Levels Of Complement-fixing Antibodies Research Articles

Acquisition of complement fixing antibodies targeting Plasmodium falciparum merozoites in infants and their mothers in Uganda.

Antibody-mediated complement fixation has previously been associated with protection against malaria in naturally acquired immunity. However, the process of early-life development of complement-fixing antibodies in infants, both in comparison to their respective mothers and to other immune parameters, remains less clear. We measured complement-fixing antibodies in newborns and their mothers in a malaria endemic area over 5 years follow-up and found that infants' complement-fixing antibody levels were highest at birth, decreased until six months, then increased progressively until they were similar to birth at five years. Infants with high levels at birth experienced a faster decay of complement-fixing antibodies but showed similar levels to the low response group of newborns thereafter. No difference was observed in antibody levels between infant cord blood and mothers at delivery. The same result was found when categorized into high and low response groups, indicating placental transfer of antibodies. Complement-fixing antibodies were positively correlated with total schizont-specific IgG and IgM levels in mothers and infants at several time points. At nine months, complement-fixing antibodies were negatively correlated with total B cell frequency and osteopontin concentrations in the infants, while positively correlated with atypical memory B cells and P. falciparum-positive atypical memory B cells. This study indicates that complement-fixing antibodies against P. falciparum merozoites are produced in the mothers and placentally-transferred, and they are acquired in infants over time during the first years of life. Understanding early life immune responses is crucial for developing a functional, long lasting malaria vaccine.

Induction and decay of functional complement-fixing antibodies by the RTS,S malaria\xa0vaccine in children, and a negative impact of malaria exposure

BackgroundLeading malaria vaccine, RTS,S, is based on the circumsporozoite protein (CSP) of sporozoites. RTS,S confers partial protection against malaria in children, but efficacy wanes relatively quickly after primary immunization. Vaccine efficacy has some association with anti-CSP IgG; however, it is unclear how these antibodies function, and how functional antibodies are induced and maintained over time. Recent studies identified antibody-complement interactions as a potentially important immune mechanism against sporozoites. Here, we investigated whether RTS,S vaccine-induced antibodies could function by interacting with complement.MethodsSerum samples were selected from children in a phase IIb trial of RTS,S/AS02A conducted at two study sites of high and low malaria transmission intensity in Manhiça, Mozambique. Samples following primary immunization and 5-year post-immunization follow-up time points were included. Vaccine-induced antibodies were characterized by isotype, subclass, and epitope specificity, and tested for the ability to fix and activate complement. We additionally developed statistical methods to model the decay and determinants of functional antibodies after vaccination.ResultsRTS,S vaccination induced anti-CSP antibodies that were mostly IgG1, with some IgG3, IgG2, and IgM. Complement-fixing antibodies were effectively induced by vaccination, and targeted the central repeat and C-terminal regions of CSP. Higher levels of complement-fixing antibodies were associated with IgG that equally recognized both the central repeat and C-terminal regions of CSP. Older age and higher malaria exposure were significantly associated with a poorer induction of functional antibodies. There was a marked decay in functional complement-fixing antibodies within months after vaccination, as well as decays in IgG subclasses and IgM. Statistical modeling suggested the decay in complement-fixing antibodies was mostly attributed to the waning of anti-CSP IgG1, and to a lesser extent IgG3.ConclusionsWe demonstrate for the first time that RTS,S can induce complement-fixing antibodies in young malaria-exposed children. The short-lived nature of functional responses mirrors the declining vaccine efficacy of RTS,S over time. The negative influence of age and malaria exposure on functional antibodies has implications for understanding vaccine efficacy in different settings. These findings provide insights into the mechanisms and longevity of vaccine-induced immunity that will help inform the future development of highly efficacious and long-lasting malaria vaccines.

Human antibodies activate complement against Plasmodium falciparum sporozoites, and are associated with protection against malaria in children

BackgroundAntibodies targeting Plasmodium falciparum sporozoites play a key role in human immunity to malaria. However, antibody mechanisms that neutralize sporozoites are poorly understood. This has been a major constraint in developing highly efficacious vaccines, as we lack strong correlates of protective immunity.MethodsWe quantified the ability of human antibodies from malaria-exposed populations to interact with human complement, examined the functional effects of complement activity against P. falciparum sporozoites in vitro, and identified targets of functional antibodies. In children and adults from malaria-endemic regions, we determined the acquisition of complement-fixing antibodies to sporozoites and their relationship with antibody isotypes and subclasses. We also investigated associations with protective immunity in a longitudinal cohort of children (n = 206) residing in a malaria-endemic region.ResultsWe found that antibodies to the major sporozoite surface antigen, circumsporozoite protein (CSP), were predominately IgG1, IgG3, and IgM, and could interact with complement through recruitment of C1q and activation of the classical pathway. The central repeat region of CSP, included in leading vaccines, was a key target of complement-fixing antibodies. We show that antibodies activate human complement on P. falciparum sporozoites, which consequently inhibited hepatocyte cell traversal that is essential for establishing liver-stage infection, and led to sporozoite death in vitro. The natural acquisition of complement-fixing antibodies in malaria-exposed populations was age-dependent, and was acquired more slowly to sporozoite antigens than to merozoite antigens. In a longitudinal cohort of children, high levels of complement-fixing antibodies were significantly associated with protection against clinical malaria.ConclusionsThese novel findings point to complement activation by antibodies as an important mechanism of anti-sporozoite human immunity, thereby enabling new strategies for developing highly efficacious malaria vaccines. We also present evidence that complement-fixing antibodies may be a valuable correlate of protective immunity in humans.

Quality and Toxicity Assessments of Foot and Mouth Disease Virus Vaccine in Inoculated Guinea Pigs

The quality and toxicity assessment of foot and mouth disease virus vaccine was carried out in inoculated guinea pigs. The vaccine was developed from local isolates for the control and prevention of foot and mouth disease in Nigerian cattle. All the vaccine inputs tested were sterile and the high mean titre levels of complement fixing antibodies (92.8 and 147.2) and serum neutralizing antibodies (1.68 and 2.15), either as single dose or repeated doses inoculations. The blood immune cells parameters showed a positive immunological response due to activation by the vaccine antigens. There were increases in their population as compared to the controls. The blood enzyme profiles did not show any significant evidence of tissue or organ damage as all the results obtained were within the reference standard ranges of normal healthy guinea pigs. The findings from the study show that the vaccine could be used for the control and prevention of foot and mouth disease in Nigerian livestock. Keyword : Foot and Mouth Disease, Antibody, Quality, Toxicity, Vaccine.

Functional complement-fixing antibodies are generated against a Campylobacter jejuni capsule conjugate vaccine in non-human primates

Abstract Campylobacter jejuni is among the most common causes of diarrheal disease worldwide and efforts to develop protective measures against the pathogen are ongoing. One of the few defined virulence factors targeted for vaccine development is the capsule polysaccharide (CPS). We have developed a capsule conjugate vaccine against a prototype CPS, type HS23/36, that confers 100% protection against diarrhea caused by a homologous strain of C. jejuni in a non-human primate (NHP) model; however the mechanisms of protection remain unknown. Other licensed capsule conjugate vaccines against encapsulated gram-negative organisms use bactericidal antibody titers as a correlate of protection. We developed a flow cytometry-based serum bactericidal assay (SBA) to determine if increased levels of complement-fixing antibodies correlate with protection against C. jejuni. Sera from NHPs immunized with HS23/36 CPS-CRM197 vaccine showed significantly higher SBA titers when compared with control NHPs. Results were similar to those of a bacteriological-based SBA. All NHPs, irrespective of immune status, that did not develop diarrhea, had higher SBA titers compared with NHPs that developed diarrhea. Importantly, a strong correlation was found between serum anti-CPS IgG and SBA titers in NHPs and similar studies will be conducted in upcoming human clinical trials. This flow cytometry-based SBA assay is much simpler than bacteriological-based assays and should facilitate analyses of functional antibodies against multivalent C. jejuni capsule conjugate vaccines.

Induction of Transient Arthritis by the Adoptive Transfer of a Collagen II Specific Th1 Clone to HLA-DR4 (B1*0401) Transgenic Mice

Collagen II arthritis (CIA) represents an animal model of human RA that can be induced in DBA/1J (H-2q) but not in C57BL/6 mice (H-2b). A vigorous CII specific CD4 Th1-cell response but not IgG2 anti-CII antibody or CIA could be induced in C57BL/6 mice made transgenic for the RA shared epitope DR4 (B1*0401). We developed CD4 Th1-cell clones specific for CII from these transgenic (tg) mice in order to determine if the adoptive transfer of these clones into syngeneic tg C57BL/6 recipients could induce CIA. Three bovine CII specific (bCII) CD4 Th1-cell clones and one T-cell line specific for an immunodominant region of bCII (p261–273) were generated. Among these only one clone that could up-regulate anti-CII, IgG2 antibody in the recipient mice was able to induce transient arthritis. However, this level of IgG2 anti-CII antibody was only one-third of that seen in CII immunized DBA/1J mice that develop persistent arthritis. These results confirm our previous observations that the induction of CIA requires a sustained IgG2 antibody response to CII, an effect difficult to achieve even in DR4 (B1*0401) tg mice reconstituted with CD4 Th1 cells. This suggests that a rate limiting step in the development of human RA among those individuals expressing the RA shared epitope may be the requirement to generate sustained levels of complement fixing antibody to arthritogenic antigens.

Antibody responses to bacterial antigens in the pregnant ewe

The humoral immune response to the novel antigen Brucella abortus (S19) was examined in nonpregnant ewes and in ewes at different stages of pregnancy. Both the primary and secondary responses were monitored, by measuring the levels of total antibody, Immunoglobulin G (IgG), and complement fixing antibody. Results showed that total antibody production was significantly (p<0.01) impaired in late pregnancy and that IgG titres persisted at significantly (p<0.05) higher levels in non-pregnant animals late in the primary response and following the booster inoculation. Complement fixing antibody levels were significantly higher in non-pregnant ewes and animals inoculated post-partum. These results suggest that active immunity can be altered during pregnancy, with qualitative changes in the class and biological activity of antibody.

Immunoglobulin responses to Coxiella burnetii (Q fever): single-serum diagnosis of acute infection, using an immunofluorescence technique.

Blood specimens were collected over various periods of time from 30 abattoir workers with a clinical diagnosis of Q fever. All specimens were tested for complement-fixing antibodies and for specific immunoglobulin M (IgM) globulins to phase 1 and 2 Coxiella burnetii organisms by an immunofluorescence technique. All 22 patients with increasing levels of complement-fixing antibodies were shown to have generated specific IgM globulins, as did 4 patients with high convalescent titers but from whom "acute" specimens were not collected. Four individuals who did not show increasing levels of complement-fixing antibodies did not produce measurable levels of specific IgM. All patients with Q fever gave positive specific IgM results by 2 weeks after the onset of symptoms. IgM to phase 1 antigen persisted for 27 weeks in one patient, but IgM to phase 2 antigen was not detectable beyond 17 weeks. The estimation of Q fever-specific IgM has proved useful in confirming infection when only a "convalescent" blood specimen is available.

Serum antibody response to mature tooth allografts in mice.

Mature mouse molar teeth were transplanted to the tibial shaft medulla across an H-2 plus multiple non-H-2 histocompatibility barrier. Over the 35-day experimental period, low levels of complement-fixing antibody were detected in the serum of recipients. Antibody was distributed over two peak periods, 6 to 11 days and 21 to 27 days after transplantation, with IgM apparently preceding IgG production.

Cold agglutinin disease in a patient with Legionnaires' disease

• We present a case of Legionnaires' disease complicated by cold agglutinin disease. Therapy with erythromycin gluceptate was associated with resolution of both the pneumonia and the hemolysis. Complement-fixing antibody levels to<i>Mycoplasma pneumoniae</i>, influenza A, and adenoviruses were measured repeatedly throughout the clinical illness and were persistently nondiagnostic. The cold agglutinin present in the patient's serum was characterized as an IgM that demonstrated anti-I specificity. Thus,<i>Legionella pneumophila</i>should be considered a potential causative agent in patients with pneumonia and cold agglutinin disease. (<i>Arch Intern Med</i>140:1537-1539, 1980)

Cold Agglutinin Disease in a Patient With Legionnaires' Disease

We present a case of Legionnaires' disease complicated by cold agglutinin disease. Therapy with erythromycin gluceptate was associated with resolution of both the pneumonia and the hemolysis. Complement-fixing antibody levels to Mycoplasma pneumoniae, influenza A, and adenoviruses were measured repeatedly throughout the clinical illness and were persistently nondiagnostic. The cold agglutinin present in the patient's serum was characterized as an IgM that demonstrated anti-I specificity. Thus, Legionella pneumophila should be considered a potential causative agent in patients with pneumonia and cold agglutinin disease.

A complement fixation test for antigens of and antibodies to malignant catarrhal fever virus

A complement fixation test was developed for the study of malignant catarrhal fever (MCF). A clarified ultrasonicate of cultured cells infected with MCF virus was used as antigen and detected increasing levels of complement fixing antibody in 12 out of 14 and four out of nine infected cattle and rabbits respectively. Titres greater than or equal 1:64 were found in hyperimmune sera from three out of four cattle, five out of five rabbits and in eight out of 143 wildebeest. No antibody was detected in 310 normal cattle sera from areas of Kenya with endemic MCF. The test did not detect viral antigens in a number of infected tissues or increased anticomplementary activity in sera from sick animals.

Circulating immune complexes and complement-fixing antibodies in patients with varicella-zoster infection. Relationship to début of the disease.

Serum samples from 32 varicella-zoster (VZ)-infected patients were examined for circulating immune complexes (IC) within 1 1/2 week after début of the skin rash as well as during the following 5 weeks. Three test systems were used: a complement consumption (CC) assay, a C1q solid phase (CU1-SP) assay and a polyclonal rheumatoid factor-binding (pRF-I) assay. The CC and pRF-I assays were the most effective in detecting large IgG aggregates of IC, while aggregates of intermediate and small size were more easily demonstrated in the C1q-SP assay. IC were demonstrated in at least 2 assays simultaneously in 16 patients. Four of these patients were IC-positive in both observation periods, while 11 converted to IC-positive in the second observation interval. In 3 patients circulating IC were demonstrable as late as 8--10 weeks after the appearance of the skin rash. Maximal levels of complement-fixing antibodies to VZ antigens were observed 2 to 5 weeks after the appearance of the rash.

Complement-fixing antibody response in pneumococcal pneumonia.

Previous studies of complement-fixing antibodies to pneumococcal capsular polysaccharides in humans have yielded conflicting results. We studied 65 sera from 25 patients with pneumococcal pneumonia, using both fresh sera and heat-inactivated sera with added human complement. Only 4 of the 25 patients developed detectable levels of complement-fixing anticapsular antibody. Of the 25 patients, 22 developed detectable levels of hemagglutinating anticapsular antibody, indicating that they were able to develop an immunological response during the infection. Most of the antibody detected by hemagglutination was sensitive to 2-mercaptoethanol, but some 2-mercaptoethanol-resistant antibody was also detected. In studies with rabbit antiserum, the complement fixation test was found to be as sensitive as the hemagglutination test for detection of anticapsular antibody. It is not clear why detectable levels of complement-fixing antibody do not develop more often in patients with pneumococcal pneumonia. Studies of purified anticapsular antibody would be of interest to determine whether or not these antibodies are restricted to immunoglobulin subclasses having a limited capacity to fix complement.

Cytomegalovirus cornplement fixation antibody in Guillain‐Barré syndrome

Cytomegalovirus, measles, and adenovirus antibodies were measured in the sera of 92 Guillain-Barré patients and 120 controls. Thirty patients (33 percent) had markedly elevated levels of complement-fixing antibody to cytomegalovirus and in 21, a fourfold or more alteration in titer was demonstrated. Diagnostic falls in titer were seen in most instances and no significant elevation to the other viral agents was found. The serologic findings reported here suggest that cytomegalovirus may be a common agent involved in the pathogenesis of the Guillain-Barré syndrome.

The development of complement-fixing antibody in horses after infection with Mycoplasma equirhinis

Of 6 ponies apparently free of mycoplasmas, without antibody to M. equirhinis and with only very low values against N3, 2 were experimentally infected with M. equirhinis, 2 with the equine mycoplasma strain N3 and 2 remained uninoculated. The inocula were introduced via the nose and reisolation was by means of oropharyngeal and nasopharyngeal swabs. N3 was not recovered from any pony but M. equirhinis was recovered in large numbers within a few days from all 6 animals indicating that the organism spread naturally from the artificially infected ponies to the others. After about 6 weeks it became increasingly difficult to isolate the organisms and levels of complement-fixing antibody rose first in the nasal secretions and later in the serum. These fell after several weeks to undetectable levels. No clinical signs of infection were seen.

Host defenses in experimental scrub typhus: role of cellular immunity in heterologous protection.

The relative contributions of cellular and humoral immunity in scrub typhus infections were studied in inbred mice employing paired strains of Rickettsia tsutsugamushi differing in virulence. An infectious dose (100 MID50) of the less virulent Gilliam strain resulted in heterologous immune protection against an otherwise lethal challenge (1,000 MLD50) of the virulent Karp strain. Partial heterologous protection against lethal Karp challenge was observed in animals preimmunized with the Gilliam strain as early as 3 days prior to challenge, whereas complete protection against illness and death existed in animals immunized at least 7 days prior to challenge. In the heterologous protection provided by prior Gilliam infection, the role of humoral immunity was not of primary importance for the following reasons: (i) significant levels of complement-fixing antibody against R. tsutsugamushi were not detectable until long after animals were solidly immune; (ii) antibody eventually appearing after Gilliam immunization exhibited a consistently low complement-fixing titer against the immunizing homologous (Gilliam) strain and contained no detectable activity against the heterologous challenge (Karp) strain; and (iii) passive transfer of large quantities of serum from Gilliam immune mice, themselves immune to Karp challenge, failed to protect recipients against a similar challenge. However, protection was afforded by the passive transfer of serum containing antibody against Karp, suggesting a major role for antibody in protection against homologous infection. This heterologous challenge system was particularly useful because it minimized the role of humoral immunity, at least early in the course of infection, and allowed a definitive examination of the cellular response. Cell-mediated immunity played a major role in the heterologous protection observed after Gilliam immunization. This was evidenced by the significant protection against Karp challenge afforded by the passive transfer of spleen cells from animals immunized with Gilliam 7 to 63 days previously. Of the immune spleen cells, only those which were nonadherent, presumably lymphocytes, were capable of transferring passive heterologous protection. This protective effect of nonadherent cells could be ablated by depleting the cell population of thymus-derived or T cells with anti-theta serum and complement prior to transfer but not by use of anti-immunoglobulin serum and complement, which selectively removes bone marrow-derived or B cells. These results suggested that the cell in immune spleens capable of conferring heterologous protection was a T lymphocyte.

Dinitrochlorobenzene Responsivity In Disseminated Coccidioidomycosis: An Inverse Correlation With Complement-Fixing Amtibody Titers

The immunologic status of 25 patients with disseminated coccidiodomycosis was evaluated by serum anticoccidioidin complement-fixing antibody levels, coccidiodin skin tests, and dinitrochlorobenzene (DNCB) sensitization. In the 10 patients who had disseminated disease and a complement-fixing titer of 1:32 or less, responses to DNCB were similar to those of 20 controls. In the 15 patients with disseminated disease and a complement-fixing titer of 1:64 or more, responses to DNCB were statistically significantly diminished compared to controls (p = 0.002). Since the complement-fixing titer is associated with extent of dissemination, these results signify a relationship between diminished DNCB responses and extensive dissemination. Of the several hypotheses which might explain this relationship, we find the most attractive is that of a nonspecific deficiency of cell-mediated immunity developing secondarily to extensive disseminated disease.

Value of the Concomitant Use of Complement Fixation and Immunodiffusion Tests in the Diagnosis of Coccidioidomycosis

Complement fixation titers of 1:2 and 1:4 with coccidioidin are not always of diagnostic significance. The concurrent use of the complement fixation and immunodiffusion tests is an effective means for specific serologic diagnosis of coccidioidomycosis in patients with low levels of complement-fixing antibodies. In routine testing, it is recommended that only sera that are negative for complement-fixing antibodies at 1:8 but positive in the immunodiffusion test with coccidioidin be selected for titration at the 1:2 and 1:4 levels.

Production of self-directed antibody by tumour cells.

INOCULATION of Amsterdam rats with syngeneic tumour cells induced by Schmidt-Ruppin Rous sarcoma virus (SR-RSV) leads to the development of complement-fixing (CF) antibody to the tumour antigen1. The pattern of development of CF antibody in this system, in common with antibody development of the T antigens of other virus-induced tumour cells2–4, has several peculiar characteristics; for example, the level of CF antibody does not reflect immune status, the highest levels of CF antibody occur in tumour-bearing rats, and failure of tumour formation or regression results in low levels of CF antibody which are not elevated by repeated challenge with the same tumour cells. These observations raised an unorthodox question: is the tumour cell itself—in spite of its origin in a non-immunocompetent tissue—the source of some or all of the circulating CF antibody ? Our studies were designed to determine whether Rous sarcoma and other tumour cells have the capacity to produce self-directed antibody in vitro.