Natural infection and immune response to parvovirus B19

The natural course of parvovirus B19 infection has been evaluated by experimental infection of normal volunteers and in a prospective study of a major epidemic. After intranasal inoculation of normal per sons, the virus infects and replicates in erythroid bone marrow cells. Viremia is first detected by day 6 and can reach peak levels >1014ml 1 serum. Infection kills the host cells, so that at the peak of infection, almost no erythroid cells except for a few virtually pathognomonic giant pronormoblasts can be detected in a bone marrow aspirate. Specific immunoglobulin M (IgM) followed by IgG antibodies appear during the second week postinoculation and effectively terminate the infection.

Antibody to parvovirus can be detected using indirect capture immunoassays employing genetically engineered capsid preparations for antigen. Capture techniques to detect viral antigen in sera have been supplanted by DNA hybridization using either i2P labeled or biotinylated DNA or RNA probes. The most sensitive technique for detection of virus is DNA amplification by polymerase chain reaction. Small amounts of viral DNA can be detected for many weeks after acute infection; the biological significance of this finding is unknown.

IgM antibody is usually present in the first specimen obtained after the onset of illness: in one study, 78% of sera were positive 0-2 days and 93% were positive 3-7 days after the onset of symptoms. The peak in IgM titer occurs at 2-3 weeks and IgM has been detected in sera obtained months after the onset of symptoms. Specific IgG antibodies can be demonstrated in 42% of persons at 0-2 days and in 90% at 3-7 days.

VP2 is the primary target of antibodies induced by first exposure to the virus. As the antibody response matures, specificity against VP1 epitopes develops. Linear epitopes, clustered in the VP 1-unique region, are essential for an effective, neutralizing immune response. Using standard dot blot analysis, virus is rarely detected in sera beyond day 15 after inoculation, but when evaluated by polymerase chain reaction, low level viremia can still be demonstrated in some patients for more than 2 months after natural infection.

IgG antibodies persist for life in most individuals, probably boosted with re-exposure. Anti-B19 IgG has been found in 36% of children by the age of 10, in 50-60% of adults aged 16-40 and more than 85% in individuals more than 70 years old. BI9 infections occur worldwide and throughout the year, with a seasonal peak in spring. They frequently occur in epidemics of about 3 year periodicity, but also as sporadic cases. B19 parvovirus is probably transmitted by the respiratory route. High levels of virus in saliva and heat stability of the virus combine to make parvovirus infection very contagious. B19 has also been transmitted by blood products and seems to resist pasteurization and solvent detergent treatment.

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Responses

  • Antonino
    How to make immune system kill parvovirus b19?
    1 year ago
  • Teemu
    Can immunity against parvovirus be obtained after infection?
    8 months ago

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