed to demonstrate the same results. Conversely, both longicin partial analogs (P1 and P4) did not show significant antiviral activity when tested on adenovirus. In addition, longicin-silenced ticks showed significantly higher virus titer after 7 days post-infection but a significantly lower titer was detected after an additional 14 days of observation as compared to the Luc dsRNA-injected ticks. Mortality in both groups did not show any significant difference.ConclusionOur results suggest that longicin P4 has in vitro antiviral activity against LGTV but not against a non-enveloped virus such as adenovirus. Likewise, though most cationic antimicrobial peptides like longicin act directly on target membranes, the exact mechanism of membrane targeting of longicin P4 in enveloped viruses, such as LGTV, requires further investigation. Lastly, while the in vitro virucidal capacity of longicin P4 was confirmed in this study, the role of the endogenous tick longicin in the antiviral defense of H. longicornis against LGTV still remains to be demonstrated.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1344-5) contains supplementary material, which is available to authorized users.

Defensins as a promising class of tick antimicrobial peptides: a scoping review

“…Longicin P4 bound to tachyzoites and resulted in pore formation, disorganization, and hollowing in the membrane, thus killing the parasites [ 32 ]. The functional spectrum of longicin P4 was expanded to Langat virus (LGTV), a naturally attenuated strain as a convenient model of tick-borne flaviviruses [ 67 , 68 ]. Co-incubation of LGTV with longicin P4 before infection obviously decreased viral foci and virus yield, confirming that the action of longicin P4 against LGTV was through extracellular contact.…”

Tick-Borne Viruses and Biological Processes at the Tick-Host-Virus Interface

“…RNA interference (RNAi) appears to be the main antiviral mechanism in ticks that, together with Argonaute (Ago) and endoribonuclease Dicer (Dcr) proteins mediates tick antiviral responses (Schnettler et al, 2014 ; Gulia-Nuss et al, 2016 ). However, at present the role of defensin-like peptides displaying in vitro virucidal activities against TBV (e.g., longicin or HEdefensin from Haemaphysalis longicornis ) is unclear in tick antiviral defense (Talactac et al, 2016 , 2017 ).…”

A Continuing Exploration of Tick–Virus Interactions Using Various Experimental Viral Infections of Hard Ticks

“…This technique also requires a microinjector to efficiently introduce the inoculum into the tick and may produce higher tick mortality due to injection injury (Rechav et al, 1999). Previous studies using this technique include the infection of H. longicornis with the Langat virus (Talactac et al, 2016, 2017a), A. variegatum with the Thogoto virus (Kaufman and Nuttall, 1996), I. ricinus with TBEV (Labuda et al, 1993, 1996, 1997b; Khasnatinov et al, 2009; Belova et al, 2012), and the Louping ill virus (Jones et al, 1997). D. marginatus , D. reticulatus , and I. ricinus ticks also previously received percoxal injections with the Bhanja and Palma viruses (Labuda et al, 1997a).…”