Significant Rise In Antibody Titer Research Articles

A study of the immunomodulatory effects of coconut oil extract in broilers experimentally infected with velogenic Newcastle disease virus.

This study aims to evaluate the immunomodulatory effects of coconut oil extract (COE) in broilers experimentally infected with velogenic Newcastle disease virus (vNDV). A total of 150 broiler birds (day-old) were equally divided into five study groups i.e., negative control, positive control, COE-1, COE-2, and COE-3. On day 10, broilers of groups COE-1, COE-2, and COE-3 were supplemented with 1, 2, and 3 mL of COE respectively per liter of drinking water for 15 days. On day 13, 0.1 mL/bird (10-5.25 ELD50) of vNDV was inoculated in broilers of positive control, COE-1, COE-2, and COE-3 groups intramuscularly. During this study, growth performance, morbidity, and mortality rates of each study group were recorded. The antibody titer against NDV was determined on days 7, 14, 21, 28, and 35. The levels of immunoglobulins (IgY and IgM) were also determined on the 7th, 14th, and 21st days post-sheep red blood cells (SRBCs) inoculation. On day 33, avian tuberculin was injected between the 1st and 2nd toes of the left side (intradermally) to measure lymphoproliferative responses. On day 35, the phagocytic activity in the blood was assessed through a carbon clearance assay by injecting carbon black ink into the right-wing vein. The visceral organs having gross lesions were also collected for histopathology. The COE significantly improved the growth performance, and lowered the morbidity and mortality rates of broilers. There was a significant rise in antibody titers against NDV and levels of IgY and IgM antibodies against SRBC in COE-supplemented broilers. The lymphoproliferative response and phagocytic activity were also enhanced. Among COEsupplemented groups, the broilers of the COE-3 group showed a significant increase in growth performance and boosted immune defense. Coconut oil extract has the potential to boost the growth performance and immune status of broilers. It can be used effectively as a feed additive and alternative to antibiotics to prevent the spread of infectious poultry pathogens.

Comparison of three dosing intervals for the primary vaccination of the SARS-CoV-2 mRNA Vaccine (BNT162b2) on magnitude, neutralization capacity and durability of the humoral immune response in health care workers: A prospective cohort study.

The dosing interval of a primary vaccination series can significantly impact on vaccine immunogenicity and efficacy. The current study compared 3 dosing intervals for the primary vaccination series of the BNT162b2 mRNA COVID-19 vaccine, on humoral immune response and durability against SARS-CoV-2 ancestral and Beta variants up to 9 months post immunization. Three groups of age- and sex-matched healthcare workers (HCW) who received 2 primary doses of BNT162b2 separated by 35-days, 35-42 days or >42-days were enrolled. Vaccine induced antibody titers at 3 weeks, 3 and 6-9 months post-second dose were assessed. There were 309 age- and sex-matched HCW (mean age 43 [sd 13], 58% females) enrolled. Anti-SARS-CoV-2 binding (IgG, IgM, IgA) and neutralizing antibody titers showed significant waning in levels beyond 35 days post first dose. The second dose induced a significant rise in antibody titers, which peaked at 3 weeks and then declined at variable rates across groups. The magnitude, consistency and durability of response was greater for anti-Spike than anti-RBD antibodies; and for IgG than IgA or IgM. Compared to the shorter schedules, a longer interval of >42 days offered the highest binding and neutralizing antibody titers against SARS-CoV-2 ancestral and Beta (B1.351) variants beyond 3 months post-vaccination. This is the first comprehensive study to compare 3 dosing intervals for the primary vaccination of BNT162b2 mRNA COVID-19 vaccine implemented in the real world. These findings suggest that delaying the second dose beyond 42 days can potentiate and prolong the humoral response against ancestral and Beta variants of SARS-CoV-2 up to 9 months post-vaccination.

Immuno Modulatory Effects of Hot Aqueous Extract of Ocimum sanctum and Argemone mexicana Leaves in Chicken Model

800x600 The present study was undertaken to study the immuno modulatrory effects of leaves of Ocimum santum (OS) and Argemone mexiana (AM) plants in chicken model. 250 mg/kg body weight oral dose of OS and AM was found ideal and nontoxic in chickens and experimental chickens were fed this dose. Humoral immune response to S. enterica serovar Typhimurium ‘O’ antigen was measured by quantitating the serum antibody level of immunized chickens by ELISA test. There was a significant rise in antibody titre of OS and AM fed chickens in comparison to control group. The antibody titre in the serum samples of HAE of OS and AM fed chickens were (5333.33±674.62) and (4266.67±674.62) respectively, whereas in control group it was 3733.33±533.33. This study indicated that the extract of both plants enhanced the antibody level and acted as a humoral immuno stimulant. Cell mediated immune response (CMI) was assayed by differential lymphocyte count (DLC) and DNCB sensitized hypersensitivity test. DLC revealed increase in lymphocyte count in OS fed group and decrease in lymphocyte count in AM fed group as compared to control group. DNCB test demonstrated 29.89% increase in skin thickness in OS fed group and 34.02% decrease in skin thickness in AM fed group as compared to control group at 24 hour interval. Present study indicated the T cell suppressive impact of hot aqueous extract of AM and stimulator effect of OS. Normal 0 7.8 pt 0 2 false false false EN-US ZH-CN X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;}

Hibernation is associated with depression of T-cell independent humoral immune responses in the 13-lined ground squirrel

Mammalian hibernation consists of periods of low metabolism and body temperature (torpor), interspersed by euthermic arousal periods. The function of both the innate and adaptive immune system is suppressed during hibernation. In this study, we analyzed the humoral adaptive immune response to a T-cell independent (TI-2) and a T-cell dependent (TD) antigen. Thirteen-lined ground squirrels were immunized in summer or during hibernation with either a TI-2 or TD antigen on day 0 and day 14. Blood was drawn on day 0, 7, 14, 21 and 28. Both types of antigens induced a significant rise in antibody titer in summer animals. Much to our surprise, however, only immunization with the TD antigen, and not with the TI-2 antigen induced a humoral response in hibernators. Flow cytometric analysis of CD4 (helper T-lymphocytes), CD8 (cytotoxic T-lymphocytes) and CD45RA (B-lymphocytes) in blood, spleen and lymph nodes ruled out massive apoptosis as explanation of the absent TI humoral response during hibernation. Rather, reduced TI-2 stimulation of B-lymphocytes, possibly due to lowered serum complement during torpor, may explain the reduced antibody production in response to a TI-2 antigen. These results demonstrate that hibernation diminishes the capacity to induce a TI-2 humoral immune response, while the capacity to induce a humoral response to a TD antigen is maintained.

Effect of Adjuvants on Antibody Titer of Synthetic Recombinant Light Chain of Botulinum Neurotoxin Type B and its Diagnostic Potential for Botulism

Botulism is a neuroparalytic disease caused by Clostridium botulinum, which produces seven (A-G) antigenically diverse neurotoxins (BoNTs). BoNTs are the most poisonous substances known to humans, with a median lethal dose (LD₅₀) of approximately 1 ng/kg of body weight. Owing to their extreme potency and lethality, they have the potential to be used as a bioterrorism agent. The mouse bioassay is the gold standard for the detection of botulinum neurotoxins; however, it requires at least 3-4 days for completion. Attempts have been made to develop an ELISA-based detection system, which is potentially an easier and more rapid method of botulinum neurotoxin detection. The present study was designed using a synthetic gene approach. The synthetic gene encoding the catalytic domain of BoNT serotype B from amino acids 1-450 was constructed with PCR overlapping primers (BoNT/B LC), cloned in a pQE30 UA vector, and expressed in an E. coli M15 host system. Recombinant protein production was optimized at 0.5 mM IPTG final concentration, 4 h post induction, resulting in a maximum yield of recombinant proteins. The immunogenic nature of the recombinant BoNT/B LC protein was evaluated by ELISA. Antibodies were raised in BALB/c mice using various adjuvants. A significant rise in antibody titer (p<0.05) was observed in the Alum group, followed by the Titermax Classic group, Freund's adjuvant, and the Titermax Gold group. These developed high-titer antibodies may prove useful for the detection of botulinum neurotoxins in food and clinical samples.

An outbreak of airborne tularaemia in France, August 2004.

Fifteen tularaemia cases were identified after a holiday spent at a converted mill in the Vendee region in France, between 9 and 12 August 2004. The mill was visited, and descriptive, retrospective cohort and environmental investigations were conducted. The 39 people who had stayed at the mill between 24 July and 11 August were asked about symptoms, exposure to food and animals, and leisure activities. A case was defined as a person with evidence of fever and a positive serology (seroconversion or significant rise in antibody titre, or a single titre) = 40. Culture for Francisella tularensis and polymerase chain reaction (PCR) diagnosis was carried out for drinking water, firewood, and domestic animals at the mill. Fifteen cases of tularaemia (38%) were confirmed. Twelve of the cases (80%) had the pulmonary form. None of the patients was admitted to hospital. There was a strong association between infection and participation in a dinner at the mill on 4 August (p&lt;10-8). One of the three dogs present in the dining room was serologically positive for F. tularensis. Results of analysis of environmental samples were negative. These investigations confirmed the occurrence of a cluster of 15 tularaemia cases, in patients who were infected on the evening of 4 August, in a mill in Vend¨¦e, an endemic area for tularaemia. The investigations highlight the existence of nonspecific and benign pulmonary forms of the illness in France. The pulmonary form of infection in the human cases and the positive serology of the dog suggest contamination by inhalation of contaminated particles from the dog¡¯s fur disseminated by the dog shaking itself.

Enterovirus infections in Germany: comparative evaluation of different laboratory diagnostic methods.

The diagnosis of an enterovirus infection may be achieved through direct virus detection from fecal or cerebrospinal fluid (CSF) samples by virus isolation or PCR. Serologically, a significant rise in antibody titer may be detected and different enteroviral types can be differentiated using the neutralization assay. We investigated the contribution of these different laboratory parameters to the diagnosis of enterovirus infections occurring in the Frankfurt am Main area during the years 1997 to 1999, including an echovirus 30 outbreak in a group of children with aseptic meningitis in 1997. Samples were referred from 1,013 patients; virus isolation was attempted from 579 CSF specimens and from 400 stool samples. 208 CSF samples were tested by PCR. During the echovirus 30 outbreak we identified 22.3% of samples as positive, almost exclusively echovirus 30. In 1998 only 7.1% of samples were positive and a rather broad range of agents was isolated. In 1999 10.4% were positive, predominantly coxsackie B5 and echovirus 11. We could show that in acute enterovirus infections, virus detection by cell cuLture and PCR is superior to serological methods (neutralization assay and IgM assay). For virus isolation, there was a higher rate of positives from stool compared to CSF (1997: 27.8% versus 25%; 1998: 14.4% versus 3%; 1999: 17.9% versus 8.5%). When comparing PCR and virus isolation from the CSF, the former yielded a higher rate of positive results but was not clearly superior to virus isolation from CSF. The recommended method for the diagnosis of acute enterovirus infections is virus isolation from feces. In cases of suspected aseptic meningitis virus isolation and PCR are valuable for the direct detection of virus in CSF.

Rubella reinfection; role of neutralising antibodies and cell-mediated immunity

Background: Rubella virus may be transmitted to the fetus following rubella reinfection in early pregnancy. The mechanisms responsible for maternal-fetal transmission in women with pre-existing rubella antibodies are, however, unclear. Objectives: To evaluate the protective role of rubella specific neutralising antibodies and cell-mediated immunity in rubella reinfection. Study design: Rubella Nt antibodies were measured in sera obtained from: women who experienced rubella reinfection during pregnancy, volunteers experimentally challenged with rubella vaccine and women attending for routine rubella antibody screening. Cell-mediated immunity was assessed by measuring rubella specific LT responses among women who had experienced rubella reinfection during pregnancy. Results: Some women experienced rubella reinfection during pregnancy despite the presence of Nt antibodies in sera obtained before contact. Only 2 of 13 (15.3%) volunteers with low levels (< 15 IU/ml) of rubella antibody had detectable Nt antibodies prior to experimental challenge. Despite this, they did not develop rubella viraemia following challenge and virus excretion was detected in only one case, although the majority ( 11 13 , 84.6%) demonstrated a significant rise in antibody titre. Among pregnant women screened as having a low level of rubella antibody antenally, only 37% had detectable Nt antibodies. Among 23 women who experienced rubella reinfection during pregnancy 4 months to 6 years (mean 32 months) previously, 20 (86.9%) had a positive rubella-specific LT response. Only one of 4 cases where rubella virus was transmitted to the fetus failed to produce a a specific LT response. Conclusions: This study indicates that rubella reinfection is not associated with a lack of Nt antibodies or persistent impairment of rubella-specific LT responses.

Exanthema subitum and human herpesvirus 6 infection: clinical observations in fifty-seven cases.

Exanthema subitum had been speculated to be a viral disease although its pathogen is unknown. Human herpesvirus 6 (HHV-6), first isolated in 1986, was proved by Yamanishi et al. to be the causal agent of exanthema subitum. To evaluate the role of HHV-6 as the causal agent in clinically diagnosed exanthema subitum, we tested for HHV-6 antibody in 57 infants with clinical exanthema subitum and exanthema subitum-like rash without fever. Of the 53 patients with clinical exanthema subitum 43 showed seroconversion or a significant rise in antibody titer to HHV-6, 7 were seropositive without significant rise and 3 remained seronegative. The clinical manifestations of these 43 infants with serologically confirmed HHV-6 infection were consistent with the classical characteristics of exanthema subitum. The 4 patients with atypical exanthema subitum showed significant rises in antibody titer. Our results therefore show that the majority of cases with typical clinical manifestations of exanthema subitum had HHV-6 infection. Most cases with HHV-6 infection had the typical clinical course of exanthema subitum, and a few cases might show an afebrile exanthema subitum-like rash.

Clinical, Serological and Biochemical Studies on Lumpy Skin Disease

Abstract Clinical signs of lumpy skin disease (LSD) were recorded. The period of fever was associated with serious biochemical alterations. Such alterations were obvious between 7th and 14th days from the initial symptoms. LSD infection in cattle produced transient changes in minerals and trace elements as well as malfunctional disturbances in both liver and kidneys. Moreover, the effects on the lymphoid tissue caused excessive production of immunoglobulins in the form of gamma-globulins. The changes in gamma-globulin also roughly paralelled the changes in serum neutralizing antibodies. Serum neutralizing antibodies developed on the second day from the onset of clinical signs and were detectable until the day 210. A significant rise in antibody titre was recorded between 21 and 42 days. This increase in antibody titre is important in diagnosis of LSD.

Deafness Associated With Lassa Fever

Viral infections are now being recognized with increasing frequency to be causes of inner ear disorders, including deafness, vertigo, and facial palsy. 1 Sudden deafness has been associated with a significant rise in antibody titers directed against adenovirus, parainfluenza, and herpesviruses. 2 More recent serological surveys of patients who have idiopathic sudden hearing loss demonstrated seroconversions for antibodies against single or multiple viral agents. The most common viruses implicated were mumps, rubeola (measles), varicella-zoster, cytomegalovirus, and influenza B. It was interesting to note that the incidence of viral seroconversion and sudden hearing loss tracked each other closely, suggesting a relationship between viral infections and idiopathic sudden deafness. Sudden deafness was most prevalent in the spring in Boston during a 3-year study. 3 In England, serological studies of patients with sudden deafness revealed that mumps, measles, and herpes zoster were most commonly associated. 4 Histopathologic study of temporal bones removed during

牛ウイルス性下痢・粘膜病生ワクチンの乳牛における抗体応答と胎子感染

The antibody response and possibility of fetal infection were assessed in cows that had been vaccinated with a bovine viral diarrhea-mucosal disease live virus vaccine (No.12-43 strain). The seroconversion rate was examined in 92 vaccinated cows. In those cows which had antibody titer of 4 or lower at the time of vaccination, the seroconversion rate reached almost 100%, while in those with antibody titer of 8 or higher, the rate tended to be lower in the cows which showed higher antibody levels against the No.12 and Nose strains. Twenty-six antibody-negative cows were vaccinated and their antibody titers were determined two months later. The mean antibody titers (n=26) against the No.12, Nose, and KS86-1 strains were 4806.5, 1170.0, and 121.4, respectively. Rises in antibody titer were also recognized against field-isolated virus strains obtained from cattle in Hokkaido, and the mean antibody titers against three isolates were 460.2, 135.0, and 131.5. The mean antibody titer (n=6) determined one year after the vaccination was 512 against the No.12 and Nose strains, and 64 against the K (+) strain. In some cases, however, in spite of a high antibody level against the KS86-1 strain, a significant rise in antibody titer was recognized when antibody levels against the No.12 and Nose strains were low. This suggested that some field strains may greatly be different serologically from vaccine strains.Eight antibody-negative pregnant cows were vaccinated, and all of them showed a significant rise in antibody titer after vaccination. Furthermore, antibody to the No.12 strain was detected in 5 pre-colostrol calves born to these 8 cows, suggesting fetal infection.The present findings indicated that the live virus vaccine used in this study induced an antibody response effective enough for prevention of bovine viral diarrhea-mucosal disease, although the use for pregnant cows should be avoided.

Immune response to trivalent inactivated influenza vaccine in young and elderly subjects

The antibody response (determined using the single radial haemolysis in gel technique) to inactivated whole-virion trivalent influenza vaccine [A/Leningrad/360/86(H3N2), A/Taiwan/5/87 and B/Ann Arbor/1/86], recommended for the 1987–88 winter season in Italy, in 49 elderly (age ⩾ 60 years) subjects was compared with the response in 23 young adult (age < 60 years) volunteers. The subjects were prevalently healthy and a high percentage of young and old people had been repeatedly immunized against influenza in previous years. No significant differences were detected among age groups; moreover, the immune response measured by seroconversion or by a significant rise in antibody titre was constantly low.

黒毛和種肥育牛に見られた牛ライノウイルス感染症

There was an outbreak of an acute respiratory disease in cattle in Nagasaki Prefecture in March, 1987. The 45 cattle, all from different places in Nagasaki Prefecture from outsideof the prefecture, involved in the outbreak showed fever, coughing, nasal discharge, labored breathing and diarrhea five days after they were introduced and five of them died.Pasteurella haemolytica was isolated from six nasal swab specimens in seven ill cattle (85.7%). Mycoplasma SP. was isolated from two of seven specimens (28.6%). Two cytopathogenic virus strains were isolated in MDBK cell cultures from nasal swabs of cattle with markedleukopenia.The isolants were readily inactivated by acid and heating at 50°C for 30 minutes, but they resisted chloroform. The type of their nucleic acid was determined to be RNA. Immunoelectron microscopy using convalescent serum revealed picornavirus-like particles in cultured material.The isolants were neutralized with antiserum against the Sd-1 strain of bovine rhinovirus type 1.A significant rise in antibody titer was shown against the isolants in convalescent serum of the ill cattle, but not against bovine respiratory syncytiai virus, bovine adenovirus type 7, or bovine entero virus. A small rise in antibody titer against bovine herpesvirus type 1, parainfluenza virus type 3 and bovine viral diarrhea mucosal disease virus, was shown. It is considered, however, that such a sero-conversion may be due to vaccination of combined vaccine against these viral agents.Serologic survey against the isolated virus in sera collected from 195 cattle in 1987 in Nagasaki Prefecture revealed that 73. 5% of those over one year old were antibody positive, while 29. 9% of those from four to 10 months old particulaly have a tendency to show a low positive rate.

Serological Confirmation of Group C Streptococcal Pneumonia

Lancefield group C streptococci are a common cause of infections in animals but less frequently cause disease in humans. Studies by Duma [1] and Mohr [2] showed that only O^o-OJ^o of streptococci isolated from cultures of human blood were identified as group C. Pneumonia due to group C Streptococcus has been reported in eight individuals [2-7]: five patients were previously healthy, one was a chronic smoker, one had a hiatus hernia and a bleeding esophageal ulcer, and one had underlying Hodgkin's disease. We describe a patient with pneumonia due to group C Streptococcus, peritonitis with underlying congenital heart disease, and chronic renal failure who was receiving continuous ambulatory peritoneal dialysis. The etiologic role of the group C Streptococcus in the illness of this patient was confirmed by isolating the organism from the blood and peritoneal fluid and by demonstrating a significant rise in antibody titer to group C streptococcal carbohydrate antigen in convalescent sera.

Antibody response to bacteriophage hyaluronidase in acute glomerulonephritis after group A streptococcal infection.

In a test of the hypothesis that lysogeny of group A streptococci by a temperate bacteriophage might confer nephritogenicity, 283 sera from 69 patients were examined for IgG and IgM antibodies to M 49 streptococcal bacteriophage hyaluronidase. The IgG and IgM response to bacteriophage hyaluronidase was greatest in M 49 streptococci-infected individuals with nephritis, but M 49 streptococci-infected subjects without nephritis also had a greater immune response than did subjects infected with serotypes other than M 49. Although antibody to bacterial hyaluronidase was detected in all Streptococcus-infected groups, antibody to M 49 streptococcal bacteriophage hyaluronidase usually was found in only M 49 streptococci-infected patients. Although the greatest IgG and IgM antibody response to bacteriophage hyaluronidase can be demonstrated in individuals with glomerulonephritis, the antibody response does not indicate a direct relation of lysogeny and nephritis because subjects with and without nephritis after M 49 streptococcal infection all had a significant rise in antibody titer.

Single radial complement fixation test using NP-containing plates: a simple and sensitive method for the detection of influenza infection

The single radial complement fixation (SRCF) test using nucleoprotein (NP) was compared with the haemagglutination inhibition (HAI) test in the course of the evaluation of the protective efficacy of influenza vaccine. In the case of persons who were not vaccinated, the percent incidence of infection was almost the same (which confirmed by HAI test or by SRCF test), whereas in the case of vaccinees, there was a significant difference between the incidence confirmed by HAI (7.9%) and SRCF (19.4%) tests. The SRCF test was shown to be a simple and sensitive method for detection of a significant rise in antibody titre against influenza virus.

Testing for Streptococcal Pharyngitis-Reply

In Reply.— We share Dr Odio's concerns that evaluations of group A streptococcal antigen-detection kits should provide clinically relevant information and that comparisons of the new procedures be made using a welldocumented reference method, or the gold standard. As Dr Odio noted, a confirmed diagnosis of streptococcal pharyngitis requires a significant rise in antibody titer between acute and convalescent serum samples. Not being willing to wait the two to three weeks following onset of symptoms required for collection of convalescent serum samples, physicians have looked to the traditional culture and investigated the faster antigen-detection products as more practical alternatives. In the absence of a rapid serological test to confirm infection, the throat culture is merely a screen to determine the presence or absence of group A streptococci, and the rapid antigendetection kits serve the same purpose. Since the objectives of the two tests are identical, a competently performed throat culture

A new serological assay for Staphylococcus aureus infections: detection of IgG antibodies to S. aureus lipase with an enzyme-linked immunosorbent assay.

Purified Staphylococcus aureus lipase was used as antigen in an enzyme-linked immunosorbent assay (ELISA) that detected IgG antibodies in 169 patients with infections due to S. aureus, in 122 patients with infections not due to S. aureus, and in 167 healthy controls. Eighty-eight percent (21 of 24) of the patients with endocarditis due to S. aureus showed a positive level of antibody to lipase or a significant change in antibody titer during the first month, as did 89% (17 of 19) and 28% (5 of 18) of the patients with complicated and uncomplicated septicemia due to S. aureus, respectively. The specificity for S. aureus infections was high; only one patient in the non-S. aureus endocarditis and septicemia groups showed a significant rise in antibody titer, and this rise did not reach a positive antibody level. Patients with recurrent furunculosis or chronic osteomyelitis due to S. aureus responded in only 15% and 23% of cases, respectively. We suggest that the antibody-to-lipase ELISA could be used as a valuable complement to other serological assays in diagnosing serious S. aureus infections because of its high sensitivity and specificity.

Incidence of immune responses following 102 infusions of autoplex in 18 hemophilic patients with antibody to factor VIII

An activated prothrombin complex concentrate (Autoplex) was infused for the treatment of 102 bleeding episodes in 18 hemophilia A patients with antibody to factor VIII who were previously known as high responders. Among 95 bleeding episodes treated with a single infusion of the concentrate [43–107 factor VIII correcting units (FECU)/kg], only 1 anamnestic response was observed. On the contrary, a significant rise in antibody titer occurred following 2 of 4 double (at 8–12 hr interval) and all 3 multiple (over3 –10 days) infusions of Autoplex. The occurrence of immune responses may be explained by the presence of factor VIII coagulant antigen (VIII:CAg) in the 26 batches of Autoplex tested by two-site immunoradiometric assay (10-–36 U/vial). The anamnestic response was not correlated to the batch used nor to the amount (0.6–7.8 U/kg/day) of VIII:CAg infused per day. However, exposure to the concentrate over several days appeared to be the major predisposing factor for an immune response.