title: CKR-L3, a deletion version CCR6-isoform shows coreceptor-activity for limited human and simian immunodeficiency viruses.
abstract: BACKGROUND
  The chemokine receptors (CKRs), mainly CCR5 and CXCR4 function as major coreceptors in infections caused by human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). Approximately 20 G protein-coupled receptors (GPCRs) have been identified as minor coreceptors, alike CCR6 that we reported recently. Since CKR-L3 is indentified as a natural isoform of CCR6, we attempted in this study to explore the coreceptor function of CKR-L3.
  
  
  METHODS
  NP-2 cells transduced with CD4-receptor (NP-2/CD4) normally remain resistant to HIV or SIV infection. However, the introduction of functional coreceptors can make these cells susceptible to these viruses. NP-2/CD4/CKR-L3 cells were produced to examine the coreceptor activity of CKR-L3. Likely, CCR6-isoform and the major coreceptors, CCR5 and CXCR4 were also examined in parallel. Presence of viral antigen in infected NP-2/CD4/coreceptor cells was detected by indirect immunofluorescence assay (IFA). The results were validated by detection of syncytia, proviral DNA and by measuring reverse transcriptase (RT) activities.
  
  
  RESULTS
  HIV-2MIR and SIVsmE660 were found to infect NP-2/CD4/CKR-L3 cells, indicative of the coreceptor function of CKR-L3. Viral antigens appeared faster in NP-2/CD4/CKR-L3 cells than in NP-2/CD4/CCR6, indicating that CKR-L3 is a more efficient coreceptor. Moreover, syncytia formation was more rapid and RT release evidenced earlier and at higher levels with CKR-L3 than with CCR6. Sequence analysis in the C2-V3 envelope region of HIV-2MIR replicated through CKR-L3 and CCR6 coreceptor showed two and three amino acid substitutions respectively, in the C2 region compared to the CCR5-variant. The SIVsmE660-CKRL3 variant showed three amino acid substitutions in the V1 region, one change in the V2 and two changes in the C2 region. The SIVsmE660-CCR6 variant produced two changes in the V1 region, and three in the C2 region.
  
  
  CONCLUSIONS
  Isoform CKR-L3 exhibited coreceptor activity for limited primary HIV and SIV isolates with better efficiency than the parent CCR6-isoform. Amino acid substitutions in the envelope region of these viruses may confer selective pressure towards CKR-L3-use. CKR-L3 with other minor coreceptors may contribute to HIV and SIV pathogenesis including dissemination, trafficking and latency especially when major coreceptors become compromised. However, further works will be required to determine its clinical significance in HIV and SIV infection.
authors: Department of Virology and Preventive Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. salequl@gmail.com.
authors: Salequl
authors: S
authors: Islam
authors: Katsuaki
authors: K
authors: Kanbe
authors: Nobuaki
authors: N
authors: Shimizu
authors: Takahiro
authors: T
authors: Ohtsuki
authors: Atsushi
authors: A
authors: Jinno-Oue
authors: Atsushi
authors: A
authors: Tanaka
authors: Hiroo
authors: H
authors: Hoshino
mesh_terms: D000818:Animals; D002460:Cell Line; D006678:HIV / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D054399:Receptors, CCR6 / Q000378:metabolism*; D015728:Receptors, HIV / Q000378:metabolism*; D017384:Sequence Deletion; D015302:Simian Immunodeficiency Virus / Q000502:physiology*; D014779:Virus Replication
chemical_list: C106311:CCR6 protein, human; D054399:Receptors, CCR6; D015728:Receptors, HIV