The extra domain A of fibronectin activates Toll-like receptor 4

Cellular fibronectin, which contains an alternatively spliced exon encoding type III repeat extra domain A (EDA), is produced in response to tissue injury. Fragments of fibronectin have been implicated in physiological and pathological processes, especially tissue remodeling associated with inflammation. Because EDA-containing fibronectin fragments produce cellular responses similar to those provoked by bacterial lipopolysaccharide (LPS), we examined the ability of recombinant EDA to activate Toll-like receptor 4 (TLR4), the signaling receptor stimulated by LPS. We found that recombinant EDA, but not other recombinant fibronectin domains, activates human TLR4 expressed in a cell type (HEK 293 cells) that normally lacks this Toll-like receptor. EDA stimulation of TLR4 was dependent upon co-expression of MD-2, a TLR4 accessory protein. Unlike LPS, the activity of EDA was heat-sensitive and persisted in the presence of the LPS-binding antibiotic polymyxin B and a potent LPS antagonist, E5564, which completely suppressed LPS activation of TLR4. These observations provided a mechanism by which EDA-containing fibronectin fragments promote expression of genes involved in the inflammatory response.

Combined systemic and mucosal immunization with microsphere-encapsulated inactivated simian immunodeficiency virus elicits serum, vaginal, and tracheal antibody responses in female rhesus macaques

We determined the efficacy of immunization with microsphere-encapsulated whole inactivated simian immunodeficiency virus (SIV) by combined systemic and mucosal administration to protect female rhesus macaques against vaginal challenge with homologous rhesus PBMC-grown SIVmac251. Animals in one group were primed and boosted intramuscularly. Two groups were primed intramuscularly and boosted either intratracheally or orally. A final group was primed by vaccinia/rgp140 scarification and subdivided for either intratracheal or oral boosting. Strong ELISA titers of circulating SIV-specific IgG and modest IgA responses were elicited in the animals primed intramuscularly. Intratracheal boosting in the intramuscularly primed macaques resulted in high bronchial alveolar wash (BAW) IgG and less pronounced IgA. SIV-specific vaginal wash (VW) IgG was also present in the intramuscular/intramuscular and intramuscular/intratracheal groups. Vaccinia/rgp140 priming gave low ELISA titers to whole SIV, and failed to elicit mucosal antibody regardless of the booster route. No animal in any group developed serum neutralizing antibody to homologous SIVmac251. On vaginal challenge none of the immunized groups was infected at a lesser frequency than the unimmunized controls. These data suggest that the use of microspheres in a combined parenteral and mucosal regimen is an effective method of eliciting IgG and IgA antibody at mucosal surfaces.

Induction of mucosal antibody responses by microsphere-encapsulated formalin-inactivated simian immunodeficiency virus in a male urethral challenge model

Male rhesus macaques were immunized mucosally with microsphere-encapsulated formalin-inactivated simian immunodeficiency virus (SIV) particles in a test of immunogenicity and protection against mucosal SIV challenge. Tracheal boosting of animals that had been primed intramuscularly resulted in strong serum ELISA titers to SIV, and evidence of local IgA responses in broncho-alveolar washes. The bulk of the antibody response was against non-envelope epitopes. No neutralizing antibody was observed, and intraurethral challenge with cell-free rhesus-grown virus showed no evidence of protection against infection. Microsphere-based immunization efficiently raises local and system responses, but the resulting immunity to SIV is apparently not sufficient to protect against mucosal challenge.

IgG subtype is correlated with efficiency of passive protection and effector function of anti-herpes simplex virus glycoprotein D monoclonal antibodies

IgG subclasses differ in their effector functions in a variety of in vitro assays. To assess the effect of antibody subclass differences on in vivo protective efficacy against herpes simplex virus (HSV), a series of subclass switch mutants was made from an anti-HSV glycoprotein D monoclonal antibody. Purified antibody was examined for the ability to protect against HSV-2 challenge in mice. IgG2a was found to be more effective than IgG1. This correlated both with activity in antibody-dependent cell-mediated cytotoxicity and with efficiency of complement-mediated neutralization. These data suggest that optimization of passive immunization against HSV requires consideration of antibody subclass.

Characterization of recombinant polioviruses expressing regions of rotavirus VP4, hepatitis B surface antigen, and herpes simplex virus type 2 glycoprotein D

Recombinant polioviruses expressing antigens from rotavirus, herpes simplex virus type 2, and hepatitis B virus were generated. Fusion of the heterologous polypeptides to the amino terminus of the poliovirus polyprotein did not prevent myristylation of VP0, suggesting a novel mechanism of myristylation for these recombinant viruses. The effects of the parental genetic background, different foreign sequences, and different insert sizes on growth characteristics were compared. Both the size and the nature of the heterologous sequence appeared to be factors influencing the growth and stability of recombinant polioviruses. All of the recombinants showed a temperature-sensitive phenotype, regardless of the genetic background (attenuated or wild type) from which they were derived. Preliminary studies with transgenic mice carrying the poliovirus receptor gene are discussed.

Baculovirus-expressed herpes simplex virus type 2 glycoprotein D is immunogenic and protective against lethal HSV challenge

Herpes simplex virus type 2 glycoprotein D (gD2) was cloned and expressed in the baculovirus-Spodoptera frugiperda system. Milligram quantities of glycoprotein were recovered from suspension culture and subjected to purification by ion-exchange and immunoaffinity chromatography. The resultant purified gD existed as a homogeneous 57,500 MW monomeric species demonstrating reactivity with anti-gD monoclonal antibodies including those directed at a non-sequential neutralizing epitope of gD. Immunization of Balb/c mice with doses of 0.1-10.0 micrograms of AlPO4-absorbed gD resulted in elicitation of humoral and cellular responses to both HSV1 and HSV2 as well as to purified gD1 and gD2. Immunized mice receiving an infectious dose of 1 x 10(6) p.f.u. of HSV2 via the footpad route were significantly protected against infection at all doses tested when compared with unimmunized AlPO4 and uninoculated control animals.

Effects of in vivo depletion of immunocyte populations on herpes simplex virus glycoprotein D vaccine-induced resistance to HSV2 challenge

BALB/c mice, preimmunized with a protective dose of native herpes simplex virus type 1 glycoprotein D (ngD1) vaccine, were depleted of selected immunocyte populations in vivo using monoclonal antibodies directed at Thy1+, L3T4+, or Lyt2+ cells. Following immunization and depletion, animals were inoculated with varied challenge levels of herpes simplex virus type 2 (HSV2) in the footpad and were monitored for disease. Both depleted undepleted gD-immunized mice were significantly protected when compared with placebo controls. T-cell-independent protection in Thy1 and L3T4-depleted ngD1-immunized animals was effective at low and moderate levels of HSV2 challenge levels, high levels of HSV2 giving high symptom scores in immunized and depleted mice. Depletion of Lyt2+ cells had no significant effect on the outcome of HSV2 infection. Depleted and nondepleted animals also were assessed in parallel for cellular and humoral responsiveness to ngD1 and to HSV antigens in vitro. Lymphoproliferative responses were abrogated in gD-immunized mice treated with anti-Thy1 or anti-L3T4, anti-Lyt2 treatment having little effect. Postimmunization T-cell depletion did not undermine ELISA or neutralizing antibody responses. These findings suggest that at low to moderate levels of virus challenge vaccine-elicited antibody plays a primary role in limiting the severity of infection, T-cell-mediated protective responses being of enhanced significance only at high levels of virus challenge.

Native HSV glycoprotein D subunit vaccine: analysis of in vitro T-cell activation and antigen presentation

Native herpes simplex virus (HSV) glycoprotein D (ngD1) subunit vaccine, a potential human vaccine candidate, was examined to determine responsive murine lymphocyte populations in vitro. This vaccine preparation has been shown to protect against HSV challenge in mice and guinea pigs and to elicit humoral and cellular responses in rodents and primates. Immunized BALB/c mice were used in splenocyte lymphoproliferative studies to analyze the cellular response. After in vivo sensitization, the in vitro proliferative response observed appears to be resultant of Class II-restricted T-cell division in response to gD presented in the context of macrophage-expressed Ia.

Absence of mouse mammary tumor virus proviral amplification in chemically induced lymphomas of RF/J mice

RF/J mice are susceptible to the induction of thymic lymphomas by the carcinogens 3-methylcholanthrene and N-methyl-N-nitrosourea. Given the association of mouse mammary tumor virus (MMTV) with certain thymomas, we examined genomic DNA from chemically induced lymphomas of RF/J mice for new MMTV proviruses. Of 13 tissue culture lines derived from 3-methylcholanthrene-induced tumors, 5 had acquired new proviruses. MMTV amplification coincided with the appearance of viral mRNAs and proteins. However, no primary tumors or animal-passaged tumors contained new proviruses. These observations indicate that MMTV does not have a role in the tumor induction process, although it may become activated and amplified in tissue culture lines derived from tumors.

Genetic control of resistance to 3-methylcholanthrene-induced T-cell lymphoma in mice

Different strains of inbred mice exhibit different levels of susceptibility to T-cell lymphoma induced by the carcinogen 3-methylcholanthrene (MCA). Resistance to MCA-induced lymphoma was dominant over susceptibility in all crosses tested, and in inbred strain mice MCA resistance was found to correlate with resistance to lymphoma induced by a fractionated dose of gamma irradiation. The susceptible RF/J strain was also found to be extraordinarily sensitive to lymphoma induction by low doses of X-irradiation; this low dose sensitivity was also recessive. Experiments on both first and second generation backcross populations supported the hypothesis that a single locus is the main determinant of MCA resistance. Studies examining the possible linkage of low lymphoma incidence to a number of loci failed to establish any clear association, but linkage was seen between the Lyt-2 locus and a significant delay in MCA-induced lymphoma development. We also examined the strain distribution of several activities which might have been expected to have an effect on susceptibility to induced lymphoma. No correlation was seen between resistance and either DNA repair ability, thymic superoxide dismutase levels, or natural killer activity.

Genetically determined resistance to 3-methylcholanthrene-induced lymphoma is expressed at the level of bone marrow-derived cells

Reciprocal bone marrow transfers were performed between mouse strains sensitive or resistant to 3-methylcholanthrene-induced thymic lymphoma. Sensitivity and resistance are properties inherent in bone marrow, and cannot be altered by maturation of marrow in an environment of the opposite phenotype.

Differential susceptibility of cytotoxic and helper T cell precursors to neonatal tolerization to histocompatibility antigens

The ability of various (C57BL/6J X CBA/HT6T6)F1 spleen cell subpopulations to induce tolerance to allogeneic histocompatibility antigens after injection into neonatal CBA/HT6T6 mice was examined. The requirements for tolerization of cytotoxic T lymphocyte precursors (CTLp) and IL 2-producing helper T cell precursors (IL 2Tp) appear to be coordinated but not identical. CTLp frequencies measured in limiting dilution analysis (LDA) were found to be decreased by 90 to 99% in mice injected neonatally with unseparated or a variety of semiallogeneic spleen cell fractions, including T cells, T cell-depleted spleen, the Ig+ and Ig- fractions of nylon-adherent, T-depleted spleen cells, Sephadex-G10 (G10)-nonadherent spleen cells, and T-depleted allogeneic C57BL/6J spleen cells. In contrast, IL 2Tp showed tolerization only after neonatal injection of unseparated or T cell-depleted F1 spleen cells, and not after injection of T or B cells or of G10-nonadherent or T-depleted allogeneic spleen cells. These studies show that the CTLp and IL 2Tp compartments have different requirements for neonatal tolerization, which appear to correlate with the presence of cells expressing class I or class II alloantigens in the inoculum: all spleen cell types tested were capable of tolerizing the CTLp compartment, whereas only whole spleen and T-depleted spleen cells could tolerize IL 2Tp; donor T cells, although capable of inducing CTLp tolerance, are not necessary for either CTLp or IL 2Tp tolerance induction; Ig+ B cells alone are marginally effective in tolerization of IL 2Tp, and G10-nonadherent cells are ineffective, suggesting that macrophages or another type of G10-adherent accessory cell may be required for tolerization of IL 2Tp, although it is not clear whether they are sufficient; and tolerization of CTLp can occur in the presence of a normal IL 2Tp compartment when certain inocula, such as T cells, are used for tolerance induction at birth.

Differential susceptibility of cytotoxic and helper T cell precursors to neonatal tolerization to histocompatibility antigens

The ability of various (C57BL/6J X CBA/HT6T6)F1 spleen cell subpopulations to induce tolerance to allogeneic histocompatibility antigens after injection into neonatal CBA/HT6T6 mice was examined. The requirements for tolerization of cytotoxic T lymphocyte precursors (CTLp) and IL 2-producing helper T cell precursors (IL 2Tp) appear to be coordinated but not identical. CTLp frequencies measured in limiting dilution analysis (LDA) were found to be decreased by 90 to 99% in mice injected neonatally with unseparated or a variety of semiallogeneic spleen cell fractions, including T cells, T cell-depleted spleen, the Ig+ and Ig- fractions of nylon-adherent, T-depleted spleen cells, Sephadex-G10 (G10)-nonadherent spleen cells, and T-depleted allogeneic C57BL/6J spleen cells. In contrast, IL 2Tp showed tolerization only after neonatal injection of unseparated or T cell-depleted F1 spleen cells, and not after injection of T or B cells or of G10-nonadherent or T-depleted allogeneic spleen cells. These studies show that the CTLp and IL 2Tp compartments have different requirements for neonatal tolerization, which appear to correlate with the presence of cells expressing class I or class II alloantigens in the inoculum: all spleen cell types tested were capable of tolerizing the CTLp compartment, whereas only whole spleen and T-depleted spleen cells could tolerize IL 2Tp; donor T cells, although capable of inducing CTLp tolerance, are not necessary for either CTLp or IL 2Tp tolerance induction; Ig+ B cells alone are marginally effective in tolerization of IL 2Tp, and G10-nonadherent cells are ineffective, suggesting that macrophages or another type of G10-adherent accessory cell may be required for tolerization of IL 2Tp, although it is not clear whether they are sufficient; and tolerization of CTLp can occur in the presence of a normal IL 2Tp compartment when certain inocula, such as T cells, are used for tolerance induction at birth.

Specific neonatally induced tolerance to Mls locus determinants

Neonatal injection of CBA/HT6T6 (H-2k, Mlsb) mice with adult, Mls-incompatible (CBA/J [H-2k, Mlsd] X CBA/HT6T6)F1 spleen cells results in the abrogation of cell proliferation and interleukin 2 (IL 2) production in bulk mixed lymphocyte cultures, when spleen cells from the inoculated mice are tested at 6 to 8 wk of age with stimulator cells expressing the Mlsd of the tolerizing inoculum. In limiting dilution assays, this tolerant state was manifested in a 25- to 550-fold (280-fold average) decrease in the frequency of precursors of Mlsd-responsive IL 2-producing T cells. Tolerance was specific in that the frequencies of precursors of IL 2-producing cells responding to Con A, allogeneic H-2d, and self-Ia were not affected. The observed low frequency of Mls-responsive cells was due neither to extensive chimerism resulting in the dilution of Mlsd-responsive cells by the nonresponsive F1 cells of the inoculum, nor to the action of suppressor cells. These findings indicate that neonatal injection of Mls-incompatible spleen cells produces a state of specific tolerance by a clonal deletion or inactivation mechanism. This specific tolerance supports the view that 1) the Mls locus encodes or regulates the expression of defined alloantigenic determinants and 2) Mls-incompatible responder mice have specific receptors for Mls determinants on clonally distributed IL 2-producing responder T cells.

Early loss of precursors of CTL and IL 2-producing cells in the development of neonatal tolerance to alloantigens

Bulk culture and limiting dilution analysis (LDA) were used to follow the ontogeny of the tolerant state in CBA/ HT6T6 mice neonatally tolerized to allogeneic histocompatibility antigens. Advantage was taken of the fact that the lymph nodes (LN) of young mice show immunocompetence before spleen cells do, allowing analysis of actual reactivity as early as 1 wk of age. At 1 wk, the LN cells of mice tolerized i.v. showed a loss of CTL reactivity in bulk culture specific for the tolerizing antigens; a corresponding specific decrease was seen in the frequency of CTL precursors (CTLp). At the same age, however, proliferative responses and interleukin 2 (IL 2) production in MLC were nonspecifically depressed in the tolerized animals. LDA of IL 2 producer precursor frequency (IL- 2Tp ) showed that there was a nonspecific loss of 50% of functional alloreactive IL- 2Tp , accompanied by a larger specific decrease of 90% in the frequency of IL- 2Tp responding to the injected alloantigens. These characteristics of the tolerant state persisted through at least 4 wk of age. Neither the proliferative nor CTL response deficiencies could be overcome by the addition of Con A supernatant containing IL 2. Mixing experiments failed to show evidence of suppressor cell involvement in the loss of the proliferative response. Our results indicate that the specific loss of alloreactivity after tolerization is due to clonal inactivation or deletion of both CTLp and IL- 2Tp , which is obvious as early as 7 days of age. In addition, the differences in the specificity of the clonal inactivation between CTLp and IL- 2Tp suggest the existence of independent mechanisms for tolerization.

Early loss of precursors of CTL and IL 2-producing cells in the development of neonatal tolerance to alloantigens

Bulk culture and limiting dilution analysis (LDA) were used to follow the ontogeny of the tolerant state in CBA/ HT6T6 mice neonatally tolerized to allogeneic histocompatibility antigens. Advantage was taken of the fact that the lymph nodes (LN) of young mice show immunocompetence before spleen cells do, allowing analysis of actual reactivity as early as 1 wk of age. At 1 wk, the LN cells of mice tolerized i.v. showed a loss of CTL reactivity in bulk culture specific for the tolerizing antigens; a corresponding specific decrease was seen in the frequency of CTL precursors (CTLp). At the same age, however, proliferative responses and interleukin 2 (IL 2) production in MLC were nonspecifically depressed in the tolerized animals. LDA of IL 2 producer precursor frequency (IL- 2Tp ) showed that there was a nonspecific loss of 50% of functional alloreactive IL- 2Tp , accompanied by a larger specific decrease of 90% in the frequency of IL- 2Tp responding to the injected alloantigens. These characteristics of the tolerant state persisted through at least 4 wk of age. Neither the proliferative nor CTL response deficiencies could be overcome by the addition of Con A supernatant containing IL 2. Mixing experiments failed to show evidence of suppressor cell involvement in the loss of the proliferative response. Our results indicate that the specific loss of alloreactivity after tolerization is due to clonal inactivation or deletion of both CTLp and IL- 2Tp , which is obvious as early as 7 days of age. In addition, the differences in the specificity of the clonal inactivation between CTLp and IL- 2Tp suggest the existence of independent mechanisms for tolerization.

Analysis by limiting dilution of interleukin 2-producing T cells in murine ontogeny

The ontogeny of interleukin 2 (IL 2) production in young CBA/HT6T6J mice was studied using both bulk culture and limiting dilution methods. The ability of spleen cells in bulk culture to produce IL 2 in response to concanavalin A (Con A) was found to rise through the first 2 weeks of life, from no production at day 1, through 20 units/ml at day 6, to 80-100 units/ml in adults. No evidence for suppression of IL 2 production by young spleen was found. Limiting dilution analysis of both young spleen and young lymph node (LN) shows that young spleen has a much lower complement of cells producing IL 2 in response to Con A or allogeneic stimulation than does adult spleen. The frequency of 6-day spleen cells producing IL 2 in response to Con A is 1/1000, while the adult frequency is approximately 1/50. Young LN, in contrast, has levels of IL 2-producing cells close to those of adult LN, with a frequency of responders to Con A of 1/20. No evidence was found for a deficiency in IL 2 production on a per cell basis, in either 6-day spleen or LN. In examining allogeneic reactivity, a high frequency of cells reacting to strong Mls stimulation was found in both young and adult spleen and LN.