Detection of Cryptosporidium parvum DNA in human feces by nested PCR.

Cryptosporidium parvum is a coccidian protozoan that causes diarrhea in humans, often chronic and severe in patients with AIDS. Conventionally, diagnosis is made by concentration of stools followed by acid-fast staining (AF) or immunofluorescent staining. The threshold of detection in human stool specimens by these methods may require the presence of 50,000 (immunofluorescent staining) to 500,000 (AF) oocysts per g of stool. In this study, a nested PCR assay was developed to detect C. parvum DNA directly from stool specimens. After extraction of DNA from formalinized stool, a 400-bp fragment of C. parvum DNA was amplified with two 26-mer outer primers. The amplicon from this reaction was amplified with a second primer pair. With these nested primers, a 194-bp DNA fragment was amplified and confirmed as C. parvum DNA by internal probing with an enzyme-linked chemiluminescence system. This PCR-based test allowed the detection of 500 oocysts per g of stool or 100 ng of C. parvum DNA. Studies indicate that the primers utilized are specific for the DNA of C. parvum. DNA sequences were also detected in stool specimens from 4 of 28 patients previously reported negative by AF. In summary, a rapid, sensitive, and specific assay for the detection of C. parvum directly from stool specimens has been developed. This test has the potential for detecting asymptomatic infection, monitoring the response to therapy, and detecting the organism in environmental sources.

Intracellular amplification of proviral DNA in tissue sections using the polymerase chain reaction.

We developed a new method to amplify cell DNA in situ using the polymerase chain reaction (PCR). Proviral sequences of mouse mammary tumor virus (MMTV) contained in cultured cells and tissue sections were amplified intracellularly using a thermal cycler. Two techniques were employed to maintain the localization of the amplified DNA. First, complementary tails at the 5' ends of the oligonucleotide primers resulted in the synthesis of high molecular weight concatamers containing the target sequences. Second, the PCR was carried out in a thin film of agarose solidified over the tissue sections. The specifically amplified and localized DNA was then detected by in situ hybridization (ISH). Our results demonstrate that (a) DNA in tissue sections can serve as the target for the polymerase chain reaction in situ, (b) cell morphology is maintained, and (c) a target of 167 BP can be specifically detected in individual cells. This technique should be generally applicable to amplifying cellular DNA targets in tissue sections for detection in situ.

Construction and characterization of two infectious molecular clones of encephalomyocarditis virus.

We constructed and characterized two infectious molecular clones of encephalomyocarditis (EMC) virus. Both constructs, pDL and pDA, were assembled from five overlapping cDNA clones derived from the diabetogenic variant of EMC virus (EMC-D) and from two synthetic oligonucleotide cartridges. pDA contained a single point mutation at position 1720 within the "puff" region of capsid protein 1AB that was derived from the nondiabetogenic variant of EMC virus (EMC-B). This point mutation resulted in an amino acid substitution of arginine (EMC-B) for lysine (EMC-D). Our construction illustrates two novel findings: (i) that the problem of stably cloning long poly(C) tracts of EMC virus can be circumvented by the use of a shortened, synthetic, poly(dC-dG) oligonucleotide cartridge, and (ii) that a single point mutation in the puff region of the capsid protein 1AB leads to change in its electrophoretic mobility and to a change in the plaque size of recombinant virus.

In situ detection of human immunodeficiency virus (HIV) nucleic acid in H9 cells using nonradioactive DNA probes and an image cytophotometry system.

Rapid and sensitive nonradioactive methods to detect human immunodeficiency virus (HIV)-infected cells are needed in clinical medicine. We developed an in situ hybridization test using 2-acetylaminofluorene (AAF)-labeled HIV DNA as a hybridization probe. Hybridized probe was detected using rabbit anti-AAF antibody, followed by alkaline phosphatase-conjugated goat anti-rabbit, and the bromochloroindolyl phosphate-nitroblue tetrazolium reaction. An image cytophotometry system was used to quantitate the percentage of HIV-infected cells. These methods were used to determine the percentage of H9 cells infected with HIV. HIV was detected in 0% of cells on day 1 post infection, 7% on day 4, 41% on day 8, and 5% on day 15. These results paralleled those of the reverse transcriptase assay and an antigen capture ELISA assay for HIV antigen. Thus the AAF modified HIV DNA probe detected HIV nucleic acid in infected H9 cells and the image cytophotometry system improved the sensitivity and objectivity of detection.

Comparison of the nucleotide sequences of diabetogenic and nondiabetogenic encephalomyocarditis virus.

The nucleotide sequences of a diabetogenic variant of encephalomyocarditis (EMC) virus (D variant, ifp- phenotype) and a nondiabetogenic variant of EMC virus (B variant, ifp+ phenotype) have been compared. These variants differ at eight sites. The poly(C) tract of EMC-B is three bases shorter than that of EMC-D. Of the seven sites at which nucleotide substitutions were confirmed using RNA templates, four resulted in amino acid changes in three different proteins, the leader peptide, 1B (VP2), and 1D (VP1). The biological significance of these differences can now be investigated.

Comparison of non-radioactive DNA hybridization probes to detect human immunodeficiency virus nucleic acid.

Simple and sensitive methods to directly detect the human immunodeficiency virus (HIV) are needed for routine use in the clinical laboratory. In this study, we compared DNA probes prepared by: (1) nick translation with biotinylated dATP; (2) direct covalent biotinylation with photobiotin; (3) direct covalent reaction with 2-acetylaminofluorene (AAF); and (4) a standard radioactive (32P) nick translation procedure. These four DNA probes were hybridized with dilutions of purified target HIV DNA blotted onto nitrocellulose strips. Hybridization was detected using a complex of strepavidin-alkaline phosphatase [for (1) and (2)], alkaline phosphatase-tagged antibodies [for (3)] and by autoradiography [for (4)]. Alkaline phosphatase was detected colorimetrically using nitroblue tetrazolium and 5-bromo-4-chloro-3-indolyl phosphate. After 1 h, AAF probes were most sensitive (amount detected less than 5 pg), followed by biotin (10 pg), photobiotinylated probes (20 pg) and the radioactive probe (10 pg). The AAF probes were then used to detect HIV DNA in infected CEM cells. We conclude that non-radioactive DNA labelling methods can be used to directly detect HIV DNA under conditions compatible with present clinical laboratory procedures.

Encephalomyocarditis virus-induced diabetes mellitus in mice: model of viral pathogenesis.

Encephalomyocarditis (EMC) virus induction of diabetes mellitus in mice has proven to be an excellent experimental model for the pathogenesis of viral disease. In SJL and DBA/2 mice, diabetes results exclusively from the infection and damage of beta cells by the virus. In addition, in BALB/cBy mice subclinical beta cell damage caused by the virus is followed by autoimmune beta cell destruction, which results in hyperglycemia. Studies of two closely related plaque variants (EMC-D and EMC-B) selected from the M strain of EMC virus revealed differences in the interferon response associated with viral infection. The EMC-D variant causes diabetes in infected SJL mice by direct beta cell destruction. Infection with EMC-B does not cause diabetes and interferes with the production of diabetes by EMC-D due to the greater ability of EMC-B than of EMC-D to induce interferon in mice. Circulating interferon has a greater effect on inhibition of viral replication because local interferon production is amplified in interferon-primed cells infected with EMC-B. These properties are determined by the interferon-inducing particle (Ifp+) phenotype of EMC-B and the Ifp- phenotype of EMC-D.

The genomic RNA of diabetogenic encephalomyocarditis virus: characterization and molecular cloning.

The RNA of a diabetogenic variant of encephalomyocarditis (EMC) virus (D variant, ifp- phenotype) and a nondiabetogenic variant of EMC virus (B variant, ifp+ phenotype) which were derived from the same virus stock (M strain) have been compared. The size of both genomes is estimated at 7.7 kb. The poly(C) tract of EMC-D is estimated at 144 bases, whereas that of EMC-B is 141 bases in length. The untranslated 5' terminal 103 nucleotides are identical for B and D with preservation of a stable terminal hairpin structure. The entire open reading frame of both variants has been cloned and the restriction maps of 12 different enzymes are identical. These maps were compared to a computer-generated restriction map of another strain of EMC virus which has been cloned and sequenced by Palmenberg et al. (1984, Nucleic Acids Res. 12, 2969-2985). Approximately 50% of the restriction sites of the B and D variants had similar locations in this strain of EMC. We conclude that significant genetic variation exists between the M strain (B and D variants) and the Palmenberg strain of EMC virus. However, the B and D variants are very similar at the molecular level and comparison of their nucleotide sequences will be necessary to reveal the basis for their different biological properties.

Relative sensitivity of cell culture systems in the detection of herpes simplex viruses.

Guinea pig embryonic fibroblasts were more sensitive and McCoy and Hep-2 cells were less sensitive than human foreskin fibroblasts in parallel titrations of herpes simplex virus. No difference in sensitivity was found for five lines of human fetal lung fibroblasts (including WI-38 cells), two lines of human embryo fibroblasts, one line of human foreskin fibroblasts, cells from a human fetal kidney, amnion cells from a human placenta, the Chang liver cell, the HeLa cell, and a line of mink cells. The cell doubling level of human or guinea pig fibroblast lines did not affect their sensitivity. One hundred ninety-five clinical specimens submitted for herpes simplex virus isolations were tested in parallel in primary rabbit kidney, guinea pig embryo, and human fetal lung fibroblast cultures. The percentages of positive or false-negative cultures were essentially the same for the three types of cells.

Interferon-sensitive coxsackievirus variants in nature.

Variants of a clinical isolate of coxsackie B-4 virus that differ in interferon (IFN) sensitivity were selected from virus stock both before and after passage in mice. IFN sensitivity was a stable property on subsequent plaque selection. The IFN-sensitive variant was less virulent than its IFN-insensitive counterpart, whether from the original virus stock or from mouse passaged virus. None of these variants was diabetogenic in mice. These studies demonstrate that coxsackievirus variants of differing IFN sensitivity exist in nature and that this property can modulate virus virulence.

Diabetogenic potential of coxsackie B viruses in nature.

Thirty-seven clinical isolates of coxsackievirus (CV) serotypes B-1, B-3, B-4, and B-5 were inoculated into male SJL mice. Twelve strains resulted in minor abnormalities of glucose metabolism in one or more of six infected mice (Tables 1 and 2). Sequential infection of male SJL mice with CVB-3, CVB-4, and CVB-5 resulted in abnormal glucose metabolism in 25 percent of the mice (Fig. 1). The glucose index of the abnormal animals was similar to that produced by sequential infection with reovirus and cytomegalovirus but less than that seen with more severe beta cell tropic agents such as streptozotocin or encephalomyocarditis virus. Infection of autoimmune New Zealand (NZB X NZW) F1 male mice with CBV-3, CVB-4, and CVB-5 resulted in transient elevation of the blood glucose concentration associated with acute acinar pancreatitis (Fig. 2). In spite of recent evidence that infection with the coxsackie B viruses can result in human diabetes mellitus, the diabetogenic potential of CVB field strains appears to be limited. Diabetes mellitus may occur as a rare event, limited to genetically susceptible hosts. Autoimmune mechanisms or repeated infection with other CVB serotypes may convert minimal beta-cell destruction into clinically overt disease.

Latent herpesviruses of humans.

The herpesviruses that infect humans characteristically establish a latent infection that may be reactivated later. The consequences of reactivation range from asymptomatic shedding to severe disseminated infection. Varicella-zoster and herpes simplex viruses are both highly neurotropic, establishing nonreplicating infections in sensory ganglia. Latent herpes simplex virus is known to reside in neurons, and the virus-cell interactions involved have been defined to an extent. Cytomegalovirus and Epstein-Barr virus interact with peripheral blood leukocytes. Latent cytomegalovirus infection of human leukocytes has not been proved, although studies in a murine model have implicated B lymphocytes as a repository of latent virus. Epstein-Barr virus is known to persist in a non-replicating state as extrachromosomal DNA in B lymphocytes and to cause "immortalization" of the infected cell; persistence of the viral genome in epithelial cells may also result in malignant transformation, such as nasopharyngeal carcinoma.

Relationship of interferon-inducing particle phenotype to encephalomyocarditis virus-induced diabetes mellitus.

The B (nondiabetogenic) and D (diabetogenic) variants of encephalomyocarditis (EMC) virus were studied to further define the role of the interferon (IFN) system in murine virus-induced diabetes mellitus. The relationship between the initial multiplicity of infection with EMC-B and the IFN yield showed that cells infected with one IFN-inducing particle produce a maximum amount of IFN, whereas IFN production is suppressed in cells infected with two or more particles. The IFN yield induced by EMC-D was less than 5% of that induced by EMC-B, allowing the designation of the B and D variants as Ifp+ and Ifp-, respectively. The Ifp+ property of the virion was shown to be responsible for the greater sensitivity of EMC-B to exogenous IFN as a result of primed local IFN induction. The data indicate that different Ifp phenotypes occur in nature and are associated with the development of diabetes in mice.

The role of interferon in virus-induced diabetes.

The repeated administration of interferon (IFN) or an IFN inducer reduced the development of diabetes in mice infected with the D variant of encephalomyocarditis (EMC) virus. Mice treated with the IFN inducer had less infectious virus, fewer pathologic changes, and higher concentrations of immunoreactive insulin in the islets of Langerhans in comparison with untreated mice. Antibody to mouse IFN (MuIFN) suppressed circulating IFN in mice infected with the B variant of EMC virus. Mice treated with antibody to MuIFN had four times more infected islet cells and 10 times more infectious virus in the pancreas compared with untreated mice. Of the surviving animals treated with antibody to MuIFN, approximately 40% developed mild diabetes whereas none of the mice developed diabetes when infected with the B variant of EMC virus alone. The IFN system is an important determinant of the outcome in EMC virus-induced diabetes in mice.

CSF lactate in diseases of the CNS.

The usefulness of the CSF lactate concentration in the diagnosis of bacterial meningitis was studied in 109 adults and children with a variety of infectious and neurologic diseases. A positive correlation was found between elevated lactate levels and the presence of leukocytes in the CSF. Elevations of the CSF lactate concentration with concomitantly negative Gram's stains and cultures were found in patients with infections at anatomic sites other than the CNS, accidental or neurosurgical head trauma, subarachnoid hemorrhage, and seizures due to alcoholism. When performed routinely on CSF, the positive predictive value was 31%, indicating that a diagnosis other than bacterial meningitis is more likely. We conclude that the CSF lactate concentration does not contribute to the diagnosis in children or adults with suspected meningitis.