1/27/2020 Editors Note: This unpublished paper was written by Xueying Qiao in August 2003, which is being released now due to its relevance to the current coronavirus infections in Wuhan, China. In this paper, Mr. Qiao hypothesizes that mutant human cells can serve as a mixing vessel or a training camp for nonhuman strains of virus to grow, adapt, reassort and develop into strains with high transmissibility among humans. He also proposes methods on how we can predict and prevent future human epidemics of nonhuman viral strains from happening again, such as the current epidemic in Wuhan, China. Please note that the data and references from this paper are from earlier than August 2003, and there are new findings since then that should be discussed (i.e. we now know that the Spanish flu from 1918-1919 epidemic is a hybrid strain of both avian flu and human influenza A)(9). A discussion about this theory and what we can extrapolate from it with modern data will be discussed in a future analysis from this date.

Aug 1, 2003

A Spy Role in Virus Invasion

Influenza virus invaded man with massive life losses three times in its recorded history. Yet, in many other cases, it often raids into human communities, reaping only a few lives at a time, striking fear into human society and vanishing itself into air.  What is the message the virus sends us? This article will present a theory of a spy role that can help to decode the message and learn how we can predict and prevent from an epidemic.

Influenza virus is harbored in wild waterfowl and varies its genome through incorporating incorrect nucleotides by its low fidelity polymerase, the so-called “antigenic drift”, gaining new characteristics to expand its host range. The virus also takes another shortcut to change its genome by acquiring gene fragments from other co-circulating subtypes, the so-called “antigenic shift”, as well as reassortment”. The variant can be new enough to begin an epidemic. It is very important to understand how a virus evolves its genomic material and where the training camp for selecting antigenic drift mutants or a mixing vessel for reassorting antigenic shift mutants is. The hypothesis shown below helps reveal answers to the questions that still remain unsolved.

Human cells resist nonhuman influenza subtypes but not human ones. Yet under certain conditions, some human cells mutate to become susceptible for nonhuman strains, providing a training camp or mixing vessel for the virus to invade, adapt and reassort. While nonhuman strains grow in these mutated cells, well-adapted virus mutants are selected. The progeny of the selected virus mutants can be transmitted to either the original host for further circulation and variation, or to other human individuals without necessarily creating an epidemic since it only attacks mutated cells that normal people carry in a small amount. However, it can be highly pathogenic to individuals who carry an adequate amount of cell mutants. Most importantly, the possibility of nonhuman viral strains shifting its genetic materials with human viral strains is increased in these mutated human cells. In case a non-human virus acquires genomic materials from others, often a co-infected human influenza virus, and if the arisen variant carries new characteristics in which enable it to invade and replicate in normal human cells, an influenza epidemic will occur.

Nonhuman viruses constantly invade humans.(1) Humans can support limited replication of avian influenza viruses that are unrelated to human strains.(2) All viruses isolated from the 1997 Hong Kong outbreak have been confirmed to be avian strains.(3) Further studies on the first isolate that killed a 3-year-old boy revealed that it remained highly pathogenic for birds(3) with little human transmissibility(4) and its receptor specificity, a property to recognize host cells, was consistent with avian strains and differed from human ones.5 The virus was also adapted to escape human host anti-viral cytokine responses through an antigenic drift, varying one amino acid at position 92 of the NS1 protein molecule.(6) These indicate that nonhuman viruses had limited capabilities to infect and replicate in humans. Yet it is already enough for them to become well adapted. It can be presumed humans carry a limited amount of mutated cells, resulting in viral adaptation in these mutated cells and thus limited infections. We may expect that these viruses will not initiate an epidemic and only individuals who carry a sufficient number of mutated cells are at risk. However, the possibility still exists that these strains can shift its genomic material in the cell mutants of a human host with a co-circulating human strain that subsequently adapt characteristics resulting in high transmissibility and can cause an epidemic.  Although it is not clear where the virus responsible for the 1918 “Spanish Flu”, which killed at least 20 million people in 1918-1919, originated from(7), the viruses responsible for the “Asia Flu” in 1957 and the “Hong Kong Flu” in 1968, which killed hundreds of thousands of people worldwide, are reassortants between human and avian strains.(4) Nevertheless, antigenic drift is key to the emergence of most epidemics, including ones caused by viral antigenic shift because they often concurrently emerge with virus adaptations, which mostly come from drifting. A drifted strain has to be selected to become effective and a mutated human cell is the best place for that selection to be possible.

There is no direct evidence yet to indicate the existence of human cell mutants in influenza virus studies. However, positive implications can be made from studies on a bacteriophage family,(8) Cystoviridae. In that family, different strains have different host ranges from others, yet they can grow in mutants of the host cells of the other phage members in the family. Every member of the family contains three double-stranded RNA genomic segments designated as L, M and S. The M genomic segment carries a set of genes that direct the bacteriophage to recognize the host cells. Among the members of this family, Φ 6 is closely related to Φ7 and able to exchange its genomic RNA segments with Φ7 whereas Φ 8 is quite distantly related toΦ6 and hardly able to exchange the genomic RNA segments with Φ6. Φ 13 is between the two groups and able to accept the entire M genomic segment from Φ 6.  However, in order for Φ 6 to accept or acquire the Φ 13 M genomic segment, a recombination between Φ 6 M genomic segment and Φ 13 M genomic segment needs to occur first, making it more difficult for it to occur naturally.  This exchange of genomic material will result in a host range change for Φ13. The primary host for Φ6 is P. syringae pv. Phaseolicola HB10Y (HB10Y). Φ13 cannot infect it and does not produce antigenic drift mutants that can do so; Φ13 can only grow in it after acquiring the M genomic segment from Φ6. However Φ13 can grow in a mutant, LM2489, isolated from HB10Y, which also supports the growth of Φ 6.  This clearly shows that mutants do exist in HB10Y that can play the role of a spy, helping Φ 13 invade, adapt and reassort with Φ 6. When Φ 13 acquires the M genomic segment from Φ 6, it is virulent to normal HB10Y cells. On the other hand, the host strain ERA, an isolate of P. pseudoalcaligenes and used in isolating Φ 13, does not grow Φ 6 unless Φ 6 obtains mutations. Yet, normal Φ 6 can propagate in a mutant of ERA, S4M, which grows both Φ 6 and Φ 13. Again, mutants in ERA can also act as collaborators for Φ 6 to invade, adapt and reassort with Φ 13 so that Φ 6 can switch its host range.

We have seen many extraordinary studies on viruses isolated from human patients during outbreaks yet little about host cells from the same patients. There are unquestionable differences between the patients who are severely susceptible to a particular nonhuman strain and normal people who are not so susceptible. One way to the search for the differences is to identify mutated cells in human patients, which may have an affinity with avian virus using the difference in receptors between human cells and avian cells. Furthermore, we may investigate the relationship between the amount of mutated cells in different human patients and the susceptibility of these patients to the virus. We should also pay more attention to studies on nonhuman viruses. If we are able to group nonhuman viruses on their mutability in adapting to human hosts and their capability in exchanging genomic material with human strains from the easiest to the hardest, we may understand the epidemic potential for each one of them. Furthermore, we may also develop vaccines according to a pattern before a particular strain can launch an attack. This will prevent from a massive loss of human lives.

Research on the influenza virus family reveals evidence that supports this hypothesis. More conclusive results were shown in the Cystoviridae. Since mutants occur in any live organisms, the principle of the hypothesis may also be true to many other virus families. Understanding the virus evolution in human cell mutants can and will help predict viral epidemic outbreak potential and decrease damages from it.

Xueying Qiao
The Public Health Research Institute
225 Warren Street, Newark NJ 07103, USA
(e-mail: xqiao@gm.slc.edu)

Edited by: Sarah Qiao (sqiao@gse.upenn.edu)

References

1.     Snacken R, Kendal AP, Haaheim LR, Wood JM. The next influenza pandemic: lessons from Hong Kong. 1997. Emerg Infect Dis 1999; 5: 195-203.

2.     Beare AS, Webster RG. Replication of avian influenza viruses in humans. Arch Virol 1991; 119: 37-42.

3.     Subbarao K, Klimov A, Katz J, et al. Characterization of an avian influenza A (H5N1) virus isolated from a child with a fatal respiratory illness.  Science 1998; 279: 393-396.

4.     Cox NJ, Subbarao K. Global epidemiology of influenza: past and present. Annu Rev Med 2000; 51: 407-421.

5.     Matrosovich M, Zhou N, Kawaoka Y, Webster R. The surface glycoproteins of H5 influenza viruses isolated from humans, chickens and wild aquatic birds have distinguishable properties. J Virol 1999; 73: 1146-1155.

6.     Seo SH, Hoffmann E, Webster RG. Lethal H5N1 influenza viruses escape host anti-viral cytokine responses. Nature Med 2002; 8: 950-954.

7.     Reid AH, Fanning TG, Hultin JV, Taubenberger JK. Origin and evolution of the 1918 “Spanish: influenza virus hemagglutinin gene. Proc Natl Acad Sci USA 1999; 96: 1651-1656.

8.     Mindich L, Qiao X, Qiao J, et at. Isolation of additional bacteriophages with genomes of segmented double-stranded RNA. J bacterial 1999; 181: 4505-4508.

9.     He CQ, He M, He HB, Wang HM, Ding NZ.  The matrix segment of the “Spanish flu” virus originated from intragenic recombination between avian and human influenza A viruses. Transboundary and Emerging Diseases 2019; 66: 2188-2195.