[Biological properties of virus dengue-3 strains isolated during the epidemic ocurred in Havana, 2001-2002].

Introduction: During dengue epidemics in Cuba, an increase in clinical severity with the epidemics progression in time, particularly in secondary infections, have been frequently observed. It is considered that this increase could be related with genetic changes in the circulating virus.

Objective: To study some biological attributes related to strains isolated at different points of time during the dengue epidemic occurred in Havana city, 2001-2002.

Methods: Nine DENV-3 strains were studied. Cytopathogenic effect, viral growth in C6/36 HT and Vero cell lines, viral plaque sizes, temperature sensitivity, neurovirulence in newborn mice and pH influence in the binding of the virus and the cell as well as in the multiplication medium were evaluated.

Results: DENV-3 strains were more cytopathogenic in Vero Cells. However, higher titres were obtained in C6/36 HT cells. All the strains showed reduction of viral titres and plaque size with temperature increasing and low neurovirulence. Basic pH favoured virus-cell binding whereas acid pH was only permissive for some strains isolated at the end of the epidemic. On the other hand, at pH 6.5-7, the viral multiplication medium favoured the growth of strains isolated at the beginning of the epidemic whereas the growth of those isolated at the endof the epidemic was noticeable at pH 7-8.

Conclusions: This study proved the phenotypical changes among strains isolated at different points of time in the epidemic. They might be related to differences in viral fitness or in virulent potential. Nevertheless, some of the studied biological properties suggest that dengue virus-3 strains are less virulent than the Cuban dengue virus 2 strains isolated in 1997.