Cognitive control in number processing: new evidence from number compatibility effects in task-switching.

A growing body of research suggests that basic numerical abilities such as number magnitude processing are influenced by cognitive control processes. So far, evidence for number processing being affected by cognitive control processes stems primarily from observed adaptations of numerical effects to stimulus set characteristics (e.g. order or ratio of specific stimulus types). Complementing previous research on adaptation to stimulus set characteristics as an index of influences of cognitive control, the present study employed a task-switching paradigm to examine how cognitive control processes influence number processing. Participants were presented with a two-digit number and had to either judge its parity or compare its magnitude to a standard depending on a preceding cue. We expected numerical congruency effects (i.e. the unit-decade compatibility effect for magnitude comparisons and the parity congruity effect for parity judgements) to be larger in switch trials, as persisting activation of the task set of the preceding trial should increase interference. In contrast to our expectations, both numerical congruity effects were reduced following task switches as compared to repetitions. This interaction of task-switching with numerical congruency effects suggests an influence of cognitive control on basic number processing in form of persisting inhibition of previously abandoned task sets, so that these exert less influence on current number processing demands.

Markers of foamy virus infections in monkeys, apes, and accidentally infected humans: appropriate testing fails to confirm suspected foamy virus prevalence in humans.

Foamy viruses (FVs) persist in healthy individuals of various mammalian species, including nonhuman primates. Laboratory markers of FV infection are (1) virus in throat epithelium or peripheral blood lymphocytes (PBLs), (2) proviral DNA sequences in PBLs and various solid organs, and (3) antibodies reactive to viral antigens on Western blots, in radioimmunoprecipitation tests, and in immunofluorescence assays. Using PCR and serological tests, we readily detected FV markers in naturally infected African green monkeys, rhesus monkeys, and chimpanzees, as well as in accidentally infected humans. Transmission of simian foamy viruses to humans (by bite or inadvertent laboratory infection) leads to viral markers, without affecting the recipient. Reports on FV-associated clinical disorders (e.g., thyroid or neurological) have remained controversial. In this study we failed to detect, by PCR, viral sequences in the samples from 223 patients, including 16 HIV-infected Africans, 46 Graves' disease patients, and 28 patients with the de Quervain's thyroiditis. Evaluation of 2688 sera from suspected high-risk areas (e.g., Central and East Africa, or high-risk groups such as HIV-infected individuals and patients with AIDS, thyroid, and neurological disorders) did not reveal FV-specific antibodies in a single case. Previously reported FV seroprevalence in various populations has never been verified by appropriate confirmatory tests. The strain of "human foamy virus" has remained a unique isolate. In conclusion, FVs are unlikely--at present--to circulate in human populations.

Search for retrovirus in the chronic fatigue syndrome.

AIM: To examine peripheral blood and skeletal muscle from patients with chronic fatigue syndrome for exogenous retrovirus. METHODS: Blood samples from 30 patients and muscle biopsy specimens of 15 patients were examined for retroviral sequences by DNA extraction, polymerase chain reaction (PCR), and Southern blotting hybridisation. Sera were examined for human foamy virus by western immunoblotting and indirect immunofluorescence techniques. RESULTS: No differences between the patient and control populations was found for any of the PCR primer sets used (gag, pol, env, and tax regions of HTLV I/II). An endogenous gag band was observed in both the patient and control groups. All sera were negative for antibody to human foamy virus. CONCLUSION: The results indicate that there is no evidence of retroviral involvement in the chronic fatigue syndrome.

Coronavirus induced encephalomyelitis: an immunodominant CD4(+)-T cell site on the nucleocapsid protein contributes to protection.

In this communication we present clear evidence, that the N-protein of MHV-JHM contains immunodominant CD4+ T-cell sites. These sites were recognized by the immune system of virus infected Lewis rats. In previous investigations we have shown, that CD4+ T-cell lines with specificity for defined viral proteins can be selected from diseased Lewis rats and mediate protection, if transferred to otherwise lethally infected animals. To define regions of the N-protein, which are immunodominant for the T-cell response, we employed bacterially expressed N-protein and truncated subfragments of N as an antigen. We demonstrate, that T-cells from MHV-JHM infected, diseased Lewis rats recognized with high prevalence the carboxyterminal subfragment C4-N (95 aa) and to some extent the adjacent C3-N protein. The same results were obtained with T-cells derived from rats immunized with bacterially expressed N-protein or from animals vaccinated by a stable N-protein expressing vaccinia recombinant. Finally, transfer of CD4+ line T-cells to MHV-JHM infected rats specific for C4-N mediated protection against acute disease.

On the move? Echinococcus multilocularis in red foxes of Saxony-Anhalt (Germany).

Echinococcus multilocularis is a cestode parasites that frequently occurs in the red fox (Vulpes vulpes), which is the main definitive host in Central Europe. The parasite may infect humans as accidental intermediate hosts and cause alveolar echinococcosis. In the German federal state of Saxony-Anhalt, the occurrence of E. multilocularis in red foxes as a possible source of infection for humans was studied from 1998 to 2010. A significant shift in the geographical centroid of the occurrence of E. multilocularis from a long-known highly endemic area in the southwest of the state towards the north-northeast (3.2 km/year) was found. The overall prevalence in the state increased significantly from 13.6% (1998-2005) to 23.4% (2006-2010). No autochthonous cases of alveolar echinococcosis have been reported to date in Saxony-Anhalt, but this might change in the near future with the spread and increasing biomass of the parasite.

Toxoplasma gondii in foxes and rodents from the German Federal States of Brandenburg and Saxony-Anhalt: seroprevalence and genotypes.

Data on the genotypes of Toxoplasma gondii circulating in wildlife are scarce. In the present study, foxes and rodents from two Federal States in Central or Eastern Germany were examined for T. gondii infections. Body fluids were collected at necropsy or fluids were obtained from frozen tissues of naturally exposed red foxes (Vulpes vulpes), voles (Microtus arvalis), shrews (Neomys anomalus) and a striped field mouse (Apodemus agrarius) and tested for T. gondii by serology. DNA isolated from tissues of seropositive foxes and all the rodents was examined by PCR. In the German Federal States of Brandenburg and Saxony-Anhalt 152/204 (74.5%) and 149/176 (84.7%) of foxes, respectively, but none of the rodents (0/72) had antibodies to T. gondii. Only 28/152 (18.4%) and 20/149 (13.4%) of seropositive foxes from Brandenburg and Saxony-Anhalt, respectively, but none of the rodents tested PCR-positive for T. gondii. The complete T. gondii genotype could be determined for twelve samples using nine PCR-restriction fragment length polymorphism (PCR-RFLP) markers (newSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, PK1, L358 and Apico). In addition to T. gondii clonal type II (Apico II) and type II (Apico I), type III and T. gondii genotypes showing non-canonical allele patterns were observed in foxes. This suggests that, while T. gondii type II prevails in foxes, other genotypes circulate in wildlife. The population structure of T. gondii in Germany may be more diverse than previously thought.

Nuclear localization of foamy virus Gag precursor protein.

All foamy viruses give rise to a strong nuclear staining when infected cells are reacted with sera from infected hosts. This nuclear fluorescence distinguishes foamy viruses from all other retroviruses. The experiments reported here indicate that the foamy virus Gag precursor protein is transiently located in the nuclei of infected cells and this is the likely reason for the typical foamy virus nuclear fluorescence. By using the vaccinia virus expression system, a conserved basic sequence motif in the nucleocapsid domain of foamy virus Gag proteins was identified to be responsible for the nuclear transport of the gag precursor molecule. This motif was also found to be able to direct a heterologous protein, the Gag protein of human immunodeficiency virus, into the nucleus.

Identification of pol-related gene products of human foamy virus.

Human foamy virus pol gene fragments were molecularly cloned into a procaryotic expression vector. The expression pattern of the cloned fragments and nucleotide sequence analysis of the 5' pol gene region revealed that in HFV the protease (PR) is located in the pol open reading frame. Purified recombinant proteins were used to generate antibodies in rats. In immunoblot assay, using infected cells as antigen, a precursor protein with an apparent molecular mass (M(r)) of 127K was identified by antibodies directed against the reverse transcriptase (RT), RNaseH, or integrase (IN) domains of pol. With concentrated virus as antigen, the RT and RNaseH antibodies recognized a protein of 80K, the IN antiserum recognized a protein of 40K, and the PR antiserum detected a protein of approximately 10K.

An immunodominant CD4+ T cell site on the nucleocapsid protein of murine coronavirus contributes to protection against encephalomyelitis.

The murine coronavirus neurotropic strain JHM (MHV-JHM) nucleocapsid (N) protein induces a strong T-helper cell response in Lewis rats. It has been shown previously that N-specific CD4+ T cells can confer protection against acute disease upon transfer to otherwise lethally infected rats. To define the major antigenic regions that elicit this T cell response, truncated fragments of N protein were expressed from a bacterial expression vector and employed as T cell antigens. Lymphocytes from either MHV-JHM-infected or immunized rats were stimulated in culture with virus antigen, grown and tested for their specificity to the N protein fragments. The carboxy-terminally located C4-N fragment (95 amino acids) induced the most pronounced proliferative response irrespective of whether the lymphocyte culture was derived from immunized or MHV-JHM-infected rats. We established T cell lines specific for the truncated N protein fragments and tested their potential to mediate protection by transfer experiments. Only the T cell line C4-N and the T cell line specific for the full-length N protein were protective. By contrast, all truncated N protein fragments elicited a humoral immune response and contained antigenic sites recognized by antibodies from diseased rats.

Nucleocapsid or spike protein-specific CD4+ T lymphocytes protect against coronavirus-induced encephalomyelitis in the absence of CD8+ T cells.

To investigate the antiviral CD4+ T cell response in coronavirus MHV-JHM-induced encephalomyelitis, spleen and thymic lymphocytes from diseased rats were stimulated in culture with virus Ag, expanded and tested for their specificity to viral proteins and nucleocapsid (N) and spike (S) proteins that had been expressed in bacteria. A strong T cell response specific for N was measurable during acute disease, whereas S-specific T cells were only detectable in rats with a later onset of disease. CD4+ T cell lines with specificity for virus and either N or S protein were established and their influence on the course of a mouse hepatitis virus-JHM infection was investigated. All lines were of the CD4+ phenotype. Both N and S protein-specific CD4+ T cells conferred protection to infected Lewis rats and reduced the amount of infectious virus in the central nervous system. After transfer of CD4+ T cells and challenge with virus, an increase in the antiviral IgM response occurred, but neutralizing antibodies were not detectable during the period of virus clearance. Previous CD8+ cell depletion did not abrogate protection mediated by CD4+ T cell line transfer.