Virus

About: Virus is a research topic. Over the lifetime, 136914 publications have been published within this topic receiving 5209107 citations. The topic is also known as: infectious agent & viruses.

SARS-CoV-2 invades host cells via a novel route: CD147-spike protein

Abstract: SUMMARY Currently, COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been widely spread around the world; nevertheless, so far there exist no specific antiviral drugs for treatment of the disease, which poses great challenge to control and contain the virus. Here, we reported a research finding that SARS-CoV-2 invaded host cells via a novel route of CD147-spike protein (SP). SP bound to CD147, a receptor on the host cells, thereby mediating the viral invasion. Our further research confirmed this finding. First, in vitro antiviral tests indicated Meplazumab, an anti-CD147 humanized antibody, significantly inhibited the viruses from invading host cells, with an EC50 of 24.86 μg/mL and IC50 of 15.16 μg/mL. Second, we validated the interaction between CD147 and SP, with an affinity constant of 1.85×10−7M. Co-Immunoprecipitation and ELISA also confirmed the binding of the two proteins. Finally, the localization of CD147 and SP was observed in SARS-CoV-2 infected Vero E6 cells by immuno-electron microscope. Therefore, the discovery of the new route CD147-SP for SARS-CoV-2 invading host cells provides a critical target for development of specific antiviral drugs.

Influenza A virus M2 protein: monoclonal antibody restriction of virus growth and detection of M2 in virions.

Abstract: The influenza A virus M2 protein is an integral membrane protein of 97 amino acids that is expressed at the surface of infected cells with an extracellular N-terminal domain of 18 to 23 amino acid residues, an internal hydrophobic domain of approximately 19 residues, and a C-terminal cytoplasmic domain of 54 residues. To gain an understanding of the M2 protein function in the influenza virus replicative pathway, we produced and characterized a monoclonal antibody to M2. The antibody-binding site was located to the extracellular N terminus of M2 as shown by the loss of recognition after proteolysis at the infected-cell surface, which removes 18 N-terminal residues, and by the finding that the antibody recognizes M2 in cell surface fluorescence. The epitope was further defined to involve residues 11 and 14 by comparing the predicted amino acid sequences of M2 from several avian and human strains and the ability of the M2 protein to be recognized by the antibody. The M2-specific monoclonal antibody was used in a sensitive immunoblot assay to show that M2 protein could be detected in virion preparations. Quantitation of the amount of M2 associated with virions by two unrelated methods indicated that in the virion preparations used there are 14 to 68 molecules of M2 per virion. The monoclonal antibody, when included in a plaque assay overlay, considerably showed the growth of some influenza virus strains. This plaque size reduction is a specific effect for the M2 antibody as determined by an analysis of recombinants with defined genome composition and by the observation that competition by an N-terminal peptide prevents the antibody restriction of virus growth.

Influenza virus activates inflammasomes via its intracellular M2 ion channel

Abstract: Influenza virus, a negative-stranded RNA virus that causes severe illness in humans and animals, stimulates the inflammasome through the Nod-like receptor NLRP3. However, the mechanism by which influenza virus activates the NLRP3 inflammasome is unknown. Here we show that the influenza virus M2 protein, a proton-selective ion channel important in viral pathogenesis, stimulates the NLRP3 inflammasome pathway. M2 channel activity was required for the activation of inflammasomes by influenza and was sufficient to activate inflammasomes in primed macrophages and dendritic cells. M2-induced activation of inflammasomes required its localization to the Golgi apparatus and was dependent on the pH gradient. Our results show a mechanism by which influenza virus infection activates inflammasomes and identify the sensing of disturbances in intracellular ionic concentrations as a previously unknown pathogen-recognition pathway.

Type-specific neutralization of the human immunodeficiency virus with antibodies to env-encoded synthetic peptides

Abstract: A synthetic peptide (SP-10-IIIB) with an amino acid sequence [Cys-Thr-Arg-Pro-Asn-Asn-Asn-Thr-Arg-Lys-Ser-Ile-Arg-Ile-Gln-Arg-Gly-Pro -Pro-Gly-(Tyr); amino acids 303-321] from the human immunodeficiency virus (HIV) isolate human T-cell lymphotropic virus type III (HTLV-III) HTLV-IIIB envelope glycoprotein gp120 was coupled to tetanus toxoid and used to raise goat antibodies to HIV gp120. Goat anti-SP-10-IIIB serum bound to the surface of HTLV-IIIB-infected CEM T cells but not to the surface of HTLV-IIIRF-infected or uninfected CEM T cells. Anti-SP-10-IIIB antibodies also selectively bound to gp120 from lysates of HTLV-IIIB cells in immunoblot assays. Twenty-one percent of sera (28 of 175) from patients seropositive for HIV contained antibodies that reacted with SP-10-IIIB in RIA. Human anti-SP-10-IIIB antibodies affinity purified from acquired immunodeficiency syndrome (AIDS) patient serum bound to HTLV-IIIB-infected cells and immunoprecipitated gp120. Goat antibodies to SP-10-IIIB neutralized HTLV-IIIB (80% neutralization titer of 1/600), inhibited HTLV-IIIB-induced syncytium formation, but did not neutralize HIV isolates HTLV-IIIRF or HTLV-IIIMN or inhibit syncytium formation with these isolates. Also, goat antiserum to an homologous synthetic peptide [SP-10-IIIRF(A), (Cys)-Arg-Lys-Ser-Ile-Thr-Lys-Gly-Pro-Gly-Arg-Val-Ile-Tyr] from gp120 of HIV isolate HTLV-IIIRF inhibited syncytium formation by HTLV-IIIRF, but did not inhibit syncytium formation by HTLV-IIIB or by HTLV-IIIMN. Thus, the amino acid sequences of SP-10-IIIB and SP-10-IIIRF(A) define homologous regions of gp120 that are important in type-specific virus neutralization. The identification of these type-specific neutralizing epitopes should facilitate the design of a polyvalent, synthetic vaccine for AIDS.

Nevirapine resistance mutations of human immunodeficiency virus type 1 selected during therapy.

Abstract: Drug susceptibility and mutations in the reverse transcriptase (RT) gene were analyzed with 167 virus isolates from 38 patients treated with nevirapine, a potent nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) RT. Resistant isolates emerged quickly and uniformly in all patients administered nevirapine either as monotherapy or in combination with zidovudine (AZT). Resistance developed as early as 1 week, indicating rapid turnover of the virus population. The development of resistance was associated with the loss of antiviral drug activity as measured by CD4 lymphocyte counts and levels of HIV p24 antigen and RNA in serum. In addition to mutations at amino acid residues 103, 106, and 181 that had been identified by selection in cell culture, mutations at residues 108, 188, and 190 were also found in the patient isolates. Sequences from patient clones documented cocirculating mixtures of populations of different mutants. The most common mutation with monotherapy, tyrosine to cysteine at residue 181, was prevented from emerging by coadministration of AZT, which resulted in the selection of alternative mutations. The observations documented that, under selective drug pressure, the circulating virus population can change rapidly, and many alternative mutants can emerge, often in complex mixtures. The addition of a second RT inhibitor, AZT, significantly altered the pattern of mutations in the circulating population of HIV.