Lassa Virus Research Articles

Lassa Fever: A Mini Review of Clinical Features, Diagnosis and Treatment

Lassa virus (LASV) is an enveloped single stranded RNA virus that results in Lassa fever (LF). The causative organism belongs to the Arenavirus genus. Since it's initial diagnosis in 1969 in Lassa town Nigeria, numerous endemic outbreaks have occurred with spread to other regions in Africa and beyond. LF is transmitted via rodent to human and human-to-human transmissions, with rodents being the reservoir of infection. Risk factors for the disease include residing in an endemic area with poor sanitation and overcrowding, close contact with infected individuals and being a health care worker. About 80% of infected patients do not develop symptoms but the remaining develop a multisystem disease, where up to 15% die in-hospital care with its hallmark symptom being bleeding especially from body orifices. This review will introduce a general overview of Lassa fever and describe the epidemiology, clinical features, diagnosis and treatment of Lassa fever patients. It will also provide a means to raise awareness among healthcare workers. Furthermore, our review focuses on the most up-to-date clinical information for the effective management, prevention and counseling of Lassa fever patients.

Lassa virus Z protein hijacks the autophagy machinery for efficient transportation by interrupting CCT2-mediated cytoskeleton network formation

ABSTRACT The Lassa virus (LASV) is a widely recognized virulent pathogen that frequently results in lethal viral hemorrhagic fever (VHF). Earlier research has indicated that macroautophagy/autophagy plays a role in LASV replication, but, the precise mechanism is unknown. In this present study, we show that LASV matrix protein (LASV-Z) is essential for blocking intracellular autophagic flux. LASV-Z hinders actin and tubulin folding by interacting with CCT2, a component of the chaperonin-containing T-complexes (TRiC). When the cytoskeleton is disrupted, lysosomal enzyme transit is hampered. In addition, cytoskeleton disruption inhibits the merge of autophagosomes with lysosomes, resulting in autophagosome accumulation that promotes the budding of LASV virus-like particles (VLPs). Inhibition of LASV-Z-induced autophagosome accumulation blocks the LASV VLP budding process. Furthermore, it is found that glutamine at position 29 and tyrosine at position 48 on LASV-Z are important in interacting with CCT2. When these two sites are mutated, LASV-mut interacts with CCT2 less efficiently and can no longer inhibit the autophagic flux. These findings demonstrate a novel strategy for LASV-Z to hijack the host autophagy machinery to accomplish effective transportation. Abbreviation: 3-MA: 3-methyladenine; ATG5: autophagy related 5; ATG7: autophagy related 7; Baf-A1: bafilomycin A1; CCT2: chaperonin containing TCP1 subunit 2; co-IP: co-immunoprecipitation; CTSD: cathepsin D; DAPI: 4’,6-diamidino-2’-phenylindole; DMSO: dimethyl sulfoxide; EGFR: epidermal growth factor receptor; GFP: green fluorescent protein; hpi: hours post-infection; hpt: hours post-transfection; LAMP1: lysosomal-associated membrane protein 1; LASV: lassa virus; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; mCherry: red fluorescent protein; PM: plasma membrane; SQSTM1/p62: sequestosome 1; STX6: syntaxin 6; VLP: virus-like particle; TEM: transmission electron microscopy; TRiC: chaperonin-containing T-complex; WB: western blotting; μm: micrometer; μM: micromole.

Deep mutational scanning reveals functional constraints and antibody-escape potential of Lassa virus glycoprotein complex

Lassa virus is estimated to cause thousands of human deaths per year, primarily due to spillovers from its natural host, Mastomys rodents. Efforts to create vaccines and antibody therapeutics must account for the evolutionary variability of the Lassa virus's glycoprotein complex (GPC), which mediates viral entry into cells and is the target of neutralizing antibodies. To map the evolutionary space accessible to GPC, we used pseudovirus deep mutational scanning to measure how nearly all GPC amino-acid mutations affected cell entry and antibody neutralization. Our experiments defined functional constraints throughout GPC. We quantified how GPC mutations affected neutralization with a panel of monoclonal antibodies. All antibodies tested were escaped by mutations that existed among natural Lassa virus lineages. Overall, our work describes a biosafety-level-2 method to elucidate the mutational space accessible to GPC and shows how prospective characterization of antigenic variation could aid the design of therapeutics and vaccines.

Modelling Lassa virus dynamics in West African Mastomys natalensis and the impact of human activities.

Lassa fever is a West African rodent-borne viral haemorrhagic fever that kills thousands of people a year, with 100 000 to 300 000 people a year probably infected by Lassa virus (LASV). The main reservoir of LASV is the Natal multimammate mouse, Mastomys natalensis. There is reported asynchrony between peak infection in the rodent population and peak Lassa fever risk among people, probably owing to differing seasonal contact rates. Here, we developed a susceptible-infected-recovered ([Formula: see text])-based model of LASV dynamics in its rodent host, M. natalensis, with a persistently infected class and seasonal birthing to test the impact of changes to seasonal birthing in the future owing to climate and land use change. Our simulations suggest shifting rodent birthing timing and synchrony will alter the peak of viral prevalence, changing risk to people, with viral dynamics mainly stable in adults and varying in the young, but with more infected individuals. We calculate the time-average basic reproductive number, [Formula: see text], for this infectious disease system with periodic changes to population sizes owing to birthing using a time-average method and with a sensitivity analysis show four key parameters: carrying capacity, adult mortality, the transmission parameter among adults and additional disease-induced mortality impact the maintenance of LASV in M. natalensis most, with carrying capacity and adult mortality potentially changeable owing to human activities and interventions.

Critical appraisal of Monkeypox (Mpox) in Africa using scoping and systematic review methods

Africa remains a battlefield for the emergence and re-emergence of deadly aetiologies including the Lassa fever virus from 1969, Monkey pox (mpox) virus from 1970, and Ebola virus from 1976 till date, among others. With the recent index case of mpox following rapid spread from Africa to different continents, a critical appraisal of the disease to x-ray its dynamics in Africa is warranted. This study integrated a mix of scoping and systematic reviews to converse the epidemiology and biosecurity/environmental issues from one health perspective. Our scoping review used major scientific databases based on their relevance and reliability, while the PROSPERO-registered systematic review followed the PRISMA guidelines. Phylogeny analysis was performed to compare recent outbreaks of mpox with the existing genotypic information. The genetic analysis focused on the H3L gene that codes for envelope proteins involved in viral attachment. Transmission of mpox virus was reported mainly in four routes. Animals implicated include monkeys, squirrels, and pigs. Risk factors include age, gender, occupation, climate, travel, political instability, and vaccination status. Different circulating strains were reported with eight-point mutations found to occur in Africa. Observed clustering within the predominant West African (WA) clade and the recent outbreak strains corroborate the reports of WA clade in other non-African and non-endemic countries. Viral adaptation in the WA clade enhanced person-to-person transmissibility, spreading to over 100 countries. Hence, there is need to address mpox host-associated physiological and biochemical changes, the development of mpox virus-specific diagnostic kits and vaccines, and studies on the disease's socio-ecological, economic and psychological consequences.

Health and economic impacts of Lassa vaccination campaigns in West Africa.

Lassa fever is a zoonotic disease identified by the World Health Organization (WHO) as having pandemic potential. This study estimates the health-economic burden of Lassa fever throughout West Africa and projects impacts of a series of vaccination campaigns. We also model the emergence of "Lassa-X" - a hypothetical pandemic Lassa virus variant - and project impacts of achieving 100 Days Mission vaccination targets. Our model predicted 2.7M (95% uncertainty interval: 2.1M-3.4M) Lassa virus infections annually, resulting over ten years in 2.0M (793.8K-3.9M) disability-adjusted life years (DALYs). The most effective vaccination strategy was a population-wide preventive campaign primarily targeting WHO-classified "endemic" districts. Under conservative vaccine efficacy assumptions, this campaign averted $20.1M ($8.2M-$39.0M) in lost DALY value and $128.2M ($67.2M-$231.9M) in societal costs (International dollars 2021). Reactive vaccination in response to local outbreaks averted just one-tenth the health-economic burden of preventive campaigns. In the event of Lassa-X emerging, spreading throughout West Africa and causing approximately 1.2M DALYs within two years, 100 Days Mission vaccination averted 22% of DALYs given a vaccine 70% effective against disease, and 74% of DALYs given a vaccine 70% effective against both infection and disease. These findings suggest how vaccination could alleviate Lassa fever's burden and assist in pandemic preparedness.

Assignment of the Lassa virus transmembrane domain in the prefusion and postfusion states in detergent micelles.

Lassa virus (LASV) is the most prevalent member of the arenavirus family and the causative agent of Lassa fever, a viral hemorrhagic fever. Although there are annual outbreaks in West Africa, and recently isolated cases worldwide, there are no current therapeutics or vaccines. As such, LASV poses a significant global public health threat. One of the key steps in LASV infection is delivering its genetic material by fusing its viral membrane with the host cell membrane. This process is facilitated by significant conformational changes within glycoprotein 2 (GP2), yielding distinct prefusion and postfusion structural states. However, structural information is missing to understand the changes that occur in the transmembrane domain (TM) during the fusion process. Previously, we showed that the TM undergoes pH-dependent structural changes that result in a helical extension. Here, we provide the 1H, 15N, and 13C assignment of the LASV TM backbone in the prefusion and postfusion states. We also provide the 1H, 15N, and 13C assignment of two mutants, G429P and D432P, which prevent this helical extension. These results will help understand the role the TM plays in membrane fusion and can lead to the design of therapeutics against LASV infection.

Identification of residues in Lassa virus glycoprotein 1 involved in receptor switch

Lassa virus (LASV) is an enveloped, negative-sense RNA virus that causes Lassa hemorrhagic fever. Successful entry of LASV requires the viral glycoprotein 1 (GP1) to undergo a receptor switch from its primary receptor alpha-dystroglycan (α-DG) to its endosomal receptor lysosome-associated membrane protein 1 (LAMP1). A conserved histidine triad in LASV GP1 has been reported to be responsible for receptor switch. To test the hypothesis that other non-conserved residues also contribute to receptor switch, we constructed a series of mutant LASV GP1 proteins and tested them for binding to LAMP1. Four residues, L84, K88, L107, and H170, were identified as critical for receptor switch. Substituting any of the four residues with the corresponding lymphocytic choriomeningitis virus (LCMV) residue (L84 ​N, K88E, L10F, and H170S) reduced the binding affinity of LASV GP1 for LAMP1. Moreover, all mutations caused decreases in glycoprotein precursor (GPC)-mediated membrane fusion at both pH 4.5 and 5.2. The infectivity of pseudotyped viruses bearing either GPCL84N or GPCK88E decreased sharply in multiple cell types, while L107F and H170S had only mild effects on infectivity. Using biolayer light interferometry assay, we found that all four mutants had decreased binding affinity to LAMP1, in the order of binding affinity being L84 ​N ​> ​L107F ​> ​K88E ​> ​H170S. The four amino acid loci identified for the first time in this study have important reference significance for the in-depth investigation of the mechanism of receptor switching and immune escape of LASV occurrence and the development of reserve anti-LASV infection drugs.

Identification of a macrocyclic compound targeting the lassa virus polymerase

There are no approved vaccines or therapeutics for Lassa virus (LASV) infections. To identify compounds with anti-LASV activity, we conducted a cell-based screening campaign at biosafety level 4 and tested almost 60,000 compounds for activity against an infectious reporter LASV. Hits from this screen included several structurally related macrocycles. The most potent, Mac128, had a sub-micromolar EC50 against the reporter virus, inhibited wild-type clade IV LASV, and reduced viral titers by 4 orders of magnitude. Mechanistic studies suggested that Mac128 inhibited viral replication at the level of the polymerase.

Hexestrol, an estrogen receptor agonist, inhibits Lassa virus entry.

Lassa virus (LASV) is the causative agent of human Lassa fever which in severe cases manifests as hemorrhagic fever leading to thousands of deaths annually. However, no approved vaccines or antiviral drugs are currently available. Recently, we screened approximately 2,500 compounds using a recombinant vesicular stomatitis virus (VSV) expressing LASV glycoprotein GP (VSV-LASVGP) and identified a P-glycoprotein inhibitor as a potential LASV entry inhibitor. Here, we show that another identified candidate, hexestrol (HES), an estrogen receptor agonist, is also a LASV entry inhibitor. HES inhibited VSV-LASVGP replication with a 50% inhibitory concentration (IC50) of 0.63 µM. Importantly, HES also inhibited authentic LASV replication with IC50 values of 0.31 µM-0.61 µM. Time-of-addition and cell-based membrane fusion assays suggested that HES inhibits the membrane fusion step during virus entry. Alternative estrogen receptor agonists did not inhibit VSV-LASVGP replication, suggesting that the estrogen receptor itself is unlikely to be involved in the antiviral activity of HES. Generation of a HES-resistant mutant revealed that the phenylalanine at amino acid position 446 (F446) of LASVGP, which is located in the transmembrane region, conferred resistance to HES. Although mutation of F446 enhanced the membrane fusion activity of LASVGP, it exhibited reduced VSV-LASVGP replication, most likely due to the instability of the pre-fusion state of LASVGP. Collectively, our results demonstrated that HES is a promising anti-LASV drug that acts by inhibiting the membrane fusion step of LASV entry. This study also highlights the importance of the LASVGP transmembrane region as a target for anti-LASV drugs.IMPORTANCELassa virus (LASV), the causative agent of Lassa fever, is the most devastating mammarenavirus with respect to its impact on public health in West Africa. However, no approved antiviral drugs or vaccines are currently available. Here, we identified hexestrol (HES), an estrogen receptor agonist, as the potential antiviral candidate drug. We showed that the estrogen receptor itself is not involved in the antiviral activity. HES directly bound to LASVGP and blocked membrane fusion, thereby inhibiting LASV infection. Through the generation of a HES-resistant virus, we found that phenylalanine at position 446 (F446) within the LASVGP transmembrane region plays a crucial role in the antiviral activity of HES. The mutation at F446 caused reduced virus replication, likely due to the instability of the pre-fusion state of LASVGP. These findings highlight the potential of HES as a promising candidate for the development of antiviral compounds targeting LASV.

A validate and standardized pseudotyped microneutralization assay as a safe and powerful tool to measure LASSA neutralising antibodies for vaccine development and comparison

Background Over the past few decades, WHO has made massive efforts to promote the development of a vaccine against Lassa virus (LASV), one of the top ten priority pathogens for research and development under the WHO R&D Blueprint for Emerging Infections. To date, several vaccines are at different stages of development. In this scenario, a validated and standardised assay to measure LSV neutralising antibodies is urgently needed for vaccine development and comparison. Methods The neutralisation assay remains the gold standard for determining antibody efficacy. Here we have proposed a safe and validated pseudotyped neutralisation assay for LASV, taking advantage of the development of the first WHO International Standard and Reference Panel for Anti-Lassa Fever (NIBSC code 21/332). Results and Conclusions The proposed results demonstrate that the pseudotyped luciferase neutralisation assay is a specific serological test for the measurement of LASV neutralising antibodies without cross-reacting with standard sera specific for heterologous viral infections. In addition, the assay is accurate, precise, and linear according to criteria and statistical analyses defined and accepted by international guidelines.

Replicon particle vaccination induces non-neutralizing anti-nucleoprotein antibody-mediated control of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) can cause severe human disease and is considered a WHO priority pathogen due to the lack of efficacious vaccines and antivirals. A CCHF virus replicon particle (VRP) has previously shown protective efficacy in a lethal Ifnar-/- mouse model when administered as a single dose at least 3 days prior to challenge. Here, we determine that non-specific immune responses are not sufficient to confer short-term protection, since Lassa virus VRP vaccination 3 days prior to CCHFV challenge was not protective. We also investigate how CCHF VRP vaccination confers protective efficacy by examining viral kinetics, histopathology, clinical analytes and immunity early after challenge (3 and 6 days post infection) and compare to unvaccinated controls. We characterize how these effects differ based on vaccination period and correspond to previously reported CCHF VRP-mediated protection. Vaccinating Ifnar-/- mice with CCHF VRP 28, 14, 7, or 3 days prior to challenge, all known to confer complete protection, significantly reduced CCHFV viral load, mucosal shedding, and markers of clinical disease, with greater reductions associated with longer vaccination periods. Interestingly, there were no significant differences in innate immune responses, T cell activation, or antibody titers after challenge between groups of mice vaccinated a week or more before challenge, but higher anti-NP antibody avidity and effector function (ADCD) were positively associated with longer vaccination periods. These findings support the importance of antibody-mediated responses in VRP vaccine-mediated protection against CCHFV infection.

Unraveling factors responsible for pathogenic differences in Lassa virus strains.

Lassa virus (LASV) is the etiological agent of Lassa fever (LF), a severe hemorrhagic disease with potential for lethal outcomes. Apart from acute symptoms, LF survivors often endure long-term complications, notably hearing loss, which significantly impacts their quality of life and socioeconomic status in endemic regions of West Africa. Classified as a Risk Group 4 agent, LASV poses a substantial public health threat in affected areas. Our laboratory previously developed a novel lethal guinea pig model of LF utilizing the clinical isolate LASV strain LF2384. However, the specific pathogenic factors underlying LF2384 infection in guinea pigs remained elusive. In this study, we aimed to elucidate the differences in the immunological response induced by LF2384 and LF2350, another LASV isolate from a non-lethal LF case within the same outbreak. Through comprehensive immunological gene profiling, we compared the expression kinetics of key genes in guinea pigs infected with LASV LF2384 and LF2350. Our analysis revealed differential expression patterns for several immunological genes, including CD94, CD19-2, CD23, IL-7, and CIITA, during LF2384 and LF2350 infection. Moreover, through the generation of recombinant LASVs, we sought to identify the specific viral genes responsible for the observed pathogenic differences between LF2384 and LF2350. Our investigations pinpointed the L protein as a crucial determinant of pathogenicity in guinea pigs infected with LASV LF2384.

An mRNA-LNP-based Lassa virus vaccine induces protective immunity in mice.

The mammarenavirus Lassa virus (LASV) causes the life-threatening hemorrhagic fever disease, Lassa fever. The lack of licensed medical countermeasures against LASV underscores the urgent need for the development of novel LASV vaccines, which has been hampered by the requirement for a biosafety level 4 facility to handle live LASV. Here, we investigated the efficacy of mRNA-lipid nanoparticle (mRNA-LNP)-based vaccines expressing the LASV glycoprotein precursor (LASgpc) or nucleoprotein (LCMnp) of the prototypic mammarenavirus, lymphocytic choriomeningitis virus (LCMV), in mice. Two doses of LASgpc- or LCMnp-mRNA-LNP administered intravenously (i.v.) protected C57BL/6 mice from a lethal challenge with a recombinant (r) LCMV expressing a modified LASgpc (rLCMV/LASgpc2m) inoculated intracranially. Intramuscular (i.m.) immunization with two doses of LASgpc- or LCMnp-mRNA-LNP significantly reduced the viral load in C57BL/6 mice inoculated i.v. with rLCMV/LASgpc2m. High levels of viremia and lethality were observed in CBA mice inoculated i.v. with rLCMV/LASgpc2m, which were abrogated by i.m. immunization with two doses of LASgpc-mRNA-LNP. The protective efficacy of two i.m. doses of LCMnp-mRNA-LNP was confirmed in a lethal hemorrhagic disease model of FVB mice i.v. inoculated with wild-type rLCMV. In all conditions tested, negligible and high levels of LASgpc- and LCMnp-specific antibodies were detected in mRNA-LNP-immunized mice, respectively, but robust LASgpc- and LCMnp-specific CD8+ T cell responses were induced. Accordingly, plasma from LASgpc-mRNA-LNP-immunized mice did not exhibit neutralizing activity. Our findings and surrogate mouse models of LASV infection, which can be studied at a reduced biocontainment level, provide a critical foundation for the rapid development of mRNA-LNP-based LASV vaccines.IMPORTANCELassa virus (LASV) is a highly pathogenic mammarenavirus responsible for several hundred thousand infections annually in West African countries, causing a high number of lethal Lassa fever (LF) cases. Despite its significant impact on human health, clinically approved, safe, and effective medical countermeasures against LF are not available. The requirement of a biosafety level 4 facility to handle live LASV has been one of the main obstacles to the research and development of LASV countermeasures. Here, we report that two doses of mRNA-lipid nanoparticle-based vaccines expressing the LASV glycoprotein precursor (LASgpc) or nucleoprotein (LCMnp) of lymphocytic choriomeningitis virus (LCMV), a mammarenavirus genetically closely related to LASV, conferred protection to recombinant LCMV-based surrogate mouse models of lethal LASV infection. Notably, robust LASgpc- and LCMnp-specific CD8+ T cell responses were detected in mRNA-LNP-immunized mice, whereas no virus-neutralizing activity was observed.

Intrasegmental recombination as an evolutionary force of Lassa fever virus.

Lassa fever (LF), caused by Lassa virus (LASV), is one of the most dangerous diseases to public health. Homologous recombination (HR) is a basic genetic power driving biological evolution. However, as a negative-stranded RNA virus, it is unknown whether HR occurs between LASVs and its influence on the outbreak of LF. In this study, after analyzing 575 S and 433 L segments of LASV collected in Africa, we found that LASV can achieve HR in both of its segments. Interestingly, although the length of S segment is less than half of the L segment, the proportion of LASVs with S recombinants is significantly higher than that with L recombinants. These results suggest that HR may be a feature of LASV, which can be set by natural selection to produce beneficial or eliminate harmful mutations for the virus, so it plays a role in LASV evolution during the outbreak of LF.

A novel BSL-2 Lassa virus reverse genetics system modelling the complete viral life cycle

ABSTRACT Lassa virus (LASV), a risk-group 4 pathogen, must be handled in biosafety level-4 (BSL-4) conditions, thereby limiting its research and antiviral development. Here, we developed a novel LASV reverse genetics system which, to our knowledge, is the first to study the complete LASV life cycle under BSL-2 conditions. Viral particles can be produced efficiently when LASV minigenomic RNA harbouring minimal viral cis-elements and reporter genes is transfected into a helper cell line stably expressing viral NP, GP, Z and L proteins. The resulting defective virions, named LASVmg, can propagate only in the helper cell line, providing a BSL-2 model to study the complete LASV life cycle. Using this model, we found that a previously reported cellular receptor α-dystroglycan is dispensable for LASVmg infection. Furthermore, we showed that ribavirin can inhibit LASVmg infection by inducing viral mutations. This new BSL-2 system should facilitate studying the LASV life cycle and screening antivirals.

Lessons From the Global SARS-CoV-2 Health Emergency for Potential Future Pandemics

Abstract The emergence of novel infectious agents with pandemic potential remains a critical global concern, as underscored by the COVID-19 pandemic. This study investigates the various factors contributing to the risk of new pandemics and proposes a framework for pandemic prevention and mitigation. We review the characteristics of several infectious agents, including influenza viruses, coronaviruses, filoviruses, paramyxoviruses, Lassa fever virus, Crimean-Congo hemorrhagic fever virus, and the yellow fever virus. These agents are discussed in terms of their transmission modes, reservoirs, potential for human-to-human spread, and historical outbreaks. We emphasize the importance of monitoring and early detection of these agents, especially those with localized outbreaks and zoonotic potential. Our analysis highlights the role of human activities in pandemic risk. Factors such as overuse of antibiotics, environmental changes (deforestation, wildlife habitat encroachment), climate change effects on disease vectors, and increasing global connectivity are examined as drivers of disease emergence. Furthermore, we propose a foursome of critical actions for pandemic prevention and response: early detection and rapid containment; restricting the transmission by social distancing, masking, quarantine, and elimination of vector, which are crucial even before the vaccine is available; global vaccine and treatment distribution; and robust health policy implementation. We emphasize the importance of international collaboration, information sharing, and preparedness to effectively combat pandemics. In conclusion, this commentary provides a comprehensive overview of infectious agents with pandemic potential and their associated risks. It calls for proactive measures to prevent and mitigate future pandemics, emphasizing the need for a global strategy that combines early detection, rapid response, and sustained public health infrastructure.

Cellular immune responses in the guinea pig model with a 9-color phenotypic flow cytometry panel

Abstract Guinea pigs serve as a valuable animal model for many aspects of infectious disease research. A primary limitation of the guinea pig model is the lack of a robust toolbox to probe the underlying immune responses in these animals. We developed an optimized 9-color flow cytometric assay for immunophenotyping peripheral and tissue-associated immune cells in the guinea pig. Using this assay, we can delineate CD45+ cells as well as monocyte and macrophage populations, in addition to further differentiating lymphocyte populations of B and T cells. Importantly, we found that this panel is able to detect these populations in both inbred Strain 13 and outbred Hartley guinea pigs in whole blood and from fresh and frozen cells isolated from several peripheral tissues. We utilized this panel to separately interrogate the immune responses in whole blood and spleen tissue samples after exposure of Hartley guinea pigs with Ebola virus (EBOV) and Strain 13 or Hartley guinea pigs with Lassa virus (LASV). We believe this flow cytometry panel will serve as an important tool to interrogate the underlying immune responses to risk group 4 pathogens in addition to numerous other infectious diseases with the guinea pig model.

Exploring Pre-Pandemic SARS-CoV-2-Specific B Cell Responses in the West African Population.

Abstract The emergence of the novel coronavirus, SARS-CoV-2, during the COVID-19 pandemic prompted investigations into pre-existing immunity in human populations. Despite being a new coronavirus, individuals had previous exposure to common seasonal human coronaviruses. In this study, we examined SARS-CoV-2-specific memory B cells in six pre-pandemic Lassa virus-infected patients from West Africa. By incorporating a SARS-CoV-2 Spike Antigen (WA-1 strain) into a broader antigen panel that included Lassa virus GPC and a control, we identified and sorted antigen-positive B cells. Further analysis revealed a distinct population of SARS-CoV-2-specific memory B cells. Native paired monoclonal antibody (mAb) sequences were recovered from 598 SARS-CoV-2 Spike-positive B cells, demonstrating a surprisingly high frequency of pre-existing SARS-CoV-2-specific B cells. Remarkably, Spike-specific mAbs were recovered from all six donors, each contributing to at least one expanded clonal lineage. Notably, most IgM antibodies belonged to the same lineages. These findings suggest a notable prevalence of pre-existing immunity to SARS-CoV-2 in pre-pandemic patients, potentially influencing susceptibility to the virus and contributing to adverse COVID-19 outcomes. This study provides insights for risk management and supports the development of universal coronavirus vaccines by highlighting the complex interplay between pre-existing immunity and susceptibility to SARS-CoV-2.

Reservoir displacement by an invasive rodent reduces Lassa virus zoonotic spillover risk

The black rat (Rattus rattus) is a globally invasive species that has been widely introduced across Africa. Within its invasive range in West Africa, R. rattus may compete with the native rodent Mastomys natalensis, the primary reservoir host of Lassa virus, a zoonotic pathogen that kills thousands annually. Here, we use rodent trapping data from Sierra Leone and Guinea to show that R. rattus presence reduces M. natalensis density within the human dwellings where Lassa virus exposure is most likely to occur. Further, we integrate infection data from M. natalensis to demonstrate that Lassa virus zoonotic spillover risk is lower at sites with R. rattus. While non-native species can have numerous negative effects on ecosystems, our results suggest that R. rattus invasion has the indirect benefit of decreasing zoonotic spillover of an endemic pathogen, with important implications for invasive species control across West Africa.