Biology subjects

Mazurov, D.

Publications and source records attributed to Mazurov, D..

4 recordsLinked to original sources

bioRxiv2023

Alternative substitutions of N332 in HIV-1AD8 gp120 differentially affect envelope glycoprotein function and viral sensitivity to broadly neutralizing antibodies targeting the V3-glycan

The envelope glycoprotein (Env) trimer on the surface of human immunodeficiency virus type I (HIV-1) mediates viral entry into host CD4+ T cells and is the sole target of neutralizing antibodies. Broadly neutralizing antibodies (bnAbs) that target gp120 V3-glycan of HIV-1 Env trimer are potent and block the entry of diverse HIV-1 strains. Most V3-glycan bnAbs interact, to a different extent, with a glycan attached to N332 but Asn at this position is not absolutely conserved or required for HIV-1 entry based on prevalence of N332 in different circulating HIV-1 strains from diverse clades. Here, we studied the effects of amino acid changes at position 332 of HIV-1AD8 Envs on HIV-1 sensitivity to antibodies, cold exposure, and soluble CD4. We further investigated how these changes affect Env function and HIV-1 infectivity in vitro. Our results suggest robust tolerability of HIV-1 AD8 Env N332 to changes with specific changes that resulted in extended exposure of gp120 V3 loop, which is typically concealed in most primary HIV-1 isolates. Viral evolution leading to Asn at position 332 of HIVAD8 Envs is supported by the selection advantage of high levels of cell-cell fusion, transmission, and infectivity even though cell surface expression levels are lower than most N332 variants. Thus, tolerance of HIV-1AD8 Envs to different amino acids at position 332 provides increased flexibility to respond to changing conditions/environments and to evade the immune system. Modeling studies of the distance between N332 glycan and specific bnAbs was in agreement with N332 glycan dependency on bnAb neutralization. Overall, our studies provide insights into the contribution of specific amino acids at position 332 to Env antigenicity, stability on ice, and conformational states.

microbiology↗

bioRxiv2023

Ultrasensitive quantification of HIV-1 cell-to-cell transmission in primary human CD4+ T cells measures viral sensitivity to broadly neutralizing antibodies

HIV-1 efficiently replicates in vivo by direct transmission from infected to uninfected CD4+ T cells at confined local sites designated virological synapses (VSs). VSs are formed by cell junctions between HIV-1 envelope glycoproteins (Envs) on an infected cell and CD4 on an uninfected cell. These sites facilitate highly efficient viral transmission and contribute to HIV-1 evasion from neutralizing antibodies, but accurate quantification of the efficiency of cell-cell transmission is still challenging. Here, we developed an ultrasensitive HIV-1 cell- to-cell transmission assay that triggers the expression of the nanoluciferase (nluc) gene in target cells upon transmission and after reverse transcription of the HIV-1 RNA genome. The assay is based on insertion of the nluc gene in an antisense orientation into HIV-1 provirus; Nluc expression is blocked in virus-producing cells because the nluc gene contains an intron that can be efficiently spliced out only when mRNA is transcribed from the opposite (sense) strand. Thus, only sense mRNA that is spliced and subsequently reversed transcribed during transmission to target cells will support Nluc expression. Assay optimization resulted in a very low background, >99% splicing efficiency, high sensitivity and wide dynamic range for detection of cell-cell transmission in T cell lines and primary CD4+ T cells. The new reporter vector can detect cell-cell transmission using single-round viral vectors and HIV-1 molecular clones, which provide viral proteins of different HIV-1 strains, and reproducibly measures sensitivity of HIV-1 transmission to antibody neutralization in vitro. This assay will contribute to understanding fundamental mechanisms of HIV-1 cell-to-cell transmission, allow evaluation of pre-existing or acquired HIV-1 resistance in clinical trials, and can be adapted to study other retroviruses.

microbiology↗

bioRxiv2021

SARS-CoV-2 cell-to-cell infection is resistant to neutralizing antibodies

The COVID-19 pandemic caused by SARS-CoV-2 has posed a global threat to human lives and economics. One of the best ways to determine protection against the infection is to quantify the neutralizing activity of serum antibodies. Multiple assays have been developed to validate SARS-CoV-2 neutralization; most of them utilized lentiviral or vesicular stomatitis virus-based particles pseudotyped with the spike (S) protein, making them safe and acceptable to work with in many labs. However, these systems are only capable of measuring infection with purified particles. This study has developed a pseudoviral assay with replication-dependent reporter vectors that can accurately quantify the level of infection directly from the virus producing cell to the permissive target cell. Comparative analysis of cell-free and cell-to-cell infection revealed that the neutralizing activity of convalescent sera was more than tenfold lower in cell cocultures than in the cell-free mode of infection. As the pseudoviral system could not properly model the mechanisms of SARS-CoV-2 transmission, similar experiments were performed with replication-competent coronavirus, which detected nearly complete SARS-CoV-2 cell-to-cell infection resistance to neutralization by convalescent sera. Based on available studies, this is the first attempt to quantitatively measure SARS-CoV-2 cell-to-cell infection, for which the mechanisms are largely unknown. The findings suggest that this route of SARS-CoV-2 transmission could be of great importance for treatment and prevention of COVID-19. ImportanceImmune surveillance of viral or bacterial infections is largely mediated by neutralizing antibodies. Antibodies against the SARS-CoV-2 spike protein are produced after vaccination or infection, but their titers only partly reflect the degree of protection against infection. To identify protective antibodies, a neutralization test with replicating viruses or pseudoviruses (PVs) is required. This study developed lentiviral-based PV neutralization assays that, unlike similar systems reported earlier, enable quantitative measurement of SARS-CoV-2 neutralization in cell cocultures. Using both PVs and replication-competent virus, it was demonstrated that SARS-CoV-2 cell-to-cell infection is considerably more resistant to serum neutralization than infection with purified viral particles. The tests are easy to set up in many labs, and are believed to be more informative for monitoring SARS-CoV-2 collective immunity or entry inhibitor screening.

microbiology↗

bioRxiv2021

Engineering T cell resistance to HIV-1 infection via knock-in of peptides from the heptad repeat 2 domain of gp41

Previous studies suggest that short peptides from the heptad repeat 2 (HR2) domain of gp41 expressed on the cell surface are more potent inhibitors of HIV-1 entry than soluble analogs. However, their therapeutic potential has only been examined using lentiviral vectors. Here, we aimed to develop CRISPR/Cas9-based fusion inhibitory peptide knock-in (KI) technology for the generation and selection of HIV-1-resistant T cells. First, we cloned a series of HIV-1 fusion inhibitory peptides and embedded them in CD52, the shortest GPI-anchored protein, which efficiently delivers epitope tags to the cell surface and maintains a sufficient level of KI. Among the seven peptides tested, MT-C34, HP-23L, and 2P23 exhibited significant activity against both cell-free and cell-to-cell HIV-1 infection. Unlike membrane-bound peptides, the shed variant of MT-C34 provided insufficient protection against HIV-1 due to its low concentrations in the culture medium. Using Cas9 plasmids or ribonucleoprotein electroporation and cell sorting with antibodies raised against gp41 peptides, we generated CEM/R5 cells with biallelic KI of MT-C34 (embedded in CD52 for expression in lipid rafts) and 2P23 (N-terminally fused to CXCR4). In combination, these peptides provided a higher level of protection than individual KI. By extending homology arms and substituting PCR donor DNA with a plasmid containing signals for nuclear localization, we achieved KI of MT-C34 into CXCR4 loci and HIV-1 proviral DNA at levels of up to 35% in CEM/R5 cells and increased KI occurrence from undetectable to 4-5% in CD4 lymphocytes. Comparative analysis of lentiviral and HDR-based delivery strategies showed that KI led to the higher MT-C34 expression and stronger protection of primary CD4 lymphocytes from HIV-1 than lentiviral transduction, albeit the efficiency of KI needs further improvements in order to meet clinical requirements. Thus, the developed CRISPR/Cas9 platform offers a new opportunity for antiviral peptide delivery with a concomitant precise genetic modification of targeted locus that can be employed to strengthen cell protection against HIV. AUTHOR SUMMARYHIV is a human lentivirus that infects CD4-positive immune cells and, when left untreated, manifests in the fatal disease known as acquired immunodeficiency syndrome. Antiretroviral therapy (ART) is not leading to viral clearance, and HIV persists in the organism as a latent provirus. One way to control infection is to increase the population of HIV-resistant CD4 lymphocytes via entry molecule knockout or expression of different antiviral genes. Peptides from the heptad repeat (HR) domain of gp41 are potent inhibitors of HIV-1 fusion, especially when designed to express on the cell surface. Individual gp41 peptides encoded by therapeutic lentiviral vectors have been evaluated and some have entered clinical trials. However, a CRISPR/Cas9-based gp41 peptide delivery platform that operates through concomitant target gene modification has not yet been developed due to low knock-in (KI) rates in primary cells. Here, we systematically evaluated the antiviral activity of different HR2-peptides cloned into the shortest carrier molecule, CD52. The resulting small-size transgene constructs encoding selected peptides, in combination with improvements to enhance donor vector nuclear import, helped to overcome precise editing restrictions in CD4 lymphocytes. Using KI into CXCR4, we demonstrated different options for target gene modification, effectively protecting edited cells against HIV-1.

microbiology↗