Biology subjects

Biswas, B.

Publications and source records attributed to Biswas, B..

3 recordsLinked to original sources

bioRxiv2020

A recombinant fragment of Human surfactant protein D binds Spike protein and inhibits infectivity and replication of SARS-CoV-2 in clinical samples

RationaleCOVID-19 is an acute infectious disease caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Human surfactant protein D (SP-D) is known to interact with spike protein of SARS-CoV, but its immune-surveillance against SARS-CoV-2 is not known. ObjectiveThis study aimed to examine the potential of a recombinant fragment of human SP-D (rfhSP-D) as an inhibitor of replication and infection of SARS-CoV-2. MethodsrfhSP-D interaction with spike protein of SARS-CoV-2 and hACE-2 receptor was predicted via docking analysis. The inhibition of interaction between spike protein and ACE-2 by rfhSP-D was confirmed using direct and indirect ELISA. The effect of rfhSP-D on replication and infectivity of SARS-CoV-2 from clinical samples was studied by measuring the expression of RdRp gene of the virus using qPCR. Measurements and Main ResultsIn-silico interaction studies indicated that three amino acid residues in the RBD of spike of SARS-CoV-2 were commonly involved in interacting with rfhSP-D and ACE-2. Studies using clinical samples of SARS-CoV-2 positive cases (asymptomatic, n=7 and symptomatic, n=8 and negative controls n=15) demonstrated that treatment with 5M rfhSP-D inhibited viral replication by ~5.5 fold and was more efficient than Remdesivir (100 M). Approximately, a 2-fold reduction in viral infectivity was also observed after treatment with 5M rfhSP-D. ConclusionsThese results conclusively demonstrate that the calcium independent rfhSP-D mediated inhibition of binding between the receptor binding domain of the S1 subunit of the SARS-CoV-2 spike protein and human ACE-2, its host cell receptor, and a significant reduction in SARS-CoV-2 infection and replication in-vitro.

immunology↗

bioRxiv2020

Identification and characterisation of the gene encoding an amastine-like surface protein (ALSP) in the Leishmania donovani genome: a putative anti-leishmanial drug target

In the current study, a novel putative protein of Leishmania donovani, amastin-like surface protein (ALSP) has been characterized. The gene was cloned in a bacterial system and the protein was overexpressed. A polyclonal antibody was developed against the protein, which detected a 10 kDa band in the L. donovani amastigote. ALSP mRNA was detected in L. donovani amastigote, which was not expressed in the promastigote. ALSP mRNA was not expressed in either morphological forms of Leishmania major. MALDI-TOF confirmed the molecular weight of ALSP as 10 kDa. I-TASSER predicted the function of ALSP as a lipase, which was confirmed by preliminary in-vitro experiments using amastigotes of L. donovani. ALSP has GAS amino acid sequences, which might act as the active site for its lipase activity. The selective expression of ALSP in amastigotes probably makes it important in virulence mechanisms such as survival in the phagolysosome and modulation of its membrane and other metabolic functions, necessary for parasite survival in the human host. ALSP can act as a peptide vaccine target and maybe detected in the peripheral blood or urine as a molecular biomarker of active disease in visceral leishmaniasis.

molecular biology↗

bioRxiv2020

HIV-1 Gag protein with or without p6 specifically dimerizes on the viral RNA packaging signal

The HIV-1 Gag protein is responsible for genomic RNA (gRNA) packaging and immature viral particle assembly. While the presence of gRNA in virions is required for viral infectivity, in its absence, Gag can assemble around cellular RNAs and form particles resembling gRNA-containing particles. When gRNA is expressed, it is selectively packaged despite the presence of excess host RNA, but how it is selectively packaged is not understood. Specific recognition of a gRNA packaging signal (Psi) has been proposed to stimulate the efficient nucleation of viral assembly. However, the heterogeneity of Gag-RNA interactions renders capturing this transient nucleation complex using traditional structural biology approaches challenging. Here, we used native mass spectrometry to investigate RNA binding of wild-type Gag and Gag lacking the p6 domain (Gag{Delta}p6). Both proteins bind to Psi RNA primarily as dimers, but to a control RNA primarily as monomers. The dimeric complexes on Psi RNA require an intact dimer interface within Gag. Gag{Delta}p6 binds to Psi RNA with high specificity in vitro and also selectively packages gRNA in particles produced in mammalian cells. These studies provide direct support for the idea that Gag binding to Psi specifically nucleates Gag-Gag interactions at the early stages of immature viral particle assembly in a p6-independent manner.

biochemistry↗