Wolfgang Preiser

Close relative of human Middle East respiratory syndrome coronavirus in bat, South Africa.

To the Editor: The severe acute respiratory syndrome (SARS) outbreak of 2002–03 and the subsequent implication of bats as reservoir hosts of the causative agent, a coronavirus (CoV), prompted numerous studies of bats and the viruses they harbor. A novel clade 2c betacoronavirus, termed Middle East respiratory syndrome (MERS)–CoV, was recently identified as the causative agent of a severe respiratory disease that is mainly affecting humans on the Arabian Peninsula (1). Extending on previous work (2), we described European Pipistrellus bat–derived CoVs that are closely related to MERS-CoV (3). We now report the identification of a South Africa bat derived CoV that has an even closer phylogenetic relationship with MERS-CoV. n nDuring 2011–2012, fecal pellets were collected from 62 bats representing 13 different species in the KwaZulu-Natal and Western Cape Provinces of South Africa and stored in RNAlater solution (Life Technologies, Carlsbad, CA, USA). Details about the bat sample are available in the Technical Appendix. RNA was extracted by using the QIAamp Viral RNA Mini Kit (QIAGEN, Hilden, Germany). Screening for CoVs was done by nested reverse transcription PCR using broadly reactive oligonucleotide primers targeting a conserved region in the RNA-dependent RNA polymerase (RdRp) gene (online Technical Appendix). PCR results were positive for 5 (8%) of the 62 specimens. PCR amplicons for 4 positive specimens yielded alphacoronavirus sequences related to recently described bat alphacoronaviruses from South Africa (4). The other positive specimen, termed PML/2011, was from an adult female Neoromicia cf. zuluensis bat sampled in 2011; the specimen yielded a novel betacoronavirus (GenBank accession no. {type:entrez-nucleotide,attrs:{text:KC869678,term_id:666386896}}KC869678). Technical Appendix Figure 1 shows the distribution of this bat species. n nTo obtain better phylogenetic resolution, we extended the 398-nt RdRp fragment generated by the screening PCR to 816 nt, as described (5). PML/2011 differed from MERS-CoV by only 1 aa exchange (0.3%) in the translated 816-nt RdRp gene fragment. Thus, PML/2011 was much more related to MERS-CoV than any other known virus. The amino acid sequence of the next closest known relatives of MERS-CoV, from European Pipistrellus bats (3), differed from MERS-CoV by 1.8%. The amino acid sequences of viruses from Nycteris bats in Ghana (3) and the 2c prototype bat CoVs, HKU4 and HKU5, from China (6) differed by 5.5%–7.7% from MERS-CoV. The smaller 152- to 396-nt RdRp fragments of 2c bat CoVs from a Hypsugo savii bat in Spain (7), bat guano in Thailand (8), and a Nyctinomops bat in Mexico (9) showed no or only partial overlap with the 816-nt fragment generated in this study; thus, a direct comparison could not be done. However, in their respective RdRp fragments, these CoVs yielded amino acid sequence distances of 3.5%–8.0% and were thus probably more distant from MERS-CoV than the virus described here. n nA Bayesian phylogenetic analysis of the 816-nt RdRp sequence confirmed the close relationship between PML/2011 and MERS-CoV (Figure). Their phylogenetic relatedness was as close as that of SARS-CoV and the most closely related bat coronavirus known, Rs672 from a Rhinolophus sinicus bat (Figure). Like PML/2011 and MERS-CoV, Rs672 and SARS-CoV showed only 1 aa exchange in the translated 816-nt RdRp fragment. To confirm this relatedness, we amplified and sequenced a short 269-nt sequence encompassing the 3′-terminus of the spike gene for PML/2011 (oligonucleotide primers available upon request from the authors). A partial spike gene–based phylogeny using this sequence yielded the same topology as that using the partial RdRp sequence (Technical Appendix Figure 2). Again, PML/2011 was most closely related to MERS-CoV, showing only a 10.9% aa sequence distance in this gene, which encodes the glycoprotein responsible for CoV attachment and cellular entry. This distance was less than the 13.3% aa sequence distance between MERS-CoV and the European Pipistrellus CoVs (3) and less than the 20.5%–27.3% aa sequence distance between MERS-CoV and HKU5 and between MERS-CoV and HKU4 (6) in the same sequence fragment. n n n nFigure n nPartial RNA-dependent RNA polymerase (RdRp) gene phylogeny, including the novel betacoronavirus from a Neoromicia zuluensis bat in South Africa (GenBank accession no. {type:entrez-nucleotide,attrs:{text:KC869678,term_id:666386896}}KC869678 ... n n n nOur results further support the hypothesis that, like human CoV-229E and SARS-CoV, ancestors of MERS-CoV might exist in Old World insectivorous bats belonging to the family Vespertilionidae, to which the genera Neoromicia and Pipistrellus belong (3). Knowledge of the close relatedness of PML/2011 and MERS-CoV, which contrasts with the more distant relatedness of CoVs in bats from the Americas and Asia, enables speculations of an African origin for bat reservoir hosts of MERS-CoV ancestors. This hypothesis is limited by a global sampling bias, the small sample size, and the single clade 2c betacoronavirus detection in this study. Still, a putative transfer of MERS-CoV ancestors from Africa to the Arabian Peninsula would parallel the transfer of other viruses (e.g., the exportation of Rift Valley fever virus from East Africa, which led to a severe outbreak in Saudi Arabia in 2000) (10). n nStudies of Vespertilionidae bats and potential intermediate hosts (e.g., carnivores and ungulates, such as camels) are urgently needed to elucidate the emergence of MERS-CoV. Such studies should focus on the Arabian Peninsula and Africa. n nTechnical Appendix: nDescription of bat sampling, screened bat species, distribution of Neoromicia zuluensis bats, and spike gene phylogeny of the 2c betacoronavirus clade. n nClick here to view.(326K, pdf)

Human monoclonal antibody as prophylaxis for SARS coronavirus infection in ferrets.

n Summaryn n SARS coronavirus continues to cause sporadic cases of severe acute respiratory syndrome (SARS) in China. No active or passive immunoprophylaxis for disease induced by SARS coronavirus is available. We investigated prophylaxis of SARS coronavirus infection with a neutralising human monoclonal antibody in ferrets, which can be readily infected with the virus. Prophylactic administration of the monoclonal antibody at 10 mg/kg reduced replication of SARS coronavirus in the lungs of infected ferrets by 3·3 logs (95% Cl 2·6–4·0 logs; p<0·001), completely prevented the development of SARS coronavirus-induced macroscopic lung pathology (p=0·013), and abolished shedding of virus in pharyngeal secretions. The data generated in this animal model show that administration of a human monoclonal antibody might offer a feasible and effective prophylaxis for the control of human SARS coronavirus infection.n n

Isolation and Characterization of Human Monoclonal Antibodies from Individuals Infected with West Nile Virus

ABSTRACT Monoclonal antibodies (MAbs) neutralizing West Nile Virus (WNV) have been shown to protect against infection in animal models and have been identified as a correlate of protection in WNV vaccine studies. In the present study, antibody repertoires from three convalescent WNV-infected patients were cloned into an scFv phage library, and 138 human MAbs binding to WNV were identified. One hundred twenty-one MAbs specifically bound to the viral envelope (E) protein and four MAbs to the premembrane (prM) protein. Enzyme-linked immunosorbent assay-based competitive-binding assays with representative E protein-specific MAbs demonstrated that 24/51 (47%) bound to domain II while only 4/51 (8%) targeted domain III. In vitro neutralizing activity was demonstrated for 12 MAbs, and two of these, CR4374 and CR4353, protected mice from lethal WNV challenge at 50% protective doses of 12.9 and 357 μg/kg of body weight, respectively. Our data analyzing three infected individuals suggest that the human anti-WNV repertoire after natural infection is dominated by nonneutralizing or weakly neutralizing MAbs binding to domain II of the E protein, while domain III-binding MAbs able to potently neutralize WNV in vitro and in vivo are rare.

Human Monoclonal Antibody Combination against SARS Coronavirus: Synergy and Coverage of Escape Mutants

Background Experimental animal data show that protection against severe acute respiratory syndrome coronavirus (SARS-CoV) infection with human monoclonal antibodies (mAbs) is feasible. For an effective immune prophylaxis in humans, broad coverage of different strains of SARS-CoV and control of potential neutralization escape variants will be required. Combinations of virus-neutralizing, noncompeting mAbs may have these properties. Methods and Findings Human mAb CR3014 has been shown to completely prevent lung pathology and abolish pharyngeal shedding of SARS-CoV in infected ferrets. We generated in vitro SARS-CoV variants escaping neutralization by CR3014, which all had a single P462L mutation in the glycoprotein spike (S) of the escape virus. In vitro experiments confirmed that binding of CR3014 to a recombinant S fragment (amino acid residues 318–510) harboring this mutation was abolished. We therefore screened an antibody-phage library derived from blood of a convalescent SARS patient for antibodies complementary to CR3014. A novel mAb, CR3022, was identified that neutralized CR3014 escape viruses, did not compete with CR3014 for binding to recombinant S1 fragments, and bound to S1 fragments derived from the civet cat SARS-CoV-like strain SZ3. No escape variants could be generated with CR3022. The mixture of both mAbs showed neutralization of SARS-CoV in a synergistic fashion by recognizing different epitopes on the receptor-binding domain. Dose reduction indices of 4.5 and 20.5 were observed for CR3014 and CR3022, respectively, at 100% neutralization. Because enhancement of SARS-CoV infection by subneutralizing antibody concentrations is of concern, we show here that anti-SARS-CoV antibodies do not convert the abortive infection of primary human macrophages by SARS-CoV into a productive one. Conclusions The combination of two noncompeting human mAbs CR3014 and CR3022 potentially controls immune escape and extends the breadth of protection. At the same time, synergy between CR3014 and CR3022 may allow for a lower total antibody dose to be administered for passive immune prophylaxis of SARS-CoV infection.

Severe acute respiratory syndrome (SARS)—paradigm of an emerging viral infection

n Abstractn n An acute and often severe respiratory illness emerged in southern China in late 2002 and rapidly spread to different areas of the Far East as well as several countries around the globe. When the outbreak of this apparently novel infectious disease termed severe acute respiratory syndrome (SARS) came to an end in July 2003, it had caused over 8000 probable cases worldwide and more than 700 deaths.n Starting in March 2003, the World Health Organization (WHO) organised an unprecedented international effort by leading laboratories working together to find the causative agent. Little more than one week later, three research groups from this WHO-coordinated network simultaneously found evidence of a hitherto unknown coronavirus in SARS patients, using different approaches. After Koch’s postulates had been fulfilled, WHO officially declared on 16 April 2003 that this virus never before seen in humans is the cause of SARS.n Ever since, progress around SARS-associated coronavirus (SARS-CoV) has been swift. Within weeks of the first isolate being obtained, its complete genome was sequenced. Diagnostic tests based on the detection of SARS-CoV RNA were developed and made available freely and widely; nevertheless the SARS case definition still remains based on clinical and epidemiological criteria. The agent’s environmental stability, methods suitable for inactivation and disinfection, and potential antiviral compounds have been studied, and development of vaccines and immunotherapeutics is ongoing.n Despite its grave consequences in humanitarian, political and economic terms, SARS may serve as an example of how much can be achieved through a well-coordinated international approach, combining the latest technological advances of molecular virology with more “traditional” techniques carried out to an excellent standard.n n

Severe acute respiratory syndrome: identification of the etiological agent.

n Abstractn n The severe acute respiratory syndrome (SARS) emerged in late 2002 in southern China and rapidly spread to countries around the globe. Three research groups within a World Health Organization (WHO)-coordinated network have independently and simultaneously shown that a novel coronavirus is linked to SARS. A fourth group has completed the Kochs postulates by infecting monkeys with the agent. Sequencing of the complete genome was achieved only weeks after the first isolate of the virus became available.n n

Stability and inactivation of SARS coronavirus.

The SARS-coronavirus (SARS-CoV) is a newly emerged, highly pathogenic agent that caused over 8,000 human infections with nearly 800 deaths between November 2002 and September 2003. While direct person-to-person transmission via respiratory droplets accounted for most cases, other modes have not been ruled out. Faecal shedding is common and prolonged and has caused an outbreak in Hong Kong. We studied the stability of SARS-CoV under different conditions, both in suspension and dried on surfaces, in comparison with other human-pathogenic viruses, including human coronavirus HCoV-229E. In suspension, HCoV-229E gradually lost its infectivity completely while SARS-CoV retained its infectivity for up to 9 days; in the dried state, survival times were 24xa0h versus 6 days. Thermal inactivation at 56°C was highly effective in the absence of protein, reducing the virus titre to below detectability; however, the addition of 20% protein exerted a protective effect resulting in residual infectivity. If protein-containing solutions are to be inactivated, heat treatment at 60°C for at least 30xa0min must be used. Different fixation procedures, e.g. for the preparation of immunofluorescence slides, as well as chemical means of virus inactivation commonly used in hospital and laboratory settings were generally found to be effective. Our investigations confirm that it is possible to care for SARS patients and to conduct laboratory scientific studies on SARS-CoV safely. Nevertheless, the agent’s tenacity is considerably higher than that of HCoV-229E, and should SARS re-emerge, increased efforts need to be devoted to questions of environmental hygiene.

Laboratory Diagnosis of Norovirus: Which Method Is the Best?

Noroviruses (NV) are transmitted by fecally contaminated food, vomit, and person-to-person contact. They are one of the main causes of non-bacterial acute gastroenteritis in nursing, old people and children’s homes. NV outbreaks are characterized by a short incubation period (12–48 h), nausea, vomiting and diarrhea, and high secondary attack rates. The illness is generally mild and self-limiting. The aim of diagnostic procedures in viral gastroenteritis is to avoid nosocomial infections on the one hand and unnecessary antibiotic treatment on the other. Diagnostic procedures for NV are based on the detection of virus in stool samples by (immune) transmission electron microscopy (TEM), antigen ELISA, or polymerase chain reaction (PCR). In our study, a total of 244 stool samples obtained from 227 patients between March and May 2002 were tested by TEM, antigen ELISA and in-house PCR. Our data showed that PCR has the highest sensitivity (94.1%), followed by TEM (58.3%), and ELISA (31.3%), while specificity was highest for TEM (98.0%), followed by ELISA (94.9%), and PCR (92.4%). All three methods tested (TEM, ELISA and PCR) are useful for epidemiological investigations in gastroenteritis outbreaks; however, to maximize diagnostic validity for individual cases, at least two of the methods should be combined.

Molecular and Biological Characterization of Human Monoclonal Antibodies Binding to the Spike and Nucleocapsid Proteins of Severe Acute Respiratory Syndrome Coronavirus

ABSTRACT Human monoclonal antibodies (MAbs) were selected from semisynthetic antibody phage display libraries by using whole irradiated severe acute respiratory syndrome (SARS) coronavirus (CoV) virions as target. We identified eight human MAbs binding to virus and infected cells, six of which could be mapped to two SARS-CoV structural proteins: the nucleocapsid (N) and spike (S) proteins. Two MAbs reacted with N protein. One of the N protein MAbs recognized a linear epitope conserved between all published human and animal SARS-CoV isolates, and the other bound to a nonlinear N epitope. These two N MAbs did not compete for binding to SARS-CoV. Four MAbs reacted with the S glycoprotein, and three of these MAbs neutralized SARS-CoV in vitro. All three neutralizing anti-S MAbs bound a recombinant S1 fragment comprising residues 318 to 510, a region previously identified as the SARS-CoV S receptor binding domain; the nonneutralizing MAb did not. Two strongly neutralizing anti-S1 MAbs blocked the binding of a recombinant S fragment (residues 1 to 565) to SARS-CoV-susceptible Vero cells completely, whereas a poorly neutralizing S1 MAb blocked binding only partially. The MAb ability to block S1-receptor binding and the level of neutralization of the two strongly neutralizing S1 MAbs correlated with the binding affinity to the S1 domain. Finally, epitope mapping, using recombinant S fragments (residues 318 to 510) containing naturally occurring mutations, revealed the importance of residue N479 for the binding of the most potent neutralizing MAb, CR3014. The complete set of SARS-CoV MAbs described here may be useful for diagnosis, chemoprophylaxis, and therapy of SARS-CoV infection and disease.

Activation of the Cytokine Network and Unfavorable Outcome in Patients with Yellow Fever

To study the contribution of inflammatory mediators to the pathogenesis of yellow fever (YF), the serum levels of several cytokines and chemokines were measured in 7 patients with fatal YF (f-YF), 11 patients with nonfatal hemorrhagic YF (nf/h-YF), and 18 patients with nonfatal nonhemorrhagic YF (nf/nh-YF). The levels of interleukin (IL)-6, monocyte chemoattractant protein-1, interferon-inducible protein (IP)-10, tumor necrosis factor- alpha , and IL-1 receptor antagonist (IL-1RA) were all statistically significantly higher in the patients with f-YF than in those with nf/nh-YF. In patients with nf/h-YF, only levels of IP-10 and IL-1RA were significantly elevated. The high levels of pro- and anti-inflammatory cytokines and chemokines in serum from patients with f-YF are reminiscent of those seen in patients with bacterial sepsis. This finding has implications for the understanding of the pathophysiology of YF and the development of therapeutic strategies.