A Longitudinal Analysis of Memory Immune Responses in Convalescent Crimean-Congo Hemorrhagic Fever Survivors in Uganda.

Evaluating the adaptive immune responses to natural infection with Crimean-Congo hemorrhagic fever (CCHF) virus (CCHFV) in human survivors is critical to the development of medical countermeasures. However, the correlates of protection are unknown. As the most prevalent tick-borne human hemorrhagic fever virus with case fatality rates of 5%-30% and worldwide distribution, there is an urgent need to fill these knowledge gaps.

Reversion of Ebolavirus Disease from a Single Intramuscular Injection of a Pan-Ebolavirus Immunotherapeutic.

Intravenous (IV) administration of antiviral monoclonal antibodies (mAbs) can be challenging, particularly during an ongoing epidemic, due to the considerable resources required for performing infusions. An ebolavirus therapeutic administered via intramuscular (IM) injection would reduce the burdens associated with IV infusion and allow rapid treatment of exposed individuals during an outbreak. Here, we demonstrate how MBP134, a cocktail of two pan-ebolavirus mAbs, reverses the course of disease (Gulu variant) with a single IV or IM dose in non-human primates (NHPs) as late as five days post-exposure.

Genotype-specific features reduce the susceptibility of South American yellow fever virus strains to vaccine-induced antibodies.

The resurgence of yellow fever in South America has prompted vaccination against the etiologic agent, yellow fever virus (YFV). Current vaccines are based on a live-attenuated YF-17D virus derived from a virulent African isolate. The capacity of these vaccines to induce neutralizing antibodies against the vaccine strain is used as a surrogate for protection.

Cross-Strain Neutralizing and Protective Monoclonal Antibodies against EEEV or WEEV.

The three encephalitic alphaviruses, namely, the Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV), are classified by the Centers for Disease Control and Prevention (CDC) as biothreat agents. Currently, no licensed medical countermeasures (MCMs) against these viruses are available for humans. Neutralizing antibodies (NAbs) are fast-acting and highly effective MCMs for use in both pre- and post-exposure settings against biothreat agents.

Protective neutralizing antibodies from human survivors of Crimean-Congo hemorrhagic fever.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a World Health Organization priority pathogen. CCHFV infections cause a highly lethal hemorrhagic fever for which specific treatments and vaccines are urgently needed. Here, we characterize the human immune response to natural CCHFV infection to identify potent neutralizing monoclonal antibodies (nAbs) targeting the viral glycoprotein.

Therapy for Argentine hemorrhagic fever in nonhuman primates with a humanized monoclonal antibody.

The COVID-19 pandemic has reemphasized the need to identify safe and scalable therapeutics to slow or reverse symptoms of disease caused by newly emerging and reemerging viral pathogens. Recent clinical successes of monoclonal antibodies (mAbs) in therapy for viral infections demonstrate that mAbs offer a solution for these emerging biothreats. We have explored this with respect to Junin virus (JUNV), an arenavirus classified as a category A high-priority agent and the causative agent of Argentine hemorrhagic fever (AHF).

Capsids and Portals Influence Each Other's Conformation During Assembly and Maturation.

The portal proteins of tailed bacteriophage and Herpesvirus capsids form dodecameric rings that occupy one capsid vertex and are incorporated during the assembly of capsid precursors called procapsids or proheads. Portals are essential and serve as the pore for DNA transit and the site of tail attachment; however, bacteriophage HK97 capsid proteins assemble efficiently without a portal when expressed from plasmids. Following portal co-expression, portals were incorporated into about half of the proheads that were made.

Structure and Characterization of Crimean-Congo Hemorrhagic Fever Virus GP38.

Crimean-Congo hemorrhagic fever virus (CCHFV) is the causative agent of the most widespread tick-borne viral infection in humans. CCHFV encodes a secreted glycoprotein (GP38) of unknown function that is the target of a protective antibody. Here, we present the crystal structure of GP38 at a resolution of 2.

Therapeutic monoclonal antibody treatment protects nonhuman primates from severe Venezuelan equine encephalitis virus disease after aerosol exposure.

There are no FDA licensed vaccines or therapeutics for Venezuelan equine encephalitis virus (VEEV) which causes a debilitating acute febrile illness in humans that can progress to encephalitis. Previous studies demonstrated that murine and macaque monoclonal antibodies (mAbs) provide prophylactic and therapeutic efficacy against VEEV peripheral and aerosol challenge in mice. Additionally, humanized versions of two neutralizing mAbs specific for the E2 glycoprotein, 1A3B-7 and 1A4A-1, administered singly protected mice against aerosolized VEEV.

Cross-reactive neutralizing human survivor monoclonal antibody BDBV223 targets the ebolavirus stalk.

Three Ebolavirus genus viruses cause lethal disease and lack targeted therapeutics: Ebola virus, Sudan virus and Bundibugyo virus. Monoclonal antibody (mAb) cocktails against the surface glycoprotein (GP) present a potential therapeutic strategy. Here we report two crystal structures of the antibody BDBV223, alone and complexed with its GP2 stalk epitope, an interesting site for therapeutic/vaccine design due to its high sequence conservation among ebolaviruses.

Structural basis of broad ebolavirus neutralization by a human survivor antibody.

The structural features that govern broad-spectrum activity of broadly neutralizing anti-ebolavirus antibodies (Abs) outside of the internal fusion loop epitope are currently unknown. Here we describe the structure of a broadly neutralizing human monoclonal Ab (mAb), ADI-15946, which was identified in a human survivor of the 2013-2016 outbreak. The crystal structure of ADI-15946 in complex with cleaved Ebola virus glycoprotein (EBOV GP) reveals that binding of the mAb structurally mimics the conserved interaction between the EBOV GP core and its glycan cap β17-β18 loop to inhibit infection.

Development of a Human Antibody Cocktail that Deploys Multiple Functions to Confer Pan-Ebolavirus Protection.

Passive administration of monoclonal antibodies (mAbs) is a promising therapeutic approach for Ebola virus disease (EVD). However, all mAbs and mAb cocktails that have entered clinical development are specific for a single member of the Ebolavirus genus, Ebola virus (EBOV), and ineffective against outbreak-causing Bundibugyo virus (BDBV) and Sudan virus (SUDV). Here, we advance MBP134, a cocktail of two broadly neutralizing human mAbs, ADI-15878 from an EVD survivor and ADI-23774 from the same survivor but specificity-matured for SUDV GP binding affinity, as a candidate pan-ebolavirus therapeutic.

Structural Basis of Pan-Ebolavirus Neutralization by a Human Antibody against a Conserved, yet Cryptic Epitope.

Only one naturally occurring human antibody has been described thus far that is capable of potently neutralizing all five ebolaviruses. Here we present two crystal structures of this rare, pan-ebolavirus neutralizing human antibody in complex with Ebola virus and Bundibugyo virus glycoproteins (GPs), respectively. The structures delineate the key protein and glycan contacts for binding that are conserved across the ebolaviruses, explain the antibody's unique broad specificity and neutralization activity, and reveal the likely mechanism behind a known escape mutation in the fusion loop region of GP2.

Humoral immune response to adenovirus induce tolerogenic bystander dendritic cells that promote generation of regulatory T cells.

Following repeated encounters with adenoviruses most of us develop robust humoral and cellular immune responses that are thought to act together to combat ongoing and subsequent infections. Yet in spite of robust immune responses, adenoviruses establish subclinical persistent infections that can last for decades. While adenovirus persistence pose minimal risk in B-cell compromised individuals, if T-cell immunity is severely compromised reactivation of latent adenoviruses can be life threatening.

The Ebola Virus VP30-NP Interaction Is a Regulator of Viral RNA Synthesis.

Filoviruses are capable of causing deadly hemorrhagic fevers. All nonsegmented negative-sense RNA-virus nucleocapsids are composed of a nucleoprotein (NP), a phosphoprotein (VP35) and a polymerase (L). However, the VP30 RNA-synthesis co-factor is unique to the filoviruses.

A Single Maturation Cleavage Site in Adenovirus Impacts Cell Entry and Capsid Assembly.

Unlabelled: Proteolytic maturation drives the conversion of stable, immature virus particles to a mature, metastable state primed for cell infection. In the case of human adenovirus, this proteolytic cleavage is mediated by the virally encoded protease AVP. Protein VI, an internal capsid cement protein and substrate for AVP, is cleaved at two sites, one of which is near the N terminus of the protein.

Inhibition of adenovirus replication by a trisubstituted piperazin-2-one derivative.

The number of disseminated adenovirus (Ad) infections continues to increase mostly due to the growing use of immunosuppressive treatments. Recipients of solid organ or hematopoietic stem cell transplants, mainly in pediatric units, exhibit a high morbidity and mortality due to these infections. Unfortunately, there are no Ad-specific antiviral drugs currently approved for medical use.

The delta domain of the HK97 major capsid protein is essential for assembly.

The 102 residue N-terminal extension of the HK97 major capsid protein, the delta domain, is normally present during the assembly of immature HK97 procapsids, but it is removed during maturation like well-known internal scaffolding proteins of other tailed phages and herpesviruses. The delta domain also shares other unusual properties usually found in other viral and phage scaffolding proteins, including its location on the inside of the capsid, a high predicted and measured α-helical content, and an additional prediction for the ability to form parallel coiled-coils. Viral scaffolding proteins are essential for capsid assembly and phage viability, so we tested whether the HK97 delta domain was essential for capsid assembly.

The cleaved N-terminus of pVI binds peripentonal hexons in mature adenovirus.

Mature human adenovirus particles contain four minor capsid proteins, in addition to the three major capsid proteins (penton base, hexon and fiber) and several proteins associated with the genomic core of the virion. Of the minor capsid proteins, VI plays several crucial roles in the infection cycle of the virus, including hexon nuclear targeting during assembly, activation of the adenovirus proteinase (AVP) during maturation and endosome escape following cell entry. VI is translated as a precursor (pVI) that is cleaved at both N- and C-termini by AVP.

Adenovirus composition, proteolysis, and disassembly studied by in-depth qualitative and quantitative proteomics.

Using high-resolution MS-based proteomics in combination with multiple protease digestion, we profiled, with on average 90% sequence coverage, all 13 viral proteins present in an human adenovirus (HAdV) vector. This in-depth profile provided multiple peptide-based evidence on intrinsic protease activity affecting several HAdV proteins. Next, the generated peptide library was used to develop a targeted proteomics method using selected reaction monitoring (SRM) aimed at quantitative profiling of the stoichiometry of all 13 proteins present in the HAdV.

Disulfide-bond formation by a single cysteine mutation in adenovirus protein VI impairs capsid release and membrane lysis.

The internal capsid protein VI mediates adenovirus (AdV) endosome penetration during cell entry. Essential to this process is the release of protein VI from the AdV capsid and subsequent membrane targeting and insertion by the liberated VI molecules within the endocytic vesicle. In this study, we describe a human AdV (HAdV) substitution mutant (AdV VI-G48C) within the critical N-terminal amphipathic α-helical domain of protein VI.

Viral weapons of membrane destruction: variable modes of membrane penetration by non-enveloped viruses.

Significant progress has recently been obtained in our understanding of cellular entry by nonenveloped viruses (NEVs). A key step in the entry process involves the disruption or remodeling of the limiting cell membrane allowing the virus to gain access to the cellular replication machinery. Biochemical, genetic and structural data from diverse virus groups have shed light on the process of membrane penetration thereby revealing both the conservation and divergence of the mechanisms and principles governing this process.

Functional genetic and biophysical analyses of membrane disruption by human adenovirus.

The identification of the adenovirus (AdV) protein that mediates endosome penetration during infection has remained elusive. Several lines of evidence from previous studies suggest that the membrane lytic factor of AdV is the internal capsid protein VI. While these earlier results imply a role for protein VI in endosome disruption, direct evidence during cell entry has not been demonstrated.

Virus capsid expansion driven by the capture of mobile surface loops.

The capsids of tailed-DNA bacteriophages first assemble as procapsids, which mature by converting into a new form that is strong enough to contain a densely packed viral chromosome. We demonstrate that the intersubunit crosslinking that occurs during maturation of HK97 capsids actually promotes the structural transformation. Small-angle X-ray scattering and crosslinking assays reveal that a shift in the crosslink pattern accompanies conversion of a semimature particle, Expansion Intermediate-I/II, to a more mature state, Balloon.