Is there a relationship between the detection of human herpesvirus 8 and Epstein-Barr virus in Waldeyer's ring tissues?

Objective: Human herpesvirus 8 (HHV-8) and Epstein-Barr virus (EBV) are human pathogens associated to a number of neoplasms, including tumors of the Waldeyer's ring. Both viruses have been previously detected by in situ methods in tonsils and adenoids from children. HHV-8 was found in 6.8% of the cases and EBV in about one third of the cases. As they belong to the same gamma-herpesvirus subfamily and share some biological characteristics, it is of medical interest to further explore their possible relationship in the Waldeyer's ring, an issue not yet addressed in the specialized literature. The purpose of the present study is to compare the presence of EBV by in situ hybridization (ISH) in tonsils and adenoids from children up to 14 years of age in cases previously shown to be positive and negative for HHV-8. Methods: Paraffin wax-embedded sections consisting of 38 tonsils and two adenoids from 40 patients were analyzed. HHV-8 was detected by ISH, using the T1-1 probe for the viral mRNA. EBV was also detected by ISH, using the EBER probe. Both probes and the detection systems were provided by Novocastra. Results: HHV-8 was detected in 19 tonsils and one adenoid. The other 19 tonsils and one adenoid taken from the HHV-8-negative group were selected by pairing age and gender of patients with the HHV-8-positive group. In both groups EBV was detected in 13 cases and was negative in other 7. Conclusion: Although both viruses are related in many aspects, some biological and epidemiological features differ. This is reflected in the present results, as EBV is similarly detected in the groups negative and positive for HHV-8, favoring different mechanisms of spread. (C) 2006 Elsevier Ireland Ltd. All rights reserved.70111923192

Elucidating in vitro and in vivo phenotypic behaviour of L. infantum/L. major natural hybrids

The clinical manifestation and course of Leishmania infections depend on factors such as species, virulence and host-immunity. Although trypanosomatids are considered to have clonal propagation, genetic hybridization has produced successful natural hybrid lineages. Hybrids displaying strong selective advantages may have an impact on pathogenesis and the eco-epidemiology of leishmaniasis. Thus, characterization of phenotypic properties of Leishmania hybrids could bring significant insight into the biology, infectivity, pathogenicity and transmission dynamics of these atypical strains. The present study focuses on phenotypic features and survival capacity of Leishmania infantum/Leishmania major hybrid isolates as compared with representative putative parental species, L. infantum and L. major. In vitro assays (growth kinetics, susceptibility to different conditions) and in vivo infection (parasite detection and histopathological alterations) showed that hybrids present higher growth capacity and decreased susceptibility to reactive oxygen species. Furthermore, evaluation of infected spleen tissue suggests that hybrids induce a stronger immune reaction than their putative parents, leading to the development of white pulp hyperplasia in B-lymphocyte compartments. Overall, these hybrids have shown high plasticity in terms of their general behaviour within the different phenotypic parameters, suggesting that they might have acquired genetic features conferring different mechanisms to evade host cells

Elucidating in vitro and in vivo phenotypic behaviour of L. infantum/L. major natural hybrids

The clinical manifestation and course of Leishmania infections depend on factors such as species, virulence and host-immunity. Although trypanosomatids are considered to have clonal propagation, genetic hybridization has produced successful natural hybrid lineages. Hybrids displaying strong selective advantages may have an impact on pathogenesis and the eco-epidemiology of leishmaniasis. Thus, characterization of phenotypic properties of Leishmania hybrids could bring significant insight into the biology, infectivity, pathogenicity and transmission dynamics of these atypical strains. The present study focuses on phenotypic features and survival capacity of Leishmania infantum/Leishmania major hybrid isolates as compared with representative putative parental species, L. infantum and L. major. In vitro assays (growth kinetics, susceptibility to different conditions) and in vivo infection (parasite detection and histopathological alterations) showed that hybrids present higher growth capacity and decreased susceptibility to reactive oxygen species. Furthermore, evaluation of infected spleen tissue suggests that hybrids induce a stronger immune reaction than their putative parents, leading to the development of white pulp hyperplasia in B-lymphocyte compartments. Overall, these hybrids have shown high plasticity in terms of their general behaviour within the different phenotypic parameters, suggesting that they might have acquired genetic features conferring different mechanisms to evade host cells