Antigenic characterization of H5N1 highly pathogenic avian influenza viruses isolated from poultry in India, 2006-2015

Abstract

Highly pathogenic avian influenza (HPAI) is a major health concern worldwide. In this study, we focused on antigenic analysis of HPAI H5N1 viruses isolated from poultry in India between 2006 and 2015 comprising 25 isolates from four phylogenetic clades 2.2 (1 isolate), 2.2.2.1 (1 isolate), 2.3.2.1a (17 isolates) and 2.3.2.1c (6 isolates). Seven H5N1 isolates from all four clades were selected for production of chicken antiserum, and antigenic analysis was carried out by hemagglutination inhibition (HI) assay. HI data indicated antigenic divergence (6-21 fold reduction in cross-reactivity) between the two recently emerged clades 2.3.2.1a and 2.3.2.1c. These two clades are highly divergent (21-128 fold reduction in HI titre) from the earlier clades 2.2 /2.2.2.1 isolated in India. However, a maximum of 2-fold and 4-fold reduction in cross-reactivity was observed within the isolates of homologous clades 2.3.2.1c and 2.3.2.1a, respectively. The molecular basis of inter-clade antigenic divergence was examined in the haemagglutinin (HA) antigenic sites of the H5N1 virus. Amino acid changes at 8 HA antigenic sites were observed between clades 2.3.2.1a and 2.3.2.1c, whereas 20-23 substitutions were observed between clades 2.3.2.1a/2.3.2.1c and 2.2/2.2.2.1. Therefore, a systematic analysis of antigenic drift of the contemporary field isolates is a pre-requisite for determining the suitable strain(s) for vaccine candidature.

The Pattern of Highly Pathogenic Avian Influenza H5N1 Outbreaks in South Asia

“…The most commonly detected clade in this region was 2.2. Clade 2.3.2.1a was also common and was identified in India, Bangladesh, Nepal and Bhutan [18][19][20] [18,24]. The co-detection of genetically related avian influenza viruses in human and poultry during the same period suggested that viruses were transmitted from poultry to human in Bangladesh Pakistan and Nepal.…”

“…Though few H5N1 outbreaks were reported after 2014, circulation of H5N1 viruses continues. Findings from surveillance and other studies suggest that both HPAI and LPAI viruses continue to circulate among birds in South Asian countries [20,21,27,30,33,35,37,42,43].…”

“…H5N1 viral clades reported in poultry in South Asian countries, January 2003 to December 2018[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Avian influenza overview September – November 2017

“…The following clades were detected between 2013 and 2017 (Smith et al, 2015;Liu et al, 2016;Marinova-Petkova et al, 2016a;Bhat et al, 2017;El Romeh et al, 2017;Ghafouri et al, 2017a;Rashid et al, 2017;Salaheldin et al, 2017;Shittu et al, 2017 (Torchetti et al, 2015). The following clades were detected between 2013 and 2017 (Smith et al, 2015;Liu et al, 2016;Marinova-Petkova et al, 2016a;Bhat et al, 2017;El Romeh et al, 2017;Ghafouri et al, 2017a;Rashid et al, 2017;Salaheldin et al, 2017;Shittu et al, 2017 (Torchetti et al, 2015).…”

“…Since the first detection of Gs/Gd/96 'Guangdong' lineage of A(H5N1) HPAIV in 1996, the HA of the virus has undergone an extensive evolution with the continuous emergence (and disappearance) of multiple genetic clades. The following clades were detected between 2013 and 2017 (Smith et al, 2015;Liu et al, 2016;Marinova-Petkova et al, 2016a;Bhat et al, 2017;El Romeh et al, 2017;Ghafouri et al, 2017a;Rashid et al, 2017;Salaheldin et al, 2017;Shittu et al, 2017 (Torchetti et al, 2015).…”