ApoE4 is more efficient than E3 in brain access by herpes simplex virus type 1

Bovine herpesvirus 1 infection and infectious bovine rhinotracheitis

Bovine herpesvirus 1 (BoHV-1), classified as an alphaherpesvirus, is a major pathogen of cattle. Primary infection is accompanied by various clinical manifestations such as infectious bovine rhinotracheitis, abortion, infectious pustular vulvovaginitis, and systemic infection in neonates. When animals survive, a life-long latent infection is established in nervous sensory ganglia. Several reactivation stimuli can lead to viral re-excretion, which is responsible for the maintenance of BoHV-1 within a cattle herd. This paper focuses on an updated pathogenesis based on a molecular characterization of BoHV-1 and the description of the virus cycle. Special emphasis is accorded to the impact of the latency and reactivation cycle on the epidemiology and the control of BoHV-1. Several European countries have initiated BoHV-1 eradication schemes because of the significant losses incurred by disease and trading restrictions. The vaccines used against BoHV-1 are described in this context where the differentiation of infected from vaccinated animals is of critical importance to achieve BoHV-1 eradication.

Apolipoprotein E alleles can contribute to the pathogenesis of numerous clinical conditions including HSV-1 corneal disease

Apolipoprotein E (ApoE) alleles have been reported to affect the clinical outcome of numerous cardiovascular, neurodegenerative, and viral infectious diseases, including atherosclerosis, Alzheimer's disease (AD), hepatitis C, and HIV. The major alleles of ApoE are 2, 3, and 4. ApoE genotypes have been hypothesized to regulate many biological functions, resulting in significant changes in the onset and/or outcome (severity and duration) of several clinical conditions. Based on genetic analyses in human and animal studies using knockout (ApoE -/-) mice and mice transgenic for human 3 and 4, we present evidence that strongly suggests that the ApoE alleles can regulate the pathogenesis of ocular herpes simplex virus type 1 (HSV-1) infections. This review will summarize the major studies that support this hypothesis. Significant gender based differences in HSV-1 pathogenesis have also been reported, suggesting that hormonal regulation combined with ApoE genotype plays a significant role in HSV-1 pathogenesis. Identification of specific mechanisms in ocular HSV-1 infections related to the ApoE alleles and gender could lead to therapeutic intervention based on the properties of the apoE isoforms. While many clinical investigations have been reported and, to a lesser extent, transgenic mouse studies have been conducted, no specific mechanisms of how ApoE induces or alters clinical disease are known.

No association of apolipoprotein E epsilon4 genotype with faster progression or less recovery of relapses in a Spanish cohort of multiple sclerosis

BACKGROUND

Recent data have suggested a faster deterioration of multiple sclerosis (MS) patients who harbour the epsilon4 allele of the apolipoprotein E (APOE) gene. We investigate the relationship of APOE genotypes with disease severity and clinical recovery of relapses in a MS population of the north of Spain.

METHODS

One hundred and thirty-three patients with clinically defined MS were studied. Disease course (relapsing versus progressive), age of onset, duration of the disease and disability measured by the Expanded Disability Status Scale (EDSS) were recorded. Worsening was measured by the Progression Index (PI) and by EDSS 4 and 6 latencies. In 79 patients with relapsing-remitting (RR) MS the degree of clinical recovery of relapses (total versus partial) was assessed.

RESULTS

The frequency of the APOE epsilon4 allele in our patients was similar to that found in other southern European populations. APOE epsilon4 patients did not have a faster progression as assessed by PI and EDSS 4 and 6 latencies. Among 79 patients with RRMS there were no significant differences in the degree of recovery of relapses.

CONCLUSIONS

In this MS population, APOE epsilon4 polymorphism is not associated with a more severe clinical course and does not appear to influence recovery of exacerbations.

A TAP2 genotype associated with Alzheimer's disease in APOE4 carriers

Sporadic Alzheimer's disease (AD) appears to be the consequence of the interaction between combinations of genes and environmental factors. Binding with the transporter associated with antigen processing (TAP) is thought to be the main way in which herpes simplex virus type 1 (HSV-1) evades immune surveillance. Several TAP gene polymorphisms were examined and a TAP2 SNP (rs241448) associated with AD found in two independent case-control samples, especially in carriers of the APOE4 allele. These findings are consistent with the hypothesis that human genetic variants facilitating the access of HSV-1 to the brain might result in susceptibility to AD.

Non-invasive bioluminescence imaging for monitoring herpes simplex virus type 1 hematogenous infection

Traditional studies on viral neuroinvasiveness and pathogenesis have generally relied on murine models that require the sacrifice of infected animals to determine viral distributions and titers. The present paper reports the use of in vivo bioluminescence imaging to monitor the replication and tropism of KOS strain HSV-1 viruses expressing the firefly luciferase reporter protein in hematogenously infected mice. Following intraperitoneal injection, a comparison was made between real-time PCR determinations of HSV-1 DNA concentrations (requiring the sacrifice of the experimental animals) and in vivo bioluminescence emissions in living animals. For further comparison, in vitro light emission was also measured in the ovaries and adrenal glands of sacrificed mice. After infection, HSV-1 spread preferentially to the ovaries and adrenal glands (these organs showed the highest virus levels). Both the PCR and bioluminescence methods detected low viral loads in the nervous system, where the virus was restricted to the spinal cord. The concentrations of viral DNA measured correlated with the magnitude of bioluminescence in vivo, and with the photon flux determined by the in vitro luciferase enzyme assay. The results show that bioluminescence imaging can be used for non-invasive, real-time monitoring of HSV-1 hematogenous infection in living mice, but that coupling this methodology with conventional techniques aids in the characterization of the infection.

Hematogenous vertical transmission of herpes simplex virus type 1 in mice

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that causes severe disease and death in newborn humans but, to date, it remains unclear how neonatal infection occurs. We show here that the vertical transmission of HSV-1 in mice is mainly hematogenous and involves the colonization of the neonate central nervous system (CNS). HSV-1 DNA was mainly detected in the blood and CNS of the offspring born to latently infected mothers; no significant differences were seen between the viral DNA concentrations in the blood of these mothers and their female progeny (either neonate or adult). The administration of acyclovir during gestation reduced or eliminated both the maternal and the neonatal viral DNA in the blood. Embryo transfer was performed to ensure (as far as possible) that only vertical hematogenous infection took place. Immunohistochemical analysis detected viral proteins in the encephalon of the offspring. Immunofluorescence studies provided immunoreactive evidence of HSV-1 proteins in the neurons of the hippocampus and showed that these viruses can molecularly reactivate after hyperthermia. Neonatal HSV-1 infection therefore appears to be mainly caused by hematogenous vertical transmission, and the viruses that colonize the offspring CNS are capable of molecular reactivation after a period of latency.

Senile plaques in Alzheimer's diseased brains: possible association of beta-amyloid with herpes simplex virus type 1 (HSV-1) L-particles

The characteristic insoluble, senile (neuritic) plaques found extracellularly in brains of patients with Alzheimer's disease (AD) contain the fibrillar form of beta-amyloid (Abeta42). A substantial proportion of autopsied elderly brains have demonstrated DNA evidence of herpes simplex virus type 1 (HSV-1) infiltration. HSV-1-infected cells produce significant quantities of non-infectious, non-DNA-containing light particles (L-particles) comprised of viral envelope and tegument proteins. HSV-induced L-particles can be exocytosed out of their host cells. This report advances the hypothesis that (1) Abeta binds to L-particles; (2) Abeta permeabilizes L-particles, destroying the integrity of the envelope and allowing the contained tegument proteins to spill into the extracellular space; and (3) these events are followed by a conformational shift of Abeta into its fibrillar form, physically trapping the L-particle-derived substances and resulting in the plaques characteristic of AD. These hypotheses are supported by reports of biomolecular changes and pathophysiologies which have been simultaneously observed in both AD- and HSV-infected brains.

Interaction of herpesviridae, APOE gene, and education in cognitive impairment

While high age, low level of education and APOE epsilon4 allele are known to predict dementia, there is recent data suggesting that certain viruses and subtypes of APOE epsilon3 could be involved, too. We investigated these relationships in a home-dwelling cohort of 357 elderly people with various cardiovascular diseases (DEBATE study). MMSE score below 24 was used to define cognitive impairment (n = 58). When adjusted for age and the presence of diabetes, multivariate analysis demonstrated maximally increased risk of cognitive impairment in association with a combination of three factors: seropositivity for herpesviridae, presence of APOE epsilon4, and low education (risk ratio 6.1, 95% CI 2.4-15.2). In the subcohort of APOE3/3 individuals (n = 216) homozygosity for the -219G epsilon3 haplotype showed a similar association (risk ratio 8.8, 95% CI 2.6-29.8). These results demonstrate an interaction of specific genetic (APOE) and environmental (education and herpesviridae) risk factors in the development of cognitive impairment and indicate that not only the epsilon4 allele of APOE but also the epsilon3 haplotype is a risk factor for dementia.

Herpes simplex virus type 1 infection via the bloodstream with apolipoprotein E dependence in the gonads is influenced by gender

Herpes simplex virus type 1 (HSV-1) causes disease in humans and animals. Infection usually occurs via the neural route and possibly occurs via the hematogenous route. The latter, however, is the main route by which immunosuppressed individuals and neonates are infected. Gender-dependent differences in the incidence and severity of some viral infections have been reported. To detect differences between the sexes with respect to HSV-1 colonization and disease, the characteristics of both acute and latent infections in hematogenously infected male and female mice were compared. In acute infection, the female mice had a poorer outcome: HSV-1 colonization was more effective, especially in the gonads and brain. In the encephalon, the midbrain had the highest viral load. In latent infection, brain viral loads were not significantly different with respect to sex. Significant differences were seen, however, in the blood and trigeminal ganglia: HSV-1 seroprevalence was observed in females, with no virus detected in males. In brain dissections, only the cerebral cortex of the females had viral loads statistically higher than those observed in the males. The spread of the virus to several organs of interest during acute infection was examined immunohistochemically. Female mice showed greater viral immunostaining, especially in the adrenal cortex, gonads, and midbrain. In male mice, HSV-1 was detected predominantly in the adrenal cortex. It was also found that apolipoprotein E promotes virus colonization of the ovaries, the APOE gene dose being directly related to viral invasiveness.

Infiltration of the brain by pathogens causes Alzheimer's disease

Despite very numerous studies on Alzheimer's disease (AD), especially on amyloid plaques and neurofibrillary tangles, little information has been obtained thus on the causes of the disease. Evidence is described here that implicates firstly herpes simplex virus type 1 (HSV1) as a strong risk factor when it is present in brain of carriers of the type 4 allele of the gene for apolipoprotein E (APOE-4). Indirect support comes from studies indicating the role of APOE in several diverse diseases of known pathogen cause. A second putative risk factor is the bacterium, Chlamydia pneumoniae. This pathogen has been identified and localized in AD brain. Current studies aimed at "proof of principle" address the entry of the organism into the CNS, the neuroinflammatory response to the organism, and the role that the organism plays in triggering AD pathology. An infection-based animal model demonstrates that following intranasal inoculation of BALB/c mice with C. pneumoniae, amyloid plaques/deposits consistent with those observed in the AD brain develop, thus implicating this infection in the etiology of AD.