Preparation and evaluation of a glycerol-preserved direct agglutination antigen for long-term preservation: a comparative study of the detection of anti-Leishmania infantum antibodies in human and dog.
OBJECTIVE
To prepare and evaluate a glycerol-preserved antigen from an Iranian strain of Leishmania infantum (L. infantum) for use in glycerol-preserved direct agglutination tests (GP-DAT) as an alternative to freeze dried direct agglutination tests (FD-DAT) that use freeze-dried antigen.


METHODS
Glycerol-preserved DAT antigen was prepared and stored at different temperatures. We tested antigen stored at 4 °C, 22-37 °C and 50 °C over a period of 365 days. Seven hundred twenty-nine serum samples were collected from different geographical zones of Iran from 2007-2009, and 80 of these samples were pooled to produce sera. Each pooled serum contained 10 sera. All positive and negative pooled sera were separately tested for anti-L. infantum antibodies with GP-DAT, FD-DAT and formaldehyde-fixed direct agglutination test (FF-DAT) antigens; tests were performed on both human and dog sera over a period of 12 months.


RESULTS
There was strong agreement between the results obtained using GP-DAT and FD-DAT antigens stored at 22-37 °C for 12 months for both human (100%) and dog (100%) pooled sera. The direct agglutination test results were highly reproducible (weighted kappa: GP=0.833, FD=0.979 and FF=0.917).


CONCLUSIONS
Because GP-DAT antigen is highly stable over a range of temperatures and is easy to transport in the field, this type of antigen may be particularly useful in areas with endemic visceral leishmaniasis.
Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Behnaz
B
Akhoundi
Mehdi
M
Mohebali
Gholam-Hossein
GH
Edrissian
Mohammad-Bagher
MB
Eslami
Hossein
H
Keshavarz
Hossein
H
Malekafzali
Mohammad-Bagher
MB
Rokni
D000372:Agglutination Tests / Q000379:methods; D000818:Animals; D000913:Antibodies, Protozoan / Q000302:isolation & purification; D000953:Antigens, Protozoan / Q000302:isolation & purification; D003451:Cryoprotective Agents; D004285:Dogs; D005612:Freeze Drying; D005990:Glycerol; D006801:Humans; D007492:Iran; D018314:Leishmania infantum / Q000276:immunology / Q000302:isolation & purification*; D007898:Leishmaniasis, Visceral / Q000175:diagnosis* / Q000453:epidemiology; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods; D013696:Temperature
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D003451:Cryoprotective Agents; D005990:Glycerol