The discovery of thiamethoxam: a second-generation neonicotinoid.

Neonicotinoids represent a novel and distinct chemical class of insecticides with remarkable chemical and biological properties. In 1985, a research programme was started in this field, in which novel nitroimino heterocycles were designed, prepared and assayed for insecticidal activity. The methodology for the synthesis of 2-nitroimino-hexahydro-1,3,5-triazines, 4-nitroimino-1,3,5-oxadiazinanes and 4-nitroimino-1,3,5-thiadiazinanes is outlined. Bioassays demonstrated that 3-(6-chloropyridin-3-ylmethyl)-4-nitroimino-1,3,5-oxadiazinane exhibited better insecticidal activity than the corresponding 2-nitroimino-hexahydro-1,3,5-triazine and 4-nitroimino-1,3,5-thiadiazinane. In most tests, this compound was equally or only slightly less active than imidacloprid. A series of structural modifications on this lead structure revealed that replacement of the 6-chloro-3-pyridyl group by a 2-chloro-5-thiazolyl moiety resulted in a strong increase of activity against chewing insects, whereas the introduction of a methyl group as pharmacophore substituent increased activity against sucking pests. The combination of these two favourable modifications led to thiamethoxam (CGA 293 343). Thiamethoxam is the first commercially available second-generation neonicotinoid and belongs to the thianicotinyl sub-class. It is marketed under the trademarks Actara for foliar and soil treatment and Cruiser for seed treatment. The compound has broad-spectrum insecticidal activity and offers excellent control of a wide variety of commercially important pests in many crops. Low use rates, flexible application methods, excellent efficacy and the favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.

Variability of the Hepatitis B Surface Protein in HBV-Infected Liver Transplant Recipients.

Variations in the major surface proteins (HBsAg) of hepatitis B virus (HBV) have been implicated in the high rate of reinfection in HBV-infected recipients of orthotopic liver transplantations (OLT). Sera from 6 OLT patients positive for HBsAg and from 3 recipients negative for it prior to transplantation were analyzed over several years, and 39 HBsAg sequences were compared. Despite anti-HBs immunoprophylaxis resulting in the disappearance of HBsAg, HBV DNA was detectable by a sensitive nested PCR in almost all sera. In 1 patient, a significant temporary shift in HBV subtypes was observed, indicating a mixed infection or the presence of multiple HBV populations in this patient; this was also true for other patients. Amino acid substitutions compared to wild-type HBV subtypes in 7 patients and variations within patients in 5 patients were detectable over time; the 'escape mutation' at amino acid position 145 was detected in 2 patients. Our data suggest that the high rate of reinfection in OLT recipients seems not to be associated with specific sequence variations in the major HBs gene, but shows a remarkable inter- and intraindividual variability. Obviously, no correlation between heterogeneity in this gene and clinical outcome was present. Copyright 1997 S. Karger AG, Basel

Individuals with antibodies against hepatitis B core antigen as the only serological marker for hepatitis B infection: high percentage of carriers of hepatitis B and C virus.

BACKGROUND/AIMS: Several reports have unequivocally demonstrated that some individuals with antibodies against hepatitis B core antigen as the only serological marker for hepatitis B infection are chronic carriers of the hepatitis B virus. Nevertheless, conflicting data exist about the frequency of this phenomenon; its cause is unknown. METHODS: In a prospective study we tested individuals who were positive for anti-HBc alone for HBV-DNA as well as for coexisting infections with human immunodeficiency virus and hepatitis C virus. RESULTS: Using polymerase chain reaction with primer pairs from three different regions of the hepatitis B virus genome, we found 54 of 164 individuals (32.9%) with anti-HBc alone to be positive for hepatitis B virus, the majority of them showing very low hepatitis B virus concentrations. 14.3% were human immunodeficiency virus positive; half of them were also hepatitis B virus carriers. Surprisingly, 62 of 153 participants (40.5%) in this study showed antibodies against hepatitis C virus, and about two thirds of the latter were also positive for HCV-RNA. This finding could be confirmed by a retrospective analysis of all people tested for hepatitis B virus markers and anti-HCV in our institution during the 2 years before the prospective study was begun. Again, a high correlation was found between the presence of anti-HCV and anti-HBc alone: 49.2% of individuals with anti-HBc only were anti-HCV positive also, compared to 26.8% of HBsAg carriers and only 10% of individuals showing the serological pattern of past hepatitis B. CONCLUSIONS: Thus our study of individuals positive for anti-HBc alone revealed a high number of carriers of hepatitis B virus and hepatitis C virus among them; furthermore, we found some evidence that hepatitis C virus infection may favour this unusual hepatitis B virus marker pattern.

Detection by PCR of human polyomaviruses BK and JC in immunocompromised individuals and partial sequencing of control regions.

Immunocompromised individuals were tested for the presence of the human polyomaviruses JC (JCV) and BK (BKV) by the polymerase chain reaction (PCR). The use of appropriate primers in a nested PCR allowed the detection of both viruses simultaneously. Viruses were differentiated by restriction fragment length analysis of amplified DNA fragments. Both BKV and JCV DNA were detected in the urine of an AIDS patient with progressive multifocal leukencephalopathy. In autopsy materials from this patient, JCV- but not BKV-DNA was found in brain and kidney tissue, whereas lung tissue was negative for both virus DNAs. To evaluate the methodology further, hybridization-positive urines from three recipients of bone marrow transplants and a positive urine of an acute myeloid leukemia patient were analyzed by this PCR method. One case was positive both for BKV and JCV, two cases were positive only for BKV, and one was negative for both. Parts of the control regions of JCV and BKV were sequenced directly from PCR-derived fragments. The JCV sequence from urine of the AIDS patient compared to sequences from a bone marrow transplant recipient and to archetypical reference strains showed two nucleotide (nt) exchanges out of 250 nt. The BKV sequences from the AML and the AIDS patients showed five nt exchanges out of 265 nt in the control region and were identified as BKV WW or WWT3 strains. In the agnogene region five exchanges were detected, two of them resulting in non-conservative amino acid exchanges. The possibility of testing clinical specimens of different origins by this PCR method is important for elucidating often unclear clinical courses in immunocompromised patients.(ABSTRACT TRUNCATED AT 250 WORDS)

The Sukhumi primate monkey model for viral lymphomogenesis: high incidence of lymphomas with presence of STLV-I and EBV-like virus.

T-cell leukemia virus-like proviral sequences (STLV-I) as well as EBV-like sequences were detected in PBLs and tissues of non-human primates (Papio hamadryas baboons, Green monkeys and Macaca arctoides; Sukhumi Primate Center/Georgia) by PCR. Surprisingly, two different types of STLV-I within Papio hamadryas baboons were found. One of its represents the baboon prototype STLV-I-Su described earlier, present in lymphomatous baboons from the "high-lymphoma stock", which shows about 83% homology to HTLV-I and 85% to STLV-I in the env and tax genes. The inter-individual variability within this subtype is very low (about 1% in the tax gene). The second subtype was mainly found in asymptomatic animals from the control colony and showed in the env gene 95% homology to HTLV-I, but only 82% to the prototype baboon sequence. The presence of two subtypes within the Sukhumi baboon population might be interesting in respect to the inoculation experiments with human leukemic blood and to possible interspecies transmissions. The nature of the Herpes Papio-virus was elucidated as EBV-like and the homology to the human EBV was > 90% in the polymerase gene. The homologies between different monkey species were between 92 and 96% and also here two subtypes within the baboons were detected. This is the first direct demonstration by sequencing that the Herpes Papio virus is closely related to EBV. For further studies of this animal model, rabbits were inoculated with cells originated from lymphomatous baboons and macaques. The rabbits developed generalized lymphomas lethal within 1-2 months. EBV-like and STLV-I-like sequences could be detected by PCR and sequencing showed 99-100% identity to the inoculum, indicating in fact the transmission from monkey to rabbit. These animal models seem to be very suitable for the elucidation of the pathogenesis of human HTLV-I associated T-cell leukemia/lymphoma and might be further on used for therapeutical and preventative studies.

Identification of type A and B isolates of Epstein-Barr virus by polymerase chain reaction.

A method is described for the identification of type A and type B isolates of Epstein-Barr virus (EBV) by means of the polymerase chain reaction. The use of three pairs of primers specific for genomic sequences coding for the two forms of EBV nuclear antigen (EBNA), 2A and 2B, and for a DNA sequence from the BamZ/BamR region allows the reliable and rapid detection of type A and B viruses in as little as 1000 EBV positive cells.