Increased rainfall is associated with increased risk for legionellosis.

Legionnaires' disease (LD) is caused by Legionella species, most of which live in water. The Mid-Atlantic region experienced a sharp rise in LD in 2003 coinciding with a period of record-breaking rainfall. To investigate a possible relationship, we analysed the association between monthly legionellosis incidence and monthly rainfall totals from January 1990 to December 2003 in five Mid-Atlantic states. Using negative binomial model a 1-cm increase in rainfall was associated with a 2.6% (RR 1.026, 95% CI 1.012-1.040) increase in legionellosis incidence. The average monthly rainfall from May to September 1990-2002 was 10.4 cm compared to 15.7 cm from May to September 2003. This change in rainfall corresponds to an increased risk for legionellosis of approximately 14.6% (RR 1.146, 95% CI 1.067-1.231). Legionellosis incidence increased during periods of increased rainfall; identification of mechanisms that increase exposure and transmission of Legionella during rainfall might lead to opportunities for prevention.

The transneuronal spread phenotype of herpes simplex virus type 1 infection of the mouse hind footpad.

The mouse hind footpad inoculation model has served as a standard laboratory system for the study of the neuropathogenesis of herpes simplex virus type 1 (HSV-1) infection. The temporal and spatial distribution of viral antigen, known as the transneuronal spread phenotype, has not previously been described; nor is it understood why mice develop paralysis in an infection that involves sensory nerves. The HSV-as-transneuronal-tracer experimental paradigm was used to define the transneuronal spread of HSV-1 in this model. A new decalcification technique and standard immunocytochemical staining of HSV-1 antigens enabled a detailed analysis of the time-space distribution of HSV-1 in the intact spinal column. Mice were examined on days 3, 4, 5, and 6 postinoculation (p.i.) of a lethal dose of wild-type HSV-1 strain 17 syn+. Viral antigen was traced retrograde into first-order neurons in dorsal root ganglia on day 3 p.i., to the dorsal spinal roots on days 4 and 5 p.i., and to second- and third-order neurons within sensory regions of the spinal cord on days 5 and 6 p.i. HSV-1 antigen distribution was localized to the somatotopic representation of the footpad dermatome within the dorsal root ganglia and spinal cord. Antigen was found in the spinal cord gray and white matter sensory neuronal circuits of nociception (the spinothalamic tract) and proprioception (the dorsal spinocerebellar tract and gracile fasciculus). Within the brain stems and brains of three paralyzed animals examined late in infection (days 5 and 6 p.i.), HSV antigen was restricted to the nucleus subcoeruleus region bilaterally. Since motor neurons were not directly involved, we postulate that hindlimb paralysis may have resulted from intense involvement of the posterior column (gracile fasciculus) in the thoracolumbar spinal cord, a region known to contain the corticospinal tract in rodents.

Viral upper respiratory infections.

Viral upper respiratory infections, otherwise known as the common cold, are the most common diseases among humans. The self-limited, and often self-diagnosed, acute mild catarrhal illness is usually a nasopharyngitis of 5 to 7 days duration. The major virus groups causing colds are the Picornaviridae, Coronaviridae, Paramyxoviridae, Orthomyxoviridae, and Adenoviridae families. This review will emphasize the basic virology, pathogenesis, and immunology of these infections, and will conclude with present-day and future modalities for treatment and prevention.

Two novel single amino acid syncytial mutations in the carboxy terminus of glycoprotein B of herpes simplex virus type 1 confer a unique pathogenic phenotype.

We previously reported on a variant of the herpes simplex type 1 (HSV-1) strain 17 syn+, named 17 hep syn, capable of forming giant polykaryocytes (syncytia) in tissue culture and which induced a striking alteration in the pathogenesis of infection in vivo. Following footpad inoculation of mice, 17 hep syn infection resulted in a marked clinicopathologic acute inflammatory response of the inoculated limb and mice died without antecedant limb paralysis typical of the wild-type 17 syn+ infection. The syncytial and pathogenic phenotypes were mapped to a cloned 670-base pair Kpnl-Pstl (0.345-0.351 map units) DNA fragment encoding the carboxy terminal portion of the glycoprotein B (gB). In this report, we focus on the genetics of the region of the 17 hep syn gB gene that conferred both the syncytial and pathogenic phenotypes to 17 syn+. Five 17 syn+ x 17 hep syn syncytial recombinant viruses, R1-R5, generated in marker transfer experiments with cloned 17 hep syn fragments containing gB sequences, produced 17 hep syn-like disease in mice. Sequence analysis of the Kpnl-Pstl fragment of 17 hep syn revealed a single base pair change when compared to the 17 syn+ sequence, predicting an alanine (GCC codon) to valine (GTC codon) amino acid substitution at residue 825 of the mature gB protein, plus loss of an Ncol restriction endonuclease site. Southern blot analysis of Ncol digests of viral DNAs showed that all of the recombinants except R4 contained the same mutation as 17 hep syn. The syncytial phenotype of R4 was, however, mapped to the same region as 17 hep syn and the other recombinants, and the DNA sequence of the 670-base pair Kpnl-Pstl clone of R4 revealed another single base pair change predicting a leucine (CTC codon) to histadine (CAC codon) amino acid substitution at residue 787 of gB. The mutant gBs did not effect viral growth as all of the recombinant viruses had similar in vitro replication kinetics to wild-type HSV-1. These data provide direct evidence that at least two mutations can exist in the carboxy terminus of gB of HSV-1 that promote syncytial formation in vitro and effect pathogenesis in vivo.

Altered pathogenesis in herpes simplex virus type 1 infection due to a syncytial mutation mapping to the carboxy terminus of glycoprotein B.

A syncytial (syn) variant of herpes simplex virus type 1 strain 17 syn+ was selected by serial passage in heparin, a glycosaminoglycan which potently inhibits herpes simplex virus infectivity. This virus, 17 hep syn, is sixfold more heparin resistant than its parent. By using marker transfer techniques, its syn phenotype, but not heparin resistance, was mapped first to the BamHI G fragment (0.343 to 0.415 map units) and then to a 670-bp KpnI-PstI subclone (0.345 to 0.351 map units) encoding the carboxy terminus of glycoprotein B (gB). Three cloned syncytial recombinants were generated from cotransfections of 17 syn+ with either 17 hep syn BamHI-G or the 670-bp subclone. After footpad inoculation of mice, 17 hep syn was as virulent as its parent, despite reaching lower titers in feet, sciatic nerves, dorsal root ganglia, spinal cords, and brains. Animals infected with 17 hep syn or the gB recombinant viruses developed a unique pattern of disease that was strikingly different than that seen with wild-type virus: severe inflammation and edema of the inoculated limb and death without antecedent paralysis. Histopathologic examination revealed limitation of spinal involvement by 17 hep syn to the dorsal aspect of the cord and decreased virus-induced damage in the central nervous system. The genetically unrelated syn variant MP, in contrast, was avirulent and did not cause severe local inflammation. After intracerebral inoculation, 17 hep syn was highly virulent and replicated to high titers in the brain. Yet, unlike the parental virus, it resulted in an altered distribution of herpes simplex virus antigens, which were limited to the ependymal and subependymal regions surrounding the lateral ventricles. Despite their syncytial phenotype and pathogenic properties, the recombinant viruses, unlike 17 hep syn, were not heparin resistant. We conclude that a transferable alteration in the 670-bp carboxy-terminal portion of the glycoprotein gB gene of 17 hep syn results in both its syncytial phenotype and the unique pattern of disease that it causes but does not result in heparin resistance. These observations provide direct biological evidence for an important role for herpes simplex virus gB in pathogenic events both at the peripheral site of infection and within the nervous system.

Treatment of resistant herpes simplex virus with continuous-infusion acyclovir.

Two patients with acquired immunodeficiency syndrome who developed severe ulcerative proctitis caused by herpes simplex virus type 2 that was resistant to acyclovir were successfully treated with 6 weeks of high-dose, continuous-infusion acyclovir sodium (1.5 to 2.0 mg/kg per hour). Viruses cultured from the lesions were resistant to acyclovir in vitro after the patients had received prolonged therapy with oral and intravenous acyclovir in traditional divided doses. Investigation into the mechanism of the acyclovir resistance revealed changes in the thymidine-kinase activity of both isolates. This viral enzyme phosphorylates acyclovir and is necessary for drug activation. The first patient's isolate was deficient of all thymidine-kinase activity, while the second patient's isolate had a thymidine kinase with altered substrate specificity for acyclovir. The continuous infusion was safe, well tolerated, and done in an outpatient setting with weekly clinic visits and monitoring of creatinine and acyclovir levels.

Inactivation of Naegleria gruberi cysts by chlorinated cyanurates.

The resistance of Naegleria gruberi cysts to chlorine in the presence of cyanuric acid was compared at pH 5 and 7. An amperometric membrane electrode was used to measure HOCl concentrations independently of the chlorinated cyanurate species, thus permitting an analysis of the role of free chlorine versus chlorinated cyanurates in cyst inactivation. In the presence of cyanuric acid, the products of the HOCl residual and the contact time required for 99% cyst inactivation were 8.5 mg . min/liter and 13.9 mg . min/liter at pH 5 and 7, respectively. The Watson's Law coefficients of dilution (n) were 1.3 and 1.6 at pH 5 and 7, respectively. The results strongly suggest that HOCl is the predominant cysticide with no measurable cysticidal effect of the chlorinated cyanurate species.

Bone marrow hemosiderin does not always reflect body iron stores.

Absence of hemosiderin from the bone marrow is sometimes encountered in patients who are not iron deficient. Two cases of autoimmune hemolytic anemia are described in which there was little or no hemosiderin in the marrow but large amounts in the spleen, which had been the major site of accelerated RBC destruction.