Diverse Host Immune Responses of Different Geographical Populations of the Coconut Rhinoceros Beetle to Oryctes Rhinoceros Nudivirus (OrNV) Infection

Incursions of the coconut rhinoceros beetle (CRB), Oryctes rhinoceros, into different islands in the South Pacific have been detected in recent years. It has been suggested that this range expansion is related to an O. rhinoceros haplotype reported to show reduced susceptibility to the well-established classical biocontrol agent, Oryctes rhinoceros nudivirus (OrNV). Our understanding of the genetic characteristics which distinguish the population of O. rhinoceros that has recently established in Solomon Islands from other well-established populations across the region is very limited. Here, we hypothesized that the recently established O. rhinoceros population should have greater innate immune responses when challenged by OrNV than those of well-established and native O. rhinoceros populations. We used the RNA sequencing (RNA-Seq) approach to generate gene expression profiles of midgut tissue from OrNV-infected and noninfected individuals collected in the Solomon Islands (recent incursion), Papua New Guinea and Fiji (previously established), and the Philippines (within the native range). The collections included individuals from each of the three major mitochondrial lineages (CRB-G, CRB-PNG, and CRB-S) known to the region, allowing us to explore the specific responses of each haplotype to infection. Although insects from the Philippines and Solomon Islands that were tested belong to the same mitochondrial lineage (CRB-G), their overall responses to infection were different. The number of differentially expressed genes between OrNV-infected and noninfected wild-caught individuals from the four different locations varied from 148 to 252. Persistent OrNV infection caused a high level of induced antimicrobial activity and immune responses in O. rhinoceros, but the direction and magnitude of the responses were population specific. The insects tested from the Solomon Islands displayed extremely high expression of genes which are known to be involved in immune responses (e.g. coleoptericin, cecropin, and serpin). These variations in the host immune system among insects from different geographical regions might be driven by variations in the virulence of OrNV isolates, and this requires further investigation. Overall, our current findings support the importance of immunity in insect pest incursion and an expansion of the pest's geographic range. IMPORTANCE Oryctes rhinoceros nudivirus (OrNV) is a double-stranded DNA (dsDNA) virus which has been used as a biocontrol agent to suppress coconut rhinoceros beetle (CRB) in the Pacific Islands. Recently a new wave of CRB incursions in Oceania is thought to be related to the presence of low-virulence isolates of OrNV or virus-tolerant haplotypes of beetles (CRB-G). Our comparative analysis of OrNV-infected and noninfected CRBs revealed that specific sets of genes were induced by viral infection in the beetles. This induction was much stronger in beetles collected from the Solomon Islands, a newly invaded country, than in individuals collected from within the beetle's native range (the Philippines) or from longer-established populations in its exotic range (Fiji and Papua New Guinea [PNG]). Beetles from the Philippines and the Solomon Islands that were tested in this study all belonged to the CRB-G haplotype, but the country-specific responses of the beetles to OrNV infection were different.

Retrospective anti-tetanus antibody responses of zoo-based Asian elephants (Elephas maximus) and rhinoceros (Rhinocerotidae)

Tetanus toxoids (TT) commercially available for use in horses and livestock are commonly used to vaccinate elephants and rhinoceros that are in human care. Although recommendations for booster intervals have changed in human and horse protocols to reduce the risks associated with hyper-immunity (i.e. B-cell anergy and hypersensitivity reactions) these have generally not been adopted in zoo protocols. Additionally, there is no evidence to demonstrate commercial TT immunogenicity in rhinoceros. In this study, a preliminary analysis of rhinoceros antibody responses to TT was conducted, in addition to an exploration of the impact of various booster frequencies on antibody responses in elephant. Retrospective analysis of archived serum samples was conducted for 9 Asian elephants (Elephas maximus), 7 southern black (Diceros bicornis minor), one southern white (Ceratotherium simum simum), and two greater one-horned (Rhinoceros unicornis) rhinoceros. Pre-vaccination (baseline) samples and those following priming vaccination (rhinoceros only), annual and non-annual boosters were targeted. A commercially available competitive ELISA kit was used to quantify serum anti-TT antibodies. Average baseline and post-vaccination anti-tetanus antibody concentrations were greater in elephant (92 mg/L ± 42, n = 3, N = 3; 125 ± 76, n = 82, N = 9) than in rhinoceros (47 mg/L ± 39, n = 8, N = 8; 44 mg/L ± 37, n = 16, N = 7). Rhinoceros antibody concentrations did not differ markedly following vaccinations from their naturally acquired high pre-vaccination concentrations. Eight elephants demonstrated antibody maintenance for 3-5 years without a tetanus booster. Additionally, although five out of nine elephants developed local reactions consistent with delayed type IV hypersensitivity following some boosters, there was no association between high antibody concentrations and increased incidence of adverse reactions. In addition, no decrease in antibody concentrations was detected as a result of annual vaccination in elephants, though this does not entirely rule out potential for B-cell anergy.

Cloning, sequencing and expression of white rhinoceros (Ceratotherium simum) interferon-gamma (IFN-γ) and the production of rhinoceros IFN-γ specific antibodies

Bovine tuberculosis (BTB) is endemic in African buffalo (Syncerus caffer) in the Kruger National Park (KNP). In addition to buffalo, Mycobacterium bovis has been found in at least 14 other mammalian species in South Africa, including kudu (Tragelaphus strepsiceros), Chacma baboon (Papio ursinus) and lion (Panthera leo). This has raised concern about the spillover into other potentially susceptible species like rhinoceros, thus jeopardising breeding and relocation projects aiming at the conservation of biodiversity. Hence, procedures to screen for and diagnose BTB in black rhinoceros (Diceros bicornis) and white rhinoceros (Ceratotherium simum) need to be in place. The Interferon-gamma (IFN-gamma) assay is used as a routine diagnostic tool to determine infection of cattle and recently African buffalo, with M. bovis and other mycobacteria. The aim of the present work was to develop reagents to set up a rhinoceros IFN-gamma (RhIFN-gamma) assay. The white rhinoceros IFN-gamma gene was cloned, sequenced and expressed as a mature protein. Amino acid (aa) sequence analysis revealed that RhIFN-gamma shares a homology of 90% with equine IFN-gamma. Monoclonal antibodies, as well as polyclonal chicken antibodies (Yolk Immunoglobulin-IgY) with specificity for recombinant RhIFN-gamma were produced. Using the monoclonals as capture antibodies and the polyclonal IgY for detection, it was shown that recombinant as well as native white rhinoceros IFN-gamma was recognised. This preliminary IFN-gamma enzyme-linked immunosorbent assay (ELISA), has the potential to be developed into a diagnostic assay for M. bovis infection in rhinoceros.

Comparative studies of mitogen- and antigen-induced lymphocyte proliferation in four captive rhinoceros species

Cellular immune function in four rhinoceros species was evaluated by way of in vitro lymphocyte proliferation responses to mitogenic and antigenic stimuli to establish normative data on white blood cell activity for each species and to identify species-specific differences that might help explain the predisposition of black rhinoceroses (Diceros bicornis) to disease. A cross section of the U.S. rhinoceros population encompassing all four captive species was sampled, including the Sumatran rhinoceros (Dicerorhinus sumatrensis) (n = 3); Indian rhinoceros (Rhinoceros unicornis) (n = 4); African black rhinoceros (n = 16); and African white rhinoceros (Ceratotherium simum) (n = 10). Of the four species evaluated, African black rhinoceroses exhibited the weakest (P < 0.05) lymphocyte proliferative responses to the mitogens: pokeweed (0.1 microg/ml), phytohemagglutinin (0.3 microg/ml), and concanavalin A (5.0 microg/ml). Total cell density at the end of culture was only 70% of that achieved with lymphocytes isolated from African white rhinoceroses, Indian rhinoceroses, and Sumatran rhinoceroses. However, lymphocyte response to bacterial endotoxin lipopolysaccharide was similar (P > 0.05) across species. Antigenic stimulation produced much weaker responses than mitogenic stimulation. No differences (P > 0.05) were observed among rhinoceros species in response to 1 and 10 microg/ml of Leptospira icterohemorrhagiae or Leptospira gryppotyphosa. Lymphocytes from African white rhinoceroses proliferated weakly in the presence of Aspergillus fumigatus filtrate, whereas lymphocytes from the southern black rhinoceros subspecies appeared slightly suppressed in the presence of increasing doses (0.1, 1, and 10 microg/ml) of Aspergillus filtrate. This comparative data set characterizing lymphocyte proliferation in the rhinoceros reveals several differences in immune cell responses among rhinoceros species and provides some evidence that lymphocytes of captive African black rhinoceroses are less vigorous than those of the other rhinoceros species.

Evolutionary history of MHC class I genes in the mammalian order Perissodactyla

We carried out an analysis of partial sequences from expressed major histocompatibility complex (MHC) class I genes isolated from a range of equid species and more distantly related members of the mammalian order Perissodactyla. Phylogenetic analysis revealed a minimum of six groups, five of which contained genes and alleles that are found in equid species and one group specific to the rhinoceros. Four of the groups contained only one, or very few sequences, indicating the presence of relatively nonpolymorphic loci, while another group contained the majority of the equid sequences identified. These data suggest that a diversification of MHC genes took place after the split between the Equidae and the Rhinocerotidae yet before the speciation events within the genus Equus.

Characterization of a red blood cell antigen in donkeys and mules associated with neonatal isoerythrolysis

A red cell antigen of donkeys and mules was identified using antibodies in serum from a mare which produced a mule foal affected with neonatal isoerythrolysis (NI). Subsequently antibodies with similar activity were identified in the sera of other mares which had produced mule foals and were produced by immunization of horses with blood from donkeys. The antigen detected by these antibodies does not correspond to any recognized horse red cell alloantigen. This may be a xenoantigen since all donkeys (and mules) tested have shared this antigen and all horses tested have lacked the antigen. The results suggest that all mule pregnancies (donkey sire x horse dam) are incompatible with regard to this factor and a potential for neonatal isoerythrolysis exists in all cases.

Comparison of five tests for the serologic diagnosis of myiasis by Gasterophilus spp. larvae (Diptera: Gasterophilidae) in horses and donkeys: a preliminary study

Sera from 41 horses and 159 donkeys, from twelve States of México, were tested to ascertain anti-Gasterophilus circulating antibodies by double immunodiffusion (DD), counterimmunoelectrophoresis (CIE), indirect haemagglutination (IH), thin layer immunoassay (TIA) and diffusion-in-gel ELISA (DIG-ELISA) methods using crude somatic antigen from third instar larvae of G. intestinalis (DeGeer). At necropsy, 33/41 horses and 24/159 donkeys were found to be parasitized by G. intestinalis and/or G. nasalis (L.). Gasterophilus intestinalis was the species most commonly found in the equines. Analysis of the sera from the infected animals by DD showed positive results of 21.2% in horses and of 8% in donkeys. Screening the sera with CIE gave sensitivities of 69.7% in horses and of 32% in donkeys. Examination of the sera by IH showed positive results of 87.9% and of 48% in horses and donkeys, respectively. Testing the sera with TIA gave sensitivities of 93.9% in horses and of 96% in donkeys. Analysis of horses' sera by DIG-ELISA showed a sensitivity of 93.9%.

Circulation of African horsesickness virus in zebra (Equus burchelli) in the Kruger National Park, South Africa, as measured by the prevalence of type specific antibodies

In the Kruger National Park 75% of zebra foals are born in October-March and they lose their passive immunity against African horsesickness virus (AHSV) when they are 5-6 months old. One month later infection with different serotypes of AHSV amounts to 31% and thereafter infections increase rapidly to almost 100% before the foals are 12 months old. The capability of zebra to maintain AHSV is clearly illustrated by the continuing infections during every month of the year with a peak period in winter. This peak is ascribed to the presence of large numbers of susceptible foals in the presence of active Culicoides species.

Immunokinetics of equine herpesvirus 1 in donkey mares: suppression of secondary cell-mediated response

To study the immunokinetics of equine herpesvirus 1 (EHV1), donkey mares were immunised with a laboratory strain of EHV1, or with recommended doses of Pneumabort-K vaccine (EHV1 Army 183 strain, formalin-inactivated, with an oil adjuvant) and a booster was given after three months. Humoral immune responses were studied by employing a virus neutralisation (VN) test. A leucocyte migration inhibition test (LMIT) was employed for the assay of cellular immune responses. The VN antibody titre reached 1:64 or 1:128 after primary immunisation and showed a marginal increase (1:256) after secondary immunisation with either of the immunogens. After the primary dose of immunogen, there was a gradual increase in host cellular response which persisted for up to three months. However, on secondary immunisation, cell-mediated immune response was short-lived and weak compared to the primary response with both immunogens. This could be one possible explanation for breakdown of anti-EHV1 immunity leading to abortion in immunised mares.

Antibodies in horses, mules and donkeys following monovalent vaccination against African horse sickness

A total of 256 sera collected from three species of domesticated equidae in four different Spanish provinces were examined 1-4 months after the administration of attenuated monovalent African horse sickness virus (AHSV) serotype 4 vaccine. Approximately 10% of the sera were negative by ELISA, virus neutralization, agar gel immuno-diffusion and complement fixation tests. Similar negative reactions were recorded with sera from two ponies after experimental primary vaccination. The rapid rise in antibodies in sera from these two ponies, after a second dose of vaccine, suggested they would probably have been immune to challenge. It is therefore suggested that the apparent absence of antibodies against AHSV in some animals after primary vaccination may not necessarily indicate a total lack of protection.

Antibodies to some pathogenic agents in free-living wild species in Tanzania

A total of 535 sera from eight species of wildlife were collected from different game areas in Tanzania between 1987 and 1989. These sera were tested for antibodies against foot-and-mouth disease, bovine herpes virus types 1 and 2, lumpy skin disease, bovine viral diarrhoea, Akabane, bovine ephemeral fever, bluetongue, enzootic bovine leucosis, African horse sickness and African swine fever viruses and Brucella abortus based on the expected species susceptibility. Sera from buffalo Syncerus caffer, wildebeest Connochaetes taurinus and topi Damaliscus korrigum contained antibodies against the majority of the pathogens tested. Antibodies to fewer pathogens were detected in sera from the other species. No antibodies to lumpy skin disease virus were detected in any of the sera examined. African horse sickness antibodies were detected in sera from Zebra and African swine fever antibodies were detected in wart hog. The occurrence of antibodies to these agents suggests that wild species act as reservoirs of infection for some of these pathogens. However, until the susceptibility of individual species is proven by isolation of the aetiological agents their role must remain speculative.

Suppression of lymphocyte proliferation by a greater than 30,000 molecular weight factor in horse conceptus-conditioned medium

In this experiment we have identified and partially characterized the immunosuppressive activity of preimplantation horse conceptus-conditioned medium (HCCM). Horse conceptuses were nonsurgically flushed from mares at Days 9-10 (n = 6), 15-16 (n = 3), and 25-26 (n = 3). After incubating the conceptuses for 24 h in RPMI-1640 supplemented with 15% fetal calf serum (FCS) and 1% penicillin/streptomycin, HCCM was obtained from cultures and tested for immunosuppressive activity in lymphocyte proliferation assays. Peripheral blood lymphocytes obtained from randomly selected mares were stimulated with mitogens (pokeweed mitogen [PWM], concanavalin A [Con A], and phytohemagglutinin [PHA]) in cultures supplemented with 0%, 25%, or 50% HCCM. HCCM from all cultures suppressed lymphocyte proliferation induced by all three mitogens (p less than 0.001). After being subjected to various treatments (heating, freeze-thawing, and nitrocellulose filtration), HCCM maintained its full biological suppressor activity. Amicon microconcentrators with 10,000 and 30,000 molecular weight (MW) exclusion filter membranes were used to fractionate HCCM by molecular weight. The suppressor factor was found to be in the greater than 30,000 MW fraction. HCCM was further tested interspecifically on donkey and goat lymphocytes stimulated with PWM. HCCM did suppress proliferation of interspecific lymphocytes (p less than 0.01); however, the suppressive capacity of HCCM in caprine lymphocyte cultures was less (p less than 0.05) than that observed in equine cultures. These data support the hypothesis that the horse conceptus produces an immunoregulatory factor. This factor is extremely stabile and appears to exhibit some degree of species-specificity. The production and immunosuppressive effectiveness of such a factor may play an important role in maintaining the fetal allograft throughout gestation.

Feedback by early and late primary antisera on the primary and secondary adoptive immune responses of mice to burro erythrocytes

Experiments on antibody feedback inhibition of the immune response have confirmed that control is more effective against a primary response than against a secondary response. The cells producing antibodies in primary and secondary responses are different both in terms of number of IgFC and amount of antibody produced by individual IgFC (plaque size). Late primary anti-burro RBC sera (greater than 200 days), despite low titers, are, on a volume for volume basis, feedback inhibitors at least as good as early (8-12 days) primary antisera on primary responses but are more effective in suppressing secondary responses (B memory cells). Late primary antisera, due to the process of affinity maturation, have a high affinity for antigen. The suppressive effect of early and late antisera is equally removable by absorption with burro erythrocytes: a result which it is thought, decreases the likelihood of feedback by anti-idiotype being involved in the observed suppression. It is suggested that feedback antibody acts (a) in competition with receptors, inter alia removing antigen into immunologically irrelevant pathways, (b) by a process involving the linking of antigen to Fc receptors, and (c) as a blocking antibody coating B cells (Bm) or APC which are already binding epitopes, thus preventing their cooperation with specific helper or other accessory cells.

Use of high-performance liquid chromatography for the purification of antibodies and antibody conjugates and the study of antibody-antigen interactions

The purification and characterization of polyclonal and monoclonal antibodies and antibody-enzyme conjugates by high-performance liquid chromatography (HPLC) using a Protein Pak 300 SW column and a Protein Pak DEAE anion-exchange column is described. The following polyclonal antibodies were examined: (i) donkey anti-mouse immunoglobulin G (IgG), (ii) mouse IgG, (iii) sheep anti-human IgG and (IV) goat anti-human factor VIII. HPLC was used to analyse the purity of horseradish peroxidase conjugates of rabbit anti-mouse IgG and donkey anti-mouse IgG. In the case of donkey anti-mouse IgG, each stage of the production of the purified antibody and antibody-enzyme conjugate was monitored by HPLC. HPLC was used to examine monoclonal mouse anti-human T cell and mouse anti-human apoliproprotein B antibodies. The presence of antibody in ascites fluid from mice bearing Landschütz ascites tumour cells was also detected. The antigen-antibody reaction between human serum albumin and anti-human serum albumin was demonstrated using HPLC and this procedure should offer a novel method for studying antigen-antibody interaction.

Anti-antibody enhancement of iodine-131 anti-CEA radioimmunodetection in experimental and clinical studies

Imaging of tumors with radiolabeled antibodies, especially when located in the blood-rich visceral organs, may be improved through administration of a second antibody directed against the primary tumor-associated antibody. In hamsters bearing a human colonic carcinoma xenograft producing carcinoembryonic antigen (CEA), we injected donkey anti-goat IgG 24 hr after administration of 131I-labeled goat anti-CEA IgG and achieved enhanced tumor imaging 24-48 hr later, with a significant relative decrease of radioactivity in blood and all major organs except the spleen. In seven of nine patients, this method of anti-antibody clearance of nontargeted radioactive murine monoclonal antibodies revealed sites of cancer, including liver metastases. Characterization of radioactivity in the plasma before and after administration of the second antibody confirmed that complexes were quickly formed between primary and secondary antibodies, and imaging of the patients revealed a rapid uptake of radioactivity in the liver at 2 hr that dissipated within 24 hr. Radioactivity in the spleen gradually increased over time. The method of anti-antibody immunological enhancement of cancer imaging is feasible and may reveal tumor sites missed by conventional imaging.

A cascade of T-T interactions, mediated by the linked recognition of antigen, in the induction of T cells able to help delayed-type hypersensitivity responses

Previous work has shown that specific helper T cells are required for the primary induction of delayed-type hypersensitivity (DTH). Conditions are defined here under which the primary induction by antigen of precursor helper T cells only occurs in the presence of specific, irradiated effector T cells, demonstrating that the induction of helper T cells requires T-T cooperation. The interaction between precursor and effector helper T cells is mediated by the recognition of epitopes that must be physically linked to one another. In more detail, hapten-Ficoll conjugates and xenogeneic red blood cells induce medium-density but not low-density cultures of unprimed murine spleen cells to express antigen-specific DTH. Low-density cultures do not support the induction of DTH unless they are supplemented with specific irradiated helper T cells. These helper T cells are themselves induced when antigen is added to medium-density but not low-density cultures. Precursor helper T cells in low-density cultures are only induced by antigen in the presence of additional specific irradiated T cells. Further experiments were directed at analyzing the nature of this T-T interaction. Irradiated hapten-primed T cells help the induction of precursor helper T cells specific for burro red blood cells (BRBC) in the presence of haptenated BRBC and chicken red blood cells (CRBC), but do not help in the presence of haptenated CRBC and BRBC. These experiments demonstrate that the interaction between precursor and effector T cells is mediated by the linked recognition of antigen. These findings show that the induction of precursor cells for both DTH reactivity, and those T cells able to help in the induction of DTH, require specific helper T cells. It is further shown that the induction of T cells able to help in the induction of helper precursor cells takes place in medium-density but not low-density cultures. In order words, antigen, when added to medium-density cultures of normal spleen cells, induces T cells able to mediate DTH, and T cells able to help in the induction of these helper T cells, whereas antigen induces none of these T cells when added to low-density cultures unless appropriate specific helper T cells are added.(ABSTRACT TRUNCATED AT 400 WORDS)

A soluble class I molecule analogous to mouse Q10 in the horse and related species

Horse serum is shown to contain a soluble class I molecule analogous to the secreted Q10 molecule in the mouse. This molecule has several similarities to the recently described mouse Q10 molecule: it is smaller than membrane-bound equine class I molecules; it occurs in a high molecular mass complex of 200-300 kd in serum; and the serum levels of the equine molecule are similar to that of the Q10 molecule (about 30 micrograms/ml). A soluble molecule is also detected in the sera of species related to the horse; it has in fact been found in all the wild members of the order Perissodactyla so far tested. However, it was not detected in the serum of members of the orders Carnivora, Sirenia, Proboscidea, Artiodactyla, and Primates that were tested, nor in the serum of members of the order Rodentia other than in that of the genus Mus.

Immunological systematics of the extinct quagga (Equidae)

It has been debated whether the extinct quagga was a distinct fourth species of African zebra or whether it was merely the southern variant of the Plains zebra (Equus burchelli). Using a radioimmunoassay (RIA) technique, we have shown that proteins remaining in quagga skins from museums are much more similar to serum proteins of the Plains zebra than to those of the other two extant zebras.

[Immunoenzyme analysis. The isolation and characteristics of Soviet reagents for detecting the surface antigen of the hepatitis B virus in blood sera]

A method for the preparation of highly specific conjugates on the basis of antibodies obtained as a result of dissociation of the immune complex HBsAg--anti-HBsAg, formed in vitro, is proposed. ELISA was performed according to Walters with some modifications in the concentration of the assay ingredients and in the time of incubation. The technique of the assay of blood sera for the presence of HBsAg with the use of reagents manufactured in the USSR has been worked out.

Synthesis and evaluation of luminescent tracers and hapten-protein conjugates for use in luminescence immunoassays with immobilised antibodies and antigens. A critical study of macro solid phases for use in immunoassay systems, Part II

This article describes the synthesis of labels and hapten-protein conjugates for use in bio- and chemiluminescent immunoassay systems, together with the problems encountered. The effects of maleimide upon acetate-, adenylate- and pyruvate kinase activity have been studied, as well as upon the luciferin-luciferase monitoring system. Maleimide inhibited both acetate and adenylate kinase but showed no inhibition of pyruvate kinase and the monitoring reagent. Four heterobifunctional reagents were tested for their capability in forming pyruvate kinase-donkey-anti-rabbit IgG conjugates which retained enzyme and antibody activity. The best results were obtained with succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate and succinimidyl-6-(p-maleimidophenyl)-hexanoate. The relationship between the amounts of succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate and IgG was studied with respect to enzymic activity of the conjugate. The Michaelis-Menten constants for both conjugated and non-conjugated pyruvate kinase were calculated and compared. It was found that the maximal velocity (Vmax) of the conjugated enzyme was lower than that of the non-conjugated enzyme although the "apparent" Km value was the same for both conjugated and non-conjugated pyruvate kinase. The pyruvate kinase-anti rabbit IgG conjugate was tested for its ability to bind to rabbit-IgG coated polystyrene balls. In addition to bioluminescent labels, the synthesis of chemiluminescent markers was undertaken and optimised. The three substances used for labelling were diazoluminol, diazoisoluminol and N-(4-aminobutyl)-N-ethylisoluminol hemisuccinamide the latter being used as an N-hydroxysuccinamide "active" ester. The ratio of label to IgG was studied for diazoluminol and N-(4-aminobutyl)-N-ethylisoluminol hemisuccinamide active ester after it had been discovered that diazoisoluminol was not suitable for coupling to antibodies. The optimal molar ratios label: IgG were for diazoluminol 40:1 and for N-(4-aminobutyl)-N-ethylisoluminol hemisuccinamide active ester 60:1. Increasing the substitution rate led to a lessening of the dynamic range, shown by an increase in the ratio between unspecific binding (noise) to maximal binding (signal) in an assay. The synthesis of hapten-protein conjugates for covalent coupling to polystyrene balls was undertaken as this formed part of the preparation for the assays described in Part III. The optimal production of gentamicin-bovine serum albumin and thyroxine-transferrin conjugates has been described in detail.

Naturally acquired antibodies to tetanus toxin in humans and animals from the galápagos islands

A serologic survey using a highly sensitive enzyme-linked immunosorbent assay confirmed the anticipated finding of naturally acquired antibodies to tetanus toxin both in humans and animals on the Galápagos Islands. In 57 inhabitants (mean age, 31.3 years) who had not been vaccinated against tetanus, antibody to tetanus toxin was detected in the blood in varying titers (geometric mean [reciprocal] titer [GMT], 0.015 international units [IU]/ml). In one individual the titer of antibody was greater than 12.5 IU/ml. Two individuals who had never been vaccinated against tetanus but who had reported having had clinical tetanus had titers of antibody to tetanus toxin of 0.02 IU/ml and 0.3 IU/ml, respectively. All nine of the animals studied showed antibody to tetanus toxin (GMT, 0.028 IU/ml).

Factors which govern the sensitivity of direct and indirect rosetting reactions and reverse passive haemagglutination in the identification of cell surface and free macromolecules

A series of immunoassays have recently been elaborated in which the red cell is used as a label or marker of interacting antibody, often anti-immunoglobulin (anti-Ig). This paper considers and investigates quantifiably, the different variables which affect the sensitivity of direct and indirect antiglobulin rosetting reactions (DARR and IARR) and of reverse passive haemagglutination (RPH).

Sensitivity is governed by the surface properties and amount of antibody on the indicator red cell and, in detection of cell-bound antigen, by the antigen density. By varying the antibody:Ig ratio on the red cell using affinity purified anti-Ig, cells with more than 1:32–64 antibody:Ig showed similar sensitivity in detection of lymphocyte sIg in DARR and IARR tests and of serum Ig by RPH. Using these indicator cells coupled with different Ab:Ig ratios to detect lymphocytes sensitized with different levels of anti-Ig in a model IARR test, it was clear that studying cells with a high density of determinants on the lymphocyte surface it is not necessary to have `strong' anti-immunoglobulin on the indicator cell, but increasingly sparse determinants require increasingly strong anti-Ig on the red cell to detect all positively reacting cells.

Red cells of different species afford carriers of varing sensitivity in all three reactions—DARR, IARR and RPH. Preliminary trypsin treatment may greatly further enhance the sensitivity of some species red blood cells (e.g. bovine and sheep), but leaves others (e.g. pig and donkey) unchanged. Use of ¹²⁵I-labelled Ig and anti-Ig showed that the increased sensitivity of trypsinized bovine and sheep RBC is not due to increased uptake of Ig during chromic chloride linkage or of antibody in agglutinations.

Solid phase antigen luminescent immunoassays (SPALT) for the determination of insulin, insulin antibodies and gentamicin levels in human serum

We describe an interesting and novel alternative to conventional immunoassay techniques for the measurement of antigens and antibodies in body fluids. The label used for all assays is a pyruvate kinase-IgG conjugate of the relevant second (species-specific) antibody. All assays follow the same principle in which a solid phase antigen is used to adsorb unreacted first (substance-specific) antibody following a conventional antibody-antigen reaction in a liquid phase. After washing, the solid phase antigen-first antibody is allowed to react with the labelled second antibody. The solid phase is then washed and the pyruvate kinase bound to the solid phase is used to generate ATP which is measured kinetically in a luminometer. Assays are described for insulin, insulin antibodies and gentamicin to demonstrate both the versatility and sensitivity of this type of assay. The insulin assay had a lower detection limit of under 0.25 microU per tube and was comparable with the radioimmunoassay used for routine purposes both in sensitivity and reproducibility. The insulin antibody assay correlated well with the radiometric determination used routinely in the laboratory. The gentamicin assay correlated well with the routine commercial radioimmunoassay and also had comparable coefficients of variation. In all cases, the inter- and intra-assay variation was under 10% in the range of interest.

Immunochemistry of cytochrome c. Identification of antigenic determinants through the study of hybrid molecules

Antibodies elicited in rabbits against horse cytochrome c cross-react in varying degree with the cytochromes c of other species. Radioimmunoassay experiments are described in which 23% of the immunoglobulin shown to bind to horse cytochrome c fails to react with beef cytochrome c, and 14% of that bound by beef cytochrome c does not react with rabbit cytochrome c. Studies of hybrid cytochromes, prepared by a reconstitution procedure involving the cleavage and re-formation of peptide bond 65-66, show that these differences result from single amino acid replacements, Beef cytochrome c differs in binding capacity from horse cytochrome c as a result of the substitution of a glycine for a lysine residue in sequence position 60, and the difference between rabbit cytochrome c and beef cytochrome c reflects the substitution of a valine for a proline residue in position 44. Reconstituted horse cytochrome c and reconstituted beef cytochrome c have binding capacities indistinguishable from those of the parent proteins. The presence of a homoserine rather than a methionine residue in position 65 results, in the case of the reconstituted horse molecule, in a slightly lower affinity for the antibody population directed against the lysine-60 region. A corresponding difference is not observed in the case of beef cytochrome c and its reconstitution product, which do not bind the population in question.

Enzyme-linked protein A: an enzyme-linked immunosorbent assay reagent for detecting antibodies in tuberculous exotic animals

An enzyme-linked immunosorbent assay (ELISA) was developed, using protein A labeled with horseradish peroxidase for detecting antibodies in tuberculous exotic mammals (llamas, rhinoceroses, elephants). The modified ELISA provides a rapid procedure for screening several animal species simultaneously for tuberculosis without the production of specific anti-species conjugates. Heat-killed cells of Mycobacterium bovis and M avium and purifed protein-derivative tuberculin of M bovis were used as antigens for ELISA.

The influence of antigen properties on the conditions required to elute antibodies from immunoadsorbents

Immunoadsorbents were used to purify a number of antibodies. Using pH 2.0 acid conditions alone it was possible to elute antibodies raised against human growth hormone (HGH) and Fc fragments from such immunoadsorbents with 50% or better recovery of antibody activity. However, to elute antibodies raised against triiodothyronine and cortisol required 6 M guanidine HCl, pH 2.0. The avidities of the purified antibodies were similar to those of the non-purified antibodies. The purified antibodies were stable in solution at 4 degrees C for at least six months.

[Production of monospecific immunoglobulin against human leukocyte interferon]

Donkeys were regularly, at seven-day intervals, immunized subcutaneously with human leukocyte interferon (IF) with the activity of 1.6 X 103 U/10 ml. IF-neutralizing antibodies in the titre of 1:128-1:256 were detected in the animals' sera after 38-40 injections. As a result of continuing injections the titre of these antibodies increased considerably. The antibodies to the components of the system in which the IF was obtained were revealed in parallel. Donkey antiinterferon plasma was prepared by plasmapheresis and antiinterferon immunoglobulin (AIFIG) was released from the plasma by centrifugation using ammonium sulphate at 50% saturation. Contamination antibodies were removed from AIFIG by affin chromatography on combined immunosorbent.

Homologous and cross-reactive precipitins in anti-pneumococcal sera raised in mules

Serial bleedings were obtained from two mules during prolonged immunization, one with type XXV the other with type VIII pneumococcal vaccine. IgGa, IgGb, IgGc, IgB, IgG(T) and IgM present among purified Pn anti-XXV and Pn anti-VIII immunoglobulin isolated from various bleedings were identified by use of rabbit anti-equine heavy chain specific reagents. Radioimmunodiffusion with 14C-labelled type XXV pneumococcal capsular polysaccharide and horse and donkey reagents with species specificity directed against donkey or horse IgGa respectively, demonstrated both parental horse and donkey IgGa heavy chain isotypes among the anti-PnXXV antibodies of the interspecies hybrid. Qualtitative and quantitative examination of the cross-precipitation of mule anti-PnXXV sera with the capsular polysaccharides of pneumococcal types IV, X and XA, with birch sap, ketha gum, and with polysaccharides of E. coli, Klebsiella and Rhizobium was carried out and compared with data obtained with anti-PnXXV raised in a horse. Analysis of supernatants from the cross-reactions showed that distinct subfractions had reacted. indicating a marked heterogeneity of the antibodies.

Prevalence of vesicular exanthema of swine antibodies among feral mammals associated with the southern California coastal zones

Serum-neutralizing antibodies to both vesicular exanthema of swine virus (VESV) and San Miguel sea lion virus (SMSV) were found in a number of animal species having an association with the southern California coastal zones. California sea lions (Zalophus californianus) had antibodies to 9 VESV types (A48, C52, D53, E54, F54, G55, I55, J56, and K56). Fur seals (Callorhinus ursinus) and elephant seal pups (Mirounga angustirostris) were tested for antibodies to 6 VESV types and all were negative. California gray whales (Eschrichtius robustus) were tested for antibodies to 9 VESV types, and sperm whale (Physeter catodon), finback whale (Balaenoptera physalus), and sei whale (Balaenoptera borealis) were tested for 6 VESV types. Among the last 4 species, antibodies were present for each VESV type except C52, and all species were positive for antibodies to 2 or more VESV types. Feral swine from both Santa Cruz Island and Santa Catalina Island were tested and antibodies were present for 8 of 9 VESV types and all SMSV types except SMSV-4. One donkey from San Miguel Island was positive for VESV I55 and 2 were positive for SMSV-2.

Cell-mediated immune response in equine babesiosis

An intradermal skin test, to demonstrate a delayed cutaneous hypersensitivity reaction in Babesia equi infection in donkeys, was developed. A skin reaction to B. equi antigen was elicited in vaccinnated, infected and carrier intact and splenectomised donkeys. The histopathological examination of the skin biopsy revealed infiltration of mononuclear cells and accumulation of oedematous fluid in the deeper layers of the dermis. A leucocyte migration inhibition test was developed and its specificity as an in vitro measure of cell-mediated immunity to B. equi antigen was established. The results of this study demonstrated a correlation between cell-mediated immunity and protection.

Dissociation of changes in enzymatic and immunoreactive rat serum dopamine bets-hydroxylase during growth and development

Dopamine beta-hydroxylase (DBH) activity was measured in the serum, heart and salivary glands of Sprague-Dawley rats from 1 day after birth to 90 days of age. Serum DBH activity in blood from newborn animals was 90 units, approximately 4.5 times higher than in blood from 60- to 90-day-old rats. The serum enzyme activity increased to 130 units at 15 days of age and then decreased rapidly to adult levels (20 units). This decrease was not due to changes in levels of circulating inhibitors or activators of the enzyme. Four different inbred strains of rats also demonstrated a striking decrease in serum DBH activity between 15 and 60 days of age. Cardiac DBH in Sprague-Dawley rats increased approximately 5-fold from birth to 15 days of age, but failed to decrease thereafter. Salivary gland DBH activity also increased with maturation and failed to decrease. Plasma concentrations of epinephrine and norepinephrine were no different in blood samples obtained from Sprague-Dawley rats 15 and 60 days of age. This finding makes it less likely that the decrease in serum DBH activity with maturation represents a decrease in the functional activity of sympathetic nerve terminals. Antibodies against DBH were used to measure immunoreactive DBH protein in serum from rats 15 and 60 days of age. These studies demonstrated a significantly higher enzymatic activity per unit of immunoreactive protein in blood from young rats than in blood from animals 60 days of age. The ratios of enzymatic activity to immunoreactive protein as measured by the quantity of antibody necessary to precipitate 50% of the endogenous serum DBH activity (AD50) were 21.18 +/- 1.04 and 3.83 +/- 0.40 (mean +/- S.E.M.) for blood from animals 15 and 60 days of age, respectively. Among the possible explanations for this observation are included a greater quantity of enzymatically inactive but immunoreactive DBH in blood of adult animals as compared with the blood of young rats, or the existence of a different form of serum DBH in blood of young animals.

Studies on the epidemiology of sandfly fever in Iran. III. Host-feeding patterns of Phlebotomus papatasi in an endemic area of the disease

Blood meals from 575 Phlebotomus papatasi collected in an Iranian village were identified by precipitin test. The majority of sandfly feedings (57.5%) were on birds, mainly chickens and pigeons. The remaining 42.5% were on mammals (humans, cows, mules, sheep, and goats) or were non-reactive. Calculation of forage ratios of each host species indicated that chickens, equines, and bovines were the preferred hosts of P. papatasi in the village. Results of this study demonstrate that P. papatasi has a much wider natural host range than indicated previously and suggest that this species is an opporunistic feeder and is not strongly anthropophilic. Observations on the diurnal activity of P. papatasi are also presented.

[Preparative isolation of alpha 2-macroglobulin, transferrin, albumin and study of their nonspecific gamma-inhibitory activity]

Profiles of distribution of non-specific gamma-inhibitors of influenza A2/Victoria/35/72 in donkey and horse sera were established by gel chromatography in Sephadex G-200. High and low molecular inhibitors were found in 19S and 4S serum fractions. Highly purified preparations of a2-macroglobulin, transferrine and albumin were isolated by a combination of methods of salt precipitation, gel chromatography on Sephadex G-100, G-200 and ion exchange on DEAE-Sephadex A-50. Heating sera resulted in a considerable increase of the antiviral activity of a2-macroglobulin and transferrine and a reduction of albumin activity.

Toxoplasma gondii antibodies in free-living African mammals

Twelve species of free-living African mammals from Kenya, Tanzania, Uganda and Zambia were tested for antibodies to Toxoplasma gondii using the indirect hemagglutination test. Of 157 animals sampled, 20 (13%) were seropositive. T. gondii antibodies were detected in Burchell's zebra, (Equus burchelli), hippopotamus (Hippopotamus amphibius), African elephant (Loxodonta africana), defassa waterbuck (Kobus defassa), lion (Panthera leo), and rock hyrax (Procavia capensis), The highest titers were found in elephants, two having titers of 1:4096 and one of 1:8192. These results are discussed in relation to the maintenance of T. gondii among African wildlife.

Modulation of the immune response by antigen-reactive lymphocytes after cultivation with gangliosides

GM1 ganglioside isolated from mouse brain was found to be capable of inhibiting the thymocytotoxicity of AKR anti-Thy 1.2 antiserum and to a lesser extent anti-BAtheta antiserum. GD1b ganglioside of mouse brain and thymocytes inhibited the thymocytotoxicity of rabbit anti-BAtheta anti-serum for mouse thymocytes. When GM1 ganglioside, in the form of cholesterol-lecithin liposomes, was incubated with spleen cell cultures in the presence of SRBC, depressed anti-SRBC hemolytic plaque responses were observed. This effect could be neutralized by first absorbing the GM1 liposomes with anti-Thy-1.2 antibodies. The kinetics of GM1 numbers when the ganglioside was added even as late as the 4th day of culture. Results of experiments in which GM1 ganglioside was incubated with either bone marrow cells or with thymocytes suggest that the target cell for GM1 liposomes is the B lymphocytes.

Enrichment of memory cells carrying receptors for a protein antigen (HSA). II. Improved enrichment technique, using BSA density gradient separation

Mice primed to human serum albumin (HSA) by means of an HSA--sheep red cell conjugate, developed a high level of memory to HSA, with little concomitant antibody production ('pure priming'). The proportion of HSA-specific antigen-binding cells was determined in the spleens of the primed mice by means of a rosette technique, using an HSA-donkey red cell conjugate. The specificity of the rosette-forming cells (RFC) was confirmed by the ability of soluble HSA to inhibit rosette formation. Highly enriched rosette suspensions (up to 40-fold enrichment) were prepared by bovine serum albumin density gradient centrifugation. The enriched suspensions could transfer adoptively memory to HSA, whereas the rosette-depleted fractions were totally inactive. It was thus confirmed that memory cells are included in the antigen-binding cells. A detectable level of memory could be transferred with 3000 rosettes. RFC similarly isolated from spleens of non-primed mice could also transfer a low level of responsiveness to HSA, but only when large numbers (70,000) were injected, together with primed, RFC-depleted spleen cells.

Limiting dilution analysis of helper T-cell function

Limiting dilution analysis has been applied to the study of T-cell 'helper' function in vitro. Using the microculture system one can estimate the numbers of (a) 'helper' T cells involved in specific collaboration with B cells and (b) those T cells which are able, on being activated by their specific antigen, to facilitate the response of B cells to another antigen. Such studies have enabled us to demonstrate that: (1) a single 'helper' T cell was able to activate a single B-cell precursor to detectable antibody production; (2) the 'helper' function of primed T cells was radio-resistant; (3) a minimal estimate of 'helper' frequencies could be obtained in defined cell populations; (4) nonspecific facilitation was directed towards virtually all available B cells of a given specificity if these were challenged with their appropriate particulate antigen; (5) the microculture system offers the opportunity to determine whether specific and non-specific T-cell 'helper' effects are a consequence of the activity of one T-cell type or of differenct subpopulations of T cells.

Inhibition of immune responses in vitro by specific antiserums to Ia antigens

Mouse antiserums prepared against Ia antigens, which are products of I (immune response) region genes of the H-2 complex, can inhibit both primary (immunoglobulin M) and secondary (immunoglobulin G) immune responses in vitro by mouse spleen cultures to heterologous erythrocytes. Antiserums directed specifically at products of either the H-2K or H-2D loci have no effect on this response.

Functional heterogeneity among the T-derived lymphocytes of the mouse. IV. Nature of spontaneously induced suppressor cells

When spleen cells are cultured for 4 days in the presence of fetal bovine serum, T-cells are generated which nonspecifically suppress the humoral responses of non-precultured cells to a variety of antigens. These T cells can be generated from both short-lived, sessile T1 cells and long-lived, recirculating T2 cells, and thus appear similar to suppressor T cells activated by concanavalin A.

Antigen-specific and nonspecific mediators of T cell/B cell cooperation. I. Evidence for their production by different T cells

Evidence is presented for two types of helper T cells in the mouse specific for a protein antigen, keyhole limpet hemocyanin (KLH). The first cell is able to help B cells respond to the hapten, trinitrophenyl (TNP), when coupled to KLH presumably through the participation of KLH-specific T cell factors. The second helper cell when stimulated with KLH is able to help B cells respond to red blood cell antigens, but not TNP-KLH, through the production of a non-antigen-specific factor. Both types of helper cells were shown to be present in the spleens of KLH-primed mice, although they occurred with different frequencies. They were shown to be different T cells by their segregation from each other in vitro at limiting dilution.

Complement-mediated alteration of antibody specificity in vivo

The simultaneous injection of heterologous anti-EL4 lymphoma serum and complement results in the rapid disappearance of such antibody from the periphery of non-tumor bearing mice. However, this phenomenon is only observed when a complement source capable of mediating the lysis of EL4 cells sensitized with such heterologous antibody is used. This complement mediated enhancement of anti-tumor antibody absorption was observed in vivo for three strains of mice. Omission of complement or the use of genetically deficient complement sources resulted in no effect on circulating antibody titer when compared to the titer of heterologous anti-tumor antibody observed in the periphery when injected alone. Exogenous complement did not enhance the clearance of heterologous anti-tetanus toxin serum, thereby suggesting that the increased absorption of anti-EL4 in vivo is not related simply to the enhanced clearance of foreign gamma-globulin. Confirmatory evidence of the role of complement in altering anti-tumor antibody specificity in vivo was obtained in a guinea pig tumor model as well. The data suggest that anti-tumor serum shown to be relatively specific for the tumor cell gains additional specificity in the presence of functional complement and consequently manifests avidity for cross-reactive determinants previously thought to be unrelated.