Friday, July 9, 2010
The HIV Sweet Spot
The human immunodeficiency virus (HIV), while an awful and dreaded pathogen, is amazing. Many viruses, while causing disease, are static targets for which antibody defense systems are designed. For example, take the mumps virus, an RNA Paramyxovirus. It infects only humans and is generally transmitted by salivary secretions. Once it infects a person, a series of inflammatory responses ensue, most commonly swelling of the parotid glands. The "invader" is recognized by the victim's immune system, antibodies are produced and viral eradication is accomplished.
Specialized immune cells have the machinery to pick up characteristics on the viral structure and then to synthesize proteins (antibodies), which are "lock and key" fits. Once the antibody attaches to the virus, the virus-antibody complex is vulnerable to further attack and eradication. And so it goes for the myriad of disease attackers.
Vaccines are given to prevent disease by stimulating the immune system to produce antibodies to a potential infection. In the case of a mumps vaccinated person, who becomes infected with mumps virus, the already present antibodies latch onto the invader before it can cause any disease symtoms. The virus is eradicated quickly, before it can replicate itself.
Basically the antibody is site specific. The key for success is that all of the viruses of the specific disease have the same site. And therein lies the fascination with HIV. This virus is always mutating its look. Although an HIV infected person produces scads of antibodies, they are relatively ineffective, since the site for which they were produced changes. So while some of the viruses with the "old" sites can be eradicated, there's always a new population of mutated pathogens ready to carry on the disease process. In other words, you never get the same pitch twice when you're trying to bat against HIV.
A report in Science cites a patient, whose immune system has found a non changing antigenic site on the HIV. NON CHANGING. He was able to make antibodies, labeled VRCo1 and VRCo2, which attacked this "sweet spot". These antibodies were able to eradicate about 91% of the 190 known HIV types.
The trick now is to be able to simulate the sweet spot so that it can be "vaccinized". If a person could be given the sweet spot protein sequence and shape, his immune system would produce his own VRCo1 and VRCo2 antibodies. Consequently, immunity would be achieved. In the event that infection occurred, the already present antibody would quickly attach to the HIV and the organism could be quickly eliminated.
This news is a step forward in the development of a successful vaccine. There are 30-40 million people infected with HIV at present and the mortality so far approximates 30 million. Perhaps with the sweet spot as a target, the release of a valid vaccine is in the near future.