HIV, the virus that causes AIDS, shows high genetic variability. A number of types of this virus exist and are more or less widespread in different parts of the world. Subtype B is the dominant form in the West, where most of the drugs are developed and tested. However, 90 percent of the people infected with HIV carry other types of the virus that are common in Asia and Africa.
Some experts feared that HIV therapies might be less effective against other types of the virus. However, these reservations have proven unfounded, as researchers of the Swiss HIV Cohort Study have shown in a recently published study (*). “Most of the studies up to now suffered from the fact that patients with distinct genetic background and infected with different HIV subtypes were compared,” Huldrych Günthard from the University Hospital Zurich, explains. “As a result it was not clear whether varying degrees of therapeutic success were due to the subtype or the ethnic group. The size of our cohort enables us to examine this question for the first time within a single ethnic group, i.e. with white patients only.”
Less treatment failures with other virus types
A total of 5,268 patients were included in the study, 4,729 with subtype B, 539 with another subtype. As expected, HIV therapy worked well against subtype B: per 100 years of treatment (i.e. if you treat 100 patients for a year or 50 patients for two years) approximately four treatment failures occurred in which the viral load in the blood either never decreased sufficiently or rose suddenly at a later stage in treatment. In patients with non-B subtypes, the treatment failed on even fewer occasions: only approximately twice in 100 treatment years.
According to Günthard, this result does not necessarily mean that HIV therapies would be more successful in Africa and Asia than in Europe. Other circumstances also play a role, such as genetic factors or how closely the patient follows the doctor’s recommendations. However, one can now at least rule out the possibility that existing therapies cannot contain virus subtypes that are predominant in Africa and Asia. The results are also relevant to Switzerland: as in North America and the rest of Europe, non-B subtypes of HIV are becoming ever more frequent here.
(*) Alexandra U. Scherrer, Bruno Ledergerber, Viktor von Wyl, Jürg Böni, Sabine Yerly, Thomas Klimkait, Philippe Bürgisser, Andri Rauch, Bernard Hirschel, Matthias Cavassini, Luigia Elzi, Pietro L. Vernazza, Enos Bernasconi, Leonhard Held, Huldrych F.Günthard, and the Swiss HIV Cohort Study (2011). Improved Virological Outcome in White Patients Infected With HIV-1 Non-B Subtypes Compared to Subtype B. Clinical Infectious Diseases online: doi: 10.1093/cid/cir669 (available as a PDF document from the SNSF; E-Mail: email@example.com).
Prof. Dr. med. Huldrych Günthard
Klinik für Infektionskrankheiten und Spitalhygiene
Phone: +41 (0) 44 255 34 50