Reverse transcriptase and corresponding activity-blocking antibody for monitoring SIVsm infection in macaques.

A nonradioactive reverse transcriptase (RT) assay was used to measure RT activity in serum during the viremia peak associated with primary infection and for measuring the generation and maintenance of RT activity-blocking antibody (RTb-ab) titers during and after seroconversion in SIV-infected macaques. The RT assay was compared to an antigen capture immunoassay designed for HIV-2/SIVsm and was found to be approximately 40 times more sensitive in detecting SIVsm in serum from infected macaques. The RT assay detected RT activity in serum corresponding to levels from 3 pg/ml.

Interaction of fluid phase C1/C1q and macrophage membrane-associated C1q with gram-negative bacteria.

Many gram-negative bacteria are killed after treatment with normal non-immune sera and directly bind and activate C1 in the absence of antibodies. For the immediate killing of such serum-sensitive bacteria, like R-forms of Salmonella strains, all serum complement components are essential. When purified serum C1 to C9 are used, further activation of the cascade requires an additional serum factor.

Patients with CLL and hypocomplementaemia have an impaired serum bactericidal activity against the Salmonella minnesota Re mutant.

The bactericidal effect of 25 serum samples from 23 patients with chronic lymphocytic leukaemia (CLL) against the Salmonella minnesota S form and Re mutant has been studied. No killing of the S form was observed in any of the sera tested, whereas a normal bactericidal effect was found against the Re mutant (group 1) in 17/25 sera of CLL patients. By contrast, in 8 serum samples from 6 CLL patients no killing or a markedly delayed killing of the Re strain was observed (group 2).

Antibody-independent killing of gram-negative bacteria via the classical pathway of complement.

The experiments in this paper provided evidence that, besides lipopolysaccharides (LPS), porins of gram-negative bacteria bind to C1q and C1. From these experiments, we concluded that the association of LPS and porins (outer membrane proteins, OMP) may potentiate the C1q and C1 binding in the absence of specific antibodies. This antibody independent binding of C1 to LPS and porins is a prerequisite for the activation of the classical pathway of complement leading to the killing of serum-sensitive bacteria.