Detection and quantitation of human immunodeficiency virus type-1 particles by confocal microscopy.

A method is described to visualise directly human immunodeficiency virus type-1 (HIV-1) particles. HIV-1 containing samples were adsorbed onto a plastic surface and doubly labeled with antibodies specific for viral proteins and sensitive nucleic acids dyes. Laser scanning confocal microscopy detected co-localization of viral proteins and nucleic acids, thus allowing specific identification of HIV. Using this technique, we have quantified eight different HIV-1 sub-types and three HIV-1 groups in tissue culture supernatants from infected peripheral blood mononuclear cells (PBMCs). Confocal counts correlated well with electron microscopy (EM) counts and HIV-1 RNA loads as determined by quantitative PCR. Confocal microscopy may prove to be a simple alternative to electron microscopy for virus identification and quantitation.

In vivo uptake of an experimental microencapsulated diphtheria vaccine following sub-cutaneous immunisation.

Previous studies demonstrated in vitro phagocytosis of poly(lactide-co-glycolide) (PLGA) microspheres (MS) by macrophages and dendritic cells and the biodistribution of fluorescent PLGA particles following oral or intranasal administration. In this study, we report the uptake and biodistribution of sub-cutaneously administered fluorescent labelled PLGA MS loaded with diphtheria toxoid (DT). The cell type and percentage of fluorescent positive cells were determined by flow cytometry and confirmed by fluorescent microscopy. Fluorescent particles were detected inside cells of the peritoneal flush as early as 10 min post-inoculation, predominantly in cells of macrophage morphology. In vivo trafficking of PLGA particles following a sub-cutaneous immunisation of mice appeared to be governed by macrophages. However, in the first week after inoculation, dendritic cells played a significant role in the uptake and digestion of the microspheres, thereby triggering the immune response against the antigen. Fluorescent PLGA MS were also observed in cells of lymphoid tissues such as mesenteric lymph nodes (MLN) and spleen (S). However, microsphere fluorescence in lymphoid tissues decreased rapidly, as they were degraded inside the cells, thereby enabling the presentation of the antigen to specific cells of the immune system. To our knowledge, this is the first time the fate of immunogenic PLGA microspheres was studied in vivo following a sub-cutaneous injection route.

Optimization of nb-4 and hl-60 differentiation for use in opsonophagocytosis assays.

Production of effective vaccine formulations is dependent on the availability of assays for the measurement of protective immune responses. The development and standardization of in vitro human cell-based assays for functional opsonophagocytic antibodies require critical evaluation and optimization of the preparation of cells for the assay. We report evaluation of a number of protocols with two continuous cell lines (NB-4 and HL-60) for the provision of differentiated cells for use in functional assays. Flow cytometric analysis of CD11b antigen expression, as a marker of differentiation, indicated that all-trans-retinoic acid (ATRA) gave improved differentiation (>80% of cells differentiated at 96 h) when compared with dimethylformamide (DMF) (<60% of cells differentiated at 96 h). Morphological changes during differentiation toward a neutrophil-like phenotype were assessed by scanning electron microscopy. HL-60 and NB-4 cells treated with ATRA showed more spreading and flattening than cells treated with DMF, further evidence that they may have achieved a more differentiated phenotype. The number of cell divisions in culture appeared to be critical because cell lines maintained in exponential growth for >40 passages failed to express CD11b antigen or show morphological changes associated with differentiation after exposure to either differentiation-inducing reagent. Late-passage cells also demonstrated increased tolerance to DMF. Our results indicated that ATRA supplemented with vitamin D(3) and granulocyte colony-stimulating factor affords robust, rapid, and reproducible differentiation of both cell types.

In situ hybridization and immunolabelling study of the early replication of simian immunodeficiency virus (SIVmacJ5) in vivo.

The distribution of virus-infected cells in cynomolgus macaques was determined at 4, 7, 14 and 28 days following intravenous challenge with 1000 TCID(50) of the wild-type simian immunodeficiency virus SIVmacJ5 (stock J5C). At each time-point, pairs of macaques were killed humanely and the presence of SIV was determined and quantified in blood, spleen, peripheral and mesenteric lymph nodes, thymus, lung and ileum by virus co-cultivation with C8166 cells, by quantitative DNA PCR or by in situ hybridization (ISH). At day 4 post-infection (p.i.), detection of the virus was sporadic. By day 7 p.i., however, significant SIV loads were detected in the blood and lymphoid tissues by DNA PCR and virus co-cultivation. Large numbers of cells expressing SIV RNA were detected in mesenteric lymph nodes by ISH and significantly fewer (P<0.05) in the spleen. Significant numbers of ISH-positive cells were also observed in sections of ileum. By day 14 p.i., the distribution of SIV was more even in all lymphoid tissues analysed. By day 28, most of the tissues were negative by ISH, but all remained positive by virus isolation and DNA PCR. Immunolabelling of sections of mesenteric lymph node with monoclonal antibodies specific for SIV envelope and Nef largely confirmed the observations from ISH. These results indicate that, even following intravenous challenge, a major site of the initial replication of SIV is gut-associated lymphoid tissue. Vaccines that induce protection at this site may therefore be superior, even against parenteral challenge.