Molecular Characterization of the Haemagglutinin-Neuraminidase Gene of Human Parainfluenza Virus Type-1 Isolated from Infants Aged 6-36 Months attending Mbagathi District Hospital Nairobi Kenya 2006-2010

Abstract

Human parainfluenza virus type 1 (HPIV-1), a Paramyxovirus, is a leading cause of paediatric respiratory hospitalizations globally. Currently, there is no clinically successful vaccine against HPIV-1. Hence, there is need to characterize circulating strains of this virus in order to establish and develop a feasible and efficacious vaccine against the virus. The variable HPIV-1 Hemagglutin-Neuraminidase (HN) protein is found in the envelope of HPIV-1 where it initiates the infection process by binding to cellular receptors. HN is also the major antigen against which the human immune response is directed against. This study focused on identifying mutations in the HN gene that would be useful in understanding evolution of HPIV-1. Twenty five HPIV-1 isolates were obtained after screening nasopharyngeal samples from patients with influenza-like-illness attending Mbagathi District Hospital in Nairobi from June 2006 to December 2010. RT-PCR was carried out on the isolates using HN-specific primers to amplify 360nt in the most polymorphic region and the amplicons sequenced. Genomic data was analysed using a suite of bioinformatics software. Forty-eight polymorphic sites with a total of 55 mutations were identified at the nucleotide level and 47 mutations at 23 positions at the amino acid level. No positively selected sites were found in the HN protein. The data from the analysis of 21 isolates suggests that the HN gene which is the major antigenic target is under purifying (negative) selection.