Objective:

To optimize the microneutralization test (MNT) for the detection of neutralizing antibodies against serotype 2 of dengue fever virus (DENV-2) in a Vero-76 cell line.

Materials and methods:

Different cell concentrations were assessed (0.6 X 105 cells/mL, 0.9 X 105 cells/mL, and 1.2 x 105 cells/mL) with 2%, 3%, and 4% fetal bovine serum, virus stock passage number, and incubation days. Viral particles were confirmed using RT-qPCR. DENV-2 disseminated with 5 passages in Vero-76 cells, then, the virus was titrated in 96-well plaques, and two methods for cell infection were evaluated: single layer, and suspended cells. Also, the optimum day for cell staining was determined. Once results were obtained, the following samples were processed using MNT for DENV-2: five sera negative for DENV-2 and yellow fever virus (YFV), five sera negative for antibodies against DENV-2 and positive for antibodies against YFV, and five sera positive for antibodies against DENV-2 that were selected using the plate reduction neutralization test.

Results:

The optimum method for MNT used suspended cells (0.9 X 105 cells/mL), 2% fetal bovine serum, and viral particles at the 5th passage. The minimal dilution able to differentiate a positive sample for DENV2 was 1:40, and the MNT incubation time for DENV-2 was ten days.

Conclusion:

MNT with the cell suspension method and a culture medium with 2% fetal bovine serum allows the detection of IgG neutralizing antibodies against DENV-2 with reliable results, so that larger sample sizes may be assessed, saving materials to be used.

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