[Acute upper limb embolism in a severely burned patient]

Thrombosis and pulmonary embolisms are the most common complications in the hospital. The need for anticoagulation during hospital stay is obligatory. Arterial embolisms are rare. They often take place in patients with a pre-existing peripheral artery occlusive disease or in patients with atrial fibrillation. The most common complications in burn patients are wound infection, pneumonia, catheter-associated infections and paralytic ileus. There are almost no data available regarding arterial embolism in burn patients. Therefore we would like to present the case of a 60-year-old woman who was injured by a fire at home and was transported to our special burn unit. She sustained partial thickness burns of both legs and buttocks. The TBSA was 15%. During the first days of clinical stay the patient suffered from a pain induced movement reduction of the left hand. There were no peripheral pulses palpable or by pulsed-wave Doppler detectable. An urgent selected angiography of the left arm was performed and a arterial embolism of the proximal part of the a. brachialis was detected. The patient was operated immediately. After debridement and split-skin graft of the burn wounds the patient was taken to rehabiliation after 35 days.

Characterization of chemokine receptor utilization of viruses in the latent reservoir for human immunodeficiency virus type 1

Latently infected resting CD4(+) T cells provide a long-term reservoir for human immunodeficiency virus type 1 (HIV-1) and are likely to represent the major barrier to virus eradication in patients on combination antiretroviral therapy. The mechanisms by which viruses enter the latent reservoir and the nature of the chemokine receptors involved have not been determined. To evaluate the phenotype of the virus in this compartment with respect to chemokine receptor utilization, full-length HIV-1 env genes were cloned from latently infected cells and assayed functionally. We demonstrate that the majority of the viruses in the latent reservoir utilize CCR5 during entry, although utilization of several other receptors, including CXCR4, was observed. No alternative coreceptors were shown to be involved in a systematic fashion. Although R5 viruses are present in the latent reservoir, CCR5 was not expressed at high levels on resting CD4(+) T cells. To understand the mechanism by which R5 viruses enter latent reservoir, the ability of an R5 virus, HIV-1 Ba-L, to infect highly purified resting CD4(+) T lymphocytes from uninfected donors was evaluated. Entry of Ba-L could be observed when virus was applied at a multiplicity approaching 1. However, infection was limited to a subset of cells expressing low levels of CCR5 and markers of immunologic memory. Naive cells could not be infected by an R5 virus even when challenged with a large inoculum. Direct cell fractionation studies showed that latent virus is present predominantly in resting memory cells but also at lower levels in resting naive cells. Taken together, these findings provide support for the hypothesis that the direct infection of naive T cells is not the major mechanism by which the latent infection of resting T cells is established.

Reservoirs for HIV-1: mechanisms for viral persistence in the presence of antiviral immune responses and antiretroviral therapy

The success of combination antiretroviral therapy for HIV-1 infection has generated interest in mechanisms by which the virus can persist in the body despite the presence of drugs that effectively inhibit key steps in the virus life cycle. It is becoming clear that viral reservoirs established early in the infection not only prevent sterilizing immunity but also represent a major obstacle to curing the infection with the potent antiretroviral drugs currently in use. Mechanisms of viral persistence are best considered in the context of the dynamics of viral replication in vivo. Virus production in infected individuals is largely the result of a dynamic process involving continuous rounds of de novo infection of and replication in activated CD4(+) T cells with rapid turnover of both free virus and virus-producing cells. This process is largely, but not completely, interrupted by effective antiretroviral therapy. After a few months of therapy, plasma virus levels become undetectable in many patients. Analysis of viral decay rates initially suggested that eradication of the infection might be possible. However, there are several potential cellular and anatomical reservoirs for HIV-1 that may contribute to long-term persistence of HIV-1. These include infected cell in the central nervous system and the male urogenital tract. However, the most worrisome reservoir consists of latently infected resting memory CD4(+) T cells carrying integrated HIV-1 DNA. Definitive demonstration of the presence of this form of latency required development of methods for isolating extremely pure populations of resting CD4(+) T cells and for demonstrating that a small fraction of these cells contain integrated HIV-1 DNA that is competent for replication if the cells undergo antigen-driven activation. Most of the latent virus in resting CD4(+) T cells is found in cells of the memory phenotype. The half-life of this latent reservoir is extremely long (44 months). At this rate, eradication of this reservoir would require over 60 years of treatment. Thus, latently infected resting CD4(+) T cells provide a mechanism for life-long persistence of replication-competent forms of HIV-1, rendering unrealistic hopes of virus eradication with current antiretroviral regimens. The extraordinary stability of the reservoir may reflect gradual reseeding by a very low level of ongoing viral replication and/or mechanisms that contribute to the intrinsic stability of the memory T cell compartment. Given the substantial long-term toxicities of current combination therapy regimens, novel approaches to eradicating this latent reservoir are urgently needed.

A stable latent reservoir for HIV-1 in resting CD4(+) T lymphocytes in infected children

HIV-1 persists in a latent state in resting CD4(+) T lymphocytes of infected adults despite prolonged highly active antiretroviral therapy (HAART). To determine whether a latent reservoir for HIV-1 exists in infected children, we performed a quantitative viral culture assay on highly purified resting CD4(+) T cells from 21 children with perinatally acquired infection. Replication-competent HIV-1 was recovered from all 18 children from whom sufficient cells were obtained. The frequency of latently infected resting CD4(+) T cells directly correlated with plasma virus levels, suggesting that in children with ongoing viral replication, most latently infected cells are in the labile preintegration state of latency. However, in each of 7 children who had suppression of viral replication to undetectable levels for 1-3 years on HAART, latent replication-competent HIV-1 persisted with little decay, owing to a stable reservoir of infected cells in the postintegration stage of latency. Drug-resistance mutations generated by previous nonsuppressive regimens persisted in this compartment despite more than 1 year of fully suppressive HAART, rendering untenable the idea of recycling drugs that were part of failed regimens. Thus the latent reservoir for HIV-1 in resting CD4(+) T cells will be a major obstacle to HIV-1 eradication in children.

Latent infection of CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy

Combination therapy for HIV-1 infection can reduce plasma virus to undetectable levels, indicating that prolonged treatment might eradicate the infection. However, HIV-1 can persist in a latent form in resting CD4+ T cells. We measured the decay rate of this latent reservoir in 34 treated adults whose plasma virus levels were undetectable. The mean half-life of the latent reservoir was very long (43.9 months). If the latent reservoir consists of only 1 x 10(5) cells, eradication could take as long as 60 years. Thus, latent infection of resting CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective anti-retroviral therapy.

Identification of a reservoir for HIV-1 in patients on highly active antiretroviral therapy

The hypothesis that quiescent CD4+ T lymphocytes carrying proviral DNA provide a reservoir for human immunodeficiency virus-type 1 (HIV-1) in patients on highly active antiretroviral therapy (HAART) was examined. In a study of 22 patients successfully treated with HAART for up to 30 months, replication-competent virus was routinely recovered from resting CD4+ T lymphocytes. The frequency of resting CD4+ T cells harboring latent HIV-1 was low, 0.2 to 16.4 per 10(6) cells, and, in cross-sectional analysis, did not decrease with increasing time on therapy. The recovered viruses generally did not show mutations associated with resistance to the relevant antiretroviral drugs. This reservoir of nonevolving latent virus in resting CD4+ T cells should be considered in deciding whether to terminate treatment in patients who respond to HAART.

Positive and negative regulation of gene expression in eukaryotic cells with an inducible transcriptional regulator

To facilitate the understanding of the complex process of target gene expression and its control, we report a modified inducible system for activation or repression of target gene expression in response to an exogenously administered compound. The main component of this inducible system is a chimeric transcriptional activator (GLVP) consisting of an N-terminal VP16 transcriptional activation domain fused to a yeast GAL4 DNA binding domain and a mutated human progesterone receptor (hPR) ligand binding domain (LBD). This chimeric regulator binds to a target gene containing the 17-mer GAL4 upstream activation sequence (UAS) in the presence of anti-progesterone, RU486. We showed that the combination of two different types of domains (VP16 and poly-glutamine stretch) into one chimeric molecule could result in a further increase in transcriptional activation potency. Through mutational analysis, we modified the original GLVP and generated a more potent version of the RU486 inducible regulator GL914 VPc with a 19 amino acid deletion of the hPR-LBD (delta C19) and a C-terminally located VP16 activation domain. More importantly, this new chimeric regulator can effectively activate target gene expression at a much lower concentration of RU486 (0.01 nM). The concept of RU486 regulatable gene expression is not limited to gene activation. By replacing the VP16 activation domain with a KRAB transcriptional repression domain, we are able to achieve inducible repression of target gene expression. We also present evidence that individual functional domains within a chimeric protein could modulate each other's function depending on their relative positions within the molecule. Using this potent regulator, we demonstrate that inducible nerve growth factor (NGF) secretion into conditioned media can elicit neurite outgrowth in co-cultured PC12 cells. This new versatile inducible system can potentially be used to control target gene expression in a mammalian system in vivo.

Acceleration and deceleration of sexual maturation by social cues in a tropical rodent Zygodontomys brevicauda

The effects of social cues from adult conspecifics on the rate of sexual maturity were studied in a tropical rodent, the cane mouse (Zygodontomys brevicauda), in the laboratory. Several aspects of the biology of this species have suggested that it might be atypical in that young females may not accelerate or decelerate their rate of reproductive development in response to social cues. This hypothesis was tested by housing 16-day-old females with an adult male, an adult female, or alone, and reproductive development was assessed periodically, beginning when the mice were 20 days old. Young females paired with males underwent more uterine growth and matured markedly earlier than did isolated controls. Young females paired with adult females exhibited less uterine growth than did isolated controls. Thus, social cues both accelerate and decelerate reproductive development in females of this species, and the hypothesis that social cues have no effect on reproductive development in young females was rejected. The evolutionary conditions that favour unresponsiveness of young females to social cues appear to be restrictive, and may be rare in mammals.