Study of Viral Coinfection of the Ixodes persulcatus Ticks Feeding on Humans in a Natural Focus of the South of the Far East

Abstract

The phenomenon of pathogen co-infection detected in a half-fed Ixodes persulcatus tick taken from a human in the south of the Far East was studied. Research was carried out on PEK, Vero, and Vero-E6 cell lines, outbred mice, and chicken embryos using ELISA, PCR, IMFA, plaque formation, and electron microscopy. The tick contained an antigen and a genetic marker of the tick-borne encephalitis virus (TBEV). The patient had post-vaccination antibodies in a titer of 1:200, as a result of which, obviously, an antibody-dependent elimination of TBEV occurred. The tick-borne co-isolate also contained an unknown pathogen (Kiparis-144 virus), which, in our opinion, was a trigger for the activation of chronic infection in suckling white mice. In the laboratory co-isolate, ectromelia virus was present, as evidenced by paw edema during the intradermal infection of mice, characteristic rashes on the chorioallantoic envelope of chicken embryos, and typical plaques on Vero-E6. The Kiparis-144 virus was not pathogenic for white mice and chicken embryos, but it successfully multiplied in the PEK, Vero, and Vero-E6 lines. Viral co-infection was confirmed by electron microscopy. Passaging on mice contributed to an increase in the virulence of the co-isolate, whose titer increased by 10,000 times by the fifth passage, which poses an epidemiological danger.

Co-infection in the Tick Microbiome and in Humans as a Natural Process of Co-cultivation of Tick-Borne Pathogens<strong> </strong>

“…Shown here are dense conglomerates consisting of fused pox-viral particles with small virus particles up to 100 nm in size adhered to them. The electron microscopic picture demonstrated the phenomenon of co-cultivation of two viruses -the ECTV virus and the KiparisV virus, which we described previously [16].…”

“…Single or merged several copies of freely lying particles of the same small virus, up to 100 nm in size, were found. We described a similar relationship between the new KiparisV virus and ectromelia virus (ECTV) in a previous article [16]. To compare the electron microscopic picture of KiparisV and ECTV we present Figure 2.…”

“…According to the literature, mixed infection of ticks is a fairly common event and is recorded in 6.3-25.8% of cases [8,9]. The detected activation of the ECTV virus during co-cultivation with the KiparisV virus revealed an important feature -a sharp increase in the virulence and pathogenicity of the mouse virus [16]. Previously, we drew attention to this feature of increased pathogenicity of individual pathogens in humans with the simultaneous detection of several pathogens of tick-borne infections after tick bites.…”

“…[10]. The identification of a new virus KiparisV [16] in a half-fed I persulcatus tick removed from a human dictated the need to study, first of all, its role in human pathology, as well as conducting research to determine the characteristics of its behavior in the tick microbiome.…”

“…An example of this was our comprehensive studies of the half-fed tick I. persulcatus, removed from a person in 2016, when, against the background of co-infection with the murine ectromelia virus (ECTV), we were able to verify the new virus Kiparis-144, later KiparisV [16]. It was shown that when these two viruses are co-cultivated in the body of warm-blooded animals, the new KiparisV virus acts as an amplifier or "accelerator" of the replication of the mousepox virus, dramatically increasing its virulence.…”