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Topic Name: Researchers provide emergence of Recombinant forms of HIV: Dynamics and Scaling

Category: Genetic Engineering

Research persons: Suryavanshi ,Narendra Dixit

Location: Indian Institute of Science, Bangalore, India

Details

The emergence of drug resistant forms of HIV often underlies the failure of current antiretroviral therapies for HIV infection. Specific mutations in the HIV genome confer resistance to individual drugs. sexual reproduction, a process similar to sexual reproduction in higher organisms, can accelerate the accumulation of resistance mutations by mixing the contents of distinct viral genomes and expedite the failure of therapy. The dynamics of the emergence of recombinant forms of HIV in infected individuals remains poorly understood.

In a study publishing in PLoS Computational Biology on October 26, 2007, researchers Suryavanshi and Dixit from the Indian Institute of Science, Bangalore, India present a new model of HIV dynamics that provides a detailed account of the emergence and growth of recombinant forms of HIV following infection with diverse viral genomes. Analysis of experimental data using the model establishes the high rate of HIV recombination and elucidates the origins of scaling relationships that link the relative prevalence of recombinant forms of HIV to the overall extent of infection. The model provides a framework for predicting the development of multi-drug resistance in HIV patients.

This work was supported by US National Institutes of Health.

Note for Sexual reproduction

Sexual reproduction is a union that results in increasing genetic diversity of the offspring. It is characterized by two processes: meiosis, involving the halving of the number of chromosomes; and fertilisation, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve genetic recombination.

The evolution of sex is a major puzzle. The first fossilized evidence of sexually reproducing organisms is from eukaryotes of the Stenian period, about 1.2 to 1 billion years ago. Sexual reproduction is the primary method of reproduction for the vast majority of visible organisms, including almost all animals and plants. Bacterial conjugation, the transfer of DNA between two bacteria, is often mistakenly confused with sexual reproduction, because the mechanics are similar.

A major question is why sexual reproduction persists when parthenogenesis appears in some ways to be a superior form of reproduction. Contemporary evolutionary thought proposes some explanations. It may be due to selection pressure on the clade itself—the ability for a population to radiate more rapidly due to a changing environment through sexual recombination than parthenogenesis allows. Alternatively, sexual reproduction may allow for the 'ratcheting' of evolutionary speed as one clade competes with another for a limited resource.

Note for Genetic recombination

Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. In eukaryotes recombination commonly occurs during meiosis as chromosomal crossover between paired chromosomes. This process leads to offspring having different combinations of genes from their parents and can produce new chimeric alleles. In evolutionary biology this shuffling of genes is thought to have many advantages, including that of allowing sexually reproducing organisms to avoid Muller's ratchet. However, a recombination pathway in DNA is any way by which a broken DNA molecule is reconnected to form a whole DNA strand.

In molecular biology "recombination" can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA.

Enzymes called recombinases catalyze natural recombination reactions. RecA, the recombinase found in E. coli, is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other eukaryotic organisms there are two recombinases required for repairing DSBs. The RAD51 protein is required for mitotic and meiotic recombination and the DMC1 protein is specific to meiotic recombination.

About National Institutes of Health

The National Institutes of Health (NIH) is an agency of the United States Department of Health and Human Services and is the primary agency of the United States government responsible for biomedical research.

The Institutes are responsible for 28%—about $28 billion—of the total biomedical research funding spent annually in the U.S., with most of the rest coming from industry. The NIH is divided into two parts: the "Extramural" parts of NIH are responsible for the funding of biomedical research outside of NIH, while the "Intramural" parts of NIH conduct research. Intramural research is primarily conducted at the main campus in Bethesda in unincorporated Montgomery County, Maryland, and the surrounding communities. The National Institute of Aging and the National Institute on Drug Abuse are located in Baltimore, Maryland, and the National Institute of Environmental Health Sciences is in Research Triangle, North Carolina. The NIAID maintains Rocky Mountain Labs in Hamilton, Montana, with an emphasis on virology.

The predecessor of the NIH began in 1887 as the Laboratory of Hygiene. It grew and was reorganized in 1930 by the Ransdell Act into the National Institute of Health (singular at the time). Today it is one of the world's foremost medical research centers, and the Federal focal point for medical research in the U.S. The NIH, comprising 27 separate institutes, centers and the Office of the Director, is part of the United States Department of Health and Human Services. The current NIH Director is Elias Zerhouni.

The goal of NIH research is to acquire new knowledge to help prevent, detect, diagnose, and treat disease and disability, from the rarest genetic disorder to the common cold. The NIH mission is to uncover new knowledge that will lead to better health for everyone. NIH works toward that mission by: conducting research in its own laboratories; supporting the research of non-Federal scientists in universities, medical schools, hospitals, and research institutions throughout the country and abroad; helping in the training of research investigators; and fostering communication of medical and health sciences information.

CONTACT: 

Narendra Dixit 
Department of Chemical Engineering 
Indian Institute of Science 
Bangalore, India - 560012 
Phone: +91-80-2293-2768 
E-Mail: narendra@chemeng.iisc.ernet.in