Effect of zidovudine on serum human immunodeficiency virus core antigen levels. Results from a placebo-controlled trial.

We assessed the effect of antiviral therapy on serum human immunodeficiency virus core antigen (HIV-Ag) levels in patients enrolled in the phase II trial on zidovudine for acquired immunodeficiency syndrome (AIDS) and AIDS-related complex. Human immunodeficiency virus core antigen was detected in 45% of subjects at entry (59% with AIDS and 37% of patients with AIDS-related complex). Median HIV-Ag levels in zidovudine-treated subjects fell from 111 pg/mL at entry to 46 pg/mL at four weeks, while levels in placebo recipients did not change significantly. Decline in HIV-Ag in zidovudine recipients was sustained through 16 weeks of treatment and was significantly different from the placebo group. Anti-p24 antibody levels did not change in either group. We conclude that in patients with HIV-antigenemia changes in HIV-Ag level are an important marker of anti-retroviral activity.

HIV-1 inhibition by azidothymidine in a concurrently randomized placebo-controlled trail.

Two independent measures of human immunodeficiency virus type 1 (HIV-1) infection, virus isolation, and serum levels of p24 antigen were evaluated in a double-blind randomized clinical trial of the safety and efficacy of a nucleoside analogue, 3'-azido-3'-deoxythymidine (AZT) versus placebo in a single center. Pretreatment studies from 38 AIDS and AIDS-related complex (ARC) patients were comparably positive for virus isolation from their lymphocytes; all patients were qualitatively virus positive. Before AZT treatment, there was significantly decreased virus recovery in patients with higher numbers of CD4-positive lymphocytes. Within 1 month of AZT therapy, the time in culture required to register virus positivity was increased markedly in the AZT-treated group, and over the following several months progressive diminution in virus recovery was noted. Similar changes were not seen in patients concurrently receiving placebo treatment. Before treatment, 16 of 20 and 12 of 16 patients in the AZT and placebo groups, respectively, were p24 antigen positive. Marked reduction in serum p24 levels were noted in 11 of 16 (69%) of the p24 antigen-positive AZT-treated patients compared to 3 of 12 (25%) of the p24 antigen-positive placebo-treated patients (p = 0.02). There was a marked virologic response in 14 of 20 (70%) of the AZT-treated patients compared to 4 of 18 (22%) placebo-treated patients (p = 0.004). A higher frequency of positive clinical and immunological effects also were noted in the AZT-treated patients relative to placebo-treated patients (p = 0.02 and p = 0.06, respectively).

Fluorescence photobleaching recovery measurement of protein absolute diffusion constants.

The technique of fluorescence photobleaching recovery [Axelrod et al., Biophys. J. 16 (1976) 1055] has been applied to the measurement of absolute diffusion constants of a number of fluoiescein isothiocyanate-labeled proteins. Measured diffusion constants agree to within +/- 7% of published values for the underivatized proteins. The method has sufficient sensitivity to reveal the concentration dependence at neutral pH of the diffusion constant of alpha-chymotrypsin. The rapidity with which the labelling and measurements can be performed and the small amount of material required suggest the technique may be useful in rapid characterization of small protein samples. Some developments in optical and electronic systems and in data processing for this technique are discussed.

Herpes simplex virus binding and entry modulate cell surface protein mobility.

Fluorescence photobleaching recovery measurements showed that herpes simplex virus type 1 attachment to target cells rapidly induced an anchorage modulation of cell surface protein mobility, an activity mediated by the cytoskeleton and associated with the multivalent attachment of other ligands (e.g., cells, lectins, or anti-immunoglobulin) to cell surfaces. The restriction in cell surface protein mobility was released concurrently with virus penetration. The effects of attachment and penetration on cell surface protein mobility and cytoskeletal function are some of the earliest cellular changes induced by herpes simplex virus infection.

Changes in lectin receptor lateral mobilities accompany lymphocyte stimulation.

Changes in lateral mobilities of rabbit lymphocyte membrane components in response to succinyl concanavalin A (S Con A) have been studied by fluorescence photobleaching recovery (FPR). During hrs 0 to 3 after exposure to S Con A, lectin receptor mobilities on both T and B cells fall about 2-fold. Reduced mobility of T cell lectin receptors persists until hr 18. From hr 18 to 24 rapid recovery of original mobility occurs if and only if lectin is present. In contrast, nonresponding B cells recover original receptor mobility gradually over hr 4 to 48. Metabolic inhibitors added at hr 3 restore original receptor mobilities, but cytoskeletal disruptors have this effect on T cells only. From hr 0 to 15, washing lectin from the cell surface is decreasingly effective in restoring T cell receptor mobility. After hr 15, mobility cannot be enhance by lectin removal. Parallel DNA synthesis studies show that, for T cell stimulation, lectin must be present on the cell surface during hr 0 to 3 and 18 to 24. These are the periods when FPR measurements show lectin receptor mobilities being restricted and released, respectively. Stimulation of B cells by anti-Ig shows several interesting features. First, stimulation by intact anti-Ig fails to reduce the mobilities of Con A receptors in a manner similar to that produced by S Con A. Second, S Con A does reduce mobility of surface Ig. Thus, Con A receptors would appear to exert a unique anchorage modulation of mobilities of other membrane molecules.