Oral EBV and KSHV Infection in HIV

The gamma herpesviruses, Kaposi’s-sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are tightly associated with the development of AIDS-associated oral disease and malignancy during immune suppression. The objective of this investigation was to characterize oral infection and pathogenesis in healthy and immune-suppressed individuals. To characterize oral EBV and KSHV infection, we examined throat washings and oral epithelial cells from HIV-positive and HIV-negative individuals. Quantitative/real-time polymerase-chain-reaction (PCR) assays, transmission electronmicroscopy, immunostaining, and sequence analysis were used to identify viral infection. Virus was isolated from throat-wash samples and was used to infect epithelial and lymphoid cell lines. We detected EBV and KSHV in the oral cavity in healthy and immune-suppressed individuals. Viral strain analysis of KSHV K1 in multiple clones from the oral cavities of healthy persons and immunosuppressed patients detected several strains previously detected in KS lesions, with minor strain variation within individuals. Immunoelectron microscopy for multiple viral antigens detected consistent expression of viral proteins and oral epithelial specimens. In oral epithelial cells infected with wild-type KSHV in vitro, the K8.1 glycoprotein associated with lytic KSHV infection was detected in both primary and telomerase immortalized oral epithelial cultures by 24 hours post-infection. Virions were detected, subsequent to infection, by scanning electron microscopy. Oral epithelial cells were also infected in vitro with wild-type EBV originating from throat washes. Analysis of these data suggests that, like EBV, KSHV infection is present in the oropharynx of healthy individuals, is transmissible in vitro, and may be transmitted by saliva.

Epstein-Barr virus early antigen diffuse (EBV-EA/D)-directed immunoglobulin A antibodies in systemic lupus erythematosus patients

OBJECTIVE

We sought to determine whether the serological response towards lytic cycle antigens of Epstein-Barr virus (EBV) is altered in systemic lupus erythematosus (SLE) patients.

METHOD

We used enzyme-linked immunosorbent assay (ELISA) to investigate the prevalence of EBV early antigen diffuse (EBV-EA/D) antibodies in sera from 60 patients with SLE, 40 with scleroderma (SSc), 20 with primary Sjögren's syndrome (pSS), 20 with rheumatoid arthritis (RA), 20 healthy controls, and also subjects with various circulating autoantibodies. Samples from patients were obtained from clinics specialized within the diseases in Denmark and Sweden and samples from healthy controls were obtained from volunteers.

RESULTS

A significant elevated titre of immunoglobulin (Ig)A, IgG, and IgM EBV-EA/D antibodies was found in SLE patients compared to healthy controls, a finding not explained by immunosuppressive treatment or disease activity. The largest difference was observed for IgA EBV-EA/D antibodies (p = 0.0013) with a seropositive rate of 58% in SLE patients and 0% in healthy controls. RA and SSc patients and individuals seropositive for anti-Scl-70 were additionally found to have elevated titres of IgA EBV-EA/D antibodies (40%, p = 0.014; 60%, p = 0.015; and 38.5%, p = 0.045, respectively). However, the titres were generally lower than in SLE patients.

CONCLUSION

Our findings support an association between EBV and SLE. The elevated titre of EBV-EA/D-directed IgA antibodies found in SLE patients could suggest reactivation of EBV in epithelial cells or reinfection of epithelial cells after reactivation in B cells, indicating lack of control of the latent infection.

Interaction of the chaperone calreticulin with proteins and peptides of different structural classes

The interaction of calreticulin with native and denatured forms and polypeptides in proteolytic digests of proteins representing structural classes of all-alpha-helix (hemoglobin, serum albumin), all-beta-sheet (IgG) and alpha-helix + beta-sheets (lysozyme, ovalbumin) was investigated. The binding of calreticulin to denatured proteins was found to depend on conformation and structural class of the protein. No interaction was observed with the native proteins, whereas binding was seen for the denatured proteins, the order of interaction being lysozyme = IgG > ovalbumin >> hemoglobin = serum albumin. Moreover, the interaction between calreticulin and the heat-denatured proteins depended on the temperature and time used for denaturation and the degree of proteolytic fragmentation. Calreticulin bound well to peptides in proteolytic digests from protease K or chymotrypsin treatment of lysozyme, IgG and ovalbumin but weakly or not at all to peptides in proteolytic digests of hemoglobin and serum albumin. Synthetic peptides from lysozyme and ovalbumin confirmed binding to hydrophobic peptides from these proteins. These results show that calreticulin has the ability to interact with denatured and fragmented forms of proteins with a preference for beta-strand structure and hydrophobicity.

Interaction of calreticulin with amyloid beta peptide 1-42

The interaction of calreticulin with amyloid beta (Abeta) was investigated using solid phase and solution binding assays. Calreticulin bound Abeta 1-42 in a time and concentration dependent fashion. The binding was optimal at pH 5 and was stimulated by Ca2+ and inhibited by Zn2+ at pH 7. Interaction took place through the hydrophobic C-terminus of Abeta 1-42 and the polypeptide binding site of calreticulin. The results are discussed in the light of a reported role of calreticulin as a cell surface scavenger receptor.

Functional interaction between the cytoplasmic leucine-zipper domain of HIV-1 gp41 and p115-RhoGEF

The long cytoplasmic tail of the human immunodeficiency virus (HIV)-1 transmembrane protein gp41 (gp41C) is implicated in the replication and cytopathicity of HIV-1 [1]. Little is known about the specific functions of gp41C, however. HIV-1 or simian immunodeficiency virus (SIV) mutants with defective gp41C have cell-type- or species-dependent phenotypes [2] [3] [4] [5] [6]. Thus, host factors are implicated in mediating the functions of gp41C. We report here that gp41C interacted with the carboxy-terminal regulatory domain of p115-RhoGEF [7], a specific guanine nucleotide exchange factor (GEF) and activator of the RhoA GTPase, which regulates actin stress fiber formation, activation of serum response factor (SRF) and cell proliferation [8] [9]. We demonstrate that gp41C inhibited p115-mediated actin stress fiber formation and activation of SRF. An amphipathic helix region with a leucine-zipper motif in gp41C is involved in its interaction with p115. Mutations in gp41C leading to loss of interaction with p115 impaired HIV-1 replication in human T cells. These findings suggest that an important function of gp41C is to modulate the activity of p115-RhoGEF and they thus reveal a new potential anti-HIV-1 target.

Induction of MHC class I expression on immature thymocytes in HIV-1-infected SCID-hu Thy/Liv mice: evidence of indirect mechanisms

The SCID-hu Thy/Liv mouse and human fetal thymic organ culture (HF-TOC) models have been used to explore the pathophysiologic mechanisms of HIV-1 infection in the thymus. We report here that HIV-1 infection of the SCID-hu Thy/Liv mouse leads to the induction of MHC class I (MHCI) expression on CD4+CD8+ (DP) thymocytes, which normally express low levels of MHCI. Induction of MHCI on DP thymocytes in HIV-1-infected Thy/Liv organs precedes their depletion and correlates with the pathogenic activity of the HIV-1 isolates. Both MHCI protein and mRNA are induced in thymocytes from HIV-1-infected Thy/Liv organs, indicating induction of MHCI gene expression. Indirect mechanisms are involved, because only a fraction (<10%) of the DP thymocytes were directly infected by HIV-1, although the majority of DP thymocytes are induced to express high levels of MHCI. We further demonstrate that IL-10 is induced in HIV-1-infected thymus organs. Similar HIV-1-mediated induction of MHCI expression was observed in HF-TOC assays. Exogenous IL-10 in HF-TOC induces MHCI expression on DP thymocytes. Therefore, HIV-1 infection of the thymus organ leads to induction of MHCI expression on immature thymocytes via indirect mechanisms involving IL-10. Overexpression of MHCI on DP thymocytes can interfere with thymocyte maturation and may contribute to HIV-1-induced thymocyte depletion.