Lipopolysaccharide stimulates HIV-1 entry and degradation in human macrophages

The bacterial endotoxin LPS is a potent stimulator of monocyte and macrophage activation and has been shown to protect differentiated macrophages from de novo infection by HIV-1. However, the mechanisms of this inhibitory activity of LPS are not fully understood. We investigated the effect of LPS on the early post-binding steps of HIV-1 replication in primary macrophages. Paradoxically, when applied together with the virus, LPS stimulated entry of HIV-1 into macrophages, as judged by the amount of internalized HIV-1 RNA and p24. This stimulatory activity did not depend on receptors used for entry and did not require new protein synthesis. However, internalized viral RNA and p24 were rapidly degraded in LPS-stimulated macrophages. Surprisingly, while degradation of HIV-1 p24 in LPS-treated cells was inhibited by bafilomycin A1, HIV-1 RNA was not protected by this agent, suggesting that viral RNA is degraded by a pH-independent mechanism. These results indicate that LPS stimulates both virus uptake and virus degradation in macrophages.

CD147 facilitates HIV-1 infection by interacting with virus-associated cyclophilin A

Cyclophilin A (CyPA) is specifically incorporated into the virions of HIV-1 and has been shown to enhance significantly an early step of cellular HIV-1 infection. Our preliminary studies implicated CD147 as a receptor for extracellular CyPA. Here, we demonstrate a role for CyPA-CD147 interaction during the early steps of HIV-1 infection. Expression of human CD147 increased infection by HIV-1 under one-cycle conditions. However, susceptibility to infection by viruses lacking CyPA (simian immunodeficiency virus or HIV-1 produced in the presence of cyclosporin A) was unaffected by CD147. Virus-associated CyPA coimmunoprecipitated with CD147 from infected cells. Antibody to CD147 inhibited HIV-1 entry as evidenced by the delay in translocation of the HIV-1 core proteins from the membrane and inhibition of viral reverse transcription. Viruses whose replication did not require CyPA (SIV or mutant HIV-1) were resistant to the inhibitory effect of anti-CD147 antibody. These results suggest that HIV-1 entry depends on an interaction between virus-associated CyPA and CD147 on a target cell.

HIV-1 penetrates coronary artery endothelial cells by transcytosis

BACKGROUND

The pathogenesis of HIV-1-related cardiomyopathy is poorly understood, but HIV-1 has been detected in cardiomyocytes. Whether HIV-1 penetrates into the myocardium by infection of coronary artery endothelial cells (CAEC) or using transcellular or paracellular routes across CAEC has not been resolved.

MATERIALS AND METHODS

A model of the CAEC barrier was constructed with primary CAEC (derived from human coronary vessels). Polymerase chain reaction (PCR) assay, infectious assay, and immunofluorescence were employed to show abortive nature of HIV-1 infection of CAEC. Tight junction (TJ) and cell adhesion proteins were visualized by immunofluorescence. The time course of HIV-1 invasion was measured by HIV-1 RNA assay. Inulin permeability assay determined paracellular leakage. Transmission electron microscopy demonstrated virus-induced endothelial vacuolization.

RESULTS

Despite a strong display on CAEC of CXCR4 and a lesser expression of CCR3 and CCR5, HIV-1 did not productively replicate in CAEC, as shown by infectious assay, immunofluorescence, and electron microscopy. HIV-1 infection of CAEC was abortive with minimal reverse transcription of strong stop DNA and pol but not full-length or two LTR DNA circles. Upon infection of the model with 1 million RNA copies of HIV-1JR-FL, virus penetration 2 hr postinfection (PI) was negligible but increased by 1,750% 24 hr PI. The paracellular permeability increased during this period by only 25%. Neither AOP-RANTES nor v-MIPII significantly reduced HIV-1JR-FL invasion. Virus infection did not alter the integral TJ protein occludin and the TJ-associated protein ZO-1. HIV-1 exposed CAEC and brain microvascular endothelial cells (BMVEC) developed extensive cytoplasmic vacuolization with retroviral-like particles in the vacuoles.

CONCLUSIONS

The endothelium is not an impenetrable barrier to HIV-1. The virus opens a transcellular route across coronary and brain endothelia in cytoplasmic vacuoles.

The binding subunit of pertussis toxin inhibits HIV replication in human macrophages and virus expression in chronically infected promonocytic U1 cells

We have recently shown that the binding subunit of pertussis toxin (PTX-B) inhibits the entry and replication of macrophage-tropic (R5) HIV-1 strains in activated primary T lymphocytes. Furthermore, PTX-B suppressed the replication of T cell-tropic (X4) viruses at a postentry level in the same cells. In this study we demonstrate that PTX-B profoundly impairs entry and replication of the HIV-1(ADA) (R5), as well as of HIV pseudotyped with either murine leukemia virus or vesicular stomatitis virus envelopes, in primary monocyte-derived macrophages. In addition, PTX-B strongly inhibited X4 HIV-1 replication in U937 promonocytic cells and virus expression in the U937-derived chronically infected U1 cell line stimulated with cytokines such as TNF-alpha and IL-6. Of interest, TNF-alpha-mediated activation of the cellular transcription factor NF-kappaB was unaffected by PTX-B. Therefore, PTX-B may represent a novel and potent inhibitor of HIV-1 replication to be tested for efficacy in infected individuals. In support of this proposition, a genetically modified mutant of PTX (PT-9K/129G), which is safely administered for prevention of Bordetella pertussis infection, showed an in vitro anti-HIV profile superimposable to that of PTX-B.

The B-oligomer of pertussis toxin inhibits human immunodeficiency virus type 1 replication at multiple stages

We have recently demonstrated that the binding subunit (B-oligomer) of pertussis toxin (PTX-B) deactivates CCR5 and inhibits entry of R5 human immunodeficiency virus type 1 (HIV-1) strains in activated primary T lymphocytes (M. Alfano et al., J. Exp. Med. 190:597-605, 1999). We now present evidence that PTX-B also affects a post-entry step of HIV-1 replication. While PTX-B inhibited fusion induced by R5 but not that induced by X4 envelopes, it blocked infection of T cells with recombinant HIV-1 particles pseudotyped with R5, X4, and even murine leukemia virus or vesicular stomatitis virus envelopes. It also suppressed HIV-1 RNA synthesis in cultures of infected peripheral blood mononuclear cells when new infections had been inhibited by zidovudine, and it reduced Tat-dependent expression of the luciferase reporter gene controlled by the HIV-1 long terminal repeat (LTR). Surprisingly, PTX-B did not affect expression from the cytomegalovirus promoter, nor did it reduce the basal (Tat-independent) expression from the LTR promoter. These results indicate that PTX-B inhibits HIV-1 infection at both the entry and the post-entry stages of viral replication, with the post-entry activity specifically affecting transcription or stability of Tat-stimulated HIV-1 mRNAs.

Two nuclear localization signals in the HIV-1 matrix protein regulate nuclear import of the HIV-1 pre-integration complex

Replication of HIV-1 in non-dividing and slowly proliferating cell populations depends on active import of the viral pre-integration complex (PIC) into the cell nucleus. While it is commonly accepted that this process is mediated by an interaction between the HIV-1 PIC and the cellular nuclear import machinery, controversial results have been reported concerning the mechanisms of this interaction. Here, we demonstrate that a recently identified nuclear localization signal within the HIV-1 matrix protein (MA), MA NLS-2, together with previously described MA NLS-1, mediates nuclear import of the HIV-1 PIC. Inactivation of both MA NLSs precluded nuclear translocation of MA and rendered the virus defective in nuclear import and replication in non-dividing macrophage cultures, even when functional Vpr and integrase (IN), two more viral proteins implicated in HIV-1 nuclear import, were present. Taken together, these results indicate that Vpr does not function as an independent nuclear import factor and demonstrate that HIV-1 MA, by virtue of its two nuclear localization signals, regulates HIV-1 nuclear import.

Molecular characterization of a mouse genomic element mobilized by advanced glycation endproduct modified-DNA (AGE-DNA)

BACKGROUND

DNA modified by advanced glycation endproducts (AGEs) undergoes a high frequency of insertional mutagenesis. In mouse lymphoid cells, these mutations are due in part to the transposition of host genomic elements that contain a DNA region homologous to the Alu family of repetitive elements. One particular 853 bp insertion, designated INS-1, was identified previously as a DNA element common to plasmids recovered from multiple, independent lymphoid cell transfections.

MATERIALS AND METHODS

To characterize the genomic origin of this element, we used a 281-bp region of non-Alu-containing INS-1 sequence, designated. CORE, as a probe in Southern hybridization and for screening a bacteriophage mouse genomic DNA library. The resultant clones were sequenced and localized within the mouse genome.

RESULTS

Two distinct genomic clones of 15 kB and 17 kB in size were isolated. A 522-bp unique region common to INS-1 and corresponding to the CORE sequence was identified in each clone. In both cases, CORE was found to be surrounded by repetitive DNA sequences: a 339-bp MT repeat at the 5' end, and a 150-bp B1 repeat at the 3' end. The CORE sequence was localized to mouse chromosome 1.

CONCLUSIONS

These studies revealed that the CORE region of INS is present in low copy number but is associated with known repetitive DNA elements. The presence of these repetitive elements may facilitate the transposition of CORE by recombination or other, more complex rearrangement events, and explain in part the origin of AGE-induced insertional mutations.