Clinical Relevance of HIV-1 Superinfection

Over time a single patient can be infected by multiple intraor intersubtype human immunodeficiency viruses type 1 (HIV-1) strains. These so-called dual infections are divided into co-infections and superinfections. HIV-1 co-infection is described as a second infection taking place before measurable HIV-1 antibody production by the immune system (seroconversion) and HIV-1 superinfection is defined as a second infection occurring after seroconversion. Here the focus lays on superinfections, which have implications for HIV-1 transmission, treatment and vaccine development (Gottlieb et al., 2004). Moreover superinfections can give rise to HIV-1 circulating recombinant forms (CRF); this significantly increases the global epidemiology (Gottlieb et al., 2007). Also due to these recombination events, two different drug resistant HIV-1 viruses could lead to multi drug resistance or even to more pathogenic viruses (Gottlieb et al., 2004, Blackard et al., 2004, Fernandez Larrosa et al., 2006). Another important issue that is not extensively surveyed in literature is the clinical relevance of HIV-1 superinfection, as most descriptions rely on case reports and not on controlled cohort studies. The individual cases differ in severity, as several superinfected patients with rapidly progressive HIV-1 disease have been described since 2002, but superinfection cases were also found by coincidence in long-term non-progressors (LTNPs). These patients were able to control HIV-1 disease before and sometimes also after the superinfection event. So it is not resolved yet how superinfection affects disease progression in general and, if any, specific host or viral factors are involved. In this chapter, first an overview will be given of HIV-1 superinfected patients from several studies, with regard to HIV-1 disease progression. Disease progression is indicated by an increase in the HIV-1 plasma viral load, a decrease in the CD4+ T-cell count, acquired immunodeficiency syndrome (AIDS) related events and/or the start of antiretroviral treatment. These outcomes are compared to values of disease progression for single HIV-1 infected patients, resulting in an indication of the clinical relevance of HIV-1 superinfection.