What Pediatricians Should Know About Lassa Virus

Understanding Immune Responses to Lassa Virus Infection and to Its Candidate Vaccines

Lassa fever (LF) is a deadly viral hemorrhagic fever disease that is endemic in several countries in West Africa. It is caused by Lassa virus (LASV), which has been estimated to be responsible for approximately 300,000 infections and 5000 deaths annually. LASV is a highly pathogenic human pathogen without effective therapeutics or FDA-approved vaccines. Here, we aim to provide a literature review of the current understanding of the basic mechanism of immune responses to LASV infection in animal models and patients, as well as to several of its candidate vaccines.

Pathogenicity and virulence mechanisms of Lassa virus and its animal modeling, diagnostic, prophylactic, and therapeutic developments

Lassa fever (LF) is a deadly viral hemorrhagic disease that is endemic to West Africa. The causative agent of LF is Lassa virus (LASV), which causes approximately 300,000 infections and 5,000 deaths annually. There are currently no approved therapeutics or FDA-approved vaccines against LASV. The high genetic variability between LASV strains and immune evasion mediated by the virus complicate the development of effective therapeutics and vaccines. Here, we aim to provide a comprehensive review of the basic biology of LASV and its mechanisms of disease pathogenesis and virulence in various animal models, as well as an update on prospective vaccines, therapeutics, and diagnostics for LF. Until effective vaccines and/or therapeutics are available for use to prevent or treat LF, a better level of understanding of the basic biology of LASV, its natural genetic variations and immune evasion mechanisms as potential pathogenicity factors, and of the rodent reservoir-vector populations and their geographical distributions, is necessary for the development of accurate diagnostics and effective therapeutics and vaccines against this deadly human viral pathogen.

Lassa Fever among Children in Eastern Province, Sierra Leone: A 7-year Retrospective Analysis (2012-2018)

Pediatric Lassa fever (LF) usually presents as a nonspecific febrile illness, similar to other endemic diseases in countries like Sierra Leone, where LF is considered to be hyperendemic. The nonspecificity of presentation and lack of research have made it difficult to fully understand best practices for pediatric management. We aim to describe clinical characteristics of hospitalized pediatric patients suspected or diagnosed with LF and assess factors associated with hospital outcomes among those with LF antigen-positive results. We conducted a 7-year retrospective cohort study using routine data for all children younger than 18 years admitted at the Kenema Government Hospital's LF ward. A total of 292 children with suspected or confirmed LF were analyzed. Overall, mortality was high (21%). Children with antigen-positive results had a high case fatality rate of 63% (P < 0.01). In univariate analyses, children who presented with unexplained bleeding (odds ratio [OR]: 3.58; 95% CI: 1.08-11.86; P = 0.040) and confusion (altered sensorium) (OR: 5.37; 95% CI: 1.34-21.48; P = 0.020) had increased odds of death. Abnormal serum levels of alanine aminotransferase (P = 0.001), creatinine (P = 0.004), and potassium (P = 0.003) were associated with increased likelihood of death in these children. Treatment with ribavirin was not significantly associated with survival (P = 0.916). Our findings provide insights into current pediatric LF clinical presentation and management. More evidence-based, high-quality research in creating predictive algorithms of antigen-positivity and hospital outcomes is needed in the management of pediatric LF.

Monitoring of Lassa virus infection in suspected and confirmed cases in Ondo State, Nigeria

Introduction

Lassa virus (LASV), the causative agent of Lassa fever (LF), an endemic acute viral haemorrhagic illness in Nigeria, is transmitted by direct contact with the rodent, contaminated food or household items. Person-to-person transmission also occurs and sexual transmission has been reported. Thus, this study investigated the presence of LASV in body fluids of suspected and confirmed cases.

Methods

this was a cross-sectional study between March 2018 and April 2019 involving 112 consenting suspected and post ribavirin confirmed cases attending the Lassa fever treatment center in Ondo State. Whole blood was collected from 57 suspected and 29 confirmed cases. Other samples from confirmed cases were 5 each of High Vaginal Swab (HVS) and seminal fluid; 12 breast milk and 4 urine. All samples were analyzed using reverse transcription-PCR (RT-PCR) targeting the S-gene of LASV.

Results

analysis of whole blood by RT-PCR showed that 1/57 (1.8%) suspected and 1/29 (3.4%) confirmed post ribavirin treated cases were positive. While LASV was detected in 2/5 (40%) post ribavirin treated seminal fluids and 1/11 (8.3%) breast milk. However, LASV was not detected in any of the HVS and urine samples.

Conclusion

the detection of LASV in seminal fluid and breast milk of discharged post ribavirin treated cases suggests its persistence in these fluids of recovering Nigerians. The role of postnatal and sexual transmissions in the perennial outbreak of LF needs to be further evaluated.

The function annotations of ST3GAL4 in human LAMP1 and Lassa virus GP-C interaction from the perspective of systems virology

Lassa virus (LASV) is a single-stranded RNA virus that has plagued the Sub-Saharan part of Africa, precisely Nigeria where various pathogenic strains with varied genomic isoforms have been identified. The human lysosomal-associated membrane protein 1 (LAMP1) is alternately required for the micropinocytosis of LASV. Therefore, it is of interest to understand the mechanism of action of the host LAMP1 with LASV protein during infection. The role of ST3 beta-galactoside alpha-2, 3-sialyltransferase 4 (ST3GAL4) in the interaction between LASV (glycoprotein) GP-C and the human LAMP1 is relevant in this context. Deposited curated protein sequences of both LAMP1 and LASV GP-C were retrieved for the study. The ST3GAL4 associated data was constructed and analysed from weighted network analysis to infer the function annotations and molecular mediators that characterize the LASV infection. The gene network shows that glycoprotein sialylation, sialyltransferase enzymatic activities and glycosphingolipid biosynthesis are linked with the ST3GAL4 function. However, the physical interaction of FAM 213A, CD8B molecule and proprotein convertase subtilisin/kexin type 1 inhibitor (PCSK1N) with ST3GAL4 is intriguing in this perspective. There are 11 glycosylated asparagine sequons of the human LAMP1 but only nine were assigned a sialylated glycan cap to mediate the LASV GP-C and LAMP1 interaction having exceeded a recommended glycosylation threshold of 0.5. Therefore, the sialylated glycans of the human LAMP1 are a total of nine and these sialylated glycans mediate the molecular recognition between LASV and LAMP1. This study therefore, predicts that there is a cellular interchange between N-linked glycosylation properties of the human LAMP1 and LASV glycoprotein, and sialylation functions of ST3GAL4 in LASV infectivity. Further studies and the clinical trial of this predictive model on the sialylated glycans of LAMP1 will facilitate the understanding of the LASV micropinocytosis process in host cells.

Personal protective equipment for viral hemorrhagic fevers

PURPOSE OF REVIEW

Viral hemorrhagic fevers (VHF) encompass many organisms that have caused sporadic outbreaks with high case fatality rates. This article reviews VHF with reported human-to-human transmission and describes updates about personal protective equipment (PPE) for healthcare personnel (HCP) and others. We summarize existing information about appropriate PPE use, training, and compliance for care of VHF patients in endemic and nonendemic countries, as well as addresses the challenges HCP experience when using PPE.

RECENT FINDINGS

PPE is essential in protecting HCP from exposure to disease-causing pathogens. Recent evidence shows that anyone involved in care, management, and transport of certain VHF patients must use elements of PPE as part of appropriate infection prevention and control (IPC) practices. Strict adherence to standard precautions has effectively interrupted human-to-human transmission of a number of VHF. However, unclear protocols, inconsistent training, climate challenges, and cultural sensitivities impede proper PPE use. Appropriate PPE use can drastically reduce the risk of HCP exposure to VHF.

SUMMARY

Infections caused by certain VHFs can be highly pathogenic and associated with significant morbidity and mortality. Though it is well documented that use of PPE and good IPC practices are critical to reducing transmission, little conclusive evidence exists about the ideal PPE ensemble or components. Concerns with comfort, compliance, training, and usability may impede proper PPE use. Basic PPE elements, used appropriately as part of stringent IPC, must always form the foundation of care for HCP-treating patients with VHF. More research is required to identify the ideal PPE ensemble for caring for VHF patients in various settings.

Routine and pulse vaccination for Lassa virus could reduce high levels of endemic disease: A mathematical modelling study

Lassa fever is an acute viral illness caused by Lassa virus (LASV), a rodent-borne pathogen. LASV is endemic to much of Sub-Saharan West Africa, where seasonal outbreaks cause significant morbidity and mortality. Increased global awareness of LASV has led to development of improved diagnostic tests, treatments and vaccines. As vaccine candidates are trialled, it is essential to assess the potential outcomes of introducing a LASV vaccination program in endemic regions. This study investigates the potential outcomes of routine and pulse vaccination strategies using a deterministic mathematical model that captures seasonal LASV transmission between rodents and humans. For plausible parameter values, we find that immunization of 40% of infants at 70% vaccine effectiveness achieves a population-level reduction in infectious case numbers of 30%, while coverage of 60% at 90% vaccine effectiveness achieves a 56% reduction. Similar reductions can be achieved more rapidly via population-wide pulse vaccination at 11% coverage (30% reduction at 70% effectiveness) or 23% coverage (56% reduction at 90% effectiveness) repeated every 10 years. Similar pulse vaccine doses delivered at reduced frequency, but increased coverage achieves a greater reduction in infectious cases. Findings around infant vaccination are sensitive to our assumption that immunity is life-long, while pulse-vaccination has only slightly reduced effect if immunity lasts 10-30 years. An effective LASV vaccination program would incorporate pulse vaccination in addition to routine childhood immunization to limit disease. Estimates of feasible vaccine coverage and effectiveness are needed to fully quantify the likely benefits of a vaccination program in LASV endemic regions.