Abstract
ObjectiveTo investigate the geographical origin and evolution dynamics of HIV-1 subtype C infection in India.DesignNinety HIV-1 subtype C env gp120 subtype C sequences from India were compared with 312 env gp120 reference subtype C sequences from 27 different countries obtained from Los Alamos HIV database. All the HIV-1 subtype C env gp120 sequences from India were used for the geographical origin analysis and 61 subtype C env gp120 sequences with known sampling year (from 1991 to 2008) were employed to determine the origin of HIV infection in India.MethodsPhylogenetic analysis of HIV-1 env sequences was used to investigate the geographical origin and tMRCA of Indian HIV-1 subtype C. Evolutionary parameters including origin date and demographic growth patterns of Indian subtype C were estimated using a Bayesian coalescent-based approach under relaxed molecular clock models.FindingsThe majority of the analyzed Indian and South African HIV-1 subtype C sequences formed a single monophyletic cluster. The most recent common ancestor date was calculated to be 1975.56 (95% HPD, 1968.78–1981.52). Reconstruction of the effective population size revealed three phases of epidemic growth: an initial slow growth, followed by exponential growth, and then a plateau phase approaching present time. Stabilization of the epidemic growth phase correlated with the foundation of National AIDS Control Organization in India.InterpretationIndian subtype C originated from a single South African lineage in the middle of 1970s. The current study emphasizes not only the utility of HIV-1 sequence data for epidemiological studies but more notably highlights the effectiveness of community or government intervention strategies in controlling the trend of the epidemic.
Highlights
The first AIDS case in India was detected in 1986 among sex workers in Chennai, Tamil Nadu [1], and since HIV-1 infection has been reported in all of the states and union territories in India
Genetic analyses of HIV-1 circulating in different parts of India have shown that the predominant proportion of HIV-1 circulating in India is of subtype C origin with a small fraction made up of subtypes A and B [2,3,4,5,6,7,8]
The fact that HIV-1 isolated from different parts of India at different times are closely related [6] suggests that the preponderance of subtype C viruses over other subtypes is most probably not due to continual introductions of HIV-1 subtype C into the country, recent immigration, or representative of a cluster of isolated individuals
Summary
The first AIDS case in India was detected in 1986 among sex workers in Chennai, Tamil Nadu [1], and since HIV-1 infection has been reported in all of the states and union territories in India. According to the UNAIDS 2010 report, India – which has a population of about 1.1 billion, has approximately 2.4 million people living with HIV-1. This makes India one of the largest HIV-1 infected populations in the world. HIV-1 subtype C sequences from different parts of India were more closely related to each other than to subtype C sequences from other regions [6]. These results indicate that subtype C sequences in India are distinct from subtype C sequences sampled from other countries. Revealing the geographic origin, date of origin, and evolutionary history of HIV-1 in this region would provide valuable insight regarding the epidemic in India
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