The novel coronavirus 2019-nCoV has recently emerged as a human pathogen in the city of Wuhan in China’s Hubei province, causing fever, severe respiratory illness, and pneumonia—a disease recently named COVID-19 (
1,
2). According to the World Health Organization (WHO), as of 16 February 2020, there had been >51,000 confirmed cases globally, leading to at least 1600 deaths. The emerging pathogen was rapidly characterized as a new member of the betacoronavirus genus, closely related to several bat coronaviruses and to severe acute respiratory syndrome coronavirus (SARS-CoV) (
3,
4). Compared with SARS-CoV, 2019-nCoV appears to be more readily transmitted from human to human, spreading to multiple continents and leading to the WHO’s declaration of a Public Health Emergency of International Concern (PHEIC) on 30 January 2020 (
1,
5,
6).
2019-nCoV makes use of a densely glycosylated spike (S) protein to gain entry into host cells. The S protein is a trimeric class I fusion protein that exists in a metastable prefusion conformation that undergoes a substantial structural rearrangement to fuse the viral membrane with the host cell membrane (
7,
8). This process is triggered when the S1 subunit binds to a host cell receptor. Receptor binding destabilizes the prefusion trimer, resulting in shedding of the S1 subunit and transition of the S2 subunit to a stable postfusion conformation (
9). To engage a host cell receptor, the receptor-binding domain (RBD) of S1 undergoes hinge-like conformational movements that transiently hide or expose the determinants of receptor binding. These two states are referred to as the “down” conformation and the “up” conformation, where down corresponds to the receptor-inaccessible state and up corresponds to the receptor-accessible state, which is thought to be less stable (
10–
13). Because of the indispensable function of the S protein, it represents a target for antibody-mediated neutralization, and characterization of the prefusion S structure would provide atomic-level information to guide vaccine design and development.
Based on the first reported genome sequence of 2019-nCoV (
4), we expressed ectodomain residues 1 to 1208 of 2019-nCoV S, adding two stabilizing proline mutations in the C-terminal S2 fusion machinery using a previous stabilization strategy that proved effective for other betacoronavirus S proteins (
11,
14).
Figure 1A shows the domain organization of the expression construct, and figure S1 shows the purification process. We obtained ~0.5 mg/liter of the recombinant prefusion-stabilized S ectodomain from FreeStyle 293 cells and purified the protein to homogeneity by affinity chromatography and size-exclusion chromatography (fig. S1). Cryo–electron microscopy (cryo-EM) grids were prepared using this purified, fully glycosylated S protein, and preliminary screening revealed a high particle density with little aggregation near the edges of the holes.
After collecting and processing 3207 micrograph movies, we obtained a 3.5-Å-resolution three-dimensional (3D) reconstruction of an asymmetrical trimer in which a single RBD was observed in the up conformation. (
Fig. 1B, fig. S2, and table S1). Because of the small size of the RBD (~21 kDa), the asymmetry of this conformation was not readily apparent until ab initio 3D reconstruction and classification were performed (
Fig. 1B and fig. S3). By using the 3D variability feature in cryoSPARC v2 (
15), we observed breathing of the S1 subunits as the RBD underwent a hinge-like movement, which likely contributed to the relatively poor local resolution of S1 compared with the more stable S2 subunit (movies S1 and S2). This seemingly stochastic RBD movement has been captured during structural characterization of the closely related betacoronaviruses SARS-CoV and MERS-CoV, as well as the more distantly related alphacoronavirus porcine epidemic diarrhea virus (PEDV) (
10,
11,
13,
16). The observation of this phenomenon in 2019-nCoV S suggests that it shares the same mechanism of triggering that is thought to be conserved among the Coronaviridae, wherein receptor binding to exposed RBDs leads to an unstable three-RBD up conformation that results in shedding of S1 and refolding of S2 (
11,
12).
Because the S2 subunit appeared to be a symmetric trimer, we performed a 3D refinement imposing C3 symmetry, resulting in a 3.2-Å-resolution map with excellent density for the S2 subunit. Using both maps, we built most of the 2019-nCoV S ectodomain, including glycans at 44 of the 66
N-linked glycosylation sites per trimer (fig. S4). Our final model spans S residues 27 to 1146, with several flexible loops omitted. Like all previously reported coronavirus S ectodomain structures, the density for 2019-nCoV S begins to fade after the connector domain, reflecting the flexibility of the heptad repeat 2 domain in the prefusion conformation (fig. S4A) (
13,
16–
18).
The overall structure of 2019-nCoV S resembles that of SARS-CoV S, with a root mean square deviation (RMSD) of 3.8 Å over 959 Cα atoms (
Fig. 2A). One of the larger differences between these two structures (although still relatively minor) is the position of the RBDs in their respective down conformations. Whereas the SARS-CoV RBD in the down conformation packs tightly against the N-terminal domain (NTD) of the neighboring protomer, the 2019-nCoV RBD in the down conformation is angled closer to the central cavity of the trimer (
Fig. 2B). Despite this observed conformational difference, when the individual structural domains of 2019-nCoV S are aligned to their counterparts from SARS-CoV S, they reflect the high degree of structural homology between the two proteins, with the NTDs, RBDs, subdomains 1 and 2 (SD1 and SD2), and S2 subunits yielding individual RMSD values of 2.6 Å, 3.0 Å, 2.7 Å, and 2.0 Å, respectively (
Fig. 2C).
2019-nCoV S shares 98% sequence identity with the S protein from the bat coronavirus RaTG13, with the most notable variation arising from an insertion in the S1/S2 protease cleavage site that results in an “RRAR” furin recognition site in 2019-nCoV (
19) rather than the single arginine in SARS-CoV (fig. S5) (
20–
23). Notably, amino acid insertions that create a polybasic furin site in a related position in hemagglutinin proteins are often found in highly virulent avian and human influenza viruses (
24). In the structure reported here, the S1/S2 junction is in a disordered, solvent-exposed loop. In addition to this insertion of residues in the S1/S2 junction, 29 variant residues exist between 2019-nCoV S and RaTG13 S, with 17 of these positions mapping to the RBD (figs. S5 and S6). We also analyzed the 61 available 2019-nCoV S sequences in the Global Initiative on Sharing All Influenza Data database (
https://www.gisaid.org/) and found that there were only nine amino acid substitutions among all deposited sequences. Most of these substitutions are relatively conservative and are not expected to have a substantial effect on the structure or function of the 2019-nCoV S protein (fig. S6).
Recent reports demonstrating that 2019-nCoV S and SARS-CoV S share the same functional host cell receptor, angiotensin-converting enzyme 2 (ACE2) (
22,
25–
27), prompted us to quantify the kinetics of this interaction by surface plasmon resonance. ACE2 b ound to the 2019-nCoV S ectodomain with ~15 nM affinity, which is ~10- to 20-fold higher than ACE2 binding to SARS-CoV S (
Fig. 3A and fig. S7) (
14). We also formed a complex of ACE2 bound to the 2019-nCoV S ectodomain and observed it by negative-stain EM, which showed that it strongly resembled the complex formed between SARS-CoV S and ACE2 that has been observed at high resolution by cryo-EM (
Fig. 3B) (
14,
28). The high affinity of 2019-nCoV S for human ACE2 may contribute to the apparent ease with which 2019-nCoV can spread from human to human (
1); however, additional studies are needed to investigate this possibility.
The overall structural homology and shared receptor usage between SARS-CoV S and 2019-nCoV S prompted us to test published SARS-CoV RBD-directed monoclonal antibodies (mAbs) for cross-reactivity to the 2019-nCoV RBD (
Fig. 4A). A 2019-nCoV RBD-SD1 fragment (S residues 319 to 591) was recombinantly expressed, and appropriate folding of this construct was validated by measuring ACE2 binding using biolayer interferometry (BLI) (
Fig. 4B). Cross-reactivity of the SARS-CoV RBD-directed mAbs S230, m396, and 80R was then evaluated by BLI (
12,
29–
31). Despite the relatively high degree of structural homology between the 2019-nCoV RBD and the SARS-CoV RBD, no binding to the 2019-nCoV RBD could be detected for any of the three mAbs at the concentration tested (1 μM) (
Fig. 4C), in contrast to the strong binding that we observed to the SARS-CoV RBD (fig. S8). Although the epitopes of these three antibodies represent a relatively small percentage of the surface area of the 2019-nCoV RBD, the lack of observed binding suggests that SARS-directed mAbs will not necessarily be cross-reactive and that future antibody isolation and therapeutic design efforts will benefit from using 2019-nCoV S proteins as probes.
The rapid global spread of 2019-nCoV, which prompted the PHEIC declaration by WHO, signals the urgent need for coronavirus vaccines and therapeutics. Knowing the atomic-level structure of the 2019-nCoV spike will allow for additional protein-engineering efforts that could improve antigenicity and protein expression for vaccine development. The structural data will also facilitate the evaluation of 2019-nCoV spike mutations that will occur as the virus undergoes genetic drift and help to define whether those residues have surface exposure and map to sites of known antibody epitopes for other coronavirus spike proteins. In addition, the structure provides assurance that the protein produced by this construct is homogeneous and in the prefusion conformation, which should maintain the most neutralization-sensitive epitopes when used as candidate vaccine antigens or B cell probes for isolating neutralizing human mAbs. Furthermore, the atomic-level detail will enable the design and screening of small molecules with fusion-inhibiting potential. This information will support precision vaccine design and the discovery of antiviral therapeutics, accelerating medical countermeasure development.
Acknowledgments
We thank J. Ludes-Meyers for assistance with cell transfection, members of the McLellan laboratory for critical reading of the manuscript, and A. Dai from the Sauer Structural Biology Laboratory at the University of Texas at Austin for assistance with microscope alignment.
Funding: This work was supported in part by a National Institutes of Health (NIH)/National Institute of Allergy and Infectious Diseases (NIAID) grant awarded to J.S.M. (R01-AI127521) and by intramural funding from NIAID to B.S.G. The Sauer Structural Biology Laboratory is supported by the University of Texas College of Natural Sciences and by award RR160023 from the Cancer Prevention and Research Institute of Texas (CPRIT).
Author contributions: D.W. collected and processed cryo-EM data. D.W., N.W., and J.S.M. built and refined the atomic model. N.W. designed and cloned all constructs. D.W., N.W., K.S.C., J.A.G., and O.A. expressed and purified proteins. D.W., J.A.G., and C.-L.H. performed binding studies. B.S.G. and J.S.M. supervised experiments. D.W., B.S.G., and J.S.M. wrote the manuscript with input from all authors.
Competing interests: N.W., K.S.C., B.S.G., and J.S.M. are inventors on U.S. patent application no. 62/412,703 (“Prefusion Coronavirus Spike Proteins and Their Use”), and D.W., N.W., K.S.C., O.A., B.S.G., and J.S.M. are inventors on U.S. patent application no. 62/972,886 (“2019-nCoV Vaccine”).
Data and materials availability: Atomic coordinates and cryo-EM maps of the reported structure have been deposited in the Protein Data Bank under accession code 6VSB and in the Electron Microscopy Data Bank under accession codes EMD-21374 and EMD-21375. Plasmids are available from B.S.G. under a material transfer agreement with the NIH or from J.S.M. under a material transfer agreement with The University of Texas at Austin.
License information: This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit
https://creativecommons.org/licenses/by/4.0/. This license does not apply to figures/photos/artwork or other content included in the article that is credited to a third party; obtain authorization from the rights holder before using such material.
Re: pH boosters/regulator as a potential candidate in managing COVID19
Thanks to Wrapp et al [1] for coming up with a clear picture of the 2019-nCoV spike structure. This work along with some others (e.g, https://www.ncbi.nlm.nih.gov/books/NBK554776/) very clearly shows that the viral membrane consists of proteins (the S-protein) which are fatty in nature. This fatty nature of the virus spike suggests that its survival on a basic media will be highly compromised. In other words, pH booster like pantoprazole can be helpful in managing the life threatening situation in critically sick patients suffering from COVID-19. W. Londong in his work [2] very clearly shows how administration of pantoprazole helps in increasing 24-h intragastric pH value on humans.
If the blood pH values of COVID19 patients are increased (> 7.5) beyond the value of the same at the time of n-CoV infection, its basic nature will destroy the fatty viral membrane to eventually kill the virus. This may prove life saving in critically sick patients. In view of the above adopting following steps can help in not only managing the crisis well but also may prove to be life saving:
(a) To administer pH boosters (e.g, pantoprazole, ranitidine, omeprazole etc.) to moderate to critically sick COVID19 patients with an understanding that it may induce alkalosis that can be managed relatively easier as it does not carry consequences more severe than COVID19.
(b) Local administration of pH boosters, similar to the use of inhalers by an asthma patient, to critically sick COVID19 patients if all attempts to save life seems to be failed analogous to "micro-defibrillators".
(c) To monitor blood/saliva/BAL pH values from COVID19 patients and comparing it with healthy patients (pH: ~ 7.45) to optimise choice and dose of appropriate pH booster. Alternatively, to analyze the available blood/saliva/BAL pH values' data from existing patients if the data is available.
Additionally, control experiments should be carried to further validate the assumption and decide on appropriate pH boosters for other fatty membrane viruses.
Furthermore, administering pH booster will help addressing possible gastrointestinal manifestations and potential fecal-oral transmission as reported recently [3,4]. Henceforth, co-infection or co-factors may control efficiently which also sabotage corona pathogenesis inside host and potentially get treated through this method.
References
[1] D. Wrapp et al., Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation, Science 367 (2020), 1260.
[2] W. Londong, Effect of pantoprazole on 24-h intragastric pH and serum gastrin in humans, Alimentary Pharmacology and Therapeutics 08 (1994) 39
[3] J. Gu et al., COVID-19: Gastrointestinal manifestations and potential fecal-oral transmission, Gastroenterology, In Press (2020) (https://doi.org/10.1053/j.gastro.2020.02.054)[4] F. Xiao et al., Evidence for gastrointestinal infection of SARS-CoV-2, Gastroenterology, In Press (2020) (https://doi.org/10.1053/j.gastro.2020.02.055)
RE: Comments on "Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation"
Comments on "Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation"
Sheng Chen 1* and Edward Wai-Chi Chan2
1Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
2State Key Lab of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;
*Corresponding author: Sheng Chen, City University of Hong Kong, Kowloon, Hong Kong;
Email: [email protected]
Keywords: SARS-CoV-2, ACE2, spike protein, conformation, receptor binding
Abstract
Wrapp et al. (Reports, February 19, 2020) reported the structure of the spike protein (S) of the novel coronavirus, SARS-CoV-2, in the prefusion conformation and concluded that the protein could bind to the human cell receptor ACE2 with an affinity 10~20-fold higher than that of SARS-CoV-1. However, this finding is not consistent with current results of protein structure studies in which only two interaction sites between SARS-CoV-2 and ACE2 were identified, whereas five were observed in the case of SARS-CoV-1. These structural data, which suggest that binding of SARS-CoV-2 to ACE2 is actually much weaker, are more consistent with the longer incubation period and relatively low pathogenicity of this new coronavirus. The high transmission potential of SARS-CoV-2 may be due to these disease features.
Wrapp etc.(1) recently reported the Cryo-EM structure of the 2019-nCoV spike protein in prefusion conformation. In this study, the author quantified the kinetics of interaction of S protein (S) and ACE2, the human receptor of SARS-CoV-2 virus, by surface plasmon resonance (SPR). Their data showed that ACE2 bound to the S ectodomain of 2019-nCoV with ~15 nM affinity, which is approximately 10- to 20-fold higher than the affinity of SARS-CoV S to ACE2. They also formed and analyzed a complex of ACE2 and the 2019-nCoV S ectodomain by negative-stain EM, and showed that it strongly resembled the complex that formed between SARS-CoV S and ACE2 and was observed at high-resolution by cryo-EM. The author then stated that the high affinity of SARS-CoV-2 S for human ACE2 may contribute to the ability of 2019-nCoV to undergo efficient human-to-human transmission. We would like to point out that additional studies are needed to confirm this possibility. Since the authors have obtained the complex structure of S and ACE2, they should look in detail the sites and nature of interaction between S and ACE2 to explain why binding of S of SARS-CoV-2 to ACE2 is 10~20-fold higher when compared to SARS-CoV. The binding affinity between two proteins is normally determined not only by the shape of the interaction interface, but also by the relative number of ionic interaction, hydrophobic interaction, hydrogen bonding and cation-π interaction involved. We recently analyzed interaction between S of SARS-CoV-2 and ACE2, using the complex structure of RBS of S of SARS-CoV and ACE2 (2ajf) as reference (2). Our modeled complex structure was highly similar to the atomic structure of the SARS-CoV-2 S-ACE2 complex reported by other groups, suggesting that the protein modeling approach is highly reliable. Structural analysis of interaction between RBD of S of SARS-CoV and human ACE2 identified several sites where interaction of different nature occurred. These include four hydrophobic interactions: ACE2(Y41)/ RBD(Y484), ACE2(L45)/ RBD(Y484), ACE2(L79, M82)/ RBD(L472), ACE2(Y83)/ RBD(Y475), one salt-bridge: ACE2(E329)/ RBD(R426) and one cation-π interaction: ACE2(K353)/ RBD(Y491). However, examination of interaction between RBD of 2019-nCoV and human ACE2 depicted only one potential hydrophobic interaction between ACE2(L79, M82) and RBD(F486), and one cation-π interaction: ACE2(K353)/ RBD(Y492). Further examination of RBD from bat SARS-like coronaviruses, including bat-SL-CoVZX45 and bat coronavirus HKU3-1which do not infect human, depicted only one cation-π interaction, ACE2(K353)/ RBD(Y481)(3, 4). Another bat-originated coronavirus, bat SARS CoV W1V1, which exhibits strong binding affinity to ACE2 and hence high potential to cause human infection, was also included in the analysis(5). Binding affinity of RBD from this virus to ACE2 was found to be as tight as the human SARS virus, involving four hydrophobic interactions: ACE2(Y41)/ RBD(Y485), ACE2(L45)/ RBD(Y485), ACE2(L79, M82)/ RBD(F473), ACE2(Y83)/ RBD(Y476), one salt-bridge: ACE2(E329)/ RBD(R427) and one cation-π interaction site ACE2(K353)/ RBD(Y492) (6). These data suggested that a higher binding affinity of RBD of the coronavirus to ACE2 is associated with higher infectivity and pathogenicity. The fact that the RBD of SARS-CoV-2 exhibited much lower affinity to ACE2 implies that the virulence potential of SARS-CoV-2 should be much lower than that of the human SARS virus, but is nevertheless stronger than viruses that do not cause human infection(3, 4). Despite a lack of binding assay data to confirm the strength of protein-protein interaction, we wish to stress that the SPR binding data reported in this study are actually contradictory to the structural data reported in various recent studies; this issue was not highlighted and discussed by the author. Furthermore, the authors claimed that the high affinity of SARS-CoV-2 S for human ACE2 may contribute to the apparent ease with which 2019-nCoV can spread between human. Although a high binding affinity of S to ACE2 would render the virus highly infectious, such high affinity should also confer high level virulence. The fact is that SARS-CoV-2 exhibits much lower pathogenicity when compared to SARS-CoV-1. Infection by this new coronavirus is therefore associated with a much lower mortality rate and often mild symptoms. In fact, the lower pathogenicity of SARS-CoV-2 results in a longer incubation period prior to symptom onset, during which the patient would already be infectious. We believe this is the real reason why this virus can spread even more efficiently then SAR-CoV-1 in the human population although its binding affinity to ACE2 is weaker than SARS-CoV-1.
Acknowledgments
This study was not supported by any research grant.
Conflicts of interest
We declare that we have no conflict of interest.
Reference:
1. D. Wrapp et al., Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science, (2020).
2. F. Li, W. Li, M. Farzan, S. C. Harrison, Structure of SARS coronavirus spike receptor-binding domain complexed with receptor. Science 309, 1864-1868 (2005).
3. S. R. Dominguez et al., Isolation, propagation, genome analysis and epidemiology of HKU1 betacoronaviruses. J Gen Virol 95, 836-848 (2014).
4. D. Hu et al., Genomic characterization and infectivity of a novel SARS-like coronavirus in Chinese bats. Emerg Microbes Infect 7, 154 (2018).
5. X. Y. Ge et al., Isolation and characterization of a bat SARS-like coronavirus that uses the ACE2 receptor. Nature 503, 535-538 (2013).
6. N. D. X. Y. L. Y. K. C. E. C. S. Chen, Genomic and protein structure modelling analysis depicts the origin and pathogenicity of 2019-nCoV, a new coronavirus which caused a pneumonia outbreak in Wuhan. F1000Research 9:121 (2020).
RE: Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation
Gender-specific Coronavirus-infections in the light of evolution
In their Report "Cryo-EM structure of the 2019-nCoV" (Science 367, p. 1260–1263; 2020), D. Wrapp et al. write that "The novel coronavirus 2019-nCoV has recently emerged as a human pathogen in the city of Wuhan in China's Hubei province, causing fever, severe respiratory illness, and pneumonia." In addition, the authors refer to the rising number of deaths since the official outbreak on December 29, 2019.
However, with respect to mortality, this disease, recently named "Covid-19", displays a strong gender-specific occurrence that may be explained in the light of evolution. Four decades ago, A. D. Pickering and P. Christie published a remarkable article entitled "Sexual differences in the incidence and severity of ectoparasitic infestation of the brown trout, Salmo trutta L." (1). The authors reported that adult males of this fish species are more frequently (and severely) infested by a number of parasites than females of the same age. Remarkably, juvenile fish of both genders were found to be less attacked compared to sexually mature males (1). Numerous papers that were subsequently published "in the wake of Pickering & Christie 1980" have documented that there are gender-specific (or "sex-based") differences in immunological responses, both to foreign and self-antigens. As a result, in 2009, M. Zuk (2) labelled males as "the sicker sex".
In two recent Review Articles entitled "Sex differences in immune responses" (3) and "Sexual dimorphism in innate immunity" (4), the following facts were summarized. First, not only in fish (i.e., freshwater vertebrates) (1), but also in reptiles, birds, the house mouse and Rhesus macaques, immune responses are greater in females compared to males. In addition, three invertebrates species, the Sea urchin, the Fruit fly, and Scorpion flies, considerable "sex differences" in specific immune responses were documented – with a larger protective effect in females compared to males. Hence, the well-documented finding that women have a more efficient immune system than men must be interpreted as an early "innovation" during the course of organismic evolution. When challenged by pathogens (bacteria, viruses etc.), female organisms can mount a much stronger immune response to the invading microbes compared to men.
Second, in our own species, over the life course (in utero, childhood, adulthood, old age) immune responses change and display the gender-specific pattern outline above: females have a stronger immune system than men, irrespective of the age of the individual (3, 4).
With respect to the "Covid-19"-pneumonia disease, it has been argued that "The coronavirus seems to hit men harder than women" (5). This conclusion is supported by the fact that, although both sexes have been infected in about equal numbers, the death rate in China was 2.8 vs. 1.7 % in men and women, respectively (n = 44.000 people). In other areas outside the epicenter of "Covid-19" (Hubei Province), a different pattern is documented. Despite lower mortalities, the infection rates of Chinese men were much higher than in the female sub-population (5). Moreover, in a report entitled "Analysis: Why have there been so many coronavirus deaths in Italy?", it was shown that, based on Government data, "The large majority of the deceased were male, and all were Italian citizens" (6).
Despite the fact that these "sex differences" in mortality rates may be, in part, due to gender-specific "life styles" (smoking etc.), there is evidence to suggest that the male vs. female-disparity with respect to "Covid-19" is an evolved feature related to bi-parental reproduction. In the house mouse, "Sex-based differences in susceptibility to SARS-CoV-infection" were detected (7). Under lab-conditions, the mortality rate in male mice was 90 %, compared to 20 % in females. It follows that, regarding coronavirus-infections, mice show a similar sexual dimorphic pattern in survival, as documented in humans (2, 3).
It is likely that the more efficient immune system in female vertebrates (fish, mice, humans) (1–4) may "confer a survival advantage to their offspring" (5), a feature that likely evolved under the selection pressure of continuous microbial pathogen attacks. Since males, whose reproductive role is to provide sperm for the fertilization of eggs, are unable to get pregnant and "become a mother", no such an "optimized immune response" developed in the "sicker sex" over evolutionary time scales.
Finally, it should be mentioned that recent research carried out by "China's Bat Women" (Zheng-Li Shi and coworkers) has shown that, like the severe acute respiratory syndrome (SARS)-virus, the novel coronavirus (2019-nCoV) originated in Chinese bats (Mammalia: order Chiroptera), from where they infected humans, which may be regarded as an "accidental host" (8). On illegal wildlife markets – a cultural tradition in Southern China, where animals such as bats, pangolins, civets etc. are sold – coronaviruses can jump to humans directly or via intermediate hosts. However, bats (a natural reservoir for many viruses) eat insects and pollinate plants. Obviously, these flying mammals are not the problem for the outbreak of this zoonotic disease.
Unfortunately, in January 2020, the Chinese Communist Government suppressed the news about the occurrence of a highly infectious new virus that can cause, when transferred from bats to humans (zoonosis), a deadly pneumonia. As a result of this censorship of "politically incorrect infos" (and the open border-ideology of globalization), the coronavirus disease 19 (Covid-19) not only rapidly spread in China via human-to-human-transmissions: due to unrestricted travelling throughout Europe, the USA and elsewhere, it developed into a pandemic.
U. Kutschera
Institute of Biology, University of Kassel, Germany
E-mail: [email protected]
References
1. A. D. Pickering, P. Christie. J. Fish Biol. 16, 669–683 (1980).
2. M. Zuk. PLoS Pathog. 5, e1000267 (2009).
3. S. L. Klein, K. L. Flanagan. Nat. Rev. Immunol. 16, 626–638 (2016).
4. S. Jaillon et al. Clinic Rev. Allerg. Immunol. 56, 308–321 (2019).
5. R. C. Rabin. The New York Times, update March 2, 1–6 (2020).
6. C. Speak. Thelocal.it, March 5, 1–6 (2020).
7. R. Channappanavar et al. J. Immunol. 198, 4046–4053 (2017).
8. J. Qiu. Scientific American, March 11, 1–8 (2020).
RE: Can you test Nano-silver as a therapeutic?
Dear Sirs: Great work. Very impressive.
I would like to call your attention to a 2010 study that details how nano silver (aka colloidal silver, aka CS) blocks the attachment of HIV-1 to himan cells. As you know, there is some similarity in the attachment characteristics with COVID-19.
I would suggest you do in vitro testing of 120 ppm CS, as this strength is the most potent, and its readily available on Amazon in the US. Colloidal silver has been used for decades for its antibiotic and antiviral properties, and is inexpensive and easy to manufacture. And to be clear, I am not talking about silver proteins, as that is a different agent altogether, although also worthy of testing.
It may be the answer you seek. As the study below indicates, it blocked attachment of HIV-1, not just initially, but for several hours after dosing. Also, it is easily administered orally or via a nebulizer.
One last thought: we have no immunity against this virus, but it had no "immunity" against nano silver.
2010 Study article:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2818642/
Also this 2005 study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1190212/
Unfractionated Heparin and Penicillin should contain 2019-nCoV
Dear Sir,
the clinical diagnosis of pneumonia is most often not confirmed by the pathologists.
Intravascular coagulation is the main actor of innate immunity.
Virus opens the door, streptococci overwhelm the functions.
This is lesson from the 1918 Pandemic: 95 % of mortality is induced by bacterial coinfection.
So penicillin and unfractionated heparin should be discussed as prevention of disseminated intravascular coagulation and bacterial superinfection.