Sanja Glisic

Characterization of conserved properties of hemagglutinin of H5N1 and human influenza viruses: possible consequences for therapy and infection control

BackgroundEpidemics caused by highly pathogenic avian influenza virus (HPAIV) are a continuing threat to human health and to the worlds economy. The development of approaches, which help to understand the significance of structural changes resulting from the alarming mutational propensity for human-to-human transmission of HPAIV, is of particularly interest. Here we compare informational and structural properties of the hemagglutinin (HA) of H5N1 virus and human influenza virus subtypes, which are important for the receptor/virus interaction.ResultsPresented results revealed that HA proteins encode highly conserved information that differ between influenza virus subtypes H5N1, H1N1, H3N2, H7N7 and defined an HA domain which may modulate interaction with receptor. We also found that about one third of H5N1 viruses which are isolated during the 2006/07 influenza outbreak in Egypt possibly evolve towards receptor usage similar to that of seasonal H1N1.ConclusionThe presented results may help to better understand the interaction of influenza virus with its receptor(s) and to identify new therapeutic targets for drug development.

Angiotensin II type 1 receptor gene polymorphism and essential hypertension in Serbian population

Essential hypertension is considered to be a multifactorial trait resulting from the combined influence of environmental and genetic determinants. Due to the controversial results about the role of the ATR1 gene locus in hypertension and understanding that ethnic origin should be carefully considered in studying the association between gene polymorphism and disease etiology, we investigated the role of A1166C polymorphism in Serbian hypertensives. A total of 298 subjects, 100 hypertensive and 198 normotensive, age- and sex-matched controls, were included in this study. All subjects were genotyped for the A1166C polymorphism in ATR1 gene using allele-specific PCR-based technique. There were significant differences in both allele and genotype frequencies between hypertensive and normotensive male subjects (p<0.05). There is significant association between hypertension and CC genotype (CC vs. AC+AA OR=2.56, p=0.04) in the males only. These results suggest that a genetic variant of the ATR1 gene locus influences the risk of essential hypertension in the sex-specific manner in the Serbian population.

Discovery of New Therapeutic Targets by the Informational Spectrum Method

The field of bioinformatics has become a major part of the drug discovery pipeline playing a key role in improvement and acceleration of this time and money consuming process. Here we review the application of the informational spectrum method (ISM), a virtual spectroscopy method for structure/function analysis of proteins, in identification of functional protein domains representing candidate therapeutic targets for drugs against human immunodeficiency virus (HIV)-1, anthrax, highly pathogenic influenza virus H5N1 and cardiovascular diseases.

Virtual screen for repurposing approved and experimental drugs for candidate inhibitors of EBOLA virus infection

The ongoing Ebola virus epidemic has presented numerous challenges with respect to control and treatment because there are no approved drugs or vaccines for the Ebola virus disease (EVD). Herein is proposed simple theoretical criterion for fast virtual screening of molecular libraries for candidate inhibitors of Ebola virus infection. We performed a repurposing screen of 6438 drugs from DrugBank using this criterion and selected 267 approved and 382 experimental drugs as candidates for treatment of EVD including 15 anti-malarial drugs and 32 antibiotics. An open source Web server allowing screening of molecular libraries for candidate drugs for treatment of EVD was also established.

Study of apoB gene signal peptide insertion/deletion polymorphism in a healthy Serbian population: no association with serum lipid levels

The apolipoprotein B (apoB) signal peptide polymorphism was studied in unrelated healthy individuals. A total of 232 women and 222 men were analyzed separately. The relative frequencies of Del allele in women and men were 0.42 and 0.37, respectively. More heterozygous individuals were detected in comparison with other populations, using a modified silver staining method on polyacrylamide gel for visualization of Ins and Del alleles. There was no statistically significant difference in mean lipid levels adjusted for age, BMI, smoking habit and blood pressure between the three Ins/Del genotypes in both samples (ANOVA). Therefore, no differences were shown in the genotype frequency distribution throughout the lipid quartiles.

Novel Phylogenetic Algorithm to Monitor Human Tropism in Egyptian H5N1-HPAIV Reveals Evolution toward Efficient Human-to-Human Transmission

Years of endemic infections with highly pathogenic avian influenza (HPAI) A subtype H5N1 virus in poultry and high numbers of infections in humans provide ample opportunity in Egypt for H5N1-HPAIV to develop pandemic potential. In an effort to better understand the viral determinants that facilitate human infections of the Egyptian H5N1-HPAIVvirus, we developed a new phylogenetic algorithm based on a new distance measure derived from the informational spectrum method (ISM). This new approach, which describes functional aspects of the evolution of the hemagglutinin subunit 1 (HA1), revealed a growing group G2 of H5N1-HPAIV in Egypt after 2009 that acquired new informational spectrum (IS) properties suggestive of an increased human tropism and pandemic potential. While in 2006 all viruses in Egypt belonged to the G1 group, by 2011 these viruses were virtually replaced by G2 viruses. All of the G2 viruses displayed four characteristic mutations (D43N, S120(D,N), (S,L)129Δ and I151T), three of which were previously reported to increase binding to the human receptor. Already in 2006–2008 G2 viruses were significantly (p<0.02) more often found in humans than expected from their overall prevalence and this further increased in 2009–2011 (p<0.007). Our approach also identified viruses that acquired additional mutations that we predict to further enhance their human tropism. The extensive evolution of Egyptian H5N1-HPAIV towards a preferential human tropism underlines an urgent need to closely monitor these viruses with respect to molecular determinants of virulence.

Influenza vaccine as prevention for cardiovascular diseases: Possible molecular mechanism

Despite plausible evidence for beneficial effects of the vaccination against influenza in cardiovascular diseases (CVD) very limited studies have been carried out to explain the molecular mechanism of this phenomenon. Using the informational spectrum method (ISM), a virtual spectroscopy method for analysis of protein-protein interactions, the bradykinin 2 receptor (BKB2R) was identified as a principal host protein which could mediate molecular processes underlying the cardioprotective effect of influenza vaccines. Based on this finding we suggest that some antibodies elicited by influenza vaccines act as agonists, which activate a BKB2R-associated signaling pathway contributing to the protection against CVD. The ISM analysis of 14 influenza viruses, which were used as components of seasonal vaccines, revealed four vaccine viruses A/Beijing/262/95(H1N1), A/NewCaledonia/20/1999(H1N1), A/Christchurch/28/2003(H3N2) and A/Perth/16/2009(H3N2), which could be suited best for further studies on the cardioprotective effect of influenza vaccines.

Lipoprotein lipase: A bioinformatics criterion for assessment of mutations as a risk factor for cardiovascular disease

Lipoprotein lipase (LPL) is a key enzyme in lipid metabolism. Decrease of the LPL enzymatic activity leads to elevated triglycerides (TG) and reduced high‐density lipoprotein (HDL‐C levels), both risk factors for cardiovascular disease (CVD). Therefore, mutations, which decrease the LPL activity, may confer susceptibility to CVD. Here, the informational spectrum method (ISM), a virtual spectroscopy method for structure/function analysis of nucleotide and protein sequences, is applied for identification of evolutionary highly conserved information encoded by the primary structure of LPL. It was demonstrated that mutations, which alter the LPL enzymatic activity also alter this information. On the basis of this finding, an efficient and simple bioinformatics criterion for assessment of the pathogenic effect of LPL nonsynonymous single nucleotide substitution as a risk factor of CVD has been proposed. Proteins 2008.

Aerobic exercise training as a potential source of natural antibodies protective against human immunodeficiency virus‐1

Despite the effectiveness of HAART in controlling HIV‐1 replication, the emergence of drug‐resistant viruses in infected patients and the severe side effects caused by the currently used drug regimens and the lack of an effective vaccine necessitate the continued search for new therapeutic strategies for prevention and therapy of HIV disease. Previously we reported that natural autoantibodies, recognizing peptide FTDNAKTI (peptide NTM1) derived from the C2 domain of HIV‐1 gp120, contribute to the control of HIV disease. Here we demonstrated that sera from well‐trained athletic (HIV‐negative) subjects showed high reactivity with peptide NTM1. This result confirms that aerobic exercise training stimulates production of natural autoantibodies, which recognize peptide NTM1. Bioinformatics analysis indicates that these natural autoantibodies could slow down disease progression by blocking the superantigenic site on HIV‐1 gp120. The results suggest that aerobic exercise training may be a promising non‐toxic and inexpensive adjunctive anti‐HIV therapy.

Demonstration of a direct interaction between β2-adrenergic receptor and insulin receptor by BRET and bioinformatics.

Glucose metabolism is under the cooperative regulation of both insulin receptor (IR) and β2-adrenergic receptor (β2AR), which represent the receptor tyrosine kinases (RTKs) and seven transmembrane receptors (7TMRs), respectively. Studies demonstrating cross-talk between these two receptors and their endogenous coexpression have suggested their possible interactions. To evaluate the effect of IR and prospective heteromerization on β2AR properties, we showed that IR coexpression had no effect on the ligand binding properties of β2AR; however, IR reduced β2AR surface expression and accelerated its internalization. Additionally, both receptors displayed a similar distribution pattern with a high degree of colocalization. To test the possible direct interaction between β2AR and IR, we employed quantitative BRET2 saturation and competition assays. Saturation assay data suggested constitutive β2AR and IR homo- and heteromerization. Calculated acceptor/donor (AD50) values as a measure of the relative affinity for homo- and heteromer formation differed among the heteromers that could not be explained by a simple dimer model. In heterologous competition assays, a transient increase in the BRET2 signal with a subsequent hyperbolical decrease was observed, suggesting higher-order heteromer formation. To complement the BRET2 data, we employed the informational spectrum method (ISM), a virtual spectroscopy method to investigate protein-protein interactions. Computational peptide scanning of β2AR and IR identified intracellular domains encompassing residues at the end of the 7th TM domain and C-terminal tail of β2AR and a cytoplasmic part of the IR β chain as prospective interaction domains. ISM further suggested a high probability of heteromer formation and homodimers as basic units engaged in heteromerization. In summary, our data suggest direct interaction and higher-order β2AR:IR oligomer formation, likely comprising heteromers of homodimers.