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By Carol A. Kemper, MD
Source: Khalili K, et al. Lancet 1999; 353:1152-1153.
While JC virus commonly causes an asymptomatic infection in humans, often early in life, reactivation of viral replication in the neurological tissues of immunosuppressed persons, including those with HIV infection, can result in a progressively disabling and fatal demyelinating illness called progressive multifocal leukoencephalopathy (PML). Recent experiments in transgenic mice suggest that the gene responsible for a regulatory protein of viral replication, called T-antigen, may have oncogenic potential (Krynska B, et al. Oncogene 1999;18:39-46). This led Khalili and colleagues to examine the prevalence of JC virus DNA in tumor tissue from 11 pediatric patients with medulloblastomas.
Ten children (91%) had evidence of JC VP1 DNA in tumor tissue and 73% had specific DNA sequences corresponding to the T-antigen of the virus. Using immunohistochemical techniques, JC virus T-antigen was demonstrated within a majority of tumor nuclei, and about 5-20% of tumor cells stained positively for antibody to T antigen. Specimens of brain tissue from five age-matched healthy controls were negative.
Interestingly, the structural organization of the regulatory gene appears to differ between that of the prototype Mad-1 variant of JC virus, which is responsible for the demyelination of neurological tissues, and the JCV (CY) strain commonly isolated in the urine of PML and non-PML individuals. These findings suggest that, in addition to its demyelinating effects in immunosuppressed patients, certain variants of JC virus may have tumorigenic potential.
a. JC virus commonly causes an asymptomatic infection.
b. Infection with JC virus often occurs at a young age.
c. JC virus is the cause of progressive multifocal leukoencephalopathy.
d. JC virus is associated with glioblastoma multiforme.
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Source: Roux V, Raoult D. J Clin Microbiol 1999;37:596-599.
Roux and Raoult used PCR assays to assess the prevalence of human body louse infection by three different human disease-causing bacteria, including Bartonella quintana (the agent of trench fever), Borrelia recurrentis (an agent of relapsing fever), and Rickettsia prowazekii (the agent of epidemic typhus). Samples of body lice were collected from 599 subjects residing in six different countries, including refugees in Congo and Burundi, homeless people in Marseille, Moscow, and Zimbabwe, and rural residents of Peru.
Bartonella was found in 9.7% of all lice sampled, varying in frequency from 1.4% obtained from rural Peruvians to as high as 16.7% from Zimbabwean homeless (see also Kemper CA. Infect Dis Alert 1999;15:120). In contrast, R. prowazekii was only found in refugees from Burundi, where an epidemic of typhus was occurring. Nearly one-third of the specimens collected during the epidemic were positive for R. prowazekii, but the organism was not identified in any of the 91 post-epidemic specimens. None of the specimens from any of the groups was positive for B. recurrentis. Much the same as our Public Health Department presently uses PCR to monitor the prevalence of Borrelia burgdorferi in Ixodes pacificus ticks in our area, PCR assay could be a valuable epidemiological and diagnostic tool for tracking endemic disease in body lice in high-risk populations.
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Source: Ramos A, et al. Emerg Infect Dis 1999;5:65-74.
Dual and even triple co-infection with different subtypes and clades of HIV-1 have been documented in several countries around the globe, including Africa and South America. The potential for infection with multiple serotypes and recombinant strains creating mosaics may significantly affect efforts to develop effective HIV vaccine strategies. For example, in Brazil, which has been selected as a World Health Organization (WHO) field site for HIV vaccine testing, four subtypes (B, F, C, and D) are present in the population, although only the first two are predominant.
Ramos and colleagues evaluated the HIV strains found in 79 patients in 1994, all of whom were participants in pre-vaccine selection studies in Rio de Janeiro. Using combinations of various molecular and sequencing techniques, three dual (3.8%) and six recombinant (7.6%) infections were identified. Each of the recombinant infections was a unique B/F mosaic, whereas the dual infections were different combinations of two of the circulating subtypes B, F, and D.
Based on patterns of infection found five years ago in a major urban area in South America, mixed infections with different subtypes of HIV, including combinations of less common strains found circulating at low levels in the population, were found in up to 11.4% of patients. This finding may have profound affects on worldwide vaccine developmental efforts.