Biology:Parvovirus B19

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Short description: Human virus that infects RBC precursors


Parvovirus B19
Electron micrograph of Parvoviruses in blood
Virus classification e
(unranked): Virus
Realm: Monodnaviria
Kingdom: Shotokuvirae
Phylum: Cossaviricota
Class: Quintoviricetes
Order: Piccovirales
Family: Parvoviridae
Genus: Erythroparvovirus
Species:
Erythroparvovirus primate1
Synonyms
  • B19 virus
  • Erythrovirus B19
  • Human parvovirus B19
  • B19V

Parvovirus B19, also called B19 virus (B19V), Human parvovirus B19,[1] or sometimes erythrovirus B19,[2] is a human virus in the family Parvoviridae, genus Erythroparvovirus. It measures only 23–26 nm in diameter.[3] The virus is assigned to the species Erythroparvovirus primate1.[4] The name is derived from Latin parvum, meaning small, reflecting the fact that B19 ranks among the smallest DNA viruses. B19 virus is most known for causing disease in the pediatric population; however, it can also affect adults. It is the classic cause of the childhood rash called fifth disease or erythema infectiosum, or "slapped face syndrome".[5][6] The name comes from it being the fifth in a list of historical classifications of common skin rash illnesses in children.[7]

The virus was discovered by chance in 1975 by Australian virologist Yvonne Cossart.[3][6] The name B19 originated from the coding of a serum sample, number 19 in panel B.[6][8]

Virology

Erythroviruses belong to the Parvoviridae family of small DNA viruses.[9] Human parvovirus B19 is a non-enveloped, icosahedral virus that contains a single-stranded linear DNA genome of approximately 5,600 base pairs in length.[10] B19V's nonenveloped viral particles are ~22 to 24 nm in diameter which are quite small compared to other parvoviruses.[3] The infectious particles may contain either positive or negative strands of DNA. The icosahedral capsid consists of 60 capsomeres, consisting of two structural proteins, VP1 (83 kDa) and VP2 (58 kDa), which are identical except for 227 amino acids at the amino-terminal of the VP1-protein, the so-called VP1-unique region. VP2 is the major capsid protein, and comprises approximately 95% of the total virus particle. VP1-proteins are incorporated into the capsid structure in a non-stoichiometrical relation (based on antibody-binding analysis and X-ray structural analysis the VP1-unique (VP1u) region is assumed to be exposed at the surface of the virus particle.[11] VP1u is located in the N-terminus of the VP1.[12] At each end of the DNA molecule there are palindromic sequences which form "hairpin" loops. The hairpin at the 3' end serves as a primer for the DNA polymerase.[13] It is classified as an erythrovirus because of its capability to invade red blood cell precursors in the bone marrow. Three genotypes (with subtypes) have been recognised.[14]

The genome of human parvovirus B19 encodes four other proteins in addition to VP1 and VP2 and also some smaller proteins whose function is still unknown.[15] The most notable of these is the large nonstructural protein commonly referred to as NS1. NS1 is a multifunctional protein that has a role in binding and operating on the p6 promoter which gives NS1 the ability to control the transcription of the B19V genome.[16] NS1 binds and cleaves DNA in a sequence specific manner via restriction endonuclease activity of an N-terminal domain. Only single stranded DNA is cleaved, but double stranded DNA is preferentially bound, with high cooperativity that facilitates the binding of multiple NS1 units.[17] NS1 is responsible for the regulation of certain cellular promoters including the p21/WAF1 promoter,[18] and is thought to regulate the virus' own promoter.[19] The 11 kDa protein encoded by the viral genome has been implicated in viral DNA replication.[20]

The nucleotide substitution rate for total coding DNA has been estimated to be 1.03 (0.6-1.27) x 10−4 substitutions/site/year.[21] This rate is similar to that of other single-stranded DNA viruses. VP2 codons were found to be under purifying selection. In contrast VP1 codons in the unique part of the gene were found to be under diversifying selection. This diversifying selection is consistent with persistent infection as this part of the VP1 protein contains epitopes recognised by the immune system.

Studies of Parvovirus B19 (B19V) have provided insights into its persistence and integration within human tissues. Analyses revealed that B19V primarily resides in endothelial cells, monocytes, and B cells, with few documented integration events in vivo. Although B19V DNA integration has been observed in vitro, its low prevalence in sampled tissues suggests that alternative mechanisms may contribute to lifelong persistence. In one case involving pulmonary carcinoma, a B19V integration junction was found in the colon, indicating possible interactions with host genomic elements.[22]

Evolution

The most recent common ancestor of the extant strains has been dated to about 12,600 years ago.[23] Three genotypes—1, 2 and 3—are recognised. A recombination between types 1 and 3 gave rise to genotype 2 between 5,000 and 6,800 years ago.

Transmission

The virus is primarily spread by infected respiratory droplets; however, blood-borne transmission has also been reported.[24] The secondary attack risk for exposed household persons is about 50%, and about half of that for classroom contacts.[6][25] Transmission can happen from a mother that has B19V infection during pregnancy. The baby can get infected by bloodstream and therefore develop a severe anemia.[26]

Infectivity and symptoms

Two out of ten infected people do not experience any symptoms but are still highly infective. The B19V infection starts with flu-like symptoms consisting fever, headache, runny nose, sore throat, joint pain and rash.[27] Symptoms begin some six days after exposure (between 4 and 28 days, with the average being 16 to 17 days[28]) and last about a week. The rash that children experience will appear after few days after the initial symptoms and can spread all over the body.[27]

Infected patients with normal immune systems are contagious before becoming symptomatic, but probably not after.[29] Individuals with B19 IgG antibodies are generally considered immune to recurrent infection, but reinfection is possible in a minority of cases.[30] About half of adults are B19-immune due to a past infection.[26]

Immunocompromised patients (organ transplant, HIV etc.) are prone to complications that affect the nerves, joints or bloodstream.[27]

Epidemiology

A significant increase in the number of cases is seen every three to four years; the last epidemic year was 1998.[31] Outbreaks can arise especially in nurseries and schools.

Parvovirus B19 causes an infection in humans only. Cat and dog parvoviruses do not infect humans due to animals having their own parvoviruses. There is always a possibility for a spillover. There is no vaccine available for human parvovirus B19,[32] though attempts have been made to develop one.[33][34]

Role in disease

Child showing signs of erythema infectiosum, also known as fifth disease
The "slapped cheek" appearance typical of fifth disease

Fifth disease

Fifth disease or erythema infectiosum is only one of several expressions of parvovirus B19. The associated bright red rash of the cheeks gives it the nickname "slapped cheek syndrome".[6] Any age may be affected, although it is most common in children aged six to ten years. It is so named because it was the fifth most common cause of a pink-red infection associated rash to be described by physicians (many of the others, such as measles and rubella, are rare now).[35]

Once infected, patients usually develop the illness after an incubation period of four to fourteen days. The disease commences with high fever and malaise, when the virus is most abundant in the bloodstream, and patients are usually no longer infectious once the characteristic rash of this disease has appeared.[32] The following symptoms are characteristic:

  • A usual brief viral prodrome with fever, headache, nausea, diarrhea.
  • As the fever breaks, a red rash forms on the cheeks, with relative pallor around the mouth ("slapped cheek rash"), sparing the nasolabial folds, forehead, and mouth.
  • "Lace-like, (reticular)" red rash on trunk or extremities then follows the facial rash. Infection in adults usually only involves the reticular rash, with multiple joint pain predominating.
  • Exacerbation of rash by sunlight, heat, stress.

Papular purpuric gloves and socks syndrome

Teenagers or young adults may develop the so-called papular purpuric gloves and socks syndrome. It is a cutaneous condition characterized by pruritus, edema, and erythema of the hands and feet.[36]: 401  In 1996, an association with parvovirus B19 was described, after virus was demonstrated in skin biopsy samples,[37] subsequently corroborated in numerous publications.[38] [39]

Polyarthropathy syndrome

Arthralgias and arthritis are commonly reported in association with parvovirus B19 infection in adults in the absence of skin findings, whereas erythema infectiosum is the main symptom observed in children. The occurrence of arthralgia coincides with the initial detection of circulating IgM- and IgG-antibodies against the viral structural proteins VP1 and VP2. Parvovirus B19 infection may affect the development of arthritis.[11] In adults (and perhaps some children), parvovirus B19 can lead to a seronegative arthritis which is usually easily controlled with analgesics.[40] Women are approximately twice as likely as men to experience arthritis after parvovirus infection. Possibly up to 15% of all new cases of arthritis are due to parvovirus, and a history of recent contact with a patient and positive serology generally confirms the diagnosis.[29] This arthritis does not progress to other forms of arthritis. Typically joint symptoms last 1–3 weeks, but in 10–20% of those affected, it may last weeks to months.[6][32]

A Danish study has links between B19 with polymyalgia rheumatica.[41]

Aplastic crisis and chronic erythroid hypoplasia

Although most patients have a decrease of erythropoiesis (production of red blood cells) during parvovirus infection, it is most dangerous in patients with pre-existing bone marrow stress, for example sickle cell anemia or hereditary spherocytosis,[42][43] and are therefore heavily dependent on erythropoiesis due to the reduced lifespan of the red cells. This is termed "aplastic crisis" (also called reticulocytopenia). It is treated with blood transfusion.

Parvovirus B19 is a cause of chronic anemia in individuals with immunodeficiency, receiving immunosuppressive therapy or with HIV infection. Treatment with intravenous immunoglobulin usually resolves the anemia although relapse can occur. Parvovirus infection may trigger an inflammatory reaction in AIDS patients who have just begun antiretroviral therapy.[44]

Hydrops fetalis

Micrograph showing viral changes in fetal red blood cells in a case of parvovirus infection. H&E stain

Parvovirus infection in pregnant women is associated with hydrops fetalis due to severe fetal anemia, sometimes leading to miscarriage or stillbirth.[32][45] This is due to a combination of hemolysis of the red blood cells, as well as the virus directly negatively affecting the red blood cell precursors in the bone marrow. The risk of fetal loss is about 10% if infection occurs before pregnancy week 20 (especially between weeks 14 and 20), but minimal after then. Routine screening of the antenatal sample would enable the pregnant mother to determine the risk of infection. Knowledge of her status would allow the mother to avoid contact with individuals suspected or known to have an ongoing infection, however, at the present time, antenatal testing for immunity is not recommended, since there is no good means to prevent the infection, there is no specific therapy and there are no vaccines available. It may increase maternal anxiety and fear without proven benefit. The best approach would be to recommend all pregnant women to avoid contact with children with current symptoms of infection, as described above. The risk to the fetus will be reduced with correct diagnosis of the anemia (by ultrasound scans) and treatment (by blood transfusions). There is some evidence that intrauterine parvovirus B19 infection leads to developmental abnormalities in childhood.[46]

Treatment

At the moment, there are no treatments that directly target parvovirus B19 virus.[47] Intravenous immunoglobulin therapy (IVIG) therapy has been a popular alternative because doctors can administer it without stopping chemotherapy drugs like MEL-ASCT.[48] Also, the treatment's side effects are rare as only 4 out of 133 patients had complications (2 had acute kidney injury and 2 had pulmonary edema) even though 69 of the patients had organ transplants and 39 of them were HIV positive.[49] This is a large improvement over administering rituximab. The monoclonal antibody against the CD20 protein has been shown to cause acute hepatitis,[50] neutropenia via parvovirus B19 reactivations,[51] and even persistent parvovirus B19 infection.[52] However, it is important to note that IVIG therapy is not perfect as 34% of treated patients will have a relapse after 4 months.[49]

Diagnostics and vaccination

There is no routine laboratory test for B19V, but in case of the doctor is suspecting a B19V infection patient's blood will be drawn. The blood is then tested for antibodies.[26]

As of 2020, no approved human vaccine existed against parvovirus B19.[53] Bernstein et. al.[34] tested in 2011 a possible candidate vaccine that was produced in insect cells. For the vaccine VP2/VP1 VLPs (virus-like particle) were used. This vaccine was approved to the I clinical phase, but was stopped due to unexplained reactions in patients. It was argued that the reaction could have been due to the PLA2 activity in VP1u. The reaction was either to the PLA2 activity releasing arachidonic acid and precursors of inflammatory mediators or the usage of insect cells. The PLA2 activity can be reduced or fully removed with site-directed mutagenesis. So this could still act as a candidate vaccine, but further research is needed.[12]

See also

References

  1. ↑ "Clinical presentations of parvovirus B19 infection". American Family Physician 75 (3): 373–376. February 2007. PMID 17304869. 
  2. ↑ "Seroepidemiology of human bocavirus defined using recombinant virus-like particles". The Journal of Infectious Diseases 198 (1): 41–50. July 2008. doi:10.1086/588674. PMID 18491974. 
  3. ↑ 3.0 3.1 3.2 "Human parvovirus B19". Clinical Microbiology Reviews 15 (3): 485–505. July 2002. doi:10.1128/CMR.15.3.485-505.2002. PMID 12097253. 
  4. ↑ "Human parvovirus B19" (in en). https://www.ncbi.nlm.nih.gov/datasets/taxonomy/10798/. 
  5. ↑ "Parvovirus B19 infections". International Journal of Dermatology 43 (10): 747–749. October 2004. doi:10.1111/j.1365-4632.2004.02413.x. PMID 15485533. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 "Parvovirus B19 infections". American Family Physician 60 (5): 1455–1460. October 1999. PMID 10524489. http://www.aafp.org/afp/991001ap/1455.html. Retrieved 2009-11-06. 
  7. ↑ "Parvovirus B19" (in en). https://www.cdc.gov/parvovirusb19/index.html. 
  8. ↑ Siegl, Günter; Bates, Robert C.; Berns, Kenneth I.; Carter, Barrie J.; Kelly, David C.; Kurstak, Edouard; Tattersall, Peter (2008-07-25). "Characteristics and Taxonomy of Parvoviridae". Intervirology 23 (2): 61–73. doi:10.1159/000149587. ISSN 0300-5526. PMID 3980186. https://doi.org/10.1159/000149587. 
  9. ↑ "Variants of B19". Developments in Biologicals 118: 71–77. 2004. PMID 15645675. 
  10. ↑ "Human parvovirus B19: a mechanistic overview of infection and DNA replication". Future Virology 10 (2): 155–167. 2015. doi:10.2217/fvl.14.103. PMID 26097496. 
  11. ↑ 11.0 11.1 "Human parvovirus B19 infection and antiphospholipid antibodies". Autoimmunity Reviews 6 (5): 278–85. April 2007. doi:10.1016/j.autrev.2006.09.006. PMID 17412298. 
  12. ↑ 12.0 12.1 Soto-Valerio, I. A.; Cayetano-Cruz, M.; Valadez-García, J.; Guadarrama, P.; Méndez, C.; Bustos-Jaimes, I. (2022). "In vitro refolding of the structural protein VP1 of parvovirus B19 produces virus-like particles with functional VP1 unique region" (in en). Virology 570: 57–66. doi:10.1016/j.virol.2022.03.009. PMID 35367742. https://www.sciencedirect.com/science/article/pii/S0042682222000538. Retrieved 2024-02-25. 
  13. ↑ G. Siegl and P. Cassinotti, Parvoviruses Chapter 14, Topley and Wison's Microbiology and Microbial Infections, Vol. 1, Virology, 1998 pp. 261–280
  14. ↑ "Global co-existence of two evolutionary lineages of parvovirus B19 1a, different in genome-wide synonymous positions". PLOS ONE 7 (8). 2012. doi:10.1371/journal.pone.0043206. PMID 22912828. Bibcode: 2012PLoSO...743206M. 
  15. ↑ "Parvovirus B19 Achievements and Challenges" (in en). ISRN Virology 2013. April 2013. doi:10.5402/2013/898730. 
  16. ↑ Zhang, Y.; Shao, Z.; Gao, Y.; Fan, B.; Yang, J.; Chen, X.; Zhao, X.; Shao, Q. et al. (2022). "Structures and implications of the nuclease domain of human parvovirus B19 NS1 protein" (in en). Computational and Structural Biotechnology Journal 20: 4645–4655. doi:10.1016/j.csbj.2022.08.047. PMID 36090819. 
  17. ↑ "DNA Binding and Cleavage by the Human Parvovirus B19 NS1 Nuclease Domain". Biochemistry 55 (47): 6577–6593. November 2016. doi:10.1021/acs.biochem.6b00534. PMID 27809499. 
  18. ↑ "Human Parvovirus B19 nonstructural protein transactivates the p21/WAF1 through Sp1". Virology 329 (2): 493–504. November 2004. doi:10.1016/j.virol.2004.09.008. PMID 15518826. 
  19. ↑ "NS1 protein of parvovirus B19 interacts directly with DNA sequences of the p6 promoter and with the cellular transcription factors Sp1/Sp3". Virology 293 (1): 86–93. February 2002. doi:10.1006/viro.2001.1285. PMID 11853402. 
  20. ↑ "The 11-Kilodalton Nonstructural Protein of Human Parvovirus B19 Facilitates Viral DNA Replication by Interacting with Grb2 through Its Proline-Rich Motifs". Journal of Virology 93 (1). January 2019. doi:10.1128/JVI.01464-18. PMID 30282717. 
  21. ↑ "Substitution rate and natural selection in parvovirus B19". Scientific Reports 6. October 2016. doi:10.1038/srep35759. PMID 27775080. Bibcode: 2016NatSR...635759S. 
  22. ↑ "Intra-host genomic diversity and integration landscape of human tissue-resident DNA virome". Nucleic Acids Research 52 (21): 13073–13093. 2024. doi:10.1093/nar/gkae871. PMID 39436041. 
  23. ↑ "Ancient human parvovirus B19 in Eurasia reveals its long-term association with humans". Proceedings of the National Academy of Sciences of the United States of America 115 (29): 7557–7562. July 2018. doi:10.1073/pnas.1804921115. PMID 29967156. Bibcode: 2018PNAS..115.7557M. 
  24. ↑ Baron S, ed (1996). Parvoviruses. In: Barron's Medical Microbiology (4th ed.). Univ of Texas Medical Branch. ISBN 978-0-9631172-1-2. 
  25. ↑ "Parvovirus B19". The New England Journal of Medicine 350 (6): 586–597. February 2004. doi:10.1056/NEJMra030840. PMID 14762186. 
  26. ↑ 26.0 26.1 26.2 "Parvovirus B19 and Pregnancy" (in en). https://www.cdc.gov/parvovirusb19/pregnancy.html. 
  27. ↑ 27.0 27.1 27.2 "Symptoms and Complications" (in en). https://www.cdc.gov/parvovirusb19/symptoms-complications.htmll. 
  28. ↑ "Fifth Disease (for Parents)". http://kidshealth.org/parent/infections/skin/fifth.html. 
  29. ↑ 29.0 29.1 "Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19". Journal of Medical Microbiology 53 (Pt 6): 459–475. June 2004. doi:10.1099/jmm.0.05485-0. PMID 15150324. http://eprints.maynoothuniversity.ie/163/1/B19_Review_Proof.pdf. 
  30. ↑ "Parvovirus B19 infection and autoimmune disease". Autoimmunity Reviews 2 (4): 218–223. June 2003. doi:10.1016/S1568-9972(03)00014-4. PMID 12848949. 
  31. ↑ "Current epidemiological aspects of human parvovirus B19 infection during pregnancy and childhood in the western part of Germany". Epidemiology and Infection 135 (4): 563–569. May 2007. doi:10.1017/S095026880600731X. PMID 17064457. 
  32. ↑ 32.0 32.1 32.2 32.3 "Clinical presentations of parvovirus B19 infection". American Family Physician 75 (3): 373–376. February 2007. PMID 17304869. http://www.aafp.org/afp/20070201/373.html. Retrieved 2009-11-06. 
  33. ↑ "Safety and immunogenicity of a recombinant parvovirus B19 vaccine formulated with MF59C.1". The Journal of Infectious Diseases 187 (4): 675–678. February 2003. doi:10.1086/368382. PMID 12599085. 
  34. ↑ 34.0 34.1 "Safety and immunogenicity of a candidate parvovirus B19 vaccines" (in en). Vaccine 29 (43): 7357–7363. July 2011. doi:10.1016/j.vaccine.2011.07.080. PMID 21807052. 
  35. ↑ "Parvovirus B19 infection in human pregnancy". BJOG 118 (2): 175–186. January 2011. doi:10.1111/j.1471-0528.2010.02749.x. PMID 21040396. 
  36. ↑ James, William D. et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 978-0-7216-2921-6. 
  37. ↑ Aractingi, S.; Bakhos, D.; Flageul, B.; Vérola, O.; Brunet, M.; Dubertret, L.; Morinet, F. (October 1996). "Immunohistochemical and virological study of skin in the papular-purpuric gloves and socks syndrome". The British Journal of Dermatology 135 (4): 599–602. doi:10.1111/j.1365-2133.1996.tb03839.x. ISSN 0007-0963. PMID 8915154. 
  38. ↑ "Immunohistochemical detection of parvovirus B19 in "gloves and socks" papular purpuric syndrome: direct evidence for viral endothelial involvement. Report of three cases and review of the literature". The American Journal of Dermatopathology 33 (8): 790–795. December 2011. doi:10.1097/DAD.0b013e318221bc41. PMID 22024574. 
  39. ↑ Grilli, R.; Izquierdo, M.J.; Fariña, M.C.; Kutzner, H.; Gadea, I.; Martin, L.; Requena, L. (November 1999). "Papular-purpuric "gloves and socks" syndrome: Polymerase chain reaction demonstration of parvovirus B19 DNA in cutaneous lesions and sera" (in en). Journal of the American Academy of Dermatology 41 (5): 793–796. doi:10.1016/S0190-9622(99)70027-7. PMID 10534650. https://linkinghub.elsevier.com/retrieve/pii/S0190962299700277. 
  40. ↑ "Other Types of Arthritis". Arthritis Action. https://www.arthritisaction.org.uk/living/other_types. 
  41. ↑ "Synchronous variations of the incidence of temporal arteritis and polymyalgia rheumatica in different regions of Denmark; association with epidemics of Mycoplasma pneumoniae infection". The Journal of Rheumatology 23 (1): 112–119. January 1996. PMID 8838518. 
  42. ↑ "[Human parvovirus B19 as the cause of aplastic crisis in hereditary spherocytosis]". Tidsskrift for den Norske Laegeforening 111 (22): 2735–2737. September 1991. PMID 1658972. 
  43. ↑ "Aplastic crisis associated with parvovirus B19 in an adult with hereditary spherocytosis". The Journal of the Arkansas Medical Society 94 (4): 163–164. September 1997. PMID 9308316. 
  44. ↑ "Images in HIV/AIDS. Unsuspected parvovirus B19 infection in a person with AIDS". The AIDS Reader 19 (6): 225–227. June 2009. PMID 19642240. 
  45. ↑ "Parvovirus B19 in pregnancy". Reproductive Toxicology 21 (4): 421–435. May 2006. doi:10.1016/j.reprotox.2005.01.006. PMID 16580942. Bibcode: 2006RepTx..21..421E. 
  46. ↑ "Long-term outcome after fetal transfusion for hydrops associated with parvovirus B19 infection". Obstetrics and Gynecology 109 (1): 42–47. January 2007. doi:10.1097/01.AOG.0000249611.67873.94. PMID 17197586. 
  47. ↑ "Parvovirus B19 and the new century". Clinical Infectious Diseases 46 (4): 537–539. February 2008. doi:10.1086/526523. PMID 18194096. 
  48. ↑ "Preemptive intravenous immunoglobulin allows safe and timely administration of antineoplastic therapies in patients with multiple myeloma and parvovirus B19 disease". Transplant Infectious Disease 15 (4): 354–360. August 2013. doi:10.1111/tid.12067. PMID 23578205. 
  49. ↑ 49.0 49.1 "Intravenous immunoglobulin therapy for pure red cell aplasia related to human parvovirus b19 infection: a retrospective study of 10 patients and review of the literature". Clinical Infectious Diseases 56 (7): 968–977. April 2013. doi:10.1093/cid/cis1046. PMID 23243178. 
  50. ↑ "Parvovirus B19 infection-related acute hepatitis after rituximab-containing regimen for treatment of diffuse large B-cell lymphoma". Annals of Hematology 91 (2): 291–294. February 2012. doi:10.1007/s00277-011-1238-8. PMID 21538062. http://ntur.lib.ntu.edu.tw/bitstream/246246/258706/1/index.html. Retrieved 25 November 2021. 
  51. ↑ "Parvovirus B19 reactivation presenting as neutropenia after rituximab treatment". European Journal of Internal Medicine 17 (7): 505–507. November 2006. doi:10.1016/j.ejim.2006.05.002. PMID 17098597. 
  52. ↑ "Progressive bicytopenia due to persistent parvovirus B19 infection after immunochemotherapy with fludarabine/cyclophosphamide and rituximab for relapsed B cell lymphoma". Haematologica 91 (12 Suppl): ECR49. December 2006. PMID 17194655. 
  53. ↑ "Generation of a parvovirus B19 vaccine candidate". Vaccine 31 (37): 3872–3878. August 2013. doi:10.1016/j.vaccine.2013.06.062. PMID 23827313. 

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