Abstract
BackgroundThe human gastric pathogen Helicobacter pylori is co-evolved with its host and therefore, origins and expansion of multiple populations and sub populations of H. pylori mirror ancient human migrations. Ancestral origins of H. pylori in the vast Indian subcontinent are debatable. It is not clear how different waves of human migrations in South Asia shaped the population structure of H. pylori. We tried to address these issues through mapping genetic origins of present day H. pylori in India and their genomic comparison with hundreds of isolates from different geographic regions.ResultsWe attempted to dissect genetic identity of strains by multilocus sequence typing (MLST) of the 7 housekeeping genes (atpA, efp, ureI, ppa, mutY, trpC, yphC) and phylogeographic analysis of haplotypes using MEGA and NETWORK software while incorporating DNA sequences and genotyping data of whole cag pathogenicity-islands (cagPAI). The distribution of cagPAI genes within these strains was analyzed by using PCR and the geographic type of cagA phosphorylation motif EPIYA was determined by gene sequencing. All the isolates analyzed revealed European ancestry and belonged to H. pylori sub-population, hpEurope. The cagPAI harbored by Indian strains revealed European features upon PCR based analysis and whole PAI sequencing.ConclusionThese observations suggest that H. pylori strains in India share ancestral origins with their European counterparts. Further, non-existence of other sub-populations such as hpAfrica and hpEastAsia, at least in our collection of isolates, suggest that the hpEurope strains enjoyed a special fitness advantage in Indian stomachs to out-compete any endogenous strains. These results also might support hypotheses related to gene flow in India through Indo-Aryans and arrival of Neolithic practices and languages from the Fertile Crescent.
Highlights
The human gastric pathogen Helicobacter pylori is co-evolved with its host and origins and expansion of multiple populations and sub populations of H. pylori mirror ancient human migrations
New genetic models were successfully harnessed based on parasites and pathogens that probably accompanied their human host during evolution and much of the human history including migrations and expansions [2,4,5] in different continents
Overall, based on the multilocus sequence typing (MLST) data (Figure 2) and the cag pathogenicity-islands (cagPAI) patterns (Figure 3), we suggest that H. pylori might have arrived in India probably at the same time when IndoEuropean language speaking people crossed into India (~4000–10,000 years before present)
Summary
The human gastric pathogen Helicobacter pylori is co-evolved with its host and origins and expansion of multiple populations and sub populations of H. pylori mirror ancient human migrations. For some pathogens, such as H. pylori [1,2,3], and JC viruses [4], transmission is faithfully restricted to families within specific communities This phenomenon has in recent times provided evidence regarding patterns of human migration [2,4,5] in different continents. The human gastric pathogen H. pylori is presumed to have co-evolved with its host [6] and established itself in the human stomach possibly millions of years ago [7] It has been recognized recently as a reliable biological marker of host-pathogen co-evolution and ancient human migration based on sequence variation in select gene loci. H. pylori could provide a window into human origins and migration [1,3] and the impact of religions and social systems on stratification of human ethnic groups [12]
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