Inhibition of HIV-1 disease progression by contemporaneous HIV-2 infection.

BACKGROUND: Progressive immune dysfunction and the acquired immunodeficiency syndrome (AIDS) develop in most persons with untreated infection with human immunodeficiency virus type 1 (HIV-1) but in only approximately 20 to 30% of persons infected with HIV type 2 (HIV-2); among persons infected with both types, the natural history of disease progression is poorly understood. METHODS: We analyzed data from 223 participants who were infected with HIV-1 after enrollment (with either HIV-1 infection alone or HIV-1 and HIV-2 infection) in a cohort with a long follow-up duration (approximately 20 years), according to whether HIV-2 infection occurred first, the time to the development of AIDS (time to AIDS), CD4+ and CD8+ T-cell counts, and measures of viral evolution. RESULTS: The median time to AIDS was 104 months (95% confidence interval [CI], 75 to 133) in participants with dual infection and 68 months (95% CI, 60 to 76) in participants infected with HIV-1 only (P=0.003). CD4+ T-cell levels were higher and CD8+ T-cell levels increased at a lower rate among participants with dual infection, reflecting slower disease progression. Participants with dual infection with HIV-2 infection preceding HIV-1 infection had the longest time to AIDS and highest levels of CD4+ T-cell counts. HIV-1 genetic diversity was significantly lower in participants with dual infections than in those with HIV-1 infection alone at similar time points after infection. CONCLUSIONS: Our results suggest that HIV-1 disease progression is inhibited by concomitant HIV-2 infection and that dual infection is associated with slower disease progression. The slower rate of disease progression was most evident in participants with dual infection in whom HIV-2 infection preceded HIV-1 infection. These findings could have implications for the development of HIV-1 vaccines and therapeutics. (Funded by the Swedish International Development Cooperation Agency-Swedish Agency for Research Cooperation with Developing Countries and others.).

Effect of complement on HIV-2 plasma antiviral activity is intratype specific and potent.

Human immunodeficiency virus type 2 (HIV-2)-infected individuals develop immunodeficiency with a considerable delay and transmit the virus at rates lower than HIV-1-infected persons. Conceivably, comparative studies on the immune responsiveness of HIV-1- and HIV-2-infected hosts may help to explain the differences in pathogenesis and transmission between the two types of infection. Previous studies have shown that the neutralizing antibody response is more potent and broader in HIV-2 than in HIV-1 infection. In the present study, we have examined further the function of the humoral immune response and studied the effect of complement on the antiviral activity of plasma from singly HIV-1- or HIV-2-infected individuals, as well as HIV-1/HIV-2 dually infected individuals. The neutralization and antibody-dependent complement-mediated inactivation of HIV-1 and HIV-2 isolates were tested in a plaque reduction assay using U87.CD4.CCR5 cells. The results showed that the addition of complement increased intratype antiviral activities of both HIV-1 and HIV-2 plasma samples, although the complement effect was more pronounced with HIV-2 than HIV-1 plasma. Using an area-under-the-curve (AUC)-based readout, multivariate statistical analysis confirmed that the type of HIV infection was independently associated with the magnitude of the complement effect. The analyses carried out with purified IgG indicated that the complement effect was largely exerted through the classical complement pathway involving IgG in both HIV-1 and HIV-2 infections. In summary, these findings suggest that antibody binding to HIV-2 structures facilitates the efficient use of complement and thereby may be one factor contributing to a strong antiviral activity present in HIV-2 infection.

Potent intratype neutralizing activity distinguishes human immunodeficiency virus type 2 (HIV-2) from HIV-1.

HIV-2 has a lower pathogenicity and transmission rate than HIV-1. Neutralizing antibodies could be contributing to these observations. Here we explored side by side the potency and breadth of intratype and intertype neutralizing activity (NAc) in plasma of 20 HIV-1-, 20 HIV-2-, and 11 dually HIV-1/2 (HIV-D)-seropositive individuals from Guinea-Bissau, West Africa. Panels of primary isolates, five HIV-1 and five HIV-2 isolates, were tested in a plaque reduction assay using U87.CD4-CCR5 cells as targets. Intratype NAc in HIV-2 plasma was found to be considerably more potent and also broader than intratype NAc in HIV-1 plasma. This indicates that HIV-2-infected individuals display potent type-specific neutralizing antibodies, whereas such strong type-specific antibodies are absent in HIV-1 infection. Furthermore, the potency of intratype NAc was positively associated with the viral load of HIV-1 but not HIV-2, suggesting that NAc in HIV-1 infection is more antigen stimulation dependent than in HIV-2 infection, where plasma viral loads typically are at least 10-fold lower than in HIV-1 infection. Intertype NAc of both HIV-1 and HIV-2 infections was, instead, of low potency. HIV-D subjects had NAc to HIV-2 with similar high potency as singly HIV-2-infected individuals, whereas neutralization of HIV-1 remained poor, indicating that the difference in NAc between HIV-1 and HIV-2 infections depends on the virus itself. We suggest that immunogenicity and/or antigenicity, meaning the neutralization phenotype, of HIV-2 is distinct from that of HIV-1 and that HIV-2 may display structures that favor triggering of potent neutralizing antibody responses.

Microbial translocation correlates with the severity of both HIV-1 and HIV-2 infections.

Microbial translocation has been linked to systemic immune activation during human immunodeficiency virus (HIV) type 1 infection. Here, we show that an elevated level of microbial translocation, measured as plasma lipopolysaccharide (LPS) concentration, correlates with AIDS in both individuals infected with HIV type 1 and individuals infected with HIV type 2. LPS concentration also correlates with CD4+ T cell count and viral load independently of HIV type. Furthermore, elevated plasma LPS concentration was found to be concomitant with defective innate and mitogen responsiveness. We suggest that microbial translocation may contribute to loss of CD4+ T cells, increase in viral load, and defective immune stimuli responsiveness during both HIV type 1 and HIV type 2 infections.

Studies on toll-like receptor stimuli responsiveness in HIV-1 and HIV-2 infections.

BACKGROUND: HIV-1 and HIV-2 are two related viruses with distinct clinical outcomes, where HIV-1 is more pathogenic and transmissible than HIV-2. The pathogenesis of both infections is influenced by the dysregulation and deterioration of the adaptive immune system. However, their effects on the responsiveness of innate immunity are less well known. Here, we report on toll-like receptor (TLR) stimuli responsiveness in HIV-1 or HIV-2 infections. METHODS: Whole blood from 235 individuals living in Guinea-Bissau who were uninfected, infected with HIV-1, infected with HIV-2, and/or infected with HTLV-I, was stimulated with TLR7/8 and TLR9 agonists, R-848 and unmethylated CpG DNA. After TLR7/8 and TLR9 stimuli, the expression levels of IL-12 and IFN-alpha were related to gender, age, infection status, CD4(+) T cell counts, and plasma viral load. RESULTS: Defective TLR9 responsiveness was observed in the advanced disease stage, along with CD4(+) T cell loss in both HIV-1 and HIV-2 infections. Moreover, TLR7/8 responsiveness was reduced in HIV-1 infected individuals compared with uninfected controls. CONCLUSIONS: Innate immunity responsiveness can be monitored by whole blood stimulation. Both advanced HIV-1 and HIV-2 infections may cause innate immunity dysregulation.

Short-term HIV-1 treatment interruption is associated with dysregulated TLR-stimuli responsiveness.

Viremia during human immunodeficiency virus type-1 (HIV-1) infection results in progressive impairment of several components of the immune system. Here a unique model of repeated treatment interruptions (TIs) was used with the aim to reveal the effect of controlled short-term viremia on innate stimuli responsiveness and circulating dendritic cells (DCs). Sequential peripheral blood samples from HIV-1-infected patients on combination antiretroviral therapy, subjected to repeated TI cycles as part of a therapeutic DNA vaccination study, were analyzed. In vitro responsiveness of peripheral blood mononuclear cells to toll-like receptor (TLR) stimuli was analyzed by cytokine secretion, and frequencies of plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) were monitored by flow cytometry. These parameters were found not to be significantly different between the vaccinated and placebo groups. Instead, independent of vaccination altered in vitro TLR responsiveness was observed in parallel with TI cycles. TLR7/8-triggered secretion of IL-12 and IFN-α, as well as TLR9-triggered secretion of IL-12, was hyperactivated. In contrast, expression of IFN-α after TLR9 stimulation decreased during the initial cycle of TI. Reduced frequencies of pDCs and mDCs, compared with baseline, were noted before and during the second TI, respectively. Furthermore, spontaneous ex vivo release of IL-12 from PBMC was noted during cycles of TI. In conclusion, these results suggest that consequences of short-term TI include dysregulated TLR responses and fluctuations in the frequencies of circulating DCs. Knowledge of these immunological factors may influence the continuation of stringent treatment schedules during HIV infections.

Suppression of HIV replication in vitro by CpG and CpG conjugated to the non toxic B subunit of cholera toxin.

Administration of oligodeoxynucleotides (ODNs) containing CpG motifs generates a rapid and potent response of CC-chemokines, known as ligands of the HIV-1 co-receptor CCR5, in the murine female genital tract. The present study explored the potential HIV inhibitory activities of different human CpG prototypes either alone or conjugated to the non-toxic subunit of cholera toxin (CTB). Results showed that in vitro replication of both HIV-1 and HIV-2 can be suppressed by different human CpG prototypes. Importantly, the conjugation of CpG ODN to CTB (CTB-CpG) enhanced the antiviral activity of CpG against primary HIV-1 isolates of both R5 and X4 phenotypes in peripheral blood mononuclear cells (PBMC) as well as U87.CD4 co-receptor indicator cells. CTB-CpGs triggered higher amounts of MIP-1alpha, and MIP-1beta in PBMC than the corresponding CpG ODNs, which may explain the superior antiviral effect of CTB-CpG against R5 virus in PBMC. Incubation of PBMC with CpG ODN and CTB-CpG did not alter surface expression of HIV-1 receptors indicating that the observed anti-HIV-1 effect is not mediated through down regulation of HIV-1 receptors on target cells. Further, the enhanced antiviral effect of CTB-CpG was dependent on the presence of phosphorothioate backbone in the ODN, whereas the presence of CpG motif in ODNs was dispensable. These results have implications for the development of novel intervention strategies to prevent HIV infection.