Fatal herpes simplex virus hepatitis following neoadjuvant chemoradiotherapy and anterior resection for rectal cancer.

We describe the case of a young patient who contracted fatal herpes simplex virus hepatitis following neoadjuvant chemoradiotherapy and anterior resection for rectal cancer. The rarity and non-specific presentation of this treatable disease, which masqueraded as the sequelae of postoperative sepsis, resulted in a diagnosis following death. Features that should prompt inclusion of herpes simplex virus hepatitis in the differential diagnoses are suggested and the case is a reminder of how neoadjuvant therapy may subtly alter a patient's immunocompetency.

KRAS and BRAF mutations in Nigerian colorectal cancers.

PURPOSE: Activation of the KRAS oncogene is implicated in colorectal carcinogenesis and mutations have been reported in 30-50% of cases. BRAF mutation, though less common, is also reported and importantly associated with shorter progression-free interval. This study aims to determine the KRAS and BRAF mutation statuses of Nigerian colorectal cancers (CRC). METHODS: Mutation analysis was carried out on archival paraffin-embedded blocks of CRC tissues. KRAS codons 12, 13 and 61 and BRAF V600E were assessed by pyrosequencing after DNA extraction from 200 cases at the Leeds Institute of Molecular Medicine, St. James's University Hospital, UK. Mutation rates and the spectra were determined. RESULTS: Pyrosequencing was successful in 112 of 200 cases. KRAS mutation in codons 12 and 13 was demonstrated in 23 of 112 cases (21%); none in codon 61. BRAF mutation in codon 600 was demonstrated in 4.5%. CONCLUSION: This study shows that 21% of Nigerian CRC patients carry a KRAS mutation; half the rate in Caucasians; and that BRAF mutation also occurs in Nigerian CRC cancers.

Phagocyte-derived reactive oxygen species do not influence the progression of murine blood-stage malaria infections.

Phagocyte-derived reactive oxygen species have been implicated in the clearance of malaria infections. We investigated the progression of five different strains of murine malaria in gp91(phox-/-) mice, which lack a functional NADPH oxidase and thus the ability to produce phagocyte-derived reactive oxygen species. We found that the absence of functional NADPH oxidase in the gene knockout mice had no effect on the parasitemia or total parasite burden in mice infected with either resolving (Plasmodium yoelii and Plasmodium chabaudi K562) or fatal (Plasmodium berghei ANKA, Plasmodium berghei K173 and Plasmodium vinckei vinckei) strains of malaria. This lack of effect was apparent in both primary and secondary infections with P. yoelii and P. chabaudi. There was also no difference in the presentation of clinical or pathological signs between the gp91(phox-/-) or wild-type strains of mice infected with malaria. Progression of P. berghei ANKA and P. berghei K173 infections was unchanged in glutathione peroxidase-1 gene knockout mice compared to their wild-type counterparts. The rates of parasitemia progression in gp91(phox-/-) mice and wild-type mice were not significantly different when they were treated with l-N(G)-methylarginine, an inhibitor of nitric oxide synthase. These results suggest that phagocyte-derived reactive oxygen species are not crucial for the clearance of malaria parasites, at least in murine models.

Is ischemia involved in the pathogenesis of murine cerebral malaria?

Sequestration of parasitized erythrocytes in the central nervous system microcirculation and increased cerebrospinal fluid lactate are prominent features of cerebral malaria (CM), suggesting that sequestration causes mechanical obstruction and ischemia. To examine the potential role of ischemia in the pathogenesis of CM, Plasmodium berghei ANKA (PbA) infection in CBA mice was compared to infection with P. berghei K173 (PbK) which does not cause CM (the non-CM model, NCM). Cerebral metabolite pools were measured by (1)H nuclear magnetic resonance spectroscopy during PbA and PbK infections. Lactate and alanine concentrations increased significantly at the terminal stage of CM, but not in NCM mice at any stage. These changes did not correlate with parasitemia. Brain NAD/NADH ratio was unchanged in CM and NCM mice at any time studied, but the total NAD pool size decreased significantly in the CM mice on day 7 after inoculation. Brain levels of glutamine and several essential amino acids were increased significantly in CM mice. There was a significant linear correlation between the time elapsed after infection and small, progressive decreases in the cell density/cell viability markers glycerophosphocholine and N-acetylaspartate in CM, indicative of gradual loss of cell viability. The metabolite changes followed a different pattern, with a sudden significant alteration in the levels of lactate, alanine, and glutamine at the time of terminal CM. In NCM, there were significant decreases with time of glutamate, the osmolyte myo-inositol, and glycerophosphocholine. These results are consistent with an ischemic change in the metabolic pattern of the brain in CM mice, whereas in NCM mice the changes were more consistent with hypoxia without vascular obstruction. Mild obstructive ischemia is a likely cause of the metabolic changes during CM, but a role for immune cell effector molecules cannot be ruled out.

The role of cerebral oedema in the pathogenesis of cerebral malaria.

It has been suggested that sequestration of parasitized red blood cells might contribute to the pathogenesis of cerebral malaria (CM), by hypoxia causing either: (i) compensatory vasodilatation with a resultant increase in the brain volume; or (ii) enhancing cytokine-induced nitric oxide (NO) production via induction of inducible NO synthase (iNOS). Available evidence suggests that cerebral oedema is the initiating and probably the most important factor in the pathogenesis of murine CM. The relevance of this model in the study of the pathogenesis of CM has been questioned. However, a closer look at published reports on both human and murine CM, in this review, suggests that the pathogenesis of the murine model of CM might reflect more closely the CM seen in African children than that seen in Asian adults. It is also proposed that the role of iNOS induction during CM is protective: that the primary purpose of iNOS induction is to inhibit the side effects of brain indoleamine 2,3-dioxygenase (IDO) induction and quinolinic acid accumulation during hypoxia.

Are reactive oxygen species involved in the pathogenesis of murine cerebral malaria?

To investigate the involvement of oxidative tissue damage in the pathogenesis of murine cerebral malaria (CM), brain levels of protein carbonyls, 3,4-dihydroxyphenylalanine (DOPA), o-tyrosine, and dityrosine were measured during Plasmodium berghei ANKA (PbA) and P. berghei K173 (PbK) infections. During PbA infection in a CM model, brain levels of the substances were similar to those in uninfected mice. The role of phagocyte-derived reactive oxygen species in the pathogenesis of CM was examined in gp91phox gene knockout mice. The course of CM in these mice was the same as in their wild type counterparts. To examine whether superoxide production in the central nervous system could have occurred via increased xanthine oxidase activity, brain concentrations of urate were measured in CM mice and in mice infected with PbK (which does not cause CM). Brain urate concentration increased significantly in both groups of mice, suggesting that purine breakdown is not specific to CM. These results indicate that reactive oxygen species probably do not contribute to the pathogenesis of murine CM.

Dramatic changes in oxidative tryptophan metabolism along the kynurenine pathway in experimental cerebral and noncerebral malaria.

The pathogenesis of human cerebral malaria (CM) remains unresolved. In the most widely used murine model of CM, the presence of T lymphocytes and/or interferon (IFN)-gamma is a prerequisite. IFN-gamma is the key inducer of indoleamine 2,3-dioxygenase (IDO), which is the catalyst of the first, and rate-limiting, step in the metabolism of tryptophan (Trp) along the kynurenine (Kyn) pathway. Quinolinic acid (QA), a product of this pathway, is a neuro-excitotoxin, like glutamic acid (Glu) and aspartic acid (Asp). Kynurenic acid (KA), also produced from the Kyn pathway, antagonizes the neuro-excitotoxic effects of QA, Glu, and Asp. We therefore examined the possible roles of IDO, metabolites of the Kyn pathway, Glu, and Asp in the pathogenesis of fatal murine CM. Plasmodium berghei ANKA infection was studied on days 6 and 7 post-inoculation (p.i.), at which time the mice exhibited cerebral symptoms such as convulsions, ataxia, coma, and a positive Wooly/White sign and died within 24 hours. A model for noncerebral malaria (NCM), P. berghei K173 infection, was also studied on days 6 and 7 and 13 to 17 p.i. to examine whether any changes were a general response to malaria infection. Biochemical analyses were done by high-pressure liquid chromatography and gas chromatography/mass spectrometry/mass spectrometry (GC/MS/MS). IDO activity was low or absent in the brains of uninfected mice and NCM mice (days 6 and 7 p.i.) and was induced strongly in the brains of fatal murine CM mice (days 6 and 7 p.i.) and NCM animals (days 13 to 17 p.i.). This induction was inhibited greatly by administration of dexamethasone, a treatment that also prevented CM symptoms and death. Furthermore, IDO induction was absent in IFN-gamma gene knockout mice, which were also resistant to CM. Brain concentrations of Kyn, 3-hydroxykynurenine, and the neuro-excitotoxin QA were significantly increased in both CM mice on days 6 and 7 p.i. and NCM mice on days 13 to 17 p.i., whereas an increase in the ratio of brain QA to KA occurred only in the CM mice at the time they were exhibiting cerebral symptoms. Brain concentrations of Glu and Asp were significantly decreased in CM and NCM mice (days 13 to 17 p.i.). The results imply that neuro-excitation induced by QA may contribute to the convulsions and neuro-excitatory signs observed in CM.