Building a network for multicenter, prospective research of central nervous system infections in South America: Process and lessons learned

Multicenter collaborative networks are essential for advancing research and improving clinical care for a variety of conditions. Research networks are particularly important for central nervous system infections, which remain difficult to study due to their sporadic occurrence and requirement for collection and testing of cerebrospinal fluid. Establishment of long-term research networks in resource-limited areas also facilitates diagnostic capacity building, surveillance for emerging pathogens, and provision of appropriate treatment where needed. We review our experience developing a research network for encephalitis among twelve hospitals in five Peruvian cities since 2009. We provide practical suggestions to aid other groups interested in advancing research on central nervous system infections in resource-limited areas.

Circulating recombinant form CRF02_AG in South America

With the objective of monitoring the distribution of HIV-1 subtypes and circulating recombinant forms (CRFs)in South America, population-based surveillance studies were performed in seven countries. Peripheral blood mononuclear cell, filter paper, fresh blood, and cocultivation samples were collected from HIV-positive patients from Colombia, Ecuador, Peru, Bolivia, Chile, Argentina, and Uruguay, during a 7-year period(1995-2001). DNA was prepared and HIV envelope subtypes were determined by heteroduplex mobility as-say and DNA sequencing from 1289 HIV-positive samples. While subtypes B and F were the most commonly observed subtypes, two CRF02_AG strains were detected, in Ecuador. This is the first report of the existence of this CRF in South America.

Characterization of antibody responses to combinations of a dengue-2 DNA and dengue-2 recombinant subunit vaccine

A dengue-2 (DEN-2) DNA vaccine coding for the premembrane and envelope (E) proteins and a recombinant fusion protein containing the B domain of the DEN-2 E protein fused to the maltose-binding protein (MBP) of Escherichia coli both elicited neutralizing antibody in mice. In order to achieve more rapid protective immunity as well as to increase the persistence of neutralizing antibody, we primed mice with the DNA vaccine (D), the recombinant MBP protein (R), or both (RD) given simultaneously, and then boosted twice with either the R (R/R/R or D/R/R) or D (D/D/D or R/D/D) constructs alone or the RD (RD/RD/RD) combination. All of the recombinant protein vaccines were given with alum as an adjuvant. The serum antibody response measured by enzyme-linked immunosorbent assay was highest in D/D/D mice and RD/RD/RD mice. The D/R/R mice showed an intermediate response, and the R/D/D and R/R/R showed the lowest response. The geometric mean (GM) 50% neutralizationtiter (50% plaque reduction neutralization, or PRNT50) was marginally higher for RD/RD/RD mice (891) at 9 months after priming than that for R/R/R mice (724). T he lowest GM PRNT50 titers were seen in the D/D/D mice (33) and R/D/D mice (40), and the D/R/R group had a slightly higher titer (156) than these 2 groups. The predominant antibody subclass for the D/D/D mice was immunoglobulin (Ig) G2a, similar to mice infected with live virus. The R/R/R mice showed an exclusive IgGI antibody response, and the RD/RD/RD response also was predominantly IgGI. The antibody subclass pattern of the R/D/D and D/R/R mice showed a more balanced distribution of both IgG1 and IgG2a. Investigating the neutralizing capacity of antibody subclasses suggested that both IgG1 and IgG2a could neutralize DEN-2 virus. Our observations indicate that the combination RD prime-boost regimen warrants further investigation as a vaccine strategy to prevent dengue infection.

Inoculation of plasmids expressing the dengue-2 envelope gene elicit neutralizing antibodies in mice

To develop a nucleic acid vaccine against dengue type-2 virus, the PreM and 92% of the envelope (E) genes were cloned into different eukaryotic plasmid expression vectors (pkCMVint Polyli and pVR1012). The resultant plasmid constructs (pD2ME and P1012D2ME) properly expressed the truncated E protein in vitro as evidenced by the expected protein size on SDS-PAGE and the ability of the protein to be recognized by monoclonal antibodies directed against conformational epitopes. Three-week-old BALB/c mice were given intradermal inoculations of each construct. Plasmid expression vectors without dengue genes were used as controls. One hundred percent of the mice that received the pD2ME and p1012D2ME constructs developed anti-dengue antibodies. These antibodies were shown to neutralize dengue type-2 virus in vitro. This is the first demonstration of the use of nucleic acid inoculation in the development of potential dengue virus. vaccines.

v-rel- and c-rel-protein complexes bind to the NF-kappa B site in vitro

Previous work by others has revealed homology between the rel oncogene and the transcription factor NF-kappa B. Further, in vitro-translated v-rel protein and c-rel protein are able to bind to an oligonucleotide containing the kappa B binding site. Unlike the in vitro-translated product, cellular Rel protein exists in high molecular weight complexes with several other proteins. In this report we show that immunopurified cellular complexes containing the v-rel protein and/or the c-rel protein are also able to bind to an oligonucleotide containing the kappa B site. These cellular complexes are heterogeneous in size, and all sizes appeared to have binding activity. UV cross-linking demonstrated that the Rel proteins themselves were bound to the DNA. Thus it is likely that the Rel proteins play a direct role in transcriptional regulation.

Torsionally tuned cruciform and Z-DNA probes for measuring unrestrained supercoiling at specific sites in DNA of living cells

We describe the development and application of "torsionally tuned" Z-DNA and cruciform probes for analyzing the level of unrestrained supercoiling at specific sites in the DNA of living cells. This approach is applicable for the analysis of dynamic differences in supercoiled DNA in different parts of plasmid, bacterial, or eukaryotic chromosomes. Using a psoralen-based assay, we have shown that the Z-DNA forming sequence (CG)6TA(CG)6, cloned into plasmid pUC8, exists as Z-DNA in 30 to 40% of plasmid molecules in wild-type Escherichia coli. This level suggested an in vivo superhelical density of sigma = -0.034 at the site of insertion in the plasmid. A higher level of Z-DNA found in cells deficient in topoisomerase I (topA10) suggested an in vivo superhelical density of sigma = -0.048. We have constructed a set of torsionally tuned inverted repeated DNA molecules which require different superhelical densities for cruciform formation. Using these inverted repeats and a crosslink assay for cruciforms, we present quantitative evidence for the existence of cruciforms in living E. coli cells. Cruciform formation was dependent on DNA supercoiling in vivo and on the location of the inverted repeat within a plasmid. In topA10 cells cruciforms were detected in less than 0.5% of plasmids when cloned into two different transcriptional units: the lacZ and CAT genes. However, when cloned outside a transcriptional unit, cruciforms were found at levels up to 50% in topA10 cells. More cruciforms were found upstream than downstream from divergent promoters in pBR322. From analysis of the fraction of different inverted repeats existing as cruciforms in vivo and the levels of supercoiling required for cruciform formation in vitro, we estimate in vivo superhelical densities of sigma = -0.034 and -0.041 for the EcoRI site of pUC8-based plasmids in wild-type and topA10 cells, respectively.

The v-rel and c-rel proteins exist in high molecular weight complexes in avian and murine cells

We reported previously that the v-rel protein (p59v-rel) exists in a high molecular weight complex with at least four other proteins in the cytoplasm of v-rel-transformed chicken pre-B lymphoid cells (Simek, S. & Rice, N.R., J. Virol., 62, 4730-4736, 1989). One of these proteins is the chicken c-rel protein, but the identities of the others (of about 36 kDa, 115 kDa, and 124 kDa) are unknown. In this report we extend that observation to additional v-rel-transformed cell lines of both pre-B and B cell phenotypes. We also introduced and expressed v-rel in several other avian cell lines (a chicken T cell line, chick embryo fibroblasts, and quail fibroblasts) and found that in these cells p59v-rel was complexed with the same proteins as observed in the v-rel-transformed cells. Thus, the associated proteins are not limited to pre-B cells, but occur and complex with p59v-rel in B cells, T cells, and fibroblasts. We next examined five uninfected avian cells and tissues and found that, with only one exception, p75c-rel was complexed with p36, p115, and p124. Thus, in most cases complex formation is not limited to or dependent on the presence of the transforming v-rel protein, but also occurs with the normal c-rel protein. To determine whether a mammalian c-rel protein is similarly associated with other proteins, we screened murine cell lines for the presence of c-rel mRNA. In agreement with our earlier findings, we found the highest expression in mature B cells, although several pre-B and myeloid cell lines were also strongly positive. Using one of the B cell lines, we detected the murine c-rel protein. We found that, like its avian counterpart, it is a protein of about 75 kDa and is associated with proteins of 36 kDa and 115 kDa. Sephacryl S-400 chromatography revealed that both the avian and murine complexes are of high molecular weight, with an average size of about 400 kDa.

Transcription initiation by RNA polymerase II in vitro. At least two nucleotides must be added to form a stable ternary complex

We have prepared RNA polymerase II preinitiation complexes by incubating templates containing the adenovirus 2 major late promoter with HeLa cell nuclear extracts in the absence of nucleoside triphosphates. These preinitiation complexes are partially purified by gel filtration and are then provided with the appropriate substrates to allow either one or two phosphodiester bonds to be formed. When substrates that allow only one bond to form are used, no stable ternary complex is obtained and no RNA is made that can be incorporated into longer RNA chains. A stable complex is obtained, however, if the RNA polymerase can make two bonds. The production of a stable ternary complex requires ATP or dATP and is inhibited by alpha-amanitin. In the course of exploring the energy requirement for initiation we found that dATP may be incorporated, in the absence of ATP, as the initial base of the RNA. However, deoxyribonucleotides are not appreciably incorporated into the body of the transcript after the first two bases have been added to the growing chain.