A novel strain of Leishmania braziliensis harbors not a toti- but a bunyavirus

Abstract

Leishmania is a genus of the family Trypanosomatidae that unites obligatory parasitic flagellates causing a variety of vector-borne diseases collectively called leishmaniasis. The symptoms range from relatively innocuous skin lesions to complete failures of visceral organs. The disease is exacerbated if a parasite harbors Leishmania RNA viruses (LRVs) of the family Pseudototiviridae. Screening a novel isolate of L. braziliensis, we revealed that it possesses not a toti-, but a bunyavirus of the family Leishbuviridae. To the best of our knowledge, this is a very first discovery of a bunyavirus infecting a representative of the Leishmania subgenus Viannia. We suggest that these viruses may serve as potential factors of virulence in American leishmaniasis and encourage researchers to test leishmanial strains for the presence of not only LRVs, but also other RNA viruses.

Fig 1. Clinical manifestation of cutaneous leishmaniasis caused by L. braziliensis BO17.

Fig 2. Phylogenetic networks of L. (Viannia) based on genome-wide SNPs.

Upper panel depicts the relationships at the subgenus level and the lower panel provides the closer view on the clade (highlighted in yellow) containing the BO17 isolate that is shown in magenta. The double-crossed branch is at 50% of its length. The scale bar denotes the number of substitutions per site.

Fig 3. LbrLBV1 of L. braziliensis BO17.

(A) Agarose gel visualization of BO17 dsRNA. Leishmania guyanensis dsRNA was used as a positive control. GeneRuler 1kb DNA Ladder was added as size reference. (B) Representation of LbrLBV1 genomic segments (drawn to scale). Directional shapes depict predicted ORFs with the lengths of encoded proteins displayed inside. Terminal repeats are shown in callouts.

Fig 4. Phylogenetic tree of Leishbuviridae based on the RDRP amino acid sequences.

The tree was rooted on Phenuiviridae (collapsed for better visibility). LbrLBV1 is highlighted in black. Numbers at nodes are standard bootstrap supports/Bayesian posterior probabilities, circles indicate support of 100/1.

Fig 5. Growth curves and viral load of L. braziliensis BO17.

(A) Growth curves of the WT, LBV(-) 1, and LBV(-) 2 cultures. Data are calculated from three independent biological replicates. (B) Viral load in the WT culture analyzed by quantitative RT–PCR of RdRP mRNA. Data are summarized from three independent biological replicates, each with three technical replicates. Error bars indicate standard deviation.