Enhancing DNA immunization by targeting ASFV antigens to SLA-II bearing cells.

One of the main criticisms to DNA vaccines is the poor immunogenicity that they confer on occasions, at least in large animals. Confirming this theory, immunization with plasmid DNA encoding two African swine fever virus genes in frame (pCMV-PQ), failed in inducing detectable immune responses in pigs, while it was successful in mice. Aiming to improve the immune responses induced in swine, a new plasmid was constructed, encoding the viral genes fused in frame with a single chain variable fragment of an antibody specific for a swine leukocyte antigen II (pCMV-APCH1PQ). Our results clearly demonstrate that targeting antigens to antigen professional cells exponentially enhanced the immune response induced in pigs, albeit that the DNA vaccine was not able to confer protection against lethal viral challenge. Indeed, a viremia exacerbation was observed in each of the pigs that received the pCMV-APCH1PQ plasmid, this correlating with the presence of non-neutralizing antibodies and antigen-specific SLA II-restricted T-cells. The implications of our discoveries for the development of future vaccines against African swine fever virus and other swine pathogens are discussed.

Genomic and antigenic characterization of viruses from the 1993 Italian foot-and-mouth disease outbreak.

The origin and evolution of the type O foot-and-mouth disease viruses (FMDV) that caused the outbreak occurrence in Italy in 1993, the first episode of the disease in the EU after adoption of a non-vaccination policy in 1991, have been studied by the analysis of sequences encoding three main antigenic sites on the viral capsid proteins. The phylogenetic tree derived from sequences spanning the carboxyterminal end of VP1 showed that these Italian viruses were grouped in the ME-SA topotype, closely related to viruses that circulated previously in the Middle East. The analysis of the nucleotide sequences in VP1, VP2 and VP3 showed a co-circulation during the epizootic of genetic variants, including viruses with amino acid replacements in VP3. For some of the isolates analyzed, values of fixation of nucleotide substitutions per year were observed in the three regions analyzed, ranging from 1.5 to 5.1 x 10(-2). The use of a panel of new monoclonal antibodies raised against an isolate from this outbreak, as well as monoclonal antibodies to FMDV O1-Switzerland 1965, showed differences in the reactivity pattern among some of the Italian isolates analyzed, which were consistent with the co-circulation of antigenic variants. These results support the potential for FMDV diversification in a limited period of time and under epidemiological conditions in which no vaccination campaigns were being implemented.

[Electroconvulsive therapy in the third trimester of pregnancy: a case report]. / Terapia electroconvulsiva en el tercer trimestre de la gestación. A propósito de un caso.

Electroconvulsive or electroshock therapy is an effective psychiatric treatment. The need for effective psychotherapy in the pregnant patient and the need to limit application of psychotropic drugs have encouraged the use of electroshock therapy in the past 50 years. We report the case of a 35-year-old woman at 30 weeks' gestation who was hospitalized with severe depression. When her condition worsened after initiation of medical treatment, electroshock therapy was considered. She received a total of 9 sessions (3 per week). During treatments the patient received general anesthesia with propofol and succinylcholine with insertion of a tracheal tube. Significant variations in the hemodynamic variables of mother and fetus were not observed; nor were there signs of fetal distress. The patient experienced clear improvement and 2 days after the last treatment spontaneous labor commenced. A healthy boy was born by vaginal delivery.

[Gas-containing hepatic abscess from an unusual etiology]. / Absceso hepático gaseoso de etiología inusual.

Pyogenic hepatic abscesses used to be caused by an abdominal infection. Cholangitis due to stones is the commonest cause, followed by diverticulitis or appendicitis. Most patients presenting with pyogenic liver abscesses have a polymicrobial infection usually with Gram negative aerobic and anaerobic organisms. Escherichia coli or Klebsiella pneumoniae are frequently implicated but they do not usually produce gas into the abscesses. We comment a case of a gas-containing liver abscess after an acute pancreatitis without any risk factor associated.

Complementation of P37 (F13L gene) knock-out in vaccinia virus by a cell line expressing the gene constitutively.

Vaccinia virus produces two different infectious forms, intracellular mature virus (IMV) and extracellular enveloped virus (EEV). Acquisition of the EEV envelope occurs by wrapping of IMV with vesicles of the trans-Golgi network (TGN). The most abundant protein in the envelope of EEV, P37, is a 37 kDa palmitylated protein encoded by the F13L gene. P37 is located in the inner side of the EEV envelope and accumulates in the TGN during infection. Deletion of gene F13L results in a severe defect in the wrapping process, although normal levels of IMV are produced. A cell line, derived from RK-13 cells, was obtained that stably expressed P37 (RK(P37)), and the properties of the protein were studied in the absence of other viral polypeptides. P37 produced in RK(P37) cells differed from P37 produced in vaccinia-infected cells in terms of hydrophobicity and intracellular distribution. Despite these differences, RK(P37) cells partially complemented the phenotypic defect of vaccinia virus P37- mutants. EEV production and cell-to-cell virus spread by mutant viruses were increased significantly in RK(P37) cells when compared to normal RK-13 cell cultures. Infection of RK(P37) cells with P37- virus substantially altered the hydrophobicity and the intracellular distribution of P37 in those cells. These results indicate the requirement of the infection context for determination of the normal palmitylation and intracellular localization of P37.

A highly divergent antigenic site of foot-and-mouth disease virus retains its immunodominance.

The ability of a highly divergent antigenic site of foot-and-mouth disease virus (FMDV) of serotype C to elicit neutralizing antibodies has been evaluated in mice and rabbits. The viruses compared, FMDV C-S8c1 and HR, differ in a single amino acid replacement in their capsid proteins, but represent two extreme antigenic specificities of the major antigenic site A of FMDV type C. Both, studies of cross-neutralization of homologous and heterologous virus, and fractionation of site A-specific antibodies by immunoaffinity chromatography suggest a similar immunodominance of antigenic site A in FMDV C-S8c1 and variant HR. This information is relevant to the formulation of synthetic peptide vaccines that ideally should consist of mixtures of peptides representing several antigenic specificities. These cocktail formulations may be required to control diseases caused by FMDV and, generally, by highly variable RNA viruses, since single specificity peptides may trigger selection of vaccine-escape viral mutants.

New observations on antigenic diversification of RNA viruses. Antigenic variation is not dependent on immune selection.

Recent results have revealed novel features in the process of antigenic diversification of FMDV. (i) Antigenic variation is not necessarily the result of immune selection. (ii) Single, critical amino acid replacements may either have a minor effect on antigenic specificity or cause a drastic antigenic change affecting many epitopes on an antigenic site. (iii) The effect of such a critical replacement may be suppressed by additional substitutions at neighbouring sites. (iv) Antigenic diversification does not necessarily involve net accumulation of amino acid substitutions over time. We review evidence that some of these features apply also to other riboviruses and retroviruses. A model is proposed to relate antigenic variation without immune selection to the quasispecies structure of RNA virus populations.

Distinct repertoire of antigenic variants of foot-and-mouth disease virus in the presence or absence of immune selection.

Antigenic variants of foot-and-mouth disease virus (FMDV) were generated and frequently became dominant in clonal populations of FMDV (clone C-S8c1) grown in the absence of anti-FMDV antibodies. We have now passaged eight samples of the same FMDV clone in the presence of a limited amount of neutralizing polyclonal antibodies directed to the major antigenic site A of capsid protein VP1. Complex populations of variants showing increased resistance to polyclonal sera and to site A-specific monoclonal antibodies were selected. Some populations exhibited marked decreases in viral fitness. Multiple amino acid replacements within site A--and also elsewhere in VP1--accumulated upon passage of the virus in either the absence or the presence of neutralizing antibodies. However, antigenically critical replacements at one position in site A occurred repeatedly in FMDV passaged under antibody selection, but they were never observed in many passages carried out either in the absence of antiviral antibodies or in the presence of an irrelevant antiviral serum. Thus, even though antigenic variation of FMDV can occur in the absence or presence of immune selection, critical replacements which lead to important changes in antigenic specificity were observed only as a result of selection by neutralizing antibodies.

Use of substituted and tandem-repeated peptides to probe the relevance of the highly conserved RGD tripeptide in the immune response against foot-and-mouth disease virus.

Antigenic site A of foot-and-mouth disease virus (FMDV) is an exposed, mobile loop which includes a central, highly conserved Arg-Gly-Asp tripeptide (RGD, VP1 residues 141-143 in serotype C) thought to be part of the cell attachment site. We have analyzed the contribution of RGD to the interaction of site A with antibodies by incorporating selected amino acid replacements at RGD into synthetic peptides representing site A, and analyzing the reactivity of substituted peptides with site A-specific monoclonal antibodies (MAbs). Replacement of Arg-141, Gly-142 or Asp-143 by alanine resulted in the loss of one, three and five epitopes, respectively, out of seven epitopes probed. Other replacements resulted in the loss of even larger numbers of epitopes, suggesting that the amino acids of the RGD region are either directly involved in interaction with antibodies or that they exert an important influence on the interaction of surrounding residues with antibodies. Thus, we explored the ability of tandem repeats of the RGDL sequence (corresponding to FMDV C-S8c1) to evoke neutralizing antibodies in rabbits and guinea pigs. Neutralizing activity was generally low but with a broad specificity for different FMDV serotypes and variants. Significant decreases in neutralizing titers were observed with boosting, suggesting a possible suppression of those anti-peptide antibodies which may also be directed to cellular RGD sequences. The results point to an involvement of RGD in the antigenic structure of site A, and open the possibility that broadly neutralizing antibodies might be induced by tandem repeats of the critical, conserved domain.