Deciphering the Molecular Mechanism of HCV Protease Inhibitor Fluorination as a General Approach to Avoid Drug Resistance

Third generation Hepatitis C virus (HCV) NS3/4A protease inhibitors (PIs), glecaprevir and voxilaprevir, are highly effective across genotypes and against many resistant variants. Unlike earlier PIs, these compounds have fluorine substitutions on the P2-P4 macrocycle and P1 moieties. Fluorination has long been used in medicinal chemistry as a strategy to improve physicochemical properties and potency. However, the molecular basis by which fluorination improves potency and resistance profile of HCV NS3/4A PIs is not well understood. To systematically analyze the contribution of fluorine substitutions to inhibitor potency and resistance profile, we used a multi-disciplinary approach involving inhibitor design and synthesis, enzyme inhibition assays, co-crystallography, and structural analysis. A panel of inhibitors in matched pairs were designed with and without P4 cap fluorination, tested against WT protease and the D168A resistant variant, and a total of 22 high-resolution co-crystal structures were determined. While fluorination did not significantly improve potency against the WT protease, PIs with fluorinated P4 caps retained much better potency against the D168A protease variant. Detailed analysis of the co-crystal structures revealed that PIs with fluorinated P4 caps can sample alternate binding conformations that enable adapting to structural changes induced by the D168A substitution. Our results elucidate molecular mechanisms of fluorine-specific inhibitor interactions that can be leveraged in avoiding drug resistance.

Peptide-antibody Fusions Engineered by Phage Display Exhibit Ultrapotent and Broad Neutralization of SARS-CoV-2 Variants

The COVID-19 pandemic has been exacerbated by the emergence of variants of concern (VoCs). Many VoC mutations are found in the viral spike protein (S-protein), and are thus implicated in host infection and response to therapeutics. Bivalent neutralizing antibodies (nAbs) targeting the S-protein receptor-binding domain (RBD) are promising therapeutics for COVID-19, but are limited due to low potency and vulnerability to RBD mutations found in VoCs. To address these issues, we used naive phage-displayed peptide libraries to isolate and optimize 16-residue peptides that bind to the RBD or the N-terminal domain (NTD) of the S-protein. We fused these peptides to the N-terminus of a moderate affinity nAb to generate tetravalent peptide-IgG fusions, and showed that both classes of peptides were able to improve affinities for the S-protein trimer by >100-fold (apparent KD <1 pM). Critically, cell-based infection assays with a panel of six SARS-CoV-2 variants demonstrate that an RBD-binding peptide was able to enhance the neutralization potency of a high-affinity nAb >100-fold. Moreover, this peptide-IgG was able to neutralize variants that were resistant to the same nAb in the bivalent IgG format. To show that this approach is general, we fused the same peptide to a clinically approved nAb drug, and showed that it rescued neutralization against a resistant variant. Taken together, these results establish minimal peptide fusions as a modular means to greatly enhance affinities, potencies, and breadth of coverage of nAbs as therapeutics for SARS-CoV-2.

Vaccine hesitancy for coronavirus SARS-CoV-2 in North India

With the roll-out of worlds largest vaccine drive for Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) by Government of India on January 16 2021, India has targeted to vaccinate its entire population by the end of year 2021. Struggling with vaccine procurement and production earlier, India came up with these hurdles but the Indian population still did not seem to be mobilizing swiftly towards vaccination centers. With the initial hesitancy, as soon as the vaccination started to speedup, India was hit severely by the second wave. The severe second wave has slowed down the vaccination pace and also it was one of the major contributing factor of vaccine hesitancy. To understand the nature of vaccine hesitancy and factors underlying it, we conducted an extensive online and offline surveys in Varanasi and adjoining regions using structured questions. Majority of respondents though were students (0.633), respondents from other occupations such as government officials (0.10) were also included in the study. We observed several intriguing opinions on our eleven questions. It is interesting to note that the majority of the people (0.75) relied on fake news and did not take COVID-19 seriously. Most importantly, we noticed that a substantial proportion of respondents (relative frequency 0.151; mean age 24.8 years) reported that they are still not interested in vaccination. People who have neither been vaccinated nor have ever been infected may become the medium for spreading the virus and creating new variants. This could also lead to a resistant variant of the vaccine in the future. We expect that this extensive survey may help the government to upgrade their vaccination policies for COVID-19 in North India.

Review of Genetic Variants of Butyrylcholinesterase and Their Potential Impact on Human Health

Butyrylcholinesterase (BChE) is an enzyme found in plasma and many other parts of the body. It is enzyme that hydrolyses drugs containing ester bonds such as drugs acting at the neuromuscular junction (succinylcholine) and local anaesthetics (procaine). Examination of the gene for mutations or polymorphisms causing the observed biochemical phenotypes has isolated those responsible for all the most widely known variants. The molecular bases of several genetic variants of BChE have been reported, such as the Atypical variant, fluoride-resistant variant, silent variant, K variant, J variant and C5 variant. In general, BChE polymorphisms have been shown to produce enzymes with varying levels of catalytic activity. Genetic variants of human butyrylcholinesterase were one of the first examples in the new field of pharmacogenetics when it was recognized that abnormal response to the succinylcholine was due to a mutated enzyme with low binding affinity. Beside that, variant of BChE has potential impact for Alzheimer disease patology.

A spatial vaccination strategy to reduce the risk of vaccine-resistant variants

The process of vaccinating the world population against COVID-19 is expected to take well over a year to complete. As vaccination progresses and population immunity increases, a counteracting relaxation of social distancing measures is observed. The result will be a prolonged period of high disease prevalence combined with a fitness advantage for vaccine-resistant variants, implying a considerably increased probability that a resistant variant will spread in the population. In this paper we propose a spatial vaccination strategy that has the potential to dramatically reduce this risk. Instead of spreading the vaccination effort equally throughout a country, distinct geographic regions of the country are sequentially vaccinated, quickly bringing each to effective herd immunity. Regions with high vaccination rates will then have low infection rates and vice versa. Since people primarily interact with others in their own region, spatial vaccination will reduce the number of encounters between infected people (the source of mutations) and vaccinated people (who facilitate the spread of vaccine-resistant strains). Thus with proper logistic preparations, a spatial vaccination campaign could be highly effective in reducing the global risk of vaccine-resistant variants.

SUMOylation of Arginyl tRNA Synthetase Modulates the Drosophila Innate Immune Response

SUMO conjugation of a substrate protein can modify its activity, localization, interaction or function. A large number of SUMO targets in cells have been identified by Proteomics, but biological roles for SUMO conjugation for most targets remains elusive. The multi-aminoacyl tRNA synthetase complex (MARS) is a sensor and regulator of immune signaling. The proteins of this 1.2 MDa complex are targets of SUMO conjugation, in response to infection. Arginyl tRNA Synthetase (RRS), a member of the sub-complex II of MARS, is one such SUMO conjugation target. The sites for SUMO conjugation are Lys 147 and 383. Replacement of these residues by Arg (RRSK147R,K383R), creates a SUMO conjugation resistant variant (RRSSCR). Transgenic Drosophila lines for RRSWT and RRSSCR were generated by expressing these variants in a RRS loss of function (lof) animal, using the UAS-Gal4 system. The RRS-lof line was itself generated using CRISPR/Cas9 genome editing. Expression of both RRSWT and RRSSCR rescue the RRS-lof lethality. Adult animals expressing RRSWT and RRSSCR are compared and contrasted for their response to bacterial infection by gram positive M. luteus and gram negative Ecc15. We find that RRSSCR, when compared to RRSWT, shows modulation of the transcriptional response, as measured by quantitative 3′ mRNA sequencing. Our study uncovers a possible non-canonical role for SUMOylation of RRS, a member of the MARS complex, in host-defense.

The Role of Akt in Acquired Cetuximab Resistant Head and Neck Squamous Cell Carcinoma: An In Vitro Study on a Novel Combination Strategy

The epidermal growth factor receptor (EGFR) is a therapeutic target in head and neck squamous cell carcinoma (HNSCC). Resistance to EGFR-targeted therapies, such as cetuximab, poses a challenging problem. This study aims to characterize acquired cetuximab resistance mechanisms in HNSCC cell lines by protein phosphorylation profiling. Through this, promising combination treatments can be identified to possibly overcome acquired cetuximab resistance in HNSCC. Protein phosphorylation profiling showed increased phosphorylation of Akt1/2/3 after cetuximab treatment in acquired cetuximab resistant cells compared to cetuximab sensitive cells, which was confirmed by western blotting. Based on this protein phosphorylation profile, a novel combination treatment with cetuximab and the Akt1/2/3 inhibitor MK2206 was designed. Synergy between cetuximab and MK2206 was observed in two cetuximab sensitive HNSCC cell lines and one acquired cetuximab resistant variant in simultaneous treatment schedules. In conclusion, this study demonstrates that increased Akt1/2/3 phosphorylation seems to be characteristic for acquired cetuximab resistance in HNSCC cell lines. Our results also show an additive to synergistic interaction between cetuximab and MK2206 in simultaneous treatment schedules. These data support the hypothesis that the combination of cetuximab with PI3K/Akt pathway inhibition might be a promising novel therapeutic strategy to overcome acquired cetuximab resistance in HNSCC patients.

Ineffective neutralization of the SARS-CoV-2 Mu variant by convalescent and vaccine sera

On August 30, 2021, the WHO classified the SARS-CoV-2 Mu variant (B.1.621 lineage) as a new variant of interest. The WHO defines “comparative assessment of virus characteristics and public health risks” as primary action in response to the emergence of new SARS-CoV-2 variants. Here, we demonstrate that the Mu variant is highly resistant to sera from COVID-19 convalescents and BNT162b2-vaccinated individuals. Direct comparison of different SARS-CoV-2 spike proteins revealed that Mu spike is more resistant to serum-mediated neutralization than all other currently recognized variants of interest (VOI) and concern (VOC). This includes the Beta variant (B.1.351) that has been suggested to represent the most resistant variant to convalescent and vaccinated sera to date (e.g., Collier et al, Nature, 2021; Wang et al, Nature, 2021). Since breakthrough infection by newly emerging variants is a major concern during the current COVID-19 pandemic (Bergwerk et al., NEJM, 2021), we believe that our findings are of significant public health interest. Our results will help to better assess the risk posed by the Mu variant for vaccinated, previously infected and naïve populations.

Some Indicators of Nonspecific Immunity of Various Breeding Groups of Carp in Different Periods of the Annual Cycle

A comparative study of some parameters of nonspecific immunity in the Angelinskii rubella-resistant variant of the scaly and mirror groups of carp in the prespawning and late feeding periods was carried out. The level of the antimicrobial properties of the C-reactive protein, nonspecific immune complexes in the blood serum, and phagocytic activity of neutrophils were studied. The study showed interbreed and inter-seasonal differences in some indicators. It is concluded that the higher level of bacteriostatic activity of blood serum in the rubella-resistant variant, compared with other groups of carp, provides a low percentage of immunodeficient individuals and resistance to pathogens of infectious diseases.

Review of Genetic Variants of Butyrylcholinesterase and Their Potential Impact on Human Health

Butyrylcholinesterase (BChE) is an enzyme found in plasma and many other parts of the body. It is enzyme that hydrolyses drugs containing ester bonds such as drugs acting at the neuromuscular junction (succinylcholine) and local anaesthetics (procaine). Examination of the gene for mutations or polymorphisms causing the observed biochemical phenotypes has isolated those responsible for all the most widely known variants. The molecular bases of several genetic variants of BChE have been reported, such as the Atypical variant, fluoride-resistant variant, silent variant, K variant, J variant and C5 variant. In general, BChE polymorphisms have been shown to produce enzymes with varying levels of catalytic activity. Genetic variants of human butyrylcholinesterase were one of the first examples in the new field of pharmacogenetics when it was recognized that abnormal response to the succinylcholine was due to a mutated enzyme with low binding affinity. Beside that, variant of BChE has potential impact for Alzheimer disease patology.