[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: It has been postulated that dual infections of humans with human immunodeficiency virus (HIV) and human T-cell leukemia/lymphotropic virus (HTLV) may potentiate disease progression. Counterparts of both of these pathogenic human retroviruses have been identified in various simian species indigenous to Asia and Africa, including sooty mangabey monkeys (Cercocebus atys). Using peripheral blood mononuclear cells (PBMC) from a mangabey naturally infected with both SIV and STLV-I, T-cell lines were established and maintained continuously for more than 3 years; these cell lines harbored only a newly identified mangabey STLV-I(sm) or both STLV-I(sm) and the acutely lethal variant SIVsmmPBj14. The dually infected cell line (FEd-P14) was established by de novo infection of mangabey PBMC with SIVsmmPBj14. This cell line was characterized by multiple assays which showed that structural proteins encoded by both viruses were produced in large quantities, but that the predominant viral glycoprotein on the cell surface was the STLV-I(sm) Env. Unusual interactions of the two retroviral glycoproteins were suggested by the formation of syncytia between Raji and the FEd-P14 cells, but not between Raji and simian cells infected with only one retrovirus or human cells infected with HTLV-I. The STLV-I(sm) strain obtained from the sooty mangabey was transmitted to normal macaque and mangabey PBMC and was shown to be unique by sequencing of the entire env gene. STLV-I(sm) from this African species was more closely related to "cosmopolitan" HTLV-I strains than to the prototypic STLV-I from an Asian pig-tailed macaque. In vitro and in vivo studies of STLV-I(sm) and SIVsmm, both isolated from a naturally infected mangabey monkey, may provide insight into disease induction and manifestations associated with coinfection by their human counterparts.
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