What Are Circulating Recombinant Forms?

Circulating Recombinant Forms (CRFs) are new strains of the HIV virus. When two different subtypes conglomerate in a body cell, the unity is considered to be a new hybrid virus. If this new virus successfully infects more than one person, then it is taken to be a circulating recombinant form. CRFs typically do not survive for long periods of time. They can, however, substantially influence the immune system of an infected person.

Regional Influence

• CRFs are typically found in certain geographical regions. The most widespread combinations are subtypes A and C. While CRF A/C is common in most areas affected by HIV/AIDS, individuals are increasingly exposed to subtypes that are not native to their region or country. Subtype B, for example, has been the most common CRF in Europe, South and North America, Japan, and Australia. While the CRF is still the most common subtype, new strains have been discovered in these regions and account for at least 25 percent of new HIV cases in Europe.

An Example -- CRF01_AE and Subtype I

• CRF 01_AE or A/E is traditionally thought to be a combination of subtype A and E. Evidence of such hybridization, however, has not been provided and many individuals refer to CRF A/E as subtype E. Subtype I originated in Cyprus. The strain was later found to have traces of Subtype A and G, and was reclassified as CRF A/G/I. Some field professionals now believe that CRF A/G/I is more complex, being comprised of more than three subtypes.

Disease Progression

• Disease progression between CRFs and HIV-1 is uncertain. Although individuals who contract CRFs are at risk of contracting HIV-1, it is not certain that those who have CRFs present in the cell body will later develop the HIV virus. Scientists have, however, conducted several studies that favor the idea of CRFs leading to the virus. A study presented in 2006, for example, showed that individuals in Uganda infected with recombinant strains developed AIDS and eventually died without rapid treatment.

The Future of CRFs

• The future of CRFs is vast. Many scientists believe that new recombinant forms will be discovered in the near and distant future as subtypes continue to combine within cell bodies. It is also believed that current CRFs will continue to populate various regions throughout the world. As new CRFs are found and circulate, mutation of the HIV virus will continue to occur.