Comparison of two antigen detection techniques in a primate model of Haemophilus influenzae type b infection

Rapid diagnosis of Haemophilus influenzae type b meningitis is possible using immunological tests for capsular antigen (polyribophosphate, PRP), such as countercurrent immunoelectrophoresis (CIE) and latex particle agglutination (LPA). The authors compared 2 tests in monkeys with evolving, serially quantitated H. influenzae type b bacteremia (n = 23) and meningitis (n = 21). In vitro, the LPA test was sensitive to 0.5 ng of PRP/ml of saline, and the CIE test was sensitive to 1.0 ng/ml; in serum, however, CIE detected 5.0 ng of PRP/ml, whereas the sensitivity of LPA was unchanged. LPA detected PRP earlier in the course of bacteremia (mean, 12 hr after onset; range, 4 to 36 hr) than did CIE (mean, 45 hr; range, 4 to 168 hr) (P < 0.01). A positive LPA test required ≥ 100 bacteria per ml of blood, whereas CIE required ≥ 1,000/ml. PRP accumulated with continuing blood stream infection, aiding detection of low-grade bacteremia. LPA detected antigen in cerebrospinal fluid (CSF) earlier in the course of meningitis and at a lower bacteria density than did CIE. Both methods detected antigen reliably with ≥ 1,000 bacteria per ml of CSF. A close correlation existed between CSF concentrations of capsular antigen and bacteria (r = 0.90, P < 0.001). The authors conclude that the LPA method permits earlier diagnosis of H. influenzae type b infection in part because of its greater sensitivity

Comparison of two antigen detection techniques in a primate model of Haemophilus influenzae type b infection

Rapid diagnosis of Haemophilus influenzae type b meningitis is possible using immunological tests for capsular antigen (polyribophosphate, PRP), such as countercurrent immunoelectrophoresis (CIE) and latex particle agglutination (LPA). The authors compared 2 tests in monkeys with evolving, serially quantitated H. influenzae type b bacteremia (n = 23) and meningitis (n = 21). In vitro, the LPA test was sensitive to 0.5 ng of PRP/ml of saline, and the CIE test was sensitive to 1.0 ng/ml; in serum, however, CIE detected 5.0 ng of PRP/ml, whereas the sensitivity of LPA was unchanged. LPA detected PRP earlier in the course of bacteremia (mean, 12 hr after onset; range, 4 to 36 hr) than did CIE (mean, 45 hr; range, 4 to 168 hr) (P < 0.01). A positive LPA test required ≥ 100 bacteria per ml of blood, whereas CIE required ≥ 1,000/ml. PRP accumulated with continuing blood stream infection, aiding detection of low-grade bacteremia. LPA detected antigen in cerebrospinal fluid (CSF) earlier in the course of meningitis and at a lower bacteria density than did CIE. Both methods detected antigen reliably with ≥ 1,000 bacteria per ml of CSF. A close correlation existed between CSF concentrations of capsular antigen and bacteria (r = 0.90, P < 0.001). The authors conclude that the LPA method permits earlier diagnosis of H. influenzae type b infection in part because of its greater sensitivity

Ig allotype-linked regulation of class and subclass composition of natural antibodies to group A streptococcal carbohydrate.

To determine the importance of genes located in or near the Ig constant regions in regulating the human antibody response, we correlated Ig allotypic markers with total Ig concentrations and natural antibody concentrations to the streptococcal group A carbohydrate (A-CHO) in 193 healthy adult blood donors. The major correlations between Ig allotypes and total Ig and specific antibody concentrations were observed with the Gm(f;n;b) haplotype. When compared with Gm(f;n;b) negative individuals, Gm(f;n;b) positives had significantly higher concentrations of total IgG2 (p less than 0.001) and IgG2 anti A-CHO (p less than 0.05), lower concentrations of total IgG1 (p less than 0.001) and IgG1 anti A-CHO (p less than 0.001), and lower concentrations of total IgM (p less than 0.001) and IgM anti A-CHO (p less than 0.05). We conclude that individuals with the Gm(f;n;b) haplotype respond preferentially with IgG2 rather than IgG1 subclass antibodies. This increased capacity to respond with IgG2 antibodies may be reflected in the magnitude of the total antibody response when the IgG2 subclass comprises a major proportion of the response, as occurs in the adult response to many polysaccharide Ag