Neutron-encoded diubiquitins to profile linkage selectivity of deubiquitinating enzymes

Deubiquitinating enzymes are key regulators in the ubiquitin system and an emerging class of drug targets. These proteases disassemble polyubiquitin chains and many deubiquitinases show selectivity for specific polyubiquitin linkages. However, most biochemical insights originate from studies of single diubiquitin linkages in isolation, whereas in cells all linkages coexist. To better mimick this diubiquitin substrate competition, we develop a multiplexed mass spectrometry-based deubiquitinase assay that can probe all ubiquitin linkage types simultaneously to quantify deubiquitinase activity in the presence of all potential diubiquitin substrates. For this, all eight native diubiquitins are generated and each linkage type is designed with a distinct molecular weight by incorporating neutron-encoded amino acids. Overall, 22 deubiquitinases are profiled, providing a three-dimensional overview of deubiquitinase linkage selectivity over time and enzyme concentration.

Serum N-Glycomic Biomarkers Predict Treatment Escalation in Inflammatory Bowel Disease

Biomarkers to guide clinical decision-making at diagnosis of inflammatory bowel disease (IBD) are urgently needed. We investigated a composite serum N-glycomic biomarker to predict future disease course in a discovery cohort of 244 newly diagnosed IBD patients. Forty-seven individual glycan peaks were analysed using ultra-high performance liquid chromatography identifying 105 glycoforms from which 24 derived glycan traits were calculated. Multivariable logistic regression was performed to determine associations of derived glycan traits with disease. Cox proportional hazard models were used to predict treatment escalation from first-line treatment to biologics or surgery (hazard ratio (HR) 25.9, p=1.1×10-12; 95% confidence interval (CI), 8.52-78.78). Application to an independent replication cohort of 54 IBD patients yielded a HR of 5.1 (p=1.1×10-5; 95% CI, 2.54-10.1). These data demonstrate the prognostic capacity of serum N-glycan biomarkers and represent a step towards personalized medicine in IBD.

Large-Scale Analysis of Apolipoprotein CIII Glycosylation by Ultrahigh Resolution Mass Spectrometry

Apolipoprotein-CIII (apo-CIII) is a glycoprotein involved in lipid metabolism and its levels are associated with cardiovascular disease risk. Apo-CIII sialylation is associated with improved plasma triglyceride levels and its glycosylation may have an effect on the clearance of triglyceride-rich lipoproteins by directing these particles to different metabolic pathways. Large-scale sample cohort studies are required to fully elucidate the role of apo-CIII glycosylation in lipid metabolism and associated cardiovascular disease. In this study, we revisited a high-throughput workflow for the analysis of intact apo-CIII by ultrahigh-resolution MALDI FT-ICR MS. The workflow includes a chemical oxidation step to reduce methionine oxidation heterogeneity and spectrum complexity. Sinapinic acid matrix was used to minimize the loss of sialic acids upon MALDI. MassyTools software was used to standardize and automate MS data processing and quality control. This method was applied on 771 plasma samples from individuals without diabetes allowing for an evaluation of the expression levels of apo-CIII glycoforms against a panel of lipid biomarkers demonstrating the validity of the method. Our study supports the hypothesis that triglyceride clearance may be regulated, or at least strongly influenced by apo-CIII sialylation. Interestingly, the association of apo-CIII glycoforms with triglyceride levels was found to be largely independent of body mass index. Due to its precision and throughput, the new workflow will allow studying the role of apo-CIII in the regulation of lipid metabolism in various disease settings.

N-Linked Glycans in the Variable Domain of IgG Anti-Citrullinated Protein Antibodies Predict the Development of Rheumatoid Arthritis

OBJECTIVE

Anti-citrullinated protein antibodies (ACPAs) are disease-specific biomarkers in rheumatoid arthritis (RA). More than 90% of IgG ACPAs harbor N-linked glycans in the antibody variable (V) domain. The corresponding N-glycosylation sites in ACPA V-region sequences result from somatic hypermutation, a T cell-dependent process. As ample evidence indicates that T cells drive the maturation of the ACPA response prior to arthritis onset, we undertook this study to investigate whether the presence of glycans in IgG ACPA V domains predicts the transition from predisease autoimmunity to overt RA.

METHODS

We analyzed 2 independent sets of serum samples obtained from 126 ACPA-positive first-degree relatives (FDRs) of RA patients. Both sets originated from an Indigenous North American population and comprised cross-sectional and longitudinal samples of individuals who did or did not develop inflammatory arthritis. Serum IgG ACPAs were affinity-purified and subjected to ultra high-performance liquid chromatography-based glycan analysis.

RESULTS

In both data sets, FDR-derived IgG ACPA displayed markedly lower levels of V domain glycans (<50%) compared to IgG ACPA from RA patients. Notably, FDRs who later developed RA showed extensive V-domain glycosylation before the onset of arthritis. Moreover, IgG ACPA V-domain glycosylation was strongly associated with future development of RA (hazard ratio 6.07 [95% confidence interval 1.46-25.2]; P = 0.013).

CONCLUSION

Extensive glycosylation of the IgG ACPA V domain is present in a subset of predisposed FDRs of Indigenous North American RA patients. The presence of this feature substantially increases the risk of RA development. Based on these findings, we propose that glycosylation of the IgG ACPA V domain represents a predictive marker for RA development in ACPA-positive individuals and may serve to better target prevention measures.

Galactosylation and Sialylation Levels of IgG Predict Relapse in Patients With PR3-ANCA Associated Vasculitis

OBJECTIVE

The objective of our study is to investigate the Fc glycosylation profiles of both antigen-specific IgG targeted against proteinase 3 (PR3-ANCA) and total IgG as prognostic markers of relapse in patients with Granulomatosis with Polyangiitis (GPA).

METHODS

Seventy-five patients with GPA and a PR3-ANCA rise during follow-up were included, of whom 43 patients relapsed within a median period of 8 (2-16) months. The N-glycan at Asn297 of affinity-purified and denatured total IgG and PR3-ANCA was determined by mass spectrometry of glycopeptides in samples obtained at the time of the PR3-ANCA rise and at the time of the relapse or time-matched during remission.

RESULTS

Patients with total IgG1 exhibiting low galactosylation or low sialylation were highly prone to relapse after an ANCA rise (HR 3.46 [95%-CI 1.73-6.96], p<0.0001 and HR 3.22 [95%-CI 1.52-6.83], p=0.002, respectively). In relapsing patients, total IgG1 galactosylation, sialylation and bisection significantly decreased and fucosylation significantly increased from the time of the PR3-ANCA rise to the relapse (p<0.0001, p=0.0087, p<0.0001 and p=0.0025), while the glycosylation profile remained similar in non-relapsing patients. PR3-ANCA IgG1 galactosylation, sialylation and fucosylation of PR3-ANCA IgG1 decreased in relapsing patients (p=0.0073, p=0.0049 and p=0.0205), but also in non-relapsing patients (p=0.0007, p=0.0114 and p=0.0002), while bisection increased only in non-relapsing patients (p<0.0001).

CONCLUSION

While Fc glycosylation profiles have been associated with clinically manifest autoimmune diseases, in the present study we show that low galactosylation and sialyation in total IgG1 but not PR3-ANCA IgG1 predicts disease reactivation in patients with GPA who experience an ANCA rise during follow-up. We postulate that glycosylation profiles may be useful in pre-emptive therapy studies using ANCA rises as guideline.

High-Throughput Analysis of IgG Fc Glycopeptides by LC-MS

This chapter contains a nanoscale liquid chromatography-mass spectrometry method for the glycoform profiling of the conserved Fc N-glycosylation site of monoclonal and polyclonal immunoglobulin G (IgG). It describes in detail LaCyTools, a program for automated data (pre-)processing of the obtained LC-MS data. The minimal sample preparation necessary is explained as well as an optional method for affinity purification of (polyclonal) antibodies from serum or plasma.After (optional) affinity purification, the pure IgG is cleaved with trypsin. The tryptic glycopeptides are separated almost exclusively on their peptide backbone. This ensures similar response factors for all glycoforms in the MS detection and allows the collection of separate glycoform profiles for different IgG isoforms or allotypes. LaCyTools automatically performs label-free (relative) quantitation of the obtained data after minimal manual input and additionally calculates several quality criteria which can be used for data curation at the level of both individual analytes and entire LC-MS runs.

MALDI-TOF-MS reveals differential N-linked plasma- and IgG-glycosylation profiles between mothers and their newborns

During pregnancy, the mother provides multiple nutrients and substances to the foetus, with maternal immunoglobulin G (IgG) being actively transported to the foetus. Newborns depend on maternal IgG for immune-protection in their first months. The glycosylation of IgG has been shown to influence its dynamics, e.g. receptor binding. While minor differences in IgG glycosylation have been found between IgG derived from maternal blood and umbilical cord blood (UC) of newborn children, the differential glycosylation of maternal and UC plasma has hitherto not been studied. Here, we studied the N-glycosylation of IgG and total plasma proteome of both maternal and UC plasma of 42 pairs of mothers and newborn children. A total of 37 N-glycans were quantified for IgG and 45 for the total plasma N-glycome (TPNG). The study showed slightly higher levels of galactosylation for UC IgG than maternal IgG, confirming previous results, as well as lower bisection and sialylation. Furthermore, the TPNG results showed lower values for galactosylation and sialylation, and higher values for fucosylation in the UC plasma. In conclusion, this study presents some novel insights into IgG glycosylation differences as well as the first broad overview of the differential plasma glycosylation between mothers and newborns.

Variation of Human Salivary O-Glycome

The study of saliva O-glycosylation is receiving increasing attention due to the potential of glycans for disease biomarkers, but also due to easy access and non-invasive collection of saliva as biological fluid. Saliva is rich in glycoproteins which are secreted from the bloodstream or produced by salivary glands. Mucins, which are highly O-glycosylated proteins, are particularly abundant in human saliva. Their glycosylation is associated with blood group and secretor status, and represents a reservoir of potential disease biomarkers. This study aims to analyse and compare O-glycans released from whole human mouth saliva collected 3 times a day from a healthy individual over a 5 days period. O-linked glycans were released by hydrazinolysis, labelled with procainamide and analysed by ultra-high performance liquid chromatography with fluorescence detection (UHPLC-FLR) coupled to electrospray ionization mass spectrometry (ESI-MS/MS). The sample preparation method showed excellent reproducibility and can therefore be used for biomarker discovery. Our data demonstrates that the O-glycosylation in human saliva changes significantly during the day. These changes may be related to changes in the salivary concentrations of specific proteins.

LaCyTools: A Targeted Liquid Chromatography-Mass Spectrometry Data Processing Package for Relative Quantitation of Glycopeptides

Bottom-up glycoproteomics by liquid chromatography-mass spectrometry (LC-MS) is an established approach for assessing glycosylation in a protein- and site-specific manner. Consequently, tools are needed to automatically align, calibrate, and integrate LC-MS glycoproteomics data. We developed a modular software package designed to tackle the individual aspects of an LC-MS experiment, called LaCyTools. Targeted alignment is performed using user defined m/z and retention time (tr) combinations. Subsequently, sum spectra are created for each user defined analyte group. Quantitation is performed on the sum spectra, where each user defined analyte can have its own tr, minimum, and maximum charge states. Consequently, LaCyTools deals with multiple charge states, which gives an output per charge state if desired, and offers various analyte and spectra quality criteria. We compared throughput and performance of LaCyTools to combinations of available tools that deal with individual processing steps. LaCyTools yielded relative quantitation of equal precision (relative standard deviation <0.5%) and higher trueness due to the use of MS peak area instead of MS peak intensity. In conclusion, LaCyTools is an accurate automated data processing tool for high-throughput analysis of LC-MS glycoproteomics data. Released under the Apache 2.0 license, it is freely available on GitHub ( https://github.com/Tarskin/LaCyTools ).

Dopant Enriched Nitrogen Gas Combined with Sheathless Capillary Electrophoresis-Electrospray Ionization-Mass Spectrometry for Improved Sensitivity and Repeatability in Glycopeptide Analysis

Over the last years, numerous strategies have been proposed to enhance both ionization efficiency and spray stability in electrospray ionization (ESI), in particular for nanospray applications. In nano-liquid chromatography-mass spectrometry (nano-LC-ESI-MS), a better ESI performance has been observed when a coaxial gas flow is added around the ESI emitter. Moreover, enrichment of the gas with an organic dopant has led to an improved desolvation and ionization efficiency with an overall enhanced sensitivity. In this study, the use of a dopant enriched nitrogen (DEN)-gas combined with sheathless capillary electrophoresis (CE)-ESI-MS was evaluated for glycopeptide analysis. Using acetonitrile as a dopant, an increased sensitivity was observed compared to conventional sheathless CE-ESI-MS. Up to 25-fold higher sensitivities for model glycopeptides were obtained, allowing for limits of detection unachieved by state-of-the-art nano-LC-ESI-MS. The effect of DEN-gas on the repeatability and intermediate precision was also investigated. When compared to previously reported nano-LC-ESI-MS measurements, similar values were found for CE-ESI-MS with DEN-gas. The enhanced repeatability fosters the use of DEN-gas sheathless CE-ESI-MS in protein glycosylation analysis, where precision is essential. The use of DEN-gas opens new avenues for highly sensitive sheathless CE-ESI-MS approaches in glycoproteomics research, by significantly improving sensitivity and precision.

Pregnancy-associated serum N-glycome changes studied by high-throughput MALDI-TOF-MS

Pregnancy requires partial suppression of the immune system to ensure maternal-foetal tolerance. Protein glycosylation, and especially terminal sialic acid linkages, are of prime importance in regulating the pro- and anti-inflammatory immune responses. However, little is known about pregnancy-associated changes of the serum N-glycome and sialic acid linkages. Using a combination of recently developed methods, i.e. derivatisation that allows the distinction between α2,3- and α2,6-linked sialic acids by high-throughput MALDI-TOF-MS and software-assisted data processing, we analysed the serum N-glycome of a cohort of 29 healthy women at 6 time points during and after pregnancy. A total of 77 N-glycans were followed over time, confirming in part previous findings while also revealing novel associations (e.g. an increase of FA2BG1S1(6), FA2G1S1(6) and A2BG2S2(6) with delivery). From the individual glycans we calculated 42 derived traits. With these, an increase during pregnancy and decrease after delivery was observed for both α2,3- and α2,6-linked sialylation. Additionally, a difference in the recovery speed after delivery was observed for α2,3- and α2,6-linked sialylation of triantennary glycans. In conclusion, our new high-throughput workflow allowed the identification of novel plasma glycosylation changes with pregnancy.

MassyTools: A High-Throughput Targeted Data Processing Tool for Relative Quantitation and Quality Control Developed for Glycomic and Glycoproteomic MALDI-MS

The study of N-linked glycosylation has long been complicated by a lack of bioinformatics tools. In particular, there is still a lack of fast and robust data processing tools for targeted (relative) quantitation. We have developed modular, high-throughput data processing software, MassyTools, that is capable of calibrating spectra, extracting data, and performing quality control calculations based on a user-defined list of glycan or glycopeptide compositions. Typical examples of output include relative areas after background subtraction, isotopic pattern-based quality scores, spectral quality scores, and signal-to-noise ratios. We demonstrated MassyTools' performance on MALDI-TOF-MS glycan and glycopeptide data from different samples. MassyTools yielded better calibration than the commercial software flexAnalysis, generally showing 2-fold better ppm errors after internal calibration. Relative quantitation using MassyTools and flexAnalysis gave similar results, yielding a relative standard deviation (RSD) of the main glycan of ~6%. However, MassyTools yielded 2- to 5-fold lower RSD values for low-abundant analytes than flexAnalysis. Additionally, feature curation based on the computed quality criteria improved the data quality. In conclusion, we show that MassyTools is a robust automated data processing tool for high-throughput, high-performance glycosylation analysis. The package is released under the Apache 2.0 license and is freely available on GitHub ( https://github.com/Tarskin/MassyTools ).

Human plasma protein N-glycosylation

Glycosylation is the most abundant and complex protein modification, and can have a profound structural and functional effect on the conjugate. The oligosaccharide fraction is recognized to be involved in multiple biological processes, and to affect proteins physical properties, and has consequentially been labeled a critical quality attribute of biopharmaceuticals. Additionally, due to recent advances in analytical methods and analysis software, glycosylation is targeted in the search for disease biomarkers for early diagnosis and patient stratification. Biofluids such as saliva, serum or plasma are of great use in this regard, as they are easily accessible and can provide relevant glycosylation information. Thus, as the assessment of protein glycosylation is becoming a major element in clinical and biopharmaceutical research, this review aims to convey the current state of knowledge on the N-glycosylation of the major plasma glycoproteins alpha-1-acid glycoprotein, alpha-1-antitrypsin, alpha-1B-glycoprotein, alpha-2-HS-glycoprotein, alpha-2-macroglobulin, antithrombin-III, apolipoprotein B-100, apolipoprotein D, apolipoprotein F, beta-2-glycoprotein 1, ceruloplasmin, fibrinogen, immunoglobulin (Ig) A, IgG, IgM, haptoglobin, hemopexin, histidine-rich glycoprotein, kininogen-1, serotransferrin, vitronectin, and zinc-alpha-2-glycoprotein. In addition, the less abundant immunoglobulins D and E are included because of their major relevance in immunology and biopharmaceutical research. Where available, the glycosylation is described in a site-specific manner. In the discussion, we put the glycosylation of individual proteins into perspective and speculate how the individual proteins may contribute to a total plasma N-glycosylation profile determined at the released glycan level.

Glycoforms of Immunoglobulin G Based Biopharmaceuticals Are Differentially Cleaved by Trypsin Due to the Glycoform Influence on Higher-Order Structure

It has been reported that glycosylation can influence the proteolytic cleavage of proteins. A thorough investigation of this phenomenon was conducted for the serine protease trypsin, which is essential in many proteomics workflows. Monoclonal and polyclonal immunoglobulin G biopharmaceuticals were employed as model substances, which are highly relevant for the bioanalytical applications. Relative quantitation of glycopeptides derived from the conserved Fc-glycosylation site allowed resolution of biases on the level of individual glycan compositions. As a result, a strong preferential digestion of high mannose, hybrid, alpha2-3-sialylated and bisected glycoforms was observed over the most abundant neutral, fucosylated glycoforms. Interestingly, this bias was, to a large extent, dependent on the intact higher order structure of the antibodies and, consequently, was drastically reduced in denatured versus intact antibodies. In addition, a cleavage protocol with acidic denaturation was tested, which featured reduced hands-on time and toxicity while showing highly comparable results to a published denaturation, reduction, and alkylation based protocol.

Hinge-Region O-Glycosylation of Human Immunoglobulin G3 (IgG3)

Immunoglobulin G (IgG) is one of the most abundant proteins present in human serum and a fundamental component of the immune system. IgG3 represents ∼8% of the total amount of IgG in human serum and stands out from the other IgG subclasses because of its elongated hinge region and enhanced effector functions. This study reports partial O-glycosylation of the IgG3 hinge region, observed with nanoLC-ESI-IT-MS(/MS) analysis after proteolytic digestion. The repeat regions within the IgG3 hinge were found to be in part O-glycosylated at the threonine in the triple repeat motif. Non-, mono- and disialylated core 1-type O-glycans were detected in various IgG3 samples, both poly- and monoclonal. NanoLC-ESI-IT-MS/MS with electron transfer dissociation fragmentation and CE-MS/MS with CID fragmentation were used to determine the site of IgG3 O-glycosylation. The O-glycosylation site was further confirmed by the recombinant production of mutant IgG3 in which potential O-glycosylation sites had been knocked out.

For IgG3 samples from six donors we found similar O-glycan structures and site occupancies, whereas for the same samples the conserved N-glycosylation of the Fc CH2 domain showed considerable interindividual variation. The occupancy of each of the three O-glycosylation sites was found to be ∼10% in six serum-derived IgG3 samples and ∼13% in two monoclonal IgG3 allotypes.

The relationship between the skin and some bacterial species occurring on it in the Merino

Ten bacterial species were isolated from areas on the skin of Merino sheep affected by a chronic scaly condition leading to retarded wool growth. The growth requirements of the bacteria were studied and it was shown that they could multiply under the conditions prevailing on the skin if moisture was provided. All the bacteria isolated have the ability to stimulate the infiltration of round cells into the dermis, which is the essential feature of the pathological changes in the naturally affected skin. It was concluded that the bacteria have a decided aetiological role.

The acquisition of immunity to Histophilus ovis by sheep in nature

It was demonstrated that skin wound infection with Histophilus ovis elicits an immune response which can protect a ram against a challenge injection of the same organism into its epididymis.

Immunity against genital infection by Histophilus ovis in rams

Rams have been immunized against an infection of their genitalia by Histophilus ovis. An alum-precipitated antigen and an antigen plus Freund's complete adjuvant proved equally effective. An injection of live H. ovis into the epididymal tissue proved to be a better method of challenging immunity than an injection into the vas deferens. It was shown that cell-mediated immunity, as evidenced by tests for lymphocyte transformation, the presence of a macrophage migration inhibition factor and a delayed hypersensitivity skin reaction did not play a role in the resistance, nor did specific IgG antibodies have any protective influence. It was shown that neutrophils play a cardinal role in the immunity against H. ovis infection in so far as they phagocytize and destroy the organisms and are attracted to them by chemotaxis in immune animals.

The epidemiology of bacterial infection of the genitalia in rams

The interrelationship between the various bacteria isolated from the genital tract of rams and their host animals was studied. The pathogenicity of the different isolates varied. Several of these bacteria could be cultured in a medium consisting of a suspension of pen floor debris solidified with agar, while many organisms survived in the suspension for 10 days. Epidemiological investigations showed that rams kept under intensive systems were subjected to large-scale invasion of their genitalia by bacteria which led to infection of the accessory glands and orchitis and epididymitis. Apart from the preputial cavity, some rams kept on open range were entirely free of bacterial infection of their genitalia, and those that did have bacteria in the deeper parts of their genitalia had a very significantly lower incidence of pathological lesions of their genitalia. Finding bacteria and neutrophils in semen is consistent with the epidemiological findings.

Retardation of wool growth in Merino sheep caused by bacteria

A condition evidenced by retarded growth of wool with alteration of the yolk into a yellow, sticky, wax-like substance was investigated. The condition was associated with hyperaemia and cellular infiltration into the dermis in the affected areas. Three bacterial species, viz. Enterobacter aerogenes, E. agglomerans and Hafnia alvei, which could grow on the water-extractable component of wool-yolk, were incriminated as the cause of the condition.

The reaction of ovine neutrophils to Histophilus ovis in relation to genital infection of rams

Histophilus ovis was shown to be phagocytized by neutrophils when the organisms enter the lumen of the reproductive tract of the ram. The phagocytosis and destruction of H. ovis by neutrophils was demonstrated in vitro by the viable count method and by electron microscopy. It was shown that immunoglobulins and complement had no influence on the phagocytosis and destruction of H. ovis. Phagocytosis and killing of H. ovis was accomplished equally well by neutrophils from immunized and non-immunized rams. Immunized rams showed a massive infiltration of neutrophils into the walls, epithelium and lumen of their ampullae when dead H. ovis were introduced into their lumen.

Heartwater in Angora goats. I. Immunity subsequent to artificial infection and treatment

This study confirmed reports that Angora goats are highly susceptible to Cowdria ruminantium and showed that immunization of this breed against heartwater may be difficult hazardous. It was found that if goats were treated on the 2nd or 3rd day of the febrile reaction following the intravenous inoculation of the heartwater agent, few animals survived the infection. If, on the other hand, treatment was instituted on the 1st day of the reaction, the chances of survival were good, but the immunity of the goats to subsequent challenge was poor.

A surgical technique for the experimental reproduction of epididymitis in rams

A surgical technique is described for introducing a bacterial culture into the vas deferens of a ram close to the epididymis in such a manner that the infective material spreads to the lumen of the ductus epididymidis.

The pathology of bacterial infection of the genitalia in rams

Details are given of the macroscopic and histopathological changes brought about by infection of the genitalia of rams by bacteria other than Brucella ovis. Lesions of the seminal vesicles and ampullae are described which, in addition to the clinically evident lesions of the testes and epididymis, could be an important reasons for impaired fertility. The name "bacterial infection of the genitalia", abbreviated to BIG, is suggested as a more appropriate designation for this condition than "ram epididymitis".

The aetiology of ram epididymitis

A wide variety of organisms from the environment invade the preputial cavity of rams. Various of these organisms can be isolated from the deeper parts of the male genital tract, and especially from the accessory glands. Some of the bacteria present in the sheath can be stimulated to migrate to the deeper parts of the genital tract by injections into the host animal of luteinizing-hormone-releasing-hormone and injections of pregnant mare serum gonadotrophin. The increase levels of luteinizing hormone and follicle-stimulating hormone in surgically prepared cryptorchids also stimulate migration of the organisms. The natural mode of development of genital infections in rams is formulated as follows: The preputial cavity of a ram becomes invaded by various organisms through contact with the environment. When, under the influence of systemic hormonal stimulation, the genitalia undergo development, suitable conditions are created for the migration of some of the bacteria in the sheath to the deeper-lying organs of the genital tract such as the vesiculae seminales, epididymides and testes. In these organs the bacteria can possibly initiate a pathological process.

The immune response of horses to tetanus toxoid

An intramuscular injection of 8-16 Lf tetanus toxoid in water-in-oil emulsion protected adult horses against tetanus for at least 128 weeks. A booster dose of 8 Lf toxoid in aqueous solution protected them for a further period of at least 3 1/2 years. Colostral immunity protected foals for at least 10 weeks. An intramuscular injection of 8 Lf toxoid in water-in-oil emulsion given to foals from immune dams when they were 10-18 weeks old did not elicit any antibody response. They did respond, however, to a booster injection of 8 Lf toxoid in aqueous solution given 12 weeks after the first dose. New-born foals were shown to be inherently unable to respond to an injection of tetanus toxoid.

The future of veterinary services in the Republic of South Africa

Future developments will depend mainly on new information generated by research and on effective application of preventive medicine. In the latter case, the various diagnostic centres in South Africa will have to be developed to their full extent, leading to the drawing up of computerised disease profiles and monitoring of the incidence of scheduled diseases. Dealing with these problems will require further knowledge to be generated by research. Problems of increasing drug, insecticide and acaricide resistance and problems of virus bionomics will call for attack at the molecular, biochemical, biophysical and immunological levels. This will demand adjustment of post-graduate veterinary education and of ever closer collaboration with scientists well-versed in the basic disciplines. Despite the argument that animal production will be ousted by crop production, the former, particularly in South Africa, is bound to develop and will call for more attention to the physiology of digestion and metabolism and to diseases of metabolism of ruminants. Concern is expressed that so few young veterinarians take up research as a career, as South Africa has many veterinary problems peculiar to itself.

The taxonomic position of Clostridium botulinum type c

Experimental evidence is produced to justify abandoning the practice of subdividing Costridium botulinum Type C into type Calpha and Cbeta.

The antibody response of cattle to Clostridium botulinum types C and D toxoids

The resistance of cattle with varying serum-antitoxin titres was determined by per os challenge. The results proved that a solid immunity can be produced against C. botulinum toxins C1 and D. The immune response of cattle to various quantities of C. botulinum C1 and D toxoids, aluminium-phosphate-adsorbed and in water-in-oil emulsion was investigated. The response to antigen in water-in-oil emulsion was far superior to the other when they were used for primary and secondary stimuli. When cattle had been given a solid basic immunity with 2 injections of antigen in water-in-oil emulsion, essentially the same booster effect was obtained with antigen in water-in-oil emulsion and in aqueous solution. Only some of the animals injected intramuscularly with antigens in water-in-oil emulsion developed local lesions. These lesions were not large and their histological picture indicated a noticeable decline in severity within 20 weeks. A case is thus made out for the use of C. botulinum C1 and D toxoids in water-in-oil emulsion for the primary and secondary stimuli and an aqueous solution of these antigens for any booster stimulus as an improved method of protecting cattle against botulism.