Current Trends of HIV Recombination Worldwide

Abstract

One of the major characteristics of HIV-1 is its high genetic variability and extensive heterogeneity. This characteristic is due to its molecular traits, which in turn allows it to vary, recombine, and diversify at a high frequency. As such, it generates complex molecular forms, termed recombinants, which evade the human immune system and so survive. There is no sequence constraint to the recombination pattern as it appears to occur at inter-group (between groups M and O), as well as interand intra-subtype within group M. Rapid emergence and active global transmission of HIV-1 recombinants, known as circulating recombinant forms (CRFs) and unique recombinant forms (URFs), requires urgent attention. To date, 55 CRFs have been reported around the world. The first CRF01_AE originated from Central Africa but spread widely in Asia. The most recent CRF; CRF55_01B is a recombinant form of CRF01_AE and subtype B, although its origin is yet to be publicly disclosed. HIV-1 recombination is an ongoing event and plays an indispensable role in HIV epidemics in different regions. Africa, Asia and South America are identified as recombination hot-spots. They are affected by continual emergence and cocirculation of newly emerging CRFs and URFs, which are now responsible for almost 20% of HIV-1 infections worldwide. Better understanding of recombinants is necessary to determine their biological and molecular attributes.

Keywords: HIV; current trends.

Figure 1.

Worldwide distribution of HIV-1 recombinant forms. (A) Frequency of recombinant forms that contributed towards total HIV infections as of the year 2012. (B) Frequency of different recombinant forms that contributed towards 55 CRFs identified to date.

Figure 2.

Circulating recombinant forms (CRFs) of HIV-1 identified globally in the past 20 years. (A) Cumulative number of CRFs reported yearly in major geographical regions (Africa, Asia, South America) and globally (Overall). (B) Cumulative percentage of novel HIV-1 CRFs discovered from 1993 to 2012. In all geographical regions and overall, marked increase in the percentage of newly discovered CRFs was observed in the last 10 years (years 2003-2012). Data were extracted from the Los Alamos HIV Database. CRF5501B was excluded from this analysis since data related to this CRF is not publicly available.