Epidemiological study of tick-borne encephalitis virus in northern Greece

Serum samples from 921 apparently healthy individuals living in different prefectures of Northern Greece were investigated for the presence of antibodies against tick-borne encephalitis (TBE) virus. In addition, serum and cerebrospinal fluid samples of 302 patients with central nervous system (CNS) infection were tested for the presence of specific IgG and IgM antibodies and TBE virus RNA. Two percent of the general population was found to have antibodies to the virus, with no significant differences among the age groups. Most of the seropositive individuals were male farmers, while seroprevalence varied among different prefectures (0%-5.8%). TBE was not confirmed by laboratory findings in any of the patients with CNS infection. Results of this study revealed that a flavivirus of the TBE serocomplex is circulating in Greece, yet is not a major public health problem.     

A tick-borne encephalitis virus vaccine based on the European prototype strain induces broadly reactive cross-neutralizing antibodies in humans

After vaccination of humans with tick-borne encephalitis virus (TBEV) vaccine, the extent of cross-neutralization between viruses of the European, Far Eastern, and Siberian subtypes of TBEV and Omsk hemorrhagic fever virus (OHFV) was analyzed. Hybrid viruses that encode the TBEV surface proteins for representative viruses within all subtypes, and OHFV, were constructed using the West Nile virus (WNV) backbone as vector. These viruses allow for unbiased head-to-head comparison in neutralization assays because they exhibit the antigenic characteristics of the TBEV strains from which the surface proteins were derived and showed equivalent biologic properties in cell culture. Human serum samples derived from a TBEV vaccine trial were analyzed and revealed comparable neutralizing antibody titers against European, Far Eastern, and Siberian subtype viruses, indicating equally potent cross-protection against these TBEV strains and a somewhat reduced but still protective neutralization capacity against more distantly related viruses, such as OHFV.     

Epidemiology of tick-borne encephalitis (TBE) and phylogenetic analysis of TBE viruses in Japan and Far Eastern Russia

In Oshima, the southern part of Hokkaido, a tick-borne encephalitis (TBE) patient was found in 1993; in addition TBE virus was isolated from the blood samples of sentinel dogs, ticks pools, and rodents spleens in 1995 and 1996 by suckling mice. To identify when these TBE viruses emerged in Hokkaido, the times of divergence of TBE virus strains isolated in Oshima and Far Eastern Russia were estimated. TBE virus was isolated in Khabarovsk in 1998, and the nucleotide sequences of viral envelope protein genes of isolates from Oshima and Khabarovsk were compared. Based on the synonymous substitution rates of these virus E-protein genes, the lineage-divergence times of these TBE virus strains were predicted phylogenetically to be approximately 260-430 years ago. Furthermore, the virulence of TBE virus isolates from Oshima and Khabarovsk were compared in a mouse model. The results showed that the isolates possessed very similar virulence in mice. European TBE vaccine was found to be effective in TBE virus, Hokkaido strain. This review provides evidence that the Oshima strains of TBE virus in Hokkaido emerged from the Far Eastern Russia a few hundred years ago, which explains why the virulence of these strains is similar to that of TBE viruses isolated in Russia. Practical application of the vaccine should be considered in Japan.     

The transmission of the tick-borne encephalitis virus via cow's milk]

A case of group infection with tick-borne encephalitis (TBE) in Bikin, Khabarovsk Territory is reviewed. The disease developed as a result of drinking raw cow milk, bought from one owner, and eating sour-milk products made of that milk. 5 persons from 3 families were ill, in three cases the outcome was lethal. Data of clinical, epidemiological, viral and serological examinations confirm the diagnosis of TBE. Various antibodies to TBE virus have been determined in the blood of cows. The presence of complement-fixing antibodies may indicate fresh infection. The characteristics of TBE viral strain, isolated from the brain of dead Z. N. F. is presented on white mice. The data obtained confirm the previous suggestion on possible transmission of TBE virus with cow milk.     

The Japanese Encephalitis Antigenic Complex Viruses: From Structure to Immunity

In the last three decades, several flaviviruses of concern that belong to different antigenic groups have expanded geographically. This has resulted in the presence of often more than one virus from a single antigenic group in some areas, while in Europe, Africa and Australia, additionally, multiple viruses belonging to the Japanese encephalitis (JE) serogroup co-circulate. Morphological heterogeneity of flaviviruses dictates antibody recognition and affects virus neutralization, which influences infection control. The latter is further impacted by sequential infections involving diverse flaviviruses co-circulating within a region and their cross-reactivity. The ensuing complex molecular virus–host interplay leads to either cross-protection or disease enhancement; however, the molecular determinants and mechanisms driving these outcomes are unclear. In this review, we provide an overview of the epidemiology of four JE serocomplex viruses, parameters affecting flaviviral heterogeneity and antibody recognition, host immune responses and the current knowledge of the cross-reactivity involving JE serocomplex flaviviruses that leads to differential clinical outcomes, which may inform future preventative and therapeutic interventions.     

Subacute infection with temperature-sensitive vesicular stomatitis virus mutant G41 in the central nervous system of mice. I. Clinical and virologic studies.

Inoculation of three- to four-week-old BALB/c mice with temperature-sensitive (ts) vesicular stomatitis virus mutant G41 produced a subacute neurological disease, initially characterized by development of lethargy, hunched posture, and ruffled fur within five to seven days after infection. More than 90% of infected mice developed these clinical signs. In approximately 60% of infected mice, the initial neurological signs proceeded to striking hind-limb paralysis and weight loss. These signs usually appeared by seven to nine days after infection and lasted for 21-28 days. Only 16% of the mice died as a result of infection; death usually occurred eight to 12 days after infection. Most of the infected mice recovered from the acute phase of disease and appeared normal by four weeks after infection. However, hind-limb paralysis persisted in 4% of the mice for as long as the mice were observed, i.e., 42 days. The mutant ts-G41 was recovered from the brains and spinal cords of infected mice for the first seven days after infection. Peak titers of virus were modest, 10(4)-10(5) pfu/ml in brain tissue and 10(3)-10(4) pfu/ml in spinal cord tissue. Virus isolated after in vivo infection was temperature-sensitive and thus not revertant wild-type virus. Although virus was recoverable by homogenization for only the first seven days of infection, use of cocultivation techniques permitted the detection of ts-G41 in brains and spinal cords of infected animals for as long as 21 days after infection. Virus recovered by cocultivation was also temperature-sensitive.     

Acute Flaccid Paralysis as an Unusual Presenting Symptom of Japanese Encephalitis: A Case Report and Review of the Literature

Abstract Japanese encephalitis (JE) is an endemic disease in Taiwan. Acute JE virus infection characterized by acute flaccid paralysis in an adult has never been reported in Taiwan. We report a young adult man who received four doses of JEV (Nakayama strain) vaccination in childhood, but still developed acute JE virus infection, characterized with acute flaccid paralysis. He presented with fever, headache, progressive muscle weakness, and respiratory paralysis requiring mechanical ventilator. Deep tendon reflexes were decreased except for the Achilles reflex. After supportive care, he was weaned from the mechanical ventilator and at discharge 1 month later, his muscle power level and deep tendon reflexes recovered partially. The diagnosis of JE was based on the presence of anti-JE virus IgM in the CSF and seroconversion of IgM and IgG by the ELISA method. Electrophysiological findings were described. From the experience of this case, we caution that a history of vaccination for JE with the Nakayama strain may not provide a complete protection against natural infection in the community; and in Taiwan or any area where JE remains an endemic disease, Japanese virus encephalitis infection should be considered as a differential diagnosis in any adult presenting with acute flaccid paralysis.     

Tick-borne encephalitis: a retrospective study of clinical cases in Bornholm,Denmark

Tick-borne encephalitis (TBE) is caused by a flavivirus, tick-borne encephalitis virus (TBEV). For decades TBE has been known to cause disease in Bornholm, a Danish island. A retrospective study was performed to identify undiagnosed cases of TBE among patients hospitalized with signs and symptoms of meningitis or encephalitis in the 5 y period 1994-1999. This investigation revealed 5 new, and initially undiagnosed cases of TBE. In total, 14 cases of TBE were found in the 7 y period 1994-2000; 2 patients were tourists and 12 cases were inhabitants in Bornholm, giving an incidence of 3.81 per 100,000 inhabitants. At least 5 patients (37.7%) had sequelae in concordance with the postencephalitic syndrome seen after TBE. In conclusion, the risk of being infected and developing TBE is still low among the population of Bornholm, but information about the disease and its sequelae is needed to form a basis for vaccination recommendations.     

Activation of Leukemia Viruses by Graft-Versus-Host and Mixed Lymphocyte Reactions In Vitro

Spleen cells from BALB/c or CAF(1) mice released little or no detectable leukemia virus when cultured 2-7 days in vitro. In contrast, spleen cells of CAF(1) mice previously inoculated with parental BALB/c spleen cells released leukemia viruses in 10 of 11 cases studied. Cultures of a mixture of spleen cells from normal BALB/c and CAF(1) mice also contained leukemia viruses. Phytohemagglutinin induced the transformation of lymphocytes in cultures of CAF(1) or BALB/c spleen cells, but this transformation did not activate leukemia viruses. It is concluded that mixed lymphocyte cultures in vitro, just as graft-versus-host reactions in vivo, can activate leukemia viruses that are normally present in a repressed form. This activation is not solely a function of lymphocyte transformation. The activated mouse leukemia virus may subsequently account for the observed high incidence of neoplasia in graft-versus-host disease.     

A human case of encephalitis associated with vesicular stomatitis virus (Indiana serotype) infection

This paper describes a case of severe encephalitis in a 3-year-old Panamanian boy infected with the Indiana serotype of vesicular stomatitis virus. The virus was recovered from the child's throat on the fifth day of illness and a rise in neutralizing antibody titer was demonstrated in paired serum specimens. This is the second report of childhood encephalitis associated with vesicular stomatitis virus infection. These suggest that infection with vesicular stomatitis viruses may cause severe disease. Human infection with vesicular stomatitis viruses is common throughout the tropical Americas.     

New foci of tick-borne encephalitis virus in Europe: consequences for travellers from abroad

Tick-borne encephalitis (TBE) virus is endemic in many European countries. To assess the risk of infection by TBE virus, maps of TBE foci are a helpful tool for travellers. The TBE reporting system is insufficient in some countries leading to incomplete data, low awareness and underestimation of the risk of infection. In TBE endemic countries with a low vaccine coverage rate, the number of reported TBE cases is increasing and new TBE foci are emerging in a number of European countries. People living in and travellers going into such areas might be more exposed to TBE virus than estimated, based on the current epidemiological maps.     

Leukemia Virus Activation in Chronic Allogeneic Disease

Young adult (BALB/c x A/J)F(1) hybrid mice have no detectable leukemia viruses. When inoculated with parental BALB/c spleen lymphoid cells, also free of detectable virus, leukemia viruses rapidly become activated in the injected host. Because of similarities between such graft-induced allogeneic disease and spontaneous autoimmunity, it is proposed that autoimmune reactions may activate latent viruses.     

Identification of effective constituents of influenza vaccine by immunization with plasmid DNAs encoding viral proteins

The use of plasmid DNA encoding influenza viral proteins to vaccinate animals constitutes a promising approach to the development of effective subunit vaccines. This review describes the results obtained by the immunization of mice with such plasmid DNAs. (i) Both hemagglutinin (HA)- and neuraminidase (NA)-expressing DNAs for the surface glycoproteins from A/PR/8/34 (H1N1) or B/Ibaraki/2/85 virus can provide the most effective protection against influenza A-type or B-type virus infection among the various viral protein-expressing DNAs tested in BALB/c mice. (ii) A mixture of plasmid DNAs encoding HA and NA can provide more effective protection against virus challenge than plasmid DNA encoding HA or NA alone in BALB/c mice. (iii) NA-DNA can provide protection against infection not only by homologous virus but also by drift viruses. (iv) HA-DNA from A/PR/8/34 (H1N1) virus provides significant protection only in BALB/c (H-2(b)) mice, whereas HA-DNA from B/Ibaraki/2/85 virus affords significant protection in BALB/c, B10 (H-2(d)), and C3H (H-2(k)) mice. NA-DNA from both A-type and B-type viruses provides significant protection in the three strains of mice. These results suggest that both HA and NA molecules should be used as vaccine components to provide effective protection against influenza A-type and B-type virus infection in genetically heterogeneous humans.     

Exploratory study on pathogenesis of far-eastern spotted fever

Far-eastern spotted fever is an emerging disease caused by Rickettsia heilongjiangensis, a tick-borne obligate intracellular bacterium. In this study, R. heilongjiangensis was used to infect BALB/c mice by inoculation of retro-orbital venous plexus to imitate a blood infection caused by tick biting. We found that R. heilongjiangensis rapidly entered the circulation for systemic dissemination and the pathogen existed in liver, spleen, lungs, and brain of the mice at least 9 days post-infection (p.i.). Severe pathological lesions were observed in liver, lungs, and brain at Day 6 p.i. In addition, the elevated levels of inflammatory cytokines, including interferon-γ, tumor necrosis factor, and CC chemokine, were detected in the infected organs at Day 3 p.i. Our results reveal that R. heilongjiangensis may cause an infection in BALB/c mice and the pathological lesions in the infected mice are associated with host inflammatory response induced by R. heilongjiangensis.     

Seco-pregnane steroids target the subgenomic RNA of alphavirus-like RNA viruses

Plants have evolved multiple mechanisms to selectively suppress pathogens by production of secondary metabolites with antimicrobial activities. Therefore, direct selections for antiviral compounds from plants can be used to identify new agents with potent antiviral activity but not toxic to hosts. Here, we provide evidence that a class of compounds, seco-pregnane steroid glaucogenin C and its monosugar-glycoside cynatratoside A of Strobilanthes cusia and three new pantasugar-glycosides of glaucogenin C of Cynanchum paniculatum, are effective and selective inhibitors to alphavirus-like positive-strand RNA viruses including plant-infecting tobacco mosaic virus (TMV) and animal-infecting Sindbis virus (SINV), eastern equine encephalitis virus, and Getah virus, but not to other RNA or DNA viruses, yet they were not toxic to host cells. In vivo administration of the compounds protected BALB/c mice from lethal SINV infection without adverse effects on the mice. Using TMV and SINV as models, studies on the action mechanism revealed that the compounds predominantly suppress the expression of viral subgenomic RNA(s) without affecting the accumulation of viral genomic RNA. Our work suggested that the viral subgenomic RNA could be a new target for the discovery of antiviral drugs, and that seco-pregnane steroid and its four glycosides found in the two medicinal herbs have the potential for further development as antiviral agents against alphavirus-like positive-strand RNA viruses.     

Delayed Humoral Immunity in a Patient with Severe Tick-borne Encephalitis after Complete Active Vaccination

Abstract Tick-borne encephalitis virus (TBEV) is a common cause of viral encephalitis in parts of Central and Eastern Europe. Active immunization results in a high rate of seroconversion and is the most effective measure of decreasing the incidence of tick-borne encephalitis (TBE). Currently, booster vaccinations are recommended every 3 years after completion of primary immunization. However, titers of neutralizing antibodies decline with time after vaccination and with age and thus may be insufficient to protect from disease in the elderly. We report on a 54-year-old patient who had received his last booster vaccination 3 years before developing a severe TBE with delayed induction and longterm persistence of anti-TBEV-IgM-antibodies.     

新疆中哈边境地区分离到远东型和西伯利亚型蜱传脑炎病毒

目的研究新疆中哈边境阿拉套山夏尔西里自然保护区蜱传脑炎疫源地病原的基因型及生物学特征。方法采用布旗法采集蜱,活蜱保存或液氮冻存;采用BALB/c小鼠与BHK-21细胞进行蜱传脑炎病毒分离培养;采用RT-PCR扩增蜱传脑炎病毒远东型FE和西伯利亚型S特异基因片段并测定其序列。结果从新疆中哈边境阿拉套山夏尔西里自然保护区全沟硬蜱和森林革蜱中分离出16株蜱传脑炎病毒株,通过对扩增基因序列比对分析,明确其中13株为远东型,3株为西伯利亚型。结论从新疆中哈边境阿拉套山夏尔西里自然保护区分离到远东型和西伯利亚型蜱传脑炎病毒,该地区为两种亚型病毒共存的蜱传脑炎自然疫源地。     

Tick-borne encephalitis: pathogenesis and clinical implications

Tick-borne encephalitis (TBE) is an important and severe neurological illness occurring in large areas of Europe and northern Asia. Only a small proportion of those infected develop clinical symptoms. The symptomatic cases are, however, characterized with fevers and debilitating encephalitis that might progress into chronic disease or fatal infections. This review summarizes data on clinical presentation, pathogenesis and pathology of TBE in humans, and of experimental TBE in animal models with the purpose to explain why is TBE such a severe disease clinically.     

Macrophage impairment underlies airway occlusion in primary respiratory syncytial virus bronchiolitis

Although respiratory syncytial virus (RSV) infection is the most important cause of bronchiolitis in infants, the pathogenesis of RSV disease is poorly described. We studied histopathologic changes in a panel of lung tissue specimens obtained from infants with fatal cases of primary RSV infection. In these tissues, airway occlusion with accumulations of infected, apoptotic cellular debris and serum protein was consistently observed. Similar observations were found after RSV infection in New Zealand black (NZB) mice, which have constitutive deficiencies in macrophage function, but not in BALB/c mice. A deficiency in the number of alveolar macrophages in NZB mice appears to be central to enhanced disease, because depletion of alveolar macrophages in BALB/c mice before RSV exposure resulted in airway occlusion. In mice with insufficient numbers of macrophages, RSV infection yielded an increased viral load and enhanced expression of type I interferon-associated genes at the height of disease. Together, our data suggest that innate, rather than adaptive, immune responses are critical determinants of the severity of RSV bronchiolitis.