A retrospective survey of HIV drug resistance among patients 1 year after initiation of antiretroviral therapy at 4 clinics in Malawi

In 2004, Malawi began scaling up its national antiretroviral therapy (ART) program. Because of limited treatment options, population-level surveillance of acquired human immunodeficiency virus drug resistance (HIVDR) is critical to ensuring long-term treatment success. The World Health Organization target for clinic-level HIVDR prevention at 12 months after ART initiation is ≥ 70%. In 2007, viral load and HIVDR genotyping was performed in a retrospective cohort of 596 patients at 4 ART clinics. Overall, HIVDR prevention (using viral load ≤ 400 copies/mL) was 72% (95% confidence interval [CI], 67%-77%; range by site, 60%-83%) and detected HIVDR was 3.4% (95% CI, 1.8%-5.8%; range by site, 2.5%-4.7%). Results demonstrate virological suppression and HIVDR consistent with previous reports from sub-Saharan Africa. High rates of attrition because of loss to follow-up were noted and merit attention.

HIV drug resistance early warning indicators in cohorts of individuals starting antiretroviral therapy between 2004 and 2009: World Health Organization global report from 50 countries

The World Health Organization developed a set of human immunodeficiency virus drug resistance (HIVDR) early warning indicators (EWIs) to assess antiretroviral therapy clinic and program factors associated with HIVDR. EWIs are monitored by abstracting data routinely recorded in clinical records, and the results enable clinics and program managers to identify problems that should be addressed to minimize preventable emergence of HIVDR in clinic populations. As of June 2011, 50 countries monitored EWIs, covering 131 686 patients initiating antiretroviral treatment between 2004 and 2009 at 2107 clinics. HIVDR prevention is associated with patient care (appropriate prescribing and patient monitoring), patient behavior (adherence), and clinic/program management efforts to reduce treatment interruptions (follow up, retention on first-line ART, procurement and supply management of antiretroviral drugs). EWIs measure these factors and the results have been used to optimize patient and population treatment outcomes.

Update on World Health Organization HIV drug resistance prevention and assessment strategy: 2004-2011

The HIV drug resistance (HIVDR) prevention and assessment strategy, developed by the World Health Organization (WHO) in partnership with HIVResNet, includes monitoring of HIVDR early warning indicators, surveys to assess acquired and transmitted HIVDR, and development of an accredited HIVDR genotyping laboratory network to support survey implementation in resource-limited settings. As of June 2011, 52 countries had implemented at least 1 element of the strategy, and 27 laboratories had been accredited. As access to antiretrovirals expands under the WHO/Joint United Nations Programme on HIV/AIDS Treatment 2.0 initiative, it is essential to strengthen HIVDR surveillance efforts in the face of increasing concern about HIVDR emergence and transmission.

Monitoring of early warning indicators for HIV drug resistance in antiretroviral therapy clinics in Zimbabwe

Monitoring human immunodeficiency virus drug resistance (HIVDR) early warning indicators (EWIs) can help national antiretroviral treatment (ART) programs to identify clinic factors associated with HIVDR emergence and provide evidence to support national program and clinic-level adjustments, if necessary. World Health Organization-recommended HIVDR EWIs were monitored in Zimbabwe using routinely available data at selected ART clinics between 2007 and 2009. As Zimbabwe's national ART coverage increases, improved ART information systems are required to strengthen routine national ART monitoring and evaluation and facilitate scale-up of HIVDR EWI monitoring. Attention should be paid to minimizing loss to follow-up, supporting adherence, and ensuring clinic-level drug supply continuity.

World Health Organization generic protocol to assess drug-resistant HIV among children <18 months of age and newly diagnosed with HIV in resource-limited countries

Increased use of nonnucleoside reverse transcriptase inhibitors (NNRTIs) in pregnant and breastfeeding women will result in fewer children infected with human immunodeficiency virus (HIV). However, among children infected despite prevention of mother-to-child transmission (PMTCT), a substantial proportion will acquire NNRTI-resistant HIV, potentially compromising response to NNRTI-based antiretroviral therapy (ART). In countries scaling up PMTCT and pediatric ART programs, it is crucial to assess the proportion of young children with drug-resistant HIV to improve health outcomes and support national and global decision making on optimal selection of pediatric first-line ART. This article summarizes a new World Health Organization surveillance protocol to assess resistance using remnant dried blood spot specimens from a representative sample of children aged <18 months being tested for early infant diagnosis.

Drug resistance mutations for surveillance of transmitted HIV-1 drug-resistance: 2009 update

Programs that monitor local, national, and regional levels of transmitted HIV-1 drug resistance inform treatment guidelines and provide feedback on the success of HIV-1 treatment and prevention programs. To accurately compare transmitted drug resistance rates across geographic regions and times, the World Health Organization has recommended the adoption of a consensus genotypic definition of transmitted HIV-1 drug resistance. In January 2007, we outlined criteria for developing a list of mutations for drug-resistance surveillance and compiled a list of 80 RT and protease mutations meeting these criteria (surveillance drug resistance mutations; SDRMs). Since January 2007, several new drugs have been approved and several new drug-resistance mutations have been identified. In this paper, we follow the same procedures described previously to develop an updated list of SDRMs that are likely to be useful for ongoing and future studies of transmitted drug resistance. The updated SDRM list has 93 mutations including 34 NRTI-resistance mutations at 15 RT positions, 19 NNRTI-resistance mutations at 10 RT positions, and 40 PI-resistance mutations at 18 protease positions.

Minority HIV-1 drug resistance mutations are present in antiretroviral treatment-naïve populations and associate with reduced treatment efficacy

BACKGROUND

Transmitted HIV-1 drug resistance can compromise initial antiretroviral therapy (ART); therefore, its detection is important for patient management. The absence of drug-associated selection pressure in treatment-naïve persons can cause drug-resistant viruses to decline to levels undetectable by conventional bulk sequencing (minority drug-resistant variants). We used sensitive and simple tests to investigate evidence of transmitted drug resistance in antiretroviral drug-naïve persons and assess the clinical implications of minority drug-resistant variants.

METHODS AND FINDINGS

We performed a cross-sectional analysis of transmitted HIV-1 drug resistance and a case-control study of the impact of minority drug resistance on treatment response. For the cross-sectional analysis, we examined viral RNA from newly diagnosed ART-naïve persons in the US and Canada who had no detectable (wild type, n = 205) or one or more resistance-related mutations (n = 303) by conventional sequencing. Eight validated real-time PCR-based assays were used to test for minority drug resistance mutations (protease L90M and reverse transcriptase M41L, K70R, K103N, Y181C, M184V, and T215F/Y) above naturally occurring frequencies. The sensitive real-time PCR testing identified one to three minority drug resistance mutation(s) in 34/205 (17%) newly diagnosed persons who had wild-type virus by conventional genotyping; four (2%) individuals had mutations associated with resistance to two drug classes. Among 30/303 (10%) samples with bulk genotype resistance mutations we found at least one minority variant with a different drug resistance mutation. For the case-control study, we assessed the impact of three treatment-relevant drug resistance mutations at baseline from a separate group of 316 previously ART-naïve persons with no evidence of drug resistance on bulk genotype testing who were placed on efavirenz-based regimens. We found that 7/95 (7%) persons who experienced virologic failure had minority drug resistance mutations at baseline; however, minority resistance was found in only 2/221 (0.9%) treatment successes (Fisher exact test, p = 0.0038).

CONCLUSIONS

These data suggest that a considerable proportion of transmitted HIV-1 drug resistance is undetected by conventional genotyping and that minority mutations can have clinical consequences. With no treatment history to help guide therapies for drug-naïve persons, the findings suggest an important role for sensitive baseline drug resistance testing.

Outcomes from monitoring of patients on antiretroviral therapy in resource-limited settings with viral load, CD4 cell count, or clinical observation alone: a computer simulation model

BACKGROUND

In lower-income countries, WHO recommends a population-based approach to antiretroviral treatment with standardised regimens and clinical decision making based on clinical status and, where available CD4 cell count, rather than viral load. Our aim was to study the potential consequences of such monitoring strategies, especially in terms of survival and resistance development.

METHODS

A validated computer simulation model of HIV infection and the effect of antiretroviral therapy was used to compare survival, use of second-line regimens, and development of resistance that result from different strategies-based on viral load, CD4 cell count, or clinical observation alone-for determining when to switch people starting antiretroviral treatment with the WHO-recommended first-line regimen of stavudine, lamivudine, and nevirapine to second-line antiretroviral treatment.

FINDINGS

Over 5 years, the predicted proportion of potential life-years survived was 83% with viral load monitoring (switch when viral load >500 copies per mL), 82% with CD4 cell count monitoring (switch at 50% drop from peak), and 82% with clinical monitoring (switch when two new WHO stage 3 events or a WHO stage 4 event occur). Corresponding values over 20 years were 67%, 64%, and 64%. Findings were robust to variations in model specification in extensive univariable and multivariable sensitivity analyses. Although survival was slightly longer with viral load monitoring, this strategy was not the most cost effective.

INTERPRETATION

For patients on the first-line regimen of stavudine, lamivudine, and nevirapine the benefits of viral load or CD4 cell count monitoring over clinical monitoring alone are modest. Development of cheap and robust versions of these assays is important, but widening access to antiretrovirals-with or without laboratory monitoring-is currently the highest priority.

World Health Organization surveys to monitor HIV drug resistance prevention and associated factors in sentinel antiretroviral treatment sites

The World Health Organization (WHO) estimates that >2 million people will have started antiretroviral therapy (ART) by the end of 2006. As the development of some HIV drug resistance (HIVDR) is inevitable in populations taking ART, the emergence of HIVDR must be balanced against the benefits of providing ART, including improved health outcomes and decreased HIV/AIDS-associated morbidity and mortality. ART programmes should operate to minimize the emergence of HIVDR in populations receiving therapy and HIVDR itself must be monitored to ensure ongoing regimen efficacy. ART regimens in resource-limited settings are usually selected at the national level following a public health approach: generally only one first-line regimen with alternate regimen(s) incorporating within-class drug substitutions are available in the public sector. The WHO has developed a population-based HIVDR assessment and prevention strategy, which includes standardized HIVDR monitoring surveys in populations receiving first-line ART at sentinel sites. The WHO surveys monitor HIVDR prevention in sentinel sites by utilizing a standardized, minimum-resource prospective survey methodology to assess the success of adult and paediatric ART sites in preventing HIVDR emergence during the first year of ART. The surveys also identify associated factors that can be addressed at the level of the ART site or programme. WHO HIVDR monitoring surveys are designed to be integrated easily into a country's ongoing, routine HIV-related evaluation activities. Performed regularly at representative sites, the data generated will inform evidence-based decision making regarding national and global ART regimen selection and minimize the emergence of HIVDR at a population level.

Antiretroviral drug resistance surveillance among drug-naive HIV-1-infected individuals in Gauteng Province, South Africa in 2002 and 2004

Background

Surveillance for transmitted HIV-1 drug resistance was conducted among drug-naive HIV-1-infected pregnant women in South Africa, where single-dose nevirapine has been in use since 2001 and a national antiretroviral treatment programme started in 2004.

Methods

All subjects were from the Gauteng Province and were part of the 2002 and 2004 annual antenatal HIV seroprevalence survey conducted by the South African National Department of Health. All subjects met the inclusion criteria as set out by the World Health Organisation guidelines for HIV-1 transmitted drug resistance surveillance (women <22 years of age and in first pregnancy). Genotyping was performed on viral RNA by sequencing the protease and reverse transcriptase genes. Samples were also tested for the K103N mutation using a highly sensitive allele-specific realtime PCR assay (AS-PCR).

Results

Of 128 eligible participants from 2002, 65 (51%) samples were successfully amplified. None of them had evidence of resistance mutations by genotyping or by AS-PCR. Of 117 eligible participants from 2004, 48 (41%) samples were successfully amplified. Of these, one had T69D and one had the K70R resistance mutation, to give a total of 2/48 (4.2%) participants with evidence of resistance mutations by genotyping. One sample that was wild-type by genotyping was positive for K103N by AS-PCR. All samples clustered phylogenetically with HIV-1 subtype C, the predominant subtype circulating in South Africa.

Conclusions

Using the threshold survey, resistance prevalence overall and for each drug class in 2002 and 2004 was <5% for the Gauteng province of South Africa. The detection of a low frequency of resistance mutations in the 2004 survey suggests that surveillance should be conducted annually among untreated populations to determine if this increases with time.

HIV drug resistance threshold survey using specimens from voluntary counselling and testing sites in Hanoi, Vietnam

Background

In countries where antiretroviral therapy has been available or is being rapidly expanded, the World Health Organization (WHO) recommends surveillance for transmitted HIV drug resistance (HIVDR) by threshold surveillance methods using specimens from antenatal clinics or voluntary counselling and testing (VCT) sites. The aim of this study was to implement the HIVDR threshold survey in VCT sites in Vietnam, where HIV prevalence is high. Estimating transmitted resistance in the infected population will enable the appropriateness of current antiretroviral drug regimens to be assessed and will inform plans for future HIVDR surveillance.

Methods

Consecutive blood specimens were collected from 70 newly diagnosed HIV-positive clients 18–24 years of age at two sites in Hanoi, Vietnam. Informed consent and serum specimens were obtained from each eligible client, with serum frozen at -70°C until shipping to Thailand for resistance testing using the TruGene system.

Results

From February until August 2006, 559 clients were eligible to participate in this survey. Of the 535 clients (95.7%) who agreed to participate, 70 (13%) were HIV-positive and were included in the survey. Of the 70 specimens sent for genotyping, 52 consecutive samples were amplified, 49 of which could be genotyped. Only 1 of 49 genotyped specimens had mutations associated with drug resistance (L74V and Y181C) in the reverse transcriptase gene, indicating that the prevalence of transmitted HIVDR to all drugs and drug classes evaluated was <5%.

Conclusion

The prevalence of transmitted HIVDR was low in Hanoi as determined using threshold surveillance methods. The Ministry of Health plans to repeat this survey methodology in one more province and to confirm these findings by expanded HIVDR surveillance.

Recommendations for surveillance of transmitted HIV drug resistance in countries scaling up antiretroviral treatment

Background

The World Health Organization (WHO) HIV drug resistance (HIVDR) threshold survey method was developed for surveillance of transmitted HIVDR in resource-limited countries. The method is being implemented with minimal resources as a routine public health activity to produce comparable results in multiple countries and areas within countries. Transmitted drug resistant HIV strains will be seen first in cities or health districts where antiretroviral treatment (ART) has been widely available for years. WHO recommends countries begin surveillance in these areas.

Methods

Each survey requires ≤47 specimens from individuals consecutively diagnosed with HIV to categorize resistance to each relevant drug class as <5%, 5–15% or >15%. Use of routinely collected information and remnant specimens is recommended to minimize costs. Site and individual eligibility criteria are designed to minimize inclusion of ARV-experienced individuals and individuals infected before ART was available.

Results

Surveys have been implemented in 21 countries. In this supplement, seven countries report results of <5% transmitted HIVDR in areas where ART has been available for the longest time period. The main challenges in implementation are acquiring sufficient numbers of eligible specimens and optimizing specimen handling.

Conclusion

The WHO HIVDR threshold survey method is feasible in resource-limited countries and produces information relevant to ART and drug resistance prevention planning.

Surveillance of transmitted HIV drug resistance in the Manzini-Mbabane corridor, Swaziland, in 2006

Background

In resource-limited settings where anti-retroviral treatment (ART) is being scaled-up, the World Health Organization (WHO) recommends the surveillance of transmitted HIV drug resistance (HIVDR). We used the WHO's HIVDR threshold survey method to assess transmitted HIVDR in three antenatal clinic (ANC) sites along the corridor between the two most populous cities in Swaziland, where ART was introduced in 2003.

Methods

From July–August 2006, remnant sera were aliquoted from HIV serosurvey specimens collected from 70 primagravidas <25 years old attending ANC during the national HIV serosurvey. Genotyping was performed at the National Institute for Communicable Diseases, South Africa. Transmitted resistance was defined by the WHO's surveillance list of mutations. HIVDR prevalence was categorized using the WHO's threshold survey binomial sequential sampling method.

Results

Among the 70 eligible specimens, 61 were sequenced – 60 (98%) were identified as subtype C and one as subtype B. No major nucleoside or non-nucleoside reverse transcriptase inhibitor mutations occurred among the first 34 consecutive specimens, which supported a transmitted resistance categorization to these drug classes as <5%. One protease inhibitor mutation, M46I, was seen among the first 44 specimens, supporting a categorization of PI resistance as <5%.

Conclusion

Our survey indicates that prevalence of transmitted HIVDR among recently infected pregnant women along the Manzini-Mbabane corridor is low (<5%). Surveys will be carried out in this area biannually and may be extended to other areas. Surveys for transmitted resistance make up one element among a spectrum of activities to assess and support minimization of HIVDR.

A novel sequential sampling technique for the surveillance of transmitted HIV drug resistance by cross-sectional survey for use in low resource settings

This article describes the development of a novel sequential sampling method for the surveillance of transmitted HIV drug resistance by cross-sectional survey. Two commonly used sequential sampling methods are described and their applicability to the problem of classifying the prevalence of transmitted HIV drug resistance investigated. Both methods are rejected due to insufficient savings in sample size and operational complexity. A novel method is proposed and this is tested using computer-based simulation. This method provides useful sample size savings and operational simplicity and could provide the basis for a rapid and reliable survey method for classifying the prevalence of transmitted HIV drug resistance in circumstances where monitoring HIV drug resistance is an important issue, but resources do not allow full-scale surveillance to be established. The method is currently being used in several such settings.

Surveillance of transmitted HIV drug resistance among women attending antenatal clinics in Dar es Salaam, Tanzania

Background

In resource-limited settings where antiretroviral treatment (ART) access is being scaled-up, the World Health Organization (WHO) recommends surveillance of transmitted HIV drug resistance (HIVDR). We used the WHO HIVDR threshold survey method to assess transmitted HIVDR in Dar es Salaam where ART was introduced in 1995 and where ∼11,000 people are currently on ART.

Methods

From November 2005 to February 2006, dried blood spot (DBS) specimens were made from remnant specimens collected during the national HIV serosurvey from 60 primagravidas <25 years old attending six antenatal clinics for routine syphilis testing. Genotyping was performed at the Centers for Disease Control and Prevention, Atlanta, Georgia, USA. Protease and reverse transcriptase drug resistance mutations were identified using the Stanford University HIV drug resistance database. We used the National Institutes of Health genotyping tool for HIV-1 subtyping. HIVDR prevalence categorization was based on the WHO threshold survey binomial sequential sampling method.

Results

Among the 60 eligible specimens collected, 50 DBS were successfully amplified using RT-PCR. Sequencing was performed on the first 39 specimens: 13 (33.3%) were subtype A1, 13 (33.3%) subtype C, and 4 (10.3%) subtype D, the remainder differed in the closest subtype based on protease versus reverse transcriptase. No resistance mutations were seen; HIVDR to all drug classes was categorized as <5%.

Conclusions

Our survey indicates that prevalence of transmitted HIVDR among recently infected pregnant women in Dar es Salaam is low (<5%). The survey should be repeated during the next HIV sentinel survey in Dar es Salaam and extended to other regions where ART is being scaled up.

The World Health Organization's global strategy for prevention and assessment of HIV drug resistance

Antiretroviral treatment (ART) for HIV is being scaled up rapidly in resource-limited countries. Treatment options are simplified and standardized, generally with one potent first-line regimen and one potent alternate first-line regimen recommended. Widespread HIV drug resistance (HIVDR) was initially feared, but reports from resource-limited countries suggest that initial ART programmes are as effective as in resource-rich countries, which should limit HIV drug resistance if programme effectiveness continues during scale-up. ART interruptions must be minimized to maintain viral suppression on the first-line regimen for as long as possible. Lack of availability of appropriate second-line drugs is a concern, as is the additional accumulation of resistance mutations in the absence of viral load testing to determine failure. The World Health Organization (WHO) recommends a minimum-resource strategy for prevention and assessment of HIVDR in resource-limited countries. The WHO's Global Network HIVResNet provides standardized tools, training, technical assistance, laboratory quality assurance, analysis of results and recommendations for guidelines and public health action. National strategies focus on assessments to guide immediate public health action to improve ART programme effectiveness in minimizing HIVDR and to guide regimen selection. Globally, WHO HIVResNet collects and analyses data to support evidence-based international policies and guidelines. Financial support is provided by major international organizations and technical support from HIVDR experts worldwide. As of December 2007, 25 countries were planning or implementing the strategy; seven countries report results in this supplement.

Recommendations for surveillance of transmitted HIV drug resistance in countries scaling up antiretroviral treatment

BACKGROUND

The World Health Organization (WHO) HIV drug resistance (HIVDR) threshold survey method was developed for surveillance of transmitted HIVDR in resource-limited countries. The method is being implemented with minimal resources as a routine public health activity to produce comparable results in multiple countries and areas within countries. Transmitted drug resistant HIV strains will be seen first in cities or health districts where antiretroviral treatment (ART) has been widely available for years. WHO recommends countries begin surveillance in these areas.

METHODS

Each survey requires < or =47 specimens from individuals consecutively diagnosed with HIV to categorize resistance to each relevant drug class as <5%, 5-15% or >15%. Use of routinely collected information and remnant specimens is recommended to minimize costs. Site and individual eligibility criteria are designed to minimize inclusion of ARV-experienced individuals and individuals infected before ART was available.

RESULTS

Surveys have been implemented in 21 countries. In this supplement, seven countries report results of <5% transmitted HIVDR in areas where ART has been available for the longest time period. The main challenges in implementation are acquiring sufficient numbers of eligible specimens and optimizing specimen handling.

CONCLUSION

The WHO HIVDR threshold survey method is feasible in resource-limited countries and produces information relevant to ART and drug resistance prevention planning.

Consensus drug resistance mutations for epidemiological surveillance: basic principles and potential controversies

Programmes that monitor local, national and regional levels of transmitted HIV-1 drug resistance inform treatment guidelines and provide feedback on the success of HIV-1 treatment and prevention programmes. The World Health Organization (WHO) has established a global programme for genotypic surveillance of HIV-1 drug resistance and has recommended the adoption of a consensus definition of genotypic drug resistance. Such a definition is necessary to accurately compare transmitted drug resistance rates across geographical regions and time periods. HIV-1 diversity and the large number of mutations associated with antiretroviral drug resistance complicate the development of a consensus definition for genotypic drug resistance. This paper reviews the data that must be considered to determine which of the many HIV-1 drug resistance mutations are likely to be both sensitive and specific indicators of transmitted drug resistance. The process used to create a previously published list of drug resistance mutations for HIV-1 surveillance is reviewed and alternative approaches to this process are discussed.

World Health Organization surveys to monitor HIV drug resistance prevention and associated factors in sentinel antiretroviral treatment sites

The World Health Organization (WHO) estimates that >2 million people will have started antiretroviral therapy (ART) by the end of 2006. As the development of some HIV drug resistance (HIVDR) is inevitable in populations taking ART, the emergence of HIVDR must be balanced against the benefits of providing ART, including improved health outcomes and decreased HIV/AIDS-associated morbidity and mortality. ART programmes should operate to minimize the emergence of HIVDR in populations receiving therapy and HIVDR itself must be monitored to ensure ongoing regimen efficacy. ART regimens in resource-limited settings are usually selected at the national level following a public health approach: generally only one first-line regimen with alternate regimen(s) incorporating within-class drug substitutions are available in the public sector. The WHO has developed a population-based HIVDR assessment and prevention strategy, which includes standardized HIVDR monitoring surveys in populations receiving first-line ART at sentinel sites. The WHO surveys monitor HIVDR prevention in sentinel sites by utilizing a standardized, minimum-resource prospective survey methodology to assess the success of adult and paediatric ART sites in preventing HIVDR emergence during the first year of ART. The surveys also identify associated factors that can be addressed at the level of the ART site or programme. WHO HIVDR monitoring surveys are designed to be integrated easily into a country's ongoing, routine HIV-related evaluation activities. Performed regularly at representative sites, the data generated will inform evidence-based decision making regarding national and global ART regimen selection and minimize the emergence of HIVDR at a population level.

The World Health Organization's global strategy for prevention and assessment of HIV drug resistance

Antiretroviral treatment (ART) for HIV is being scaled up rapidly in resource-limited countries. Treatment options are simplified and standardized, generally with one potent first-line regimen and one potent alternate first-line regimen recommended. Widespread HIV drug resistance (HIVDR) was initially feared, but reports from resource-limited countries suggest that initial ART programmes are as effective as in resource-rich countries, which should limit HIV drug resistance if programme effectiveness continues during scale-up. ART interruptions must be minimized to maintain viral suppression on the first-line regimen for as long as possible. Lack of availability of appropriate second-line drugs is a concern, as is the additional accumulation of resistance mutations in the absence of viral load testing to determine failure. The World Health Organization (WHO) recommends a minimum-resource strategy for prevention and assessment of HIVDR in resource-limited countries. The WHO's Global Network HIVResNet provides standardized tools, training, technical assistance, laboratory quality assurance, analysis of results and recommendations for guidelines and public health action. National strategies focus on assessments to guide immediate public health action to improve ART programme effectiveness in minimizing HIVDR and to guide regimen selection. Globally, WHO HIVResNet collects and analyses data to support evidence-based international policies and guidelines. Financial support is provided by major international organizations and technical support from HIVDR experts worldwide. As of December 2007, 25 countries were planning or implementing the strategy; seven countries report results in this supplement.

HIV drug resistance threshold survey using specimens from voluntary counselling and testing sites in Hanoi, Vietnam

BACKGROUND

In countries where antiretroviral therapy has been available or is being rapidly expanded, the World Health Organization (WHO) recommends surveillance for transmitted HIV drug resistance (HIVDR) by threshold surveillance methods using specimens from antenatal clinics or voluntary counselling and testing (VCT) sites. The aim of this study was to implement the HIVDR threshold survey in VCT sites in Vietnam, where HIV prevalence is high. Estimating transmitted resistance in the infected population will enable the appropriateness of current antiretroviral drug regimens to be assessed and will inform plans for future HIVDR surveillance.

METHODS

Consecutive blood specimens were collected from 70 newly diagnosed HIV-positive clients 18-24 years of age at two sites in Hanoi, Vietnam. Informed consent and serum specimens were obtained from each eligible client, with serum frozen at -70 degrees C until shipping to Thailand for resistance testing using the TruGene system.

RESULTS

From February until August 2006, 559 clients were eligible to participate in this survey. Of the 535 clients (95.7%) who agreed to participate, 70 (13%) were HIV-positive and were included in the survey. Of the 70 specimens sent for genotyping, 52 consecutive samples were amplified, 49 of which could be genotyped. Only 1 of 49 genotyped specimens had mutations associated with drug resistance (L74V and Y181C) in the reverse transcriptase gene, indicating that the prevalence of transmitted HIVDR to all drugs and drug classes evaluated was <5%.

CONCLUSION

The prevalence of transmitted HIVDR was low in Hanoi as determined using threshold surveillance methods. The Ministry of Health plans to repeat this survey methodology in one more province and to confirm these findings by expanded HIVDR surveillance.

A novel sequential sampling technique for the surveillance of transmitted HIV drug resistance by cross-sectional survey for use in low resource settings

This article describes the development of a novel sequential sampling method for the surveillance of transmitted HIV drug resistance by cross-sectional survey. Two commonly used sequential sampling methods are described and their applicability to the problem of classifying the prevalence of transmitted HIV drug resistance investigated. Both methods are rejected due to insufficient savings in sample size and operational complexity. A novel method is proposed and this is tested using computer-based simulation. This method provides useful sample size savings and operational simplicity and could provide the basis for a rapid and reliable survey method for classifying the prevalence of transmitted HIV drug resistance in circumstances where monitoring HIV drug resistance is an important issue, but resources do not allow fullscale surveillance to be established. The method is currently being used in several such settings.

Surveillance of transmitted HIV drug resistance among women attending antenatal clinics in Dar es Salaam, Tanzania

BACKGROUND

In resource-limited settings where antiretroviral treatment (ART) access is being scaled-up, the World Health Organization (WHO) recommends surveillance of transmitted HIV drug resistance (HIVDR). We used the WHO HIVDR threshold survey method to assess transmitted HIVDR in Dar es Salaam where ART was introduced in 1995 and where approximately 11,000 people are currently on ART.

METHODS

From November 2005 to February 2006, dried blood spot (DBS) specimens were made from remnant specimens collected during the national HIV serosurvey from 60 primagravidas <25 years old attending six antenatal clinics for routine syphilis testing. Genotyping was performed at the Centers for Disease Control and Prevention, Atlanta, Georgia, USA. Protease and reverse transcriptase drug resistance mutations were identified using the Stanford University HIV drug resistance database. We used the National Institutes of Health genotyping tool for HIV-1 subtyping. HIVDR prevalence categorization was based on the WHO threshold survey binomial sequential sampling method.

RESULTS

Among the 60 eligible specimens collected, 50 DBS were successfully amplified using RT-PCR. Sequencing was performed on the first 39 specimens: 13 (33.3%) were subtype A1, 13 (33.3%) subtype C, and 4 (10.3%) subtype D, the remainder differed in the closest subtype based on protease versus reverse transcriptase. No resistance mutations were seen; HIVDR to all drug classes was categorized as <5%.

CONCLUSIONS

Our survey indicates that prevalence of transmitted HIVDR among recently infected pregnant women in Dar es Salaam is low (<5/%). The survey should be repeated during the next HIV sentinel survey in Dar es Salaam and extended to other regions where ART is being scaled up.

Surveillance of transmitted HIV drug resistance in the Manzini-Mbabane corridor, Swaziland, in 2006

BACKGROUND

In resource-limited settings where antiretroviral treatment (ART) is being scaled-up, the World Health Organization (WHO) recommends the surveillance of transmitted HIV drug resistance (HIVDR). We used the WHO's HIVDR threshold survey method to assess transmitted HIVDR in three antenatal clinic (ANC) sites along the corridor between the two most populous cities in Swaziland, where ART was introduced in 2003.

METHODS

From July-August 2006, remnant sera were aliquoted from HIV serosurvey specimens collected from 70 primagravidas <25 years old attending ANC during the national HIV serosurvey. Genotyping was performed at the National Institute for Communicable Diseases, South Africa. Transmitted resistance was defined by the WHO's surveillance list of mutations. HIVDR prevalence was categorized using the WHO's threshold survey binomial sequential sampling method.

RESULTS

Among the 70 eligible specimens, 61 were sequenced--60 (98%) were identified as subtype C and one as subtype B. No major nucleoside or non-nucleoside reverse transcriptase inhibitor mutations occurred among the first 34 consecutive specimens, which supported a transmitted resistance categorization to these drug classes as <5%. One protease inhibitor mutation, M461, was seen among the first 44 specimens, supporting a categorization of PI resistance as <5%.

CONCLUSION

Our survey indicates that prevalence of transmitted HIVDR among recently infected pregnant women along the Manzini-Mbabane corridor is low (<5%). Surveys will be carried out in this area biannually and may be extended to other areas. Surveys for transmitted resistance make up one element among a spectrum of activities to assess and support minimization of HIVDR.

Antiretroviral drug resistance surveillance among drug-naive HIV-1-infected individuals in Gauteng Province, South Africa in 2002 and 2004

BACKGROUND

Surveillance for transmitted HIV-1 drug resistance was conducted among drug-naive HIV-1-infected pregnant women in South Africa, where single-dose nevirapine has been in use since 2001 and a national antiretroviral treatment programme started in 2004.

METHODS

All subjects were from the Gauteng Province and were part of the 2002 and 2004 annual antenatal HIV seroprevalence survey conducted by the South African National Department of Health. All subjects met the inclusion criteria as set out by the World Health Organisation guidelines for HIV-1 transmitted drug resistance surveillance (women <22 years of age and in first pregnancy). Genotyping was performed on viral RNA by sequencing the protease and reverse transcriptase genes. Samples were also tested for the K103N mutation using a highly sensitive allele-specific real-time PCR assay (AS-PCR).

RESULTS

Of 128 eligible participants from 2002, 65 (51%) samples were successfully amplified. None of them had evidence of resistance mutations by genotyping or by AS-PCR. Of 117 eligible participants from 2004, 48 (41%) samples were successfully amplified. Of these, one had T69D and one had the K70R resistance mutation, to give a total of 2/48 (4.2%) participants with evidence of resistance mutations by genotyping. One sample that was wild-type by genotyping was positive for K103N by AS-PCR. All samples clustered phylogenetically with HIV-1 subtype C, the predominant subtype circulating in South Africa.

CONCLUSIONS

Using the threshold survey, resistance prevalence overall and for each drug class in 2002 and 2004 was <5% for the Gauteng province of South Africa. The detection of a low frequency of resistance mutations in the 2004 survey suggests that surveillance should be conducted annually among untreated populations to determine if this increases with time.

Prevalence of tuberculosis infection in the United States population: the national health and nutrition examination survey, 1999-2000

RATIONALE

The goal for tuberculosis (TB) elimination in the United States is a TB disease incidence of less than 1 per million U.S. population by 2010, which requires that the latent TB infection (LTBI) prevalence be less than 1% and decreasing.

OBJECTIVES

To estimate the prevalence of LTBI in the U.S. population.

METHODS AND MEASUREMENTS

Interviews and medical examinations, including tuberculin skin testing (TST), of 7,386 individuals were conducted in 1999-2000 as part of the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the civilian, noninstitutionalized U.S. population. LTBI was defined as a TST measurement of >/=10 mm. Associations of age, race/ethnicity, sex, poverty, and birthplace were assessed. Results among the 24- to 74-year-old subgroup were compared with NHANES 1971-1972 data.

MEASUREMENTS AND MAIN RESULTS

Estimated LTBI prevalence was 4.2%; an estimated 11,213,000 individuals had LTBI. Among 25- to 74-year-olds, prevalence decreased from 14.3% in 1971-1972 to 5.7% in 1999-2000. Higher prevalences were seen in the foreign born (18.7%), non-Hispanic blacks/African Americans (7.0%), Mexican Americans (9.4%), and individuals living in poverty (6.1%). A total of 63% of LTBI was among the foreign born. Among the U.S. born, after adjusting for confounding factors, LTBI was associated with non-Hispanic African-American race/ethnicity, Mexican American ethnicity, and poverty. A total of 25.5% of persons with LTBI had been previously diagnosed as having LTBI or TB, and only 13.2% had been prescribed treatment.

CONCLUSIONS

In addition to basic TB control measures, elimination strategies should include targeted evaluation and treatment of individuals in high-prevalence groups, as well as enhanced support for global TB prevention and control.

The requirement for surveillance of HIV drug resistance within antiretroviral rollout in the developing world

PURPOSE OF REVIEW

To describe surveillance measures to inform HIV drug-resistance prevention, as part of the public health approach to antiretroviral therapy in developing countries.

RECENT FINDINGS

Neither HIV drug-resistance transmission nor its emergence in treatment is routinely assessed in the developing world, but routine methods should be part of antiretroviral therapy scale-up. Mathematical modelling and experience in resource-rich countries suggest HIV drug-resistance transmission will increase as antiretroviral therapy coverage increases, but its rise will be limited initially. Transmission surveys should begin in geographic areas in each country where antiretroviral therapy coverage is widespread. Reports from resource-limited countries suggest that antiretroviral therapy programs are as effective as in resource-rich countries, which should limit HIV drug resistance if effectiveness is maintained with antiretroviral therapy expansion. Surveillance of HIV drug resistance emerging in treatment and other factors will support implementation of prevention measures on a population level.

SUMMARY

Standardized surveillance of transmitted and treatment-associated HIV drug resistance is critical to the success of antiretroviral therapy expansion in developing countries. Routine assessment of prescribing practices, availability of and access to appropriate regimens for adults and children, antiretroviral drug supply continuity, and measures to prevent HIV transmission will supply critical information for HIV drug-resistance prevention.

Identifying the sources of tuberculosis in young children: a multistate investigation

To better understand the molecular epidemiology of tuberculosis (TB) transmission for culture-confirmed patients <5 years of age, data were analyzed from a population-based study conducted in seven U.S. sites from 1996 to 2000. Mycobacterium tuberculosis isolates were genotyped with IS6110-based restriction fragment length polymorphism analysis and spoligotyping. Case-patient data were obtained from the Centers for Disease Control and Prevention s national tuberculosis registry and health department records. Routine public health investigations conducted by local health departments identified suspected source patients for 57 (51%) of 111 culture-confirmed patients <5 years of age. For 8 (15%) of 52 culture-confirmed patients <5 years of age and their suspected source patients with complete genotyping results, genotypes suggested infection with different TB strains. Potential differences between sources for patients <5 years of age and source patients that transmitted TB to adolescent and adult patients were identified.

DNA fingerprinting of Mycobacterium tuberculosis isolates from epidemiologically linked case pairs

DNA fingerprinting was used to evaluate epidemiologically linked case pairs found during routine tuberculosis (TB) contact investigations in seven sentinel sites from 1996 to 2000. Transmission was confirmed when the DNA fingerprints of source and secondary cases matched. Of 538 case pairs identified, 156 (29%) did not have matching fingerprints. Case pairs from the same household were no more likely to have confirmed transmission than those linked elsewhere. Case pairs with unconfirmed transmission were more likely to include a smear-negative source case (odds ratio [OR] 2.0) or a foreign-born secondary case (OR 3.4) and less likely to include a secondary case <15 years old (OR 0.3). Our study suggests that contact investigations should focus not only on the household but also on all settings frequented by an index case. Foreign-born persons with TB may have been infected previously in high-prevalence countries; screening and preventive measures recommended by the Institute of Medicine could prevent TB reactivation in these cases.

Effect of liposomal composition on photoactivated liposome fusion

Bennett and O'Brien [(1995) Biochemistry 34, 3102] showed that the ultraviolet light exposure of two-component large unilamellar liposomes (LUV) composed of a 3:1 molar mixture of dioleoylphosphatidylethanolamine (DOPE) and 1,2-bis[10-(2'-hexadienoyloxy)decanoyl]-sn-glycero-3-phosphatidyl- choline (bis-SorbPC) facilitated liposome fusion. The rate and extent of liposome fusion was dependent on the extent of photopolymerization, the temperature, and the pH. Examination of the temperature dependence of fusion of photolyzed and unphotolyzed liposomes demonstrated that an enhancement of the rate of fusion occurred in the temperature range associated with the initial appearance of precursors to the inverted cubic (QII) phase [Barry et al. (1992) Biochemistry 31, 10114]. Here, the effect of the molar lipid ratio of the DOPE/bis-SorbPC liposomes on the temperature for the onset of fusion, i.e. the critical fusion temperature, was characterized by changing the relative amounts of unreactive polymorphic lipid and reactive lamellar lipid. In each case, photopolymerization of bis-SorbPC lowered the critical fusion temperature by ca. 15-20 degrees C. The photoreaction of the bis-SorbPC-containing LUV yields cross-linked poly-SorbPC, enhancing the lateral separation of the DOPE and the polylipid and causing isothermal induction of liposome fusion by lowering the temperature for the onset of fusion. Evidence is presented to support the hypothesis that the critical temperature for fusion of two LUV populations depends on the molar ratio of the monomeric lipids in heterodimers of the two LUV. This analysis indicates that the photopolymerization of appropriately designed LUV can decrease the critical fusion temperature from above to below 37 degrees C.

Molecular genetic approaches to identification, epidemiology and taxonomy of non-albicans Candida species

The reported incidence of fungal infections associated with non-albicans species from the Candida genus is increasing. Most of these infections occur in immunocompromised patients, particularly those infected with HIV. The role of molecular genetic techniques alongside the existing techniques for the identification and typing of these organisms is discussed. Species-specific genomic DNA fragments cloned from C. tropicalis and C. krusei have been developed for identification and strain typing. Analysis of tRNA profiles has been shown to be effective for the identification of C. glabrata, C. guilliermondii, C. parapsilosis and C. tropicalis. A PCR method employing primers complimentary to large ribosomal subunit genes and the lanosterol-alpha-demethylase gene has been applied for several species, including C. glabrata, C. krusei and C. tropicalis. Strain typing by comparison of genomic DNA fingerprints has been demonstrated for C. tropicalis and C. krusei following hybridisation analysis with species-specific probes. Synthetic oligonucleotide probes--which do not have to be species-specific and which can detect minor polymorphisms--have also been used for strain typing of isolates of several non-albicans species. Random amplification of polymorphic DNA (RAPD) has also been used for analysis of C. glabrata, C. lusitaniae and C. tropicalis isolates. The potential for the application of these and other techniques to Candida spp. taxonomy--and the example of a recently discovered novel species, C. dubliniensis--is discussed.

Candida dubliniensis sp. nov.: phenotypic and molecular characterization of a novel species associated with oral candidosis in HIV-infected individuals

Atypical oral Candida isolates were recovered from 60 HIV-infected and three HIV-negative individuals. These organisms were germ-tube-positive and produced abundant chlamydospores which were frequently arranged in triplets or in contiguous pairs. They belonged to C. albicans serotype A and had atypical carbohydrate assimilation profiles. Fingerprinting the genomic DNA of a selection of these organisms with the C. albicans-specific probe 27A and five separate oligonucleotides, homologous to eukaryotic microsatellite repeat sequences, demonstrated that they had a very distinct genomic organization compared to C. albicans and C. stellatoidea. This was further established by random amplified polymorphic DNA (RAPD) and karyotype analysis. Comparison of 500 bp of the V3 variable region of the large ribosomal subunit genes from nine atypical isolates and the corresponding sequences determined from C. albicans, C. stellatoidea, C. tropicalis, C. parapsilosis, C. glabrata, C. kefyr and C. krusei showed that they atypical organisms formed a homogeneous cluster (100% similarity) that was significantly different from the other Candida species analysed, but was most closely related to C. albicans and C. stellatoidea. These genetic data combined with the phenotypic characteristics of these atypical organisms strongly suggest that they constitute a novel species within the genus Candida for which the name Candida dubliniensis is proposed.

Photoactivated enhancement of liposome fusion

The photopolymerization of two-component large unilamellar liposomes (LUV) composed of 3:1 dioleoylphosphatidylethanolamine (DOPE) and either 1,2-bis[10-(2'-hexadienoyloxy)decanoyl]-sn-glycero-3-phosphatidylc holine (bis-SorbPC) or 1-palmitoyl-2-[10-(2'-hexadienoyloxy)decanoyl]-sn- glycero-3-phosphatidylcholine (mono-SorbPC) facilitated liposome fusion. Fusion was characterized by fluorescent assays for lipid mixing, aqueous contents mixing, and aqueous contents leakage. The rate and extent of the liposome fusion was dependent on the extent of photopolymerization, temperature, and the fusion initiation conditions, including the pH and the presence of Mg2+ ions. Examination of the temperature dependence of fusion for unpolymerized and polymerized liposomes showed that an enhancement of the rate of fusion occurred in the temperature range delta TI, which previous NMR studies have identified as the initial appearance of precursors to the formation of the inverted cubic phase [Barry, J. A., et al. (1992) Biochemistry 31, 10114]. The phase behavior and fusion characteristics of the DOPE/bis-SorbPC (3:1) membranes provide unequivocal evidence that liposome fusion is mediated via intermediates associated with the lamellar to QII phase transition rather than the HII phase. Photopolymerization of SorbPC-containing liposomes forms poly-SorbPC, which enhances the lateral separation of the liposome components. The formation of enriched domains of polymorphic lipids, e.g., DOPE, causes isothermal induction of fusion by lowering the critical fusion temperature of the membranes.

Oral Candida in HIV infection and AIDS: new perspectives/new approaches

Oral candidosis has become an increasingly important problem in HIV-infected individuals. At present, the small body of published literature on the characterization of the Candida strains and species found in HIV+ patients is full of confusion and contradictions. Some of these difficulties are the result of the methodological shortcomings of a number of the techniques that have been used. Examples of the problems that may be encountered on primary isolation and subculture are described and the drawbacks associated with the systems used to date for phenotyping Candida are quoted. While molecular characterization techniques would appear to offer a reliable and objective alternative, they too have their strengths and weaknesses. An attempt is made to summarize the progress that has been made recently in the detection and identification of Candida albicans and also the non-albicans species from HIV-infected individuals. What emerges is that the commensal Candida species that inhabit the oral cavities of HIV+ patients are subjected to a number of significant pressures that probably promote the selection of organisms with unusual phenotypes and genotypes. These Candida are more difficult to characterize and behave differently compared to their counterparts in HIV- individuals. It is clear that uncovering the factors that are important for the selection of treatment regimens and will be predictive of outcome will not be easy. Candida organisms are neither as benign nor as simple as once thought.

Reduced azole susceptibility of oral isolates of Candida albicans from HIV-positive patients and a derivative exhibiting colony morphology variation

Approximately 50% (15/28) of a selection of oral isolates of Candida albicans from separate individuals infected with the human immunodeficiency virus (HIV) exhibited low susceptibility to ketoconazole as determined by hyphal elongation assessment. Nine of these isolates exhibited colony morphology variation or switching at 37 degrees C, of which six expressed low ketoconazole susceptibility. To determine whether colony morphology variation could give rise to derivatives with reduced azole susceptibility, several high-frequency switching variants of three HIV-patient isolates were recovered and assessed. All but one of the variants expressed similar azole susceptibility profiles to their respective parental strains. However, the C. albicans derivative 132ACR expressed significantly reduced susceptibility to ketoconazole in comparison to its parental strain 132A. In whole cells, on the basis of total growth the switched derivative 132ACR was markedly less susceptible than its parental isolate 132A to ketoconazole at 10 microM. A much smaller difference was observed with fluconazole at 10 microM, with the switched derivative 132ACR exhibiting a threefold lower susceptibility compared with the parental isolate 132A. The incorporation of [14C]acetate in control and azole-treated cells of both organisms was higher for the parental strain. When cell lysates of strain 132A and its derivative 132ACR were incubated with [14C]mevalonic acid and ketoconazole, the IC50 for 14C-label incorporation into C-4 demethyl sterols was fivefold higher for lysates of the switched derivative 132ACR compared with those of the parental strain 132A. With fluconazole the IC50 value for the derivative 132ACR was 25-fold higher than for strain 132A. The 14-sterol demethylase of the switched derivative 132ACR was possibly less sensitive to azole inhibition than that of the enzyme of strain 132A. These studies indicated that colony morphology variation in vitro can generate derivatives with stable, reduced azole susceptibility without prior exposure to azoles.

Infants born at risk: consequences for maternal post-partum adjustment

The role of infant risk and social support as predictors of post-partum adjustment was investigated. Fifty-three mothers whose infants reflected the range of neonatal conditions were interviewed six weeks after discharge of their infant from hospital. They were assessed on measures of emotional distress, depressive symptoms, social support and perceptions of, and concerns about, their infant and themselves. The results indicated that mothers of higher risk infants reported higher levels of emotional distress and depressive symptomatology, more concerns about themselves and their baby, more difficulty in expressing affection towards their baby and greater dissatisfaction with their social support. Using multiple regression techniques, depressive symptoms were predicted by neonatal risk and dissatisfaction with social support from family and friends, while emotional distress was predicted by neonatal risk and dissatisfaction with social support from the infant's father. The study underlines the need to place more emphasis on infant variables as factors in maternal post-partum adjustment.

Exact versus asymptotic analysis for a matched case-control study

We compare exact and asymptotic methods for variable selection in matched case-control studies. Data from a study of melanoma among the employees of the Lawrence Livermore National Laboratory illustrate the comparisons. Relative to large sample methods, the exact method almost always yielded larger p-values. The differences in p-values became more pronounced with inclusion of more variables in the logistic model. Thus, when the sample size is not large, and there are many covariates under study, use of the exact method tends to select more parsimonious models and avoids overfit of the data.

Dermatitis from plastic tote boxes impregnated with an antistatic agent

An outbreak of dermatitis occurred among employees of a microelectronics firm. In a cross-sectional epidemiologic investigation, we found that dermatitis of the hands or arms had occurred among 14 of 29 (48.3%) employees of the incoming inspection department where plastic tote boxes recently purchased from one manufacturer had been used, compared to only one case among 17 (5.9%) employees in another department which had not used these boxes. Affected workers could detect an oily film on the surfaces of these new boxes, but not on older ones. We identified the oily film to be a surface accumulation of bis-hydroxyethyl-tallow amine (BHETA), an antistatic agent with which the tote boxes had been impregnated. Subsequent toxicologic investigation established that BHETA could provoke both follicular and nonfollicular irritant dermatitis, and was also a potential skin sensitizer. Antistatic agents should be considered as potential causes of dermatitis among employees who handle electrical parts transported in plastic boxes, particularly when affected employees can detect an oily film on the box surfaces.

The electronic and magnetic properties of rubredoxin: a low-temperature magnetic circular dichroism study

Oxidized rubredoxin from Clostridium pasteurianum has been investigated by magnetic circular dichroism (MCD) spectroscopy over the temperature range 1.5 to 150 K and at magnetic fields between 0 and 4.5 tesla. The results show that studies of the temperature and field dependence of MCD transitions afford insight into the polarization of electronic transitions for ground states with large g-value anisotropy, in addition to estimates of ground-state g values and zero-field splitting parameters. In agreement with the assignment made by Eaton and Lovenberg (Eaton, W.A. and Lovenberg, W. (1973) in Iron-Sulfur Proteins, Vol. II (Lovenberg, W., ed.), pp. 131-162, Academic Press, New York), the ultraviolet-visible spectrum of oxidized rubredoxin is assigned to two S----Fe(III) charge transfer transitions (both 6A1----6T2 under tetrahedral symmetry), each spanning a range of 650-430 nm and 430-330 nm, respectively. The observed splitting in each of these transitions is attributed to a predominant axial distortion in the excited state resulting in effective D2d symmetry.

Spectroscopic studies of the seven-iron-containing ferredoxins from Azotobacter vinelandii and Thermus thermophilus

The seven-iron-containing ferredoxins from Azotobacter vinelandii and Thermus thermophilus have been investigated by low-temperature magnetic circular dichroism (MCD) and electron paramagnetic resonance (EPR) spectroscopies and room temperature ultraviolet-visible absorption spectroscopy. The results confirm the presence of one trinuclear and one tetranuclear iron-sulfur cluster in both ferredoxins and facilitate comparison of the electronic and magnetic properties of the oxidized and reduced [3Fe-xS] clusters. MCD magnetization data are consistent with an S = 2 ground state for both reduced [3Fe-xS] clusters, but indicate differences in the rhombicity of the zero-field splittings. The data permit rationalization of the absence of a delta M = 4 EPR transition for the reduced [3Fe-xS] cluster in A. vinelandii ferredoxin I. Spectroscopic studies of anaerobically isolated A. vinelandii ferredoxin I do not support the hypothesis that the [3Fe-xS] cluster arises as a result of aerial oxidative damage to a [4Fe-4S] cluster during isolation. The possibility that two distinct forms of [3Fe-xS] clusters can exist in A. vinelandii ferredoxin I was investigated by spectroscopic studies as a function of pH. The results reveal two distinct and interconvertible forms of the reduced [3Fe-xS] cluster, but do not permit rationalization of the inconsistencies in the structural data that have been reported for the oxidized clusters.

Impaired left ventricular function in acute myocardial infarction assessed by Doppler measurement of ascending aortic blood velocity and maximum acceleration

The Doppler-derived ejection variables systolic velocity integral, maximum acceleration and heart rate were recorded in 92 patients with acute myocardial infarction (AMI) and 73 age-matched normal subjects. Systolic velocity integral was validated as an index of stroke volume against a thermodilution technique in acutely ill patients. Patients with AMI were separated into clinically defined Forrester subsets and into survivors and nonsurvivors of the acute infarction period. Systolic velocity integral correlates significantly with stroke volume determined by thermodilution (r = 0.07) in patients with aortic root areas within the normal range. Patients had a 37% lower maximum acceleration (p less than or equal to 0.001), a 48% lower systolic velocity integral (p less than or equal to 0.001) and a 13% higher heart rate than the age-matched normal subjects (p less than or equal to 0.01). Systolic velocity integral and maximum acceleration both showed a systematic significant decrease through the Forrester subsets (p less than or equal to 0.01, p less than or equal to 0.001, respectively), and were also significantly different between the survivor and nonsurvivor groups (p less than or equal to 0.05, p less than or equal to 0.01, respectively.) Thus, noninvasive measurement of ascending aortic blood velocity and acceleration allows rapid assessment of left ventricular function and provides indexes closely related to the patients' clinical status and subsequent risk of mortality, indicating the potential of the Doppler technique in the prognosis and subsequent management of patients with myocardial infarction.

The iron-sulfur cluster composition of Escherichia coli nitrate reductase

Nitrate reductase from Escherichia coli has been investigated by low-temperature magnetic circular dichroism and electron paramagnetic resonance (EPR) spectroscopies, as well as by Fe-S core extrusion, to determine the Fe-S cluster composition. The results indicate approximately one 3Fe and three or four [4Fe-4S]2+,1+ centers/molecule of isolated enzyme. The magnetic circular dichroism spectra and magnetization characteristics show the oxidized and reduced 3Fe and [4Fe-4S] centers to be electronically analogous to those in bacterial ferredoxins. The form and spin quantitation of the EPR spectra from [4Fe-4S]1+ centers in the reduced enzyme were found to vary with the conditions of reduction. For the fully reduced enzyme, the EPR spectrum accounted for between 2.9 and 3.5 spins/molecule, and comparison with partially reduced spectra indicates weak intercluster magnetic interactions between reduced paramagnetic centers. In common with other Fe-S proteins, the 3Fe center was not extruded intact under standard conditions. The results suggest that nitrate reductase is the first example of a metalloenzyme where enzymatic activity is associated with a form that contains an oxidized 3Fe center. However, experiments to determine whether or not the 3Fe center is present in vivo were inconclusive.

The DNA-based human karyotype

Image cytometry and computer analysis are used to determine the relative DNA content and the DNA-based centromeric index of the 24 chromosomes of the human karyotype. A two-step procedure is used. Chromosomes of cells in metaphase first are stained with quinacrine and identified visually by their fluorescent Q-band patterns. They then are stained for DNA using gallocyanin-chrome alum. The chromosome images are scanned and recorded as digital values of optical density by an CYDAC image cytometric microscope system, CYDAC. The digital images are processed by computer to measure for each chromosome the relative DNA stain contents of the whole chromosome and of the p and q arms and the DNA-based centromeric index. About ten cells are analyzed for each of the donors, who are phenotypically normal men and women. The chromosome measurements are pooled by chromosome type for each donor and are compared among donors. The means of the chromosome measurements give the DNA-based human karyotype. Analysis of the DNA-based data shows that some chromosomes or portions of chromosomes vary significantly among donors. These variants do not correlate with detectable morphologic polymorphisms, such as Q- or C-band variants; thus they represent new and otherwise undetectable chromosome polymorphisms whose genetic basis and clinical significance are yet to be determined.

Quantitative methods of measuring the sensitivity of the mouse sperm morphology assay

In this study murine sperm were subjected to graded doses of X irradiation (0 to 120 rad) to determine whether quantitative measurements made on enlarged photographs of the sperm heads are related to radiation dose. We found that the Mahalanobis distance statistic, when used to measure distance in a multivariate space from a control group of measurements, could be used to classify sperm as normal or abnormal. The percent classified as abnormal by this method was found to be linearly related to dose. The results suggest that sensitivity of the murine sperm assay can be improved by selecting an optimal set of measurements. This improvement can reduce the doubling dose from approximately 70 rad to 10 to 15 rad while keeping the percentage of abnormal sperm in control mice at 3%, equal to the current visual method.

Correlation of primary breast cancer histopathology and estrogen receptor content

We studied the association of estrogen receptor (ER) with several histologic variables that correlate with breast tumor differentiation and with patient prognosis. Contingency table analysis revealed highly statistically significant correlations between ER content and histologic and nuclear grades, tumor necrosis, and the degree of elastosis and lymphoid cell infiltration. ER positive tumors were more likely than ER negative tumors to demonstrate histological evidence of tumor differentiation. All tumors with histologic grade 1 or nuclear grade 1 (best differentiated) were ER positive or borderline positive. Eighty-nine percent of ER negative tumors were histologic grade 3 and 78.4% were nuclear grade 3 (poor differentiation). ER positive tumors were also correlated with absent tumor necrosis, higher elastic content, and absent lymphoid cell infiltration, all features of good differentiation. Medullary carcinomas were frequently (73%) ER negative, but no relationship between ER and other morphologic types of breast cancer or 9 other morphologic variables was found. ER appears to be a biochemical marker for the degree of differentiation of human breast cancer providing a rationale for the observed differences in biological behavior between receptor positive and negative tumors.