Antibody-Mediated Protection against Genital Herpes Simplex Virus type 2 Disease in Mice by Fc gamma Receptor -Dependent and -Independent Mechanisms (41.8)

The requirement for Ab -Fcγ receptor (FcγR) interactions or for virus neutralization in protection against genital HSV-2 challenge was examined. Serum IgG Ab isolated from HSV-immune mice protected normal mice against HSV-2 disease when administered prior to challenge. However, protection was significantly diminished in mice lacking the γ chain subunit utilized in FcγRI, FcγRIII, FcγRIV, and FcεRI and in normal mice depleted of FcγR+, Gr-1+ immune cells suggesting protection was largely mediated by an FcγR-dependent mechanism. To test if FcγR-independent antibody-mediated mechanisms might manifest protection differently, a highly neutralizing, HSV glycoprotein D -specific monoclonal antibody (mAb) was utilized. Administration of IgG1, IgG2a, or IgG2b switch variants of the mAb did not prevent infection of the genital tract but resulted in lower virus loads in the vaginal epithelium and provided significant protection against disease and acute infection of the sensory ganglia independently of host FcγR expression. Together, these data demonstrate two distinct antibody effector mechanisms capable of providing substantial protection against genital HSV-2 disease. The presence of either FcγR -dependent Ab or strongly neutralizing Ab did not completely prevent HSV-2 infection but limited initial infection of genital and neuronal tissues and diminished HSV-2 disease. NIH Grants AI42815 and AI054444.

Herpes simplex virus DNA vaccine efficacy: effect of glycoprotein D plasmid constructs

The impact of vaccination with plasmid DNA encoding full-length glycoprotein D (gD) from herpes simplex virus (HSV) type 2 (gD2), secreted gD2, or cytosolic gD2 was evaluated in mice and guinea pigs. Immunization with plasmids encoding full-length gD2 or secreted gD2 produced high antibody levels, whereas immunization with DNA encoding cytosolic gD2 resulted in significantly lower antibody titers in both species (P<.001). Vaccination with DNA encoding full-length or secreted gD2 significantly reduced acute disease in mice and guinea pigs (both P<.001) and subsequent recurrent disease in guinea pigs (P<.05). In guinea pigs, immunization with DNA encoding cytosolic gD2 did not protect from acute or recurrent disease, whereas in mice it did protect, but not as well as DNA encoding full-length or secreted gD2. None of the vaccines resulted in improved virus clearance from the inoculation site, and none significantly reduced recurrent disease when used as a therapeutic vaccine in HSV-2-infected guinea pigs.

Secretagogue-triggered transfer of membrane proteins from neuroendocrine secretory granules to synaptic-like microvesicles

The membrane proteins of all regulated secretory organelles (RSOs) recycle after exocytosis. However, the recycling of those membrane proteins that are targeted to both dense core granules (DCGs) and synaptic-like microvesicles (SLMVs) has not been addressed. Since neuroendocrine cells contain both RSOs, and the recycling routes that lead to either organelle overlap, transfer between the two pools of membrane proteins could occur during recycling. We have previously demonstrated that a chimeric protein containing the cytosolic and transmembrane domains of P-selectin coupled to horseradish peroxidase is targeted to both the DCG and the SLMV in PC12 cells. Using this chimera, we have characterized secretagogue-induced traffic in PC12 cells. After stimulation, this chimeric protein traffics from DCGs to the cell surface, internalizes into transferrin receptor (TFnR)-positive endosomes and thence to a population of secretagogue-responsive SLMVs. We therefore find a secretagogue-dependent rise in levels of HRP within SLMVs. In addition, the levels within SLMVs of the endogenous membrane protein, synaptotagmin, as well as a green fluorescent protein-tagged version of vesicle-associated membrane protein (VAMP)/synaptobrevin, also show a secretagogue-dependent increase.

Regulation of the macrophage vacuolar ATPase and phagosome-lysosome fusion by Histoplasma capsulatum

Histoplasma capsulatum (Hc) maintains a phagosomal pH of about 6.5. This strategy allows Hc to obtain iron from transferrin, and minimize the activity of macrophage (Mo) lysosomal hydrolases. To determine the mechanism of pH regulation, we evaluated the function of the vacuolar ATPase (V-ATPase) in RAW264.7 Mo infected with Hc yeast or the nonpathogenic yeast Saccharomyces cerevisae (Sc). Incubation of Hc-infected Mo with bafilomycin, an inhibitor of the V-ATPase, did not affect the intracellular growth of Hc, nor did it affect the intraphagosomal pH. In contrast, upon addition of bafilomycin, phagosomes containing Sc rapidly changed their pH from 5 to 7. Hc-containing phagosomes had 5-fold less V-ATPase than Sc-containing phagosomes as quantified by immunoelectron microscopy. Furthermore, Hc-containing phagosomes inhibited phagolysosomal fusion as quantified by the presence of acid phosphatase, accumulation of LAMP2, and fusion with rhodamine B-isothiocyanate-labeled dextran-loaded lysosomes. Finally, in Hc-containing phagosomes, uptake of ferritin was equivalent to phagosomes containing Sc, indicating that Hc-containing phagosomes have full access to the early "bulk flow" endocytic pathway. Thus, Hc yeasts inhibit phagolysosomal fusion, inhibit accumulation of the V-ATPase in the phagosome, and actively acidify the phagosomal pH to 6.5 as part of their strategy to survive in Mo phagosomes.

Cloning and functional expression of a tetrabenazine sensitive vesicular monoamine transporter from bovine chromaffin granules

Using oligonucleotide primers derived from the vesicular monoamine transporters sequences, a cDNA predicted to encode the bovine chromaffin granule amine transporter has been cloned (b-VMAT2). Surprisingly, its structure is more similar to the rat brain transporter (VMAT2), than to the rat adrenal counterpart (VMAT1). Unlike rat VMAT1, bovine VMAT2 appears to be expressed both in the adrenal medulla and the brain, as judged by Northern analysis. After modification/deletion of the seven amino acids at the N-terminus of the protein it was expressed in a functional form. The order of affinity of the bovine VMAT2 transporter to substrates is: serotonin > dopamine = norepinephrine > epinephrine. Also, the recombinant bovine adrenal transporter is highly sensitive to tetrabenazine, in sharp contrast to the rat adrenal transporter. The findings indicate, therefore, a clear species variation in which structure and function of the bovine adrenal transporter resemble the rat brain protein, while its tissue distribution is distinct from both types of rat proteins. In addition, the predicted protein sequence is identical to the experimentally determined N-terminus sequence of the purified vesicular amine transporter [Stern-Bach et al. (1992) Proc. Natl. Acad. Sci. USA 89, 9730-9733].

Structure and expression of subunit A from the bovine chromaffin cell vacuolar ATPase

Subunit A of the vacuolar H(+)-ATPase class is thought to be responsible for the ATP hydrolysis which drives proton-pumping. We report here the cloning and sequence determination of the first mammalian cDNA encoding a bovine vacuolar ATPase subunit A from an adrenal medulla cDNA library. Northern blots of bovine adrenal medulla RNA reveal a message of approximately 3.8 kb. The predicted peptide sequence, consisting of 618 amino acids with a calculated molecular weight of 68397 daltons, is similar to the sequences of the three known subunit A proteins. beta-Galactosidase-subunit A fusion proteins were immuno-decorated by an antiserum raised to the subunit A protein from corn coleoptile vacuoles.

An immunoreactive 8-azido ATP-labeled protein common to the lysosomal and chromaffin granule membrane

The H+-ATPases of eukaryotic cell organelles, including the rat liver lysosomal (tritosomal) H+-ATPase and the bovine chromaffin granule ATPase, exhibit similarities in function, substrate requirements, and inhibitor responses. We have explored the possibility that these pumps also exhibit immunological similarities, and that common determinants may be present on polypeptides important to function, such as ATP binding. Toward this end, antibodies were produced in rabbits against a highly purified, detergent-solubilized and fractionated chromaffin granule proton pump preparation. This antibody reacted with a 70-80 kDa protein of the lysosomal membrane on Western blots. We have previously shown that photolysis with 8-azido-ATP inhibits lysosomal N-ethylmaleimide-sensitive, vanadate-, ouabain- and oligomycin-insensitive ATP hydrolysis and H+ transport, with concomitant labeling of a 70-80 kDa membrane protein, amongst others. Here, we report that the photolysis with 8-azido-ATP also leads to inhibition of chromaffin granule H+ pump function and pump-related ATP hydrolysis, with concomitant N-ethylmaleimide-sensitive, ATP-protectable, 8-azido-[alpha-32P]ATP labeling. The anti-chromaffin granule antibody reacts with an approx. 70 kDa protein of the chromaffin granule and the lysosome. This raises the possibility that the 70 kDa 8-azido-ATP-reactive, immunologically similar proteins may play a similar role in pump function such as ATP binding and/or hydrolysis in these organelles.