Interaction of capsulate Haemophilus influenzae with human airway mucosa in vitro.

Two pairs of isogenic capsulate and noncapsulate and one pair of capsulate fimbriate and nonfimbriate strains of Haemophilus influenzae type b were studied in an organ culture of human respiratory mucosa. Over 24 h, the numbers of recovered bacteria increased from the original inoculum size of 10(5) to 10(8) CFU/ml. Transmission electron microscopy and scanning electron microscopy showed that noncapsulate organisms caused significant epithelial damage, whereas capsulate strains did not. Association of noncapsulate bacteria with damaged epithelial cells was observed by 14 h of incubation. In contrast, capsulate organisms were associated with a dense, thick, gel-like matrix which was observed above the epithelial surface. These capsulate organisms were not seen to associate with the epithelial surface (by transmission electron microscopy), though they were occasionally seen adhering to cells by scanning electron microscopy. Fimbriate capsulate H. influenzae showed increased adherence to buccal cells compared with nonfimbriate capsulate organisms. There was also association of fimbriate capsulate bacteria with damaged organ culture epithelium in one of four experiments. It is concluded that both capsule and fimbriae affect the interaction of H. influenzae with human airway mucosa in vitro by influencing adherence to and damage of the epithelium.     

Clinical implications of positive tests for antibodies to human immunodeficiency virus type 1 in asymptomatic blood donors

Of 693,000 volunteer blood donors in Washington, D.C., who were screened for infection with human immunodeficiency virus type 1 (HIV-1) from July 1985 through December 1988, 284 tested positive on both enzyme immunoassay and Western blot assay. To determine the clinical importance of confirmed positive test results in asymptomatic blood donors, we followed 156 donors with positive Western blot assays and 80 donors with positive enzyme immunoassays but negative or indeterminate Western blots at 6-month intervals for a mean of 28 months. As compared with Western blot-negative persons, those with positive Western blots were significantly more likely to be black, male, and first-time donors and to have a history of venereal disease, generalized lymphadenopathy on examination, CD4-cell counts lower than 0.4 x 10(9) per liter, IgG levels higher than 18 g per liter, and antibody to hepatitis B core antigen on initial evaluation. In 17 (11 percent) of the Western blot-positive donors, the disease progressed to Class IV (symptomatic disease), according to the Centers for Disease Control system. CD4 counts below 0.2 x 10(9) per liter, IgA levels above 4 g per liter, abnormal proliferative responses to tetanus toxoid, and positive viral cultures were the strongest predictors of disease progression. Among the 80 donors with repeatedly reactive assay results but either negative or indeterminate Western blot assays, there was no evidence of HIV exposure in their histories, physical examinations, or laboratory evaluations, and manifestations of HIV infection developed in none of them. We conclude that a small number of persons with HIV infection continue to donate blood, despite attempts to exclude them, but that donors who test positive on enzyme immunoassay but persistently negative or indeterminate on Western blot assay probably do not represent a risk for the transmission of HIV.     

Chicken pox infection (varicella zoster virus) and acute monoarthritis: evidence against a direct viral mechanism.

A 9 year old boy developed acute monoarthritis of the left knee concurrent with the appearance of a varicella zoster virus (VZV) rash. Repeated VZV DNA hybridisation of the cells within the synovial fluid and synovial membrane failed to show any evidence of intracellular virus. Virus was isolated from synovial fluid 24 hours after the start of clinical infection but not later. These findings suggest that the mechanism of the arthritis is not due to viral replication inside the swollen joint.