High clinical suspicion of donor-derived disease leads to timely recognition and early intervention to treat solid organ transplant-transmitted lymphocytic choriomeningitis virus

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.

Solid organ transplant-related central nervous system infections

PURPOSE OF REVIEW

Central nervous system (CNS) infections in solid organ transplant (SOT) recipients may present atypical or nonspecific symptoms. Due to a wider range of infectious agents compared with immunocompetent hosts, diagnosis is challenging. This review categorizes CNS infections in SOT recipients by cause.

RECENT FINDINGS

New studies have reported new data on the epidemiology and the risk factors associated with each specific pathogen described in this review. Additionally, we included the treatment recommendations.

SUMMARY

The latest findings give us an insight into the different pathogens causing infectious neurologic complications in SOT recipients.

External quality assessment of orthohantavirus and lymphocytic choriomeningitis virus molecular detection and serology in Europe, 2021

BackgroundRodent-borne viruses such as orthohantaviruses and arenaviruses cause considerable disease burden with regional and temporal differences in incidence and clinical awareness. Therefore, it is important to regularly evaluate laboratory diagnostic capabilities, e.g. by external quality assessments (EQA).AimWe wished to evaluate the performance and diagnostic capability of European expert laboratories to detect orthohantaviruses and lymphocytic choriomeningitis virus (LCMV) and human antibody response towards orthohantaviruses.MethodsWe conducted an EQA in 2021; molecular panels consisted of 12 samples, including different orthohantaviruses (Seoul, Dobrava-Belgrade (DOBV), Puumala (PUUV) and Hantaan orthohantavirus), LCMV and negative controls. Serological panels consisted of six human serum samples reactive to PUUV, DOBV or negative to orthohantaviruses. The EQA was sent to 25 laboratories in 20 countries.ResultsThe accuracy of molecular detection of orthohantaviruses varied (50‒67%, average 62%) among 16 participating laboratories, while LCMV samples were successfully detected in all 11 participating laboratories (91-100%, average 96%). The accuracy of serological diagnosis of acute and past orthohantavirus infections was on average 95% among 20 participating laboratories and 82% in 19 laboratories, respectively. A variety of methods was used, with predominance of in-house assays for molecular tests, and commercial assays for serological ones.ConclusionSerology, the most common tool to diagnose acute orthohantavirus infections, had a high accuracy in this EQA. The molecular detection of orthohantaviruses needs improvement while LCMV detection (performed in fewer laboratories) had 95% accuracy. Further EQAs are recommended to be performed periodically to monitor improvements and challenges in the diagnostics of rodent-borne diseases.

Structural basis for antibody-mediated neutralization of lymphocytic choriomeningitis virus

The mammarenavirus lymphocytic choriomeningitis virus (LCMV) is a globally distributed zoonotic pathogen that can be lethal in immunocompromised patients and can cause severe birth defects if acquired during pregnancy. The structure of the trimeric surface glycoprotein, essential for entry, vaccine design, and antibody neutralization, remains unknown. Here, we present the cryoelectron microscopy (cryo-EM) structure of the LCMV surface glycoprotein (GP) in its trimeric pre-fusion assembly both alone and in complex with a rationally engineered monoclonal neutralizing antibody termed 18.5C-M28 (M28). Additionally, we show that passive administration of M28, either as a prophylactic or therapeutic, protects mice from LCMV clone 13 (LCMVcl13) challenge. Our study illuminates not only the overall structural organization of LCMV GP and the mechanism for its inhibition by M28 but also presents a promising therapeutic candidate to prevent severe or fatal disease in individuals who are at risk of infection by a virus that poses a threat worldwide.

Chaperonin TRiC/CCT Participates in Mammarenavirus Multiplication in Human Cells via Interaction with the Viral Nucleoprotein

The eukaryotic chaperonin containing tailless complex polypeptide 1 ring complex (CCT, also known as TCP-1 Ring Complex, TRiC/CCT) participates in the folding of 5% to 10% of the cellular proteome and has been involved in the life cycle of several viruses, including dengue, Zika, and influenza viruses, but the mechanisms by which the TRiC/CCT complex contributes to virus multiplication remain poorly understood. Here, we document that the nucleoprotein (NP) of the mammarenavirus lymphocytic choriomeningitis virus (LCMV) is a substrate of the human TRiC/CCT complex, and that pharmacological inhibition of TRiC/CCT complex function, or RNAi-mediated knockdown of TRiC/CCT complex subunits, inhibited LCMV multiplication in human cells. We obtained evidence that the TRiC/CCT complex is required for the production of NP-containing virus-like particles (VLPs), and the activity of the virus ribonucleoprotein (vRNP) responsible for directing replication and transcription of the viral genome. Pharmacological inhibition of the TRIC/CCT complex also restricted multiplication of the live-attenuated vaccine candidates Candid#1 and ML29 of the hemorrhagic fever causing Junin (JUNV) and Lassa (LASV) mammarenaviruses, respectively. Our findings indicate that the TRiC/CCT complex is required for mammarenavirus multiplication and is an attractive candidate for the development of host directed antivirals against human-pathogenic mammarenaviruses. IMPORTANCE Host-directed antivirals have gained great interest as an antiviral strategy to counteract the rapid emergence of drug-resistant viruses. The chaperonin TRiC/CCT complex has been involved in the life cycle of several viruses, including dengue, Zika, and influenza viruses. Here, we have provided evidence that the chaperonin TRiC/CCT complex participates in mammarenavirus infection via its interaction with the viral NP. Importantly, pharmacological inhibition of TRiC/CCT function significantly inhibited multiplication of LCMV and the distantly related mammarenavirus JUNV in human cells. Our findings support that the TRiC/CCT complex is required for multiplication of mammarenaviruses and that the TRiC/CCT complex is an attractive host target for the development of antivirals against human-pathogenic mammarenaviruses.

Molecular Engineering of a Mammarenavirus with Unbreachable Attenuation

Several mammarenaviruses cause severe hemorrhagic fever (HF) disease in humans and pose important public health problems in their regions of endemicity. There are no United States (US) Food and Drug Administration (FDA)-approved mammarenavirus vaccines, and current anti-mammarenavirus therapy is limited to an off-label use of ribavirin that has limited efficacy. Mammarenaviruses are enveloped viruses with a bi-segmented negative-strand RNA genome. Each genome segment contains two open reading frames (ORF) separated by a noncoding intergenic region (IGR). The large (L) segment encodes the RNA dependent RNA polymerase, L protein, and the Z matrix protein, whereas the small (S) segment encodes the surface glycoprotein precursor (GPC) and nucleoprotein (NP). In the present study, we document the generation of a recombinant form of the prototypic mammarenavirus lymphocytic choriomeningitis virus (LCMV) expressing a codon deoptimized (CD) GPC and containing the IGR of the S segment in both the S and L segments (rLCMV/IGR-CD). We show that rLCMV/IGR-CD is fully attenuated in C57BL/6 (B6) mice but able to provide complete protection upon a single administration against a lethal challenge with LCMV. Importantly, rLCMV/IGR-CD exhibited an unbreachable attenuation for its safe implementation as a live-attenuated vaccine (LAV). IMPORTANCE Several mammarenaviruses cause severe disease in humans and pose important public health problems in their regions of endemicity. Currently, no FDA-licensed mammarenavirus vaccines are available, and anti-mammarenaviral therapy is limited to an off-label use of ribavirin whose efficacy is controversial. Here, we describe the generation of recombinant version of the prototypic mammarenavirus lymphocytic choriomeningitis virus (rLCMV) combining the features of a codon deoptimized (CD) GPC and the noncoding intergenic region (IGR) of the S segment in both S and L genome segments, called rLCMV/IGR-CD. We present evidence that rLCMV/IGR-CD has excellent safety and protective efficacy features as live-attenuated vaccine (LAV). Importantly, rLCMV/IGR-CD prevents, in coinfected mice, the generation of LCMV reassortants with increased virulence. Our findings document a well-defined molecular strategy for the generation of mammarenavirus LAV candidates able to trigger long-term protective immunity, upon a single immunization, while exhibiting unique enhanced safety features, including unbreachable attenuation.

Central nervous system infections after solid organ transplantation

PURPOSE OF REVIEW

Significant advances to our understanding of several neuroinfectious complications after a solid organ transplant (SOT) have occurred in the last few years. Here, we review the central nervous system (CNS) infections that are relevant to SOT via a syndromic approach with a particular emphasis on recent updates in the field.

RECENT FINDINGS

A few key studies have advanced our understanding of the epidemiology and clinical characteristics of several CNS infections in SOT recipients. Risk factors for poor prognosis and protective effects of standard posttransplant prophylactic strategies have been better elucidated. Newer diagnostic modalities which have broad clinical applications like metagenomic next-generation sequencing, as well as those that help us better understand esoteric concepts of disease pathogenesis have been studied. Finally, several studies have provided newer insights into the treatment of these diseases.

SUMMARY

Recent findings reflect the steady progress in our understanding of CNS infections post SOT. They provide several avenues for improvement in the prevention, early recognition, and therapeutic outcomes of these diseases.

Lymphocytic Choriomeningitis-Emerging Trends of a Neglected Virus: A Narrative Review

Lymphocytic choriomeningitis virus (LCMV) is a neglected rodent-borne zoonotic virus distributed worldwide. Since serologic assays are limited to several laboratories, the disease has been underreported, often making it difficult to determine incidence and seroprevalence rates. Although human clinical cases are rarely recorded, LCMV remains an important cause of meningitis in humans. In addition, a fatal donor-derived LCMV infection in several clusters of solid organ transplant recipients further highlighted a pathogenic potential and clinical significance of this virus. In the transplant populations, abnormalities of the central nervous system were also found, but were overshadowed by the systemic illness resembling the Lassa hemorrhagic fever. LCMV is also an emerging fetal teratogen. Hydrocephalus, periventricular calcifications and chorioretinitis are the predominant characteristics of congenital LCMV infection, occurring in 87.5% of cases. Mortality in congenitally infected children is about 35%, while 70% of them show long-term neurologic sequelae. Clinicians should be aware of the risks posed by LCMV and should consider the virus in the differential diagnosis of aseptic meningitis, especially in patients who reported contact with rodents. Furthermore, LCMV should be considered in infants and children with unexplained hydrocephalus, intracerebral calcifications and chorioretinitis. Despite intensive interdisciplinary research efforts, efficient antiviral therapy for LCMV infection is still not available.

Prevalence and Risk Factors for Lymphocytic Choriomeningitis Virus Infection in Continental Croatian Regions

Lymphocytic choriomeningitis virus (LCMV) is a neglected human pathogen associated with aseptic meningitis, severe systemic infections in immunocompromised persons, and congenital anomalies. Data on the prevalence of LCMV infections are scarce. We analyzed the seroprevalence of LCMV in continental Croatian regions. A total of 338 serum samples of professionally exposed (forestry workers, hunters, agriculture workers in contact with rodents) and non-exposed populations (general population, pregnant women) were tested for the presence of LCMV antibodies using indirect immunofluorescence assay. No participants reported recent febrile disease. LCMV IgG antibodies were detected in 23/6.8% of participants: 9.8% exposed persons and 5.1% non-exposed persons (6.1% in the general population and 3.9% in pregnant women). No participants were LCMV IgM positive. Although higher seropositivity was found in males compared to females (8.9% vs. 4.7%), inhabitants of suburban/rural areas compared to inhabitants of urban areas (9.2% vs. 4.6%), and persons who used well as a source of water compared to those who used tap (11.4% vs. 5.6%), these differences did not reach statistical significance. Results of logistic regression showed that the presence of rodents in the house/yard and cleaning rodent nests were associated with an elevated risk for LCMV infection (OR = 2.962, 95% CI = 1.019-8.607).

Transmission of Eastern Equine Encephalitis Virus From an Organ Donor to 3 Transplant Recipients

BACKGROUND

In fall 2017, 3 solid organ transplant (SOT) recipients from a common donor developed encephalitis within 1 week of transplantation, prompting suspicion of transplant-transmitted infection. Eastern equine encephalitis virus (EEEV) infection was identified during testing of endomyocardial tissue from the heart recipient.

METHODS

We reviewed medical records of the organ donor and transplant recipients and tested serum, whole blood, cerebrospinal fluid, and tissue from the donor and recipients for evidence of EEEV infection by multiple assays. We investigated blood transfusion as a possible source of organ donor infection by testing remaining components and serum specimens from blood donors. We reviewed data from the pretransplant organ donor evaluation and local EEEV surveillance.

RESULTS

We found laboratory evidence of recent EEEV infection in all organ recipients and the common donor. Serum collected from the organ donor upon hospital admission tested negative, but subsequent samples obtained prior to organ recovery were positive for EEEV RNA. There was no evidence of EEEV infection among donors of the 8 blood products transfused into the organ donor or in products derived from these donations. Veterinary and mosquito surveillance showed recent EEEV activity in counties nearby the organ donor's county of residence. Neuroinvasive EEEV infection directly contributed to the death of 1 organ recipient and likely contributed to death in another.

CONCLUSIONS

Our investigation demonstrated EEEV transmission through SOT. Mosquito-borne transmission of EEEV to the organ donor was the likely source of infection. Clinicians should be aware of EEEV as a cause of transplant-associated encephalitis.

Screening of donors and recipients for infections prior to solid organ transplantation

PURPOSE OF REVIEW

This review is a brief overview of current guidelines on screening donors and candidates for bacterial, fungal, parasitic and viral infections prior to solid organ transplantation. The pretransplant period is an important time to evaluate infection exposure risk based on social history as well as to offer vaccinations.

RECENT FINDINGS

One of the major changes in the past few years has been increased utilization of increased Public Health Service risk, HIV positive, and hepatitis C-positive donors. There has also been increased attention to donor and recipient risks for geographically associated infections, such as endemic fungal infections and flaviviruses.

SUMMARY

Screening for donors and candidates prior to organ transplantation can identify and address infection risks. Diagnosing infections in a timely manner can help guide treatment and additional testing. Use of necessary prophylactic treatment in organ recipients can prevent reactivation of latent infections and improve posttransplant outcomes.

Donor-derived Viral Infections in Liver Transplantation

Donor-derived infections are defined as any infection present in the donor that is transmitted to 1 or more recipients. Donor-derived infections can be categorized into 2 groups: "expected" and "unexpected" infections. Expected transmissions occur when the donor is known to have an infection, such as positive serology for cytomegalovirus, Epstein Barr virus, or hepatitis B core antibody, at the time of donation. Unexpected transmissions occur when a donor has no known infection before donation, but 1 or more transplant recipients develop an infection derived from the common donor. Unexpected infections are estimated to occur in far less than 1% of solid organ transplant recipients. We will review the epidemiology, risk factors, and approaches to prevention and management of donor-derived viral infectious disease transmission in liver transplantation.

Is This Organ Donor Safe?: Donor-Derived Infections in Solid Organ Transplantation

Infection is an inevitable complication of solid organ transplantation. Unrecognized infection may be transmitted from a donor and result in disseminated disease in the immunosuppressed host. Recent outbreaks of deceased donor-derived infections resulting in high rates of mortality and severe morbidity have emphasized the need to be cautious in using donors with possible meningoencephalitis. Screening of organ donors for potential transmissible infections is paramount to improving transplantation outcomes.

Is This Organ Donor Safe?: Donor-Derived Infections in Solid Organ Transplantation

Infection is an inevitable complication of solid organ transplantation. Unrecognized infection may be transmitted from a donor and result in disseminated disease in the immunosuppressed host. Recent outbreaks of deceased donor-derived infections resulting in high rates of mortality and severe morbidity have emphasized the need to be cautious in using donors with possible meningoencephalitis. Screening of organ donors for potential transmissible infections is paramount to improving transplantation outcomes.

Lymphocytic choriomeningitis virus meningoencephalitis in a renal transplant recipient following exposure to mice

Solid organ transplant recipients (SOTR) are at increased risk for a wide variety of typical and atypical infections as a consequence of impaired cell mediated and humoral immunity. We report a case of meningoencephalitis in a renal transplant recipient caused by lymphocytic choriomeningitis virus (LCMV) acquired by exposure to mice excreta. The clinical course was complicated by the development of hydrocephalus, requiring a ventriculoperitoneal shunt. To our knowledge, this is the first reported case of LCMV infection in a SOTR that was not organ donor derived.

Effective Treatment of Experimental Lymphocytic Choriomeningitis Virus Infection: Consideration of Favipiravir for Use With Infected Organ Transplant Recipients

Lymphocytic choriomeningitis virus (LCMV) poses a substantial risk to immunocompromised individuals. The case fatality rate in recent clusters of LCMV infection in immunosuppressed organ transplantation recipients has exceeded 70%. In the present study, we demonstrate potent antiviral activity of favipiravir against acute, disseminated LCMV infection in NZB mice. Treatment resulted in complete protection against mortality and dramatic reductions in viral loads. In contrast, ribavirin, the current antiviral of choice, was mostly ineffective. Our findings, and the high lethality associated with LCMV infection in transplant recipients, support the consideration of favipiravir as a first-line therapeutic option.