Simultaneous triple-immunogold staining of virus and host cell antigens with monoclonal antibodies of virus and host cell antigens in ultrathin cryosections

Easy and reliable double-immunogold labelling of herpes simplex virus type-1 infected cells using primary monoclonal antibodies and studied by cryosection electron microscopy

Cell biology concerns the interactions between different cellular compartments and between the cell and the environment. The mechanisms of herpes simplex virus type-1 (HSV-1) envelopment and the transport of virus particles and HSV-1 glycoproteins have not been completely investigated. It is of interest to examine the formation of complete virus particles and the cellular distribution of viral glycoproteins correlated with microtubules. The illustration of these conditions by immunocytochemistry is best done by multiple labelling techniques in the same cell. Single-staining of neighbouring serial sections or two-face double-immunolabelling methods are not technically compatible with ultrathin cryosections. The results are reported here of a simultaneous, simple and reliable immunogold double-staining technique using primary antibodies of the same species in ultrathin cryosections. Compared to other inactivation procedures, phosphate-buffered 3% paraformaldehyde plus 2% glutaraldehyde for 2 h at room temperature is an excellent and gentle method to destroy free anti-IgG binding sites on the antibodies and to prevent cross-labelling, which has proven necessary for obtaining reproducible results on cellular distribution of tubulin and viral glycoproteins gD-1 and gC-1.

Herpes simplex virus type 1-infected human embryonic lung cells studied by optimized immunogold cryosection electron microscopy

Herpes simplex virus type 1 (HSV-1) is a common human pathogen of skin and mucous membranes and is potentially dangerous when the infection is disseminated. Viral morphogenesis, especially the mechanism of viral envelopment and the exact pathway for processing and transport of HSV-1 glycoproteins, is still unclear. We report the results of optimized immunogold-labeled cryosection electron microscopy of HSV-1-infected cultured human fibroblasts (MRC-5). The simplified method presented has proved necessary to obtain reproducible results on cellular distribution of viral glycoproteins. It is now possible to demonstrate the viral glycoprotein gD-1, but not gC-1, in the nuclear membranes and to demonstrate gD-1- and gC-1-labeled viral particles in the perinuclear space, and to show the fate of the viral particles in the endoplasmic reticulum and Golgi area in infected cells.

Immunogold labelling of neuroendocrine peptides with special reference to antibody specificity and multiple staining techniques

Immunogold methods have been very important for research on the neuroendocrine system. The compatibility of immunogold probes with optimal contrasting for electron microscopy has made localizations of neuroendocrine peptides to different subtypes of secretory organelles possible and, currently, methods using covalent attachment of nanogold particles to antibodies and neuropeptide ligands hold promise for immunocytochemistry, receptor localizations and in situ hybridizations. Multihormonal phenotypes are a hallmark of both the developing and mature neuroendocrine system. The possibility to localize multiple coexisting messengers by multilabelling immunogold methods is emphasized, and different methods for achieving this are discussed. The most difficult part of immunocytochemistry involves definitions and interpretations of specificity, and a number of limitations and control procedures are discussed.

Backscatter electron imaging of double immunogold labeled erythrocytes using two primary monoclonal IgM antibodies

The majority of mouse monoclonal antibodies reacting with blood group epitopes on erythrocytes are of the IgM class, have equal light chain type, and are available as culture supernatants only. To study the interrelationship of the blood group antigens, a method is presented which allows double labeling applying two unconjugated monoclonal antibodies of the same class and species. The method comprises two indirect, sequential labelings using mouse IgM anti-A and anti-H as primary antibodies and two goat anti-mouse IgM conjugated to 30 and 20 nm colloidal gold particles as secondary antibodies. After labeling for the first antigen, free binding sites on the primary antibody are blocked by incubation with an unconjugated goat anti-mouse antibody. The free anti-species on the secondary antibody, conjugated to 30 nm gold particles, are inactivated by silver enhancement. The silver enhancement also enlarges the gold particle for optimal discrimination between the two particle sizes, which are chosen accordingly. Semiquantitations of double labeled cells from subgroup A2 and A3 were found to be in good agreement with the counts of the corresponding single labelings as well as between experiments, irrespective of which of the two antibodies was applied in the first labeling sequence. The results were in accordance with a reciprocal but nonlinear relationship between the A and H antigens and suggest different affinities of the two antibodies for the epitopes in the subgroups investigated, indicating different biochemistry of the antigen determinants.

Intracellular maturation and sorting of two herpes simplex virus type 1 glycoproteins. Immunogold staining of ultrathin cryosections

Simultaneous immunocytochemical triple staining of ultrathin cryosections of herpes simplex virus type 1-infected cells was carried out using monoclonal antibodies specific for glycoprotein C, glycoprotein D and alpha + beta tubulin. The viral glycoproteins were identified in the cytoplasm, in the Golgi sacs, on the plasma membrane and on the surface of intra- and extracellular virus particles, but not on the nuclear membrane. The glycoproteins identified in the cytoplasm outside the Golgi region were not always confined to the membranes of vesicles, but were often located in close proximity to the tubulin-labelled structures. The glycoproteins C and D were usually codistributed in the cytoplasm, and both accumulated in the Golgi sacs in the same membrane domains. As the glycoproteins occur in close proximity to the microtubular structures, we speculate that these might be directly involved in the intracellular transport of viral glycoproteins.