Biology subjects

Thannickal, S.

Publications and source records attributed to Thannickal, S..

3 recordsLinked to original sources

bioRxiv2026

GM-CSF and M-CSF Driven Differentiation Differentially Regulates Chikungunya Virus Infection and Antiviral Responses in Human Monocyte-Derived Macrophages

Chikungunya virus is an arthritogenic alphavirus causing debilitating joint pain in infected individuals. The mechanisms driving CHIKV-associated arthralgia is poorly understood, however, macrophages have been implicated as potential reservoirs of persistent viral material and mediators of immunopathology. Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) and Macrophage-Colony Stimulating Factor (M-CSF) are cytokines that serve as myeloid growth factors that bias macrophages toward pro-inflammatory and anti-inflammatory phenotypes, respectively. In this study, we examined how cytokine-driven macrophage differentiation via GM-CSF and M-CSF influences susceptibility to and responses against CHIKV infection in vitro. Using parallel donor-matched cultures of primary macrophages, we show that GM-CSF-differentiated macrophages are highly permissive to CHIKV and Mayaro virus (MAYV) infection and support robust viral replication, whereas M-CSF-differentiated macrophages are resistant to CHIKV replication and lack detectable levels of viral protein expression. Despite these differences, we observed pro-inflammatory, M1-skewing of CHIKV-infected macrophages, regardless of differentiation state. Interestingly, we observe higher production of IFN and IP10/CXCL10 in M-CSF differentiated macrophages, suggesting that M-CSF promotes an antiviral state that restricts CHIKV infection. Stimulation of macrophages with double-stranded RNA (polyinosinic:polycytidylic acid; poly(I:C)), but not with single-stranded RNA (resiquimod, R848), recapitulated the antiviral cytokine and chemokine response induced by CHIKV infection. These findings suggest that dsRNA sensing plays a more prominent role than ssRNA sensing in driving the macrophage antiviral response to CHIKV. Together, these findings highlight macrophage differentiation as a critical determinant of CHIKV susceptibility and antiviral immunity in humans, with implications for understanding inflammatory pathogenesis during infection.

microbiology↗

bioRxiv2024

Evolution of antiviral resistance captures a transient interdomain functional interaction between chikungunya virus envelope glycoproteins

Envelope proteins drive virus and host-cell membrane fusion to achieve virus entry. Fusogenic proteins are classified into structural classes that function with remarkable mechanistic similarities. Fusion proceeds through coordinated movements of protein domains in a sequence of orchestrated steps. Structures for the initial and final conformations are available for several fusogens, but folding intermediates have largely remained unresolved and interdependency between regions that drive conformational rearrangements is not well understood. Chikungunya virus (CHIKV) particles display heterodimers of envelope proteins E1 and E2 associated as trimeric spikes that respond to acidic pH to trigger fusion. We have followed experimental evolution of CHIKV under the selective pressure of a novel small-molecule entry inhibitor. Mutations arising from selection mapped to two residues located in distal domains of E2 and E1 heterodimer and spikes. Here, we pinpointed the antiviral mode of action to inhibition of fusion. Phenotypic characterization of recombinant viruses indicated that the selected mutations confer a fitness advantage under antiviral pressure, and that the double-mutant virus overcame antiviral inhibition of fusion while single-mutants were sensitive. Further supporting a functional connection between residues, the double-mutant virus displayed a higher pH-threshold for fusion than single-mutant viruses. Finally, mutations implied distinct outcomes of replication and spreading in mice, and infection rates in mosquitoes underscoring the fine-tuning of envelope protein function as a determinant for establishment of infection. Together with molecular dynamics simulations that indicate a link between these two residues in the modulation of the heterodimer conformational rearrangement, our approach captured an otherwise unresolved interaction. ImportanceCHIKV is a reemergent pathogen that has caused large outbreaks in the twenty years. There are no available antiviral therapies and a vaccine has only recently been approved. Here, we describe the mode of action of a novel inhibitor designed against CHIKV envelope proteins heterodimer that blocks entry at the stage of fusion between virus and host membranes. Fusion is common to the entry of enveloped viruses. Virus envelope proteins drive fusion undergoing a series of transitions from an initial metastable conformational state to a more stable post-fusion state. Intermediate conformations are transient and have mostly remained inaccessible to structure determination. In this study, directed evolution of resistance to antiviral inhibition of fusion uncovered a functional interaction between two residues residing in domains that are apart in both the pre-fusion and post-fusion states. Thus, our approach allowed gaining insight into the molecular detail of the inner working of virus fusion machinery.

microbiology↗

bioRxiv2021

Combination of a Sindbis-SARS-CoV-2 spike vaccine and αOX40 antibody elicits protective immunity against SARS-CoV-2 induced disease and potentiates long-term SARS-CoV-2-specific humoral and T-cell immunity

The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 is a major global public threat. Currently, a worldwide effort has been mounted to generate billions of effective SARS-CoV-2 vaccine doses to immunize the worlds population at record speeds. However, there is still demand for alternative effective vaccines that rapidly confer long-term protection and rely upon cost-effective, easily scaled-up manufacturing. Here, we present a Sindbis alphavirus vector (SV), transiently expressing the SARS-CoV-2 spike protein (SV.Spike), combined with the OX40 immunostimulatory antibody (OX40) as a novel, highly effective vaccine approach. We show that SV.Spike plus OX40 elicits long-lasting neutralizing antibodies and a vigorous T-cell response in mice. Protein binding, immunohistochemical and cellular infection assays all show that vaccinated mice sera inhibits spike functions. Immunophenotyping, RNA Seq transcriptome profiles and metabolic analysis indicate a reprogramming of T-cells in vaccinated mice. Activated T-cells were found to mobilize to lung tissue. Most importantly, SV.Spike plus OX40 provided robust immune protection against infection with authentic coronavirus in transgenic mice expressing the human ACE2 receptor (hACE2-Tg). Finally, our immunization strategy induced strong effector memory response, potentiating protective immunity against re-exposure to SARS-CoV-2 spike protein. Our results show the potential of a new Sindbis virus-based vaccine platform to counteract waning immune response that can be used as a new candidate to combat SARS-CoV-2. Given the strong T-cell responses elicited, our vaccine is likely to be effective against variants that are proving challenging, as well as, serve as a platform to develop a broader spectrum pancoronavirus vaccine. Similarly, the vaccine approach is likely to be applicable to other pathogens.

immunology↗