Significant Decrease In Titer Research Articles

Comparative study of total antibody titer against SARS-CoV-2 spike protein between male and female COVID- 19 patients of different age groups in UAE

Abstract Introduction/Objective Currently, there is increasing evidence that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes men to experience more serious symptoms and have a higher mortality rate than women, but the associations between gender and age groups are still elusive. This study aimed to examine the associations with age, gender, and clinical parameters of total antibody responses against the spike protein of SARS- CoV-2 after infection in UAE population. Methods/Case Report In this study, spike protein antibody titer estimation for COVID-19 positive individuals (n = 1070) was determined. A cross-sectional study design was planned in which patients were divided into nine groups (based on their age) and further subdivided into two groups based on their genders (9 x 2). Serum was collected from the patients after 17 days of diagnosis as COVID-19 positive by RT-PCR method. Concentrations of SARS-CoV-2 Total antibody (COV2T) were measured by chemiluminescent immunoassay using ADVIA Centaur® XPT systems. We used a mixed effects model to investigate the potential associations of antibodies by bootstrapping t-tests of the putative effects of gender and age of the individuals. Results (if a Case Study enter NA) There were significant differences (P< 0.05) between males and females for SARS-CoV-2 total antibody reactivity. Total 645 (50.4%) male were found reactive compared to 425 (31.2%) female. Noteworthy, the group having middle-aged (41-50 years) participants depicted a higher antibody titer in both males and female against SARS-CoV-2. A significant decrease in titers also observed with different age groups. Highest number of reactive individuals were observed in 41-50 years age group (31%), followed by 31-40 years (27.34%), 51- 60 years (15.21%) and 21-30 years (13.04%). Same pattern of number of reactive individuals was found in male and female of different age group. Moreover, despite there being a weak significant positive association between age and total antibody titre in male patients, while there was no significant correlation between gender and age for the antibody response. Conclusion In a nutshell, total antibody (COV2T) reactivity was found significantly associated with male group and that was highest in 41-50 years age group, irrespective of the gender. These findings are crucial to treat and care for male and female patients infected with COVID-19 at hospitals.

Monitoring of SARS-CoV-2 Specific Antibodies after Vaccination

Vaccination is considered the most important measure to control the COVID-19 pandemic. Extensive follow-up studies with distinct vaccines and populations are able to promote robust and reliable data to better understand the effectiveness of this pharmacologic strategy. In this sense, we present data regarding binding and neutralizing (achieved by surrogate ELISA assay) antibodies throughout time, from vaccinated and previously infected (PI) health care workers (HCW) in Portugal. We analyzed serum samples of 132 HCW, who were vaccinated and with previous SARS-CoV-2 infection. Samples were collected before vaccination (baseline, M1), at second dose vaccine uptake (M2), and 25–70 days (M3) and 150–210 days (M4) after the second dose for vaccinated individuals. The IgG (anti-RBD/S) antibody geometric mean titers found on vaccinated HCW at M2 (GM = 116.1 BAU/mL; CI: 92.3–146.1) were significantly higher than those found on PI HCW at recruitment (M1) (GM = 35.9 BAU/mL; CI:15.4–83.4), and the neutralizing antibodies (nAb) were similar between these groups, of 93.2 UI/mL (95% CI 73.2–118.5) vs. 84.1 UI/mL (95% CI 40.4–155.9), respectively. We detected around 10-fold higher IgG (anti-RBD/S) antibodies titers in M3 when compared with M2, with a slight but significant decrease in titers from 36 days after the second dose vaccine uptake. The increase of nAb titers was correlated with IgG (anti-RBD/S) antibodies titers; however, in contrast to IgG (anti-RBD/S) antibodies titers, we did not detect a decrease in the nAb titer 36 days after a second vaccine dose uptake. At M4, a decrease of 8-fold in binding IgG (anti-RBD/S) and nAb was observed. No significant differences in antibody titers were observed by sex, age or chronic diseases. Our results suggest that IgG (anti-RBD/S) antibodies titers and nAb titers could be correlated, but an ongoing follow up of the cohort is required to better understand this correlation, and the duration of the immune response.

Incomplete inactivation of atypical scrapie following recommended autoclave decontamination procedures.

Prions are highly resistant to the decontamination procedures normally used to inactivate conventional pathogens. This is a challenging problem not only in the medical and veterinary fields for minimizing the risk of transmission from potentially infective sources but also for ensuring the safe disposal or subsequent use of animal by-products. Specific pressure autoclaving protocols were developed for this purpose, but different strains of prions have been reported to have differing resistance patterns to established prion decontamination procedures, and as additional TSE strains are identified it is necessary to determine the effectiveness of such procedures. In this study we assessed the efficacy of sterilization using the EU recommended autoclave procedure for prions (133°C, 3 Bar for 20min) on the atypical or Nor98 (AS/Nor98) scrapie strain of sheep and goats. Using a highly sensitive murine mouse model (tg338) that overexpresses ovine PrPC , we determined that this method of decontamination reduced the infectivity titre by 1010 . Infectivity was nonetheless still detected after applying the recommended autoclaving protocol. This shows that AS/Nor98 can survive the designated legislative decontamination conditions, albeit with a significant decrease in titre. The infectivity of a classical scrapie isolate subjected to the same decontamination conditions was reduced by 106 suggesting that the AS/Nor98 isolate is less sensitive to decontamination than the classical scrapie source.

Evidence for the association between IgG-antimitochondrial antibody and biochemical response to ursodeoxycholic acid treatment in primary biliary cholangitis.

Antimitochondrial antibody (AMA) is considered the serological hallmark of primary biliary cholangitis (PBC), while data regarding the profile of AMA during ursodeoxycholic acid (UDCA) treatment are scarce. Here, we assessed the influence of UDCA treatment on titers of AMA and factors relevant to its production. Serum IgA-AMA, IgM-AMA, IgG-AMA, B cell-activating factor of the tumor necrosis factor family (BAFF), and the frequency of circulating plasmablasts were detected in PBC patients, including those who received UDCA therapy for 24 weeks, healthy controls, chronic hepatitis B patients, and autoimmune hepatitis patients. Consecutive liver sections from controls and PBC patients were stained by immunohistochemistry for detection of intrahepatic CD38+ , IgA+ , IgM+ , and IgG+ cells. Significant decrease in titers of IgG-AMA was found only confined to PBC patients with biochemical response to UDCA treatment (P = 0.005), and similar pattern was also observed at week 24 in quantifying circulating plasmablasts (P = 0.025) and serum BAFF (P = 0.013). Notably, positive correlation between serum BAFF levels and titers of IgG-AMA, and the frequency of circulating plasmablasts were observed in PBC patients (r = 0.464, P = 0.034 and r = 0.700, P < 0.001, respectively). Additionally, in situ staining revealed significant accumulation of CD38+ and IgG+ cells within the portal tracts of PBC liver. Decreased titers of serum IgG-AMA are associated with biochemical response to UDCA treatment, implicating the potentiality of this hallmark in therapeutic response evaluation and the beneficial effect of UDCA on humoral immunity in PBC patients.

Persistence of the protective immunity and kinetics of the isotype specific antibody response against the viral nucleocapsid protein after experimental Schmallenberg virus infection of sheep.

Schmallenberg virus (SBV) is an Orthobunyavirus that induces abortion, stillbirths and congenital malformations in ruminants. SBV infection induces a long lasting seroconversion under natural conditions. The persistence of the protective immunity and the isotype specific antibody response upon SBV infection of sheep has however not been studied in detail. Five sheep were kept in BSL3 facilities for more than 16 months and subjected to repeated SBV infections. Blood was regularly sampled and organs were collected at euthanasia. The presence of SBV RNA in serum and organs was measured with quantitative real-time PCR. The appearance and persistence of neutralizing and SBV nucleoprotein (N) isotype specific antibodies was determined with virus neutralization tests (VNT) and ELISAs. The primo SBV infection protected ewes against clinical signs, viraemia and virus replication in organs upon challenge infections more than 15 months later. Production of neutralizing SBV specific antibodies was first detected around 6 days post primo-inoculation with VNT and correlated with the appearance of SBV-N specific IgM antibodies. These IgM antibodies remained present for 2 weeks. SBV-N specific IgG antibodies were first detected between 10 and 21 dpi and reached a plateau at 28 dpi. This plateau remained consistently high and no significant decrease in titre was found over a period of more than 1 year. Similar results were found for the neutralising antibody response. In conclusion, the SBV specific IgM response probably eliminates SBV from the blood and the protective immunity induced by SBV infection protects sheep against reinfection for at least 16 months.

Comparative Study of Antinuclear Antibody Detection by Indirect Immunofluorescence and Enzyme Immunoassay in Lupus Patients

To evaluate the value of immunofluorescent and ELISA techniques in early diagnosis of systemic lupus erythematosus (SLE) and to find out whether there is a correlation between Antinuclear antibodies (ANA) pattern and prognosis by observing clinical score changes using British Isles Lupus Assessment Group score. The study included 75 SLE patients, 11 disease control group, and 18 healthy control group. ANA and ds-DNA antibodies detection were done by ELISA and Immunofluorescence for all groups. Immunofluorescence technique is more sensitive for ANA and ds-DNA detection than ELISA technique (100% versus 90.7%,and 93% versus 89.3% respectively); ELISA showed 89.7 % specificity for ANA detection compared to 86.2% for Immunofluorescence, and both have 100% specificity for ds-DNA detection ;homogenous ANA pattern, showed statistically significant higher BILAG score compared to speckled pattern either at the start of the study or after the follow up period (p = 0.000); and ds-DNA titer showed statistically significant decrease in titer after therapy (p = 0.01). ANA detection by Immunofluorescence is more sensitive and effective screening assay in patients with clinical features of SLE and both ds-DNA titer by ELISA and BILAG score for severity index are considered the best markers for follow-up.

Effect of Selected Water Temperatures Used in Mycoplasma gallisepticum Vaccine Reconstitution on Titer at Selected Time Intervals

Numerous methods are currently used throughout the poultry industry for the administration of vaccines. Each utilizes water for vaccine reconstitution and/or administration, including two of the three commercially available live Mycoplasma gallisepticum (MG) vaccines. Selected water temperatures were used to reconstitute and/or dilute the three commercially available live MG vaccines. Water temperatures included 4 C, 22 C (room temperature), and 32 C, and titer (color change units) was recorded at four time intervals, at point of reconstitution (time 0), 15, 30, and 60 min postreconstitution of the vaccines (time periods 15, 30, and 60, respectively). Results for F strain MG (FMG) vaccine showed significant decreases in titer from time 0 to time 15 for the 22 C and 32 C water temperatures but no significant decrease for any time period for FMG reconstituted with 4 C water. For 6/85 strain MG no significant difference in titer was noted for any of four time periods within any of the three water temperatures. For ts-11 strain MG a significant decrease was observed in titer at each of the four postdilution time periods when diluted with 32 C water. There was no significant decrease in titer at any time period for ts-11 MG vaccine when diluted with either 4 C or 22 C water.

Pharmacokinetics and Effects of Ribavirin following Intraventricular Administration for Treatment of Subacute Sclerosing Panencephalitis

Ribavirin is a broad-spectrum antiviral drug with inhibitory activity against many RNA viruses, including measles virus. Five patients with subacute sclerosing panencephalitis (SSPE) were treated with ribavirin by intraventricular administration. Although there were transient side effects attributed to ribavirin, such as drowsiness, headache, lip and gingival swelling, and conjunctival hyperemia, intraventricular ribavirin therapy was generally safe and well tolerated. The cerebrospinal fluid (CSF) ribavirin concentration decreased, as described by a monoexponential function, after a single intraventricular dose. There was considerable interindividual variability, however, in the peak level and half-life. We aimed to adjust the individual dose and frequency of intraventricular administration based on the peak level and half-life of ribavirin in the CSF in order to maintain the CSF ribavirin concentration at the target level. Clinical effectiveness (significant neurologic improvement and/or a significant decrease in titers of hemagglutination inhibition antibodies against measles virus in CSF) was observed for four of five patients. For these four patients, CSF ribavirin concentrations were maintained at a level at which SSPE virus replication was almost completely inhibited in vitro and in vivo, whereas the concentration was lower in the patient without clinical improvement. These results suggest that intraventricular administration of ribavirin is effective against SSPE if the CSF ribavirin concentration is maintained at a high level. Intraventricular ribavirin therapy should be pursued further for its potential use for patients with SSPE and might be applied in the treatment of patients with encephalitis caused by other RNA viruses.

Long-term follow-up study of serum immunoglobulin G and immunoglobulin A antibodies after Helicobacter pylori eradication.

There have been few studies concerning serum titers of anti-Helicobacter pylori immunoglobulin G (IgG) antibody >12 months after eradication of the original infection. Moreover, clinical usefulness of immunoglobulin A (IgA) antibody levels remains to be established. The purpose of this study was to investigate long-term responses of serum IgG-specific and IgA-specific antibodies to H pylori in children after eradication therapy. A total of 34 children, 2 to 17 years of age (mean: 11.7 years) with H pylori-associated gastroduodenal disease received eradication therapy (proton pump inhibitor-based dual or triple regimens). Diagnoses included nodular gastritis (n = 8), gastric ulcer (n = 7), and duodenal ulcer (n = 19). Upper gastrointestinal endoscopy and biopsy were performed before the therapy and at 1 to 2 months' posttreatment. H pylori infection and eradication were defined by biopsy-based tests; eradication was successful in 28 patients and unsuccessful in 6. Pretreatment IgG was positive in 30 patients (88. 2%), and the IgA was positive in 31 (91.2%), who were entered into this study (duration </=24 months). Serum samples were obtained before treatment and at 1, 3, 6, 12, 18, and 24 months' posttreatment. IgG and IgA antibodies were measured using commercial enzyme immunoassay kits (HM-CAP and PP-CAP; Enteric Products, Inc, New York, NY). Compared with pretreatment values, IgG and IgA antibodies significantly and steadily decreased at 1 through 24 months' posttreatment in successfully treated patients. A decrease in titer of the IgA class was significantly greater than that of the IgG class at 1 to 12 months' follow-up. There was no significant decrease in titer of either antibody in all but 2 patients with eradication failure. A >/=30% decrease in titer of the IgA antibody at 6 months indicated eradication with sensitivity of 90.5% and specificity of 100%. For the IgG antibody, a 30% decrease at 12 months showed equal sensitivity and specificity. Seroreversion rates of IgG and IgA antibodies were 53% and 48% at 12 months and were 86% and 81% at 24 months, respectively. The mean periods from the completion of eradication therapy to seroreversion of IgG and IgA antibodies were 11.2 +/- 7.0 and 11.6 +/- 7.8 months, respectively (not significantly different). A higher pretreatment titer of IgG antibody was related to a longer period of seroreversion (r = 0.44). In one patient, (13)C-urea breath test-confirmed reinfection was accompanied by reappearance of significant titers of the IgG and IgA antibodies. A serology test is useful for evaluating eradication in children. Approximately half of patients with successful eradication remained to be IgG-seropositive and IgA-seropositive at 12 months' posttreatment. When a decrease titer in antibody is used for assessing eradication, an endpoint of >/=6 months is required. The IgA antibody may be a more convenient indicator of H pylori status than is the IgG antibody.

Evaluation of an immunofluorescence assay for specific detection of immunoglobulin G antibodies directed against Helicobacter pylori, and antigenic cross-reactivity between H. pylori and Campylobacter jejuni

An immunofluorescence assay (IFA) for the detection of immunoglobulin G antibodies directed against Helicobacter pylori was evaluated by comparing 20 serum specimens from patients with a positive urease test on biopsy material and 20 serum specimens from patients with a negative test and with defined clinical symptoms. The resulting anti-H. pylori titers were classified as follows: negative, less than or equal to 64; borderline, 128; and positive, greater than or equal to 256. By using these criteria, the IFA was subsequently tested, using 100 serum specimens from patients with gastric complaints. Overall, the titers were 71% positive, 10% borderline, and 19% negative. Depending on the patients' biopsy urease test results, the sensitivity and specificity of the assay were calculated to be 96%. Furthermore, these sera were classified into three subgroups on the basis of clinical manifestations: gastritis with 74% positive and 10% borderline titers, duodenal ulcer with 84% positive and 4% borderline titers, and gastric ulcer with 52% positive and 16% borderline titers. A serologic follow-up study was carried out with three patients with gastric ulcers who had been treated with colloidal bismuth subcitrate for 4 weeks and erythromycin for the final 2 weeks. The results indicate that a significant decrease in titer could be expected within 9 to 12 months after successful therapy, as determined by repeated negative CLO tests. Absorption experiments demonstrated that possible cross-reactivity between H. pylori and C. jejuni did not influence serodiagnosis.

Toxoplasmosis serology: an efficient hemagglutination procedure to detect IgG and IgM antibodies

In search of an efficient but simple, low cost procedure for the serodiagnosis of Toxoplasmosis, especially suited for routine laboratories facing technical and budget limitations as in less developed countries, the diagnostic capability of Hematoxo, an hemagglutination test for toxoplasmosis, was evaluated in relation to a battery of tests including IgG- and IgM-immunofluorescence tests, hemagglutination and an IgM-capture enzymatic assay. Detecting a little as 5 I.U. of IgG antitoxoplasma antibodies, Hematoxo showed a straight agreement as to reactivity and non-reactivity for the 443 non-reactive and the 387 reactive serum samples, included in this study. In 23 cases presenting a serological pattern of acute toxoplasmosis and showing IgM antibodies, Hematoxo could detect IgM antibodies in 18, indicated by negativation or a significant decrease in titers as a result of treating samples with 2-mercapto-ethanol. However, a neat increase in sensitivity for IgM specific antibodies could be achieved by previously removing IgG from the sample, as demonstrated in a series of acute toxoplasmosis sera. A simple procedure was developed for this purpose, by reconstituting a lyophilized suspension of Protein A--rich Staphylococcus with the lowest serum dilution to be tested. Of low cost and easy to perform, Hematoxo affords not only a practical qualitative procedure for screening reactors and non-reactors, as in prenatal services, but also quantitative assays that permit to titrate antibodies as well as to identify IgM antibodies.

Acute salpingitis with Chlamydia trachomatis isolated from the fallopian tubes: clinical, cultural, and serologic findings.

Chlamydia trachomatis was recovered from the fallopian tubes of ten women with acute salpingitis. The median age of the patients was 19 years. The duration of pelvic pain before consulting a physician ranged from three to 27 days (median, seven days). Half of the patients complained of irregular bleeding, and nine reported increased vaginal discharge. One patient had a rectal temperature of greater than 38 C, and one had an erythrocyte sedimentation rate of less than 15 mm/hr. At laparoscopy, mild inflammatory changes were seen in the tubes of three patients, five had moderately severe inflammation, and two had pelvic peritonitis. C. trachomatis could not be isolated from the cervix of two patients. Paired sera were available from eight patients, six of whom had a significant rise in titer of IgG antibodies to C. trachomatis. Two women had IgM antibodies. Two other women, who harbored Neisseria gonorrhoeae in the cervix, had antibodies to gonococcal pili; one had a significant decrease in titer. This latter patient was one of the patients with a stationary titer of antibodies to C trachomatis. One patient had a stationary titer of antibodies to Mycoplasma hominis. In general, chlamydial salpingitis seems to have relatively benign symptoms. Neither the failure to isolate C. trachomatis from the cervix nor a stationary titer of antibodies to the organism precludes a chlamydial etiology of acute salpingitis.

Sensitive solid-phase radioimmunoassay for detection of human immunoglobulin G antibodies to varicella-zoster virus

A sensitive solid-phase radioimmunoassay for detection of antibodies to varicella-zoster virus (VZV) is described. The antigen consisted of a sonically disrupted extract of VZV-infected human embryo cells. 125I-labeled rabbit anti-human immunoglobulin G (IgG) specific for the Fc portion of human IgG was used to detect human IgG bound to viral antigen. With this technique, 193 human sera were evaluated for their IgG antibody titer against ZVZ. Subjects included 62 healthy adults, 33 young children (12 healthy), and 49 patients. Titers obtained by the radioimmunoassay were compared with those obtained by indirect fluoresence antibody staining of membrane antigen. The radioimmunoassay technique described gave titers approximately 5 X 10(4) times higher than those shown by indirect fluorescence. It can be used for routine diagnosis, but is especially suited to determining immune status to VZV, as defined by presence or absence of antibodies to the virus; for epidemiological studies; or for determining patients at risk who are exposed to the virus. No heterotypic titer rises to VZV were observed in sera with fourfold or greater rises to Epstein-Barr virus or cytomegalovirus. Sera of eight subjects with fourfold or greater titer rises to herpes simplex virus reacted in various ways: in six cases no significant change occurred in titer to VZV; one had a significant decrease in titer by the radioimmunoassay; and one had a significant increase. Possible reasons for these titer changes are discussed.

Effect of cytosine arabinoside on herpes virus infection in renal allograft recipients

Cytosine arabinoside (Ara-C) was used for treatment of severe symptomatic cytomegalovirus (CMV)-herpes infections that were seen in nineteen of 174 renal allograft recipients. Ara-C was administered by continuous intravenous infusion at a mean dose of 35 mg/m 2 daily for three to four days. Side effects were few and minor in nature. All cases of herpes simplex and herpes zoster, which usually have a prolonged and sometimes unfavorable course in immunosuppressed patients, cleared promptly with no recurrence. All nine patients, except one who had CMV infection with the symptom complex of fever and retinitis or pneumonitis, responded satisfactorily. In the three patients in whom the CMV titers were available, there was a significant decrease in titer within two weeks after treatment.

Preservation of sera by means of paper discs

Human sera were absorbed into electrophoretic paper (Whatman) discs. After drying and storage either at +4 °C or at room temperature (18 °C) for four, seven and 14 weeks, the sera were eluted with distilled water and the diphtheria antitoxin contents were determined. Comparison with the titration of sera stored in the conventional way showed that there had been a significant decrease in titre in the case of discs dried and stored at room temperature. Alternatively, when stored at +4 °C a significant decrease in titre did not take place. This method of storage can thus be used where deep freezing of serum is not available. The storage and the transportation of sera treated in this way is very convenient.

Indirect fluorescent-antibody method for the identification of Corynebacterium vaginale.

The indirect fluorescent-antibody technique was employed in an attempt to develop a rapid method of identification of Corynebacterium vaginale. Six reference strains and ten clinical isolates selected on the basis of morphology and conventional biochemical tests were compared. Antisera were prepared in rabbits against the six reference strains. The most satisfactory antiserum was that prepared using strain 14018 grown diphasically (14018 Di) as the antigen. Certain of the antisera did exhibit a cross-reacting titer when reacted against Corynebacterium diptheriae, Corynebacterium xerosis, or Lactobacillus acidophilus. However, antisera adsorbed with these bacteria did not exhibit a significant decrease in titer when reacted against the homologous strain. Various other species of Corynebacterium as well as species of Nocardia, Actinomyces, Hemophilus, and Streptococcus did not fluoresce with the antisera. A specific antiserum was prepared by adsorbing anti-14018 Di with L. acidophilus. The adsorption removed the cross-reacting antibody but did not affect the staining reaction with C. vaginale strains. All reference strains and clinical isolates characterized as C. vaginale gave a definite positive reaction with the adsorbed anti-14018 Di. The specificity of the reactions was assessed by adsorbing the antiserum with the homologous strain. The data suggest that the indirect staining method will be of value in the rapid presumptive identification of C. vaginale.

Host defense mechanisms against herpes simplex virus. II. Protection conferred by sensitized spleen cells.

The role of cell-mediated protection against infection with herpes simplex virus was studied by adoptive immunity. Sensitized spleen cells, obtained from syngeneic mice immunized with herpes simplex virus, protected recipient mice against lethal challenge with herpes simplex virus. Survival was significantly greater in challenged mice that had received washed spleen cells from donor animals immunized with herpes simplex than from control donors. This increase in survival after challenge was associated with a significant decrease in titers of virus in the brains of mice that had received specifically sensitized cells. The decrease in viral titers was evident during the period after challenge when titers of virus peak and most deaths occur. There was no obvious association between increased survival and the levels of antibody and interferon in serum of the challenged animals, but these serum factors still must be considered as possible mediators of the protection conferred by sensitized spleen cells.

Indirect Fluorescent-Antibody Method for the Identification of Corynebacterium vaginale

The indirect fluorescent-antibody technique was employed in an attempt to develop a rapid method of identification of Corynebacterium vaginale. Six reference strains and ten clinical isolates selected on the basis of morphology and conventional biochemical tests were compared. Antisera were prepared in rabbits against the six reference strains. The most satisfactory antiserum was that prepared using strain 14018 grown diphasically (14018 Di) as the antigen. Certain of the antisera did exhibit a cross-reacting titer when reacted against Corynebacterium diptheriae, Corynebacterium xerosis, or Lactobacillus acidophilus. However, antisera adsorbed with these bacteria did not exhibit a significant decrease in titer when reacted against the homologous strain. Various other species of Corynebacterium as well as species of Nocardia, Actinomyces, Hemophilus, and Streptococcus did not fluoresce with the antisera. A specific antiserum was prepared by adsorbing anti-14018 Di with L. acidophilus. The adsorption removed the cross-reacting antibody but did not affect the staining reaction with C. vaginale strains. All reference strains and clinical isolates characterized as C. vaginale gave a definite positive reaction with the adsorbed anti-14018 Di. The specificity of the reactions was assessed by adsorbing the antiserum with the homologous strain. The data suggest that the indirect staining method will be of value in the rapid presumptive identification of C. vaginale.

Effects of injections of allergen extracts on antigenic release of histamine from leucocytes, skin tests and bronchial challenge in allergic children.

SummaryLeucocyte sensitivity to antigenic release of histamine was determined in allergic children receiving injections of allergen extracts in order to ascertain the frequency of development of complete loss of sensitivity (unresponsiveness). Leucocyte unresponsiveness did not occur in any of eight allergic children given large doses of allergen extracts by an intensive regimen of injections. In only two of twenty‐three children who had received injections of allergen extracts by a customary dosage regimen, were the leucocytes found to be unresponsive to antigenic histamine release. These findings confirm our earlier reports.The incidence of complete loss of leucocyte sensitivity during injection therapy in our studies is lower than reported by others. This is attributed to our employment of a more nearly optimal in vitro system for measurement of antigenic histamine release from leucocytes, thus avoiding the false impression of leucocyte unresponsiveness which can result from use of a less sensitive procedure.Other findings in the present investigation were: (I) concordant fluctuations in leucocyte sensitivity to two unrelated allergens during injections of one of the allergens, indicating non‐specific changes in sensitivity; (2) skin sensitivity and bronchial reactivity were not reduced even with marked decrease in peripheral leucocyte sensitivity; (3) significant decrease in titre of serum complement, as occurs in presence of antigen‐antibody complex reactions.

Biosynthesis of arginine in L cells infected with chlamydiae.

Three members of the genus Chlamydia were examined for their ability to synthesize arginine, an ability their L cell (mouse fibroblasts) hosts lacked. C. psittaci (strain 6BC) multiplied in arginine-free medium 199 without significant decrease in titer and incroporated (14)C-glutamate and (14)C-ornithine into the arginine fraction of its protein. In arginine-free media, C. trachomatis (strain mouse pneumonitis) and C. psittaci (strain meningopneumonitis) grew to only 1 to 10% of the titer obtained in arginine-containing media. The decreased ability of these two strains to multiply in arginine-free media was paralleled by a decreased ability of infected host cells to incorporate (14)C-glutamate into protein arginine. These results suggest that chlamydiae either synthesize arginine themselves, or, in some unknown manner, cause their host cells to do so.