HIV-2 and the Immune Response

HIV-1 and HIV-2 infections have important differences in epidemiology, clinical progression and transmission. Studies of the less transmissible and pathogenic HIV-2 have revealed some intriguing facts, indicating that it is less prone to replicate and perhaps can evoke a more efficient or long-lasting immune response than HIV-1 in the human host. Several crucial aspects of HIV-2 infection are still insufficiently characterised. However, there is now convincing evidence that plasma viral load is considerably lower for HIV-2 than for HIV-1, despite similar proviral (DNA) loads for the two viruses. There are reports on lower levels of apoptosis for HIV-2, possibly indicating a lower level of harmful immune activation. Several studies have also shown that vigorous HIV-2 specific immune responses can be detected, especially during the asymptomatic phase of HIV-2 infection. This includes humoral as well as cell-mediated immunity (CMI). The neutralising antibody response appears to be broader and the CMI may be more efficient for HIV-2 as compared to HIV-1. However, comparative studies in the same population groups on HIV-1 and HIV-2 immunity are scarce and difficult to perform. Nevertheless, by increasing our knowledge about how HIV-2 is contained to a higher degree than HIV-1, clinically as well as epidemiologically, we may gain knowledge that is useful in a wider perspective in our struggle to curb the devastating HIV/AIDS epidemic.