Cross-protection from St. Louis encephalitis virus and Usutu virus disease by human West Nile virus convalescent plasma in mice
| dc.contributor.author | Hossain, Md Shakhawat | en |
| dc.contributor.committeechair | Duggal, Nisha K. | en |
| dc.contributor.committeemember | Meng, Xiang-Jin | en |
| dc.contributor.committeemember | Luo, Xin M. | en |
| dc.contributor.committeemember | Weger-Lucarelli, James | en |
| dc.date.accessioned | 2024-10-29T19:02:30Z | en |
| dc.date.available | 2024-10-29T19:02:30Z | en |
| dc.date.issued | 2024-08-21 | en |
| dc.description.abstract | West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), and Usutu virus (USUV) are emerging mosquito-borne flaviviruses. These viruses are phylogenetically closely related and belong to the Japanese encephalitis serocomplex group. Similar to other flaviviruses, these viruses are enveloped, with genomes comprising positive-sense, single-stranded RNA approximately 11 kb in length. Upon translation, a single polyprotein is produced, consisting of three structural and seven non-structural proteins. These proteins function in virus binding to the cell membrane, entry into cells, replication, immune evasion, and the production of new virus progeny. Typically, these viruses are maintained in a sylvatic cycle involving avian hosts, such as passerine birds, and mosquitoes. However, they can accidentally spill over to humans through mosquito bites or wildlife exposure. Although humans generally remain asymptomatic and do not support sufficient viral replication for transmission, they can develop febrile disease and, in some cases, severe neuroinvasive diseases, especially among the elderly or immunocompromised individuals. Due to their co-circulation in the same geographical areas and sharing similar hosts and vectors, individuals in Italy and Germany have been detected as seropositive for WNV and USUV, while seropositivity for WNV and SLEV has been observed in the Americas. Viruses in the Japanese encephalitis virus serocomplex group exhibit significant antigenic similarity. The envelope protein alone contains 12 distinct epitopes and at least three highly conserved epitopes among the JEV serocomplex. Consequently, infection with one member of the JEV serocomplex group, such as WNV, induces WNV-specific antibodies and heterotypic antibodies that can cross-neutralize other members of the JEV serocomplex group, such as USUV and SLEV. Therefore, cross-reactive epitopes can protect against heterologous virus challenges to varying extents, depending on the accessibility of the antibodies to the epitopes. Prior infection with WNV or its envelope domain III (EDIII) or non-structural protein 1 (NS1) protected mice from lethal JEV challenges. Vaccination against WNV protected mice from lethal USUV challenges, and vice versa. Immunity to JEV or SLEV protected hamsters from lethal WNV challenges. Although human sera immune to WNV cross-neutralized USUV and SLEV in vitro during serodiagnosis, the actual mechanism of cross-protection among WNV, USUV, and SLEV remains poorly characterized. Therefore, this study aims to understand the mechanism of cross-protection. Specifically, this research investigated whether human plasma immune to WNV could cross-protect mice from encephalitis caused by SLEV or USUV. Initially, WNV-specific human convalescent plasma and mouse WNV convalescent serum (as a positive control) neutralized WNV and cross-neutralized USUV and SLEV in vitro in a neutralization test. Subsequently, immunocompetent mice were intraperitoneally injected with human WNV convalescent plasma, human normal plasma, mouse WNV convalescent serum, or mouse normal serum the day before being challenged with WNV, SLEV, or USUV via footpad injection. We found that human WNV convalescent plasma provided mice with strong protection against neuroinvasive encephalitis caused by WNV. Additionally, human WNV convalescent plasma reduced the viremia titers of SLEV and USUV for several days during acute infection. Human WNV convalescent serum also demonstrated a trend towards protecting mice from SLEV-induced encephalitis, as evidenced by lower SLEV titers in the brain and histopathology scores. These findings will aid in decoding the mechanisms of cross-protection among the JEV serovars, developing therapeutic strategies against WNV, SLEV, and USUV, and anticipating potential disease outcomes, especially in regions where multiple viruses of the JEV serocomplex are endemic. | en |
| dc.description.abstractgeneral | West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), and Usutu virus (USUV) are emerging flaviviruses transmitted by mosquito bites, primarily among perching birds. However, mosquitoes can also transmit these viruses to animals and humans, especially in regions where these viruses are prevalent. The immune system, which defends against pathogens and other diseases, usually combats these viruses effectively, preventing most people from developing symptoms. The immune system has two main branches: the innate immune system, which confers immediate defense, and the adaptive immune system that includes antibodies and certain long-lasting memory cells, that can fight off infections years after the initial exposure to the same or similar disease-causing agents. Occasionally, the immune system fails to fight these viruses, particularly in the elderly or those with chronic diseases, leading to fever or severe brain inflammation called encephalitis. Currently, WNV and SLEV are circulating in the Americas, while WNV and USUV are present in European countries. Due to similar transmission methods, infection patterns, and geographical overlap, individuals might be sequentially infected with WNV and USUV in Europe, and WNV and SLEV in the Americas in their lifetime. These viruses also share common antigens, which can induce similar immune responses. Therefore, the immune response to one virus might protect against another with similar antigens. It has been reported that the immune response induced by WNV can protect against encephalitis caused by USUV or SLEV. However, it remains unclear whether this cross-protection is mediated by antibodies or a certain type of immune cells called T cells. This study investigates whether antibodies induced by WNV infection can protect against SLEV or USUV in a mouse model. Plasma, the part of blood containing antibodies, is referred to as convalescent plasma when collected after an individual has recovered from an infection or disease. Human WNV convalescent plasma was tested against SLEV and USUV using a plaque reduction neutralization test to determine the antibodies’ ability to prevent viral infection in a laboratory setting. Human WNV convalescent plasma effectively prevented SLEV and USUV from infecting cells. We then developed a mouse model that could be infected with SLEV or USUV and mimic human disease. Groups of mice were systematically transferred with human WNV convalescent plasma, human normal plasma, mouse WNV convalescent serum, or mouse normal serum one day before the infection with WNV, SLEV, or USUV. Disease conditions, such as weight loss, reduced movement, hunchback, fur loss, and occasional paralysis, were monitored until the infected mice were humanely euthanized. After euthanasia, the brains of the mice were collected to measure viral load and examine signs of encephalitis. We observed asymptomatic disease outcomes reflecting natural human infection. Both human and mouse WNV convalescent samples reduced viral load in the blood for a period in both SLEV and USUV-challenged groups. Mice treated with human WNV convalescent plasma showed a trend of lower SLEV in their brains. Additionally, mice treated with mouse WNV convalescent serum had lower SLEV titers in their brains compared to those treated with mouse normal serum. Overall, these findings suggest that human WNV convalescent plasma provides some crossprotection against SLEV- and USUV-induced diseases. Understanding the mechanism of crossprotection is crucial for developing therapeutics against these viruses and predicting disease outcomes in areas where multiple viruses of the Japanese encephalitis virus serocomplex are prevalent. | en |
| dc.description.degree | Master of Science | en |
| dc.format.medium | ETD | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.uri | https://hdl.handle.net/10919/121508 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Cross-protection | en |
| dc.subject | West Nile virus | en |
| dc.subject | Saint Louis encephalitis virus | en |
| dc.subject | Usutu virus | en |
| dc.subject | Convalescent plasma | en |
| dc.title | Cross-protection from St. Louis encephalitis virus and Usutu virus disease by human West Nile virus convalescent plasma in mice | en |
| dc.type | Thesis | en |
| dc.type.dcmitype | Text | en |
| thesis.degree.discipline | Biomedical and Veterinary Sciences | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |