Cross reactivity of neutralizing antibodies to the encephalitic California Serogroup orthobunyaviruses varies by virus and genetic relatedness.

The California Serogroup (CSG) of Orthobunyaviruses comprises several viruses capable of causing neuroinvasive disease in humans, including La Crosse (LACV), Snowshoe Hare (SSHV), Tahyna (TAHV), Jamestown Canyon (JCV), and Inkoo (INKV) viruses. Diagnosis of specific CSG viruses is complicated by the high degree of antibody cross-reactivity between them, with laboratory standards requiring a fourfold higher titer of neutralizating antibody (NAb) activity to positively identify the etiologic virus. To help elucidate NAb relationships between neuroinvasive CSG viruses, we directly compared the cross-reactivity of NAb between LACV, SSHV, TAHV, JCV, and INKV. Mice were inoculated with individual viruses and the NAb activity of plasma samples was compared by plaque reduction neutralization tests against all five viruses. Overall, the results from these studies show that the CSG viruses induced high levels of NAb against the inoculum virus, and differing amounts of cross-reactive NAb against heterologous viruses. LACV, SSHV, and INKV elicited the highest amount of cross-reactive NAb. Interestingly, a fourfold difference in NAb titer between the inoculum virus and the other CSG viruses was not always observed. Thus, NAb titers, which are the gold-standard for diagnosing the etiologic agent for viral encephalitis, may not clearly differentiate between different CSG viruses.

Seroprevalence of Jamestown Canyon virus in the Japanese general population.

BACKGROUND: Jamestown Canyon virus (JCV) is a mosquito-borne orthobunyavirus that causes acute febrile illness, meningitis, and meningoencephalitis, mainly among adults. JCV is widely distributed in North America and the number of JCV cases in the U.S. has increased in recent years. Therefore, the central nervous system disease caused by JCV can be considered a potentially re-emerging viral disease. However, the seroprevalence of JCV is unknown in Japan. The purpose of this study is to evaluate the seroprevalence of JCV in the Japanese population. METHODS: We used an IgG enzyme-linked immunosorbent assay (IgG-ELISA) with JCV-infected cell-lysates and/or a neutralizing (NT) antibody assay. The cut-off value of IgG-ELISA was determined using IgG-ELISA to analyze serum specimens from 37 healthy Japanese donors. IgG-ELISA was validated by assessing its sensitivity and specificity, using 38 human serum samples previously tested for the presence or absence of antibodies against JCV and snowshoe hare virus (SSHV), in an in-house NT antibody assay conducted by the Public Health Agency of Canada. The seroepidemiological study was performed using IgG-ELISA and NT antibody assay to analyze 246 human serum samples from the serum bank of the National Institute of Infectious Diseases (NIID) in Japan. RESULTS: The cut-off value of IgG-ELISA was determined at 0.20, based on the mean (- 0.075) and standard deviation (0.092) values using Japanese donors' sera. The sensitivity and the specificity of IgG-ELISA determined using 25 JCV-positive and 4 JCV-negative serum samples were 96 and 100%, respectively. Analysis of the 246 Japanese serum samples revealed that no specimen showed a higher value than the cut-off value of IgG-ELISA, and no sample tested positive by the NT antibody assay. CONCLUSIONS: Our results showed that JCV is not circulating significantly in Japan. To the best of our knowledge, this is the first report to demonstrate the seroprevalence of JCV in the general population in Japan.

Jamestown Canyon virus in Massachusetts: clinical case series and vector screening.

Jamestown Canyon virus (JCV) is a neuroinvasive arbovirus that is found throughout North America and increasingly recognized as a public health concern. From 2004 to 2012, an average of 1.7 confirmed cases were reported annually in the United States, whereas from 2013 to 2018 this figure increased over seventeen-fold to 29.2 cases per year. The rising number of reported human infections highlights the need for better understanding of the clinical manifestations and epidemiology of JCV. Here, we describe nine patients diagnosed with neuroinvasive JCV infection in Massachusetts from 2013, the year of the first reported case in the state, to 2017. Because current diagnostic testing relies on serology, which is complicated by cross-reactivity with related orthobunyaviruses and can be negative in immunosuppressed patients, we developed and evaluated an RT-qPCR assay for detection of JCV RNA. We tested this on the available archived serum from two patients, but did not detect viral RNA. JCV is transmitted by multiple mosquito species and its primary vector in Massachusetts is unknown, so we additionally applied the RT-qPCR assay and confirmatory RNA sequencing to assess JCV prevalence in a vector candidate, Ochlerotatus canadensis. We identified JCV in 0.6% of mosquito pools, a similar prevalence to neighboring Connecticut. We assembled the first Massachusetts JCV genome directly from a mosquito sample, finding high identity to JCV isolates collected over a 60-year period. Further studies are needed to reconcile the low vector prevalence and low rate of viral evolutionary change with the increasing number of reported cases.

Enhanced Arboviral Surveillance to Increase Detection of Jamestown Canyon Virus Infections, Wisconsin, 2011-2016.

Jamestown Canyon virus (JCV), a mosquito-borne Orthobunyavirus (within the California serogroup), can cause severe neuroinvasive disease. According to national data during 2000-2013, 42% of the 31 documented JCV disease cases in the United States were detected in residents from Wisconsin. The Wisconsin Division of Public Health enhanced JCV surveillance by implementing routine use of JCV-specific immunoglobulin M (IgM) antibody testing followed by confirmatory JCV-specific plaque reduction neutralization testing on all patients with suspected cases of arboviral infection who had tests positive for arboviral immunoglobin at commercial laboratories. During 2011-2016, of the 287 Wisconsin specimens tested on the Arbovirus IgM Antibody Panel, 30 JCV cases were identified (26 confirmed and four probable). Twenty-seven (90%) JCV cases were detected after 2013. Among all cases, 17 (56%) were male and the median age was 54 years (range: 10-84 years). Fifteen patients had neuroinvasive disease, including meningitis (n = 9) and meningoencephalitis (n = 6). Although historically considered rare, the relatively high rate (0.12 cases/100,000 population) of diagnosis of JCV infections among Wisconsin residents during 2013-2016 compared with that in previous years suggests occurrence is widespread throughout Wisconsin and historically may have been under-recognized. This study aims to raise awareness of JCV infection for differential diagnosis among the arboviral diseases. Improved and timely diagnosis of arboviral disease is important in that it will provide more information regarding emerging infections and promote preventive measures to avoid mosquito-borne exposure and infection among residents of and visitors to affected areas.

Serological surveillance for Tahyna virus (California encephalitis orthobunyavirus, Peribunyaviridae) neutralizing antibodies in wild ungulates in Austria, Hungary and Romania.

A serosurvey for Tahyna virus (TAHV), a mosquito-borne California encephalitis orthobunyavirus (Peribunyaviridae) endemic to Europe, was performed to estimate the activity of TAHV on a broad geographic scale. Sera from wild boar (Sus scrofa), roe deer (Capreolus capreolus) and red deer (Cervus elaphus) were collected from Austria, Hungary and Romania. Samples were tested for neutralizing antibodies against TAHV using a virus microneutralization assay. The results demonstrate that TAHV transmission to mammals is widespread in Europe, particularly in the wild boar population where the mean rate of seroconversion is 15.2%.

California Serogroup Virus Infection Associated with Encephalitis and Cognitive Decline, Canada, 2015.

California serogroup (CSG) viruses, such as Jamestown Canyon and snowshoe hare viruses, are mosquitoborne pathogens that cause febrile illness and neurologic disease. Human exposures have been described across Canada, but infections are likely underdiagnosed. We describe a case of neuroinvasive illness in a New Brunswick, Canada, patient infected with a CSG virus.

Investigations on California serogroup orthobunyaviruses in the Tyrols: first description of Tahyna virus in the Alps.

Seroprevalence rates for immunoglobulin G (IgG) antibodies to Tahyna virus (TAHV) and Inkoo virus (INKV) were determined in sera of 1630 blood donors from North, East, and South Tyrol by immunofluorescence assays (IFAs) and confirmatory serum neutralization tests (SNTs). Ten sera (0.6%) reacted positive by TAHV IFA, five of which (0.3%) were confirmed by SNT. Eleven sera (0.7%) reacted positive in the INKV IFA; only one thereof (0.06%) was verified by subsequent SNT. To identify the source of infections, mosquitoes were trapped at 18 sampling sites in the study area, resulting in the collection of 2571 adult mosquitoes: 1254 individuals of the genus Aedes (48.8% of total) including A. albopictus, 640 Culex (24.9%), 303 Coquillettidia (11.8%), 252 Ochlerotatus (9.8%), 49 Anopheles (1.9%), and 73 mosquitoes of the genus Culiseta (2.8%). The mosquitoes were pooled according to species, trapping site, and time, and were tested by RT-PCR for the presence of California serogroup orthobunyavirus nucleic acids. PCR amplification products were obtained in five of 195 pools (2.6%), and all were identified as TAHVs by subsequent sequencing. This represents the first evidence of TAHV circulation and human exposure in the Tyrols and in the alpine region in general. Interestingly, all TAHV sequences were identified in Culex pipiens/torrentium mosquitoes. Whether other California serogroup orthobunyaviruses such as INKV are also circulating in this area is subject of further investigations on larger numbers of mosquitoes.

Roles of host species, geographic separation, and isolation in the seroprevalence of Jamestown Canyon and snowshoe hare viruses in Newfoundland.

California serogroup viruses, including Jamestown Canyon virus (JCV) and snowshoe hare virus (SSHV), are mosquito-borne members of the Bunyaviridae family and are endemic across North America. These arboviruses are potential pathogens which occasionally cause neuroinvasive disease in humans and livestock. A neutralization assay was used to document JCV and SSHV seroprevalence using blood collected from a variety of domestic and wildlife host species. These species were sampled in an island setting, Newfoundland, which contains diverse ecoregions, ecological landscapes, and habitats. Seroprevalence rates for each virus differed significantly among host species and within certain species across different geographic areas. JCV was significantly associated with large mammals, and SSHV was significantly associated with snowshoe hares. Seroprevalence rates in the 5 species of animals tested for prior exposure to JCV ranged from 0% in snowshoe hares to 64% in horses. Seroprevalence rates for SSHV ranged from less than 1% in bovines to 55% in all snowshoe hares. The seroprevalence of SSHV differed significantly (P < 0.05) among hares occupying the discrete habitats of watersheds separated by 14 to 35 km. Cattle on farms in boreal forest landscapes displayed significantly higher JCV seroprevalence (P < 0.001) than those on farms located in seacoast landscapes. Lifelong geographic isolation of cattle to insular Newfoundland was associated with significantly lower JCV seroprevalence (P < 0.01) than that for cattle which had lived off-island.

[Investigation of Tahyna virus infection among unknown fever cases in Xinjiang, China].

To investigate the infection status and the spatial distribution of Tahyna virus infection among unknown fever cases in Xinjiang, China. Sera samples of unknown fever cases from Kashi in southern Xin-jiang and Yili in northern Xinjiang were tested against Tahyna virus by IFA. Partial positive cases were tested against Tahyna virus/Snowshoe hare virus/Inkoo virus parrelled. Finally, 742 sera samples of unknown fever cases were collected from Kashi, Southern Xinjiang in 2007-2008, the positive rate of IgM antibody against Tahyna virus was 5.3%, the positive rate of IgG antibody against Tahyna virus was 18.3%. 222 sera samples of unknown fever cases were collected from Yili, Northern Xinjiang in 2008, no positive case of IgM antibody against Tahyna was found. 10 cases showed antibody neutralization against Tahyna virus by plaque reduction neutralization test. Our results demonstrate that there is current infection and past infection of Tahyna virus among Southern Xinjiang residents.

Tahyna virus genetics, infectivity, and immunogenicity in mice and monkeys.

BACKGROUND: Tahyna virus (TAHV) is a human pathogen of the California encephalitis virus (CEV) serogroup (Bunyaviridae) endemic to Europe, Asia, and Africa. TAHV maintains an enzootic life cycle with several species of mosquito vectors and hares, rabbits, hedgehogs, and rodents serving as small mammal amplifying hosts. Human TAHV infection occurs in summer and early fall with symptoms of fever, headache, malaise, conjunctivitis, pharyngitis, and nausea. TAHV disease can progress to CNS involvement, although unlike related La Crosse virus (LACV), fatalities have not been reported. Human infections are frequent with neutralizing antibodies present in 60-80% of the elderly population in endemic areas. RESULTS: In order to determine the genomic sequence of wild-type TAHV, we chose three TAHV isolates collected over a 26-year period from mosquitoes. Here we present the first complete sequence of the TAHV S, M, and L segments. The three TAHV isolates maintained a highly conserved genome with both nucleotide and amino acid sequence identity greater than 99%. In order to determine the extent of genetic relatedness to other members of the CEV serogroup, we compared protein sequences of TAHV with LACV, Snowshoe Hare virus (SSHV), Jamestown Canyon virus (JCV), and Inkoo virus (INKV). By amino acid comparison, TAHV was most similar to SSHV followed by LACV, JCV, and INKV. The sequence of the GN protein is most conserved followed by L, N, GC, NSS, and NSM. In a weanling Swiss Webster mouse model, all three TAHV isolates were uniformly neurovirulent, but only one virus was neuroinvasive. In rhesus monkeys, the virus was highly immunogenic even in the absence of viremia. Cross neutralization studies utilizing monkey immune serum demonstrated that TAHV is antigenically distinct from North American viruses LACV and JCV. CONCLUSIONS: Here we report the first complete sequence of TAHV and present genetic analysis of new-world viruses, LACV, SSHV, and JCV with old-world viruses, TAHV and INKV. Using immune serum generated in monkeys against TAHV, LACV, and JCV, we have demonstrated cross-neutralization within the CEV serogroup. Such cross reactivity may complicate virus identification, especially following JCV infection which elicited antibodies that cross neutralized both LACV and TAHV. These data also suggest that a single vaccine could generate a cross-neutralizing antibody response which may provide protection against CEV serogroup viruses from a wide geographic range.

Mosquitoes and mosquito-borne arboviruses in the Qinghai-Tibet Plateau--focused on the Qinghai area, China.

An investigation was conducted to identify the distribution of mosquitoes and mosquito-borne arboviruses in the Qinghai-Tibet Plateau, China from July to August in 2007. A total of 8,147 mosquitoes representing six species from three genera (Aedes, Culex, and Anopheles) were collected in three locations (Geermu city, altitude of 2,780 m; Xining city, 2,200 m; Minhe county, 1,700 m). Six virus isolates were obtained including Tahyna virus (TAHV), Liaoning virus, and Culex pipiens pallens Densovirus. A serosurvey showed immunoglobulin G antibodies by immunofluorescence assay (IFA) against TAHV in residents of all three locations. The IFA-positive human samples were confirmed by 90% plaque-reduction neutralization tests (PRNT(90)) against TAHV with titers ranging from 1:20 to 1:10,240. In addition, TAHV seropositive cows, sheep, and swine were found in these locations. This investigation represents the first isolation of TAHV from Ae. (Och.) detritus and the first evidence of TAHV infection in residents and livestock in the Qinghai-Tibet Plateau.

Tahyna virus and human infection, China.

In 2006, Tahyna virus was isolated from Culex spp. mosquitoes collected in Xinjiang, People's Republic of China. In 2007, to determine whether this virus was infecting humans, we tested serum from febrile patients. We found immunoglobulin (Ig) M and IgG against the virus, which suggests human infection in this region.

[Adverse immunologic effects of immunomodulators revealed in experiment and ways to their surmounting].

Immunomodulators licopid (synthetic analogue of muramylpeptide) and purified staphylococcal toxoid (PST) in some variants of experiments on mice caused adverse immunologic effects: enhancement of virus-induced immunosupression, shift from latent immunosupression (revealed only by low, but not standard, doses of test-antigen) to manifested one. Described adverse effects are not a contraindication for use of the studied drugs in practice. Their adverse effects were revealed only after single inoculation, whereas in clinical conditions PST and licopid are used by courses with duration of 5-7 and 10 days respectively. Our experiments show that inoculation of suppressive doses of the preparations repeated by 2-4 times can prevent the shift from latent to manifested immunosupression. Enhancement of immunosupression was not observed in case of combined administration of suppressive doses of PST and adjuvant dose of licopid.

Micromodification of virus-neutralisation assay with vital staining in 96-well plate and its use in diagnostics of Tahyna virus infections.

Virus neutralization test (VNT) is considered to be the gold standard for arbovirus serology because of its high specificity and sensitivity. Its micromodification in 96-well plate with vital staining of cell cultures was developed in the National Reference Laboratory (NRL) for Arboviruses of the Czech Republic and is used for the detection of specific antibodies against various viruses, mainly arboviruses. The test procedure is described for the Tahyna virus micromodified neutralization assay in 96-well plate. Results of an anti-Tahyna antibody survey conducted among the population of northern Moravia using the VNT assay are presented. The overall anti-Tahyna seroprevalence among 1001 tested persons was 3.80%. The highest positivity rate was found in persons aged over 59 years (17.53%) comparing to children with the seroprevalence rates of 0.00% and 0.56% in the age groups 0-5 years and 6-14 years, respectively.

[Isolation of influenza virus A (Orthomyxoviridae, Influenza A virus), Dhori virus (Orthomyxoviridae, Thogotovirus), and Newcastle's disease virus (Paromyxoviridae, Avulavirus) on the Malyi Zhemchuzhnyi Island in the north-western area of the Caspian Sea].

The paper presents the results of the 2003 and 2006 environmental virological monitoring surveys on the Malyi Zhemchuzhnyi Island where a large breeding colony of sea gull (Laridae) is located. In the past several years, expansion of cormorants (Phalacrocorax carbo) has enhanced the intensity of populational interactions. The investigators isolated 13 strains of influenza A virus (Orthomyxoviridae, Influenza A virus) subtype H13N1 (from sea gulls (n = 4), cormorants (n = 9) 1 strain of Dhori virus (Orthomyxoviridae, Thogotovirus) from a cormorantwith clinical symptoms of the disease, 3 strains of Newcastle disease virus (Paramyxoviridae, Avulavirus) from cormorants. RT-PCR revealed influenza A virus subtype H5 in 3.1% of the cloacal lavages from cormorants. Neutralization test indicated that sera from cormorants contained specific antibodies against West Nile (Flaviviridae, Flavivirus) (15.0%), Sindbis (Togaviridae, Alphavirus) (5.0%), Dhori (10.0%), and Tahini (Bunyaviridae, Orthobunyavirus) (5.0%); sera from herring gulls had antibodies against Dhori virus (16.7%); there were no specific antibodies to Inco (Bunyaviridae, Orthobunyavirus) and mountain hare (Lepus timidus) (Bunyaviridae, Orthobunyavirus) virus.

Seroprevalence of tick-borne and mosquito-borne arboviruses in European brown hares in Northern and Western Germany.

Tríbec virus (Kemerovo serogroup, genus Orbivirus), Eyach virus (genus Coltivirus), and Tahyna virus (California encephalitis serogroup, genus Bunyavirus) are arthropod-borne viruses known to occur in Germany. These viruses are also suspected to cause human disease. So far, no information is available on their geographical distribution in Germany and their natural transmission cycles. A total of 166 sera from European brown hares (Lepus europaeus) collected in seven districts of the Federal State of Schleswig-Holstein and in four districts of the Federal State of North Rhine-Westphalia was tested by plaque reduction neutralization test (PRNT) for antibodies against Tríbec virus, Eyach virus, Tahyna virus, and Central European encephalitis virus. One out of 22 sera (4.5%) collected in the district Nord-Friesland in Schleswig-Holstein was found positive (PRNT(90) 1:10) against Tríbec virus. Neither did sera from other regions of Schleswig-Holstein nor from hares from North Rhine-Westphalia react against any of the arboviruses tested. For the first time, antibodies against Tríbec virus could be found in a European brown hare in Germany. The negative serological results for Central European encephalitis virus are in line with the current knowledge of its natural distribution within Germany. The negative serological results for Tahyna virus or Eyach virus argue against an autochthonous circulation of these viruses in the regions tested.

[The ecology and prevalence of arboviruses on the territory of the Saratov Region].

The territorial spread of Tahyna, Batai, Sindbis, West Nile fever and Crimean-Congo hemorrhagic fever viruses throughout the Saratov region in 1998 - 2000 was analyzed. The characteristics of the epizootic activity of the natural foci of these arboviruses in different landscape zones (temperate forest-steppes, steppes and semi-deserts) were calculated. The species composition of small mammals, the natural reservoirs of the causative agents of arbovirus infections, was determined.

Mosquitoborne viruses, Czech Republic, 2002.

Specimens from residents (N = 497) of an area affected by the 2002 flood were examined serologically for mosquitoborne viruses. Antibodies were detected against Tahyna (16%), Sindbis (1%), and Batai (0.2%) viruses, but not West Nile virus. An examination of paired serum samples showed 1 Tahyna bunyavirus (California group) infection.

[Antibodies against mosquito-born viruses in human population of an area of Central Bohemia affected by the flood of 2002]. / Protilátky k virum prenosným komáry u stredoceské populace z oblasti zasazené povodní v roce 2002.

In the Central-Bohemian area affected by the flood of 2002, 497 residents were screened for antibodies against the mosquito-borne viruses Tahyna (TAHV), West Nile (WNV), Sindbis (SINV) and Batai (BATV; syn. Calovo) using the haemagglutination-inhibition (HIT) and plaque-reduction neutralization (PRNT) tests. Blood samples were collected in September 2002 when the mosquito populations showed the maximum density following the flood. Antibodies against TAHV (16.5% persons in PRNT, 14.9% in HIT), SINV (1.4% in HIT) and BATV (1.4% in HIT, 0.2% in PRNT) were detected. Although 6.8% and 1.2% of the subjects tested reactive with WNV in HIT and PRNT, respectively, the results were interpreted as cross-reactivity with tick-borne encephalitis virus. The seroprevalence of TAHV (both in PRNT and HIT) showed no association with gender (15.8% of males, 16.9% of females), increased with age (1.4% of persons younger than 20 years, 11.2% of persons aged between 20 and 50 years, and 26.2% of persons older than 50 years were positive), and correlated with the mosquito peri-residential challenge (5.0% residents seropositive in a mosquito-free control zone D--mostly Prague, 14.7% in a mild-risk zone C, 20.5% in a moderate-risk zone B, and 28.0% in the most heavily mosquito-infested risk zone A). The highest TAHV seropositivity rate (> 25%) was found amongst the inhabitants of the villages Obríství, Kozly, Tuhan, Chrást, Chlumín and Hostín. Paired blood samples were obtained from 150 of the persons at a 6-month interval: an infection episode with TAHV during or after the flood was clearly evidenced in one person living in Obríství, and less convincing findings of recent TAHV infections were found in other three residents of Chlumín and Obríství (seroconversion and/or significant antibody titres increase detected in HIT only). This serosurvey indicated the existence of an active natural focus of Valtice fever (TAHV infection) stretched along the river Labe nearby Neratovice (Obríství, Chlumín, Tuhan; Kozly, Tisice, Chrást), and a low TAHV activity area along the lower reaches of the river Vltava between Zloncice and Bukol/Zálezlice. An increased population density of mosquitoes after the flood may have boosted the incidence of mosquito-borne virus diseases, particularly Valtice fever, in Central Bohemia. An optimum prophylactic strategy to control these diseases would be epidemiological surveillance (including monitoring of both the density of mosquitoes and their rate of infection with viruses in natural foci) on the basis of which antiepidemic measures such as integrated mosquito control can be taken.