Evaluation of a ribosomal vaccine against pertussis

Vaccines against fungal infections

The state-of-the-art reached in developing protective immunity against fungal infections through vaccination makes a survey of methodologies and results timely. This review describes experimental vaccinations against dermatophytes, pathogenic yeasts, and dimorphic fungi with special attention to the anti-Coccidioides immitis vaccine, which has reached clinical trials, and to the anti-Candida albicans and anti-Histoplasma capsulatum ribosomal vaccines. Also covered are vaccination experiments in compromised hosts aimed at eliciting acquired resistance to opportunistic fungal infections which constitute risk factors for these hosts. Immunization procedures include live, killed, and attenuated organisms, as well as different subcellular fractions such as cytoplasmic extracts, fungal culture filtrates, cell walls, or ribosomal fractions. A variety of experimental animal models and isolated human trials constitute the subjects in these studies. Acquired immunity has been evaluated through assessment of resistance to infection and determination of specific immune responses. It has been demonstrated that fungal vaccines do elicit both humoral and cell-mediated immunity in the immunized host. For some vaccines (e.g., H. capsulatum), a correlation between the induced immunity and protection was observed and the immunity could be adoptively transferred. In view of the potential of vaccines against fungal infections, a perspective on their applicability, significance, and value for human use is discussed.

Ribonuclease-sensitive ribosomal vaccines

This paper presents an analysis of the protective properties of the components in ribonuclease (RNase)-sensitive ribosomal vaccines, in particular the ribonucleic acid (RNA). The protective activities in mice of purified ribosomes derived from Pseudomonas aeruginosa and from Listeria monocytogenes were compared. Both ribosomal vaccines had to be combined with the adjuvant dimethyldioctadecylammonium bromide (DDA) in order to be protective, and both lost their activity after RNase treatment. The ribosomal vaccines as well as RNA purified from the ribosomes induced non-specific protection. Intraperitoneal injection of RNA with DDA induced an influx of peritoneal cells. Furthermore, RNA with DDA activated macrophages as shown by, a.o., enhanced phagocytic activity and killing capacity for L. monocytogenes. The results suggest that the observed macrophage activation is probably T-cell-independent. With regard to the ribosomal vaccine of P. aeruginosa it is concluded that RNA also contributed to the protective activity by increasing the humoral response against suboptimal concentrations of contaminating cell surface antigens. In conclusion, it is proposed that ribosomal vaccines may be considered as a combination of a non-specific immunomodulator (RNA) with pathogen-specific cell surface antigens. This concept of ribosomal vaccines is discussed in relation to the literature concerning RNase-sensitive ribosomal vaccines.

Immunogenicity of transfer RNA isolated from a two-heptose rough mutant of Salmonella typhimurium LT2 in mouse typhoid infection

Transfer ribonucleic acid (tRNA) was isolated from a two-heptose mutant of Salmonella typhimurium LT2 (strain SL1004) and was found to afford 100% mouse protection against challenge with 1000 LD50 of strain LT2. The intraperitoneal minimum effective dose of tRNA was 5 micrograms RNA per mouse and this dose was significantly lower than that of ribosomal RNA for ddY mouse strain. The protective immunity was independent of the presence of antibodies to cell-surface antigens, and was transferred mainly by T cells. The protective moiety of tRNA was sensitive to ribonuclease digestion which resulted in 85% reduction in the mouse survival rate, but was completely resistant to protease digestion. The present study demonstrates that the immunogenic activity of salmonella RNA is present in both ribosomal RNA and tRNA.

Candida albicans-induced agglutinin and immunoglobulin E responses in mice

Mice varied in their ability to make detectable antibody responses to cell surface determinants of Candida albicans depending upon the antigen preparation and the immunization schedule used. Immunoglobulin M (IgM) appeared to be the major class of antibody responsible for the C. albicans-agglutinating activity of the immune sera. Various inbred strains of mice injected with a ribosomal fraction from C. albicans produced a low titer (average, 4 to 8) of yeast cell agglutinins and a higher titer (64 to 512) of IgE antibodies detected by passive cutaneous anaphylaxis (PCA) in rats. The two kinds of antibodies appeared to be specific for different antigens because the agglutinin, but not IgE, could be removed by absorbing the serum with a polysaccharide from the cell wall of C. albicans, but the polysaccharide did not provoke the PCA reaction. C. albicans-specific IgE antibodies showed cross-reactivity (PCA) with ribosomal antigens from a strain of C. albicans and C. tropicalis, but PCA reactions could not be elicited with similar antigen preparations from other yeast species. IgE responses were also detected in over 20% of the mice infected intravenously or intraperitoneally with live C. albicans.

Immunogenic dialyzable factor derived from a ribosomal fraction of Salmonella typhimurium. II. Isolation and characterization of the protective moiety in the dialyzable factor

An immunogenic dialyzable factor was obtained by dialysis of the freeze-thawed ribosomal fraction derived from a smooth virulent strain (LT2) of Salmonella typhimurium. Ion exchange chromatography of the dialyzable factor on Dowex 1-X2 (Cl- form) demonstrated the presence of four peaks and the fourth peak eluted with 0.4 M NaCl in 0.005 N HCl was found to be necessary for protection. This effective peak was not obtained by chromatography of nonprotective dialyzable factors such as an RNase digest. Dowex chromatography of the dialyzable factors isolated from rough mutants of strain LT2 revealed that the dialyzable factor of strain SL1004 whose live vaccine is capable of inducing protective immunity contained fairly large amounts of peak IV. DEAE-cellulose for two-dimensional thin layer chromatography was used to identify the composition of the dialyzable factor and peak IV. Eight spots were located under ultraviolet light and seven spots were characterized by their absorption ratios. In peak IV, four nucleotides were located and identified by comparison with a map of the original dialyzable factor. The data show that the effective components of the dialyzable factor are mixed nucleotides and may be unique to ribonucleic acids of strains of S. typhimurium in which live vaccines are capable of affording mouse protection.

Serotype-nonspecific protection induced by ribonucleic acid isolated from the ribosomal vaccine of Pseudomonas aeruginosa

A ribosomal vaccine of Pseudomonas aeruginosa and a vaccine containing purified lipopolysaccharide (LPS) were compared with respect to their capacity to protect mice against a lethal challenge with P. aeruginosa. The route of vaccination appeared to be important for the protective activity of the ribosomal vaccine. Optimal protection was measured if both the immunizing and the challenge injection were given intraperitoneally. The ribosomal vaccine protected mice as early as 1 day after vaccination, and the protection lasted at least 6 days. LPS-specific antibodies were detectable 6 but not 2 days after vaccination. The ribosomal vaccine protected mice also against a heterologous serotype of Pseudomonas. Injection of purified LPS did not protect mice earlier than at day 3, and the protection induced by LPS was serotype specific. Ribonucleic acid (RNA) isolated from the ribosomal vaccine had the same protective properties as the ribosomes. RNA induced serotype-nonspecific protection as quickly as 1 day after injection, and the protection lasted at least 6 days. However, the capacity to induce antibodies to LPS was lost or reduced. It is concluded that the serotype-nonspecific protection induced by RNA and the serotype-specific protection induced by LPS are due to different mechanisms. Experiments with combined vaccines containing RNA and LPS demonstrated that the addition of RNA to LPS resulted in a slight increase in LPS-specific antibodies. The data presented indicate that both the serotype-specific protection induced by LPS and the serotype-nonspecific protection induced by RNA contribute to the protective activity of the ribosomal vaccine.

Evidence for the presence of lipopolysaccharide in a ribonuclease-sensitive ribosomal vaccine of Pseudomonas aeruginosa

To obtain information about the nature of the immunogens in the ribosomal vaccine (fraction II) of Pseudomonas aeruginosa, we studied the specificity of rabbit antibodies to fraction II. Crossed immunoelectrophoresis demonstrated the presence of antibodies which precipitated with ribosomal antigens, but not with lipopolysaccharide (LPS). By means of an enzyme-linked immunosorbent assay, antibodies to LPS were detected in antibodies to fraction II. Antibodies to fraction II could protect mice against a lethal challenge with P. aeruginosa. Absorption experiments demonstrated that the protective ability of antibodies to fraction II was due to antibodies to cell envelope antigens, whereas antibodies to ribosomal antigens did not contribute to the protection. Antibodies to LPS could be detected in mice 1 week after a single vaccination with fraction II. It was concluded that the protective activity of fraction II was due, at least in part, to the presence of LPS in the ribosomal vaccine. Treatment of fraction II with ribonuclease decreased the protective activity of the ribosomal vaccine. Addition of synthetic polyadenylic acid-polyuridylic acid restored the protective activity of ribonuclease-treated fraction II, indicating that RNA in the ribosomal vaccine might act as an adjuvant or a carrier in the presentation of the of the contaminating cell envelope antigens. The protective activity and the toxicity of fraction II were compared with the protective activity and the toxicity of fraction I, which contained cell envelope components, including LPS, and of purified LPS. The results indicated that protection by the ribosomal vaccine was associated with a slightly higher toxicity than was protection by fraction I, whereas purified LPS was the most toxic vaccine.

Protective immunity against murine candidiasis elicited by Candida albicans ribosomal fractions

Candida albicans ribosomes were prepared from mechanically disrupted cells through differential centrifugation and purification in a sucrose-ammonium sulfate solution. The ribosomes were analyzed chemically and physically and exhibited characteristics of eucaryotic ribosomes (78S). ICR female mice were immunized with two subcutaneous inoculations, 2 weeks apart, of 100 microgram of ribosomes (expressed as ribosomal protein). Immunized mice were challenged either intraperitoneally or intravenously with a lethal dose of live C. albicans cells. The 31-day survival rate of immunized mice challenged intraperitoneally was 64% (mean value) versus 27% in controls; in intravenously challenged mice the survival rate of the immunized animals was about 60%, with no survivors among the controls. In intravenously challenged mice, incomplete Freund adjuvant enhanced the protection elicited by the ribosomes. Protection by ribosomal immunization was obtained against challenge doses causing chronic and acute infection.