Pathology and Pathogenesis of Lassa Fever: Novel Immunohistochemical Findings in Fatal Cases and Clinico-pathologic Correlation

Background Lassa fever is a zoonotic, acute viral illness first identified in Nigeria in 1969. An estimate shows that the “at risk” seronegative population (in Sierra Leone, Guinea, and Nigeria) may be as high as 59 million, with an annual incidence of all illnesses of three million, and fatalities up to 67,000, demonstrating the serious impact of the disease on the region and global health. Methods Histopathologic evaluation, immunohistochemical assay, and electron microscopic examination were performed on postmortem tissue samples from 12 confirmed Lassa fever cases. Results Lassa fever virus antigens and viral particles were observed in multiple organ systems and cells, including cells in the mononuclear phagocytic system and other specialized cells where it had not been described previously. Conclusions The immunolocalization of Lassa fever virus antigens in fatal cases provides novel insightful information with clinical and pathogenetic implications. The extensive involvement of the mononuclear phagocytic system, including tissue macrophages and endothelial cells suggests participation of inflammatory mediators from this lineage with the resulting vascular dilatation and increasing permeability. Other findings indicate the pathogenesis of LF is multifactorial and additional studies are needed.

Lassa Fever Virus Binds Matriglycan—A Polymer of Alternating Xylose and Glucuronate—On α-Dystroglycan

Lassa fever virus (LASV) can cause life-threatening hemorrhagic fevers for which there are currently no vaccines or targeted treatments. The late Prof. Stefan Kunz, along with others, showed that the high-affinity host receptor for LASV, and other Old World and clade-C New World mammarenaviruses, is matriglycan—a linear repeating disaccharide of alternating xylose and glucuronic acid that is polymerized uniquely on α-dystroglycan by like-acetylglucosaminyltransferase-1 (LARGE1). Although α-dystroglycan is ubiquitously expressed, LASV preferentially infects vascular endothelia and professional phagocytic cells, which suggests that viral entry requires additional cell-specific factors. In this review, we highlight the work of Stefan Kunz detailing the molecular mechanism of LASV binding and discuss the requirements of receptors, such as tyrosine kinases, for internalization through apoptotic mimicry.

Outbreak of Measles in vaccinated population in Southeastern Nigeria

Background: Outbreaks of respiratory disease, febrile illness and rash occurred in two adjoining rural communities of Imo State, Southeastern, Nigeria, at different times between 2006 and 2020. Laboratory investigation was carried out to determine the aetiological agent of the outbreak. Methodology: Oropharyngeal swabs were collected from 6 individuals showing symptoms of disease, within 3-4 days of appearance of rash. Venous blood samples were also collected from a total of 41 symptomatic persons, their contacts and individuals with resolved infections. Swabs were inoculated into Vero, HEp-2c, B95a and MDCK cell lines. Sera were analyzed using enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G and M to rubella and measles viruses, while immunofluorescence assay was used to detect Lassa fever virus immunoglobulins. Descriptive data were analyzed using the Statistical Package for the Social Sciences (SPSS). Results: Four of the 6 (66.7%) swab samples showed viral activity or cytopathic effect characterized by clumping of cells in Vero cells while 2 (33.3%) in Hep-2c characterized by rounding up of cells. Thirty-nine (95.1%) sera were positive for measles IgG while 13 (31.7%) were positive for IgM. Thirty-six (87.8%) sera were positive for rubella IgG but none was positive for IgM. None of the sera was positive for Lassa fever virus IgG and IgM. Conclusion: Measles virus was responsible for the outbreak among previously vaccinated population in the communities, while Rubella and Lassa fever viruses were excluded as the etiological agents of the outbreak. Keywords: Epidemics; IgG and IgM; Cell lines; Vaccination; Measles virus French title: Épidémie de rougeole dans la population vaccinée du sud-est du Nigéria Contexte: Des flambées de maladies respiratoires, de maladies fébriles et d'éruptions cutanées sont survenues dans deux communautés rurales voisines de l'État d'Imo, dans le sud-est du Nigéria, à des moments différents entre 2006 et 2020. Une enquête en laboratoire a été menée pour déterminer l'agent étiologique de l'épidémie. Méthodologie: Des écouvillons oropharyngés ont été prélevés sur 6 individus présentant des symptômes de maladie, dans les 3 à 4 jours suivant l'apparition de l'éruption cutanée. Des échantillons de sang veineux ont également été prélevés sur un total de 41 personnes symptomatiques, leurs contacts et des personnes souffrant d'infections résolues. Des écouvillons ont été inoculés dans des lignées cellulaires Vero, HEp-2c, B95a et MDCK. Les sérums ont été analysés en utilisant un test immuno-enzymatique (ELISA) pour les immunoglobulines G et M contre les virus de la rubéole et de la rougeole, tandis que le test d'immunofluorescence a été utilisé pour détecter les immunoglobulines du virus de la fièvre de Lassa. Les données descriptives ont été analysées à l'aide du progiciel statistique pour les sciences sociales (SPSS). Résultats: Quatre des 6 échantillons sur écouvillon (66,7%) ont montré une activité virale ou un effet cytopathique caractérisé par l'agglutination des cellules dans les cellules Vero, tandis que 2 (33,3%) dans Hep-2c étaient caractérisés par un arrondissement des cellules. Trente-neuf (95,1%) sérums étaient positifs pour les IgG contre la rougeole tandis que 13 (31,7%) étaient positifs pour les IgM. Trente-six (87,8%) sérums étaient positifs pour les IgG contre la rubéole, mais aucun n'était positif pour les IgM. Aucun des sérums n'était positif pour les IgG et IgM du virus de la fièvre de Lassa. Conclusion: Le virus de la rougeole était responsable de l'épidémie parmi la population précédemment vaccinée dans les communautés, tandis que les virus de la rubéole et de la fièvre de Lassa ont été exclus comme agents étiologiques de l'épidémie. Mots clés: épidémies; IgG et IgM; Lignées cellulaires; Vaccination; Virus de la rougeole

Boosting understanding of Lassa Fever virus epidemiology: Field testing a novel assay to identify past Lassa Fever virus infection in blood and oral fluids of survivors and unexposed controls in Sierra Leone

Background Despite identification 50 years ago, the true burden of Lassa Fever (LF) across Africa remains undefined for reasons including research focus on hospitalised patients, lack of validated field-feasible tools which reliably identify past infection, and the fact that all assays require blood samples making large-scale surveys difficult. Designated a priority pathogen of epidemic potential requiring urgent research by the World Health Organisation, a better understanding of LF sero-epidemiology is essential to developing and evaluating new interventions including vaccines. We describe the first field testing of a novel species-neutral Double Antigen Binding Assay (DABA) designed to detect antibodies to LF in plasma and oral fluid. Methodology/Principal findings Paired plasma and oral fluid were collected in Sierra Leone from survivors discharged from Kenema Government Hospital Lassa Fever Unit between 1980 and 2018, and from controls recruited in Freetown in 2019. Epidemiological sensitivity and specificity of the DABA measured against historical diagnosis in survivors and self-declared non-exposed controls was 81.7% (95% CI 70.7%– 89.9%) and 83.3% (72.7%- 91.1%) respectively in plasma, and 71.8% (60.0%– 81.9%) and 83.3% (72.7%– 91.1%) respectively in oral fluid. Antibodies were identified in people infected up to 15 years and, in one case, 40 years previously. Participants found oral fluid collection easy and painless with 80% happy to give an oral fluid sample regularly. Conclusions/Significance Given the difficulties of assay validation in a resource-limited setting, including unexpected exposures and diagnostics of varying accuracy, the new assay performed well in both plasma and oral fluid. Sensitivity and specificity are expected to be higher when case/control ascertainment is more definitive and further work is planned to investigate this. Even at the performance levels achieved, the species-neutral DABA has the potential to facilitate the large-scale seroprevalence surveys needed to underpin essential developments in LF control, as well as support zoonotic investigations.

Case series of outcome of newborn babies exposed to Lassa fever virus infection

Lassa fever (LF) is an acute viral hemorrhagic fever caused by the Lassa virus, a zoonotic infection transmitted by the infected multimammate mouse which is endemic in West African countries. It affects all ages contributing to high maternal and neonatal mortality rates. Neonates are at risk of vertical and horizontal transmission of Lassa virus. We report a series of six newborns, three of whom were delivered to Lassa fever positive mothers and were managed as exposed babies while the remaining three were diagnosed with neonatal Lassa fever. None of the babies exposed to the virus became infected and two of these exposed babies had a positive outcome. All the babies with neonatal Lassa fever died days after birth even before confirming the diagnosis and initiating ribavirin treatment. This highlights the need for prompt diagnosis in utero with treatment of mother before delivery to improve the neonatal outcome. Also, the need to commence intravenous ribavirin treatment in highly suspicious cases of neonatal Lassa fever while awaiting confirmation of the diagnosis is emphasized.

Viruses, Plagues, and History

“Viruses, Plagues, & History” focuses on the effects of viral diseases on human history. Written by an eminent internationally respected virologist, it couples the fabric of history with major concepts developed in virology, immunology, vaccination, and accounts by people who first had, saw and acted at the times these events occurred. Much of the preventive and therapeutic progress (vaccines, antiviral drugs) has been made in the last 60 years. Many of those who played commanding roles in the fight to understand, control and eradicate viruses and viral diseases are (were) personally known to the author and several episodes described in this book reflect their input. The book records the amazing accomplishments that led to the control of lethal and disabling viral diseases caused by Smallpox, Yellow Fever, Measles, Polio, Hepatitis A, B and C, and HIV. These six success stories are contrasted with viral infections currently out of control—COVID-19, Ebola virus, Lassa Fever virus, Hantavirus, West Nile virus, and Zika. Influenza, under reasonable containment at present, but with the potential to revert to a world-wide pandemic similar to 1918–1919 where over 50 million people were killed. The new platforms to develop inhibitory and prophylactic vaccines to limit these and other viral diseases is contrasted to the anti-vaccine movement and the false prophets of autism.

An Overview of Newly Emerging Viral Plagues: The Hemorrhagic Fevers and a Newly Mysterious Suspect of Viral Disease, Acute Flaccid Paralysis

This chapter highlights three of the recently identified viruses: Lassa fever virus, Ebola virus, and hantavirus. All three are equally lethal infectious agents, but they are members of different viral families. They share the ability to cause hemorrhagic fever. Once infected with any of these viruses, the victim soon suffers profuse breaks in small blood vessels, causing blood to ooze from the skin, mouth, gastrointestinal tract, and rectum. Internally, blood flows into the pleural cavity where the lungs are located, into the pericardial cavity surrounding the heart, into the abdomen, and into organs like the liver, kidney, heart, spleen, and lungs. Eventually, this uncontrolled bleeding causes unconsciousness and death. There is currently no established vaccine to prevent these potential plagues, although several are in various stages of development, and an Ebola vaccine is currently undergoing trial in Africa. The chapter also considers a newly emerging and undefined but serious disease of children, which arose primarily in 2014. Based on clinical observations, the disease is identified by the signs and symptoms of acute flaccid myelitis.