Detection of Antibodies Directed Towards Japanese Encephalitis Virus by PRNT

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Requisition Forms

Reference Details

Description:

Serological detection of neutralizing antibodies directed towards Japanese encephalitis (JE) virus by Plaque Reduction Neutralization Test (PRNT).

Test Category:
Serology
Pathogen:
Japanese Encephalitis virus (JE)
Laboratory:
Illnesses and Diseases:
  • Japanese encephalitis
Specimen:

Serum. Minimum volume of 250 µl required.

Collection Method:

2 mL screw cap tubes.

Specimen Processing, Storage and Shipping:

Store samples refrigerated until shipped for testing. Ship samples on cold pack, or with wet or dry ice.

Transportation of Dangerous Goods:

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

For additional guidance on the transport of infectious substances in other languages, please click on the link below.

http://www.who.int/ihr/capacity-strengthening/infectious-substances/en/

 

Patient Criteria:

Suspected JEV infection. Submitted samples will first be analysed by the Viral Zoonoses Diagnostic Laboratory by JEV HI to determine if the patient has developed anti-JEV antibodies.  Samples that are reactive can be further analysed for the presence of neutralizing antibodies.  Samples that are HI non-reactive (negative) will not be tested by PRNT.

Accompanying Documentation:

Completed Viral Zoonoses requisition including sender laboratory name, address and telephone number. Patient name and / or identifier (specimen reference number), date of birth, test(s) requested, collection date of specimen, date of on-set of symptoms, and clinical and travel history of patient.

Comments:

This is not a routine test.  Please contact the Viral Zoonoses Diagnostic Laboratory before sending specimens.

Methods and Interpretation of Results:

Antibodies directed against members of the JE serocomplex viruses (dengue, West Nile Virus, etc.) can cross react significantly in some serological assays. The PRNT is a more specific assay and can be used to document the presence of serum antibodies specific for a particular flavivirus.  Serum samples are incubated with virus and if viral neutralizing antibodies are present, they will bind to the virus and prevent viral infection of cultured cells, and hence yield a reduction in the number of plaques detected.  The neutralizing titre of a sample is expressed as the reciprocal of the serum dilution at which there is a 90% reduction in the number of plaques detected.  If the patient has experienced more than one flavivirus infection, cross reactive antibodies may yield uninterpretable results with this assay despite increased specificity.

Due to the cross-reactive nature of flavivirus antibody, the detection of anti-flavivirus IgG (i.e. JE, dengue virus, etc.) in a single serum sample is indicative of past or present exposure to this agent, or a related agent from the same virus genus. The presence of anti-JE virus-specific IgM in a single serum sample is consistent with an acute infection to this virus and meets the criteria for a "probable case". However, a 4 fold rise or greater in neutralizing antibody titre, or an IgG or IgM seroconversion in paired sera, is required to document a "confirmed case" of infection with associated illness.   

There is increasing evidence for IgM persistence in blood/serum for up to a year or more after arbovirus (Eg. members of the Flavivirus, alphavirus, and bunyavirus arthropod borne virus groups) exposure.  Thus, detection of IgM by itself may not always be a confirmation of acute infection.

Isolation of an arbovirus, detection of specific antibody by plaque reduction neutralization assay or detection of nucleic acid by real-time RT-PCR in a clinical specimen would constitute firm evidence of viral association with illness and provide "confirmed case" status.

Turnaround Time:

14 calendar days after the completion of JE virus HI testing.

Contact:
Phone: (204) 789-6097 or (204) 789-2106
Fax: (204) 789-2082
References:
  1. WHO. 2007. Guidelines for plaque reduction neutralization testing of human antibodies to dengue viruses
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