Enhanced methods for unbiased deep sequencing of Lassa and Ebola RNA viruses from clinical and biological samples

We have developed a robust RNA sequencing method for generating complete de novo assemblies with intra-host variant calls of Lassa and Ebola virus genomes in clinical and biological samples. Our method uses targeted RNase H-based digestion to remove contaminating poly(rA) carrier and ribosomal RNA. This depletion step improves both the quality of data and quantity of informative reads in unbiased total RNA sequencing libraries. We have also developed a hybrid-selection protocol to further enrich the viral content of sequencing libraries. These protocols have enabled rapid deep sequencing of both Lassa and Ebola virus and are broadly applicable to other viral genomics studies. Electronic supplementary material The online version of this article (doi:10.1186/s13059-014-0519-7) contains supplementary material, which is available to authorized users

Molecular Diagnostics for Lassa Fever at Irrua Specialist Teaching Hospital, Nigeria: Lessons Learnt from Two Years of Laboratory Operation

Background: Lassa fever is a viral hemorrhagic fever endemic in West Africa. However, none of the hospitals in the endemic areas of Nigeria has the capacity to perform Lassa virus diagnostics. Case identification and management solely relies on non-specific clinical criteria. The Irrua Specialist Teaching Hospital (ISTH) in the central senatorial district of Edo State struggled with this challenge for many years. Methodology/Principal Findings A laboratory for molecular diagnosis of Lassa fever, complying with basic standards of diagnostic PCR facilities, was established at ISTH in 2008. During 2009 through 2010, samples of 1,650 suspected cases were processed, of which 198 (12%) tested positive by Lassa virus RT-PCR. No remarkable demographic differences were observed between PCR-positive and negative patients. The case fatality rate for Lassa fever was 31%. Nearly two thirds of confirmed cases attended the emergency departments of ISTH. The time window for therapeutic intervention was extremely short, as 50% of the fatal cases died within 2 days of hospitalization—often before ribavirin treatment could be commenced. Fatal Lassa fever cases were older (p = 0.005), had lower body temperature (p<0.0001), and had higher creatinine (p<0.0001) and blood urea levels (p<0.0001) than survivors. Lassa fever incidence in the hospital followed a seasonal pattern with a peak between November and March. Lassa virus sequences obtained from the patients originating from Edo State formed—within lineage II—a separate clade that could be further subdivided into three clusters. Conclusions/Significance: Lassa fever case management was improved at a tertiary health institution in Nigeria through establishment of a laboratory for routine diagnostics of Lassa virus. Data collected in two years of operation demonstrate that Lassa fever is a serious public health problem in Edo State and reveal new insights into the disease in hospitalized patients.Organismic and Evolutionary Biolog

Discovery of Novel Rhabdoviruses in the Blood of Healthy Individuals from West Africa

Next-generation sequencing (NGS) has the potential to transform the discovery of viruses causing unexplained acute febrile illness (UAFI) because it does not depend on culturing the pathogen or a priori knowledge of the pathogen’s nucleic acid sequence. More generally, it has the potential to elucidate the complete human virome, including viruses that cause no overt symptoms of disease, but may have unrecognized immunological or developmental consequences. We have used NGS to identify RNA viruses in the blood of 195 patients with UAFI and compared them with those found in 328 apparently healthy (i.e., no overt signs of illness) control individuals, all from communities in southeastern Nigeria. Among UAFI patients, we identified the presence of nucleic acids from several well-characterized pathogenic viruses, such as HIV-1, hepatitis, and Lassa virus. In our cohort of healthy individuals, however, we detected the nucleic acids of two novel rhabdoviruses. These viruses, which we call Ekpoma virus-1 (EKV-1) and Ekpoma virus-2 (EKV-2), are highly divergent, with little identity to each other or other known viruses. The most closely related rhabdoviruses are members of the genus Tibrovirus and Bas-Congo virus (BASV), which was recently identified in an individual with symptoms resembling hemorrhagic fever. Furthermore, by conducting a serosurvey of our study cohort, we find evidence for remarkably high exposure rates to the identified rhabdoviruses. The recent discoveries of novel rhabdoviruses by multiple research groups suggest that human infection with rhabdoviruses might be common. While the prevalence and clinical significance of these viruses are currently unknown, these viruses could have previously unrecognized impacts on human health; further research to understand the immunological and developmental impact of these viruses should be explored. More generally, the identification of similar novel viruses in individuals with and without overt symptoms of disease highlights the need for a broader understanding of the human virome as efforts for viral detection and discovery advance

Molecular diagnostics for lassa fever at Irrua specialist teaching hospital, Nigeria: lessons learnt from two years of laboratory operation.

BACKGROUND: Lassa fever is a viral hemorrhagic fever endemic in West Africa. However, none of the hospitals in the endemic areas of Nigeria has the capacity to perform Lassa virus diagnostics. Case identification and management solely relies on non-specific clinical criteria. The Irrua Specialist Teaching Hospital (ISTH) in the central senatorial district of Edo State struggled with this challenge for many years. METHODOLOGY/PRINCIPAL FINDINGS: A laboratory for molecular diagnosis of Lassa fever, complying with basic standards of diagnostic PCR facilities, was established at ISTH in 2008. During 2009 through 2010, samples of 1,650 suspected cases were processed, of which 198 (12%) tested positive by Lassa virus RT-PCR. No remarkable demographic differences were observed between PCR-positive and negative patients. The case fatality rate for Lassa fever was 31%. Nearly two thirds of confirmed cases attended the emergency departments of ISTH. The time window for therapeutic intervention was extremely short, as 50% of the fatal cases died within 2 days of hospitalization--often before ribavirin treatment could be commenced. Fatal Lassa fever cases were older (p = 0.005), had lower body temperature (p<0.0001), and had higher creatinine (p<0.0001) and blood urea levels (p<0.0001) than survivors. Lassa fever incidence in the hospital followed a seasonal pattern with a peak between November and March. Lassa virus sequences obtained from the patients originating from Edo State formed--within lineage II--a separate clade that could be further subdivided into three clusters. CONCLUSIONS/SIGNIFICANCE: Lassa fever case management was improved at a tertiary health institution in Nigeria through establishment of a laboratory for routine diagnostics of Lassa virus. Data collected in two years of operation demonstrate that Lassa fever is a serious public health problem in Edo State and reveal new insights into the disease in hospitalized patients

Sero-positivity to EKV-1 and EKV-2.

<p>A serosurvey for EKV-1 and EKV-2 was performed on Nigerian samples (n = 320). Cut-off values were based on the mean of US normals (n = 137) plus either 3xSD or 5xSD (SD = standard deviation).</p><p>Sero-positivity to EKV-1 and EKV-2.</p

Examples of rhabdoviruses reported in Africa.

<p>A map depicting examples of rhabdoviruses isolated in sub-Saharan Africa. This map does not depict the current distribution of rhabdoviruses in Sub-Saharan Africa, nor is it meant as a comprehensive listing of all rhabdoviruses isolated in Africa; rather its purpose is to illustrate that many rhabdoviruses have been discovered throughout Africa over the past half-century. Country refers to the sample’s country of origin. Abbreviations: CAR, Central African Republic; DRC, Democratic Republic of Congo.</p

Sequencing results and schematic representation of the EKV-1 and -2 genome organization.

<p>(<b>A</b>) Overview of the data generated for each novel rhabdovirus. (<b>B</b>) A schematic showing the assembled genomes, consisting of the following genes: <i>nucleoprotein</i> (N), <i>phosphoprotein</i> (P), <i>matrix</i> (M), <i>U1</i>/<i>U2</i>/<i>U3</i> (uncharacterized accessory proteins), <i>glycoprotein</i> (G), and <i>polymerase</i> (L). We indicate in orange (EKV-1) and blue (EKV-2) segments of the viral genomes that could not be assembled from Illumina reads and instead Sanger sequenced. (<b>C</b>) Coverage plots of the final viral genomes.</p

Box-plot representation of statistically significant differences between survivors and fatal cases of Lassa fever.

<p>Urea and creatinine blood levels were drawn at admission. Comparison of unpaired groups was performed with the Mann-Whitney test. The number of cases per group is given below the plots in parentheses.</p

Virological and clinical data for Lassa fever patients.

<p>Due to a variable number of missing values, the number (n) of data points that were included in the analysis is indicated with each category.</p><p>Abbreviations:</p>a<p>Patients who were discharged after recovery.</p>b<p>Patients who died during hospitalization.</p>c<p>1+, Lassa virus RT-PCR was only positive with undiluted plasma; 2+, Lassa virus RT-PCR was positive with 1/10-volume plasma, irrespective of whether the undiluted sample was positive or not.</p>#<p>p<0.01 (PCR-positive survived vs. PCR-positive died).</p

Geographic origin of Lassa fever cases.

<p>Top: Map of the southern part of Nigeria showing location of Edo State. Most of the samples came from Edo State and the neighboring Ondo State. FCT, Federal Capital Territory. Bottom: Map of Edo State with borders of the Local Governmental Areas (LGA). LGAs with confirmed Lassa fever cases are shaded from light to dark grey depending on the number of cases. The names of the LGAs with case number in parentheses are given below the map.</p