Preventing neonatal herpes--current strategies

Comparison of Chemicon SimulFluor direct fluorescent antibody staining with cell culture and shell vial direct immunoperoxidase staining for detection of herpes simplex virus and with cytospin direct immunofluorescence staining for detection of varicella-zoster virus

A new rapid direct immunofluorescence assay, the SimulFluor direct fluorescent-antibody (DFA) assay, which can simultaneously detect herpes simplex virus types 1 and 2 (HSV-1 and -2) and varicella-zoster virus (VZV), was evaluated in comparison with our current standard procedures of (i) shell vial direct immunoperoxidase (shell vial IP) staining and cell culture for detection of HSV and (ii) cytospin DFA staining for VZV detection. A total of 517 vesicular, oral, genital, and skin lesion specimens were tested by all three procedures. For HSV detection, the SimulFluor DFA assay had an overall sensitivity, specificity, positive predictive value, and negative predictive value of 80.0, 98.3, 92.3, and 95.1%, respectively, when compared to culture. Shell vial IP staining had a sensitivity, specificity, positive predictive value, and negative predictive value of 87.6, 100, 100, and 96.9%, respectively, when compared with cell culture. The SimulFluor DFA assay, however, offers same-day, 1.5-hours results versus a 1- to 2-day wait for shell vial IP staining results and a 1- to 6-day wait for culture results for HSV. For VZV detection SimulFluor DFA staining detected 27 positive specimens as compared to 31 by our standard cytospin DFA technique--a correlation of 87.1%. A positive SimulFluor reaction for VZV is indicated by yellow-gold fluorescence compared to the bright apple-green fluorescence observed by cytospin DFA staining. There is no difference in turnaround time between the two assays. The SimulFluor DFA assay is a rapid immunofluorescence assay that can detect 80% of the HSV-positive specimens and 87% of the VZV-positive specimens with a 1.5-h turnaround time.

The Canadian Paediatric Surveillance Program: Beyond collecting numbers

Traditionally, anecdotal data and retrospective case reports have been used for insight into the natural history, epidemiology and case management of rare diseases. This lack of information has often resulted in delayed recognition and diagnosis of rare diseases, increasing the risk of complications or death of children. Furthermore, the study of rare condiions has been hampered by the need to generate sufficient numbers to enable meaningful analysis and interpretation, a need that requires data collection from a large population. The Canadian Paediatric Surveillance Program (CPSP) was established in 1996 to contribute to the improvement of the health of children and youth by national surveillance and research into uncommon paediatric diseases and conditions. The CPSP provides the mechanism to enable the prospective collection of national epidemiological data on such diseases and conditions. After five years, has the CPSP risen to meet expectations? Is it based on scientific evidence? The CPSP has revealed itself to be a very sensitive surveillance tool, providing invaluable longitudinal, epidemiological information for public health decision-makers. The present paper reviews how the different communicable diseases on the CPSP monthly reporting form stand the test of the 1998 priority criteria for diseases under national surveillance set by Canada's Advisory Committee on Epidemiology.

HSV-2 specific serology should not be offered routinely to antenatal patients

The proposal to introduce antenatal screening for HSV has no evidence for a public or individual health benefit; indeed, it has the potential to increase anxiety for patients, with a minimal likelihood of reducing the risk of neonatal herpes infection. Antenatal screening of an essentially healthy population of women must be validated in settings of different rates of neonatal HSV infection and the purposes and limitations of screening clearly outlined. Identification of pregnant women at risk of acquiring genital herpes in pregnancy is also dependent upon being able to obtain the serostatus of the male sexual partner which will reduce the practical application of the test if both patient and partners need to be screened. We recommend that efforts to improve on the currently established mechanisms for reducing the morbidity of neonatal herpes, namely early diagnosis and prompt treatment, must take priority for resources over new and unevaluated screening programmes, such as routine testing of antenatal patients.

Herpes simplex: evolving concepts

A large body of molecular biologic research has begun to clarify some basic aspects of viral latency and reactivation. The clinical definition of herpes simplex virus infection is expanding, with the recognition that the disease is largely asymptomatic and that most transmission occurs during periods of asymptomatic viral shedding. With this awareness, serologic diagnosis has become increasingly important. New treatment modalities are now available, and other promising treatments are in development.

Automated microneutralization: method and comparison with western blot for type-specific detection of herpes simplex antibodies in two pregnant populations

A novel method for the detection of microneutralization was compared to Western blot for detection of type-specific antibodies to herpes simplex virus in two pregnant patient populations in Vancouver. From an unselected group of women in labor in a tertiary care obstetric hospital (426) and another group of women specially referred for assessment of genital herpes in pregnancy (195) 20 and 88%, respectively, were seropositive for herpes simplex virus type 2 antibodies by Western blot. During the study period, 93 (48%) of the high-risk group were culture positive for HSV-2 and all but one case was verified serologically by Western blot. Therefore, the sensitivity for Western blot in this high seroprevalence group was 99%. The false-negative case had longstanding recurrent infection and on retest was found to be a laboratory error. For microneutralization, type-specificity was especially difficult to distinguish among patients with mixed viral type patterns. Comparing microneutralization to Western blot as the gold standard, sensitivity, specificity, positive and negative predictive values were 84, 78, 97 and 40% respectively, for the referred group and 73, 82, 51 and 92%, respectively, for the unselected group. Poor negative and positive predictive values for the referred group and unselected populations, respectively, demonstrate that microneutralizations are not clinically acceptable for type-specific antibody detection. By contrast, serology by Western blot is very sensitive and apparently highly specific.

The management of recurrent genital herpes infection in pregnancy: a postal survey of obstetric practice

OBJECTIVE

To determine clinical practice amongst obstetricians in the UK in the antepartum and intrapartum management of pregnant women with recurrent genital herpes infection.

METHODS

All Members and Fellows of the Royal College of Obstetricians and Gynaecologists resident in the UK were sent a questionnaire requesting information concerning their management of pregnant women with recurrent genital herpes infection.

RESULTS

There was a 76% response rate to the questionnaire. Of the 1201 obstetricians who responded, only 369 (31%) admitted to having a formal policy governing the management of herpes in pregnancy within their unit. However, regular screening was advocated by 718 (60%), of whom 463 (64%) performed regular antenatal swabs for viral culture. At the time of presentation in labour 974 obstetricians (81%) routinely examined the genitals for evidence of a recurrence. When asked in what circumstances caesarean section would be considered an appropriate method of delivery in women with genital herpes infection, 1107 (92%) felt that visible active lesions at the time of labour was sufficient. However, when the membranes had been ruptured for more than four hours in the presence of genital lesions, only 678 (56%) considered this an indication for caesarean section. Caesarean section was more likely to be considered appropriate in this situation by obstetricians who performed antenatal screening (chi 2 = 30.38, P < 0.0001). Five hundred and ninety-six obstetricians (50%) felt that a positive viral culture obtained at antenatal screening from the most recent occasion prior to presentation in labour was an indication for caesarean section, although of this group 192 (32%) said they did not perform antenatal screening by viral culture. The reporting of a recurrence by the patient without visible evidence of disease was considered an appropriate indication for caesarean section by 438 respondents (36%). Maternal request for caesarean section regardless of recurrences at delivery was considered an acceptable indication for operative delivery by 745 obstetricians (62%).

CONCLUSIONS

1. There seems to be little agreement amongst obstetricians in the UK regarding the management of recurrent genital herpes infection in pregnancy. 2. The management possibilities are reviewed and suggestions are made for a more cohesive approach to the problem.

Herpes simplex virus infection of the fetus and newborn

Although infrequent, untreated neonatal herpes results in death in half the cases and neurologic sequelae in three quarters of the survivors. Neonatal infection is usually acquired from maternal genital herpes, which is asymptomatic or unrecognized in 60% to 80% of women. The greatest risk of neonatal infection occurs when the mother has primary genital herpes involving the cervix at delivery, and the infant is premature and delivered with instrumentation (eg, scalp electrodes). More than 80% of neonates with herpes will have typical herpetic lesions of the skin, eye, or mouth, and most of the remainder will have either encephalitis or a sepsis syndrome with pneumonitis and hepatitis and negative bacterial cultures. Because herpes can mimic other neonatal infections, laboratory diagnosis is important, using cultures of the virus from lesions, peripheral blood white cells, or CSF. Treatment with intravenous acyclovir does reduce mortality and neurologic sequelae, but outcome is still guarded in babies with disseminated disease or encephalitis. Prevention focuses on caesarean section in women with active lesions at the time of impending delivery and avoidance of postnatal exposure. Further studies are needed to determine whether maternal screening (eg, HSV-2 type specific antibodies and vaginal cultures in selected women at delivery) will be cost effective in preventing neonatal herpes.

Genital herpes and pregnancy--preventive measures

Genital herpes is particularly dangerous during pregnancy because of the risk of neonatal infection. This is discussed in four situations of genital herpes associated with pregnancy. Choosing the most appropriate method of delivery, i.e. carrying the least risk of transmission from mother to baby, is based on our knowledge of the natural history of genital herpes infection, the risk to the newborn (estimated from epidemiological studies), and, lastly, the possible preventive measures available.

Detection of immunoglobulin M antibodies to glycoprotein G-2 by western blot (immunoblot) for diagnosis of initial herpes simplex virus type 2 genital infections

Western blots (immunoblots) for the detection of immunoglobulin M (IgM) antibodies specific for herpes simplex virus type 1 (HSV-1) and HSV-2 in patients' sera were developed. The locations of the type-specific glycoprotein G (gpG-2) of HSV-2 (92- and 140-kDa forms) and glycoprotein C of HSV-1 (gpC-1), which carries mostly type-specific antigenic epitopes, were checked with specific monoclonal antibodies. Western blot assays for IgM antibody to gpC-1 or gpG-2 were performed after depletion of IgG by precipitation with anti-human IgG. In patients with primary HSV-2 genital infections, seroconversion of IgM and IgG antibodies to both the 92- and 140-kDa forms of gpG-2 was observed, although both antibodies appeared in convalescent-phase serum after the first week. IgM and IgG antibodies to low-molecular-size polypeptides (40 to 65 kDa) were the first antibodies observed in patients with primary infection, but these antibodies were cross-reactive with HSV-1 and HSV-2. However, in patients with recurrent HSV-2 infections, IgG antibodies to both forms of gpG-2 and the low-molecular-size polypeptides were found no matter how early after onset the patient was bled, and IgM to gpG-2 did not appear. In patients with nonprimary initial genital HSV-2 infections, IgG antibody to HSV-1 was demonstrated in the first serum specimen, and HSV-2-specific IgM was found in 39% of the serum specimens. Hence, the Western blot assay can be used to test for IgM antibody to gpG-2, allowing for the retrospective diagnosis of inital HSV-2 infections and its use as a supplementary test to the gpG-2 IgG enzyme-linked immunosorbent assays developed elsewhere. In contrast, IgM antibody to gpG-2 is not usually detected in patients with recurrent HSV-2 infections.

The reliability of serological tests for the diagnosis of genital herpes: a critique

The reliability and limitations of the currently used routine tests for herpes simplex virus type 2 (HSV-2) antibody in Australia are reviewed. Six case reports illustrate the clinical dangers of overinterpretation of the currently available kits and the need for a readily available specific HSV-2 antibody test. In Sydney, HSV-2 causes approximately 85% of primary genital herpes and > 95% of recurrent genital herpes. Due to the extensive serological cross-reactivity between HSV-1 and HSV-2, currently available "type specific" commercial assays cannot reliably distinguish between the 2. Isolation of herpes simplex virus (HSV) or detection of HSV antigen in vesicle fluid is the preferred diagnostic test but may be overlooked or patients may have no visible lesions. The only accurate techniques for detecting HSV-2 specific antibody are the Western blot assay and an enzymatic immunoassay using glycoprotein G (gG-2), a component of the HSV-2 envelope. These tests, which still are restricted to research laboratories can be used to accurately identify people with previous exposure to HSV-2 (IgG) or to diagnose primary infection where virus isolation has not been performed or is impossible. Current commercially available antibody tests may have extensive cross-reactivity.

Herpes simplex virus infection in pregnancy

Genital infections in pregnancy caused by herpes simplex virus types 1 and 2 are a difficult management problem. Both primary and recurrent genital herpes can range from severe, extensive ulceration to asymptomatic virus shedding. Although neonatal herpes is a well recognized complication of symptomatic maternal primary genital infection at the time of delivery, most cases are associated with asymptomatic virus shedding and absence of a history of genital herpes. Neonatal herpes may also be acquired in utero and in the postnatal period. The diagnosis of herpes simplex infection is made most reliably by virus isolation or antigen detection from samples obtained from clinically apparent lesions. Serology is useful for diagnosing primary herpes, and newer serological techniques allow the detection of HSV-2 specific antibodies. Strategies to prevent neonatal herpes are limited by the failure of currently available diagnostic tests to rapidly detect women in labour who are at risk of transmitting herpes, by the absence of proven antenatal screening tests for HSV, and by transmission of herpes to neonates from asymptomatic mothers. The most useful current strategy is careful examination of the vulva and cervix for herpes lesions in women coming to labour. Caesarean section is indicated in women with clinically apparent genital herpes at delivery. Effective and safe antiviral agents are available for treatment of maternal and neonatal herpes.