Isolated case of Lassa fever in Zaria, Northern Nigeria

Clinical characterization of Lassa fever: A systematic review of clinical reports and research to inform clinical trial design

BACKGROUND

Research is urgently needed to reduce the morbidity and mortality of Lassa fever (LF), including clinical trials to test new therapies and to verify the efficacy and safety of the only current treatment recommendation, ribavirin, which has a weak clinical evidence base. To help establish a basis for the development of an adaptable, standardised clinical trial methodology, we conducted a systematic review to identify the clinical characteristics and outcomes of LF and describe how LF has historically been defined and assessed in the scientific literature.

METHODOLOGY

Primary clinical studies and reports of patients with suspected and confirmed diagnosis of LF published in the peer-reviewed literature before 15 April 2021 were included. Publications were selected following a two-stage screening of abstracts, then full-texts, by two independent reviewers at each stage. Data were extracted, verified, and summarised using descriptive statistics.

RESULTS

147 publications were included, primarily case reports (36%), case series (28%), and cohort studies (20%); only 2 quasi-randomised studies (1%) were found. Data are mostly from Nigeria (52% of individuals, 41% of publications) and Sierra Leone (42% of individuals, 31% of publications). The results corroborate the World Health Organisation characterisation of LF presentation. However, a broader spectrum of presenting symptoms is evident, such as gastrointestinal illness and other nervous system and musculoskeletal disorders that are not commonly included as indicators of LF. The overall case fatality ratio was 30% in laboratory-confirmed cases (1896/6373 reported in 109 publications).

CONCLUSION

Systematic review is an important tool in the clinical characterisation of diseases with limited publications. The results herein provide a more complete understanding of the spectrum of disease which is relevant to clinical trial design. This review demonstrates the need for coordination across the LF research community to generate harmonised research methods that can contribute to building a strong evidence base for new treatments and foster confidence in their integration into clinical care.

Survival of Lassa Virus in Blood and Tissue Culture Media and in a Small Particle Aerosol

Knowledge of the survival and stability of a pathogen is important for understanding its risk, reducing its transmission, and establishing control measures. Lassa virus is endemic in West Africa, causes severe disease, and is an emerging pathogen of concern. Our study examined the survival of Lassa virus in blood and tissue culture media at two different temperatures. The stability of Lassa virus held within a small particle aerosol was also measured. In liquids, Lassa virus was found to decay more quickly at 30 °C compared to room temperature. Sealed samples protected from environmental desiccation were more stable than samples open to the environment. In a small particle aerosol, the decay rate of Lassa virus was determined at 2.69% per minute. This information can contribute to risk assessments and inform mitigation strategies in the event of an outbreak of Lassa virus.

A Review of Hearing Loss Associated with Zika, Ebola, and Lassa Fever

The neglected tropical diseases Zika, Ebola, and Lassa fever (LF) have all been noted to cause some degree of hearing loss (HL). Hearing loss is a chronic disability that can lead to a variety of detrimental effects, including speech and language delays in children, decreased economic productivity in adults, and accelerated cognitive decline in older adults. The objective of this review is to summarize what is known regarding HL secondary to these viruses. Literature for this review was gathered using the PubMed database. Articles were excluded if there were no data of the respective viruses, postinfectious complications, or conditions related to survivorship. A total of 50 articles were included in this review. Fourteen articles discussing Zika virus and subsequent complications were included. Across these studies, 56 (21.2%) of 264 Zika-infected individuals were found to have HL. Twenty-one articles discussing Ebola virus and subsequent complications were included, with 190 (5.7%) of 3,350 Ebola survivors found to have HL. Fifteen additional articles discussing LF and subsequent complications were included. Of 926 individuals with LF, 79 (8.5%) were found to have HL. These results demonstrate a relationship between HL and infection. The true prevalence is likely underestimated, however, because of lack of standardization of reporting and measurement. Future studies of viral sequelae would benefit from including audiometric evaluation. This information is critical to understanding pathophysiology, preventing future cases of this disability, and improving quality of life after survival of infection.

A vaccine based on recombinant modified Vaccinia Ankara containing the nucleoprotein from Lassa virus protects against disease progression in a guinea pig model

Lassa fever remains the most imported viral haemorrhagic fever in Europe and is responsible for 5000 deaths per year throughout Western Africa. There is no vaccine and treatment is often ineffective. We have developed a vaccine based on modified Vaccinia Ankara expressing the nucleoprotein from Lassa virus (MVALassaNP). This study investigated the immunogenicity (in mice) and efficacy (in guinea pigs) of the MVALassaNP vaccine as a prime/boost or single vaccination regime. ELISA and ELISpot assays confirmed humoral and T-cell immunity following both a prime and prime/boost vaccination, with the prime/boost regime producing a statistically increased response compared to a prime only vaccine (P < 0.0001). The vaccine offered protection in guinea pigs against disease manifestations after challenge with virulent Lassa virus. Clinical signs, weight loss and temperature increases were observed in all animals receiving a control MVA vaccine, after challenge with Lassa virus. In contrast, no clinical signs, fever or weight loss were observed in any of the MVALassaNP vaccinated animals demonstrating that both a single immunisation, and prime/boost regime confer protection against disease progression. In conclusion, the MVALassaNP vaccine candidate elicits an immune response, demonstrates efficacy against Lassa virus disease and is suitable for further preclinical and clinical development.

A rapid research needs appraisal methodology to identify evidence gaps to inform clinical research priorities in response to outbreaks-results from the Lassa fever pilot

BACKGROUND

Infectious disease epidemics are a constant threat, and while we can strengthen preparedness in advance, inevitably, we will sometimes be caught unaware by novel outbreaks. To address the challenge of rapidly identifying clinical research priorities in those circumstances, we developed and piloted a protocol for carrying out a systematic, rapid research needs appraisal (RRNA) of existing evidence within 5 days in response to outbreaks globally, with the aim to inform clinical research prioritization.

METHODS

The protocol was derived from rapid review methodologies and optimized through effective use of pre-defined templates and global time zones. It was piloted using a Lassa fever (LF) outbreak scenario. Databases were searched from 1969 to July 2017. Systematic reviewers based in Canada, the UK, and the Philippines screened and extracted data using a systematic review software. The pilot was evaluated through internal analysis and by comparing the research priorities identified from the data, with those identified by an external LF expert panel.

RESULTS

The RRNA pilot was completed within 5 days. To accommodate the high number of articles identified, data extraction was prioritized by study design and year, and the clinical research prioritization done post-day 5. Of 118 potentially eligible articles, 52 met the data extraction criteria, of which 46 were extracted within the 5-day time frame. The RRNA team identified 19 clinical research priorities; the expert panel independently identified 21, of which 11 priorities overlapped. Each method identified a unique set of priorities, showing that combining both methods for clinical research prioritization is more robust than using either method alone.

CONCLUSIONS

This pilot study shows that it is feasible to carry out a systematic RRNA within 5 days in response to a (re-) emerging outbreak to identify gaps in existing evidence, as long as sufficient resources are identified, and reviewers are experienced and trained in advance. Use of an online systematic review software and global time zones effectively optimized resources. Another 3 to 5 days are recommended for review of the extracted data and to formulate clinical research priorities. The RRNA can be used for a "Disease X" scenario and should optimally be combined with an expert panel to ensure breadth and depth of coverage of clinical research priorities.

Phylogenetic analysis of the Arenaviridae: patterns of virus evolution and evidence for cospeciation between arenaviruses and their rodent hosts

Viruses of the Arenaviridae cause hemorrhagic fevers and neurologic disease in humans. Historically, the arenaviruses have been divided into two complexes (LASV-LCMV, Tacaribe) through the use of antigenic typing. The phylogeny of the Arenaviridae as a whole has not been estimated previously due to a lack of sequence data for all members of the family. In this study, nucleocapsid protein gene sequence data were obtained for all currently known arenaviruses and used to estimate, for the first time, a phylogeny of the entire virus family. The LCMV-LASV complex arenaviruses are monophyletic and comprise three distinct lineages. The Tacaribe complex viruses also are monophyletic and occupy three distinct lineages. Comparisons of arenavirus phylogeny with rodent host phylogeny and taxonomic relationships provide several examples in which virus-host cospeciation is potentially occurring. The pathogenic arenaviruses do not appear to be monophyletic, suggesting that the pathogenic phenotype has arisen in multiple independent events during virus evolution.

Nucleotide sequence of the S RNA of Lassa virus (Nigerian strain) and comparative analysis of arenavirus gene products

The nucleotide sequence of the small (S) genomic RNA of Lassa virus (strain GA391, of Nigerian origin) has been determined. The RNA has features which conform to those seen in most other arenavirus S RNAs which have been characterised, including conserved terminal sequences, an ambisense arrangement of the coding regions for the precursor glycoprotein (GPC) and nucleocapsid (N) proteins and an intergenic region capable of forming a base-paired "hairpin" structure. Comparison of the nucleotide sequence with that of the Josiah strain of Lassa virus (from Sierra Leone) reveals considerable nucleotide divergence in the third base of codons in the reading frames of all three proteins, although the resulting protein sequences are highly conserved, with 92, 94 and 91% identical residues for the mature glycoproteins G1 and G2 and the N protein, respectively. Sequence alignments of the available arenavirus structural proteins and dendrograms summarising the relationships between the viral proteins are presented.

Vaccinia recombinant expressing Lassa-virus internal nucleocapsid protein protects guineapigs against Lassa fever

The Lister strain of vaccinia virus was used to construct a recombinant that expressed the nucleocapsid gene of Lassa virus. Guineapigs immunised with the recombinant virus were protected against challenge with Lassa virus, whereas control animals showed the usual disease course, including pyrexia, anorexia, viraemia, and death. These data indicate not only that protective immunity to Lassa fever can be evoked by an experimental vaccine, but also that this response can be mediated by an internal protein component of the virus.

Molecular cloning of Lassa virus RNA: nucleotide sequence and expression of the nucleocapsid protein gene

Lassa virus RNA isolated from purified virus particles was polyadenylated and reverse transcripts were cloned into the PstI site of plasmid pUC9. Clones containing sequences of the smaller (S) segment of the Lassa virus genome were identified by hybridization with purified S RNA. They were characterized by their ability to hybridize with fragments of 3'-labeled Lassa virus S RNA and with each other, and by restriction mapping. The largest insert was 1830 bp long and began with the 3'-terminal 19-base sequence characteristic of all arenavirus S RNAs so far analyzed. The virus complementary strand contained a single large open reading frame, beginning at the ATG nearest its 5' end (nucleotides 103-5) and terminating with a TGA triplet at position 1813-15, that encodes a protein of 570 amino acids. A recombinant was constructed which expressed the gene as a fusion protein in Escherichia coli. The product was a 60-kDa polypeptide which reacted with monoclonal antibodies specific for the nucleocapsid protein. Comparison of the predicted amino acid sequence with the corresponding sequences deduced from the nucleotide sequences of the other arenavirus S RNAs, lymphocytic choriomeningitis (LCM) and Pichinde, reveals a considerable degree of similarity between Old and New World arenaviruses.

The use of Lassa fever convalescent plasma in Nigeria

Lassa fever convalescent plasma (LFCP) has been administered to 27 patients in hospitals at Jos and Vom, Nigeria. Among serologically or virologically confirmed cases of Lassa fever (LF) given plasma on or before the 10th day, all eight survived, as did two of three possible LF cases. Of eight patients given LFCP after the 10th day, five died, as did all three possible LF cases. LFCP was also administered to five patients subsequently shown not to have LF, and to a suspected case contact; all survived without complications of therapy. There were 15 cases of LF during this time who did not receive plasma; 11 survived. Most cases of LF who received plasma and survived showed a rapid response to therapy, in contrast with the gradual recovery in those who did not receive LFCP.

A case of Lassa fever: experience at St Thomas's Hospital

An 18-year-old Nigerian girl, normally resident in Jos, was admitted to hospital for five days before she was diagnosed as having Lassa fever. There were several atypical features in the early stages of here illness, notably the absence of prostration, pharyngitis, or bradycardia and the development of appreciable leucocytosis. Consequent control and surveillance measures required checks for 21 days on 173 people who had had contact with as first line if they had handled her or specimens without taking precautions to avoid direct skin contact with her excretions, secretions, and blood; other contacts were categorised as second line. During her time in hospital she was managed in a single room on a general ward. She visited a number of investigative departments within the hospital, and her specimens were examined in five clinical laboratories. Despite this no secondary cases occurred among either first- or second-line contacts, and there was no serological evidence of subclinical infection among any of the contacts tested (159 people).