Background. Individuals are reinfected with respiratory syncytial virus (RSV) repeatedly. The nature of reinfection, in relation to RSV genetic and antigenic diversity, is ill defined and has implications for persistence and vaccine control. Methods. We examined the molecular relatedness of RSV causing primary and repeat infections, by phylogenetic analysis of the attachment (G) gene in 12 infants from a birth cohort in rural Kenya, using nasal wash samples collected during a 16-month period in 2002-2003, which spanned 2 successive epidemics. Results. Six infants were infected during both epidemics, 4 with RSV-A in the first epidemic followed by RSV-B during the second epidemic and 2 with RSV-A during both epidemics, with no significant G gene sequence variability between samples. Two infants were infected and reinfected with different RSV-A strains during the same epidemic. Possible viral persistence was suspected in the remaining 4 infants, although reinfection with the same variant cannot be excluded. Conclusions. These are the first data that specifically address strain-specific reinfections in infancy in relation to the primary infecting variant. The data strongly suggest that, following primary infection, some infants lose strain-specific immunity within 7-9 months (between epidemics) and group-specific immunity within 2-4 months (during an epidemic period).
Bibliographical noteFunding Information:
Received 12 April 2005; accepted 18 July 2005; electronically published 17 November 2005. Potential conflicts of interest: none reported. Presented in part: Research in Progress Short Presentations and Posters, Royal Society of Tropical Medicine and Hygiene, London, UK, 10 December 2004. Financial support: Wellcome Trust United Kingdom (grant 061584). The manuscript is published with the permission of the Director of the Kenya Medical Research Institute. a Present affiliation: Department of Biological Science, The University of Warwick, Coventry, UK Correspondence: Dr. Paul D. Scott, Dept. of Biological Science, The University of Warwick, Gibbet Hill Rd., Coventry, UK (P.D.Scott@warwick.ac.uk).