Infection with novel respiratory syncytial virus genotype Ontario (ON1) in adult hematopoietic cell transplant recipients, Texas, 2011-2013

Background Respiratory syncytial virus (RSV) can cause severe respiratory disease in adult hematopoietic cell transplant (HCT) recipients. RSV subgroups A and B have evolved into multiple genotypes. We report on a recently described RSV genotype (ON1) in a cohort of adult HCT recipients in Texas. Methods Twenty adult HCT recipients were enrolled as a part of an efficacy trial of ribavirin therapy. RSV identification and genotyping was performed using molecular techniques. RSV-specific neutralizing antibody (NAb) responses were measured. Results ON1 genotype was detected in 3 of 6 patients in the 2011-2012 season and in 8 of 14 patients in 2012-2013 season. Other genotypes detected were NA1 and BA. NAb levels were low at enrollment. Eight of 9 patients who cleared the RSV infection within 2 weeks mounted a 4-fold NAb response, compared with 2 of 8 who shed the virus for >2 weeks. The clinical course of those infected with ON1 was comparable to the course for individuals infected with other genotypes. Conclusion This is the first report of RSV ON1 genotype in the United States, and ON1 genotype was dominant genotype in adult HCT recipients. Interestingly, faster viral clearance was associated with a 4-fold NAb response, likely indicating a reconstituted immune system.