Genetic and antigenic characterization of influenza A(H3N2) in Cameroon during the 2014-2016 influenza seasons

Abstract

The first outbreak of influenza A(H3N2) occurred in 1968 and caused the third flu pandemic of the 20th century. It has affected multiple countries over time. The best strategy to reduce the burden of influenza is through vaccination whose efficacy varies with respect to the circulating strains. This study was performed to better understand the molecular evolution of influenza A(H3N2) and assess vaccine efficacy in Cameroon. Complete sequences of three gene segments were obtained from 2014 to 2016 influenza seasons in Cameroon. Hemagglutinin (HA), Neuraminidase (NA) and matrix (M) genes of 35 A(H3N2) virus strains were amplified and sequenced. Predicted vaccine efficacy was measured using the Pepitope model. Phylogenetic analysis of the HA gene showed that all Cameroonian strains had evolved away from the 3C.1-A/Texas/50/2012-like clade. Globally, 2014 virus strains clustered with the 2015–2016 vaccine strain, 3C.3a-A/Switzerland/9715293/2013, whereas 2015 and 2016 virus strains clustered with the 2016–2017 vaccine strain, 3C.2a-A/HongKong/4801/2014. In order to determine the genotypic drug susceptibility to neuraminidase inhibitors and amantadine, the NA and M2 protein coding sequences were analyzed. There was no strain with characteristic mutation for resistance to neuraminidase inhibitors, per contra; all strains possessed the substitution S31N, peculiar of resistance to adamantanes. There was drift in influenza A(H3N2) dominant epitopes B (2014 and 2015) to epitopes A (2016) with a theoretical efficiency in vaccine ranging from low to moderate. The presence of several antigenic site mutations among H3N2 virus strains between 2014–2016 influenza seasons in Cameroon confirms the progressing evolution of circulating H3N2 strains.

Genetic diversity of influenza A(H3N2) viruses in Northern Cameroon during the 2014‐2016 influenza seasons

“…It is important to perform molecular analyses of influenza viruses to detect antigenic drift of viruses, viruses with increased virulence or viruses with resistance to antivirals. A previous study performed molecular characterization of influenza A(H3N2) from sentinel sites in the Southern regions of Cameroon and confirmed the progressing evolution of influenza A(H3N2) viruses in Cameroon. We report here the genome characterization of influenza A(H3N2) from the Northern region of Cameroon characterized by a Sudan tropical climate, with high temperatures …”

“…Amplification of the HA, NA and M gene fragments was performed in two steps to obtain two overlapping fragments as previously described by Monamele et al A reaction volume of 25μl contained a final concentration of 1x PCR buffer, 0.2μM of each primer, 0.19U/μL RNasin, 0.5μl of Superscript RT/Platinum Taq enzyme and 5μl of RNA. S1 Table gives the cycling conditions for amplification of the HA, NA and M genes.…”

Genetic characterization of influenza B virus in Cameroon and high frequency of reassortant strains

“…Respiratory samples, as well as clinical and demographic data, were collected from data of the surveillance activity at the CPC between January 2014 and June 2017. Nasopharyngeal swabs and/or oropharyngeal swabs were collected from outpatients that met the WHO case definition of influenza-like illness (ILI), or from inpatients with severe acute respiratory infection (SARI) as previously described 16 Step RT-PCR Kit (Life Technologies Corporation, Carlsbad, CA). The samples diagnosed for type B influenza virus with threshold cycles above 30 were not qualified for sequencing.…”

Genetic characterization of influenza A(H3N2) viruses circulating in coastal Kenya, 2009‐2017

“…Kilifi between 2009 and 2017 using full-length HA sequences. The presence of several antigenic site mutations among A(H3N2) virus strains circulating between 2009 and 17 influenza seasons confirms the continuing evolution of circulating strains in Kilifi, Kenya.Most of the amino acid variations associated with the continuing evolution of A(H3N2) viruses in Kilifi, Kenya have also been reported in other A(H3N2) viruses isolated in Africa, for example, in Cameroon36 and Mozambique,37 and in Asia, for example, in Thailand 38. Thus, the continuing evolution of A(H3N2) in Kilifi is inF I G U R E 3 A maximum likelihood phylogenetic tree of the HA gene segment for 66 KHDSS outpatient influenza A(H3N2) virus specimens collected from influenza surveillance in coastal Kenya, 2015-17.…”