Anti-Human T-Lymphotropic Virus type 1 (HTLV-1) neutralizing antibodies detection by inhibition syncytium formation assay.

GÓMEZ L; BALANGERO M; MORÓN G; BRITOS F; MANGEAUD A; MATURANO E; GALLEGO S

Simposio; III International Clinical Virology Symposium and Advances in Vaccines; 2010

Background and Aims: The syncytium inhibition assay is based on the fusogenic properties of envelope proteins of human retroviruses. We implemented and standardized an inhibition syncytium formation assay for detection and quantification of neutralizing antibodies against HTLV-1 in three groups of infected people: Asymptomatic (ASS), Oligosymptomatic (OLIGO) and patients with neurological disease (TSP/HAM), and differences between them were analyzed.  Methods: Sera of 47 HTLV-1 infected Argentinean subjects (10 TSP/HAM, 17 ASS and 20 OLIGO) were collected. To implement the inhibition syncytium formation assay, we based on the assay described by Sundaram 2004, et al. and did some modifications. The system uses MT-2 (HTLV-1) cells, cells transfected with the gene LacZ under the control of the sequence LTR of HIV (Hela CD4 + LTR Lac Z) and cell lines transfected with the tat gene of HIV (Dunni-tat o Cos-tat o RD-tat). The standarized assay was used for quantifing neutralizing antibodies in serial 5 and 10-fold dilutions of sera samples from asymptomatics and patients with neurological diseases/HTLV-1. Statical analysis was done using Kruskal-Wallis test, Levene homogeneity of variances test and Spearman correlation analysis. Results: We standardized conditions for performing this assay. Neutralizing antibody titers against HTLV-1 virus in different groups were found in a range between 1/50 and 1/4000. A high percentage of these samples (55.4%, N=26) had high titers of neutralizing antibodies (between 500-1000). There were no significant differences in antibodies titers between symptomatic and asymptomatic groups and no correlation between these titers and the number of pyramidal signs/symptoms were found. Conclusions: In this study we demonstrate no significant differences in neutralizing antibody titers between symptomatic and asymptomatic individuals. These results corroborate that neutralizing antibodies generated in vivo would not be protective for the development of TSP/HAM and suggest that their role in the pathogenesis of TSP is also unlikely. The inhibition syncytium formation assay implemented is a very useful tool that can be used in future studies of pathogenesis, viral tropism and the development of neutralizing antibodies against HTLV-1.