Phylogenetic relationships among members of the genus Phlebovirus (Bunyaviridae) based on partial M segment sequence analyses

Viruses in the Phlebovirus genus of the family Bunyaviridae cause clinical syndromes ranging from a short, self-limiting febrile illness to fatal haemorrhagic fever. The genus currently consists of 68 antigenically distinct virus serotypes, most of which have not been genetically characterized. RTPCR with four 'cocktail' primers was performed to amplify a region of the M segment of the genome of 24 phleboviruses included in the sandfly fever Naples, sandfly fever Sicilian and Punta Toro serocomplexes. Partial M segment sequences were successfully obtained and phylogenetic analysis was performed. The three resultant genotypic lineages were consistent with serological data. The sequence divergences were 27.6 % (nucleotide) and 25.7 % (amino acid) within the Sicilian serocomplex, 33.7 % (nucleotide) and 34.4 % (amino acid) within the Naples serocomplex and 35.6 % (nucleotide) and 37.5 % (amino acid) within the Punta Toro serocomplex. Overall, the diversities among viruses of Sicilian, Naples and Punta Toro serocomplexes were 48.2 % and 57.6 % at the nucleotide and amino acid levels, respectively. This high genetic divergence may explain the difficulties in designing a consensus primer pair for the amplification of all the phleboviruses using RT-PCR. It also suggests that infection with one genotype may not completely immunize against infection with all other genotypes in a given serocomplex. These findings have implications for potential vaccine development and may help explain clinical reports of multiple episodes of sandfly fever in the same individual.