Jia-Tsrong Jan

Glycans on influenza hemagglutinin affect receptor binding and immune response

Recent cases of avian influenza H5N1 and the swine-origin 2009 H1N1 have caused a great concern that a global disaster like the 1918 influenza pandemic may occur again. Viral transmission begins with a critical interaction between hemagglutinin (HA) glycoprotein, which is on the viral coat of influenza, and sialic acid (SA) containing glycans, which are on the host cell surface. To elucidate the role of HA glycosylation in this important interaction, various defined HA glycoforms were prepared, and their binding affinity and specificity were studied by using a synthetic SA microarray. Truncation of the N-glycan structures on HA increased SA binding affinities while decreasing specificity toward disparate SA ligands. The contribution of each monosaccharide and sulfate group within SA ligand structures to HA binding energy was quantitatively dissected. It was found that the sulfate group adds nearly 100-fold (2.04 kcal/mol) in binding energy to fully glycosylated HA, and so does the biantennary glycan to the monoglycosylated HA glycoform. Antibodies raised against HA protein bearing only a single N-linked GlcNAc at each glycosylation site showed better binding affinity and neutralization activity against influenza subtypes than the fully glycosylated HAs elicited. Thus, removal of structurally nonessential glycans on viral surface glycoproteins may be a very effective and general approach for vaccine design against influenza and other human viruses.

A consensus–hemagglutinin-based DNA vaccine that protects mice against divergent H5N1 influenza viruses

H5N1 influenza viruses have spread extensively among wild birds and domestic poultry. Cross-species transmission of these viruses to humans has been documented in over 380 cases, with a mortality rate of ≈60%. There is great concern that a H5N1 virus would acquire the ability to spread efficiently between humans, thereby becoming a pandemic threat. An H5N1 influenza vaccine must, therefore, be an integral part of any pandemic preparedness plan. However, traditional methods of making influenza vaccines have yet to produce a candidate that could induce potently neutralizing antibodies against divergent strains of H5N1 influenza viruses. To address this need, we generated a consensus H5N1 hemagglutinin (HA) sequence based on data available in early 2006. This sequence was then optimized for protein expression before being inserted into a DNA plasmid (pCHA5). Immunizing mice with pCHA5, delivered intramuscularly via electroporation, elicited antibodies that neutralized a panel of virions that have been pseudotyped with the HA from various H5N1 viruses (clades 1, 2.1, 2.2, 2.3.2, and 2.3.4). Moreover, immunization with pCHA5 in mice conferred complete (clades 1 and 2.2) or significant (clade 2.1) protection from H5N1 virus challenges. We conclude that this vaccine, based on a consensus HA, could induce broad protection against divergent H5N1 influenza viruses and thus warrants further study.

Phosphoproteomics of Klebsiella pneumoniae NTUH-K2044 Reveals a Tight Link between Tyrosine Phosphorylation and Virulence

Encapsulated Klebsiella pneumoniae is the predominant causative agent of pyogenic liver abscess, an emerging infectious disease that often complicates metastatic meningitis or endophthalmitis. The capsular polysaccharide on K. pneumoniae surface was determined as the key to virulence. Although the regulation of capsular polysaccharide biosynthesis is largely unclear, it was found that protein-tyrosine kinases and phosphatases are involved. Therefore, the identification and characterization of such kinases, phosphatases, and their substrates would advance our knowledge of the underlying mechanism in capsule formation and could contribute to the development of new therapeutic strategies. Here, we analyzed the phosphoproteome of K. pneumoniae NTUH-K2044 with a shotgun approach and identified 117 unique phosphopeptides along with 93 in vivo phosphorylated sites corresponding to 81 proteins. Interestingly, three of the identified tyrosine phosphorylated proteins, namely protein-tyrosine kinase (Wzc), phosphomannomutase (ManB), and undecaprenyl-phosphate glycosyltransferase (WcaJ), were found to be distributed in the cps locus and thus were speculated to be involved in the converging signal transduction of capsule biosynthesis. Consequently, we decided to focus on the lesser studied ManB and WcaJ for mutation analysis. The capsular polysaccharides of WcaJ mutant (WcaJY5F) were dramatically reduced quantitatively, and the LD50 increased by 200-fold in a mouse peritonitis model compared with the wild-type strain. However, the capsular polysaccharides of ManB mutant (ManBY26F) showed no difference in quantity, and the LD50 increased by merely 6-fold in mice test. Our study provided a clear trend that WcaJ tyrosine phosphorylation can regulate the biosynthesis of capsular polysaccharides and result in the pathogenicity of K. pneumoniae NTUH-K2044.

Differential Receptor Binding Affinities of Influenza Hemagglutinins on Glycan Arrays

A library of 27 sialosides, including seventeen 2,3-linked and ten 2,6-linked glycans, has been prepared to construct a glycan array and used to profile the binding specificity of different influenza hemagglutinins (HA) subtypes, especially from the 2009 swine-originated H1N1 and seasonal influenza viruses. It was found that the HAs from the 2009 H1N1 and the seasonal Brisbane strain share similar binding profiles yet different binding affinities toward various α2,6 sialosides. Analysis of the binding profiles of different HA subtypes indicate that a minimum set of 5 oligosaccharides can be used to differentiate influenza H1, H3, H5, H7, and H9 subtypes. In addition, the glycan array was used to profile the binding pattern of different influenza viruses. It was found that most binding patterns of viruses and HA proteins are similar and that glycosylation at Asn27 is essential for receptor binding.

Vaccination of monoglycosylated hemagglutinin induces cross-strain protection against influenza virus infections

Significance Influenza epidemics continue to be a threat to public health, and the recent human cases of avian viruses of H5N1, H7N9, and H6N1 in Asia raise the possibility of a new disastrous influenza pandemic. Although an effective universal vaccine that can protect from influenza viruses from different subtypes or even both type A and B is still far from reality, our unique findings, showing that monosaccharide glycosylated HA vaccine induces broader protection against different strains, may lead to a better influenza vaccine design that does not require frequent updates and annual immunizations. This strategy may also map out a new direction for development of universal flu vaccines and be applied to vaccine design for other human viruses. The 2009 H1N1 pandemic and recent human cases of H5N1, H7N9, and H6N1 in Asia highlight the need for a universal influenza vaccine that can provide cross-strain or even cross-subtype protection. Here, we show that recombinant monoglycosylated hemagglutinin (HAmg) with an intact protein structure from either seasonal or pandemic H1N1 can be used as a vaccine for cross-strain protection against various H1N1 viruses in circulation from 1933 to 2009 in mice and ferrets. In the HAmg vaccine, highly conserved sequences that were originally covered by glycans in the fully glycosylated HA (HAfg) are exposed and thus, are better engulfed by dendritic cells (DCs), stimulated better DC maturation, and induced more CD8+ memory T cells and IgG-secreting plasma cells. Single B-cell RT-PCR followed by sequence analysis revealed that the HAmg vaccine activated more diverse B-cell repertoires than the HAfg vaccine and produced antibodies with cross-strain binding ability. In summary, the HAmg vaccine elicits cross-strain immune responses that may mitigate the current need for yearly reformulation of strain-specific inactivated vaccines. This strategy may also map a new direction for universal vaccine design.

Inhibition of the severe acute respiratory syndrome 3CL protease by peptidomimetic α,β-unsaturated esters

Abstract The proteolytic processing of polyproteins by the 3CL protease of severe acute respiratory syndrome coronavirus is essential for the viral propagation. A series of tripeptide α,β-unsaturated esters and ketomethylene isosteres, including AG7088, are synthesized and assayed to target the 3CL protease. Though AG7088 is inactive (IC50 >100μM), the ketomethylene isosteres and tripeptide α,β-unsaturated esters containing both P1 and P2 phenylalanine residues show modest inhibitory activity (IC50 =11–39μM). The Phe-Phe dipeptide inhibitors 18a–e are designed on the basis of computer modeling of the enzyme–inhibitor complex. The most potent inhibitor 18c with an inhibition constant of 0.52μM is obtained by condensation of the Phe-Phe dipeptide α,β-unsaturated ester with 4-(dimethylamino)cinnamic acid. The cell-based assays also indicate that 18c is a nontoxic anti-SARS agent with an EC50 value of 0.18μM.

ENHANCED ANTI-INFLUENZA AGENTS CONJUGATED WITH ANTI-INFLAMMATORY ACTIVITY

Influenza therapy with a single targeted compound is often limited in efficacy due to the rapidly developed drug resistance. Moreover, the uncontrolled virus-induced cytokines could cause the high mortality of human infected by H5N1 avian influenza virus. In this study, we explored the novel dual-targeted bifunctional anti-influenza drugs formed by conjugation with anti-inflammatory agents. In particular, the caffeic acid (CA)-bearing zanamivir (ZA) conjugates ZA-7-CA (1) and ZA-7-CA-amide (7) showed simultaneous inhibition of influenza virus neuraminidase and suppression of pro-inflammatory cytokines. These ZA conjugates provided remarkable protection of cells and mice against influenza infections. Intranasal administration of low dosage (<1.2 μmol/kg/day) of ZA conjugates exhibited much greater effect than the combination therapy with ZA and the anti-inflammatory agents in protection of the lethally infected mice by H1N1 or H5N1 influenza viruses.

Identification of phenanthroindolizines and phenanthroquinolizidines as novel potent anti-coronaviral agents for porcine enteropathogenic coronavirus transmissible gastroenteritis virus and human severe acute respiratory syndrome coronavirus

Abstract The discovery and development of new, highly potent anti-coronavirus agents and effective approaches for controlling the potential emergence of epidemic coronaviruses still remains an important mission. Here, we identified tylophorine compounds, including naturally occurring and synthetic phenanthroindolizidines and phenanthroquinolizidines, as potent in vitro inhibitors of enteropathogenic coronavirus transmissible gastroenteritis virus (TGEV). The potent compounds showed 50% maximal effective concentration (EC50) values ranging from 8 to 1468nM as determined by immunofluorescent assay of the expression of TGEV N and S proteins and by real time-quantitative PCR analysis of viral yields. Furthermore, the potent tylophorine compounds exerted profound anti-TGEV replication activity and thereby blocked the TGEV-induced apoptosis and subsequent cytopathic effect in ST cells. Analysis of the structure–activity relations indicated that the most active tylophorine analogues were compounds with a hydroxyl group at the C14 position of the indolizidine moiety or at the C3 position of the phenanthrene moiety and that the quinolizidine counterparts were more potent than indolizidines. In addition, tylophorine compounds strongly reduced cytopathic effect in Vero 76 cells induced by human severe acute respiratory syndrome coronavirus (SARS CoV), with EC50 values ranging from less than 5 to 340nM. Moreover, a pharmacokinetic study demonstrated high and comparable oral bioavailabilities of 7-methoxycryptopleurine (52.7%) and the naturally occurring tylophorine (65.7%) in rats. Thus, our results suggest that tylophorine compounds are novel and potent anti-coronavirus agents that may be developed into therapeutic agents for treating TGEV or SARS CoV infection.

Cross-Reactive Neuraminidase-Inhibiting Antibodies Elicited by Immunization with Recombinant Neuraminidase Proteins of H5N1 and Pandemic H1N1 Influenza A Viruses

ABSTRACT Neuraminidase (NA), an influenza virus envelope glycoprotein, removes sialic acid from receptors for virus release from infected cells. For this study, we used a baculovirus-insect cell expression system to construct and purify recombinant NA (rNA) proteins of H5N1 (A/Vietnam/1203/2004) and pandemic H1N1 (pH1N1) (A/Texas/05/2009) influenza viruses. BALB/c mice immunized with these proteins had high titers of NA-specific IgG and NA-inhibiting (NI) antibodies against H5N1, pH1N1, H3N2, and H7N9 viruses. H5N1 rNA immunization resulted in higher quantities of NA-specific antibody-secreting B cells against H5N1 and heterologous pH1N1 viruses in the spleen. H5N1 rNA and pH1N1 rNA immunizations both provided complete protection against homologous virus challenges, with H5N1 rNA immunization providing better protection against pH1N1 virus challenges. Cross-reactive NI antibodies were further dissected via pH1N1 rNA protein immunizations with I149V (NA with a change of Ile to Val at position 149), N344Y, and I365T/S366N NA mutations. The I365T/S366N mutation of pH1N1 rNA enhanced cross-reactive NI antibodies against H5N1, H3N2, and H7N9 viruses. It is our hope that these findings provide useful information for the development of an NA-based universal influenza vaccine. IMPORTANCE Neuraminidase (NA) is an influenza virus enzymatic protein that cleaves sialic acid linkages on infected cell surfaces, thus facilitating viral release and contributing to viral transmission and mucus infection. In currently available inactivated or live, attenuated influenza vaccines based on the antigenic content of hemagglutinin proteins, vaccine efficacy can be contributed partly through NA-elicited immune responses. We investigated the NA immunity of different recombinant NA (rNA) proteins associated with pH1N1 and H5N1 viruses. Our results indicate that H5N1 rNA immunization induced more potent cross-protective immunity than pH1N1 rNA immunization, and three mutated residues, I149V, I365T, and S366N, near the NA enzyme active site(s) are linked to enhanced cross-reactive NA-inhibiting antibodies against heterologous and heterosubtypic influenza A viruses. These findings provide useful information for the development of an NA-based universal influenza vaccine.

Glycan Masking of Hemagglutinin for Adenovirus Vector and Recombinant Protein Immunizations Elicits Broadly Neutralizing Antibodies against H5N1 Avian Influenza Viruses

The highly pathogenic avian influenza (HPAI) H5N1 virus, a known trigger of diseases in poultry and humans, is perceived as a serious threat to public health. There is a clear need for a broadly protective H5N1 vaccine or vaccines for inducing neutralizing antibodies against multiple clades/subclades. We constructed single, double, and triple mutants of glycan-masked hemagglutiinin (HA) antigens at residues 83, 127 and 138 (i.e., g83, g127, g138, g83+g127, g127+g138, g83+g138 and g83+g127+g138), and then obtained their corresponding HA-expressing adenovirus vectors and recombinant HA proteins using a prime-boost immunization strategy. Our results indicate that the glycan-masked g127+g138 double mutant induced more potent HA-inhibition, virus neutralization antibodies, cross-clade protection against heterologous H5N1 clades, correlated with the enhanced bindings to the receptor binding sites and the highly conserved stem region of HA. The immune refocusing stem-specific antibodies elicited by the glycan-masked H5HA g127+g138 and g83+g127+g138 mutants overlapped with broadly neutralizing epitopes of the CR6261 monoclonal antibody that neutralizes most group 1 subtypes. These findings may provide useful information in the development of a broadly protective H5N1 influenza vaccine.