In silico segmentations of lentivirus envelope sequences

Our models yield clear and accurate delimitations of the C/V regions, when the test set and the training set were made up of sequences of the same lentivirus, but also when they were made up of sequences of different lentiviruses. Interestingly, the models predicted the different regions of lentiviruses such as the bovine and feline lentiviruses, not used in the training set. Models based on composite training sets produce accurate segmentations of sequences of all these lentiviruses.Our results suggest that each C/V region has a specific statistical oligonucleotide composition, and that the C (respectively V) regions of one of these lentiviruses are statistically more similar to the C (respectively V) regions of the other lentiviruses, than to the V (respectively C) regions of the same lentivirus.Retroviruses are RNA viruses infecting vertebrates and many non vertebrates. Virus particles are spherical and surrounded by an envelope. Their viral replication is dependent of the RT (Reverse Transcriptase), a viral RNA-dependent DNA-polymerase. The lentivirus genus is part of the retrovirus family. Lentiviruses infect animals and humans and cause slowly progressing diseases. Among the lentivirus genus, HIV-1 and HIV-2 (Human Immunodeficiency Virus type 1 and 2) infect humans, EIAV (Equine Infectious Anemia Virus) infects equids, SRLV (Small Ruminant LentiVirus) infects goats and sheep, SIV (Simian Immunodeficiency Virus) infects non primate monkeys, BIV (Bovine Immunodeficiency Virus) infects bovines and FIV (Feline Immunodeficiency Virus) infects felines.The considerable plasticity of the genome of lentiviruses is quite obvious in the env gene, encoding the envelope, particularly in the region encoding the surface (SU) glycoprotein forming spikes. Causes of this plasticity are, among other factors, the low fidelity of the viral reverse transcriptase (RT) during the retrotranscription of the viral RNA genome into DNA, the lack of proofreading activity of the RT, the hig