Long-term nonprogressor

Long-term nonprogressors (LTNPs), individuals who are infected with HIV, but maintain a CD4 count greater than 500 without antiretroviral therapy with a detectable viral load.^[1] Many of these patients have been HIV positive for 30 years without progressing to the point of needing to take medication in order not to develop AIDS. They have been the subject of a great deal of research, since an understanding of their ability to control HIV infection may lead to the development of immune therapies or a therapeutic vaccine.^[2] The classification "Long-term non-progressor" is not permanent, because some patients in this category have gone on to develop AIDS.

Long-term nonprogressors typically have viral loads under 10,000 copies RNA/ml blood,^[3] do not take antiretrovirals, and have CD4+ counts within the normal range.^[4] Most people with HIV not on medication have viral loads which are much higher.

It is estimated that around 1 in 300 people with HIV are long-term nonprogressors.^[5] Without the symptoms of AIDS, many LTNP patients may not know they are infected.^[6]

Genetic traits that confer greater resistance or more robust immune response to HIV are thought to explain why LTNP patients are able to live much longer with HIV than patients who are not LTNP.^[7][8] Some LTNP are infected with a weakened or inactive form of HIV, but it is now known that many LTNP patients carry a fully virulent form of the virus. Genetic traits that may affect progression include:

• Gene mutation. A mutation in the FUT2 gene affects the progression of HIV-1 infection.^[9] 20% of Europeans who have that mutation are called "non secretor" because of their absence of a certain type of antigen that also provides strong resistance against norovirus.^[9][10]
• Mitochondrial DNA. Different mitochondrial DNA haplotypes in humans may increase or decrease rates of AIDS progression. Haplotypes associated with more loosely coupled mitochondrial respiration, with reduced ATP and ROS generation, have been associated with faster progression and vice versa.^[11]
• Receptor mutations. A low percentage of long-term nonprogressors have been shown to have inherited mutations of the CCR5 receptor of T cell lymphocytes. HIV uses CCR5 to enter these cells. It is believed that the Δ32 (delta 32) variant of CCR5 impairs HIV ability to infect cells and cause disease. An understanding of this mechanism led to the development of a class of HIV medicines, the entry inhibitors.^[12] The presence of this mutation, however, is not a unifying theme among LTNPs and is observed in an exceedingly small number of these patients.
• HLA type has also been correlated with long-term non-progressor cohorts. In particular, strong correlations have been found between possessing the class 1 HLA-B*5701,^[13] HLA-B*5703,^[14] and/or HLA-B*2705^[15] alleles and ability to exert control over HIV.

• Antibody production. All individuals with HIV make antibodies against the virus. In most patients, broadly neutralizing antibodies do not emerge until approximately 2–4 years after the initial infection. At this point, the latent reservoir has already been established and the presence of broadly neutralizing antibodies is not enough to prevent disease progression. In some rare patients, these antibodies emerge earlier and can result in a delayed disease course. These patients, however, are not typically classified as LTNPs, but rather as slow progressors, who will eventually develop AIDS. Induction of broadly neutralizing antibodies in healthy individuals is a potential strategy for a preventive HIV vaccine, as is the elicitation of these antibodies through rationally designed immunogens. Direct production of these antibodies in somatic tissue through plasmid transfection also pose a viable method for making these antibodies available in a large number of humans.
• APOBEC3G protein production. In a small number of people infected with HIV, the virus is naturally suppressed without medical treatment. These people may carry high quantities of a protein called APOBEC3G that disrupts viral replication in cells. APOBEC3G, or "A3" for short, is a protein that sabotages reverse transcription, the process HIV relies on for its replication. This process involves the virus transcribing its singe-stranded RNA genome into double-stranded DNA that is incorporated into the cell's genome. A3 usually stops dormant viruses in the human genome, called endogenous retroviruses, from reawakening and causing infections.^[16]

References

1. http://www.aidsmap.com/HIV-non-progressor-status-established-soon-after-infection/page/1432975/
2. Understanding Long-term Nonprogressors. International AIDS Vaccine Initiative. accessed Dec 2007. Archived October 9, 2006 at the Wayback Machine
3. Poropatich, Kate; Sullivan, David J. (2010). "Human immunodeficiency virus type 1 long-term non-progressors: the viral, genetic and immunological basis for disease non-progression". Journal of General Virology 92 (2). doi:10.1099/vir.0.027102-0.
4. Rhodes DI, Ashton L, Solomon A, Carr A, Cooper D, Kaldor J, Deacon N (November 2000). "Characterization of three nef-defective human immunodeficiency virus type 1 strains associated with long-term nonprogression. Australian Long-Term Nonprogressor Study Group". J. Virol. 74 (22): 10581–8. doi:10.1128/jvi.74.22.10581-10588.2000. PMC 110932. PMID 11044102. Retrieved 2010-10-13.
5. National Institute of Allergy and Infectious Diseases, http://www.niaid.nih.gov/volunteer/hivlongterm/Pages/default.aspx, accessed July 5, 2011
6. Walker BD (2007). "Elite control of HIV Infection: implications for vaccines and treatment". Top HIV Med. 15 (4): 134–6. PMID 17720999.
7. O’connell, K. A.; Bailey, J. R.; Blankson, J. N. (2009). "Elucidating the elite: mechanisms of control in HIV-1 infection". Trends in Pharmacological Sciences 30 (12): 631–637. doi:10.1016/j.tips.2009.09.005. PMID 19837464.
8. Blankson, J. N. (2009). "Effector mechanisms in HIV-1 infected elite controllers: Highly active immune responses?". Antiviral Research 85 (1): 295–302. doi:10.1016/j.antiviral.2009.08.007. PMC 2814919. PMID 19733595.
9. http://journals.lww.com/aidsonline/Fulltext/2006/03210/A_nonsense_mutation__428G__A__in_the.7.aspx
10. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1315998/?tool=pubmed
11. Hendrickson, S. L.; Hutcheson, H. B.; Ruiz-Pesini, E.; Poole, J. C.; Lautenberger, J.; Sezgin, E.; Kingsley, L.; Goedert, J. J.; Vlahov, D.; Donfield, S.; Wallace, D. C.; OʼBrien, S. J. (2008-11-30). "Mitochondrial DNA haplogroups influence AIDS progression". AIDS 22 (18): 2429–2439. doi:10.1097/QAD.0b013e32831940bb. ISSN 0269-9370. PMC 2699618. PMID 19005266.
12. Lambotte Olivier, Boufassa Faroudy, Madec Yoann, Nguyen Ahn; et al. (2005). "HIV controllers: a homogeneous group of HIV-1-infected patients with spontaneous control of viral replication". Clinical Infectious Diseases 41 (7): 1053–6. doi:10.1086/433188. PMID 16142675.
13. Migueles, S. A.; Sabbaghian, M. S.; Shupert, W. L.; Bettinotti, M. P.; Marincola, F. M.; Martino, L.; Hallahan, C. W.; Selig, S. M.; Schwartz, D.; Sullivan, J.; Connors, M. (2000-02-29). "HLA B*5701 is highly associated with restriction of virus replication in a subgroup of HIV-infected long term nonprogressors". Proceedings of the National Academy of Sciences 97 (6): 2709–2714. doi:10.1073/pnas.050567397. ISSN 0027-8424. PMC 15994. PMID 10694578.
14. Costello, C.; Tang, J.; Rivers, C.; Karita, E.; Meizen-Derr, J.; Allen, S.; Kaslow, R. A. (1999-10-01). "HLA-B*5703 independently associated with slower HIV-1 disease progression in Rwandan women". AIDS 13 (14): 1990–1991. doi:10.1097/00002030-199910010-00031. PMID 10513667. Retrieved 2013-06-12.
15. Almeida, J. R.; Price, D. A.; Papagno, L.; Arkoub, Z. A.; Sauce, D.; Bornstein, E.; Asher, T. E.; Samri, A.; Schnuriger, A.; Theodorou, I.; Costagliola, D.; Rouzioux, C.; Agut, H.; Marcelin, A.-G.; Douek, D.; Autran, B.; Appay, V. (2007-09-24). "Superior control of HIV-1 replication by CD8+ T cells is reflected by their avidity, polyfunctionality, and clonal turnover". Journal of Experimental Medicine 204 (10): 2473–2485. doi:10.1084/jem.20070784. ISSN 0022-1007.
16. http://www.newscientist.com/article/dn24426-virussabotaging-protein-may-help-people-defy-hiv.html

12. "Delineating Antibody Recognition in Polyclonal Sera from Patterns of HIV-1 Isolate Neutralization" http://www.sciencemag.org/content/340/6133/751.abstract

External links

• The International HIV Controllers Study
• The Zephyr Foundation