Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk.

BACKGROUND: Tick distribution in Sweden has increased in recent years, with the prevalence of ticks predicted to spread towards the northern parts of the country, thus increasing the risk of tick-borne zoonoses in new regions. Tick-borne encephalitis (TBE) is the most significant viral tick-borne zoonotic disease in Europe. The disease is caused by TBE virus (TBEV) infection which often leads to severe encephalitis and myelitis in humans. TBEV is usually transmitted to humans via tick bites; however, the virus can also be excreted in the milk of goats, sheep and cattle and infection may then occur via consumption of unpasteurised dairy products. Virus prevalence in questing ticks is an unreliable indicator of TBE infection risk as viral RNA is rarely detected even in large sample sizes collected at TBE-endemic areas. Hence, there is a need for robust surveillance techniques to identify emerging TBEV risk areas at early stages. METHODS: Milk and colostrum samples were collected from sheep and goats in Örebro County, Sweden. The milk samples were analysed for the presence of TBEV antibodies by ELISA and validated by western blot in which milk samples were used to detect over-expressed TBEV E-protein in crude cell extracts. Neutralising titers were determined by focus reduction neutralisation test (FRNT). The stability of TBEV in milk and colostrum was studied at different temperatures. RESULTS: In this study we have developed a novel strategy to identify new TBEV foci. By monitoring TBEV antibodies in milk, we have identified three previously unknown foci in Örebro County which also overlap with areas of TBE infection reported during 2009-2018. In addition, our data indicates that keeping unpasteurised milk at 4 °C will preserve the infectivity of TBEV for several days. CONCLUSIONS: Altogether, we report a non-invasive surveillance technique for revealing risk areas for TBE in Sweden, by detecting TBEV antibodies in sheep milk. This approach is robust and reliable and can accordingly be used to map TBEV "hotspots". TBEV infectivity in refrigerated milk was preserved, emphasising the importance of pasteurisation (i.e. 72 °C for 15 s) prior to consumption.

[Preclinical and clinical studies of the efficacy of Panavir in therapy for tick-borne encephalitis].

The antiviral activity of Panavir was studied on a model of mice infected with the strain Sofjin of tick-borne encephalitis (TBE) virus. The efficacy of Panavir was studied in the treatment of the chronic (monotherapy; 30 patients) and acute febrile and meningeal (combined therapy; n = 113) forms of TBE. Panavir was found to have a positive effect on the clinical course of TBE and the immune mechanisms of the body's protection.

[A comparison of the immune response induced by DNA or by an inactivated vaccine against tick-borne encephalitis]. / Sravnenie immunnogo otveta, indutsirovannogo DNK ili inaktivirovannoi vaktsinoi protiv kleshchevogo éntsefalita.

BALB/c mice were immunized with recombinant plasmid DNA pSVK3-ENS1 and pcDNAI-NS3 containing, respectively, genes E-NS1 and NS3 of tick-borne encephalitis (TBE) virus. Antibodies to TBE virus proteins were detected in the blood sera of the immunized animals by the method of the enzyme immunoassay. Though the titers of virus-specific antibodies in the sera of mice immunized with protein vaccines exceeded those registered after immunization with DNA vaccines, essential protective immunity was observed after the use of both vaccines.

Evaluation of tick-borne encephalitis DNA vaccines in monkeys.

Tick-borne encephalitis is usually caused by infection with one of two flaviviruses: Russian spring summer encephalitis virus (RSSEV) or Central European encephalitis virus (CEEV). We previously demonstrated that gene gun inoculation of mice with naked DNA vaccines expressing the prM and E genes of these viruses resulted in long-lived homologous and heterologous protective immunity (Schmaljohn et al., 1997). To further evaluate these vaccines, we inoculated rhesus macaques by gene gun with the RSSEV or CEEV vaccines or with both DNA vaccines and compared resulting antibody titers with those obtained by vaccination with a commercial, formalin-inactivated vaccine administered at the human dose. Vaccinations were given at days 0, 30, and 70. All of the vaccines elicited antibodies detected by ELISA and by plaque-reduction neutralization tests. The neutralizing antibody responses persisted for at least 15 weeks after the final vaccination. Because monkeys are not uniformly susceptible to tick-borne encephalitis, the protective properties of the vaccines were assessed by passive transfer of monkey sera to mice and subsequent challenge of the mice with RSSEV or CEEV. One hour after transfer, mice that received 50 microl of sera from monkeys vaccinated with both DNA vaccines had circulating neutralizing antibody levels <20-80. All of these mice were protected from challenge with RSSEV or CEEV. Mice that received 10 microl of sera from monkeys vaccinated with the individual DNA vaccines, both DNA vaccines, or a commercial vaccine were partially to completely protected from RSSEV or CEEV challenge. These data suggest that DNA vaccines may offer protective immunity to primates similar to that obtained with a commercial inactivated-virus vaccine.

[An immunomodifier--staphylococcal anatoxin--prevents the development of immunosuppression caused by informational stress in mice]. / Immunomodifikator--stafilokokkovyi anatoksin--preduprezhdaet razvitie immunosupressii, vyzvannoi informatsionnym stressom u myshei.

The action of information stress for 14 days leads to the development of immunosuppression, which is manifested by the suppression of humoral response to sheep red blood cells (SRBC) and the decrease of resistance to Langat virus having low pathogenicity. As shown in this investigation, an immunomodifier, purified staphylococcal toxoid (PST), protects experimental animals from the immunosuppressive effect of information stress. After the injection of PST to stress-affected mice in doses of 15 or 1.5 binding units per animal on days 9, 11 and 13 of the experiment their humoral response to SRBC and resistance to Langat virus are partially restored (by 45-60%).

[The antiviral action of medicinal plant extracts in experimental tick-borne encephalitis]. / Protivovirusnoe deistvie ékstraktov lekarstvennykh rastenii pri éksperimental'nom kleshchevom éntsefalite.

Some mechanisms of inducing resistance to experimental infection with tick-borne encephalitis virus were studied in experimental mice treated with aqueous extracts of berries of Vaccinium vitis-idaea, black currant, Vaccinium myrtillus, and of greater celandine grass. The condition of the immune system organs (spleen and thymus) after treatment with the extracts under study was analysed. A correlation was found between the degree of developing resistance to infection, virus accumulation in the brain, blood, spleen and thymus and changes in some parameters (spleen and thymus indices) of these immunocompetent organs. Possible mechanisms of induction of resistance to virus by herb extracts are discussed.

[Antiviral and immunostimulating effect of maleic anhydride copolymers in experimental neuroviral infections]. / Protivovirusnyi i immunostimuliruiushchii éffekt sopolimerov maleinovogo angidrida pri éksperimental'nykh neirovirusnykh infektsiiakh.

The virus-inhibiting and immunostimulating activity of Soviet preparations, maleic anhydride copolymers, was demonstrated in alpha-, flavi-, and bunyavirus infections. Positive results were obtained in subcutaneous and intraperitoneal inoculations of the preparations used in prophylactic and therapeutic-prophylactic schedules. Stimulation of vaccination immunity was observed after combined use of copolymers and the vaccine against Eastern equine encephalomyelitis.

[Combined antiviral effect of synthetic polyribonucleotide interferonogens and specific antiviral antibodies in arbovirus infections]. / Kombinirovannyi protivovirusnyi éffekt sinteticheskikh poliribonukleotidnykh interferonogenov i spetsificheskikh protivovirusnykh antitel pri arbovirusnykh infektsiiakh.

A model of tick-borne encephalitis in BALB/c mice was used to investigate the protective anti-viral effect of an interferon inducer, poly(G).poly(C), and specific gamma-globulin administered to the animals together or separately in small doses 24 hours before or after virus inoculation. Administration to the animals of poly(G).poly(C) alone or gamma-globulin alone was shown to produce a poor protective effect. Simultaneous administration of both preparations resulted in a significant decrease of mouse mortality after infection. As a result of the pretreatment of chick embryo cell cultures with poly(G).poly(C) before inoculation and the addition of specific immune serum to the agar overlay after the Sindbis virus inoculation, its multiplication was inhibited much more than after treatment of the cells with interferon inducer alone or antibody alone. Possible mechanisms of the observed additive antiviral effects of the interferon inducer and antibody, including those associated with the influence on the virus-induced interferon production, as well as the possibility of their combined use for the prevention and treatment of viral infections are discussed.

Morphological demonstration of the virus of tick-borne encephalitis in the human brain.

A case is presented in which the fourfold increase of the HI titer during the progression of the disease, and an increase in IgM content found at the beginning of the second week of the disease confirmed the diagnosis of tick-borne encephalitis. The light microscopic changes correspond to the findings accepted as characteristic to tick-borne encephalitis. Viruses, morphologically belonging to the Flavivirus genus were found by electron microscopy in the thalamus, substantia nigra, and cerebellum of the dissected brain. This paper presents the first demonstration of the virus in a case of a human tick-borne encephalitis.