Characterisation of the epitope for a herpes simplex virus glycoprotein B-specific monoclonal antibody with high protective capacity.

Monoclonal antibody (MAb) 2c, specific for glycoprotein B of herpes simplex virus (HSV), had been shown to mediate clearance of infection from the mucous membranes of mice, thereby completely inhibiting mucocutaneous inflammation and lethality, even in mice depleted of both CD4(+) and CD8(+) cells. Additionally, ganglionic infection was highly restricted. In vitro, MAb 2c exhibits a potent complement-independent neutralising activity against HSV type 1 and 2, completely inhibits the viral cell-to-cell spread as well as the syncytium formation induced by syncytial HSV strains (Eis-Hübinger et al. in Intervirology 32:351-360, 1991; Eis-Hübinger et al. in J Gen Virol 74:379-385, 1993). Here, we describe the mapping of the epitope for MAb 2c. The antibody was found to recognise a discontinuous epitope comprised of the HSV type 1 glycoprotein B residues 299 to 305 and one or more additional discontinuous regions that can be mimicked by the sequence FEDF. Identification of the epitope was confirmed by loss of antibody binding to mutated glycoprotein B with replacement of the epitopic key residues, expressed in COS-1 cells. Similarly, MAb 2c was not able to neutralise HSV mutants with altered key residues, and MAb 2c was ineffective in mice inoculated with such mutants. Interestingly, identification and fine-mapping of the discontinuous epitope was not achieved by binding studies with truncated glycoprotein B variants expressed in COS cells but by peptide scanning with synthetic overlapping peptides and peptide key motif analysis. Reactivity of MAb 2c was immensely increased towards a peptide composed of the glycoprotein B residues 299 to 305, a glycine linker, and a C-terminal FEDF motif. If it could be demonstrated that antibodies of the specificity and bioactivity of MAb 2c can be induced by the epitope or a peptide mimicking the epitope, strategies for active immunisation might be conceivable.

A simian immunodeficiency virus V3 loop mutant that does not efficiently use CCR5 or common alternative coreceptors is moderately attenuated in vivo.

Sexually transmitted HIV-1 strains utilize the chemokine receptor CCR5 for viral entry and inhibitors targeting this coreceptor offer great promise for antiretroviral therapy. They also raise the question, however, whether viral variants exhibiting altered coreceptor interactions and resistance against these antiviral agents might still be pathogenic. In the present study, we analyzed a SIVmac239 envelope (Env) mutant (239DL) containing two mutations in the V3 loop which reduced viral entry via CCR5 by 10- to 20-fold, disrupted utilization of common alternative SIV coreceptors and changed the way Env engaged CCR5. To evaluate its replicative capacity and pathogenic potential in vivo we infected six rhesus macaques with 239DL. We found that 239DL replication was only slightly attenuated early during infection. Thereafter, a D324V change, which restored efficient CCR5 usage and coincided with 239wt-like levels of viral replication, emerged in two animals. In contrast, the viral geno- and phenotype remained stable in the other four rhesus macaques. Although these animals had about 100-fold reduced viral RNA loads relative to 239wt-infected macaques, they showed pronounced CD4 T-cell depletion in the intestinal lamina propria, and one developed opportunistic infections and died with simian AIDS. Thus, changes in the V3 loop that diminished CCR5 usage and altered Env interactions with CCR5 reduced the pathogenic potential of SIVmac in rhesus macaques but did not abolish it entirely.

Replication of M-tropic HIV-1 in activated human intestinal lamina propria lymphocytes is the main reason for increased virus load in the intestinal mucosa.

The gastrointestinal tract is the site of early abundant HIV replication and associated marked CD4 T-cell depletion. The aim of this study was to characterize the basis for the increased HIV replication in this compartment. Isolated mononuclear cells of the peripheral blood (PBMCs), the intestinal lamina propria (LPMCs), and purified gut lamina propria CD4 T-cell subpopulations (LP T cells) were isolated, phenotypically characterized, and infected in vitro with 2 different HIV-1 strains. T-cell subpopulations were analyzed by fluorescence-activated cell sorter. HIV-1 core protein p24 was determined in supernatants after in vitro infection. Furthermore the effect of T-cell stimulation on the replication of M- and T-tropic HIV strains was studied. In vitro replication of HIV-1 was significantly increased in CD69 compared with CD69 CD4 LP T cells, while there was no difference between CD103 and CD103 CD4 LP T cells. Experimental stimulation of LPMCs, which mimics activation by intestinal pathogens frequently present in the bowel of HIV-infected patients, further dramatically enhances HIV replication (24.5-fold) compared with nonstimulated LPMCs. M-tropic HIV-1 showed a preferential replication in LPMCs, while T-tropic HIV-1 strain showed a preferential replication in PBMCs. Thus, the elevated activation state of target cells in the intestine and not the expression of the homing marker CD103 is directly linked to massive HIV production.

Dysregulated peripheral and mucosal Th1/Th2 response in Whipple's disease.

BACKGROUND & AIMS: An impaired monocyte function and impaired interferon (IFN)-gamma production has been suggested as a possible pathogenetic factor in Whipple's disease (WD) and as a cause for the delayed elimination of Tropheryma whipplei in some patients. METHODS: We studied, in a series of 20 WD patients with various degrees of disease activity, cellular immune functions. RESULTS: We found an increased in vitro production of interleukin (IL)-4 by peripheral mononuclear blood cells as determined by enzyme-linked immunosorbent assay, but reduced secretion of IFN-gamma and IL-2 as compared with age- and sex-matched controls. In addition, we observed a significantly reduced monocyte IL-12 production in response to various stimuli in WD patients whereas other cytokines were comparable with controls; these immunologic alterations were not significantly different in patients with various disease activities. At the mucosal level, we found decreased CD4 T-cell percentage and a significantly impaired IFN-gamma secretion. CONCLUSIONS: Our data define a defective cellular immune response in a large series of WD patients and point to an important pathogenetic role of impaired Th1 responses. The decreased monocyte IL-12 levels may result in reduced peripheral and mucosal IFN-gamma production and lead to an increased susceptibility to T. whipplei infection in certain hosts.