Family: Kitaviridae

Genus: Cilevirus
 

Distinguishing features 

Viruses assigned to the genus Cilevirus form a monophyletic group based on a well-supported maximum likelihood tree inferred from the RNA-directed RNA polymerase (RdRP). Cilevirus genomes are split into two segments. Viruses in the genus cause non-systemic diseases and are persistently transmitted by mites of the genus Brevipalpus.  

Virion

Morphology

Depending on the species, cilevirus virions display spherical, quasi-spherical, or short bacilliform shapes. The bacilliform virions of Citrus leprosis virus C (CiLV-C, Cilevirus leprosis), Citrus leprosis virus C2 (CiLV-C2, Cilevirus colombiaense), passionfruit green spot virus (PfGSV, Cilevirus passiflorae), and Solanum violifolium ring spot virus (SvRSV, Cilevirus solani) measure 40–70 nm in width and 100–120 nm in length (Kitajima et al., 2003, Roy et al., 2013, Ramos-González et al., 2022). In contrast, particles of Hibiscus yellow blotch virus (HYBV, Cilevirus oahuense) are spherical, with an average diameter of 66 nm, and particles of Ligustrum leprosis virus (LigLV, Cilevirus australis) and Ligustrum chlorotic spot virus (LigCSV, Cilevirus ligustri) are quasi-spherical, measuring approximately 40–53 nm in width and 55–65 nm in length (Ramos-González et al., 2022).  

Nucleic acid

The genomes of cileviruses consist of two positive-sense, single-stranded RNA segments. RNA1 ranges from 8.4 to 8.9 kb, whereas RNA2 exhibits greater variability, ranging from 3.5 to 5.0 kb (Locali-Fabris et al., 2006, Roy et al., 2013, Ramos-González et al., 2020, Ramos-González et al., 2022).

Proteins  

Cilevirus virions likely contain a single coat protein of approximately 29 kDa. Particles may additionally include the P24 transmembrane protein and the putative glycoprotein P61.  

Lipids

Cilevirus virions are enveloped by a lipid membrane derived from the host.  

Genome organization and replication

The cilevirus genome consists of two RNA molecules that, based on genomic organization and phylogenetic relationships, can be divided into three subgroups (Ramos-González et al., 2023). Viruses in the subgroup 1 (CiLV-C, CiLV-C2, and PfGSV) have an RNA1 (8.7–8.9 kb) with two ORFs. The largest one codes for the RdRP polyprotein with methyltransferase (Pfam01660), helicase (Pfam01443), RdRP_2 (Pfam00978), UvrD_C_2/FtsJ-like (Pfam01728), and OTU (ovarian tumor family of cysteine proteases) (cd22792) domains. The second ORF encodes the coat protein (P29). RNA2 (4.7–5.0 kb) contains four ORFs (p15, p61, p32, and p24), which encode the proteins P15, P61, P32 and P24. Additional smaller ORFs occur in the intergenic regions between p15 and p61 (Roy et al., 2013, Ramos-González et al., 2020, Ramos-González et al., 2021). ORF p15 is only present in cileviruses of subgroup 1 and although the deduced amino acid sequences are scarcely conserved among members, they share structural similarity with mononegavirus phosphoproteins (Ramos-González et al., 2021). Deduced amino acid sequences of P61 show a signal peptide, multiple transmembrane helices (TMHs) and potential glycosylation sites. P32 is the viral movement protein (3A domain, Pfam00803), and P24 is the homolog of the membrane protein SP24 (Pfam16504). Viruses of subgroup 2, i.e., SvRSV, LigLV, LigCSV, pistachio virus Y (PisVY, Cilevirus pistaciae), and vinca ring spot virus (ViRSV, Cilevirus chilense) exhibit a similar genomic organization to that of subgroup 1 members but lack the 5′-region (1.0–1.5 kb) of RNA2, yielding shorter molecules (3.5–3.6 kb) missing p15 and the p15–p61 intergenic region (Ramos-González et al., 2022). These viruses retain ORFs p61, p32, and p24, and frequently harbour additional small ORFs with predicted TMHs. Subgroup 3, which is solely represented by Hibiscus yellow blotch virus (HYBV), possesses the shortest RNA1 (8.4 kb), which encodes the RdRP, and also contains an overlapping orphan ORF (p10). Cilevirus p29 homolog in HYBV is encoded in the 3′-end of its RNA2. Based on its distinct genome structure, HYBV is referred to as an evolutionary intermediate between cileviruses and higreviruses (Olmedo-Velarde et al., 2021).  

Biology

Most cileviruses have been detected in the Americas (Ramos-González et al., 2023). There are reports of CiLV-C2 detection in Australia (Chao et al., 2025), PisVY in Iran (Mohammadi et al., 2021), and a preliminary, non-confirmed detection of PfGSV in Africa (Munguti et al., 2025). The natural host range of cileviruses comprises trees and herbaceous plants, including economically important crops such as citrus (Citrus spp.) and passion fruit (Passiflora edulis), and numerous ornamental plants, e.g., orchids, hibiscus, etc. (Bastianel et al., 2010, Roy et al., 2015, Ramos-González et al., 2020, León M et al., 2023). Experimentally, cileviruses can infect more than 50 plant species belonging to dozens of families (Garita et al., 2013, Garita et al., 2014, Nunes M.A. et al., 2018). Systemic spread of cileviruses is undetected in either natural or experimental plant hosts. Across the host range, cilevirus infections are limited to local chlorotic or necrotic lesions, sometimes exhibiting ringspot patterns, inside which viruses remain restricted. In citrus, CiLV-C affects leaves, fruits and stems, and may lead to premature dropping of leaves and fruits. Heavy infection can eventually cause the death of trees, particularly when it occurs during early developmental stages (Bastianel et al., 2010). Two lineages of CiLV-C have been identified in citrus orchards: CRD and SJP (Ramos-González et al., 2016). They display contrasting geographic distributions and marked biological differences (Chabi-Jesus et al., 2021, Barro et al., 2026). Plant-to-plant transmission of cileviruses occurs by mite species of the genus Brevipalpus (Acari: Tenuipalpidae) (de Lillo et al., 2021). CiLV-C can be transmitted by more than one species of Brevipalpus mites (Arena et al., 2017). This virus is transmitted by all of the active stages of B. yothersi (Tassi et al., 2017). Cileviruses circulate inside the mite body, and lines of evidence indicate that CiLV-C and CiLV-C2 also propagate in their vectors, B. yothersi (Roy et al., 2015, Ramos-González et al., 2023). Experimentally, CiLV-C can also be transmitted by grafting and mechanical inoculation (Colariccio et al., 1995, Lovisolo et al., 1996).  

Antigenicity

See discussion under family description.  

Species demarcation criteria

The demarcation criteria for species in the genus Cilevirus are based on (1) the extent of the serological relationship as determined by immunodiffusion and/or ELISA, (2) less than 85% aa sequence identity for all ORF encoded proteins, (3) natural host range and, (4) vector species and particularities in the transmission process.