Acute disseminated encephalomyelitis following Saint Louis encephalitis virus infection.

Saint Louis encephalitis virus (SLEV) infection is an arbovirosis associated with a broad spectrum of neurological complications. We present a case of a 55-year-old man hailing from Manaus, a city situated in the heart of the Amazon Rainforest, who exhibited symptoms of vertigo, tremors, urinary and fecal retention, compromised gait, and encephalopathy 3 weeks following SLEV infection. Neuroaxis MRI revealed diffuse, asymmetric, and poorly defined margins hyperintense lesions with peripheral and ring enhancement in subcortical white matter, as well as severe spinal cord involvement. Serology for SLEV was positive both on serum and cerebrospinal fluid. To the best of our knowledge, the present report is the first to show brain lesions along with myelitis as a post-infectious complication of SLEV infection.

Phenotypical Screening of an MMV Open Box Library and Identification of Compounds with Antiviral Activity against St. Louis Encephalitis Virus.

St. Louis encephalitis virus (SLEV) is a neglected mosquito-borne Flavivirus that may cause severe neurological disease in humans and other animals. There are no specific treatments against SLEV infection or disease approved for human use, and drug repurposing may represent an opportunity to accelerate the development of treatments against SLEV. Here we present a scalable, medium-throughput phenotypic cell culture-based screening assay on Vero CCL81 cells to identify bioactive compounds that could be repurposed against SLEV infection. We screened eighty compounds from the Medicines for Malaria Venture (MMV) COVID Box library to identify nine (11%) compounds that protected cell cultures from SLEV-induced cytopathic effects, with low- to mid-micromolar potencies. We validated six hit compounds using viral plaque-forming assays to find that the compounds ABT-239, Amiodarone, Fluphenazine, Posaconazole, Triparanol, and Vidofludimus presented varied levels of antiviral activity and selectivity depending on the mammalian cell type used for testing. Importantly, we identified and validated the antiviral activity of the anti-flavivirus nucleoside analog 7DMA against SLEV. Triparanol and Fluphenazine reduced infectious viral loads in both Vero CCL81 and HBEC-5i cell cultures and, similar to the other validated compounds, are likely to exert antiviral activity through a molecular target in the host.

Culex interfor and Culex saltanensis (Diptera: Culicidae) are susceptible and competent to transmit St. Louis encephalitis virus (Flavivirus: Flaviviridae) in central Argentina.

BACKGROUND: St. Louis encephalitis virus (SLEV) is endemic and autochthonous on the American continent. Culex pipiens quinquefasciatus is a vector of SLEV; however, Culex interfor and Culex saltanensis have also been found to be naturally infected with SLEV. The aim of this study was to determine the vector competence of C. interfor and C. saltanensis for SLEV from Argentina compared with C. p. quinquefasciatus. METHODS: Female of the Culex species were orally infected by feeding on viraemic chicks that had been inoculated with SLEV. Abdomens, legs and saliva blood-fed mosquitoes were analysed by viral plaque assay. RESULTS: Mosquitoes were susceptible to orally acquired infection, dissemination and transmission of SLEV in the saliva. CONCLUSIONS: Our results demonstrate that C. saltanensis and C. interfor are susceptible to SLEV and competent for its transmission.

Assessment of Immunoglobulin M Enzyme-Linked Immunosorbent Assay Ratios to Identify West Nile Virus and St. Louis Encephalitis Virus Infections During Concurrent Outbreaks of West Nile Virus and St. Louis Encephalitis Virus Diseases, Arizona 2015.

West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) are closely related mosquito-borne flaviviruses that cause clinical disease ranging from febrile illness to encephalitis. The standard for serological diagnosis is immunoglobulin M (IgM) testing followed by confirmatory plaque reduction neutralization test (PRNT) to differentiate the infecting virus. However, the PRNT is time-consuming and requires manipulation of live virus. During concurrent WNV and SLEV outbreaks in Arizona in 2015, we assessed use of a diagnostic algorithm to simplify testing. It incorporated WNV and SLEV ratios based on positive-to-negative (P/N) values derived from the IgM antibody-capture enzyme-linked immunosorbent assay. We compared each sample's ratio-based result with the confirmed WNV or SLEV sample result indicated by PRNT or PCR testing. We analyzed data from 70 patients with 77 serum and cerebrospinal fluid samples, including 53 patients with confirmed WNV infection and 17 patients with confirmed SLEV infection. Both WNV and SLEV ratios had specificity ≥95%, indicating a high likelihood that each ratio was correctly identifying the infecting virus. The SLEV ratio sensitivity of 30% was much lower than the WNV ratio sensitivity of 91%, likely because of higher cross-reactivity of SLEV antibodies and generation of lower P/N values. The standard for serological diagnosis of WNV and SLEV infections remains IgM testing followed by PRNT. However, these results suggest the ratios could potentially be used as part of a diagnostic algorithm in outbreaks to substantially reduce the need for PRNTs.

Comparison of Characteristics of Patients with West Nile Virus or St. Louis Encephalitis Virus Neuroinvasive Disease During Concurrent Outbreaks, Maricopa County, Arizona, 2015.

West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) are closely related mosquito-borne flaviviruses that can cause neuroinvasive disease. No concurrent WNV and SLEV disease outbreaks have previously been identified. When concurrent outbreaks occurred in 2015 in Maricopa County, Arizona, we collected data to describe the epidemiology, and to compare features of patients with WNV and SLEV neuroinvasive disease. We performed enhanced case finding, and gathered information from medical records and patient interviews. A case was defined as a clinically compatible illness and laboratory evidence of WNV, SLEV, or unspecified flavivirus infection in a person residing in Maricopa County in 2015. We compared demographic and clinical features of WNV and SLEV neuroinvasive cases; for this analysis, a case was defined as physician-documented encephalitis or meningitis and a white blood cell count >5 cells/mm3 in cerebrospinal fluid. In total, we identified 82 cases, including 39 WNV, 21 SLEV, and 22 unspecified flavivirus cases. The comparative analysis included 21 WNV and 14 SLEV neuroinvasive cases. Among neuroinvasive cases, the median age of patients with SLEV (63 years) was higher than WNV (52 years). Patients had similar symptoms; rash was identified more frequently in WNV (33%) neuroinvasive cases than in SLEV (7%) cases, but this difference was not statistically significant (p = 0.11). In summary, during the first known concurrent WNV and SLEV disease outbreaks, no specific clinical features were identified that could differentiate between WNV and SLEV neuroinvasive cases. Health care providers should consider both infections in patients with aseptic meningitis or encephalitis.

Specific diagnostic method for St. Louis encephalitis virus using a non-structural protein as the antigen.

St. Louis encephalitis virus (SLEV) is a mosquito-borne re-emerging flavivirus in Argentina. It is currently necessary to develop specific serological tests that can efficiently discriminate the flaviviruses that circulate in our country. The immunoassays to diagnose SLEV lack specificity because they are based on the detection of structural viral proteins and the human immunoglobulins produced during infection against these proteins cross-react with other flaviviruses. Here, we describe an enzyme-immunoassay designed to detect human IgG antibodies specific to the viral non-structural protein NS5. The results indicate that NS5 is a promising antigen useful to discriminate SLEV from other circulating flaviviruses.

Silent Circulation of the Saint Louis Encephalitis Virus among Humans and Equids, Southeast Brazil.

Saint Louis encephalitis virus (SLEV) is a mosquito-borne flavivirus that occurs throughout the Americas, and is considered a public health threat. In Brazil, SLEV has been detected from human cases associated with dengue-like disease, but no neurological symptoms were reported. Furthermore, the epidemiology of SLEV in human populations is still poorly explored in the country. We reported serological and molecular detection of SLEV in a healthy population of equids and humans from rural areas in Southeast Brazil. A plaque reduction neutralization test was applied, and neutralizing antibodies were detected in 11 individuals (4.6%) and 60 horses (21.5%). A qPCR targeting the 5'UTR region and reverse transcription-PCR (RT-PCR) targeting the non-structural protein (NS5) gene were performed and three individuals tested positive in both assays. Subsequent phylogenetic analysis confirmed SLEV circulation and its findings suggest the occurrence of an asymptomatic or subclinical presence in human and animal cases, correlating with the risks for outbreaks and consequently burden of SLEV infections to public health. Preventive strategies should include improved surveillance in regions with a high probability of SLEV occurrence, improvement in diagnostic methods, and evaluation of exposure/risk factors that can favor SLEV emergence.

Production of recombinant NS1 protein and its possible use in encephalitic flavivirus differential diagnosis.

Saint Louis encephalitis virus (SLEV) and West Nile virus (WNV) are two of the major causes of arboviral encephalitis in the Americas. The co-circulation of related flaviviruses in the Americas and prior vaccination against flaviviruses pose problems to the diagnostic specificity of serological assays due to the development of cross-reactive antibodies. An accurate diagnosis method capable of differentiating these related viruses is needed. NS1 is a glycosylated, nonstructural protein, of about 46 kDa which has a highly conserved structure. Anti-NS1 antibodies can be detected within 4-8 days after the initial exposure and NS1 is the least cross-reactive of the flaviviral antigens. This study was aimed to generate SLEV and WNV NS1 recombinants proteins for the development of a flavivirus diagnostic test. Local Argentinian isolates were used as the source of NS1 gene cloning, expression, and purification. The protein was expressed in Escherichia coli as inclusion bodies and further purified by metal-chelating affinity chromatography (IMAC) under denaturing conditions. Human sera from SLEV and WNV positive cases showed reactivity to the recombinant NS1 proteins by western blot. The unfolded NS1 proteins were also used as immunogens. The polyclonal antibodies elicited in immunized mice recognized the two recombinant proteins with differential reactivity.

Diagnosis of Fatal Human Case of St. Louis Encephalitis Virus Infection by Metagenomic Sequencing, California, 2016.

We used unbiased metagenomic next-generation sequencing to diagnose a fatal case of meningoencephalitis caused by St. Louis encephalitis virus in a patient from California in September 2016. This case is associated with the recent 2015-2016 reemergence of this virus in the southwestern United States.

Saint Louis Encephalitis Virus, another re-emerging arbovirus: a literature review of worldwide research.

Not available.

Encefalitis por virus de Saint Louis: a propósito de un caso / Saint Louis encephalitis: case report

La encefalitis por el virus de Saint Louis es una enfermedad que se transmite a través de mosquitos de la especie Culex.En Argentina, se registran casos esporádicos, habitualmente asintomáticos en niños. Se presenta el caso de una paciente con manifestaciones clínicas inusuales en edad pediátrica y lesiones en el sistema nervioso central no descritas hasta el momento en la literatura. Se trata de una niña de 8 años, que consultó por síndrome febril, cambios conductuales, ataxia, clonus y rigidez de nuca. En el líquido cefalorraquídeo, se detectó pleocitosis predominantemente mononuclear. Se realizó una resonancia magnética, que evidenció imágenes de isquemia bitalámica. La infección por virus de Saint Louis se diagnosticó por IgM en el suero y el líquido cefalorraquídeo. La paciente evolucionó de manera favorable. Al momento del egreso hospitalario, persistía con bradipsiquia y alteraciones conductuales y se recuperó definitivamente 45 días después del alta.

Saint Louis encephalitis is transmitted by Culex mosquitoes. In Argentina sporadic cases are registered. Symptomatic illness is unusual in children. We present a case of meningoencephalitis caused by an uncommon viral infection. The clinical signs and symptoms are unusual for pediatric patients and the bilateral thalamic compromise showed on magnetic resonance has not been described previously. An 8-year-old girl consulted due to fever, behavior disorders and ataxia. Clonus and neck stiffness were detected at physical exam. Cerebrospinal fluid revealed mononuclear leukocytosis; bilateral ischemic compromise was observed in thalamus by magnetic resonance. Saint Louis virus was confirmed by serology: serum and cerebrospinal fluid IgM were positive during the acute phase of the disease and serum IgG was positive four weeks later. Most of the signs and symptoms of the disease were resolved, however mild behavior disorders were observed as acute sequelae up to 45 days after hospital discharge.

[Saint Louis encephalitis: case report]. / Encefalitis por virus de Saint Louis: a propósito de un caso.

Saint Louis encephalitis is transmitted by Culex mosquitoes. In Argentina sporadic cases are registered. Symptomatic illness is unusual in children. We present a case of meningoencephalitis caused by an uncommon viral infection. The clinical signs and symptoms are unusual for pediatric patients and the bilateral thalamic compromise showed on magnetic resonance has not been described previously. An 8-year-old girl consulted due to fever, behavior disorders and ataxia. Clonus and neck stiffness were detected at physical exam. Cerebrospinal fluid revealed mononuclear leukocytosis; bilateral ischemic compromise was observed in thalamus by magnetic resonance. Saint Louis virus was confirmed by serology: serum and cerebrospinal fluid IgM were positive during the acute phase of the disease and serum IgG was positive four weeks later. Most of the signs and symptoms of the disease were resolved, however mild behavior disorders were observed as acute sequelae up to 45 days after hospital discharge.

La encefalitis por el virus de Saint Louis es una enfermedad que se transmite a través de mosquitos de la especie Culex.En Argentina, se registran casos esporádicos, habitualmente asintomáticos en niños. Se presenta el caso de una paciente con manifestaciones clínicas inusuales en edad pediátrica y lesiones en el sistema nervioso central no descritas hasta el momento en la literatura. Se trata de una niña de 8 años, que consultó por síndrome febril, cambios conductuales, ataxia, clonus y rigidez de nuca. En el líquido cefalorraquídeo, se detectó pleocitosis predominantemente mononuclear. Se realizó una resonancia magnética, que evidenció imágenes de isquemia bitalámica. La infección por virus de Saint Louis se diagnosticó por IgM en el suero y el líquido cefalorraquídeo. La paciente evolucionó de manera favorable. Al momento del egreso hospitalario, persistía con bradipsiquia y alteraciones conductuales y se recuperó definitivamente 45 días después del alta.

Monoclonal antibody against Saint Louis encephalitis prM viral protein.

Saint Louis encephalitis virus belongs to Flavivirus genus; Flaviviridae family jointly with other medically important flaviviruses including dengue virus and West Nile virus. The biological properties and functions of prM flavivirus protein are under investigation due to its importance in the generation of infectious virion and host interactions. Monoclonal antibodies have become powerful tools in this approach. Also the use of monoclonal antibodies has been successfully applied for antigenic analysis, clinical diagnosis and treatments. Here, using an immunofluorescence assay we describe a monoclonal antibody (mAb 3D2) that uniquely recognizes native prM Saint Louis encephalitis virus protein expressed in either C6/36-HT or Vero cells. In conclusion, mAb3D2 has significant potential for use in (a) the diagnosis of infections caused by this virus and (b) therapeutic use to treat patients infected by this virus and fundamental research to understand the role of the prM in the Saint Louis encephalitis virus infectious process.

A Saint Louis encephalitis and Rocio virus serosurvey in Brazilian horses.

INTRODUCTION: Arboviruses are an important public health problem in Brazil, in especially flaviviruses, including the Saint Louis encephalitis virus (SLEV) and the Rocio virus (ROCV), are especially problematic. These viruses are transmitted to humans or other vertebrates through arthropod bites and may cause diseases with clinical manifestations that range from asymptomatic infection, viral hemorrhagic fever to encephalitis. METHODS: A serological survey of horses from various regions of Brazil using an enzyme-linked immunosorbent assay (ELISA) with recombinant SLEV domain III peptides and ROCV E protein as antigens. RESULTS: Overall, 415 (55.1%) of the 753 horses that were screened were seropositive for flavivirus and, among them, monotypic reactions were observed to SLEV in 93 (12.3%) and to ROCV in 46 (6.1%). These results suggested that these viruses, or other closely related viruses, are infecting horses in Brazil. However, none of the studied horses presented central nervous system infection symptoms. CONCLUSIONS: Our results suggest that SLEV and ROCV previously circulated among horses in northeast, west-central and southeast Brazil.

Serological evidence for Saint Louis encephalitis virus in free-ranging New World monkeys and horses within the upper Paraná River basin region, Southern Brazil.

INTRODUCTION: Saint Louis encephalitis virus (SLEV) primarily occurs in the Americas and produces disease predominantly in humans. This study investigated the serological presence of SLEV in nonhuman primates and horses from southern Brazil. METHODS: From June 2004 to December 2005, sera from 133 monkeys (Alouatta caraya, n=43; Sapajus nigritus, n=64; Sapajus cay, n=26) trap-captured at the Paraná River basin region and 23 blood samples from farm horses were obtained and used for the serological detection of a panel of 19 arboviruses. All samples were analyzed in a hemagglutination inhibition (HI) assay; positive monkey samples were confirmed in a mouse neutralization test (MNT). Additionally, all blood samples were inoculated into C6/36 cell culture for viral isolation. RESULTS: Positive seroreactivity was only observed for SLEV. A prevalence of SLEV antibodies in sera was detected in Alouatta caraya (11.6%; 5/43), Sapajus nigritus (12.5%; 8/64), and S. cay (30.8%; 8/26) monkeys with the HI assay. Of the monkeys, 2.3% (1/42) of A. caraya, 6.3% 94/64) of S. nigritus, and 15.4% (4/26) of S. cay were positive for SLEV in the MNT. Additionally, SLEV antibodies were detected by HI in 39.1% (9/23) of the horses evaluated in this study. Arboviruses were not isolated from any blood sample. CONCLUSIONS: These results confirmed the presence of SLEV in nonhuman primates and horses from southern Brazil. These findings most likely represent the first detection of this virus in nonhuman primates beyond the Amazon region. The detection of SLEV in animals within a geographical region distant from the Amazon basin suggests that there may be widespread and undiagnosed dissemination of this disease in Brazil.

Infection with Saint Louis encephalitis virus in the city of Ribeirao Preto, Brazil: report of one case.

Saint Louis encephalitis virus (SLEV) is a mosquito-borne flavivirus from the Americas. In this report we describe aspects of the laboratory diagnosis of a patient with an acute febrile illness induced by SLEV that was initially diagnosed as dengue by positive IgM-ELISA. Infection with this virus is probably not rare in Brazil, but cases remain undiagnosed. It is necessary to improve the surveillance system, including laboratories, for the diagnosis of SLEV in Brazil.

A Saint Louis encephalitis and Rocio virus serosurvey in Brazilian horses

Introduction Arboviruses are an important public health problem in Brazil, in especially flaviviruses, including the Saint Louis encephalitis virus (SLEV) and the Rocio virus (ROCV), are especially problematic. These viruses are transmitted to humans or other vertebrates through arthropod bites and may cause diseases with clinical manifestations that range from asymptomatic infection, viral hemorrhagic fever to encephalitis. Methods A serological survey of horses from various regions of Brazil using an enzyme-linked immunosorbent assay (ELISA) with recombinant SLEV domain III peptides and ROCV E protein as antigens. Results Overall, 415 (55.1%) of the 753 horses that were screened were seropositive for flavivirus and, among them, monotypic reactions were observed to SLEV in 93 (12.3%) and to ROCV in 46 (6.1%). These results suggested that these viruses, or other closely related viruses, are infecting horses in Brazil. However, none of the studied horses presented central nervous system infection symptoms. Conclusions Our results suggest that SLEV and ROCV previously circulated among horses in northeast, west-central and southeast Brazil. .