Symptoms and risk factors for long COVID in non-hospitalized adults

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is associated with a range of persistent symptoms impacting everyday functioning, known as post-COVID-19 condition or long COVID. We undertook a retrospective matched cohort study using a UK-based primary care database, Clinical Practice Research Datalink Aurum, to determine symptoms that are associated with confirmed SARS-CoV-2 infection beyond 12 weeks in non-hospitalized adults and the risk factors associated with developing persistent symptoms. We selected 486,149 adults with confirmed SARS-CoV-2 infection and 1,944,580 propensity score-matched adults with no recorded evidence of SARS-CoV-2 infection. Outcomes included 115 individual symptoms, as well as long COVID, defined as a composite outcome of 33 symptoms by the World Health Organization clinical case definition. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHRs) for the outcomes. A total of 62 symptoms were significantly associated with SARS-CoV-2 infection after 12 weeks. The largest aHRs were for anosmia (aHR 6.49, 95% CI 5.02-8.39), hair loss (3.99, 3.63-4.39), sneezing (2.77, 1.40-5.50), ejaculation difficulty (2.63, 1.61-4.28) and reduced libido (2.36, 1.61-3.47). Among the cohort of patients infected with SARS-CoV-2, risk factors for long COVID included female sex, belonging to an ethnic minority, socioeconomic deprivation, smoking, obesity and a wide range of comorbidities. The risk of developing long COVID was also found to be increased along a gradient of decreasing age. SARS-CoV-2 infection is associated with a plethora of symptoms that are associated with a range of sociodemographic and clinical risk factors.

Cloning and expression of AP-2, a cell-type-specific transcription factor that activates inducible enhancer elements

Human AP-2 is a sequence-specific DNA-binding protein that interacts with inducible viral and cellular enhancer elements to stimulate transcription of selected genes. Here, we report the isolation and characterization of a human cDNA clone containing the entire protein-coding region of AP-2. The deduced primary amino acid sequence of AP-2 does not contain a domain resembling any previously identified DNA binding motif. However, an interesting feature of the AP-2 protein is a clustered arrangement of proline and glutamine residues that have been found recently within the activation domains of other transcription factors. Expression of the AP-2 clone in bacteria yields a protein that binds to DNA and activates transcription in vitro in a comparable manner to native human AP-2. Transfection of cDNA clones into Drosophila cells indicates that the AP-2 gene product can also activate gene expression in vivo in a DNA template-dependent manner. Expression of endogenous AP-2 is repressed in a hepatoma cell line and stimulated following retinoic-acid-induced differentiation of a human teratocarcinoma cell line. This indicates that AP-2 may be a transcription factor involved in the control of developmentally regulated gene expression.

Neural tube, skeletal and body wall defects in mice lacking transcription factor AP-2

The retinoic acid-inducible transcription factor AP-2 is expressed in epithelial and neural crest cell lineages during murine development. AP-2 can regulate neural and epithelial gene transcription, and is associated with overexpression of c-erbB-2 in human breast-cancer cell lines. To ascertain the importance of AP-2 for normal development, we have derived mice containing a homozygous disruption of the AP-2 gene. These AP-2-null mice have multiple congenital defects and die at birth. In particular, the AP-2 knockout mice exhibit anencephaly, craniofacial defects and thoraco-abdominoschisis. Skeletal defects occur in the head and trunk region, where many bones are deformed or absent. Analysis of these mice earlier in embryogenesis indicates a failure of cranial neural-tube closure and defects in cranial ganglia development. We have shown that AP-2 is a fundamental regulator of mammalian craniofacial development.

Analysis of the DNA-binding and activation properties of the human transcription factor AP-2

The mammalian transcription factor AP-2 is a sequence-specific DNA-binding protein expressed in neural crest lineages and regulated by retinoic acid. Here we report a structure/function analysis of the DNA-binding and transcription activation properties of the AP-2 protein. DNA contact studies indicate that AP-2 binds as a dimer to a palindromic recognition sequence. Furthermore, cross-linking and immunoprecipitation data illustrate that AP-2 exists as a dimer even in the absence of DNA. Examination of cDNA mutants reveals that the sequences responsible for DNA binding are located in the carboxy-terminal half of the protein. In addition, a domain mediating dimerization forms an integral component of this DNA-binding structure. Expression of AP-2 in mammalian cells demonstrates that transcriptional activation requires an additional amino-terminal domain that contains an unusually high concentration of proline residues. This proline-rich activation domain also functions when attached to the heterologous DNA-binding region of the GAL4 protein. This study reveals that although AP-2 shares an underlying modular organization with other transcription factors, the regions of AP-2 involved in transcriptional activation and DNA binding/dimerization have novel sequence characteristics.

A Phase II Study of Pembrolizumab in EGFR-Mutant, PD-L1+, Tyrosine Kinase Inhibitor Naïve Patients With Advanced NSCLC

BACKGROUND

Despite the significant antitumor activity of pembrolizumab in NSCLC, clinical benefit has been less frequently observed in patients whose tumors harbor EGFR mutations compared to EGFR wild-type patients. Our single-center experience on the KEYNOTE-001 trial suggested that pembrolizumab-treated EGFR-mutant patients, who were tyrosine kinase inhibitor (TKI) naïve, had superior clinical outcomes to those previously treated with a TKI. As TKI naïve EGFR-mutants have generally been excluded from pembrolizumab studies, data to guide treatment decisions in this patient population is lacking, particularly in patients with programmed death ligand 1 (PD-L1) expression ≥50%.

METHODS

We conducted a phase II trial (NCT02879994) of pembrolizumab in TKI naive patients with EGFR mutation-positive, advanced NSCLC and PD-L1-positive (≥1%, 22C3 antibody) tumors. Pembrolizumab was administered 200 mg every 3 weeks. The primary endpoint was objective response rate. Secondary endpoints included safety of pembrolizumab, additional pembrolizumab efficacy endpoints, and efficacy and safety of an EGFR TKI after pembrolizumab.

RESULTS

Enrollment was ceased due to lack of efficacy after 11 of 25 planned patients were treated. Eighty-two percent of trial patients were treatment naïve, 64% had sensitizing EGFR mutations, and 73% had PD-L1 expression ≥50%. Only 1 patient had an objective response (9%), but repeat analysis of this patient's tumor definitively showed the original report of an EGFR mutation to be erroneous. Observed treatment-related adverse events were similar to prior experience with pembrolizumab, but two deaths within 6 months of enrollment, including one attributed to pneumonitis, were of concern.

CONCLUSIONS

Pembrolizumab's lack of efficacy in TKI naïve, PD-L1+, EGFR-mutant patients with advanced NSCLC, including those with PD-L1 expression ≥50%, suggests that it is not an appropriate therapeutic choice in this setting.

Impaired growth hormone responses to growth hormone-releasing factor in obesity. A pituitary defect reversed with weight reduction

To investigate whether the impaired growth hormone secretion associated with obesity is a result of a hypothalamic or a pituitary disorder and whether it is a cause or a consequence of obesity, we studied plasma growth hormone responses to growth hormone-releasing factor in morbidly obese patients before gastrointestinal surgical therapy, in formerly obese subjects who had lost considerable weight postoperatively, and in non-obese controls. Growth hormone secretion was also assessed in response to insulin-induced hypoglycemia (in seven patients preoperatively and four postoperatively). In patients studied preoperatively, growth hormone responses to growth hormone-releasing factor were markedly impaired (P less than 0.001 as compared with controls), whereas in patients studied postoperatively they were partially restored to normal (P less than 0.05 as compared with those studied preoperatively). Growth hormone responses to insulin-induced hypoglycemia were similarly diminished in obese patients studied before operation (P less than 0.02). The growth hormone response to growth hormone-releasing factor was inversely correlated with the percentage of ideal body weight (P less than 0.01) and directly correlated with the growth hormone response to insulin (P less than 0.01). The impaired responsiveness to growth hormone-releasing factor suggests that the diminished response to insulin hypoglycemia is mediated by an impaired pituitary response to endogenous growth hormone-releasing factor. The reversibility of the defect after weight reduction suggests that it is a consequence rather than a cause of obesity.

Activation and adoptive transfer of Epstein-Barr virus-specific cytotoxic T cells in solid organ transplant patients with posttransplant lymphoproliferative disease

The treatment of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (PTLD) in EBV seronegative solid organ transplant recipients who acquire their EBV infection after engraftment poses a considerable challenge because of underlying immunosuppression that inhibits the virus-specific cytotoxic T cell (CTL) response in vivo. We have developed a protocol for activating autologous EBV-specific CTL lines from these patients and show their potential use for immunotherapy against PTLD in solid organ transplant patients. Peripheral blood mononuclear cells from a panel of solid organ transplant recipients with and without active PTLD were used to assess EBV-specific memory CTL responses. The activation protocol involved cocultivation of peripheral blood mononuclear cells with an autologous lymphoblastoid cell line under conditions that favored expansion of virus-specific CTL and hindered the proliferation of allospecific T cells. These CTL consistently showed (i) strong EBV-specificity, including reactivity through defined epitopes in spite of concurrent immunosuppressive therapy, and (ii) no alloreactivity toward donor alloantigens. More importantly, adoptive transfer of these autologous CTLs into a single patient with active PTLD was coincident with a very significant regression of the PTLD. These results demonstrate that a potent EBV-specific memory response can be expanded from solid organ recipients who have acquired their primary EBV infection under high levels of immunosuppressive therapy and that these T cells may have therapeutic potential against PTLD.

Recent advances in the utility and use of the General Practice Research Database as an example of a UK Primary Care Data resource

Since its inception in the mid-1980s, the General Practice Research Database (GPRD) has undergone many changes but remains the largest validated and most utilised primary care database in the UK. Its use in pharmacoepidemiology stretches back many years with now over 800 original research papers. Administered by the Medicines and Healthcare products Regulatory Agency since 2001, the last 5 years have seen a rebuild of the database processing system enhancing access to the data, and a concomitant push towards broadening the applications of the database. New methodologies including real-world harm-benefit assessment, pharmacogenetic studies and pragmatic randomised controlled trials within the database are being implemented. A substantive and unique linkage program (using a trusted third party) has enabled access to secondary care data and disease-specific registry data as well as socio-economic data and death registration data. The utility of anonymised free text accessed in a safe and appropriate manner is being explored using simple and more complex techniques such as natural language processing.

Time-varying magnetic fields: effect on DNA synthesis

Human fibroblasts have exhibited enhanced DNA synthesis when exposed to sinusoidally varying magnetic fields for a wide range of frequencies (15 hertz to 4 kilohertz) and amplitudes (2.3 X 10(-6) to 5.6 X 10(-4) tesla). This effect, which is at maximum during the middle of the S phase of the cell cycle, appears to be independent of the time derivative of the magnetic field, suggesting an underlying mechanism other than Faraday's law. The threshold is estimated to be between 0.5 X 10(-5) and 2.5 X 10(-5) tesla per second. These results bring into question the allegedly specific magnetic wave shapes now used in therapeutic devices for bone nonunion. The range of magnetic field amplitudes tested encompass the geomagnetic field, suggesting the possibility of mutagenic interactions directly arising from short-term changes in the earth's field.

Reproductive effects of long-term exposure to Bisphenol A in the fathead minnow (Pimephales promelas)

Bisphenol A (BPA), a high-volume chemical used to make polycarbonate plastic, epoxy resins, and other chemicals has been reported to be weakly estrogenic. To investigate the effects of long-term exposure to Bisphenol A, a multigeneration study was conducted in which fathead minnows (Pimephales promelas) were exposed to water concentrations of BPA in the range from 1 to 1280 micrograms/L. In this paper, we report the growth and reproductive effects of BPA on sexually mature adults in the F0 generation (after 43, 71, and 164 d of exposure) and the effects on hatchability in the F1 generation. Mean measured concentrations of BPA in the water for all doses, over a 164-d exposure period, were between 70% and 96% of nominal. An inhibitory effect of BPA on somatic growth (length and weight) occurred in adult male fish exposed to 640 and 1280 micrograms/L (after 71 and 164 d). BPA induced vitellogenin synthesis (VTG; a biomarker for estrogen exposure) in males at concentrations of 640 and 1280 micrograms/L after 43 d and 160 micrograms/L after 71 d. In females, plasma VTG concentrations were elevated above controls only after 164-d exposure to 640 micrograms/L. Inhibition of gonadal growth (as measured by the gonadosomatic index) occurred in both males and females at concentrations of 640 and 1280 micrograms/L after 164 d. In males, a concentration of 16 micrograms/L altered the proportion of sex cell types in the testis, suggesting inhibition of spermatogenesis. Concentrations of BPA that induced VTG synthesis and affected gonadal development were lower than those that resulted in discernible effects on reproductive output. Egg production was inhibited at a BPA concentration of 1280 micrograms/L, and hatchability in the F1 generation was reduced at a BPA concentration of 640 micrograms/L (there were not enough eggs spawned in the 1280 micrograms/L group for hatchability studies to be conducted). The results demonstrate that BPA acts as a weak estrogen to fish when administered via the water, with effects on breeding at and above 640 micrograms/L.

Randomized trial of allopurinol in the prevention of calcium oxalate calculi

In a double-blind study, we examined the efficacy of allopurinol in the prevention of recurrent calcium oxalate calculi of the kidney. Sixty patients with hyperuricosuria and normocalciuria who had a history of calculi were randomly assigned to receive either allopurinol (100 mg three times daily) or a placebo. After the study, the placebo group had 63.4 percent fewer calculi (P less than 0.001), whereas the allopurinol group had 81.2 percent fewer calculi (P less than 0.001). During the study period, the mean rate of calculous events was 0.26 per patient per year in the placebo group and 0.12 in the allopurinol group. When the treatment groups were compared by actuarial analysis, the allopurinol group was found to have a significantly longer time before recurrence of calculi (P less than 0.02). We conclude that allopurinol is effective in the prevention of calcium oxalate stones in patients with hyperuricosuria. The large reduction in the frequency of calculi in the placebo group underscores the positive treatment bias that regularly occurs in trials of prophylaxis against renal calculi when historical controls are used.

Clinical information for research; the use of general practice databases

General practice computers have been widely used in the United Kingdom for the last 10 years and there are over 30 different systems currently available. The commercially available databases are based on two of the most widely used systems--VAMP Medical and Meditel. These databases provide both longitudinal and cross-sectional data on between 1.8 and 4 million patients. Despite their availability only limited use has been made of them for epidemiological and health service research purposes. They are a unique source of population-based information and deserve to be better recognized. The advantages of general practice databases include the fact that they are population based with excellent prescribing data linked to diagnosis, age and gender. The problems are that their primary purpose is patient care and the database population is constantly changing, as well as the usual problems of bias and confounding that occur in any observational studies. The barriers to the use of general practice databases include the cost of access, the size of the databases and that they are not structured in a way that easily allows analysis. Proper utilization of these databases requires powerful computers, staff proficient in writing computer programs to facilitate analysis and epidemiologists skilled in their use. If these structural problems are overcome then the databases are an invaluable source of data for epidemiological studies.

Regulation of transcription factor AP-2 by the morphogen retinoic acid and by second messengers

The expression of the transcription factor AP-2 recently has been shown to be enhanced during retinoic acid (RA)-induced differentiation of NT2 cells, a human teratocarcinoma cell line. Here we show that this induction of AP-2 mRNA is at the level of transcription and is transient, reaching a peak 48-72 hr after the addition of RA and declining thereafter, even in the continuous presence of RA. Increased levels of AP-2 mRNA are reflected in a similar elevation of AP-2 protein and accompanied by an increase in the AP-2-binding site-dependent transcriptional activity of a reporter gene. AP-2 also has been proposed to confer TPA and cAMP inducibility on promoters/enhancers containing AP-2-binding sites. We investigated the effect of these agents on the expression of AP-2 protein and mRNA. Our experiments demonstrate that expression of the AP-2 gene in HeLa cells is not elevated significantly by TPA or by a calcium ionophore and is not enhanced at all by agents that increase intracellular cAMP concentration. In fact, AP-2 mRNA is repressed by both TPA and the calcium ionophore A23187 through a delayed response. These data suggest that the AP-2-binding site-mediated cAMP and TPA responses are not regulated at the level of AP-2 expression but, rather, achieved either by post-translational changes in AP-2 or in conjunction with another protein.

Management of invasive candidal infections: results of a prospective, randomized, multicenter study of fluconazole versus amphotericin B and review of the literature

We conducted a prospective, randomized, multicenter study comparing fluconazole and amphotericin B in the treatment of candidal infections. One hundred and sixty-four patients (60 of whom were neutropenic) with documented or presumed invasive candidiasis were assigned to treatment with either fluconazole (400 mg daily) or amphotericin B (25-50 mg daily; 0.67 mg/kg daily for neutropenic patients). Clinical response and survival rates were assessed at 48 hours, after 5 days, and at the end of therapy. Overall response rates to fluconazole and amphotericin B were similar (66% and 64%, respectively). There were no differences in response as related to site of infection, pathogen, time to defervescence, relapse, or survival rates between the groups. Adverse effects were more frequent with amphotericin B (35%) than with fluconazole (5%; P < .0001). The results of this study confirm that fluconazole is as effective as but better tolerated than amphotericin B in the treatment of candidal infections.

Multiinstitutional phase II trial of paclitaxel, carboplatin, and concurrent radiation therapy for locally advanced non-small-cell lung cancer

PURPOSE

Combined modality therapy for non-small-cell lung cancer (NSCLC) has produced promising results. A multiinstitutional phase II clinical trial was conducted to evaluate the activity and toxicity of paclitaxel, carboplatin, and concurrent radiation therapy on patients with locally advanced NSCLC.

PATIENTS AND METHODS

Forty previously untreated patients with inoperable locally advanced NSCLC entered onto a phase II study from March 1995 to December 1996. On an outpatient basis for 7 weeks, patients received paclitaxel 50 mg/m2 weekly over 1 hour; carboplatin at (area under the curve) AUC 2 weekly; and radiation therapy of 66 Gy in 33 fractions. After chemoradiation therapy, patients received an additional two cycles of paclitaxel 200 mg/m2 over 3 hours and carboplatin at AUC 6 every 3 weeks.

RESULTS

Thirty-nine patients were eligible for the study. The survival rates at 12 months were 56.3%, and at 24 months, 38.3%, with a median overall survival of 20.5 months. The progression-free survival rates at 12 months were 43.6%, and at 24 months, 34.7%, with a median progression-free survival of 9.0 months. Two patients did not receive more than 2 weeks of concurrent chemoradiotherapy and were not assessable for toxicity and response. The overall response rate (partial plus complete response) of 37 assessable patients was 75.7%. The major toxicity was esophagitis. Seventeen patients (46%) developed grade 3 or 4 esophagitis. However, only two patients developed late esophageal toxicity with stricture at 3 and 6 months posttreatment.

CONCLUSION

Combined modality therapy with paclitaxel, carboplatin, and radiation is a promising treatment for locally advanced NSCLC that has a high response rate and acceptable toxicity and survival rates. A randomized trial will be necessary to fully evaluate the usefulness of these findings.

The developmentally regulated transcription factor AP-2 is involved in c-erbB-2 overexpression in human mammary carcinoma

Overexpression of the c-erbB-2/HER2 protooncogene in breast carcinoma is controlled not only by the degree of amplification of the gene but also at the level of gene transcription. Thus, whether or not the gene is amplified, the activity of the c-erbB-2 promoter is enhanced in overexpressing cells through the binding of an additional transcription factor, OB2-1, whose activity is increased in these lines. Here we describe further characterization of OB2-1 and show that it is identical to the developmentally regulated transcription factor AP-2. Functional assays confirm that AP-2 is able to regulate c-erbB-2 expression in mammary-derived cell lines. Furthermore, although AP-2 is barely detectable in cells with the low c-erbB-2 expression phenotype, protein levels are clearly elevated in a panel of c-erbB-2-overexpressing lines. These findings demonstrate an important role for this transcription factor in human cancer.

Characterization of a dimerization motif in AP-2 and its function in heterologous DNA-binding proteins

The mammalian transcription factor AP-2 is a retinoic acid inducible sequence-specific DNA-binding protein that is developmentally regulated. In this report, the functional domains necessary for AP-2 DNA binding were studied. AP-2 required a dimerization domain and an adjacent region of net basic charge to achieve a sequence-specific protein:DNA interaction. The sequences responsible for dimerization consisted of two putative amphipathic alpha helices separated by a large intervening span region. This helix-span-helix (HSH) domain was unable to bind DNA when separated from the basic region, but was still capable of dimerization. The ability of the HSH domain to function as a module that promotes DNA binding through dimerization was further demonstrated by attaching it to the heterologous basic region of the c-Jun proto-oncogene product. The resulting chimeric protein specifically recognized an AP-1 DNA-binding site in the absence of an intact c-Jun leucine repeat and in a manner that was dependent on the presence of a functional AP-2 dimerization domain.

Taphonomy and palaeoecology of Olduvai Bed-I (Pleistocence, Tanzania)

Detailed taxonomic and taphomonic studies of rodents and palaeoecological analysis have been undertaken to investigate faunal change in Olduvai Bed-I. The palaeoenvironments inferred from rodent faunas recorded in Olduvai Bed-I suggest a change between the middle (FLK + FLKNN) and the top of the series (FLKN). Changes have also been observed from taxonomic studies of large mammals and from palynological studies. These differences have been attributed in the past to climatic change, but taphonomic studies suggest a more complex scenario. The environment at Olduvai Bed-I is here interpreted through analysis of fossil faunas and fossilization processes. Identification of the causative agents that could have altered the faunal composition provides information on the environment and on the nature of the change observed between the middle and top of Bed-I. This information can then be used to test conflicting hypotheses about the origins and amount of faunal and pollen change. Results show evidence of predation in all units of Bed-I and can be attributed to different predators along the series. Different predator behaviours explain some of the variability observed by previous authors in the small mammal species composition between the middle and the top of Bed-I. After taking taphonomy into account, the remaining faunal differences point to environmental differences between middle and upper Bed-I and even greater within the upper Bed-I sequence. These differences go beyond the range that is present today in the tropical woodland-savanna biome. Our interpretation of the palaeoenvironments is that the middle Bed-I faunas indicate a very rich closed woodland environment, richer than any part of the present-day savanna biome in Africa, changing to less rich woodland in upper Bed-I with a trend towards more open and seasonal woodlands at the top of the series.

Functional dissection of Odorant binding protein genes in Drosophila melanogaster

Most organisms rely on olfaction for survival and reproduction. The olfactory system of Drosophila melanogaster is one of the best characterized chemosensory systems and serves as a prototype for understanding insect olfaction. Olfaction in Drosophila is mediated by multigene families of odorant receptors and odorant binding proteins (OBPs). Although molecular response profiles of odorant receptors have been well documented, the contributions of OBPs to olfactory behavior remain largely unknown. Here, we used RNAi-mediated suppression of Obp gene expression and measurements of behavioral responses to 16 ecologically relevant odorants to systematically dissect the functions of 17 OBPs. We quantified the effectiveness of RNAi-mediated suppression by quantitative real-time polymerase chain reaction and used a proteomic liquid chromatography and tandem mass spectrometry procedure to show target-specific suppression of OBPs expressed in the antennae. Flies in which expression of a specific OBP is suppressed often show altered behavioral responses to more than one, but not all, odorants, in a sex-dependent manner. Similarly, responses to a specific odorant are frequently affected by suppression of expression of multiple, but not all, OBPs. These results show that OBPs are essential for mediating olfactory behavioral responses and suggest that OBP-dependent odorant recognition is combinatorial.

AP-2-null cells disrupt morphogenesis of the eye, face, and limbs in chimeric mice

The homozygous disruption of the mouse AP-2 gene yields a complex and lethal phenotype that results from defective development of the neural tube, head, and body wall. The severe and pleiotropic developmental abnormalities observed in the knockout mouse suggested that AP-2 may regulate several morphogenic pathways. To uncouple the individual developmental mechanisms that are dependent on AP-2, we have now analyzed chimeric mice composed of both wild-type and AP-2-null cells. The phenotypes obtained from these chimeras indicate that there is an independent requirement for AP-2 in the formation of the neural tube, body wall, and craniofacial skeleton. In addition, these studies reveal that AP-2 exerts a major influence on eye formation, which is a critical new role for AP-2 that was masked previously in the knockout mice. Furthermore, we also have uncovered an unexpected influence of AP-2 on limb pattern formation; this influence is typified by major limb duplications. The range of phenotypes observed in the chimeras displays a significant overlap with those caused by teratogenic levels of retinoic acid, strongly suggesting that AP-2 is an important component of the mechanism of action of this morphogen.

Non-viraemic transmission of tick-borne encephalitis virus: a mechanism for arbovirus survival in nature

The vectors of arthropod-borne viruses (arboviruses) become infected by feeding on the viraemic blood of an infected animal. This theory is based on transmission studies involving artificial infection of vertebrate hosts by syringe inoculation. To reproduce natural conditions of virus transmission, infected and uninfected vectors (ticks) of tick-borne encephalitis virus, the most important arbovirus in Europe, were allowed to feed together on uninfected wild vertebrate hosts. The greatest numbers of infected ticks were obtained from susceptible host species that had undetectable or very low levels of viraemia. The results suggest that 'nonviremic transmission' is an important mechanism for the survival of certain arboviruses in nature.

Production of the novel C-C chemokine MCP-4 by airway cells and comparison of its biological activity to other C-C chemokines

Monocyte chemotactic protein-4 (MCP-4) is a newly identified C-C chemokine with potent eosinophil chemoattractant properties. We describe studies of its biological activity in vitro to induce chemotaxis of peripheral blood eosinophils and to induce histamine release from IL-3-primed peripheral blood basophils. MCP-4 and eotaxin caused a similar rise in eosinophil intracytoplasmic Ca2+ and complete cross-desensitization. MCP-4 also abolished the eosinophil Ca2+ response to MCP-3 and partially desensitized the response to macrophage inflammatory protein-1alpha. MCP-4 activated cell migration via either CCR2b or CCR3 in mouse lymphoma cells transfected with these chemokine receptors. MCP-4 inhibited binding of 125I-eotaxin to eosinophils and CCR3-transfected cells and inhibited 125I-MCP-1 binding to CCR2b-transfectants. MCP-4 mRNA was found in cells collected in bronchoalveolar lavage of asthmatic and nonasthmatic subjects and was prominently expressed in human lung and heart. MCP-4 mRNA was expressed in several human bronchial epithelial cell lines after cytokine stimulation. Pretreatment of BEAS-2B epithelial cells with the glucocorticoid budesonide inhibited MCP-4 mRNA expression. These features make MCP-4 a candidate for playing a role in eosinophil recruitment during allergic respiratory diseases.

Efficient transmission of tick-borne encephalitis virus between cofeeding ticks

Most of the data on oral infections of ticks with tick-borne encephalitis virus have been derived from experiments using animals infected by syringe inoculation. To mimic the natural conditions of virus transmission, tick-borne encephalitis virus-infected Ixodes ricinus (Linnaeus) or Rhipicephalus appendiculatus Neumann adults (donors) were cofed with uninfected nymphs (recipients) of either tick species on uninfected guinea pigs. Two tick-retaining cells were attached to each guinea pig: cell 1 contained uninfected nymphs and virus-infected adults, and cell 2 contained uninfected nymphs. Following engorgement, 55% of I. ricinus nymphs and 65% of R. appendiculatus nymphs were shown to have acquired the virus while cofeeding with I. ricinus donor ticks. Similarly, 66% of R. appendiculatus recipient nymphs that cofed with R. appendiculatus virus-infected adults were infected. Some of the guinea pigs on which the ticks cofed were apparently nonviremic. The results indicate that efficient transmission of tick-borne encephalitis virus can occur between cofeeding ticks even when the host on which they feed does not develop a detectable viremia.