DRUG RESISTANCE MUTATIONS AND TRANSMISSION CLUSTERS OF THE HIV-1 CRF01_AE SUB-EPIDEMIC IN BULGARIA

Background. In Bulgaria the second most predominant HIV-1 strain after subtype B is CRF01_AE. Material and Methods. 270 HIV-1 polymerase (pol) CRF01_AE sequences collected between 1995–2019 were analyzed with the phylogenetic approach. To identify transmission clusters, we used two different genetic distance thresholds (d), i. e. 1.5% and 0.5%. Results. Genetic distance d=1.5% defined more distant infections in a huge cluster of 154 sequences composed mostly of people, who inject drugs (PWID), whereas when (d) was reduced to 0.5%, we determined more recent transmissions and the large cluster disintegrated into smaller ones. Different drug resistance mutations (DRM) were detected in patient’s HIV-1 pol sequences and were most common in male heterosexual (HET) single sequences. Conclusions. Our data showed repeated introduction of CRF01_AE in Bulgaria and rapid spread of the infection among PWID groups. Molecular monitoring of the epidemic among PWID communities could help reduce the spread of HIV-1 infection.