James Earnest

Emory University | EU

Several vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been approved for controlling the coronavirus disease 2019 (COVID-19) pandemic worldwide. Antibody response is essential to understand the immune response to different viral targets after vaccination with different vaccine platforms. Thus, the main aim of thi...

Significance Arthritogenic alphaviruses, such as Chikungunya virus (CHIKV) and Mayaro virus (MAYV), cause febrile illness, rash, and a debilitating chronic polyarthritis in humans. Currently, there are no approved vaccines or antiviral therapies for the prevention or treatment of alphavirus infection. Here, we identified and characterized 33 monocl...

Alphaviruses are emerging, mosquito-transmitted pathogens that cause musculoskeletal and neurological disease in humans. Although neutralizing antibodies that inhibit individual alphaviruses have been described, broadly reactive antibodies that protect against both arthritogenic and encephalitic alphaviruses have not been reported. Here, we identif...

Although neutralizing monoclonal antibodies (mAbs) against epitopes within the alphavirus E2 protein can protect against infection, the functional significance of non-neutralizing mAbs is poorly understood. Here, we evaluate the activity of 13 non-neutralizing mAbs against Mayaro virus (MAYV), an emerging arthritogenic alphavirus. These mAbs bind t...

Venezuelan equine encephalitis virus (VEEV) is a neurotropic alphavirus transmitted by mosquitoes that causes encephalitis and death in humans¹. VEEV is a biodefence concern because of its potential for aerosol spread and the current lack of sufficient countermeasures. The host factors that are required for VEEV entry and infection remain poorly ch...

Significance Chikungunya virus (CHIKV) is a significant human pathogen that causes debilitating and long-lasting arthritis. Currently, there is no approved vaccine or specific therapeutic. We show that two highly potent anti-CHIKV antibodies—CHK-124 and CHK-263—can inhibit multiple steps of the CHIKV infection cycle and determined their cryogenic e...

Although animal models have been evaluated for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, none have fully recapitulated the lung disease phenotypes seen in humans who have been hospitalized. Here, we evaluate transgenic mice expressing the human angiotensin I-converting enzyme 2 (ACE2) receptor driven by the cytokeratin...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Severe Acute Respiratory Syndrome Coronavirus -2 (SARS-CoV-2) emerged in late 2019 and has spread worldwide resulting in the Coronavirus Disease 2019 (COVID-19) pandemic. Although animal models have been evaluated for SARS-CoV-2 infection, none have recapitulated the severe lung disease phenotypes seen in hospitalized human cases. Here, we evaluate...

Despite causing outbreaks of fever and arthritis in multiple countries, no countermeasures exist against Mayaro virus (MAYV), an emerging mosquito-transmitted alphavirus. We generated 18 neutralizing mAbs against MAYV, 11 of which had “elite” activity that inhibited infection with EC 50 values of <10 ng/ml. Antibodies with the greatest inhibitory c...

Mxra8 is a recently described receptor for multiple alphaviruses, including Chikungunya (CHIKV), Mayaro (MAYV), Ross River (RRV), and O'nyong nyong (ONNV) viruses. To determine its role in pathogenesis, we generated mice with mutant Mxra8 alleles: an 8-nucleotide deletion that produces a truncated, soluble form (Mxra8Δ8/Δ8) and a 97-nucleotide dele...

Host factors render cells susceptible to viral infection. One family of susceptibility factors, the tetraspanin proteins, facilitate enveloped virus entry by promoting virus-cell membrane fusion. They also facilitate viral egress from infected cells. In this article, we discuss recent insights into how tetraspanins assemble viral entry and exit pla...

Mayaro is a mosquito-borne single-stranded positive RNA alphavirus endemic to tropical regions of South America. It is closely related to other arthritogenic alphaviruses, such as Chikungunya, Semliki Forest, Ross River, and Sindbis viruses. Although there are currently no available vaccines or therapies for alphaviruses, previous studies demonstra...

Infection by enveloped coronaviruses (CoVs) initiates with viral spike (S) proteins binding to cellular receptors, and is followed by proteolytic cleavage of receptor-bound S proteins, which prompts S protein-mediated virus-cell membrane fusion. Infection therefore requires close proximity of receptors and proteases. We considered whether tetraspan...

CoV Transduction of CD81KO 293T cells. 293T WT or CD81KO cells were transfected with appropriate receptors with or without CD81. These cells were transduced with HIV pseudoviruses carrying the S proteins of MERS (A), 229E (B), SARS (C), or MHV(D). Pseudovirus transduction was measured using luciferase assay. (TIF)

Effects of CD9 and TMPRSS2 expression on MERSpp entry in cells with endogenous DPP4. 293-WT (black) or 293-CD9KO (gray) cells were transfected with an empty vector (EV), CD9 (A), or TMPRSS2 (B) before transduction with MERSpp. MERSpp entry was measured by luciferase assay. (TIF)

Relative expression of CD9, DPP4, TMPRSS2 and HPRT in HeLa and human airway epithelia cells. (TIF)

Amino acid substitutions in MERS mutants. (TIF)

Association of tetraspanins with CHAPS-resistant membranes. 293T WT, CD9KO, and CD81KO cells were analyzed for tetraspanin distribution following differential centrifugation of CHAPS lysates. The CD9KO and CD81KO cells were complemented with the appropriate tetraspanins by transfection. (TIF)

Entry kinetics of MERS-EMCpp in tetraspanin KO cells. The entry kinetics of MERSpps were measured in 293T WT, CD9KO (A), and CD81KO (B) cells. Cells were bound with MERSpps and incubated with entry inhibiting protease cocktail at the indicated time point. Luciferase levels were measured and plotted relative to untreated control cells. Entry kinetic...

Significance Middle East respiratory syndrome, caused by a zoonotically transmitted coronavirus (MERS-CoV), has a high mortality (∼36%). Because of limited autopsy data on tissues from MERS fatalities, a small animal model can provide an important tool to better understand the disease. We humanized the mouse locus of the virus receptor DPP4, preser...

Unlabelled: Coronaviruses (CoVs) and low-pathogenicity influenza A viruses (LP IAVs) depend on target cell proteases to cleave their viral glycoproteins and prime them for virus-cell membrane fusion. Several proteases cluster into tetraspanin-enriched microdomains (TEMs), suggesting that TEMs are preferred virus entry portals. Here we found that s...