Redondoviridae, a family of small, circular DNA viruses of the human Oro-respiratory tract that are associated with periodontitis and critical illness. Redondoviridae is the second most prevalent virus in the upper Respiratory tract next to Anelloviridae. This slide share briefly discuss the discovery, genome property, classification, replication style, Epidemiology of Redondoviridae. Additionally its clinical features and diagnosis are discussed.

1. College of Health Sciences
School of Medicine
DEPARTMENT OF MEDICAL MICROBIOLOGY,
PARASITOLOGY AND IMMUNOLOGY
COURSE TITLE: ADVANCED VIROLOGY
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2. Redondoviridae
Prepared By: Gemechis Dejene
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3. Outline
Introduction to Redondoviridae
Genome Property
Classifications
Replication
Epidemiology
Clinical features
Diagnosis
Conclusion
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4. Discovery of Redondovirus
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Redondoviridae:
from the
Spanish redondo for
“round”, circular
nature of the DNA
genome…2019

5. Redondoviridae
Small, circular ss DNA viruses, 3kb
Redondoviridae is a novel virus family within the circular Rep-
encoding single-stranded (CRESS)
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6. Genome property
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Redendovirus genome has 3 ORFs in opposite
orientations:
• Cp: encodes capsid protein
• Rep: encodes Replication-associated protein,
• ORF3 has no homology to any known protein,
but is found in all Redondovirus genomes.

7. Classifications
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 The genera has 2 species Vientovirus and
Brisavirus
Torbellino… whirlwind
Viento…Wind
Brisa… Breeze
discovery in the
respiratory tract
 Group II…Baltimore classification system
 ICTV System…

8. Natural hosts
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 Initially, a natural host
of the Redondo virus
was thought to be
only human

9. Natural hosts
Can Redondovirus infect bacteria?
Not yet!
Why not?
Redondovirus genomes do not contain the Shine-Dalgarno translation
initiation sequence
Redondovirus sequences have not been found in arrays of prokaryotic
CRISPR spacers.
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10. Replication
Redondo viruses replicate via rolling-circle replication (RCR)
Virus penetrates into the host cell
Uncoating of the virion
The viral ssDNA genome is converted to dsDNA by host polymerases
dsDNA transcription gives rise to viral mRNAs
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11. Replication…
The viral Rep protein binds to the stem-loop structure and nicks
dsDNA, creating a free 3′-OH, site DNA synthesis
The Rep protein remains covalently bonded to the 5′-phosphate end.
After one round of genome synthesis, the Rep protein releases one
ssDNA genome,
 The dsDNA template is regenerated for additional rounds of RCR.
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12. Replication
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13. Epidemiology
Redondo viruses are the 2nd most prevalent virus in human
respiratory samples
ReDoV sequences were detected only in human samples: oral
cavity, lung, nasopharynx, and rarely gut.
Widely distributed worldwide. Ethiopia???
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14. Epidemiology
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Taylor LJ, Dothard MI et al. 2021

15. Epidemiology
Table 1: Global redondovirus prevalence determined by qPCR
Taylor LJ, Dothard MI et al. 2021
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16. Clinical features
The first reported genome was discovered in the respiratory tract of
a febrile patient, tested negative for other pathogens.
Redondovirus nucleic acid sequences have been detected in both
healthy and diseased humans. Cui et al., 2017
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17. Clinical features…
Redondovirus abundance is increased in oro-respiratory samples
from individuals with:
 Periodontitis,
 Acute illness, and
 Severe COVID-19.
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18. Cont…
Table 2: Clinical Symptoms of Redondovirus-Infected Patients during
Disease Episodes
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Tu, N.T.K.; Deng et al. 2021

19. Diagnosis
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qPCR is the only detection technique, up-to-date

20. Conclusion
“Never underestimate the power of thought;
It is the greatest path to discovery.”
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21. References
1. Tu, N.T.K.; Deng, X.; Hong,N.T.T.; Ny, N.T.H.; Phuc, T.M.; Tam,P.T.T.; Han, D.A.; Ha,
L.T.T.; Thwaites,G.; Doorn, H.R.v.; et al.Redondoviridae: High Prevalence and Possibly
Chronic Shedding in HumanRespiratory Tract, but No Zoonotic Transmission. Viruses
2021,13, 533. https://doi.org/10.3390/v13040533
2. Taylor LJ, Dothard MI, Rubel MA, AllenAA, Hwang Y, Roche AM, Graham-Wooten
J,Fitzgerald AS, Khatib LA, Ranciaro A, ThompsonSR, Beggs WR, Campbell MC,
Mokone GG,Mpoloka SW, Fokunang C, Njamnshi AK,Mbunwe E, Woldemeskel D, Belay
G, NyamboT, Tishkoff SA, Collman RG, Bushman FD. 2021.Redondovirus diversity and
evolution onglobal, individual, and molecular scales. J Virol95:e00817-21.
https://doi.org/10.1128/JVI.00817-21
3. Abbas AA, Taylor LJ, Dothard MI, Leiby JS, Fitzgerald AS, Khatib LA, Collman RG,
Bushman FD. Redondoviridae, a Family of Small, Circular DNA Viruses of the Human
Oro-Respiratory Tract Associated with Periodontitis and Critical Illness. Cell Host Microbe.
2019 May 8;25(5):719-729.e4. doi: 10.1016/j.chom.2019.04.001. Erratum in: Cell Host
Microbe. 2019 Aug 14;26(2):297. PMID: 31071295; PMCID: PMC6510254.
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