Genotypic variation among wild isolates of Heliothis spp nuclear polyhedrosis viruses from different geographical regions.

Staphylococcal Enterotoxins (SEs) have been raising health concerns for food safety due to their association with staphylococcal foodborne poisoning (SFP). As superantigens, they also cause the life threatening toxic shock syndrome (TSS), the transmission of which via food cannot be ruled out despite the lack of epidemiological evidence. To date, at least 23 of these exotoxins are known and separated into SEs and Staphylococcal Enterotoxin-like (SEl) depending on whether or not they invoke emesis. This work presents an up-to-date overview on the presently known SEs/SEls from the perspective of their classification, pathogenesis, and genetic organisation. The incidence of these toxins in dairy products, the risk this poses to the public health, and possible control means are also reviewed.

Staphylococcal enterotoxins and enterotoxin-like toxins with special reference to dairy products: An overview

Homologous regions (hrs) were identified in the Lymantria dispar nuclear polyhedrosis virus (LdMNPV) genome. A 1.58-kb region surrounding hr4 was sequenced and found to have two distinct domains. Domain I (about 600 bp) is composed of seven repeats of about 80 bp including a series of palindromes containing MluI sites and overlapping XhoI and SacI sites. Domain II (about 700 bp) is composed of eight partially repeated sequences of 60 to 100 bp containing a 15- to 25-bp sequence that is 80 to 100% A+T in addition to a 6- to 10-bp palindrome containing an NruI site. Hybridization of a domain I sequence to cosmids containing the LdMNPV genome indicated its presence at eight positions (hr1 to -8) on the genome. In contrast, hybridization of domain II indicated that it was present only at the hr4 locus. A DpnI-based transient-replication assay was used to determine if subclones of hr4 transfected into LdMNPV-infected L. dispar cells functioned as replication origins. Subclones of hr4 containing either domain I or domain II replicated at very low or moderate levels, respectively. However, when domain I and domain II were linked on the same plasmid, high levels of replication were observed. A 1.4-kb region containing hr1 was also sequenced. It lies immediately upstream of the polyhedrin gene and contains six domain I-type repeats. Four-hundred-base-pair regions of domain I repeats from hr1 and hr4 showed 89% sequence identity. Plasmids containing the hr1 domain I replicated at low levels. However, hybrid plasmids in which the AT-rich hr4 domain II was inserted adjacent to hr1 domain I replicated to high levels, indicating that the AT-rich domain II greatly enhances replication. The orientation and position of domains I and II relative to each other did not have major effects on the levels of replication.

Lymantria dispar nuclear polyhedrosis virus homologous regions: characterization of their ability to function as replication origins.

A Lymantria dispar nuclear polyhedrosis virus (LdMNPV) gene has been identified that encodes a homolog to the granulovirus (GV) enhancin proteins that are capable of enhancing the infection of other baculoviruses. Enhancin genes have been identified and sequenced for three species of GVs but have not been found in any other nuclear polyhedrosis virus to date. The LdMNPV enhancin gene is located between 67.6 and 70.1 kbp on the viral genome. Northern and primer extension analyses of viral RNAs indicate that the enhancin gene transcripts are expressed at late times postinfection from a consensus baculovirus late promoter. The LdMNPV enhancin exhibits 29% amino acid identity to the enhancin proteins of the Trichoplusia ni, Pseudaletia unipuncta, and Helicoverpa armigera GVs. All four proteins contain a conserved zinc-binding domain characteristic of metalloproteases. A recombinant virus (enhancin::cat) was constructed in which the LdMNPV enhancin gene was inactivated by insertion mutagenesis in order to ascertain the effect of the enhancin protein on viral potency. The bioassay results indicate that disruption of the enhancin gene in the LdMNPV results in a reduction in viral potency.

/pdf/molecular-analysis-of-an-enhancin-gene-in-the-lymantria-4ndlhpaq8a.pdf

Molecular analysis of an enhancin gene in the lymantria dispar nuclear polyhedrosis virus

Identification of two nuclear polyhedrosis viruses from the cabbage moth, Mamestra brassicae (Lepidoptera: Noctuidae)

Thermal inactivation profiles of staphylococcal enterotoxins B (SEB) and C (SEC) at 80, 100, and 121 C showed that SEC is more resistant than SEB to heat. After 24 h of incubation at 25 C, some reactivation (recovery of serological reactivity) occurred in toxins that had been inactivated by heat. If the toxin was stirred during heating, reactivation did not occur. An examination of the reactivation kinetics of heat-treated SEC showed that reactivation was temperature dependent. At 25 C, the incubation temperature of heat-treated crude SEC (80 C for 10 min), 100% reactivation occurred after 24 h, whereas at 4 C only slight reactivation was observed. We and others observed that heat-treated toxins initially lost more serological activity when heated at a low temperature (80 C) than at a higher temperature (100 C); in the present study we demonstrate that this is a reversible phenomenon.

Thermal Inactivation of Staphylococcal Enterotoxins B and C

Characteristics of the DNA from Lymantria dispar nuclear polyhedrosis virus.

Characterization of the DNA from four heliothis nuclear polyhedrosis virus isolates

Thermal Inactivation ofStaphylococcal Enterotoxins B andC

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Thermal Inactivation of Staphylococcal Enterotoxins B and C

Characteristics of the DNA from Lymantria dispar nuclear polyhedrosis virus.

Characterization of the DNA from four heliothis nuclear polyhedrosis virus isolates

Thermal Inactivation ofStaphylococcal Enterotoxins B andC