Biology subjects

Kalveram, B. K.

Publications and source records attributed to Kalveram, B. K..

3 recordsLinked to original sources

bioRxiv2025

De novo recovery of Ghana virus, an African bat Henipavirus, reveals differential tropism and attenuated pathogenicity compared to Nipah virus

Henipaviruses (HNVs) like Nipah (NiV) and Hendra (HeV) viruses represent severe zoonotic threats. Ghana virus (GhV), identified in 2012, is the only African bat henipavirus with a near-complete genome assembly. However, without isolates in culture, GhV biology, pathogenicity, and zoonotic potential remain poorly understood. Using reverse genetics, we recovered a full-length infectious clone of GhV at BSL-4 following rational reconstruction of its incomplete 3' leader and modification of a non-canonical transcriptional initiation site. GhV demonstrated restricted receptor tropism (ephrin-B2 but not ephrin-B3) and distinct innate immune antagonism. Replication was attenuated in primary human cells, but was enhanced in bat cells. In Syrian golden hamsters, GhV infection caused no disease or mortality. Furthermore, a chimeric NiV encoding the GhV receptor-binding protein was completely attenuated in vivo, implicating ephrin-B3 receptor usage as a critical determinant of HNV pathogenesis. These findings elucidate GhV zoonotic potential and inform strategies for virus surveillance and control. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/679836v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@1e5addcorg.highwire.dtl.DTLVardef@1f96850org.highwire.dtl.DTLVardef@12f842eorg.highwire.dtl.DTLVardef@8f013c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

SARS-CoV-2 Uses Nonstructural Protein 16 to Evade Restriction by IFIT1 and IFIT3

Understanding the molecular basis of innate immune evasion by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important consideration for designing the next wave of therapeutics. Here, we investigate the role of the nonstructural protein 16 (NSP16) of SARS-CoV-2 in infection and pathogenesis. NSP16, a ribonucleoside 2-O methyltransferase (MTase), catalyzes the transfer of a methyl group to mRNA as part of the capping process. Based on observations with other CoVs, we hypothesized that NSP16 2-O MTase function protects SARS-CoV-2 from cap-sensing host restriction. Therefore, we engineered SARS-CoV-2 with a mutation that disrupts a conserved residue in the active site of NSP16. We subsequently show that this mutant is attenuated both in vitro and in vivo, using a hamster model of SARS-CoV-2 infection. Mechanistically, we confirm that the NSP16 mutant is more sensitive to type I interferon (IFN-I) in vitro. Furthermore, silencing IFIT1 or IFIT3, IFN-stimulated genes that sense a lack of 2-O methylation, partially restores fitness to the NSP16 mutant. Finally, we demonstrate that sinefungin, a methyltransferase inhibitor that binds the catalytic site of NSP16, sensitizes wild-type SARS-CoV-2 to IFN-I treatment. Overall, our findings highlight the importance of SARS-CoV-2 NSP16 in evading host innate immunity and suggest a possible target for future antiviral therapies. ImportanceSimilar to other coronaviruses, disruption of SARS-CoV-2 NSP16 function attenuates viral replication in a type I interferon-dependent manner. In vivo, our results show reduced disease and viral replication at late times in the hamster lung, but an earlier titer deficit for the NSP16 mutant (dNSP16) in the upper airway. In addition, our results confirm a role for IFIT1, but also demonstrate the necessity of IFIT3 in mediating dNSP16 attenuation. Finally, we show that targeting NSP16 activity with a 2-O methyltransferase inhibitor in combination with type I interferon offers a novel avenue for antiviral development.

microbiology↗

bioRxiv2022

Engineering SARS-CoV-2 cocktail antibodies into a bispecific format improves neutralizing potency and breadth

One major limitation of neutralizing antibody-based COVID-19 therapy is the requirement of costly cocktails to reduce antibody resistance. We engineered two bispecific antibodies (bsAbs) using distinct designs and compared them with parental antibodies and their cocktail. Single molecules of both bsAbs block the two epitopes targeted by parental antibodies on the receptor-binding domain (RBD). However, bsAb with the IgG-(scFv)2 design (14-H-06) but not the CrossMAb design (14-crs-06) increases antigen-binding and virus-neutralizing activities and spectrum against multiple SARS-CoV-2 variants including the Omicron, than the cocktail. X-ray crystallography and computational simulations reveal distinct neutralizing mechanisms for individual cocktail antibodies and suggest higher inter-spike crosslinking potentials by 14-H-06 than 14-crs-06. In mouse models of infections by SARS-CoV-2 and the Beta, Gamma, and Delta variants, 14-H-06 exhibits higher or equivalent therapeutic efficacy than the cocktail. Rationally engineered bsAbs represent a cost-effective alternative to antibody cocktails and a promising strategy to improve potency and breadth.

microbiology↗