A new One Health Framework in Qatar for future emerging and re-emerging zoonotic diseases preparedness and response

One Health is increasingly recognized as an optimal approach to address the global risk of health threats originating at the human, animal, and ecosystem interface, and their impact. Qatar has successfully practiced One Health approach for investigation and surveillance of zoonotic diseases such as MERS-CoV, and other health threats. However, the current gaps at institution and policy level hinder the sustainment of One Health. In this paper, we have assessed the potential for implementation of One Health Framework to reinforce and sustain One Health capacities in Qatar for 2022-2027. To implement One Health Framework in the country, Qatar Joint External Evaluation (JEE) report, lessons learnt during One Health experiences on zoonotic, vector-borne, and food borne diseases were used to present an outline for multisectoral coordination. In addition, technical capacities of One Health and factors that are required to operationalize it in the country were also assessed in series of meetings and workshops held at Ministry of Public Health on March 2022. Present health care infrastructure and resources were found to be conducive for effective management and response to shared health threats as evident during MERS-CoV, despite being more event based. Regardless, the need for more sustainable capacity development was unanimously emphasized. The consensus between all relevant stakeholders and partners was that there is a need for better communication channels, policies and protocols for data sharing, and the need to invest more resources for better sustainability. The proposed framework is expected to strengthen and facilitate multilateral coordination, enhanced laboratory capacity and network, improve active surveillance and response, risk communication, community engagement, maximize applied research, and build One Health technical work force. This would enable advancement and sustainment of One Health activities to prevent and control health threats shared between humans-animals-ecosystem interface.

Loop-mediated isothermal amplification assay for rapid detection of Streptococcus agalactiae (group B streptococcus) in vaginal swabs - a proof of concept study

PURPOSE

Neonatal sepsis caused by Streptococcus agalactiae [group B streptococcus (GBS)] is a life-threatening condition, which is preventable if colonized mothers are identified and given antibiotic prophylaxis during labour. Conventional culture is time consuming and unreliable, and many available non-culture diagnostics are too complex to implement routinely at point of care. Loop-mediated isothermal amplification (LAMP) is a method that, enables the rapid and specific detection of target nucleic acid sequences in clinical materials without the requirement for extensive sample preparation.

METHODOLOGY

A prototype LAMP assay targeting GBS sip gene is described.

RESULTS

The assay was 100 % specific for GBS, with a limit of detection of 14 genome copies per reaction. The clinical utility of the LAMP assay for rapid direct molecular detection of GBS was determined by testing a total of 157 vaginal swabs with minimal sample processing using a rapid lysis solution. Compared to a reference quantitative real-time PCR assay, the direct LAMP protocol had a sensitivity and specificity of 95.4 and 100 %, respectively, with positive and negative predictive values of 100 and 98.3 %, respectively. Positive and negative likelihood ratios were infinity and 0.05, respectively. The direct LAMP method required a mean time of 45 min from the receipt of a swab to generation of a confirmed result, compared to 2 h 30 min for the reference quantitative real-time PCR test.

CONCLUSION

The direct LAMP protocol described is easy to perform, facilitating rapid and accurate detection of GBS in vaginal swabs. This test has a potential for use at point of care.

Heller's myotomy and pneumatic dilatation in the treatment of achalasia: a population-based case-control study assessing long-term quality of life

Long-term health-related quality-of-life (HRQL) outcomes have not been widely reported in the treatment of achalasia. The aims of this study were to examine long-term disease-specific and general HRQL in achalasia patients using a population-based case-control method, and to assess HRQL between treatment interventions. Manometrically diagnosed achalasia cases (n = 120) were identified and matched with controls (n = 115) using a population-based approach. Participants completed general (SF-12) and disease-specific (Achalasia Severity Questionnaire [ASQ]) HRQL questionnaires, as appropriate, in a structured interview. Mean composite scores for SF-12 (Mental Component Summary score [MCS-12] and Physical Component Summary score [PCS-12]) and ASQ were compared between cases and controls, or between intervention groups, using an independent t-test. Adjusted mean differences in HRQL scores were evaluated using a linear regression model. Achalasia cases were treated with a Heller's myotomy (n = 43), pneumatic dilatation (n = 44), or both modalities (n = 33). The median time from last treatment to HRQL assessment was 5.7 years (interquartile range 2.4-11.5). Comparing achalasia patients with controls, PCS-12 was significantly worse (40.9 vs. 44.2, P = 0.01), but MCS-12 was similar. However, both PCS-12 (39.9 vs. 44.2, P = 0.03) and MCS-12 (46.7 vs. 53.5, P = 0.004) were significantly impaired in those requiring dual treatment compared with controls. Overall however, there was no difference in adjusted HRQL between patients treated with Heller's myotomy, pneumatic dilatation or both treatment modalities. In summary, despite treatment achalasia patients have significantly worse long-term physical HRQL compared with population controls. No HRQL differences were observed between the treatment modalities to suggest a benefit of one treatment over another.

Mycoplasma hominis and Gardnerella vaginalis display a significant synergistic relationship in bacterial vaginosis

Gardnerella vaginalis plays an important role in bacterial vaginosis (BV,) while the role of genital Mollicutes is less obvious. The diagnosis of BV by use of the current Gram stain Nugent score is also suboptimal for defining the role of Mollicutes that lack a cell wall. Since bacterial load and diversity is an important prerequisite for BV, real-time quantitative polymerase chain reaction (qPCR) assays enable these to be assessed. The purpose of this study was to define the role of genital Mollicutes and potential patterns of synergy with G. vaginalis in women with BV. Vaginal swabs from 130 women categorised by Nugent score as BV (n = 28), intermediate (n = 22) and non-BV (n = 80) were tested against four qPCR TaqMan assays targeting G. vaginalis, Mycoplasma hominis, M. genitalium, Ureaplasma urealyticum and U. parvum. Statistical analyses were used to compare bacterial prevalence and load between the three groups of women. Mycoplasma hominis and G. vaginalis co-infection was significantly more common in BV (60.7 %) compared to intermediate (36.4 %) and non-BV (8.8 %) Nugent scores (p < 0.001). Significantly higher loads of M. hominis (p = 0.001) and G. vaginalis (p < 0.001) were detected in women with BV and the respective loads in M. hominis and G. vaginalis co-infections displayed a significant positive correlation (p < 0.001; r = 0.60). No significant associations were seen with the other Mollicutes. The findings strengthen the evidence of a role for M. hominis in BV and a potential synergy with G. vaginalis. This synergy could be an important trigger of the condition and sexual contact the conduit for the transmission of an otherwise commensal bacterium that could initiate it.

A comparison of the efficiency of ELISA and selected primer sets to detect Norovirus isolates in southern Ireland over a four-year period (2002-2006): variation in detection rates and evidence for continuing predominance of NoV GII.4 genotype

Norovirus (NoV) gastroenteritis occurs in all age groups and is the most common cause of gastroenteritis in the community. However, detection methods and rates vary widely, and few data are available to compare these, particularly in Ireland. Detection of noroviruses through antigen and molecular-based strategies was carried out on 135 suspected NoV-positive samples, collected over the course of three NoV outbreaks, from 2002 to 2006, in the southern region of Ireland. A commercially available ELISA and a panel of six primer sets were evaluated to determine their suitability for NoV detection in Irish clinical samples. The key findings of this study were the detection of both GGI and GGII noroviruses by ELISA, but the detection of only GGII noroviruses by RT-PCR. In addition to this, a variation in the levels of detection from 9.4 % to 17.3 % was observed for conventional PCR assays, while a detection rate of 46.3 % was observed for the real-time PCR assay. A proportion (17.8 %) of samples were found to be negative by all detection strategies, suggesting the possibility of reporting false positives for these samples or low-copy positives that do not often repeat. Sequencing information from selected samples also revealed nucleotide polymorphisms, compromising efficient primer binding in the case of one primer pairing. Phylogenetic analysis of the partial polymerase gene identified NoV GII.4 as the dominant genotype, in accordance with previous NoV studies in Ireland. Investigating the NoV diversity of the circulating strains and the dynamics of strain replacement is important to better assess the efficacy of future NoV vaccines and to facilitate the early detection of changes in circulating NoV strains.

Molecular characterization of group A rotavirus found in elderly patients in Ireland; predominance of G1P[8], continued presence of G9P[8], and emergence of G2P[4]

Rotavirus is a major cause of gastroenteritis in young children worldwide. There have been several recent reports concerning rotavirus isolation from adults, particularly in the elderly, presenting with gastroenteritis. In this study, the authors report on rotavirus outbreaks in five separate elderly care facilities between April, and June 2011 in Ireland. The following genotypes were detected; G1P[8] (n = 5/11), G2P[4] (n = 2/11), and G9P[8] (n = 2/11). Thus, similarities to previous reports were found in that G1P[8] predominated, G9P[8] was still detected but G2P[4] was detected for the first time in a geriatric population in Ireland. Here also described is the detection of Group 2 lineage IIC rotavirus in Ireland for the first time.

Development and clinical validation of multiplex TaqMan® assays for rapid diagnosis of viral gastroenteritis

There is a need to provide rapid, sensitive, and often high throughput detection of pathogens in diagnostic virology. Viral gastroenteritis is a serious health issue often leading to hospitalization in the young, the immunocompromised and the elderly. The common causes of viral gastroenteritis include rotavirus, norovirus (genogroups I and II), astrovirus, and group F adenoviruses (serotypes 40 and 41). This article describes the work-up of two internally controlled multiplex, probe-based PCR assays and reports on the clinical validation over a 3-year period, March 2007 to February 2010. Multiplex assays were developed using a combination of TaqMan™ and minor groove binder (MGB™) hydrolysis probes. The assays were validated using a panel of 137 specimens, previously positive via a nested gel-based assay. The assays had improved sensitivity for adenovirus, rotavirus, and norovirus (97.3% vs. 86.1%, 100% vs. 87.8%, and 95.1% vs. 79.5%, respectively) and also more specific for targets adenovirus, rotavirus, and norovirus (99% vs. 95.2%, 100% vs. 93.6%, and 97.9% vs. 92.3%, respectively). For the specimens tested, both assays had equal sensitivity and specificity for astrovirus (100%). Overall the probe-based assays detected 16 more positive specimens than the nested gel-based assay. Post-introduction to the routine diagnostic service, a total of 9,846 specimens were processed with multiplex 1 and 2 (7,053 pediatric, 2,793 adult) over the 3-year study period. This clinically validated, probe-based multiplex testing algorithm allows highly sensitive and timely diagnosis of the four most prominent causes of viral gastroenteritis.

The impact of a PCR assay for candidemia on antifungal drug prescribing in critical care: an interrupted time series pilot study

SUMMARY OBJECTIVE

To evaluate the feasibility of conducting a definitive study to assess the impact of introducing a rapid PCR-based test for candidemia on antifungal drug prescribing.

METHOD

Prospective, single centre, interrupted time series study consisting of three periods of six months' duration. The assay was available during the second period, during which the PCR assay was available for routine use by physicians Monday-Friday with guaranteed 24-h turnaround time. For each period total antifungal drug use, expressed as treatment-days, was recorded and an adjustment was made to exclude estimated use for proven candidemia. Also, during the intervention period, antifungal prescribing decisions for up to 72 h after each PCR result became available were recorded as either concordant or discordant with that result.

RESULTS

While overall antifungal use remained relatively stable throughout, after adjustment for candidemia, there was a 38% reduction in use following introduction of the PCR test; however, this was nonsignificant at the 95% level. During the intervention period overall concordance between the PCR result and prescribing decisions was 84%.

CONCLUSIONS

The PCR assay for candidemia was requested, prescribing decisions were generally concordant with the results produced and there was an apparent decrease in antifungal prescription, although this was sustained even after withdrawal of the intervention; these findings should be more thoroughly evaluated in a larger trial.

Respiratory viral infection in lower airways of asymptomatic children

Aim:  The aim of this study was to determine if asthmatic children have viruses more commonly detected in lower airways during asymptomatic periods than normal children.

Methods:  Fifty‐five asymptomatic children attending elective surgical procedures (14 with stable asthma, 41 normal controls) underwent non‐bronchoscopic bronchoalveolar lavage. Differential cell count and PCR for 13 common viruses were performed.

Results:  Nineteen (35%) children were positive for at least one virus, with adenovirus being most common. No differences in the proportion of viruses detected were seen between asthmatic and normal ‘control’ children. Viruses other than adenovirus were associated with higher neutrophil counts, suggesting that they caused an inflammatory response in both asthmatics and controls (median BAL neutrophil count, 6.9% for virus detected vs. 1.5% for virus not detected, p = 0.03).

Conclusions:  Over one‐third of asymptomatic children have a detectable virus (most commonly adenovirus) in the lower airway; however, this was not more common in asthmatics. Viruses other than adenovirus were associated with elevated neutrophils suggesting that viral infection can be present during relatively asymptomatic periods in asthmatic children.

High levels of Epstein-Barr virus in COPD

Latent viral infection has been implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD). Epstein-Barr virus (EBV) is known to be important in pulmonary fibrosis. The current authors hypothesised that EBV is associated with the pathogenesis of COPD. Sputum samples were collected from patients both during exacerbations of COPD and when stable. A control group of smokers who did not have airways obstruction also had their sputum examined. The presence of EBV DNA was established and quantified using a real-time nucleic acid amplification assay. A total of 136 patients with COPD were recruited during an acute exacerbation and a total of 68 when stable. EBV was detected in 65 (48%) exacerbation cases and 31 (46%) stable patients. In the comparison group of 16 nonobstructed smokers, EBV was demonstrated in only one (6%) case. Risk of COPD in patients with EBV and who are smokers confers an odds ratio of 12.6. Epstein-Barr virus DNA is more frequently identified in the respiratory tract of chronic obstructive pulmonary disease patients in comparison with unaffected smokers. It is present both during exacerbation and when stable, suggesting that infection is persistent. Smokers who do not develop chronic obstructive pulmonary disease rarely have Epstein-Barr virus in their sputum. This finding may be of importance in the pathogenesis of chronic obstructive pulmonary disease.

Asymptomatic shedding of HSV-1 in patients undergoing oral surgical procedures and attending for noninvasive treatment

Oral surgery and stress can trigger and/or increase asymptomatic shedding of herpes simplex virus type-1 (HSV-1) into human saliva. In this investigation we examined the frequency of HSV-1 shedding in 32 patients undergoing an oral surgery procedure compared with 40 control patients attending for noninvasive treatment. Control patients comprised 18 migraine patients and 22 patients with temporomandibular (TMD) joint problems. Nested-PCR was carried out on oral rinses collected from each patient prior to treatment and 7 days post-treatment. Fifty-two of sixty-one seropositive patients were positive for HSV-1 DNA in one or both oral rinses. The frequencies of HSV-1 shedding for the oral surgery and control patients were 84.6% and 85.7% respectively. Seropositive patients who started shedding after treatment were significantly higher in oral surgery patients (46.2%) compared to control patients (34.3%). Shedding of HSV-1 in the oral cavity is not only increased by direct surgical trauma, but also appears to be common in migraine and TMD patients attending for general dental treatment. Thus pain or pain-induced stress as well as anxiety associated with dental treatment may also be a risk factor for asymptomatic shedding in specific seropositive patients attending for dental treatment.

Rapid differentiation between fluconazole-sensitive and -resistant species of Candida directly from positive blood-culture bottles by real-time PCR

In view of both the delay in obtaining identification by conventional methods following blood-culture positivity in patients with candidaemia and the close relationship between species and fluconazole (FLC) susceptibility, early speciation of positive blood cultures has the potential to influence therapeutic decisions. The aim was to develop a rapid test to differentiate FLC-resistant from FLC-sensitive Candida species. Three TaqMan-based real-time PCR assays were developed to identify up to six Candida species directly from BacT/Alert blood-culture bottles that showed yeast cells on Gram staining at the time of initial positivity. Target sequences in the rRNA gene complex were amplified, using a consensus two-step PCR protocol, to identify Candida albicans, Candida parapsilosis, Candida tropicalis, Candida dubliniensis, Candida glabrata and Candida krusei; these are the most commonly encountered Candida species in blood cultures. The first four of these (the characteristically FLC-sensitive group) were identified in a single reaction tube using one fluorescent TaqMan probe targeting 18S rRNA sequences conserved in the four species. The FLC-resistant species C. krusei and C. glabrata were detected in two further reactions, each with species-specific probes. This method was validated with clinical specimens (blood cultures) positive for yeast (n=33 sets) and the results were 100 % concordant with those of phenotypic identification carried out concomitantly. The reported assay significantly reduces the time required to identify the presence of C. glabrata and C. krusei in comparison with a conventional phenotypic method, from ∼72 to <3 h, and consequently allows optimization of the antifungal regimen at an earlier stage.

Trends in candidemia and antifungal susceptibility in a university hospital in Northern Ireland 2001-2006

OBJECTIVES

To describe the species distribution and antifungal susceptibility trends for documented episodes of candidemia at the Royal Hospitals, Belfast, 2001-2006.

METHODS

Laboratory-based retrospective observational study of all episodes of candidemia.

RESULTS

There were 151 episodes of candidemia. The species recovered were: 96 C. albicans; 26 C. glabrata; 18 C. parapsilosis; five C. tropicalis; four C. guilliermondii; one C. famata and one C. dubliniensis. We separated the data into two periods 2001-2003 and 2004-2006; contrary to the findings of other investigators, there was a notable trends toward increasing frequency of C. albicans and decreasing frequency of non-albicans species over time. Although the proportion of C. albicans, C. parapsilosis and C. tropicalis isolates susceptible to fluconazole was unchanged over time, a trend of decreased susceptibility of C. glabrata to fluconazole was noted over the six-year period. Overall, 73% and 7.7% of C. glabrata isolates had susceptible-dose-dependent and resistant phenotypes, respectively. The percentage of C. glabrata isolates susceptible to fluconazole (MIC <8 microg/ml) decreased from 36% in 2001-2003 to 0% in 2004-2006. Flucytosine resistance was detected in only 4 (2.7%) isolates. None of the isolates had an amphotericin B MIC <1 microg/ml.

CONCLUSION

A shift towards increasing dominance of C. albicans contrasts both with reports from other countries and previous data from Northern Ireland. Upwards fluconazole MIC drift among C. glabrata has important implications for empirical therapeutic decisions.

Human metapneumovirus in adults: a short case series

This study was carried out to further the available information on adult cases of human metapneumovirus (hMPV), a recently described cause of respiratory infection. Among a cohort of 741 symptomatic patients tested since 2003, the virus was diagnosed in six adults using reverse transcriptase polymerase chain reaction. Of the six, two were from the community, two were hospital inpatients with chronic obstructive pulmonary disease and two were immunocompromised patients, both of whom required ventilation and later died. This report discusses the clinical features, epidemiology and diagnosis of hMPV, highlighting that this infection may be associated with death in high-risk adults. For adults presenting with respiratory symptoms and a background of pre-existing respiratory disease or who are immunocompromised, nucleic acid-based techniques are a cost-effective means of making the viral diagnosis in a clinically relevant time frame.

Childhood respiratory infections and hospital admissions for COPD

Background

Chronic Obstructive Pulmonary Disease (COPD) exacerbations are associated with viral infections. We wished to determine if respiratory viral infection of children in the community was associated with hospital admissions of patients with exacerbations of COPD.

Methods

We collected data over a 45-month period from the Northern Ireland Regional Virus Laboratory and from a general hospital in the same locality. We studied the relationship between upper respiratory infections in children and COPD admissions. We also examined the role of school holidays.

Results

Correlations were seen between the frequency of all viral infections in children and the number of adult COPD hospitalizations (P<0.005). Subgroup analysis showed distinct relationships with epidemics of; influenza A (P<0.001), influenza B (P<0.05), adenovirus (P=0.05), respiratory syncytial virus (P<0.005) and hospital admissions of patients with COPD. There were significantly fewer COPD admissions in the week after the start of a school holiday period (P<0.05).

Conclusions

When children are hospitalized with viral respiratory infection there is an associated rise in adult COPD admissions. This suggests exacerbations of COPD are associated with epidemics of respiratory viruses. When children are on school holidays there is a reduction in COPD admissions in the community. This provides further support for respiratory viruses in the pathogenesis of COPD exacerbations.

Early experience with chronic hepatitis C in Northern Ireland: epidemiology and response to monotherapy

Chronic hepatitis C virus (HCV) infection has become a major health problem affecting an estimated 170 million people worldwide. The epidemiology of HCV and its response to treatment in Northern Ireland has not been described before. Our aims were to determine the epidemiology, histological stage, suitability for treatment and response to treatment in patients with hepatitis C presenting to one clinic in Northern Ireland. All patients were prospectively recruited with hepatitis C attending the Liver Clinic, Royal Victoria Hospital during the period December 1992 to June 1997. Sixty patients (33 male, mean age 44 years, range 19-84 years) who tested anti-HCV antibody positive were identified. The predominant genotypes were 1b (33%), 3a (28%) and 1a (26%). Most patients (78%) were asymptomatic at the time of detection and only four (7%) gave a history of jaundice. The most common modes of transmission were i.v. drug use in 30 (50%) and blood products in 20 (33%) patients. Forty-eight (86%) of the 56 patients tested were PCR positive for HCV RNA. Fifty-one patients (85%) underwent liver biopsy of whom 13 had cirrhosis (22% of original group). Twenty-nine patients were suitable for treatment, but three declined treatment and only 26 (43%) started interferon-alpha. During treatment 17 (65%) patients became PCR negative and eight (31%) remained PCR negative 12 months after completion of therapy. Liver histology was assessed before and after interferon treatment in 17 patients and showed no change in total necroinflammatory scores (p = 0.1) or staging of architectural change (p = 0.55).

CONCLUSIONS

The epidemiology and response to therapy of HCV in Northern Ireland appear comparable to elsewhere in the UK. Only a minority of anti-HCV positive non-haemophiliac patients progress to have interferon therapy suggesting that the cost of treating chronic HCV may not be as great as initially thought.

Herpes simplex type 1 shedding is associated with reduced hospital survival in patients receiving assisted ventilation in a tertiary referral intensive care unit

The impact of shedding of herpes simplex virus type 1 (HSV-1) on hospital survival of patients receiving assisted ventilation in an adult tertiary referral, acute trauma intensive care unit was assessed. The study was designed to address a clinical impression linking HSV-1 recovery with poor survival. Two hundred and forty-one males and 152 females were enrolled into a longitudinal cohort study. Combined throat swabs and tracheal secretions were tested for HSV-1 shedding using a nested nucleic acid amplification protocol; patients were ranked as nonshedders, shedders, and high-level shedders. Nonparametric analysis assessed the impact of shedding on hospital survival and logistic regression measured the confounding influence of sex, age, and the Acute Physiology, Age and Chronic Health Evaluation (APACHE II) score. Linear-by-linear association determined the influence of the level of shedding on hospital survival. The observed mortality rate was 113/393 (28.8%). Patients shedding HSV-1 106/393 (27%) had a significant reduction in hospital survival 66/106 (62%) in HSV-1 shedders compared with 217/287 (75.6%) in nonshedders (P = 0.002). This difference remained significant when adjusted for age and sex (P = 0.026). Respective mortality figures for HSV-1 shedders and nonshedders were 43/106 (40.6%) and 70/287 (24.4%) (P = 0.002). HSV-1 shedding was associated with a significant reduction in hospital survival amongst patients receiving assisted ventilation. Hospital mortality in HSV-1 shedders was increased by 16.2% over nonshedders. The role of HSV-1 in this setting needs to be addressed.

Emergence of herpes simplex type 1 as the main cause of recurrent genital ulcerative disease in women in Northern Ireland

BACKGROUND

Genital herpes is a common infection affecting some 20% of sexually active people. Although herpes simplex virus (HSV) types 1 and 2 can both establish genital latency, reactivation from the sacral ganglia favours HSV-2. Over the past decade the incidence of type 1 genital infection in women has greatly increased.

OBJECTIVES

To determine whether the increased prevalence of HSV-1 genital infection was benign or influencing the pattern of virus recovery in recurrent infection.

STUDY DESIGN

A retrospective analysis of laboratory computer records was undertaken. Patients attending six genitourinary medicine (GUM) departments, over an 80 months period, were identified. Recurrent infection was confirmed where virus was recovered from at least two separate episodes of genital ulceration that were separated by an interval of 12 or more weeks. Episodes were further analysed for frequency, age, gender and virus type.

RESULTS

Sixty nine patients with recurrent genital herpetic infection were identified. HSV-1 and HSV-2 were predominantly recovered from recurrent genital infections in females (34 HSV-1 vs. ten HSV-2) and males (one HSV-1 vs. 24 HSV-2), respectively (P>0.001). The mean age of females and males, at the initial diagnosis, was 26 and 39 years. There was no difference in the recurrence rate by type.

CONCLUSIONS

HSV-1 has become the commonest cause of recurrent genital ulceration in Northern Ireland, almost entirely due its recent increased prevalence in women over the last decade. Women are experiencing genital herpetic infections at an earlier age than men.

Clinical assessment of a generic DNA amplification assay for the identification of respiratory adenovirus infections

BACKGROUND

respiratory adenoviruses are common, often resulting in serious sporadic and epidemic infections and impaired immunity can dramatically increase their severity. They are now thought capable of establishing latency. Diagnosis by culture is slow while direct antigen detection by immunofluorescence lacks sensitivity. Molecular diagnosis can be both rapid and sensitive but the genetic heterogeneity of adenoviruses poses problems.

OBJECTIVES

to design a generic adenovirus nested polymerase chain amplification assay designed to be capable of detecting all respiratory adenoviruses. This was achieved through optimised thermal cycling and the development of a generic degenerate primer set targeting the adenovirus hexon gene.

STUDY DESIGN

this was a cross-sectional study on 172 respiratory specimens from hospital-based patients, and one from a general practice, in Northern Ireland. A comparison was made between the amplification assay, virus culture and immunofluorescence.

RESULTS

the nested polymerase chain reaction (nPCR) assay had a generic capacity for adenovirus detection and an analytical sensitivity of 6.4x10(2) copies/ml. Using an expanded gold standard (defined as a true positive or a true negative where a specimen was positive or negative by at least two of the study assays, respectively), PCR had a clinical sensitivity and specificity of 46/46 (100%) and 15/126 (91.3%), respectively. Patients with acute respiratory adenovirus infections were more likely to be male (chi(2), p=0.005) and to present with a fever (chi(2), p=0.02) than patients diagnosed with another respiratory virus. Co-infection was identified in 12/172 patients.

CONCLUSIONS

the nested amplification assay proved highly sensitive in both the analytical and clinical settings for the detection of respiratory adenovirus infections.

Clinical utility of nested multiplex RT-PCR for group F adenovirus, rotavirus and norwalk-like viruses in acute viral gastroenteritis in children and adults

BACKGROUND

The diagnosis of viral gastroenteritis can be carried out by non-molecular techniques such as electron microscopy (EM), enzyme-immunoassay and latex agglutination tests and various molecular techniques. Normally molecular detection requires the use of three separate protocols to detect the three main causes of viral gastroenteritis, adenoviruses, rotaviruses and norwalk-like viruses (NLV) which have different types of nucleic acid. The development of a sensitive and specific assay which could detect these targets would have major advantages for the clinical virology laboratory.

OBJECTIVES

The aims of the present study were to develop a sensitive and specific multiplex molecular assay and to apply it to the detection of viral agents in clinical cases of acute gastroenteritis.

STUDY DESIGN

The multiplex assay was designed using Access RT-PCR (Promega). Primers were researched and selected for their specificity and broad range detection of the viral agents across the various genotypes of group A rotaviruses, NLV and group F adenoviruses.

RESULTS

From September 2000 to August 2001 we tested 1945 clinical specimens. Rotavirus infections were detected in 190 with an age range from 12 days to 8 years old. Group F adenovirus was detected in 96 patients ranging from 15 days to 10 years old. A further single case of group F adenovirus was detected in an adult of 75 years old. NLVs were detected in 132 patients. There were 55 infections in children less than 7 years old. In 10 different outbreaks involving 130 adult patients there were 57 NLV positives. Sporadic NLV infection was detected in 11 of 600 adult patients. There were 4 patients with dual infections.

CONCLUSIONS

The assay detailed here has proved an invaluable tool for the investigation of acute gastroenteritis in specimens from patients of all ages. We found it convenient to use a single mastermix with a single protocol to test all specimens from patients of all ages. NLV in children is often overlooked and/or under reported, particularly where less sensitive assays such as EM are being employed for diagnosis.

A comparison of nested polymerase chain reaction and immunofluorescence for the diagnosis of respiratory infections in children with bronchiolitis, and the implications for a cohorting strategy

Cohorting bronchiolitis patients infected with respiratory syncytial virus (RSV) and/or influenza viruses is paramount in preventing cross-infection of these viruses in hospital. Nested polymerase chain reaction (nPCR) was compared with immunofluorescence (IF) for the detection of RSV subtypes A and B in children with suspected bronchiolitis. Co-infection with influenza A(H3N2), Chlamydia spp. and picornavirus/rhinovirus was also investigated using molecular techniques.A total of 50 nasopharyngeal secretions collected from babies admitted with bronchiolitis in the month of January 2000, comprising IF RSV positive (N= 27) and RSV negative (N= 23) specimens, were tested for both RSV subtypes, influenza A(H3N2), Chlamydia spp. and picornavirus/rhinovirus by nPCR. Nested PCR detected 28 specimens positive for RSV (RSV A = 20, RSV B = 8), which was two more than detected by IF. Influenza A(H3N2) was detected in three specimens, Chlamydia trachomatis in one, and picornavirus in 11, of which nine were confirmed to be rhinovirus by nPCR. Dual infection was detected in five cases using nPCR. Nested PCR proved useful in detecting RSV and influenza A(H3N2) infections missed by IF, and also other respiratory tract pathogens not routinely investigated. The clinical implications and risk of cross-infection with potentially virulent viruses due to inaccurate results from insensitive techniques, highlights the need for molecular assays such as nPCR to be employed as a routine method of investigation, provided as part of the laboratory service. Cohorting of patients with clinical bronchiolitis should continue, whilst awaiting laboratory confirmation.

Nested multiplex polymerase chain reaction for the diagnosis of cutaneous herpes simplex and herpes zoster infections and a comparison with electronmicroscopy

Herpes simplex virus (HSV) and varicella zoster virus (VZV) are common causes of cutaneous and mucocutaneous vesicular eruptions. Laboratory diagnostic techniques include Tzanck smears, electronmicroscopy, antigen detection and viral culture. This paper describes a nested multiplex polymerase chain reaction with respective sensitivities of 0.0001, 0.01 and 0.1 TCID50 for VZV, HSV-1 and HSV-2. The assay was used in (a) a salvage capacity for slides already processed for electronmicroscopy, and (b) as a front-line assay for prospectively processed specimens. Sixty-two glass slides with vesicle lymph/scrapings from 58 patients with suspected cutaneous herpetic lesions were examined. The clinical presentations were described as atypical/not specified (24), VZV (20) or HSV (18), and involved eruptions from diverse anatomical sites, including the genitalia. Of the 62 specimens, 6 and 38 were positive by electronmicroscopy and multiplex PCR respectively, giving a comparative sensitivity of 16% for electronmicroscopy. Nested multiplex PCR identified 15 VZV and 20 HSV-1 infections. Where the clinical details indicated either HSV or VZV (38/62), nested multiplex PCR was statistically likely to be reactive (26/38 vs. 9/24) (chi2 P = 0.000004) whereas electronmicroscopy was not (4/38 vs. 2/24) (chi2 P= 0.77). Where the clinical details indicated VZV (20/62) or HSV (18/62), nested multiplex PCR was statistically more likely to confirm VZV (10/20 vs. 5/42) (chi2 P= 0.001) or HSV (9/18 vs. 11/44) (chi2 P = 0.05) respectively. Two suspected HSV and 6 suspected VZV infections were shown to be VZV and HSV respectively by nested multiplex PCR.

The relationship between elevated fibrinogen and markers of infection: a comparison of seasonal cycles

To test the hypothesis that higher levels of fibrinogen in winter are related to infections via the acute phase response, we assessed seasonal variation in fibrinogen and C-reactive protein, together with three other responses to infection: white cell count, human herpesvirus-6 IgG antibody and interleukin-6. Monthly blood samples from 24 subjects aged 75+ years were assessed for fibrinogen, C-reactive protein, white cell count, and human herpesvirus-6 IgG antibody. Interleukin-6 was measured in seven. Seasonal variation of these measures was determined by the population-mean cosinor procedure. Fibrinogen had a significant seasonal variation with a winter peak (mid-February) 1.26 g/l above the corresponding summer trough. C-reactive protein had a late-February peak, 3.71 mg/l above the summer trough. No seasonal rhythm was found in any other response to infection investigated. This study provides no evidence that winter infections are responsible for the seasonal variation in fibrinogen or C-reactive protein. The explanation for the seasonal changes in these proteins remains unknown.

Hepatitis C virus: an important occupational hazard?

Infection with Hepatitis C virus (HCV) is estimated to affect 3% of the world's population and is an important cause of liver disease. It is most commonly transmitted by percutaneous exposure. Although current evidence does not suggest an increased prevalence of HCV infection among healthcare workers, transmission of infection following occupational exposure has been demonstrated. An average transmission rate of 1.8%, following percutaneous injury, has been reported. The risk of transmission is higher from patients with viraemia, as measured by a positive polymerase chain reaction for HCV RNA. After exposure to HCV, healthcare workers should be actively followed up, initially using a test to detect viral RNA. This may facilitate earlier diagnosis and treatment. Recent reports in the UK, of transmission of infection to patients from HCV infected healthcare workers, have prompted a review of the appropriateness of HCV infected individuals undertaking exposure prone procedures.

Parvovirus B19 in kidney transplant patients

Renal transplant patients were screened for the presence of parvovirus B19, before transplantation and monthly for 4 months after transplantation, by means of a sensitive nested PCR assay. Upon screening plasma from 110 patients, we found that two asymptomatic patients were B19 DNA positive. One of these patients was PCR positive in the plasma sample taken 2 months after transplantation; the plasma contained anti-B19 IgG antibodies before transplant and throughout the follow-up period, with an increase in the IgG level in the second posttransplant sample coinciding with the detection of B19 DNA. IgM antibodies to B19 were not detected in this patient. Because, for this patient, the donor's spleen DNA was also B19 DNA positive, we suspect B19 transmission from the donor and limited B19 replication, inasmuch as this patient already had a primed immune response to B19. The other patient was PCR positive in the pretransplant and in the plasma sample taken 1 month after transplant and contained a strong anti-B19 IgG response in the pretransplant sample and throughout the follow-up period-and anti-B19 IgM antibodies were not detected before or after transplantation. By testing samples taken from this patient at 2 weeks, 2 months, and 3 months before transplantation, we were able to determine that the infection occurred shortly before transplantation. Unexpectedly, this graft failed and was removed 2 days after transplantation despite a negative cross-match. A pathological examination of the kidney indicated acute vascular rejection, suggesting a possible role for B19 in this complication.

Description of a nonlethal herpes simplex virus type 1 glycoprotein D deletion mutant affecting a site frequently used for PCR

We report a herpes simplex virus type 1 mutant which failed to amplify with a commonly used glycoprotein D primer set. The virus contained a nine-base deletion in the gene's 5' nontranslated region. The altered amplicon was clearly distinguishable on a 4% high-resolution agarose gel.

A comparison of virus isolation, indirect immunofluorescence and nested multiplex polymerase chain reaction for the diagnosis of primary and recurrent herpes simplex type 1 and type 2 infections

134 swabs in viral transport medium were received from 126 patients with suspected clinical HSV-1 and HSV-2 infections. They were tested by (i) nested multiplex polymerase chain reaction NMPCR (strongly positive specimens had visible bands on both rounds of PCR) without prior extraction, (ii) culture in primary rhesus monkey kidney, E6-Vero, RD and HEp-2 cells and (iii) antigen detection by immunofluorescence (IF). Antigen detection employed four novel pools (A-D) of monoclonal antibodies (Mab): A was HSV-1 specific, B was HSV-2 specific while C and D were generic. In comparison to NMPCR the sensitivity and specificity of (i) culture was 59% (22/37) and 100% (134/134), (ii) IF by Pool A was 59% (16/27) and 100% (117/117), (iii) IF by Pool B was 40% (4/10) and 100% (130/130) and (iv) IF by Pools C and D were 60% (18/30) and 100% (96/96). Specimens positive by culture were more likely to be strongly positive by NMPCR (chi2 P = 0.004). Typing by each method concurred on all occasions. NMPCR was cost effective, easier to perform and was the most sensitive method for HSV detection. It should become the method of choice for HSV diagnosis.

Low pH-induced cytopathic effect--a survey of seven hantavirus strains

Hantaviruses do not produce cytopathic effects (CPE) in cell culture. However, a syncytial CPE can be induced in 7-day cultures of hantavirus growing in Vero E6 cells by reduction of the pH to approximately 6.2 using a HEPES based buffer. The appearance of this acid induced CPE was examined for seven different hantavirus strains. The differences noted were striking and reflected the taxonomic differences between hantaviruses. At 10-100 TCID50% the size of syncytial foci was very large for Seoul type viruses and smallest for Puumala viruses. The size of syncytia for Hantaan (HTN) virus was intermediate between Puumala (PUU) and Seoul (SEO) type viruses.

Investigation of seroprevalence of respiratory virus infections in an infant population with a multiantigen fluorescence immunoassay using heel-prick blood samples collected on filter paper

Respiratory viruses are an extremely common cause of childhood morbidity. However, the current seroprevalence of viruses in infant populations is difficult to establish because invasive venipuncture may be technically and ethically unacceptable. This prospective study aimed to establish the seroprevalence of respiratory viruses in an infant population by use of a novel multiantigen fluorescence immunoassay against common respiratory viruses, using heel-prick blood samples collected on filter paper. Mothers and babies were recruited in the immediate peripartum period in the Royal Maternity Hospital, Belfast. Cord blood samples at birth and heel-prick filter paper blood samples at 7 mo were collected for measurement of virus-specific IgG to respiratory syncytial virus, influenza A virus, adenovirus, and parainfluenza virus type 1, type 2, and type 3 by indirect immunofluorescence using a multiviral assay developed for this purpose. Of 386 mothers approached, 325 (84%) permitted follow-up at 7 mo, and of these, 256 (79%) agreed to the heel prick. From 234 paired samples, 125 infections were documented. Adenovirus infections were commonest, 53 (22.6%), followed by respiratory syncytial virus, 32 (13.7%); influenza A virus, 22 (9.4%); parainfluenza virus type 3, 14 (6%); parainfluenza virus type 1, 2 (0.85%); and parainfluenza virus type 2, 2 (0.85%). These results demonstrate the seroprevalence of a range of respiratory viruses in an infant population, using a novel multiviral immunoassay. The filter paper collection of blood samples and multiantigen assay format has implications for easy, widespread viral serodiagnosis in both seroepidemiology studies and in the diagnosis of pediatric viral illnesses. Filter paper permits recovery of respiratory virus-specific IgG and can be used as a simple and acceptable epidemiologic and diagnostic tool.

Effect of faecal consistency on virological diagnosis

A study was set up to investigate the effect of consistency of routine faecal specimens on the diagnostic yield by electron microscopy (EM) and virus isolation. A total of 3078 specimens were characterized as solid, semisolid, or liquid. Of 2568 specimens processed by EM a virus was demonstrated in 8.6% of liquid, 19.9% of semisolid and 25.2% of solid specimens (Chi-squared for linear trend, P value <0.0001). This observation was valid for both adenovirus (2.4%, 5.0% and 6.6%) and rotavirus (5.2%, 13.6% and 16.6%). Virus isolation was positive in 3.6% of liquid, 17.4% of semisolid and 18.1% of solid specimens. (Chi-squared for linear trend, P value <0.0001). We suggest that solid faecal specimens at the end of an episode of diarrhoea will have a higher diagnostic yield than liquid specimens at the peak of symptoms. Our findings repudiate the commonly held dogma that viruses of gastroenteritis are more likely to be found in liquid than in solid faecal specimens. This finding has important implications for those establishing diagnostic algorithms for the investigation of viral gastroenteritis.

Recrudescent herpes simplex infection mimicking primary herpetic gingivostomatitis

We report six cases of recrudescent intraoral herpes simplex infection clinically indistinguishable from primary herpetic gingivostomatitis. All infections occurred in healthy children or young adults. Serological analysis demonstrated herpes simplex virus (HSV)-specific IgG at initial presentation, indicating that the infection was not a primary infection. Convalescent sera exhibited HSV-specific IgM and a rising HSV-specific IgG titre. These findings demonstrate that the initial clinical diagnosis of primary herpetic gingivostomatitis was erroneous and that what was actually being observed was widespread recrudescent intraoral herpes simplex infection.

The Unlinked Anonymous HIV Prevalence Monitoring Programme in N. Ireland 1992-1995

Previous evidence has suggested that Northern Ireland is a low seroprevalence area for HIV infection. The Unlinked Anonymous HIV Prevalence Monitoring Programme initiated in England and Wales in 1990 was extended to Northern Ireland in 1992. Patients attending the Genitourinary Medicine Clinic at the Royal Victoria Hospital have, with informed consent, been tested anonymously for HIV infection since that time. The results of the survey between 1992 and 1995 have shown an overall seroprevalence rate 3.01% for homosexual/bisexual men, 0.08% for heterosexual men, and 0.05% for heterosexual women. These results confirm the previous impression of low HIV seroprevalence in Northern Ireland and the survey provides an excellent longitudinal study by which changes may be monitored.

Acute visual disturbance in a young adult

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Parvovirus B19 infection in AIDS patients

Bone marrow of 61 HIV-1-infected patients and 23 control patients was examined to determine the incidence of B19 infection and its clinical impact in HIV-1-infected persons. Of the 61 HIV-infected patients studied, ages ranged from 22-47 years with a mean of 33.2 years. There was a man:woman ratio of 3.8:1. With regard to staging of HIV disease at the time of bone marrow sampling, 52 patients were CDC group 4, 5 patients were CDC group 3, and 4 patients were CDC group 2. Control patients, were not known to be HIV-1-infected, and had one of the following conditions: lymphoma, leukaemia, thrombocytopenia, thrombocytosis, anaemia, multiple myeloma, raised serum IgM. Thirteen of 61 HIV-infected patients and 0 of 23 control patients were positive for B19 DNA in bone marrow (two-tailed P value = 0.016). Within the HIV-infected group, the average haemoglobin among persons testing B19 DNA positive (n = 13) was 11.1 g/dl, compared with 11.5 g/dl among persons testing B19 DNA negative (n = 48). In conclusion, B19 persistence may be common and frequently subclinical in AIDS patients.

Isolation of viruses from clinical specimens in microtitre plates with cells inoculated in suspension

Virus isolation is essential for the provision of a full diagnostic virology service. Present methods are time consuming, expensive and relatively inflexible for routine use. Our objective was to audit our existing virus isolation system and to develop a sensitive, flexible virus isolation system which could be adapted for use in a busy routine laboratory which is required to provide a service for a wide range of clinical situations. We carried out a pilot study which compared conventional roller tube monolayer cultures to a microplate system using cells inoculated in suspension and showed that the microplate method using extra cell lines could provide a more sensitive system for virus isolation. This system was adapted for routine use using six cell lines inoculated in suspension and the results are presented for 2610 specimens for virus isolation and 972 for Clostridium difficile toxin (CDT) detection. There were 516 viruses isolated and 229 specimens positive for CDT using this system. Polioviruses (92), echoviruses (35), coxsackieviruses (15) and untyped enteroviruses (13) were isolated in RMK, E6-vero and RD cells. Adenoviruses (137) were isolated in HEp2 and E6-vero cells. Herpes simplex virus (HSV) was isolated from 149 specimens in E6-vero, FCL and HFF9 cells. Myxoviruses (38) and paramyxoviruses were isolated in RMK cells. HEp2 was the only cell line necessary to isolate the 33 respiratory syncytial viruses (RSV). Cytomegaloviruses (CMV) (2) and varicella zoster (1) virus (VZV) were isolated only in the human fibroblast cell line HFF9. Rubella virus was isolated from a baby with congenital rubella in RMK, E6-vero and additionally in BGM cells. In conclusion, the use of cells inoculated in suspension in microtitre plates for virus isolation was sensitive and convenient. It allowed the use of six cell lines for routine virus isolation without using additional laboratory staff time. It improved turnaround times. It was also safer microbiologically than conventional isolation in tube monolayers. The precise identification of virus isolates was simplified.

Evidence of hantavirus in wild rodents in Northern Ireland

A survey of evidence of rodent hantavirus infection in County Down, Northern Ireland was carried out by using immunofluorescence to detect virus antigen and antibody. Antibodies to hantavirus (R22 strain of Seoul virus and Hantaan 76-118) were found in 11/51 (21.6%) brown rats (Rattus norvegicus), 1/31 (3.2%) field mice (Apodemus sylvaticus) and 17/59 (28.8%) house mice (Mus domesticus). Seven rodents had evidence of hantavirus antigen in lung tissues. Antibody positive animals were significantly more likely to be adults than juveniles (P = 0.04) but and there was no sex difference between antibody positive and negative animals. House mice were more likely to be antibody positive if captured inside farm outbuildings (P = 0.08). Attempts to culture virus from the rodent material were unsuccessful. This work demonstrates a substantial rodent reservoir for hantavirus in Northern Ireland.

Follow-up study of clinical and immunological findings in patients presenting with acute parvovirus B19 infection

This study was undertaken to examine the natural history of parvovirus B19 infection in persons without a known immune defect in terms of both clinical symptoms and immune responsiveness to the virus. Fifty-three patients with acute B19 infection (positive for serum anti-B19 IgM) were studied; symptoms at acute infection were rash and arthralgia (n = 26), rash (n = 7), arthralgia (n = 16), aplastic crisis (n = 3), and intrauterine fetal death (n = 1). Patients were followed for 26-85 months (mean 57 months) and reassessed for persistent symptoms, anti-B19 antibodies, and antibodies to the unique region of B19 VP1. There were 23 cases of arthralgia persisting for longer than 1 year after acute infection. One of these patients, a 48-year-old woman at follow-up, had had persistent arthralgia for 4 years following acute B19 infection, had rheumatoid factor at a titre of 1920 IU/ml detected at follow-up, and had been independently diagnosed as having rheumatoid arthritis at the time of follow-up. All 53 patients were positive for serum anti-B19 IgG compared to 45 of 53 age- and sex-matched control patients, a significant difference (two-tailed P value = 0.008). All test patients at follow-up and control patients were negative for serum anti-B19 IgM and antibodies to the unique region of B19 VP1. Serum from acute infection from 33 of 53 test patients was tested for antibodies to the unique region of VP1, and 16 of these were positive. The presence of this antibody did not correlate with subsequent duration of symptoms but did correlate with a short interval between symptom onset and blood sampling. The unique region of B19 VP1 is known to be crucial for a successful humoral response to the virus, and it seems that the antigenic role played by this region is important only during the acute phase of B19 infection.

Genetic diversity in the non-structural gene of parvovirus B19 detected by single-stranded conformational polymorphism assay (SSCP) and partial nucleotide sequencing

A homologous region in the parvovirus B19 non-structural gene (B19 nt 1399-1682) was examined in 50 samples from patients with a wide variety of B19-related disease from various countries by PCR amplification, single-stranded conformational polymorphism (SSCP) assay and nucleotide sequencing. Five SSCP types were confirmed by nucleotide sequence analysis. Of a total of 6 mutations, all were silent. Types 3 and 4 accounted for 92% of strains. There was no correlation between genome type and either clinical illness or patient age. However, there was a correlation between SSCP type and country of origin. Type 3 strains predominated in Japan (18/26) and the UK (6/8), whereas type 4 predominated in the USA (9/12). Notably, type 3 strains also predominated among females (14/18), whereas there were approximately equal numbers of strain types 3 (7/17) and 4 (8/17) among males; an observation which remains unexplained. Within the Japanese group, although type 3 strains predominated overall, strains isolated from 1981 to 1987 consisted of types 1 (2/15), 2 (1/15), 3 (8/15), and 4 (4/15), whereas strains isolated from 1990 to 1994 consisted almost entirely of type 3 (10/11).

Design and production of a target-specific monoclonal antibody to parvovirus B19 capsid proteins

Native parvovirus B19 was used as antigen to produce a mouse monoclonal antibody, R92F6, which reacted with B19 VP1 and VP2, neutralised the virus in bone marrow culture, and labelled infected cells in paraffin-embedded tissues from cases of B19-related fetal hydrops. The B19 epitope recognised by R92F6 (amino acids 328-344 from the amino terminal region of B19 VP2) appears to be highly conserved, since these tissue specimens were obtained over a 13 year period from widely spaced locations in the UK. This epitope was synthesised as a peptide (S7b) which was used as antigen to produce a mouse monoclonal antibody, 3H8, which specifically reacted with the B19 capsid proteins VP1 and VP2 in immunofluorescence and immunoblot assays. 3H8 was also capable of labelling formalin-fixed, paraffin-embedded, B19-infected fetal tissue and was shown to be of the same isotype as R92F6 (IgG1). Highly conserved epitopes derived from conserved amino acid sequences are valuable in the diagnosis of infectious disease. If these can be recognised and accurately synthesised, the production of specific mouse monoclonal antibodies may be possible for many human pathogens. Considering the vast amount of sequence data available in the literature, this approach seems to be both feasible and of wide potential.

Development of an IgM capture assay for the diagnosis of B19 parvovirus infection using recombinant baculoviruses expressing VP1 or VP2 antigens

BACKGROUND

The clinical manifestations of human parvovirus B19 infection are often similar to those induced as the result of infection by other infectious agents such as rubella and some bacteria. Although diagnosis of B19 infection is feasible by detection of specific antibodies, the tests require viraemic serum as a source of antigen. This inevitably leads to problems of reproducibility and dependence upon appropriate high quality clinical material.

OBJECTIVES

To develop a monoclonal antibody capture ELISA (MACEIA) for detecting anti-B19 IgM antibody in human sera, using recombinant baculoviruses expressing the B19 parvovirus VP1 and VP2 proteins and to compare this with MACEIA using a plasma derived B19 antigen.

STUDY DESIGN

Sera from 85 patients with proven B19 infection and the paired convalescent sera from 26 anti-B19 IgM-positive acute samples were examined for B19-specific IgM antibody by a monoclonal antibody capture assay that utilised recombinant baculoviruses expressing B19 proteins in lieu of a plasma-derived B19 antigen. Control samples consisted of 24 anti-rubella IgM, 24 anti-EBV IgM and 102 negative sera from uninfected individuals.

RESULTS

Eighty-four of the 85 sera were anti-B19 IgM positive by MACEIA using recombinant baculovirus derived B19 antigen and by indirect immunofluorescence tests, whereas 79 were positive by MACEIA using plasma-derived antigen. Of the 26 convalescent samples which were positive as acute sera, 4 had become negative by 8 weeks post-infection. The expressed recombinant baculovirus antigens had identical molecular weights to the VP1 (84 kDa) and VP2 (58 kDa) proteins of virus purified from human plasma. Recombinant baculovirus-derived VP1 antigen was as effective as VP2 particles at detecting antibodies.

CONCLUSIONS

Recombinant proteins VP1 and VP2, obtained from recombinant baculovirus-infected cell lysate, showed equal specificity to and higher sensitivity than, B19 virus purified from human plasma when used in MACEIA to detect B19-IgM antibody.

Varicella zoster gastritis in a bone marrow transplant recipient

A case is reported of a patient who had previously undergone autologous bone marrow transplantation for recurrent Hodgkin's disease. The patient developed a generalised vesicular skin eruption. The clinical diagnosis was of disseminated shingles. Herpes viral particles were identified within the vesicular fluid by electron microscopy and using a specific monoclonal antibody to varicella zoster virus (VZV), positive immunofluorescence was detected in scrapings from the base of a vesicle. Gastroscopy and biopsy were performed because of severe abdominal pain and vomiting. The histological features were of non-specific active inflammation. Despite the histological absence of viral inclusions electron microscopy of the gastric biopsy revealed the presence of intranuclear herpes viral particles with a diameter of 90-100 nm. VZV specific DNA was detected by the polymerase chain reaction in the gastric biopsy extract. The patient was treated with acyclovir and made a full recovery.