Humoral response in Treponema pallidum-infected guinea pigs: I. Antibody specificity

Young male inbred strain 2 guinea pigs were infected intradermally with 8 X 10(7) Treponema pallidum extracted from a rabbit orchitis, and 5 months later reinfected with 10(7) T. pallidum. Ninety percent of the animals developed symptomatic lesions after initial infection but none on challenge. Immunoblotting of sera obtained at intervals after infection or reinfection showed antibodies against T. pallidum antigen (TP), nonpathogenic treponemes--T. phagedenis biotype Reiter (TR), T. refringens strain Noguchi (TN), and T. vincentii (TV)--as well as normal rabbit serum (NRS) and normal rabbit testes extract (NRT). Antibodies reacting with TP were detected as early as 17 days (five polypeptides) and steadily rose (at 3 months 17 polypeptides were seen). Cross-reacting antibodies to TR, TN, TV, or rabbit proteins decreased within 3 to 5 months. After reinfection, the antibodies to NRS increased more sharply than the anti-treponemal antibodies. Adsorption with TR and NRS of sera obtained after infection or reinfection produced a reduction of antibodies to TP by 75-87%.

Humoral response in Treponema pallidum-infected guinea pigs. II. Circulating immune complexes and autoimmune responses

Guinea pigs of inbred strain 2 and of a strain deficient in complement component 4 (C4D) responded to intradermal infection with Treponema pallidum by production of antibodies to treponemal antigens, normal rabbit serum proteins, fibronectin, and creatine kinase and with formation of circulating immune complexes (IC). IC started to appear at low concentrations 1 mo after infection and increased between 3 and 5 mo post-infection. Antibodies to fibronectin appeared after the second month but were not detectable 30 days later. Antibody activity to creatine kinase was detectable at the fourth month and became significantly higher at 5 mo post-infection. Reinoculation with a dose similar to that used for primary infection caused a significant increase in all antibodies and IC. Dissociation products of IC formed after primary infection consisted predominantly of treponemal antibodies and antigens, whereas IC detected after reinfection consisted predominantly of antibodies and normal rabbit serum proteins. Antibodies to fibronectin and creatine kinase are considered autoantibodies, and the underlying mechanism responsible for their production in syphilis is discussed.

Humoral response in Treponema pallidum-infected guinea pigs. II. Circulating immune complexes and autoimmune responses

Guinea pigs of inbred strain 2 and of a strain deficient in complement component 4 (C4D) responded to intradermal infection with Treponema pallidum by production of antibodies to treponemal antigens, normal rabbit serum proteins, fibronectin, and creatine kinase and with formation of circulating immune complexes (IC). IC started to appear at low concentrations 1 mo after infection and increased between 3 and 5 mo post-infection. Antibodies to fibronectin appeared after the second month but were not detectable 30 days later. Antibody activity to creatine kinase was detectable at the fourth month and became significantly higher at 5 mo post-infection. Reinoculation with a dose similar to that used for primary infection caused a significant increase in all antibodies and IC. Dissociation products of IC formed after primary infection consisted predominantly of treponemal antibodies and antigens, whereas IC detected after reinfection consisted predominantly of antibodies and normal rabbit serum proteins. Antibodies to fibronectin and creatine kinase are considered autoantibodies, and the underlying mechanism responsible for their production in syphilis is discussed.

Natural antibodies to treponemal antigens in four strains of guinea-pigs

A total of 185 serum samples obtained from healthy male and female guinea-pigs of inbred strains 2 and 13 and outbred strains C4D and Hartley A were examined for natural antibodies to treponemal antigens by ELISA using Treponema pallidum (TP), T. phagedenis biotype Reiter (TR) and T. vincentii (TV) antigens and by the FTA test. The prevalence and titres of natural antibodies depended on the age and strain of guinea-pig and the treponemal antigen used. One- and 7-day-old guinea-pigs contained significantly (P less than 0.001) higher levels of natural antibodies than did animals 1 or 3-6 months old. The similar high levels of natural antibodies in newborn guinea-pigs and their mothers (12-30 months old) and the sharp drop observed at the age of 1 month suggested maternal transfer as the mechanism of acquisition. In young adults 3-6 months old, the age group most susceptible to TP infection, antibodies to TP and TR were at their lowest levels, but antibodies reacting to TV had already begun to rise. Natural antibodies were of the IgG1 and IgG2 but not of the IgM class. The highest levels of natural antibodies were in the C4D guinea-pigs; the lowest were in the Hartley A strain. Natural antibody activity was inhibited or adsorbed by TR antigens.

The mechanism of action of lymphokines. VII. Modulation of the action of macrophage migration inhibitory factor by antioxidants and drugs affecting thromboxane synthesis

Guinea pig peritoneal exudate macrophages are active producers of oxygen radicals in response to membrane stimulation. We examined the involvement of oxygen radicals in the inhibition of macrophage migration caused by the lymphokine, macrophage migration inhibitory factor (MIF). It was found that the presence of scavengers of superoxide and hydrogen peroxide did not influence MIF action. Exogenous horseradish peroxidase, however, significantly enhanced the migration inhibitory effect of MIF. Among six scavengers of hydroxyl radicals and singlet oxygen that were tested, L-methionine (20-80 mM) and L-histidine (40-80 mM) were capable of preventing MIF action. Macrophage responsiveness to MIF was also blocked by the lipid antioxidant propyl gallate (0.125-0.25 mM). Lymphokine-induced inhibition of migration could not be prevented by inhibitors of phospholipase A2, cyclooxygenase, or lipoxygenase. The inhibiting of thromboxane synthetase, however, by imidazole, 1-benzylimidazole and the prostaglandin endoperoxide analogs U-51605 and U-44069 effectively prevented MIF action. These findings are compatible with the hypothesis that the inhibiton of macrophage migration by MIF is the result of reversible autotoxic damage by a yet unidentified product of the oxidative burst, possibly hypochlorous acid. Thromboxane also appears to be involved in MIF action probably by its adhesiveness increasing and proaggregatory actions. The intracellular target of the autotoxic attack and the relative importance of oxygen-derived products and thromboxane in the mediation of MIF-induced migration inhibition are unknown.

Effect of N-(phosphonacetyl)-L-aspartate on 5-azacytidine metabolism in P388 and L1210 cells

The effect of N-phosphonacetyl-L-aspartate (PALA) pretreatment on the metabolism and cytotoxicity of 5-azacytidine (5-aza-Cyd) was studied in two murine leukemic cell lines. Exposure of P388 and L1210 cells to 3 mM PALA for 3 hr before adding 5-aza-Cyd at 75 microM was accompanied by a two-fold increment in acid-soluble and 3-fold increment in acid-insoluble incorporation of 5-aza-Cyd in both cell lines. RNA incorporation of 5-aza-Cyd increased from 97.5 +/- 3.4 pmol 5-aza-Cyd per microgram D-ribose in control cells to 299.2 +/- 4.2 pmol 5-aza-Cyd per microgram D-ribose in PALA-treated cells; a smaller increment in DNA incorporation of 5-aza-Cyd was also noted. Sequential treatment of cells with PALA and 5-aza-Cyd was associated with a 40% reduction in protein synthesis compared to only a 2 and 8% reduction, respectively, produced by the drugs given alone. Sequential administration of PALA and 5-aza-Cyd resulted in greater than additive cytotoxicity as measured by both growth inhibition and in vitro soft-agar cloning assays. Exposure of both cell lines to 3 mM PALA for 3 hr produced 50 and 65% reductions in intracellular levels of cytidine triphosphate and uridine triphosphate; intracellular accumulation of 5-azacytidine triphosphate, the lethal metabolite of 5-aza-Cyd, increased from 43.4 +/- 2.1 pmol/10(6) cells to 92.4 +/- 3.3 pmol/10(6) cells in PALA-treated cells. PALA was able to augment the metabolism and cytotoxicity of 5-aza-Cyd in a uridine-cytidine kinase-mutant 5-aza-Cyd-resistant L5178Y subline. This sequential drug combination has a rational biochemical basis and may offer significant advantages over either drug when administered alone, especially in cells which are resistant to 5-aza-Cyd.