EV71:TLLcho virus murine model of enterovirus A71 neurological disease does not exhibit neurogenic pulmonary oedema

Small animal models play an important role in investigating and revealing the molecular determinants and mechanisms underlying neuro-virulence of enterovirus A71 (EV-A71). In our previous study, we successfully developed two mouse cell-line replication competent EV-A71 strains (EV71:TLLm and EV71:TLLmv) which were capable of inducing neuro-invasion in BALB/c mice. The more virulent EV71:TLLmv exhibited ability to induce acute encephalomyelitis accompanied by neurogenic pulmonary oedema. EV71:TLLcho virus strain was generated from EV71:TLLm by a series of passages in CHO-K1 cells. EV71:TLLcho demonstrated a broader range of infectivity across various mammalian cell lines and exhibited complete cytopathic effects (CPE) within 48 hours post-inoculation in comparison to EV71:TLLm or EV71:TLLmv. EV71:TLLcho consistently yielded higher levels of viral replication at all time points examined. In comparison to EV71:TLLm, EV71:TLLcho consistently induced more severe disease and increased mortality in one-week old BALB/c mice. However, unlike mice challenged with EV71:TLLmv, none of the mice challenged with EV71:TLLcho progressed to severe acute encephalomyelitis and developed neurogenic pulmonary oedema.

Contact-Free Co-Culture Model for the Study of Innate Immune Cell Activation During Respiratory Virus Infection

The early interactions between the nasal epithelial layer and the innate immune cells during viral infections remains an under-explored area. The significance of innate immunity signaling in viral infections has increased substantially as patients with respiratory infections who exhibit high innate T cell activation show a better disease outcome. Hence, dissecting these early innate immune interactions allows the elucidation of the processes that govern them and may facilitate the development of potential therapeutic targets and strategies for dampening or even preventing early progression of viral infections. This protocol details a versatile model that can be used to study early crosstalk, interactions, and activation of innate immune cells from factors secreted by virally infected airway epithelial cells. Using an H3N2 influenza virus (A/Aichi/2/1968) as the representative virus model, innate cell activation of co-cultured peripheral blood mononuclear cells (PBMCs) has been analyzed using flow cytometry to investigate the subsets of cells that are activated by the soluble factors released from the epithelium in response to the viral infection. The results demonstrate the gating strategy for differentiating the subsets of cells and reveal the clear differences between the activated populations of PBMCs and their crosstalk with the control and infected epithelium. The activated subsets can then be further analyzed to determine their functions as well as molecular changes specific to the cells. Findings from such a crosstalk investigation may uncover factors that are important for the activation of vital innate cell populations, which are beneficial in controlling and suppressing the progression of viral infection. Furthermore, these factors can be universally applied to different viral diseases, especially to newly emerging viruses, to dampen the impact of such viruses when they first circulate in naïve human populations.

Enteroviral 3C protease activates the human NLRP1 inflammasome in airway epithelia

Immune sensor proteins are critical to the function of the human innate immune system. The full repertoire of cognate triggers for human immune sensors is not fully understood. Here, we report that human NACHT, LRR, and PYD domains-containing protein 1 (NLRP1) is activated by 3C proteases (3Cpros) of enteroviruses, such as human rhinovirus (HRV). 3Cpros directly cleave human NLRP1 at a single site between Glu130 and Gly131 This cleavage triggers N-glycine-mediated degradation of the autoinhibitory NLRP1 N-terminal fragment via the cullinZER1/ZYG11B complex, which liberates the activating C-terminal fragment. Infection of primary human airway epithelial cells by live human HRV triggers NLRP1-dependent inflammasome activation and interleukin-18 secretion. Our findings establish 3Cpros as a pathogen-derived trigger for the human NLRP1 inflammasome and suggest that NLRP1 may contribute to inflammatory diseases of the airway.

Monoclonal antibodies for the S2 subunit of spike of SARS-CoV-1 cross-react with the newly-emerged SARS-CoV-2

Background

A novel coronavirus, SARS-CoV-2, which emerged at the end of 2019 and causes COVID-19, has resulted in worldwide human infections. While genetically distinct, SARS-CoV-1, the aetiological agent responsible for an outbreak of severe acute respiratory syndrome (SARS) in 2002–2003, utilises the same host cell receptor as SARS-CoV-2 for entry: angiotensin-converting enzyme 2 (ACE2). Parts of the SARS-CoV-1 spike glycoprotein (S protein), which interacts with ACE2, appear conserved in SARS-CoV-2.

Aim

The cross-reactivity with SARS-CoV-2 of monoclonal antibodies (mAbs) previously generated against the S protein of SARS-CoV-1 was assessed.

Methods

The SARS-CoV-2 S protein sequence was aligned to those of SARS-CoV-1, Middle East respiratory syndrome (MERS) and common-cold coronaviruses. Abilities of mAbs generated against SARS-CoV-1 S protein to bind SARS-CoV-2 or its S protein were tested with SARS-CoV-2 infected cells as well as cells expressing either the full length protein or a fragment of its S2 subunit. Quantitative ELISA was also performed to compare binding of mAbs to recombinant S protein.

Results

An immunogenic domain in the S2 subunit of SARS-CoV-1 S protein is highly conserved in SARS-CoV-2 but not in MERS and human common-cold coronaviruses. Four murine mAbs raised against this immunogenic fragment could recognise SARS-CoV-2 S protein expressed in mammalian cell lines. In particular, mAb 1A9 was demonstrated to detect S protein in SARS-CoV-2-infected cells and is suitable for use in a sandwich ELISA format.

Conclusion

The cross-reactive mAbs may serve as useful tools for SARS-CoV-2 research and for the development of diagnostic assays for COVID-19.

Monoclonal antibodies for the S2 subunit of spike of SARS-CoV-1 cross-react with the newly-emerged SARS-CoV-2

BackgroundA novel coronavirus, SARS-CoV-2, which emerged at the end of 2019 and causes COVID-19, has resulted in worldwide human infections. While genetically distinct, SARS-CoV-1, the aetiological agent responsible for an outbreak of severe acute respiratory syndrome (SARS) in 2002-2003, utilises the same host cell receptor as SARS-CoV-2 for entry: angiotensin-converting enzyme 2 (ACE2). Parts of the SARS-CoV-1 spike glycoprotein (S protein), which interacts with ACE2, appear conserved in SARS-CoV-2.AimThe cross-reactivity with SARS-CoV-2 of monoclonal antibodies (mAbs) previously generated against the S protein of SARS-CoV-1 was assessed.MethodsThe SARS-CoV-2 S protein sequence was aligned to those of SARS-CoV-1, Middle East respiratory syndrome (MERS) and common-cold coronaviruses. Abilities of mAbs generated against SARS-CoV-1 S protein to bind SARS-CoV-2 or its S protein were tested with SARS-CoV-2 infected cells as well as cells expressing either the full length protein or a fragment of its S2 subunit. Quantitative ELISA was also performed to compare binding of mAbs to recombinant S protein.ResultsAn immunogenic domain in the S2 subunit of SARS-CoV-1 S protein is highly conserved in SARS-CoV-2 but not in MERS and human common-cold coronaviruses. Four murine mAbs raised against this immunogenic fragment could recognise SARS-CoV-2 S protein expressed in mammalian cell lines. In particular, mAb 1A9 was demonstrated to detect S protein in SARS-CoV-2-infected cells and is suitable for use in a sandwich ELISA format.ConclusionThe cross-reactive mAbs may serve as useful tools for SARS-CoV-2 research and for the development of diagnostic assays for COVID-19.

Epidemiology and Relative Severity of Influenza Subtypes in Singapore in the Post-Pandemic Period from 2009 to 2010

Background

After 2009, pandemic influenza A(H1N1) [A(H1N1)pdm09] cocirculated with A(H3N2) and B in Singapore.

Methods

A cohort of 760 participants contributed demographic data and up to 4 blood samples each from October 2009 to September 2010. We compared epidemiology of the 3 subtypes and investigated evidence for heterotypic immunity through multivariable logistic regression using a generalized estimating equation. To examine age-related differences in severity between subtypes, we used LOESS (locally weighted smoothing) plots of hospitalization to infection ratios and explored birth cohort effects referencing the pandemic years (1957; 1968).

Results

Having more household members aged 5–19 years and frequent public transport use increased risk of infection, while preexisting antibodies against the same subtype (odds ratio [OR], 0.61; P = .002) and previous influenza infection against heterotypic infections (OR, 0.32; P = .045) were protective. A(H1N1)pdm09 severity peaked in those born around 1957, while A(H3N2) severity was least in the youngest individuals and increased until it surpassed A(H1N1)pdm09 in those born in 1952 or earlier. Further analysis showed that severity of A(H1N1)pdm09 was less than that for A(H3N2) in those born in 1956 or earlier (P = .021) and vice versa for those born in 1968 or later (P < .001), with no difference in those born between 1957 and 1967 (P = .632).

Conclusions

Our findings suggest that childhood exposures had long-term impact on immune responses consistent with the theory of antigenic sin. This, plus observations on short-term cross-protection, have implications for vaccination and influenza epidemic and pandemic mitigation strategies.

Capsules of virulent pneumococcal serotypes enhance formation of neutrophil extracellular traps during in vivo pathogenesis of pneumonia

Neutrophil extracellular traps (NETs) are released by activated neutrophils to ensnare and kill microorganisms. NETs have been implicated in tissue injury since they carry cytotoxic components of the activated neutrophils. We have previously demonstrated the generation of NETs in infected murine lungs during both primary pneumococcal pneumonia and secondary pneumococcal pneumonia after primary influenza. In this study, we assessed the correlation of pneumococcal capsule size with pulmonary NETs formation and disease severity. We compared NETs formation in the lungs of mice infected with three pneumococcal strains of varying virulence namely serotypes 3, 4 and 19F, as well as a capsule-deficient mutant of serotype 4. In primary pneumonia, NETs generation was strongly associated with the pneumococcal capsule thickness, and was proportional to the disease severity. Interestingly, during secondary pneumonia after primary influenza infection, intense pulmonary NETs generation together with elevated myeloperoxidase activity and cytokine dysregulation determined the disease severity. These findings highlight the crucial role played by the size of pneumococcal capsule in determining the extent of innate immune responses such as NETs formation that may contribute to the severity of pneumonia.

Human genome-wide RNAi screen reveals host factors required for enterovirus 71 replication

Enterovirus 71 (EV71) is a neurotropic enterovirus without antivirals or vaccine, and its host-pathogen interactions remain poorly understood. Here we use a human genome-wide RNAi screen to identify 256 host factors involved in EV71 replication in human rhabdomyosarcoma cells. Enrichment analyses reveal overrepresentation in processes like mitotic cell cycle and transcriptional regulation. We have carried out orthogonal experiments to characterize the roles of selected factors involved in cell cycle regulation and endoplasmatic reticulum-associated degradation. We demonstrate nuclear egress of CDK6 in EV71 infected cells, and identify CDK6 and AURKB as resistance factors. NGLY1, which co-localizes with EV71 replication complexes at the endoplasmatic reticulum, supports EV71 replication. We confirm importance of these factors for EV71 replication in a human neuronal cell line and for coxsackievirus A16 infection. A small molecule inhibitor of NGLY1 reduces EV71 replication. This study provides a comprehensive map of EV71 host factors and reveals potential antiviral targets.

Enterovirus 71 (EV71) infection causes a spectrum of symptoms including neurological disease. To improve our understanding of EV71-host interactions, Wu et al. here perform a genome-wide RNAi screen, which implicates cell cycle regulation and ER-associated degradation as important factors in EV71 replication.

Biochemical and structural characterization of the interface mediating interaction between the influenza A virus non-structural protein-1 and a monoclonal antibody

We have previously shown that a non-structural protein 1 (NS1)-binding monoclonal antibody, termed as 2H6, can significantly reduce influenza A virus (IAV) replication when expressed intracellularly. In this study, we further showed that 2H6 binds stronger to the NS1 of H5N1 than A/Puerto Rico/8/1934(H1N1) because of an amino acid difference at residue 48. A crystal structure of 2H6 fragment antigen-binding (Fab) has also been solved and docked onto the NS1 structure to reveal the contacts between specific residues at the interface of antibody-antigen complex. In one of the models, the predicted molecular contacts between residues in NS1 and 2H6-Fab correlate well with biochemical results. Taken together, residues N48 and T49 in H5N1 NS1 act cooperatively to maintain a strong interaction with mAb 2H6 by forming hydrogen bonds with residues found in the heavy chain of the antibody. Interestingly, the pandemic H1N1-2009 and the majority of seasonal H3N2 circulating in humans since 1968 has N48 in NS1, suggesting that mAb 2H6 could bind to most of the currently circulating seasonal influenza A virus strains. Consistent with the involvement of residue T49, which is well-conserved, in RNA binding, mAb 2H6 was also found to inhibit the interaction between NS1 and double-stranded RNA.

A monoclonal antibody binds to threonine 49 in the non-structural 1 protein of influenza A virus and interferes with its ability to modulate viral replication

The emergence of resistant influenza A viruses highlights the continuous requirement of new antiviral drugs that can treat the viral infection. Non-structural 1 (NS1) protein, an indispensable component for efficient virus replication, can be used as a potential target for generating new antiviral agents. Here, we study the interaction of 2H6 monoclonal antibody with NS1 protein and also determine whether influenza virus replication can be inhibited by blocking NS1. The 2H6-antigen binding fragment (Fab) forms a multimeric complex with the NS1 RNA-binding domain (RBD). T49, a residue which forms a direct hydrogen bond with double stranded RNA, in NS1 protein was found to be critical for its interaction with 2H6 antibody. NS1(RBD) has high affinity to 2H6 with KD of 43.5±4.24nM whereas NS1(RBD)-T49A has more than 250 times lower affinity towards 2H6. Interestingly, the intracellular expression of 2H6-single-chain variable fragment (scFv) in mammalian cells caused a reduction in viral growth and the M1 viral protein level was significantly reduced in 2H6-scFv transfected cells in comparison to vector transfected cells at 12h post infection. These results indicate that the tight binding of 2H6 to NS1 could lead to reduction in viral replication and release of progeny virus. In future, 2H6 antibody in combination with other neutralizing antibodies can be used to increase the potency of viral inhibition.

Angiopoietin-like 4 Increases Pulmonary Tissue Leakiness and Damage during Influenza Pneumonia

Excessive host inflammatory responses negatively impact disease outcomes in respiratory infection. Host-pathogen interactions during the infective phase of influenza are well studied, but little is known about the host's response during the repair stage. Here, we show that influenza infection stimulated the expression of angiopoietin-like 4 (ANGPTL4) via a direct IL6-STAT3-mediated mechanism. ANGPTL4 enhanced pulmonary tissue leakiness and exacerbated inflammation-induced lung damage. Treatment of infected mice with neutralizing anti-ANGPTL4 antibodies significantly accelerated lung recovery and improved lung tissue integrity. ANGPTL4-deficient mice also showed reduced lung damage and recovered faster from influenza infection when compared to their wild-type counterparts. Retrospective examination of human lung biopsy specimens from infection-induced pneumonia with tissue damage showed elevated expression of ANGPTL4 when compared to normal lung samples. These observations underscore the important role that ANGPTL4 plays in lung infection and damage and may facilitate future therapeutic strategies for the treatment of influenza pneumonia.

A novel universal neutralizing monoclonal antibody against enterovirus 71 that targets the highly conserved "knob" region of VP3 protein

Hand, foot and mouth disease caused by enterovirus 71(EV71) leads to the majority of neurological complications and death in young children. While putative inactivated vaccines are only now undergoing clinical trials, no specific treatment options exist yet. Ideally, EV71 specific intravenous immunoglobulins could be developed for targeted treatment of severe cases. To date, only a single universally neutralizing monoclonal antibody against a conserved linear epitope of VP1 has been identified. Other enteroviruses have been shown to possess major conformational neutralizing epitopes on both the VP2 and VP3 capsid proteins. Hence, we attempted to isolate such neutralizing antibodies against conformational epitopes for their potential in the treatment of infection as well as differential diagnosis and vaccine optimization. Here we describe a universal neutralizing monoclonal antibody that recognizes a conserved conformational epitope of EV71 which was mapped using escape mutants. Eight escape mutants from different subgenogroups (A, B2, B4, C2, C4) were rescued; they harbored three essential mutations either at amino acid positions 59, 62 or 67 of the VP3 protein which are all situated in the “knob” region. The escape mutant phenotype could be mimicked by incorporating these mutations into reverse genetically engineered viruses showing that P59L, A62D, A62P and E67D abolish both monoclonal antibody binding and neutralization activity. This is the first conformational neutralization epitope mapped on VP3 for EV71.

Over the last decade, EV71 has emerged as a major cause of severe hand, foot and mouth disease in the Asia-Pacific region, occasionally leading to fatal brain stem encephalitis in young children. The rapid progression and high mortality of severe EV71 infection makes it vital to identify neutralization epitopes and putative therapeutic monoclonal antibodies. In this study we mapped the first conformational neutralization epitope on the VP3 protein of EV71. This epitope was confirmed by introducing the mutations into reverse genetically engineered viruses which abolished neutralization with monoclonal antibody (mAb)10D3. The importance of this novel neutralization epitope lies in the optimization of putative EV71 vaccines because the VP3 knob could be incorporated together with VP1 into a bivalent subunit vaccine. Further, the universal recognition of a conserved site on EV71 VP3 and not CVA16 makes mAb 10D3 a valuable tool for differential diagnosis of hand, foot and mouth disease. An additional hope is that mAb 10D3 could be used as a therapeutic intravenous immunoglobulin (IVIG).

Snake venom phospholipases A(2): a novel tool against bacterial diseases

The majority of snake venom phospholipases A(2) (svPLA(2)s) are toxic and induce a wide spectrum of biological effects. They are cysteine-rich proteins that contain 119-134 amino acids and share similar structures and functions. About 50% of the residues are incorporated into α-helices, whereas only 10% are in β-sheets. Fourteen conserved cysteines form a network of seven disulfide bridges that stabilize the tertiary structure. They show a high degree of sequence and structural similarity, and are believed to have a common calcium- dependent catalytic mechanism. Additionally, svPLA(2)s display an array of biological actions that are either dependent or independent of catalysis. The PLA(2)s of mammalian origin also exert potent bactericidal activity by binding to anionic surfaces and enzymatic degradation of phospholipids in the target membranes, preferentially of Gram-positive species. The bactericidal activity against Gram-negatives by svPLA(2) requires a synergistic action with bactericidal/permeability-increasing protein (BPI), but is equally dependent on enzymatic- based membrane degradation. Several hypotheses account for the bactericidal properties of svPLA(2)s, which include "fatal depolarization" of the bacterial membrane, creation of physical holes in the membrane, scrambling of normal distribution of lipids between the bilayer leaflets, and damage of critical intracellular targets after internalization of the peptide. The present review discusses several svPLA(2)s and derived peptides that exhibit strong bactericidal activity. The reports demonstrate that svPLA(2)-derived peptides have the potential to counteract microbial infections. In fact, the C-terminal cationic/hydrophobic segment (residues 115-129) of svPLA(2)s is bactericidal. Thus identification of the bactericidal sites in svPLA(2)s has potential for developing novel antimicrobials.

Characterization and specificity of the linear epitope of the enterovirus 71 VP2 protein

Background

Enterovirus 71 (EV71) has emerged as a major causative agent of hand, foot and mouth disease in the Asia-Pacific region over the last decade. Hand, foot and mouth disease can be caused by different etiological agents from the enterovirus family, mainly EV71 and coxsackieviruses, which are genetically closely related. Nevertheless, infection with EV71 may occasionally lead to high fever, neurologic complications and the emergence of a rapidly fatal syndrome of pulmonary edema associated with brainstem encephalitis. The rapid progression and high mortality of severe EV71 infection has highlighted the need for EV71-specific diagnostic and therapeutic tools. Monoclonal antibodies are urgently needed to specifically detect EV71 antigens from patient specimens early in the infection process. Furthermore, the elucidation of viral epitopes will contribute to the development of targeted therapeutics and vaccines.

Results

We have identified the monoclonal antibody 7C7 from a screen of hybridoma cells derived from mice immunized with the EV71-B5 strain. The linear epitope of 7C7 was mapped to amino acids 142-146 (EDSHP) of the VP2 capsid protein and was characterized in detail. Mutational analysis of the epitope showed that the aspartic acid to asparagine mutation of the EV71 subgenogroup A (BrCr strain) did not interfere with antibody recognition. In contrast, the serine to threonine mutation at position 144 of VP2, present in recently emerged EV71-C4 China strains, abolished antigenicity. Mice injected with this virus strain did not produce any antibodies against the VP2 protein. Immunofluorescence and Western blotting confirmed that 7C7 specifically recognized EV71 subgenogroups and did not cross-react to Coxsackieviruses 4, 6, 10, and 16. 7C7 was successfully used as a detection antibody in an antigen-capture ELISA assay.

Conclusions

Detailed mapping showed that the VP2 protein of Enterovirus 71 contains a single, linear, non-neutralizing epitope, spanning amino acids 142-146 which are located in the VP2 protein's E-F loop. The S/T(144) mutation in this epitope confers a loss of VP2 antigenicity to some newly emerged EV71-C4 strains from China. The corresponding monoclonal antibody 7C7 was used successfully in an AC-ELISA and did not cross-react to coxsackieviruses 4, 6, 10, and 16 in immunofluorescence assay and Western blots. 7C7 is the first monoclonal antibody described, that can differentiate Coxsackievirus 16 from Enterovirus 71.

PCR detection and typing of human papilloma virus DNA in squamous carcinoma of the cervix in a cohort of Sri Lankan women

OBJECTIVE

To determine the prevalence of human papilloma virus (HPV) types 16 and 18 in squamous carcinomas of the cervix in Sri Lanka.

DESIGN

Case control study.

SETTING

One gynaecological unit at the Cancer Institute, Maharagama, Sri Lanka.

PATIENTS

15 patients with squamous carcinoma of the cervix, and 15 age matched controls with histologically normal cervices.

MEASUREMENTS

DNA was extracted from paraffin embedded cervical biopsies. Polymerase chain reaction was performed on extracted DNA employing primers specific for HPV types 16 and 18.

RESULTS

HPV 16 DNA was detected in 11 out of 15 cervical cancer biopsies (73.3%), in comparison with 3 out of 15 normal controls (20%). HPV 18 was detected in 3 out of 15 cervical cancer biopsies, but not in a single control biopsy.

CONCLUSION

Despite the limited number of cases in this cohort, this study supports the strong association between HPV 16 and squamous cancer of the cervix.

Rapid detection of enterovirus 71 by real-time TaqMan RT-PCR

BACKGROUND

Enterovirus 71 (EV71) is the main etiological agent of Hand, Foot and Mouth Disease (HFMD) and has been associated with neurological complications which resulted in fatalities during recent outbreaks in Asia Pacific region.

OBJECTIVE

Develop a real-time TaqMan RT-PCR for rapid detection of EV71.

STUDY DESIGN

Specific primers and probe were designed based on highly conserved VP1 region of EV71. The sensitivity of the real-time RT-PCR was evaluated with 67 clinical specimens collected from pediatric patients with suspected HFMD.

RESULTS

Our real-time TaqMan RT-PCR showed 100% specificity in detecting EV71 and showed an analytical sensitivity of 5 viral copies. High sensitivity was also achieved in detecting EV71 directly from clinical specimens.

CONCLUSIONS

Real-time TaqMan RT-PCR offers a rapid and sensitive method to detect EV71 from clinical specimens, and will allow quarantine measures to be taken more effectively during outbreaks.

Identification of immunodominant VP1 linear epitope of enterovirus 71 (EV71) using synthetic peptides for detecting human anti-EV71 IgG antibodies in Western blots

A major IgG-specific immunodominant VP1 linear epitope of enterovirus 71 (EV71) strain 41 (5865/SIN/00009), defined by the core sequence LEGTTNPNG, was identified by Pepscan analysis. Oligonucleotides corresponding to the amino-acid sequence of synthetic peptide SP32 were cloned and over-expressed in Escherichia coli as a recombinant glutathione-S-transferase (GST)-SP32 fusion protein. In ELISAs, this protein did not react with human anti-EV71 IgG antibodies, but there was significant immunoreactivity according to western blot analysis. The amino-acid sequence of SP32 was highly specific for detecting EV71 strains in western blot analysis, and showed no immunoreactivity with monoclonal antibodies raised against other enteroviruses, e.g., CA9 and Echo 6.

Inhibition of enterovirus 71 in virus-infected mice by RNA interference

Enterovirus 71 (EV71) is the main causative agent of hand, foot, and mouth disease (HFMD) in young children. It is often associated with neurological complications and has caused high mortality levels in recent outbreaks in the Asia Pacific region. Currently, there is no effective antiviral therapy against EV71 infections. In this study, we have evaluated and compared the efficacies of three different forms of small interfering RNAs (siRNAs) in inhibiting EV71 replication in a murine model. We have shown that both synthetic 19-mer siRNAs and plasmid-borne short hairpin RNAs (shRNAs) targeted at the conserved 3D(pol) region were able to inhibit EV71 infections in suckling mice when delivered with or without lipid carrier via the systemic route. The treated mice did not exhibit hind limb paralysis and weight loss, as was observed in untreated mice. EV71 replication was significantly reduced as revealed by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blot. In addition, no evidence of interferon (IFN) induction was detected in the intestinal tissues harvested from the mice as a result of siRNA administration. However, the chemically synthesized 29-mer shRNA did not protect the suckling mice from EV71 infections despite being more potent in the in vitro system. Our results indicate that RNA interference (RNAi) may be a promising therapeutic approach for fighting EV71 infections.

Passive protection against lethal enterovirus 71 infection in newborn mice by neutralizing antibodies elicited by a synthetic peptide

Enterovirus 71 (EV71) infections could lead to high mortalities and neither vaccine nor therapeutic treatment is available. We investigated vaccination with a synthetic peptide SP70 representing a neutralizing linear VP1 epitope of EV71 strain 41 (subgenogroup B4) and passive transfer of anti-SP70 antibodies to protect suckling Balb/c mice against EV71 infectivity. When the mouse anti-SP70 antisera with a neutralizing antibody titer of 1:32 were passively administered to one-day-old suckling mice which had been challenged with a lethal dose of 1000 TCID(50) per mouse, the neutralizing anti-SP70 antibodies were able to confer 80% in vivo protection. In contrast, suckling mice which did not receive any anti-SP70 antisera did not survive the viral challenge at day 21 postinfection. Histological examination and real-time RT-PCR assays revealed viral infiltration in small intestines of EV71-infected mice. Interestingly, anti-SP70 antibodies play a major role in the inhibition of EV71 replication in vivo and significantly reduced the viral titer. In conclusion, EV71-neutralizing antibodies elicited by the synthetic peptide SP70 were able to confer good in vivo passive protection against homologous and heterologous EV71 strains in suckling Balb/c mice.

Identification of human metapneumovirus and Chlamydophila pneumoniae in children with asthma and wheeze in Singapore

INTRODUCTION

The aim of our study was to determine if human metapneumovirus (hMPV) and Chlamydophila pneumoniae (CP) could be detected in Singaporean asthmatic children and wheezing infants during an acute asthma attack.

METHODS

The study was performed on 30 older children (mean age 9.8 years) and 30 young children (mean age 1.3 years), who were admitted with an acute exacerbation of wheezing. Nasopharyngeal aspirates were collected and tested by polymerase chain reaction for CP, and for a panel of viruses (hMPV, respiratory syncytial virus, adenovirus, influenza virus types A and B, parainfluenza virus types 1 and 3, and rhinovirus).

RESULTS

hMPV was isolated in eight out of 60 children (13.3 percent), while CP was isolated in two cases. Overall, 48/60 (80 percent) samples were positive for the presence of viruses.

CONCLUSION

In most of the children admitted because of acute wheezing, a virus could be detected. hMPV was isolated for the first time in Singapore in children who were admitted with an acute asthma attack.

Enhanced potency and efficacy of 29-mer shRNAs in inhibition of Enterovirus 71

Enterovirus 71 (EV71) is the main causative agent of hand, foot, and mouth disease (HFMD) in young children. It has been associated with severe neurological complications and has caused significant mortalities in large-scale outbreaks in Asia. In this study, we demonstrated an enhanced silencing of EV71 through the use of chemically synthesized 29-mer shRNAs. The 29-mer shRNAs were designed to target three highly conserved regions of EV71 genome. Transfection of rhabdomyosarcoma (RD) cells with the 29-mer shRNAs significantly inhibited EV71 replication in a dose-dependent manner as demonstrated by reduction of viral RNA, VP1 protein and plaque forming units. The inhibitory effects were more potent and were achieved at 10-fold lower concentrations when compared to 19-mer siRNAs reported previously [Sim, A.C.N., Luhur, A., Tan, T.M.C., Chow, V.T.K., Poh, C.L., 2005. RNA interference against Enterovirus 71 infection. Virology 341, 72-79]. The viral inhibitory effects lasted 72 h post-infection and there was no adverse off-target silencing effect. Gene silencing by 29-mer shRNAs targeted at the 3D(pol) region (sh-3D) was the most effective, achieving 91% viral inhibition. Further evaluation found that no enhanced inhibitory effects were observed when sh-3D was cotransfected with each of the other two candidates. This study showed an improvement in triggering RNAi using the more potent 29-mer shRNAs, indicating its therapeutic potential against EV71.

Identification of neutralizing linear epitopes from the VP1 capsid protein of Enterovirus 71 using synthetic peptides

Enterovirus 71 (EV71) is the main causative agent of Hand, foot and mouth disease (HFMD) and has been associated with severe neurological diseases resulting in high mortalities. Currently, there is no vaccine available and treatment is limited to palliative care. In this study, antisera were raised in mice against 95 overlapping synthetic peptides spanning the VP1 capsid protein of EV71. Two peptides, SP55 and SP70, containing amino acid 163-177 and 208-222 of VP1, respectively, are capable of eliciting neutralizing antibodies against EV71 in the in vitro microneutralization assay. SP70 was identified to be particularly potent in eliciting a neutralizing antibody titer comparable to that obtained with a whole virion-immune serum. Immunization of mice with either SP55 or SP70 triggered an EV71-specific IgG response as high as that obtained with the whole virion as immunogen. The IgG sub-typing revealed that the neutralizing antibodies elicited by both synthetic peptides are likely belonging to the IgG1 sub-type. Alignment with databases showed that the amino acid residues of SP70 are highly conserved amongst the VP1 sequences of EV71 strains from various sub-genogroups. Altogether, these data indicate that SP70 represents a promising candidate for an effective synthetic peptide-based vaccine against EV71.

Specific detection of enterovirus 71 directly from clinical specimens using real-time RT-PCR hybridization probe assay

Enterovirus 71 (EV71) is one of the main causative agents of hand, foot and mouth disease (HFMD) in young children. Infections caused by EV71 could lead to many complications, ranging from brainstem encephalitis to pulmonary oedema, resulting in high mortality. Thus, rapid detection of the virus is required to enable measures to be implemented in preventing widespread transmission. Based on primers and probes targeting at the VP1 region, a real-time reverse-transcriptase polymerase chain reaction (RT-PCR) hybridization probe assay was developed for specific detection of EV71 from clinical specimens. Quantitative analysis showed that the assay was able to detect as low as 5 EV71 viral copies and EV71 was detected from 46 of the 55 clinical specimens obtained from pediatric patients suffering from HFMD during the period from 2000 to 2003 in Singapore. This study showed that the single tube real-time RT-PCR assay developed in this study can be applied as a rapid and sensitive method for specific detection of EV71 directly from clinical specimens.

RNA interference against enterovirus 71 infection

Enterovirus 71 (EV71) is a highly infectious major causative agent of hand, foot, and mouth disease (HFMD) which could lead to severe neurological complications. There is currently no effective therapy against EV71. In this study, RNA interference (RNAi) is employed as a therapeutic approach for specific viral inhibition. Various regions of the EV71 genome were targeted for inhibition by chemically synthesized siRNAs. Transfection of rhabdomyosarcoma (RD) cells with siRNA targeting the 3'UTR, 2C, 3C, or 3D region significantly alleviated cytopathic effects of EV71. The inhibitory effect was dosage-dependent with a corresponding decrease in viral RNA, viral proteins, and plaque formations by EV71. Viral inhibition of siRNA transfected RD cells was still evident after 48 h. In addition, no significant adverse off-target silencing effects were observed. These results demonstrated the potential and feasibility for the use of siRNA as an antiviral therapy for EV71 infections.

Intron position conservation across eukaryotic lineages in tubulin genes

A compilation of intron positions obtained from a large number of eukaryotic genomes across orthologous tubulins is explored for molecular evolution. Comparison of intron positions for 41 alpha, 80 beta, and 30 gamma tubulin genomic sequences indicates that the putative ancestral tubulin gene contained at least 19, 33, and 52 intron positions distributed at different sites in the coding regions for alpha, beta, and gamma tubulins, respectively. Many intron positions are old and are conserved across different eukaryotic lineages and intron distribution patterns are consistent with 'introns-early' hypothesis.

Human genome -- from pieces to patterns

A profile of exon-intron lengths in genes shows a normal distribution. This observation suggests that different genes may have portions of their total exon and/or intron lengths in common. In order to explore the common exon-intron structural patterns that may arise due to common lengths across genes, we compared the exon-intron length patterns of annotated human genes. We discovered 1762278 conserved arrangements of exon-intron length across the otherwise unrelated and diverse genomic landscape. The existence of common exon-intron length patterns across unrelated genes suggests for their role of in gene assemblage and human genome design and architecture.

The NUS MBBS-PhD programme: nurturing clinician-scientists for tomorrow

The MBBS-PhD programme is a significant milestone in medical education in Singapore. In July 2000, the Faculty of Medicine, National University of Singapore launched this programme in collaboration with the Institute of Molecular and Cell Biology, with support from the Economic Development Board, and the Agency for Science, Technology and Research, Singapore. The objectives of the programme are to nurture and develop the talents of the brightest medical students by integrating clinical and basic biomedical research training, as well as to stimulate advanced basic and applied research in areas of growing importance to clinical medicine. The programme also aims to train clinician-scientists who will interface basic biology and clinical practice to solve biomedical problems and spearhead biomedical research initiatives in Singapore. Successful MBBS-PhD graduates can pursue career tracks in clinical research, basic biomedical research or in the biotechnology industry.

The evolution of teaching and learning medical microbiology and infectious diseases at NUS

Infectious diseases were rife during the early years of the Singapore Medical College, which was established in 1905. The current Department of Microbiology in the National University of Singapore (NUS) has its historical roots in the Departments of Bacteriology and Parasitology, which were established in 1925 and 1950 respectively. With the achievements since its inception, and with its present research focus on Infectious Diseases, Immunology, Applied and Environmental Microbiology, it is poised to face the microbiological challenges of the 21st century. Over the decades, the structure of the medical microbiology course in NUS has modernised, culminating in the current emphasis on its practical utility in clinical practice. Coordinated by the Department of Microbiology, the Microbiology and Infectious Diseases module and the Immunology module both adopt integrated multidisciplinary approaches that aim to introduce students to the language and fundamental concepts in microbiology, infectious diseases and immunology.

A report on single exon genes (SEG) in eukaryotes

Single exon genes (SEG) are archetypical of prokaryotes. Hence, their presence in intron-rich, multi-cellular eukaryotic genomes is perplexing. Consequently, a study on SEG origin and evolution is important. Towards this goal, we took the first initiative of identifying and counting SEG in nine completely sequenced eukaryotic organisms--four of which are unicellular (E. cuniculi, S. cerevisiae, S. pombe, P. falciparum) and five of which are multi-cellular (C. elegans, A. thaliana, D. melanogaster, M. musculus, H. sapiens). This exercise enabled us to compare their proportion in unicellular and multi-cellular genomes. The comparison suggests that the SEG fraction decreases with gene count (r = -0.80) and increases with gene density (r = 0.88) in these genomes. We also examined the distribution patterns of their protein lengths in different genomes.

The novel human MOST-1 (C8orf17) gene exhibits tissue specific expression, maps to chromosome 8q24.2, and is overexpressed/amplified in high grade cancers of the breast and prostate

AIMS

To elucidate genes that participate in the process of oncogenesis, primers based on the E6 genes of genital human papillomaviruses (HPVs) were used to amplify potential expressed sequence tags (ESTs) from the MOLT-4 T lymphoblastic leukaemia cell line.

METHODS

Using the polymerase chain reaction (PCR) with human papillomavirus E6 gene primers, an EST from the MOLT-4 T lymphoblastic leukaemia cell line was amplified. Via rapid amplification of cDNA ends (RACE) and cycle sequencing from MOLT-4 and fetal lung cDNA libraries, overlapping cDNAs of 2786 bp and 2054 bp of the corresponding novel human intronless gene designated MOST-1 (for MOLT-4 sequence tag-1) were characterised and assigned the symbol C8orf17 by the HUGO Nomenclature Committee.

RESULTS

Both cDNAs contained a potential open reading frame (ORF) of 297 bp incorporating a methionine codon with an ideal Kozak consensus sequence for translation initiation, and encoding a putative hydrophilic polypeptide of 99 amino acids. Although reverse transcription PCR (RT-PCR) demonstrated MOST-1 expression in all 19 cancer and two normal cell lines tested, differential expression was seen in only nine of 16 normal tissues tested (heart, kidney, liver, pancreas, small intestine, ovary, testis, prostate, and thymus). A 388 bp fragment was amplified from the NS-1 mouse myeloma cell line, the sequence of which was identical to that within the MOST-1 ORF. The MOST-1 gene was mapped by fluorescent in situ hybridisation to chromosome 8q24.2, a region amplified in many breast cancers and prostate cancers, which is also the candidate site of potential oncogene(s) other than c-myc located at 8q24.1. Analysis of paired biopsies of invasive ductal breast cancer and adjacent normal tissue by semiquantitative and real time RT-PCR revealed average tumour to normal ratios of MOST-1 expression that were two times greater in grade 3 cancers than in grade 1 and 2 cancers. Quantitative real time PCR of archival prostatic biopsies displayed MOST-1 DNA values that were 9.9, 7.5, 4.2, and 1.4 times higher in high grade carcinomas, intermediate grade carcinomas, low grade carcinomas, and benign hyperplasias, respectively, than in normal samples.

CONCLUSIONS

These data suggest a role for MOST-1 in cellular differentiation, proliferation, and carcinogenesis.

Complete sequence analyses of enterovirus 71 strains from fatal and non-fatal cases of the hand, foot and mouth disease outbreak in Singapore (2000)

Enterovirus 71 (EV71) is a major aetiological agent of hand, foot and mouth disease (HFMD). In recent years, several outbreaks in East Asia were associated with neurological complications and numerous deaths. An outbreak in Singapore in October 2000 afflicted thousands of children, resulting in four fatal cases from three of whom EV71 was isolated. The genomes of two representative EV71 strains isolated from a fatal case and a surviving patient were completely sequenced, and their nucleotide and amino acid sequences compared with known EV71 strains. The two outbreak strains were classified under genogroup B, together with those previously isolated in Singapore, Malaysia and Japan. Comparative sequence analysis of the two Singapore strains revealed 99% nucleotide similarity, while their deduced amino acid sequences were almost identical except for residue 1506 in the 3A non-structural region. Given that the outbreak involved closely related genetic variants of EV71, the broad spectrum of disease severity may be attributed to critical factors such as varying viral inoculation doses or differing host immune responses following infection, but is less likely to be due to the emergence of EV71 strains with heightened virulence.

Sequence and phylogenetic analysis of SH, G, and F genes and proteins of Human respiratory syncytial virus isolates from Singapore

To study the genetic variability and molecular epidemiology of Human respiratory syncytial virus (HRSV) occurring in Singapore, nucleotide sequencing of three membrane-associated genes (SH, G and F) of four local isolates was performed. Comparison of their nucleotide and amino acid sequences with those of the prototype strains A2 (subgroup A) and CH-18537 (subgroup B) indicated that the Singapore isolates belong to the subgroup A. Comparison of the Singapore isolates with the reference strain A2 showed that whereas the G protein was the most divergent with up to 15% difference, the F and SH proteins showed less diversity of only up to 4%. Each gene exhibited its distinct variable and conserved regions. The N- and O-glycosylation sites within the G protein of the isolates were analyzed to ascertain their potential implications on the antigenicity of the viral glycoprotein. Based on the second variable region of the G protein, phylogenetic analysis of the Singapore isolates with 91 previously identified genotypes of subgroup A revealed that more than one genotype (GA2 and GA5) may circulate in the local population at a given time. This epidemiological study reflects the pattern of genetic relationships between the HRSV isolates from Singapore to those from other parts of the world.