Identification of a novel HIV-1 complex circulating recombinant form (CRF18_cpx) of Central African origin in Cuba

Background: Analysis of partial pol and env sequences have indicated a high diversity of HIV-1 genetic forms in Cuba, including two potential novel circulating recombinant forms (CRF): U-pol/H-env and D-pol/A(env). Objectives: To determine whether U-pol/H-env recombinant viruses from Cuba, detected in 7% of samples, represent a novel HIV-1 CRF, and to identify non-Cuban viruses related to this recombinant form. Methods: Near full-length genome amplification was carried out by nested polymerase chain reaction in four overlapping DNA segments of two epidemiologically unlinked viruses in uncultured peripheral blood mononuclear cells. The sequences were analysed phylogenetically. Recombinant structures and phylogenetic relationships were analysed by bootscanning and by maximum likelihood. Searches for related viruses in databases were initially based on sequence homology and sharing of signature nucleotides. Results: Both Cuban viruses clustered uniformly in bootscans all along the genome with each other and with a virus from Cameroon, CM53379, indicating that all three represent the same recombinant form. Their genome comprised multiple segments clustering with subtypes A1, F, G, H and K, as well as segments failing to cluster with recognized subtypes. The newly defined CRF, designated CRF18_cpx, was phylogenetically related in partial segments to CRF13_cpx, CRF04_cpx and 36 additional viruses, most of them from Central Africa. One of the viruses from Cameroon, sequenced in the near full-length genome, was a CRF18_cpx/subtype G secondary recombinant. Conclusions: A novel HIV-1 complex circulating recombinant form (CRF18_cpx) has been identified that is circulating in Cuba and Central Africa. (c) 2005 Lippincott Williams & Wilkins.