Evaluation of a new third generation anti-HIV-1/anti-HIV-2 assay with increased sensitivity for HIV-1 group O.

Although the HIV-1 group O virus found in two persons of Cameroonian origin has been described in 1990 (De Leys et al., 1990), sera from group O infected individuals became available only recently. Several studies showed that some of the anti-HIV-1/HIV-2 screening tests failed to detect all of these samples (Loussert-Ajaka et al., 1994; Simon et al., 1994; Schable et al., 1994; Gürtler et al., 1995). In the current version of an anti-HIV-1/anti-HIV-2 screening assay, namely the Vironostika HIV Uni-Form II, an HIV-O specific peptide was introduced in order to improve HIV-1 group O reactivity. The peptide was derived from the immunodominant region of HIV-1 group O gp41 strain ANT70. All 30 anti-HIV-1 group O sera were detected by the so-called plus O assay, while 29 samples of this panel were positive the current assay. The sensitivity of the plus O assay for anti-HIV-1 and anti-HIV-2 positive samples is identical to that of the reference test without HIV-1 group O peptide. The clinical specificity of the HIV Uni-Form II plus O assay is improved to > or = 99.92% by an adjustment of the coat concentration of HIV-1 p24 (to avoid false positive p24 only reactions) without affecting sensitivity of the assay. The specific reaction of an HIV-1 group O specific rabbit serum for quality control purposes is presented.

[Degradation of cereal straw with lye]. / Ontsluiting van graanstro met loog.

Straw is a plentiful agricultural waste product. It cannot be used as the sole feed for ruminants and it cannot even serve to satisfy maintenance requirements. The rumen microbes are not capable of breaking down the cell walls in cereal straw rapidly enough or to a sufficient extent. To improve the utilization of straw, efforts were made to treat this material by physical, chemical and biological methods. Some of these procedures will only improve the intake of straw by the animal, whereas the primary object continues to be the improvement of digestibility. Alkali treatment of straw is the most suitable method for this purpose. The mode of action of alkali on the cell walls of straw is described in the present paper.

Properties of turnip yellow mosaic virus in cesium chloride solutions: the formation of high-density components.

The bottom component B1a of TYMV with a buoyant density of 1.42-1.43 g/ml, is converted to a more dense particle B2a following CsCI density gradient centrifugation. This conversion is complete after a prior incubation of the virus in the CsCl solution at elevated temperatures. It is shown that the formation of B28 is accompanied with a loss from the virion of polyvalent cations like spermidine and Mg2+. The exchange of the latter ions for Cs ions is responsible for the occurrence of the higher-density particles. The more dense component B2a can be converted back to B,; like particles upon incubation in the presence of 0.1 M M9Cl2. If TYMV or component B1a is centrifuged in the presence of Mg2+, the conversion into B2a is prevented. The latter phenomenon allowed the isolation and characterization of the minor components B1b and B1c, previously postulated (Mellema et al. (1979), Virology 96, 38-46). The phenomenon of conversion appeared to be restricted to the components of the B series of TYMV; indicating that the class of light minor components does not contain artefacts of the CsCl gradient centrifugation. The formation of B2a is accompanied by degradation of RNA, which might be due to some conformational change in the virion, rendering the RNA vulnerable to RNases.

Synthesis, resolution and charge-donor properties of six tryptophan analogues.

In order to investigate the special function of tryptophan in peptide hormones, six tryptophan analogues have been synthesized, in which structural resemblance has been grossly retained and potentially essential properties have only partially been varied. The L-enantiomers have been isolated after enzymatic digestion of racemic dipeptide derivatives, and charge-transfer properties of the compounds have been studied.