Cloning and characterization of human immunodeficiency virus type 1 variants diminished in the ability to induce syncytium-independent cytolysis.

The phenomenon of interference was exploited to isolate low-abundance noncytopathic human immunodeficiency virus type 1 (HIV-1) variants from a primary HIV-1 isolate from an asymptomatic HIV-1-seropositive hemophiliac. Successive rounds of virus infection of a cytolysis-susceptible CD4+ cell line and isolation of surviving cells resulted in selective amplification of an HIV-1 variant reduced in the ability to induce cytolysis. The presence of a PvuII polymorphism facilitated subsequent amplification and cloning of cytopathic and noncytopathic HIV-1 variants from the primary isolate. Cloned virus stocks from cytopathic and noncytopathic variants exhibited similar replication kinetics, infectivity, and syncytium induction in susceptible host cells. The noncytopathic HIV-1 variant was unable, however, to induce single-cell killing in susceptible host cells. Construction of viral hybrids in which regions of cytopathic and noncytopathic variants were exchanged indicated that determinants for the noncytopathic phenotype map to the envelope glycoprotein. Sequence analysis of the envelope coding regions indicated the absence of two highly conserved N-linked glycosylation sites in the noncytopathic HIV-1 variant, which accompanied differences in processing of precursor gp160 envelope glycoprotein. These results demonstrate that determinants for syncytium-independent single-cell killing are located within the envelope glycoprotein and suggest that single-cell killing is profoundly influenced by alterations in envelope sequence which affect posttranslational processing of HIV-1 envelope glycoprotein within the infected cell.

HIV-1 replication is controlled at the level of T cell activation and proviral integration.

During progression of the Acquired Immune Deficiency Syndrome (AIDS), the human immunodeficiency virus type 1 (HIV-1) is harbored in CD4+ T cells, which act as the primary reservoir for the virus. In vitro, HIV-1 requires activated T cells for a productive infection; however, in vivo, the number of circulating T cells in the activated state that are potential targets for HIV-1 infection is low. We have investigated the ability of HIV-1 to infect resting T cells, and the consequences of such an infection. T cell activation was not required for HIV-1 infection; however, viral DNA was unable to integrate in resting T cells and was maintained extrachromosomally. Subsequent T cell activation allowed integration of extrachromosomal forms and led to a productive viral life cycle. Extrachromosomal forms of viral DNA were found to persist for several weeks after infection of resting T cells and, following T cell activation, these forms maintained their ability to integrate and act as a template for infectious virus. Several lines of evidence, including temporal analysis of HIV-1 replication and analysis of an HIV-1 integrase deletion mutant, indicated that extra-chromosomal HIV-1 DNA genomes were transcriptionally active. These results are compatible with a model whereby HIV-1 can persist in a non-productive extra-chromosomal state in resting T cells until subsequent antigen-induced or mitogen-induced T cell activation, virus integration and release. Thus agents that induce T cell activation may control the rate of HIV-1 replication and spread during AIDS progression.

Integration is not necessary for expression of human immunodeficiency virus type 1 protein products.

A common feature in the life cycle of cytocidal retroviruses, including human immunodeficiency virus type 1 (HIV-1), is the accumulation of large amounts of unintegrated viral DNA. As yet, the role of unintegrated viral DNA in the cytopathogenesis of cytocidal retrovirus infections remains unresolved. HIV-1 mutants which were deleted in the integrase/endonuclease gene and which were unable to establish an integrated form of the virus were constructed. Despite an inability to integrate, these mutants were fully competent templates for HIV-1 core and envelope antigen production. HIV-1 antigen could be detected in the supernatants of lymphocyte cultures infected with HIV-1 integrase mutants. However, an inability to rescue infectious virus from these cultures indicated that HIV-1 integration was required for the production of infectious HIV-1. On the basis of the ability of unintegrated HIV-1 DNA to serve as a template for HIV-1 antigen production, it is plausible that unintegrated viral DNA can contribute to the HIV-1 antigen pool during HIV-1 replication.

A case of sudden retinal artery occlusion and blindness in pregnancy.

Central retinal artery occlusion is generally a disease of old age associated with loss of vision in one eye. In older patients, it is usually secondary to emboli from atherosclerotic plaques; in younger patients valvular heart disease is a common precursor. Several other conditions have been associated with central retinal artery occlusion, but to our knowledge, there have been no previously reported cases with pregnancy as the sole associated factor. Such a case is presented.

Massive transfusion without major complications after trauma.

A case of massive degloving injury of the trunk, with open pelvic fracture, and evisceration of abdominal contents from blunt trauma is presented. The most significant aspect of this case was the transfusion of 173 units of packed cells and 176 units of fresh frozen plasma in the first thirty hours. The patient ultimately recovered and returned to work.

Prolonged tracheal intubation in the trauma patient.

Over a 15-month period, 74 trauma patients who were expected to require extended intubation were studied prospectively to evaluate the appropriateness of tracheostomy. Patients were randomized to receive either early (34) or late (40) tracheostomies. The patients also were grouped to determine the difference of early versus late tracheostomy on the development of laryngotracheal pathology and respiratory infections; length of intubation and type of patient injury were studied as possible differential factors. Fifteen per cent (11/74) of the patients developed major laryngotracheal pathology as identified by endoscopy, and respiratory infections developed in 54% (40/74), but there was no significant difference in the complication incidence between the early and late tracheostomy groups. Significantly more complications occurred in rigid-posture, head-injured patients than in any other trauma grouping, but there was no significant difference in the complication incidence between the two tracheostomy groups within that classification. We conclude that patients can undergo translaryngeal intubation for up to 2 weeks without significantly increasing complications relative to transtracheal intubation.

Acute renal failure associated with the thrombocytopenia of septicemia.

Gram-negative sepsis is a recognized cause of thrombocytopenia and has recently been associated with acute renal failure from acute glomerulonephritis. We report here a patient in which the development of and treatment for trauma, gram-negative sepsis, was followed one day later by rapidly rising WBC (20,000-65,000), creatinine, BUN, and thrombocytopenia (300,000-25,000). Peak creatinine (6.5 mg%) and BUN (160 mg%) levels occurred on the third day of septicemia, when dialysis was begun. During the profound thrombocytopenia (less than 20,000 on days three through five of the septicemia) platelet transfusions did not raise the platelet count. The platelets returned to above 100,000 by day seven of the septicemia and the WBC was under 30,000 by this time. We propose that septicemia caused by E. coli (and staph) was responsible for the concomitant appearance of both thrombocytopenia and acute renal failure in a 20-year-old man.