Biology subjects

Acciani, M. D.

Publications and source records attributed to Acciani, M. D..

5 recordsLinked to original sources

bioRxiv2025

Uncovering the features of Measles-targeting human antibodies elicited by the MMR vaccine

Measles virus (MeV), a highly transmissible paramyxovirus, causes disease that can lead to severe complications and death, particularly in babies and young children. Deployment of the durable, highly effective, live-attenuated measles vaccine has saved an estimated 94 million lives in the past 50 years,1 yet the immunological explanation for this vaccines unique success and its landscape of antibody recognition remains unclear. Here we report the first panel of human monoclonal antibodies (mAbs) specific for the MeV hemagglutinin (H) and fusion (F) surface proteins, derived from the memory B cells of an MMR vaccinee. From over 100 cloned human mAbs, we mapped four major epitope clusters on H and another five major clusters on F, and structurally characterized 17 representative mAbs including one or more examples of each of the nine epitope clusters on the two surface antigens. We find that antibodies against both H and F can lead to potent virus neutralization and reduction of viral loads in vivo, including one mAb against F that reduces viral loads to below the limit of detection for all animals. High-resolution cryo-EM reveals contact sites of the most protective antibodies against both surface antigens. Discovery, characterization, and in vitro and in vivo success of these fully human mAbs now provide new avenues for prophylactic or therapeutic intervention against this re-emerging virus. HighlightsO_LIA large panel of Measles-specific monoclonal antibodies was isolated from a human MMR vaccinee, years after vaccination. C_LIO_LIStructural and biochemical mapping paints a landscape of antibody recognition with nine major competition groups, including four major sites on Hemagglutinin (H) and five on the fusion protein (F). C_LIO_LIAntibodies against both H and F confer in vitro neutralization and in vivo protection, including, in one case, undetectable viral load after antibody treatment. C_LIO_LIThe most protective H-specific mAbs, 4D08 and 1C08, target the receptor-binding site and the F-proximal outside of the H dimer, and likely function by interfering with receptor binding and H-F interactions, respectively. C_LIO_LIThe most protective F-specific mAbs, 3A12 and 4F09, target the sides and apex of the prefusion F trimer, and likely function by locking F into its pre-fusion state C_LI

immunology↗

bioRxiv2024

Chikungunya Virus Release is Reduced by TIM-1 Receptors Through Binding of Envelope Phosphatidylserine

T-cell immunoglobin and mucin domain protein-1 (TIM-1) mediates entry of Chikungunya virus (CHIKV) into some mammalian cells through the interaction with envelope phospholipids. While this interaction enhances entry, TIM has been shown to tether newly formed HIV and Ebola virus particles, limiting their efficient release. In this study, we investigate the ability of surface receptors such as TIM-1 to sequester newly budded virions on the surface of infected cells. We established a luminescence reporter system to produce Chikungunya viral particles that integrate nano-luciferase and easily quantify viral particles. We found that TIM-1 on the surface of host cells significantly reduced CHIKV release efficiency in comparison to other entry factors. Removal of cell surface TIM-1 through direct cellular knock-out or altering the cellular lipid distribution enhanced CHIKV release. Over the course of infection, CHIKV was able to counteract the tethering effect by gradually decreasing the surface levels of TIM-1 in a process that appears to be mediated by the nonstructural protein 2. This study highlights the importance of phosphatidylserine receptors in mediating not only the entry of CHIKV but also its release and could aid in developing cell lines capable of enhanced vaccine production. ImportanceChikungunya virus (CHIKV) is an enveloped alphavirus transmitted by the bites of infectious mosquitoes. Infection with CHIKV results in the development of fever, joint pain, and arthralgia that can become chronic and last for months after infection. Prevention of this disease is still highly focused on vector control strategies. In December 2023, a new live attenuated vaccine against CHIKV was approved by the FDA. We aimed to study the cellular factors involved in CHIKV egress, to better understand CHIKVs ability to efficiently infect and spread among a wide variety of cell lines. We found that TIM-1 receptors can significantly abrogate CHIKVs ability to efficiently exit infected cells. This information can be beneficial for maximizing viral particle production in laboratory settings and during vaccine manufacturing.

microbiology↗

bioRxiv2022

Phosphatidylserine within the Viral Membrane Enhances Chikungunya Virus Infectivity in a Cell-type Dependent Manner

Chikungunya virus (CHIKV), an alphavirus of the Togaviridae family, is the causative agent of the human disease chikungunya fever (CHIKF), which is characterized by debilitating acute and chronic arthralgia. No licensed vaccines or antivirals exist for CHIKV. Preventing the attachment of viral particles to host cells is an attractive intervention strategy. Viral entry of enveloped viruses from diverse families including Filoviridae and Flaviviridae is mediated or enhanced by phosphatidylserine receptors (PSRs). PSRs facilitate the attachment of enveloped viruses to cells by binding to exposed phosphatidylserine (PS) in the viral lipid membrane - a process termed viral apoptotic mimicry. To investigate the role of viral apoptotic mimicry during CHIKV infection, we produced viral particles with discrete amounts of exposed PS on the virion envelope by exploiting the cellular distribution of phospholipids at the plasma membrane. We found that CHIKV particles containing high outer leaflet PS (produced in cells lacking flippase activity) were more infectious in Vero cells than particles containing low levels of outer leaflet PS (produced in cells lacking scramblase activity). However, the same viral particles were similarly infectious in NIH3T3 and HAP1 cells, suggesting PS levels can influence infectivity only in cells with high levels of PSRs. Interestingly, PS-dependent CHIKV entry was observed in mosquito Aag2 cells, but not C6/36 cells. These data demonstrate that CHIKV entry via viral apoptotic mimicry is cell-type dependent. Furthermore, viral apoptotic mimicry has a mechanistic basis to influence viral dynamics in vivo in both the human and mosquito host. ImportanceOutbreaks of Chikungunya virus (CHIKV) have occurred throughout Africa, Asia, and Europe. Climate change permits the expansion of Aedes mosquito vectors into more temperate regions, broadening the geographic range and increasing the frequency of future human outbreaks. The molecular basis underlying the broad host and cellular tropism of CHIKV remains unresolved. While several host molecules have been implicated in CHIKV viral attachment and entry, the role of lipid-mediated attachment (viral apoptotic mimicry) is unclear. We observed that higher levels of externalized phosphatidylserine (PS) in the viral lipid bilayer correlated with enhanced CHIKV infectivity in mammalian cells abundant with PS receptors and lacking alternative attachment factors. Interestingly, CHIKV infection in mosquito Aag2 cells was also affected by viral PS accessibility. This study further delineates the role of virus-cell attachment molecules in CHIKV infection. Viral apoptotic mimicry has potential to influence CHIKV dynamics in vivo in both the human and mosquito host.

microbiology↗

bioRxiv2021

Cool temperatures limit Zika virus genome replication

Zika virus is a mosquito-borne flavivirus known to cause severe birth defects and neuroimmunological disorders. We have previously demonstrated that mosquito transmission of Zika virus decreases with temperature. While transmission was optimized at 29{degrees}C, it was limited at cool temperatures (< 22{degrees}C) due to poor virus establishment in the mosquitoes. Temperature is one of the strongest drivers of vector-borne disease transmission due to its profound effect on ectothermic mosquito vectors, viruses, and their interaction. Although there is substantial evidence of temperature effects on arbovirus replication and dissemination inside mosquitoes, little is known about whether temperature affects virus replication directly or indirectly through mosquito physiology. In order to determine the mechanisms behind temperature-induced changes in Zika virus transmission potential, we investigated different steps of the virus replication cycle in mosquito cells (C6/36) at optimal (28{degrees}C) and cool (20{degrees}C) temperatures. We found that cool temperature did not alter Zika virus entry or translation but reduced the amount of double-stranded RNA replication intermediates. If replication complexes were first formed at 28{degrees}C and the cells were subsequently shifted to 20{degrees}C, the late steps in the virus replication cycle were efficiently completed. These data suggest that cool temperature decreases the efficiency of Zika virus genome replication in mosquito cells. This phenotype was observed in the Asian-lineage of Zika virus, while the African-lineage Zika virus was less restrictive at 20{degrees}C. ImportanceWith half of the human population at risk, arboviral diseases represent a substantial global health burden. Zika virus, previously known to cause sporadic infections in humans, emerged in the Americas in 2015 and quickly spread worldwide. There was an urgent need to better understand the disease pathogenesis, develop therapeutics and vaccines, as well as to understand, predict, and control virus transmission. In order to efficiently predict the seasonality and geography for Zika virus transmission, we need a deeper understanding of the host-pathogen interactions and how they can be altered by environmental factors such as temperature. Identifying the step in the virus replication cycle that is inhibited in cool conditions can have implications in modeling the temperature suitability for arbovirus transmission as global environmental patterns change. Understanding the link between pathogen replication and environmental conditions can potentially be exploited to develop new vector control strategies in the future.

microbiology↗

bioRxiv2020

Ebola virus requires phosphatidylserine scrambling activity for efficient budding and optimal infectivity

AbstractEbola virus (EBOV) interacts with cells using two categories of cell surface receptors, C-type lectins and phosphatidylserine (PS) receptors. PS receptors typically bind to apoptotic cell membrane PS and orchestrate the uptake and clearance of apoptotic bodies. Many viruses coated with PS-containing lipid envelopes, acquired during budding from host cells, can also exploit these receptors for internalization. PS is restricted to the inner leaflet of the plasma membrane in homeostatic cells, an orientation that would be unfavorable for PS receptor-mediated uptake if conserved on the viral envelope. Therefore, it is theorized that viral infection induces host cell PS externalization to the outer leaflet during replication. Cells have several membrane scramblase enzymes that enrich outer leaflet PS when activated. Here, we investigate two scramblases, TMEM16F and XKR8, as possible mediators of cellular and viral envelope surface PS levels during recombinant VSV/EBOV-GP replication and EBOV virus-like particle (VLP) production. We found that rVSV/EBOV-GP and EBOV VLPs produced in XKR8 knockout cells contain decreased levels of PS in their outer leaflets. {Delta}XKR8-made rVSV/EBOV-GP is 70% less efficient at infecting cells through apoptotic mimicry compared to viruses made in parental cells. Our data suggest that virion surface PS acquisition requires XKR8 activity, whereas TMEM16F activity is not essential. Unexpectedly, we observed defective rVSV/G, rVSV/EBOV-GP, and EBOV VLP budding in {Delta}XKR8 cells, suggesting that phospholipid scrambling via XKR8 enhances both Ebola infectivity and budding efficiency. Overexpression of XKR8 dramatically increased budding activity, suggesting outer leaflet PS is required for both particle production and increased infectivity. ImportanceThe Democratic Republic of the Congo experienced its deadliest Ebola outbreak from 2018 to 2020, with 3,444 confirmed cases and 2,264 deaths (as of March 12, 2020). Owing to the extensive damage that these outbreaks have caused in Africa, as well as its future epidemic potential, Ebola virus (EBOV) ranks among the top eight priority pathogens outlined by the WHO in 2018. A comprehensive understanding of Ebola entry pathways into target cells is critical for antiviral development and outbreak control. Thus far, host-cell scramblases TMEM16F and XKR8 have each been named as the sole mediator of Ebola envelope surface phosphatidylserine (PS). We assessed the contributions of these proteins using CRISPR knockout cells and two EBOV models: rVSV/EBOV-GP and EBOV VLPs. We observed that XKR8 is required for optimal EBOV envelope PS levels, PS receptor engagement, and particle budding across all viral models, whereas TMEM16F did not play a major role.

microbiology↗