A cluster of patients with recombinant B/F HIV-1 infection: Epidemiological, clinical, and virological aspects

Migratory processes have caused changes in human immunodeficiency virus (HIV) epidemiology and non-B subtypes are now playing an increasing role. In a cohort of 553 HIV-infected outpatients tested to identify non-B isolates, the largest group consisted of 13 subjects with a recombinant B/F form (prevalence 2.4%). Sequencing and phylogenetic analyses described a B/F recombinant clade with anomalous breakpoints that did not allow it to be classified as CRF12-BF. Viral load was not quantified efficiently because of a mismatch in the primers and probes used by commercial assays. An assessment of the clinical management, and epidemiological, immunological, and virological characteristics of these patients, who were receiving non-nucleoside reverse transcriptase inhibitor (NNRTI)- or protease inhibitor (PI)-based regimens, showed that the immunological and virological mismatch delayed the start of treatment by a mean of 6.8 months. Therapy was started in nine patients. Both NNRTI- and PI-based regimens led to full virological suppression after a mean 36 weeks of treatment; the PI-based regimens proved to be more effective in terms of immunological recovery (1,341 vs. 544 CD4+ cells/mm 3). The spread of non-B subtypes is increasing throughout the world but their response to treatment is still unclear. PIs and NNRTIs are effective but further tests are needed to allow the more efficient recognition of these viral strains and establish how they should be treated.