Review of current preclinical testing strategies for bacterial vaccines

A wide variety of bacterial vaccines is in various stages of preclinical and clinical development. These products range from whole killed or live attenuated bacterial organisms to purified proteins, peptides and plasmid DNA. Although preclinical strategies may be directed by a set of common guidelines focused on demonstrating safety and biological activity, the exact developmental scheme will depend on product-specific characteristics. In general, preclinical data should support the proposed clinical formulation and include detailed information on the source and quality of starting materials, manufacturing processes, characterization of bacterial seed stocks, potency, general safety, purity, and identity. Data describing product validation and testing may be appropriate depending on the type of product, e.g., genetic stability for recombinant constructs, details on inactivation or attenuation methods for organisms or toxins, demonstration of potency of combination products, and safety and toxicology studies of plasmid DNA vaccines or vaccines with novel adjuvants. The choice of dose, route, and formulation to be used clinically may be greatly affected by rigorous preclinical developmental strategies.

Public health implications of emerging vaccine technologies

The field of public health and medicine stands to benefit immensely from the emerging vaccine technologies and improved application of existing technologies. Technological advances may promote: (1) greater flexibility and simplicity in the design and operation of immunization campaigns or ongoing prevention programs, including reduction in number of vaccine doses, cold chain elimination, slow-release/prolonged antigenic stimulation, reduced cost and hazard and increased ease of administration through noninvasive, oral delivery systems, greater population levels of immunization and health; (2) the development of documents by FDA, WHO, and other regulatory authorities and groups, to assist the manufacturer in the appropriate manufacturing, preclinical, and clinical development of these new vaccines; (3) a greater array of vaccines to protect the civilian and military populations; (4) increased vaccine potency; (5) vaccines eliciting mucosal immunity, cytotoxic T cells, and/or neutralizing antibody. At the end of the 20th century there remain many unconquered pathogens and noninfectious indications for which medical science suggests that vaccines could be effective. New technologies may provide the best hope to address this wide array of public health needs.

Protection of immunized and previously infected chimpanzees challenged with Mycoplasma pneumoniae

Following immunization, peak geometric mean serum metabolism inhibition antibody (MIT) titres were 1:13 and 1:16 for groups of three chimpanzees each that received either the formalin-inactivated OSU-1A or experimental acellular extract vaccine, respectively. Following challenge, the mean titres for chimpanzees given the acellular vaccine peaked at 1:256 in 4 weeks and was 1:48 at 10 weeks. Chimpanzees given the OSU-1A vaccine peaked at 1:80 in 4 weeks and remained at 1:80 at 10 weeks. There was no direct correlation between the serum MIT response and the severity of disease or colonization, and thus the MIT response was not a reliable measurement of protection. The two non-immunized chimpanzees showed significant signs of disease, including cough, pharyngitis, rhinitis, fever and abnormal X-ray findings, for about 5 weeks. The chimpanzees immunized with either vaccine were less colonized and showed far less disease than non-immunized controls. Protection afforded the chimpanzees was similar to that of vaccinees in the human clinical trial given the same OSU-1A vaccine (Wenzel et al., 1977). The two previously infected chimpanzees were most protected against colonization and disease on challenge.

Experimentally induced septic arthritis in chimpanzees infected with Mycoplasma hominis, Mycoplasma pneumoniae, and Ureaplasma urealyticum

Mycoplasma hominis was isolated in pure culture from septic synovial aspirates from an individual (patient A) during 16 different bouts of exacerbation over a 70-month period of observation. Two isolates, 10(7) and also 10(6) color-changing units (CCU) of the 1620 isolate and 5 x 10(4) CCU of the 1628 isolate, caused inflammation in chimpanzees inoculated intraarticularly. Inflammation was also induced with 10(7) CCU of the 2010B isolate, serovar VII of Ureaplasma urealyticum, recovered from an agammaglobulinemic individual (patient B) with septic polyarthritis and with 3 x 10(6) CCU of the PI-1428 isolate of Mycoplasma pneumoniae. Inflammation persisted for up to 36 days and was self-limiting. The aspirates contained up to 220,000 white blood cells/mm3 and up to 10(7) CCU/mL. There was good correlation between the severity of inflammation and the numbers of organisms, but antibody was not detected in aspirates during the peak severity of disease. As the numbers of organisms, decreased, detectable levels of antibody increased, thus suggesting that antibody may have been bound to antigen. Chimpanzees previously infected with either the 1628 isolate of M. hominis or the 2010B isolate of U. urealyticum were protected on challenge with > 100 times the minimal dose causing arthritis. Chimpanzees showed little or no inflammation when inoculated intraarticularly with 5 x 10(8) CCU of the type strain PG-21 of M. hominis or with the type strain CO of U. urealyticum or when inoculated intravenously with 3 x 10(8) CCU of the arthrogenic 1620 isolate of M. hominis.

Experimentally induced Mycoplasma pneumoniae pneumonia in chimpanzees

Eight chimpanzees were examined. Two served as negative control and six inoculated with Mycoplasma pneumoniae became colonized. Colonization persisted for 28-68, 16-50 and 21 days with an average duration of 47, 32.5 and 21 days in the oropharyngeal, tracheal and lung tissues, respectively. Mycoplasma titers ranged from 10(8) to 10(1) color-changing units per specimen during the course of the infections. Seroconversion occurred within 12-15 days and peak antibody titers ranged from 1.256 to 1.1024 and developed between days 28 and 48 post-inoculation. Positive cold agglutinin titers were detected between 12 to 15 days and peak titers ranged from 1:80 to 1:640. Significant increases in sIgA and IgG immunoglobulin antibody levels were detected in lung lavage fluids. Unlike the many other experimentally infected animals examined, chimpanzees infected with M. pneumoniae had positive X-ray findings, developed cold agglutinins and showed overt signs of disease. These signs include persistent cough, low grade fever, rhinitis, oropharyngitis, diarrhea, and loss of appetite. Peak severity of disease corresponded with peak lung colonization, and the detection of cold agglutinins and positive X-ray findings. The microbiological, serological and clinical aspects of pneumonia induced in chimpanzees was similar to naturally occurring primary atypical pneumonia in humans.

The role of a 40-megadalton plasmid in the adherence and hemolytic properties of Aeromonas hydrophila

A cured strain of Aeromonas hydrophila, MS-2PC, was examined for phenotypic changes in antibiotic resistance, adherence, and hemolysis. Parental strain MS-2 was resistant to ampicillin, novobiocin, and carbenicillin; MS-2PC, which lacked a 40-MDa plasmid, was also resistant to ampicillin but was sensitive to novobiocin and carbenicillin. The adherence of these isolates to CaCo-2 and HeLa cells was examined. MS-2PC demonstrated greater attachment to both cell lines than did strain MS-2 (p < 0.05). MS-2PC also demonstrated greater hemolysis activity than did MS-2 (p < 0.01). The 40-Mda plasmid was isolated and reintroduced into MS-2PC. The resulting transformant, 20T, regained resistance to carbenicillin and novobiocin. The attachment ability of 20T was equal to that of MS-2, and both strains demonstrated significantly lower attachment ability than that of MS-2PC (p < 0.01). Strains MS-2 and 20T exhibited the same hemolysis pattern, which was markedly less than that of strain MS-2PC. These results indicate that the 40-Mda plasmid which codes for antibiotic resistance also controls other functions of A. hydrophila MS-2.

Biological activities of monoclonal antibodies to Mycoplasma pneumoniae membrane glycolipids

A purified preparation of membranes was obtained by using a unique method of treating Mycoplasma pneumoniae with the ATPase inhibitor, diethylstilbestrol. This method was shown to yield highly purified membranes with little or no cytoplasmic contamination. These membranes were used to immunize mice for subsequent productions of monoclonal antibodies (MAbs). Hybridoma culture supernatants were screened by enzyme-linked immunosorbent assay with whole-cell M. pneumoniae and lipid extract antigens. Four stable MAbs were obtained and characterized. MAb CP3-46F5 reacted with a protein of a molecular weight of approximately 52,000 as determined by Western blot (immunoblot). MAbs CP3-50C2, CP3-53C5, and CP3-53C8 did not react with any antigens on Western blots but did bind to at least 10 distinct glycolipid bands as determined by orcinol staining on thin-layer chromatograms of M. pneumoniae lipid extracts. The MAbs did not react with similarly prepared lipid extracts from Mycoplasma genitalium, Mycoplasma neurolyticum, and Mycoplasma gallisepticum. These MAbs did not inhibit M. pneumoniae metabolism or attachment to WiDr cell cultures. The anti-glycolipid MAbs recognize determinants specific to M. pneumoniae, unlike polyclonal hyperimmune sera against M. pneumoniae, which cross-react with lipid extracts of M. genitalium.

Hamster challenge potency assay for evaluation of Mycoplasma pneumoniae vaccines

A hamster immunization challenge assay described in the accompanying paper (M. F. Barile, D. K. F. Chandler, H. Yoshida, M. W. Grabowski, R. Harasawa, and S. Razin, Infect. Immun. 56:2443-2449, 1988) was used to examine protection against Mycoplasma pneumoniae disease by passive immunization and to evaluate the protective potency of a Formalin-inactivated whole-cell and a cell extract M. pneumoniae vaccine. Passive immunization with a globulin fraction of hyperimmune mule antiserum to M. pneumoniae provided hamsters some protection against the challenge. When hamsters were actively immunized, a single dose of Formalin-inactivated vaccine provided only minimal protection, whereas multiple doses of this vaccine, particularly when combined with adjuvant, provided good protection. A single dose of the cell extract vaccine did not protect animals, but two doses caused a marked reduction of disease when a priming dose was given intraperitoneally, followed by a booster dose intratracheally. The correlation between the level of metabolism inhibition antibodies to M. pneumoniae in the sera of vaccinated hamsters and the degree of protection as measured by reduction of lung pathological scores and colonization was poor, indicating that seroconversion rates for metabolism inhibition antibodies are not by themselves adequate to measure the potency of M. pneumoniae vaccines.

Parameters of Mycoplasma pneumoniae infection in Syrian hamsters

An animal model for evaluating the potency of Mycoplasma pneumoniae vaccines was developed with hamsters. Factors that influence hamster infection by M. pneumoniae were defined, and parameters for assessment of intensity of pulmonary disease were established. Colonization of hamster lungs was determined by culture, and intensity of lung disease was assessed histopathologically and expressed numerically as a lung pathological score. Intratracheal inoculation of the challenge was superior to the intranasal or aerosol route for inducing a consistent degree of lung disease. A challenge dose of 10(6) CFU inoculated intratracheally produced lung colonization and significant reproducible lung pathological scores in essentially all unvaccinated animals. The peak of infection, as determined by these criteria, was at about 2 weeks after challenge. Animals over 6 weeks of age were preferable for the test, since younger animals exhibited a lower lung pathological score even though they showed the same degree of lung colonization. The hamster assay developed provides a dependable experimental system for testing the protective potency of M. pneumoniae vaccines.

Presence of anaplerotic reactions and transamination, and the absence of the tricarboxylic acid cycle in mollicutes

Cell extracts of the fermentative Mollicutes Acholeplasma laidlawii B-PG9, Acholeplasma morum S2, Mycoplasma capricolum 14, Mycoplasma gallisepticum S6, Mycoplasma pneumoniae FH, Mycoplasma hyopneumoniae J and M. genitalium G-37, and the non-fermentative Mycoplasma hominis PG-21, Mycoplasma hominis 1620 and Mycoplasma bovigenitalium PG-11 were examined for 39 cytoplasmic enzyme activities associated with the tricarboxylic acid (TCA) cycle, transamination, anaplerotic reactions and other enzyme activities at the pyruvate locus. Malate dehydrogenase (EC 4.2.1.2) was the only TCA-cycle-associated enzyme activity detected and it was found only in the eight Mycoplasma species. Aspartate aminotransferase (EC 2.6.1.1) activity was detected in all Mollicutes tested except M. gallisepticum S6. Malate synthetase (EC 4.1.3.2) activity, in the direction of malate formation, was found in the eight Mycoplasma species, but not in any of the Acholeplasma species. Phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) was detected in the direction of oxaloacetate (OAA) formation in both Acholeplasma species, but not in any of the Mycoplasma species. Pyruvate carboxylase (EC 6.4.1.1), pyruvate kinase (EC 2.7.1.40), pyruvate dehydrogenase (EC 1.2.4.1) and lactate dehydrogenase (EC 1.1.1.27) activities were found in all ten Mollicutes tested. No activities were detected in any of the ten Mollicutes for aspartase (EC 4.3.1.1), malic enzyme (EC 1.1.1.40), PEP carboxytransphosphorylase (EC 4.1.1.38), PEP carboxykinase (EC 4.1.1.32) or pyruvate orthophosphate dikinase (EC 2.7.9.1). In these TCA-cycle-deficient Mollicutes the pyruvate-OAA locus may be a point of linkage for the carbons of glycolysis, lipid synthesis, nucleic acid synthesis and certain amino acids. CO2 fixation appears obligatory in the Acholeplasma species and either CO2 fixation or malate synthesis appears obligatory in the Mycoplasma species.

Superiority of the chimpanzee animal model to study the pathogenicity of known Mycoplasma pneumoniae and reputed mycoplasma pathogens

As far as we know, humans are the only known natural hosts for M. pneumoniae disease. Whereas volunteer studies have provided useful data on the pathogenesis of disease and efficacy of vaccines, experimentally inducing disease in humans raises serious ethical questions and has become increasingly difficult to defend. Thus, there is a genuine need for a satisfactory animal model to study M. pneumoniae disease. Using the cotton rat and developing chick embryo models, Eaton and co-workers (9-13) have clearly shown that the infectious "Eaton agent" was the cause of primary atypical pneumonia. After the causative agent was identified as M. pneumoniae (14), more definite and quantitative studies were possible. The hamster animal model has provided most of our information on the pathogenicity of strains, the pathogenesis of disease and the potency of inactivated vaccines. However, protective data obtained in hamsters immunized with the TS mutant vaccines did not correlate with data obtained in humans, raising concern regarding the use of the hamster animal model to evaluate the potency of live TS vaccines. The chimpanzee animal model has a number of advantages. Chimpanzees become clinically ill, show positive X-ray findings, and develop cold agglutinin titers. In fact, the experimentally induced disease in chimpanzees is remarkably similar to naturally occurring primary atypical pneumonia in patients. Because of the close genomic relationship, immunologic reagents prepared and used for human studies can also be used successfully in chimpanzee studies. The chimpanzee model also has some serious disadvantages. They are expensive to house and maintain and are generally not available to the scientific community. Nonetheless, chimpanzees are probably the best, most meaningful animal models established thus far to examine the infectious process, the immune response and the pathogenesis of this disease and to determine approaches to effective therapy and immunization of diseases produced by known pathogens, like M. pneumoniae, as well as reputed mycoplasma pathogens, such as M. genitalium and M. hominis.

Mycoplasma pneumoniae attachment to glutaraldehyde-treated human WiDr cell cultures

Attachment of Mycoplasma pneumoniae to host cells initiates disease, and the attachment components may represent important protective immunogens for preventing disease. We have studied the mechanisms of attachment using in vitro cell culture systems and selected pathogenic and nonpathogenic strains of M. pneumoniae. Attachment of the pathogenic strains M129 and PI-1428 was several fold greater than attachment of the nonpathogenic strain, and attachment of strains M129 and PI-1428 was reduced by 21 to 63% when human WiDr cell monolayers were exposed to neuraminidase, supporting the concept that M. pneumoniae attaches to mammalian cells by a neuraminidase-sensitive glycoconjugate. While attachment of the two pathogenic strains was markedly reduced by treating the WiDr cells with glutaraldehyde, glutaraldehyde treatment produced minimal effects on the attachment of the nonpathogenic strain B176. Glutaraldehyde treatment also altered the temperature dependence of attachment by the pathogenic strains. Because glutaraldehyde-treated WiDr cell monolayers showed little difference in attachment between pathogenic and nonpathogenic strains, glutaraldehyde-treated cells are not appropriate cell substrates for studying M. pneumoniae attachment mechanisms or identifying immunogens for vaccine development.

Survey of immunoglobulin A protease activity among selected species of Ureaplasma and Mycoplasma: specificity for host immunoglobulin A

Because immunoglobulin A (IgA) is the predominant immunoglobulin at mucosal surfaces, IgA proteases produced by pathogenic bacteria are considered potential virulence factors for organisms that cause disease or gain entry at mucous membranes. To determine the role of IgA protease in the pathogenicity of mycoplasmal disease, a variety of human and animal mycoplasma and ureaplasma species were examined for IgA protease activity with human, murine, porcine, and canine IgA. None of the mycoplasma species examined showed detectable IgA protease activity with any of the IgAs tested. Twenty-eight strains of Ureaplasma urealyticum isolated from human urogenital tissues cleaved human IgA1, but no cleavage of human IgA2 or murine, porcine, or canine IgA was observed. Ureaplasmas isolated from nonhuman hosts (feline, canine, avian, and bovine [Ureaplasma diversum]) did not cleave human IgA1. Two strains of canine ureaplasmas were able to cleave canine IgA, but not murine IgA. Thus, ureaplasmas from other species can produce IgA protease, but the specificity of the enzyme was restricted to the IgA of the appropriate host. This finding suggests that IgA proteases could play a role in the selective host specificity of mucosal pathogens.

Competitive inhibition and attachment assays in cell cultures to detect pathogenic binding components of mycoplasmas: a review

A microattachment assay for quantitating adherence of radiolabelled Mycoplasma pneumoniae to human WiDr cell culture monolayers is described. Preincubating the WiDr cell monolayers with a protein-rich extract of M. pneumoniae inhibited the subsequent attachment of radiolabelled organisms. Competitive attachment inhibition provided a quantitative procedure to determine M. pneumoniae-binding components in the extract. The microattachment assays also measured attachment inhibition by the sialoglycoconjugates ceruloplasmin, orosomucoid and gangliosides, indicating that these reagents may be structural analogues of the mammalian cell receptor. Attachment of virulent M. pneumoniae strains to glutaraldehyde-treated monolayers was reduced approximately 60% and showed a different temperature dependence compared with untreated cells. These results suggest that maximal attachment of virulent M. pneumoniae may require two or more different receptors and binding components.

Mycoplasma hominis- tissue cell interactions: a review with new observations on phenotypic and genotypic properties

Strains of Mycoplasma hominis isolated from different tissues of patients with a variety of disease processes and from cell culture substrates show marked phenotypic and genotypic heterogeneity, as determined by their antigenic and isozyme properties and by [3H]DNA-DNA hybridization and DNA cleavage pattern analyses. Strains isolated from the same tissues (blood of postpartum patients or human urogenital tract or cell culture substrates) have very high genomic homology and form clusters of similar strains. Clusters of strains that colonize similar specialized urogenital tissues may initiate diseases that reflect damage to the particular tissue colonized. Antigenic markers such as those for attachment components for different strain clusters may help determine the role, if any, played by strain differences in the etiology of a family of urogenital diseases.

Mycoplasma pneumoniae attachment to WiDr cell cultures: competitive inhibition assays

Attachment of radiolabeled M. pneumoniae to human WiDr cell culture monolayers was dependent on the WiDr cell density and the concentration of M. pneumoniae. Saturation of confluent monolayers grown on 5 mm coverslips was attained with only 40 micrograms of M. pneumoniae protein. Preincubating the WiDr monolayers with unlabeled M. pneumoniae or with a protein-rich extract prepared from M. pneumoniae inhibited subsequent attachment of radiolabeled organisms. Attachment inhibition by the M. pneumoniae extract provided a quantitative assay for mycoplasmal binding components. Treatment of radiolabeled M. pneumoniae with orosomucoid, ceruloplasmin, and gangliosides inhibited attachment to WiDr cells. These sialoglycoconjugates may be structural analogues of the target cell receptor.

Genomic and phenotypic analyses of Mycoplasma pneumoniae strains

Mycoplasma pneumoniae strains PI-1428, M129, B176, FH, and MAC were analyzed for homology by DNA-DNA hybridization, thermal elution midpoints of the DNA-DNA heteroduplexes, DNA cleavage patterns with restriction endonucleases, and protein gel electrophoretic profiles. These properties were compared with biological assays, such as antigenic reactivity with reference antisera in the growth inhibition and metabolic inhibition tests, as well as the ability to attach to human WiDr cell cultures. The avirulent, nonhemadsorbing strain B176 could be differentiated from the others by diminished attachment capacity to WiDr cells and by slightly reduced DNA homology. The other strains appeared to be identical when examined by these procedures. No significant differences were detected among any of the strains by the metabolic inhibition or growth inhibition tests. The DNA cleavage patterns of the five strains were also similar, although strains FH and MAC differed from the other three strains in a few bands. These results demonstrate that these five strains are similar and that the species M. pneumoniae is remarkably homogeneous.

Mycoplasma pneumoniae attachment: competitive inhibition by mycoplasmal binding component and by sialic acid-containing glycoconjugates

Attachment of Mycoplasma pneumoniae to human WiDr cell culture monolayers was examined by using radiolabeled M. pneumoniae. The amount of attachment was proportional to the density of the WiDr cells and to the concentration of M. pneumoniae in the assay. Saturation of the monolayers was achieved with 40 micrograms of virulent strain M129 per assay, whereas binding of avirulent strain B176 was 70% less than that of strain M129. A competitive attachment inhibition assay was used to measure specific binding component activity. Attachment was inhibited when WiDr cells were pretreated with unlabeled virulent strain M129, whereas avirulent noncytadsorbing strain B176 did not inhibit attachment as well as the virulent strain. A protein-rich extract prepared from virulent, cytadsorbing strains of M. pneumoniae also inhibited attachment. The amount of inhibition was dependent on the amount of extract used, and units for binding component activity in the extract were calculated from the competitive attachment inhibition assays. The competitive attachment inhibition assay was also used to investigate the nature of the receptor site on the WiDr cells. Attachment was inhibited when the radiolabeled M. pneumoniae suspensions were pretreated with human sialoglycoproteins, such as orosomucoid and ceruloplasmin, and bovine gangliosides. These findings support the present concept that the mammalian receptor site for M. pneumoniae is a sialic acid-containing glycoprotein.

Attachment of Mycoplasma pneumoniae to hamster tracheal organ cultures, tracheal outgrowth monolayers, human erythrocytes, and WiDr human tissue culture cells

Virulent strains of Mycoplasma pneumoniae, PI-1428 and M129, were radiolabeled wtih [3H]palmitic acid or [3H]thymidine and examined for attachment to hamster tracheal organ cultures, tracheal outgrowth monolayers, human O-positive erythrocytes, and human WiDr carcinoma cell cultures. Although attachment to each cell substrate was readily detected, the WiDr cell culture monolayers provided the most satisfactory substrate for quantitating mycoplasma attachment. Serious technical limitations were encountered with each of the other substrates that we examined; these limitations interfered with reproducibility or sensitivity and rendered tracheal organ cultures and erythrocyte suspensions unsuitable for routine attachment and attachment inhibition assays. Moreover, the WiDr cell monolayer was the most sensitive substrate for determining attachment inhibition activity in protein-containing extracts prepared from M. pneumoniae. The significance of these findings is discussed.

Inactivation of galactosyltransferase by lactoperoxidase and N-acetylimidazole

Galactosyltransferase (UDPgalactose:D-glucose 4-beta-D-galactosyltransferase, EC 2.4.1.22) was totally inactivated by iodination with lactoperoxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7). Substrates protected against inactivation. The presence of 10 mM Mn2+ and 1 mM UDPgalactose gave partial protection which was enhanced by the addition of 10 mM N-acetylglucosamine, but not by glucose. These results are consistent with a conformational change upon binding of UDPgalactose. Only monoiodotyrosine and diiodotyrosine were identified in the pronase digest of iodinated galactosyltransferase. Galactosyltransferase was also inactivated with N-acetylimidazole and partial activity was restored by treating acetylated galactosyltransferase with hydroxylamine. These results suggest that tyrosine(s) is essential for galactosyltransferase activity.

Ciliostatic, hemagglutinating, and proteolytic activities in a cell extract of Mycoplasma pneumoniae

An extract of Mycoplasma pneumoniae, prepared from glass-grown organisms by extraction with 2 M NaCl, followed by freeze-thaw, ultracentrifugation, dialysis, and lyophilization, yielded approximately 20% of the total mycoplasmal protein. The extract contained at least 20 protein bands on sodium dodecyl sulfate-polyacrylamide gels and 2 to 5% carbohydrate and inhibited 70 to 100% of the ciliary activity of hamster tracheal organ cultures (ciliostasis). The extent of ciliostasis was dependent on the concentration of the extract. The extract also produced hemagglutination of human O-positive erythrocytes and showed proteolytic activity with a synthetic tetrapeptide substrate, S-2222. These in vitro tissue-damaging activities may be associated with the virulence of the mycoplasmas and with the pathogenesis of M. pneumoniae disease.

Interaction of bovine platelets with bovine glomerular basement membrane

The interaction of bovine platelets with bovine glomerular basement membrane has been studied by aggregometry, transmission and scanning electron microscopy and measurement of [3H] serotonin release. In the absence of added calcium platelets adhere to basement membrane but fail to undergo the release reaction or aggregation. In the presence of 0.2-0.5 mM calcium release of serotonin and complete aggregation of the platelets are observed when sufficient basement membrane is present. Platelets were strongly adhered to the basement membrane surface, the platelet surface in the aggregates closely following the surface of the basement membrane. Platelet morphology in aggregates with basement membrane closely resembled that of platelets from collagen-induced aggregates. Basement membrane differed from collagen in its requirement for calcium for the aggregation and release reactions. In addition purified basement membrane was 1.5-3 fold less active on a weight basis than bovine tendon collagen in promoting aggregation.

Human alveolar macrophages: antigen-independent binding of lymphocytes

To characterize the initial step in alveolar macrophage (AM)-lymphocyte (L) interaction in the human lung, we studied the ability of human AM to bind autologous blood L in vitro in the absence of antigen. AM were obtained by saline bronchial lavage through a fiberoptic bronchoscope. Monolayers of AM attached to glass bound autologous blood L prepared by Ficoll-Hypaque and nylon wool column separation. The AM-L binding increased from zero time to a maximum at 2 h and then declined to a zero time value at 18 h. The binding was dependent on the number of L added to the AM monolayers, with greatest binding at an AM:L ratio of 1:50. AM:L binding required viability of AM, but not of L, and was temperature dependent. Pretreatment of AM with iodoacetic acid, trypsin, neuraminidase, or colchicine diminished attachment of L at 2 h. Neuraminidase pretreatment of L resulted in increased binding to nontreated AM. Thus, a physical interaction between human AM and autologous peripheral blood L can occur in vitro in the absence of known antigen; similar interaction in vivo may play a role in the generation of cell-mediated immune responses in the lung.