The glycoprotein isolated from vesicular stomatitis virus is mitogenic for mouse B lymphocytes.

The glycoprotein (G protein) of VSV was purified from the intact virion by Triton X-100 extraction. The isolated G protein has been shown to be a T cell-independent, B lymphocyte mitogen and polyclonal activator. Neither G protein nor the intact virion are stimulatory for murine T lymphocytes. The greater the density of G protein in lipid vesicles or the degree of aggregation of isolated G protein, the more highly stimulatory it is for murine splenocytes. As G protein is spread out in artificial vesicles, it becomes less mitogenic. It is probable that other viral components are also stimulatory since the Triton-insoluble pellet and VSV from which the G protein has been enzymatically removed retain mitogenic activity. To out knowledge, this is the first time a purified viral component has been demonstrated to be lymphocyte mitogen.

Dopa inhibits induced proliferative activity of murine and human lymphocytes.

L-DOPA, the product of enzymatic hydroxylation of L-tyrosine, is released by melanotic melanoma cells in vivo and in vitro. Here we report that DOPA at pharmacologically relevant micromolar doses dramatically inhibits the stimulation of DNA synthesis by lipopolysaccharide and concanavalin A in murine splenocytes and human lymphocytes, having little or no effect on unstimulated (control) lymphocytes or proliferating fibroblasts. Therefore we propose that melanogenically active melanoma cells can inhibit the host's immune response via the release of DOPA and/or its oxidation products.

Mitogenic activity of Sindbis virus and its isolated glycoproteins.

Purified preparations of Sindbis virus, a member of the togavirus family, are mitogenic for lymphocytes from a number of different mouse strains. Cell separation techniques, as well as studies using lymphocytes from the congenitally athymic BALB/c nu/nu mouse, showed that Sindbis virus is a T-cell-independent B-cell mitogen. Additionally, the envelope glycoproteins of Sindbis virus, isolated by Triton X-100 extraction and butanol precipitation, stimulated lymphocytes to incorporate five times as much [3H]thymidine into their DNA as did the Sindbis virion. These results are similar to those previously reported for vesicular stomatitis virus and herpes simplex virus types I and II and for the purified glycoproteins of vesicular stomatitis virus and influenza virus.

Sendai virus glycoproteins are T cell-dependent B cell mitogens.

UV-inactivated Sendai virus is mitogenic for murine splenocytes, whereas infectious Sendai virus kills spleen cells in vitro. The isolated hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins of Sendai virus are also mitogenic for cultured mouse spleen cells. A mixture of these glycoproteins (1 microgram/well) gives maximum stimulation 96 h after culture initiation. Viral proteins remaining insoluble after Triton X-100 extraction are also mitogenic for mouse spleen cells, with maximum stimulation occurring at 72 h after culture initiation with 1 to 5 microgram/well. On the basis of protein concentration, the HN and F glycoproteins are approximately three times more mitogenic than the Triton X-100-insoluble material. The mitogenic response of the HN and F glycoproteins has two components, a T cell-independent B cell proliferation, which is less than one-half of the total stimulation observed, and a T cell-dependent B cell proliferation. In contrast, the Triton X-100-insoluble material is a T cell-dependent B cell mitogen. Purified T lymphocytes do not respond to the mitogenic signal of either HN-F or Triton X-100-insoluble material.

Activation of mouse lymphocytes by vesicular stomatitis virus.

Vesicular stomatitis virus (VSV) is a mitogen for mouse spleen cells, and infectious virus is not required for mitogenesis. At concentrations between 10 and 100 microgram per culture, VSV stimulated DNA synthesis and blast transformation. Maximal activation by VSV occurred 48 h after culture initiation. Spleen cells depleted of T-lymphocytes by treatment with anti-Thy 1.2 and complement and those obtained from congenitally athymic BALB/c nu/nu mice were activated by VSV, suggesting that VSV is a B-cell mitogen. Activation of spleen cells was independent of the host in which the virus was grown, since VSV grown in BHK-21, HKCC, or MDBK cells was mitogenic. The mitogenesis was specific for VSV, since MDBK cell-grown WSN influenza virus was not a mitogen in this in vitro activation system, VSV-specific antibody prevented VSV mitogenesis, and VSV was mitogenic for spleen cells from C3H/HeJ mice which were resistant to mitogenesis by endotoxin.

Role of intrastructural/intermolecular help in immunization with peptide-phospholipid complexes.

The design of effective subunit vaccines requires the inclusion of both B and T cell epitopes. The best mechanism for including both types of epitopes within an Ag is dependent upon how the Ag is processed by the APC for presentation to a responsive Th cell. If it is more efficient to process a single molecule for both helper and primary epitopes, than covalent linkage of B cells and T cell epitopes for intramolecular presentation of help would be recommended. If however, separate peptides containing either B or Th cell epitopes could be included within a single complex for the elicitation of intermolecular/intrastructural help, more antigenically diverse structures could be designed. This paper reports that it is possible to generate intermolecular/intrastructural help within an antigenic peptide-phospholipid (PL) complex. These peptide-PL complexes use well defined epitopes from Plasmodium falciparum as Ag. In addition to generating intrastructural help, we have shown that the Ir to these peptide-PL complexes is controlled by Ir genes and is similar to the Ir to the circumsporozoite protein of this pathogen.

Intranasal immunization with proteoliposomes protects against influenza.

Worldwide, influenza virus remains a serious disease which has successfully eluded numerous attempts to design a consistently effective vaccine. In part, these attempts have been thwarted because of a lack of basic understanding of the mechanisms which mediate protection and recovery from influenza infection. A better understanding of the roles of secretory antibody, serum antibody and cell mediated immunity vis-à-vis protection and recovery from influenza infection has allowed us more rationally to approach the design and administration of a vaccine for influenza. We have constructed a vaccine composed of glycoproteins from the envelopes of either influenza of Sendai virus embedded in a lipid bilayer (immunosomes) mimicking the presentation of the virus to the cells during natural infection. Intranasal immunization with these immunosomes induces an adequate systemic Ir compared with intramuscular immunization and a superior local IgA response. These animals were specifically protected from virus challenge.

Defining minimal requirements for antibody production to peptide antigens.

The role that individual determinants play in modulating the immune response of an organism to a pathogen is often obscured because of the complexity of the pathogen. In order to gain a better appreciation of the role of individual determinants in the immune response, a pathogen may be dissociated into smaller components, for example peptides representing specific epitopes. These isolated components are often poorly immunogenic and historically have required the use of adjuvants to stimulate antibody production. This report defines the minimal essential requirements for antibody production to a peptide in this system. These are the ability to stimulate both B- and T-helper lymphocytes, anchorage in a phospholipid complex and multivalency within the complex. When these conditions are met, no additional adjuvants are necessary. This procedure has allowed us to identify three distinct T-helper cell epitopes from HIV gp160. In addition, this information has been used to produce a simple, totally synthetic and highly immunogenic preparation for the production of antibodies to peptides.