Therapy with a severe acute respiratory syndrome-associated coronavirus-neutralizing human monoclonal antibody reduces disease severity and viral burden in golden Syrian hamsters

BackgroundImmunotherapy with monoclonal antibodies (MAbs) offers safe interventions for the prevention of infection in patients after organ transplantation and for the treatment of cancers and autoimmune diseases. MAb 201 is a severe acute respiratory syndrome–associated coronavirus (SARS-CoV)–specific MAb that prevents establishment of viral replication in vitro and prevents viral replication in vivo when administered prophylactically. The efficacy of MAb 201 in the treatment of SARS was evaluated in golden Syrian hamsters, an animal model that supports SARS-CoV replication to high levels and displays severe pathological changes associated with infection, including pneumonitis and pulmonary consolidation

MethodsGolden Syrian hamsters that were intranasally inoculated with SARS-CoV were treated with various doses of MAb 201 or an irrelevant MAb 24 h after inoculation. Two to 7 days after infection, the hamsters were killed, and their lungs were collected for evaluation of viral titers and pathological findings

ResultsPostexposure treatment with MAb 201 can alleviate the viral burden and associated pathological findings in a golden Syrian hamster model of SARS-CoV infection. After a hamster is treated with MAb 201, its viral burden is reduced by 10^2.4–10^3.9 50% tissue-culture infectious doses per gram of tissue, and the severity of associated pathological findings, including interstitial pneumonitis and consolidation, is also remarkably reduced

ConclusionsThe demonstration of successful postexposure MAb 201 therapy in an animal model that demonstrates viral replication and associated pulmonary pathological findings suggests that MAb 201 may be useful in the arsenal of tools to combat SARS

Peripheral B cells latently infected with Epstein-Barr virus display molecular hallmarks of classical antigen-selected memory B cells

Epstein-Barr virus (EBV) establishes a lifelong persistent infection within peripheral blood B cells with the surface phenotype of memory cells. To date there is no proof that these cells have the genotype of true germinal-center-derived memory B cells. It is critical to understand the relative contribution of viral mimicry versus antigen signaling to the production of these cells because EBV encodes proteins that can affect the surface phenotype of infected cells and provide both T cell help and B cell receptor signals in the absence of cognate antigen. To address these questions we have developed a technique to identify single EBV-infected cells in the peripheral blood and examine their expressed Ig genes. The genes were all isotype-switched and somatically mutated. Furthermore, the mutations do not cause stop codons and display the pattern expected for antigen-selected memory cells based on their frequency, type, and location within the Ig gene. We conclude that latently infected peripheral blood B cells display the molecular hallmarks of classical antigen-selected memory B cells. Therefore, EBV does not disrupt the normal processing of latently infected cells into memory, and deviations from normal B cell biology are not tolerated in the infected cells. This article provides definitive evidence that EBV in the peripheral blood persists in true memory B cells.

Cross-reactive influenza virus-specific CD8+ T cells contribute to lymphoproliferation in Epstein-Barr virus-associated infectious mononucleosis

The marked proliferation of activated CD8+ T cells is pathognomonic of EBV-associated infectious mononucleosis (IM), common in young adults. Since the diversity and size of the memory CD8+ T cell population increase with age, we questioned whether IM was mediated by the reactivation of memory CD8+ T cells specific to previously encountered pathogens but cross-reactive with EBV. Of 8 HLA-A2+ IM patients, 5 had activated T cells specific to another common virus, as evidenced by a significantly higher number of peripheral blood influenza A virus M1(58-66)-specific T cells compared with healthy immune donors. Two patients with an augmented M1 response had tetramer-defined cross-reactive cells recognizing influenza M1 and EBV-BMLF1(280-288), which accounted for up to one-third of their BMLF1-specific population and likely contributed to a skewed M1-specific T cell receptor repertoire. These epitopes, with only 33% sequence similarity, mediated differential effects on the function of the cross-reactive T cells, which may contribute to alterations in disease outcome. EBV could potentially encode an extensive pool of T cell epitopes that activate other cross-reactive memory T cells. Our results support the concept that cross-reactive memory CD8+ T cells activated by EBV contribute to the characteristic lymphoproliferation of IM.

Pneumonitis and multi-organ system disease in common marmosets (Callithrix jacchus) infected with the severe acute respiratory syndrome-associated coronavirus

Severe acute respiratory syndrome (SARS) is a significant emerging infectious disease. Humans infected with the etiological agent, SARS-associated coronavirus (SARS-CoV), primarily present with pneumonitis but may also develop hepatic, gastrointestinal, and renal pathology. We inoculated common marmosets (Callithrix jacchus) with the objective of developing a small nonhuman primate model of SARS. Two groups of C. jacchus were inoculated intratracheally with cell culture supernatant containing SARS-CoV. In a time course pathogenesis study, animals were evaluated at 2, 4, and 7 days after infection for morphological changes and evidence of viral replication. All animals developed a multifocal mononuclear cell interstitial pneumonitis, accompanied by multinucleated syncytial cells, edema, and bronchiolitis in most animals. Viral antigen localized primarily to infected alveolar macrophages and type-1 pneumocytes by immunohistochemistry. Viral RNA was detected in all animals from pulmonary tissue extracts obtained at necropsy. Viral RNA was also detected in tracheobronchial lymph node and myocardium, together with inflammatory changes, in some animals. Hepatic inflammation was observed in most animals, predominantly as a multifocal lymphocytic hepatitis accompanied by necrosis of individual hepatocytes. These findings identify the common marmoset as a promising nonhuman primate to study SARS-CoV pathogenesis.

The impact of race/ethnicity on mother-to-child HIV transmission in the United States in Pediatric AIDS Clinical Trials Group Protocol 316

The present analysis was designed to determine whether race/ethnicity was independently associated with mother-to-child HIV-1 transmission risk in subjects enrolled in a trial of 2-dose intra-partum nevirapine in combination with standard antiretroviral therapy and to determine what factors, including race/ethnicity, predicted maternal viral suppression at the time of delivery. Women enrolled in Pediatric AIDS Clinical Trials Group (PACTG) 316 from sites in the United States and Puerto Rico were included. Distribution of selected maternal disease and treatment characteristics was assessed by race/ethnicity category. Logistic regression models were fit to evaluate possible association of factors with HIV transmission and with viral load at delivery. Variables associated with the outcome at P < 0.05 level were retained in the final models. Of 1052 women randomized at PACTG sites, 891 were included in the present analysis: 572 (64%) were black; 206 (23%) were Hispanic; and 113 (13%) were white. All women who had infected infants were black or Hispanic (11/572 and 3/206, respectively), whereas none of the women identified as white had an infected infant (0/113). This difference was not statistically significant (P = 0.54). White women had higher entry CD4 cell counts and lower HIV-1 RNA at delivery than women of other races/ethnicities. Black and Hispanic women were more likely than white women to start therapy during their current pregnancy but did not initiate prenatal care later. In bivariate models that included antiretroviral type and variables that had values of P < or = 0.25 in univariate analysis, time of antiretroviral initiation, time of prenatal care initiation, and race/ethnicity each retained significance in predicting viral suppression at delivery. Race/ethnicity remained predictive of viral suppression at delivery in a multivariate model incorporating all of these variables (P = 0.01). Higher HIV-1 RNA and lower CD4 cell counts in women identified as black or Hispanic have significant implications for the health of these women and their newborns. Race/ethnicity is significant in predicting viral suppression at the time of delivery.

Nuclear localization of HIV type 1 Vif isolated from a long-term asymptomatic individual and potential role in virus attenuation

Recent reports have determined that HIV-1 Vif counteracts an innate antiviral cellular factor, Apobec3G. However, the function of Vif during HIV-1 pathogenesis remains poorly understood. To gain a better understanding of Vif function, the viral isolate from an HIV-1-infected long-term nonprogressor (LTNP) that displayed a Vif-mutant replication phenotype was studied. This LTNP has been infected since before 1983 and has no HIV-related disease in the absence of antiretroviral therapy. From separate samples, obtained on more than one study visit, virus grew in cocultures of LTNP cells with Vif-complementing T cell lines, but not the parental T cell lines. An unusual amino acid motif (KKRK) was found in the Vif sequence at positions 90 to 93. Since this motif commonly functions as a nuclear localization sequence, experiments were performed to determine the ability of this KKRK motif to mediate nuclear localization of Vif. Wild-type Vif displayed a predominantly cytoplasmic distribution. In contrast, the KKRK Vif showed a predominantly nuclear localization. The effect of the KKRK mutation on virus production and infectivity was also studied. The KKRK motif that mislocalizes Vif to the nucleus also reduces viral replication and infectivity in nonpermissive cells. Our data highlight the importance of Vif in HIV-1 pathogenesis and also provide a unique tool to investigate the interaction of Vif and Apobec3G.

Development and characterization of a severe acute respiratory syndrome-associated coronavirus-neutralizing human monoclonal antibody that provides effective immunoprophylaxis in mice

Background. Severe acute respiratory syndrome (SARS) remains a significant public health concern after the epidemic in 2003. Human monoclonal antibodies (MAbs) that neutralize SARS-associated coronavirus (SARSCoV) could provide protection for exposed individuals.

Methods. Transgenic mice with human immunoglobulin genes were immunized with the recombinant major surface (S) glycoprotein ectodomain of SARS-CoV. Epitopes of 2 neutralizing MAbs derived from these mice were mapped and evaluated in a murine model of SARS-CoV infection.

Results. Both MAbs bound to S glycoprotein expressed on transfected cells but differed in their ability to block binding of S glycoprotein to Vero E6 cells. Immunoprecipitation analysis revealed 2 antibody-binding epitopes: one MAb (201) bound within the receptor-binding domain at aa 490–510, and the other MAb (68) bound externally to the domain at aa 130–150. Mice that received 40 mg/kg of either MAb prior to challenge with SARS-CoV were completely protected from virus replication in the lungs, and doses as low as 1.6 mg/kg offered significant protection.

Conclusions. Two neutralizing epitopes were defined for MAbs to SARS-CoV S glycoprotein. Antibodies to both epitopes protected mice against SARS-CoV challenge. Clinical trials are planned to test MAb 201, a fully human MAb specific for the epitope within the receptor-binding region.

Efficient replication of severe acute respiratory syndrome coronavirus in mouse cells is limited by murine angiotensin-converting enzyme 2

Replication of viruses in species other than their natural hosts is frequently limited by entry and postentry barriers. The coronavirus that causes severe acute respiratory syndrome (SARS-CoV) utilizes the receptor angiotensin-converting enzyme 2 (ACE2) to infect cells. Here we compare human, mouse, and rat ACE2 molecules for their ability to serve as receptors for SARS-CoV. We found that, compared to human ACE2, murine ACE2 less efficiently bound the S1 domain of SARS-CoV and supported less-efficient S protein-mediated infection. Rat ACE2 was even less efficient, at near background levels for both activities. Murine 3T3 cells expressing human ACE2 supported SARS-CoV replication, whereas replication was less than 10% as efficient in the same cells expressing murine ACE2. These data imply that a mouse transgenically expressing human ACE2 may be a useful animal model of SARS.

CO2 emission benefit of diesel (versus gasoline) powered vehicles

Concerns regarding global warming have increased the pressure on automobile manufacturers to decrease emissions of CO2 from vehicles. Diesel vehicles have higher fuel economy and lower CO2 emissions than their gasoline counterparts. Increased penetration of diesel powered vehicles into the market is a possible transition strategy toward a more sustainable transportation system. To facilitate discussions regarding the relative merits of diesel vehicles it is important to have a clear understanding of their CO2 emission benefits. Based on European diesel and gasoline certification data, this report quantifies such CO2 reduction opportunities for cars and light duty trucks in today's vehicles and those in the year 2015. Overall, on a well-to-wheels per vehicle per mile basis, the CO2 reduction opportunity for today's vehicles is approximately 24-33%. We anticipate that the gap between diesel and gasoline well-to-wheel vehicle CO2 emissions will decrease to approximately 14-27% by the year 2015.

A trial of three antiretroviral regimens in HIV-1-infected children

BACKGROUND

Depletion of CD4 T-cell counts or progression of human immunodeficiency virus (HIV) disease occurs rapidly in children, but few data address the efficacy of aggressive therapy for HIV-infected children.

METHODS

We evaluated the safety, tolerability, and activity of three regimens of antiretroviral therapy in a multicenter, open-label, phase 1-2 trial. Children infected with HIV type 1 (HIV-1) were stratified at entry according to age--three months or younger (early therapy) or older than three months (delayed therapy)--and assigned sequentially to one of three regimens. Children continued to receive treatment for up to 200 weeks if the plasma HIV-1 RNA level was less than 1000 copies per milliliter by 16 weeks.

RESULTS

Plasma HIV-1 RNA levels fell from a median of 5.3 log copies per milliliter (range, 3.3 to 6.4 log copies per milliliter) at baseline to less than 1000 copies per milliliter at 16 weeks in 32 of 52 infants (62 percent). Plasma HIV-1 RNA levels were below 400 copies per milliliter at 48 weeks in 26 infants (50 percent) and at 200 weeks in 23 infants (44 percent). An intention-to-treat analysis revealed that significantly more children who received stavudine, lamivudine, nevirapine, and nelfinavir had plasma HIV-1 RNA levels of less than 400 copies per milliliter at 48 weeks (83 percent) and 200 weeks (72 percent) than children who received reverse-transcriptase inhibitors alone (P=0.001 and P=0.01, respectively). Fewer infants in the delayed-therapy group than in the early-therapy group (30 percent vs. 60 percent) had plasma HIV-1 RNA levels of less than 400 copies per milliliter at 200 weeks (P=0.03). Treatment-associated adverse effects were infrequent.

CONCLUSIONS

In this phase 1-2 trial involving HIV-1-infected children, an age of three months or younger at the initiation of therapy and treatment with stavudine, lamivudine, nevirapine, and nelfinavir were associated with improved long-term viral suppression. Larger, randomized trials are required to define the optimal time to initiate therapy and the optimal regimen for these infants.

Acute infection with Epstein-Barr virus targets and overwhelms the peripheral memory B-cell compartment with resting, latently infected cells

In this paper we demonstrate that during acute infection with Epstein-Barr virus (EBV), the peripheral blood fills up with latently infected, resting memory B cells to the point where up to 50% of all the memory cells may carry EBV. Despite this massive invasion of the memory compartment, the virus remains tightly restricted to memory cells, such that, in one donor, fewer than 1 in 10(4) infected cells were found in the naive compartment. We conclude that, even during acute infection, EBV persistence is tightly regulated. This result confirms the prediction that during the early phase of infection, before cellular immunity is effective, there is nothing to prevent amplification of the viral cycle of infection, differentiation, and reactivation, causing the peripheral memory compartment to fill up with latently infected cells. Subsequently, there is a rapid decline in infected cells for the first few weeks that approximates the decay in the cytotoxic-T-cell responses to viral replicative antigens. This phase is followed by a slower decline that, even by 1 year, had not reached a steady state. Therefore, EBV may approach but never reach a stable equilibrium.

Alterations in HIV-1 LTR promoter activity during AIDS progression

HIV-1 variants evolving in AIDS patients frequently show increased replicative capacity compared to those present during early asymptomatic infection. It is known that late stage HIV-1 variants often show an expanded coreceptor tropism and altered Nef function. In the present study we investigated whether enhanced HIV-1 LTR promoter activity might also evolve during disease progression. Our results demonstrate increased LTR promoter activity after AIDS progression in 3 of 12 HIV-1-infected individuals studied. Further analysis revealed that multiple alterations in the U3 core-enhancer and in the transactivation-response (TAR) region seem to be responsible for the enhanced functional activity. Our findings show that in a subset of HIV-1-infected individuals enhanced LTR transcription contributes to the increased replicative potential of late stage virus isolates and might accelerate disease progression.

Vertical transmission of Mycobacterium tuberculosis in KwaZulu Natal: impact of HIV-1 co-infection

BACKGROUND

Increases in perinatal TB have paralleled the exacerbation of the TB epidemic in KwaZulu Natal. The exact risks for vertical transfer of Mycobacterium tuberculosis (VTRTB) to the baby are unknown, as is the impact of HIV-1 co-infection, which frequently accompanies maternal TB disease in the region.

DESIGN

Prospective case series study of 82 HIV-1-infected and 25 non-infected pregnant mothers, King Edward VIII Hospital, KwaZulu Natal, South Africa.

RESULTS

Perinatal mortality in HIV-1/TB diseased mothers was 85/1000 and associated with maternal anaemia (P = 0.02); 46% of newborns were premature, 66% low birth weight and 49% intrauterine growth restricted. These were significantly higher than overall hospital rates (P < 0.01, OR 4.8, 95%CI 3.2-7.0). Sites of detection of maternal TB, distribution of bacteriologically-proven TB, obstetric comorbidity and perinatal morbidity were similar in HIV-1-infected and non-infected mothers. VTRTB was detected in 16 newborns (16%), occurring similarly in bacteriologically-proven and suspected maternal TB disease, with no difference between HIV-1-infected and non-infected mothers. Eleven newborns with VTRTB were HIV-1 exposed; 64% acquired HIV-1 and died from rapidly progressive disease by 10 months of age. HIV-1-infected mothers and their exposed newborns had significantly lower CD4 counts. No association between perinatal maternal viral load, CD4 count or VTRTB was detected.

CONCLUSION

Mothers with TB disease in pregnancy are at risk for significant perinatal morbidity, mortality and VTRTB.

Demonstration of the Burkitt's lymphoma Epstein-Barr virus phenotype in dividing latently infected memory cells in vivo

Epstein-Barr virus (EBV) is a herpesvirus that establishes a lifelong, persistent infection. It was first discovered in the tumor Burkitt's lymphoma (BL). Despite intensive study, the role of EBV in BL remains enigmatic. One striking feature of the tumor is the unique pattern of viral latent protein expression, which is restricted to EBV-encoded nuclear antigen (EBNA) 1. EBNA1 is required to maintain the viral genome but is not recognized by cytotoxic T cells. Consequently, it was proposed that this expression pattern was used by latently infected B cells in vivo. This would be the site of long-term, persistent infection by the virus and, by implication, the progenitor of BL. We now know that EBV persists in memory B cells in the peripheral blood and that BL is a tumor of memory cells. However, a normal B cell expressing EBNA1 alone has been elusive. Here we show that most infected cells in the blood express no detectable latent mRNA or proteins. The exception is that when infected cells divide they express EBNA1 only. This is the first detection of the BL viral phenotype in a normal, infected B cell in vivo. It suggests that BL may be a tumor of a latently infected memory B cell that is stuck proliferating because it is a tumor and, therefore, constitutively expressing only EBNA1.

Angiotensin-converting enzyme 2 is a functional receptor for the SARS coronavirus

Spike (S) proteins of coronaviruses, including the coronavirus that causes severe acute respiratory syndrome (SARS), associate with cellular receptors to mediate infection of their target cells. Here we identify a metallopeptidase, angiotensin-converting enzyme 2 (ACE2), isolated from SARS coronavirus (SARS-CoV)-permissive Vero E6 cells, that efficiently binds the S1 domain of the SARS-CoV S protein. We found that a soluble form of ACE2, but not of the related enzyme ACE1, blocked association of the S1 domain with Vero E6 cells. 293T cells transfected with ACE2, but not those transfected with human immunodeficiency virus-1 receptors, formed multinucleated syncytia with cells expressing S protein. Furthermore, SARS-CoV replicated efficiently on ACE2-transfected but not mock-transfected 293T cells. Finally, anti-ACE2 but not anti-ACE1 antibody blocked viral replication on Vero E6 cells. Together our data indicate that ACE2 is a functional receptor for SARS-CoV.

Prevention of Mother-to-Child Transmission of HIV-What Next?

Mother-to-child transmission (MTCT) of the human immunodeficiency virus (HIV) is a global problem. HIV can be transmitted from mother-to-child at various stages of pregnancy including in utero, intrapartum and during breastfeeding. A number of interventions have, therefore, been aimed at effectively providing alternatives to breastfeeding and limiting the risk of newborn infection during delivery, by using caesarian section as the mode of delivery and administering antiretroviral (ARV) drugs prepartum and peripartum. However, these approaches are not always possible in developing countries and the use of ARV drugs, in particular nevirapine, zidovudine and zidovudine/lamivudine, have been investigated in both developing countries and developed countries. The studies have involved the administration of various ARV prophylaxis regimens to HIV-infected pregnant women perinatally, either as monotherapy or in various combinations. In some studies, infants have also received ARV prophylaxis. Although studies have enrolled different populations and utilized various ARV drugs and regimens, encouraging reductions in the MTCT rates have been reported. These interventions have raised concerns regarding the development of ARV-resistant HIV strains. Mutations that confer resistance to nevirapine have been detected in pregnant women who received this drug, but the emergence of these mutations was not associated with an increased risk of transmission of HIV-1 to their infants. Studies are ongoing to determine if the presence of these mutations has implications for the subsequent administration of nevirapine, either to prevent MTCT of HIV-1 or for the mother's own health. Effective interventions that can reduce MTCT of HIV are now available worldwide. However, a number of issues remain to be resolved, particularly methods to reduce the transmission of the virus during breastfeeding and to deliver effective treatment for the mothers' own HIV infection.

Predose infant nevirapine concentration with the two-dose intrapartum neonatal nevirapine regimen: association with timing of maternal intrapartum nevirapine dose

OBJECTIVE

To evaluate cord blood and predose nevirapine concentrations in infants exposed to the two-dose intrapartum neonatal nevirapine regimen.

METHODS

The authors obtained plasma samples for nevirapine assay from cord blood and just prior to the 48-hours to 72-hours after birth neonatal nevirapine dose from a subset of infants participating in PACTG 316, a randomized, placebo-controlled trial of the two-dose intrapartum neonatal nevirapine regimen added to standard antiretroviral therapy.

RESULTS

Nevirapine concentrations were measured in 109 cord blood samples and 149 predose samples. Cord blood nevirapine concentrations were below the target concentration of 100 ng/mL (10-times the in vitro IC(50) of nevirapine against wild-type HIV) in eight (7%) of 109 infants (95% confidence interval [CI], 3%-14%); the concentrations in six of these infants were below the assay limit of quantitation. Predose infant nevirapine concentrations were below 100 ng/mL in 23 (15%) of 149 infants (95% CI, 10%-22%); the concentrations in 13 of these infants were below the assay limit of quantitation. Lower predose nevirapine concentrations were associated with lower cord blood concentrations and a shorter interval between maternal dosing and delivery. All but one of the infants with predose nevirapine concentrations below the assay limit of quantitation were born less than 2 hours after maternal dosing.

CONCLUSION

Infants born less than 2 hours after maternal nevirapine dosing during labor should receive a dose of nevirapine immediately after birth in addition to the standard infant dose at 48 to 72 hours.

Multicenter evaluation of use of dried blood and plasma spot specimens in quantitative assays for human immunodeficiency virus RNA: measurement, precision, and RNA stability

Eleven laboratories evaluated the use of dried blood and plasma spots for quantitation of human immunodeficiency virus (HIV) RNA by two commercially available RNA assays, the Roche Amplicor HIV-1 Monitor and the bioMerieux NucliSens HIV-1 QT assays. The recovery of HIV RNA was linear over a dynamic range extending from 4,000 to 500,000 HIV type 1 RNA copies/ml. The Monitor assay appeared to have a broader dynamic range and seemed more sensitive at lower concentrations. However, the NucliSens assay gave more consistent results and could be performed without modification of the kit. HIV RNA was stable in dried whole blood or plasma stored at room temperature or at -70 degrees C for up to 1 year. Dried blood and dried plasma spots can be used as an easy and inexpensive means for the collection and storage of specimens under field conditions for the diagnosis of HIV infection and the monitoring of antiretroviral therapy.

Accuracy of the TRUGENE HIV-1 genotyping kit

Drug resistance and poor virological responses are associated with well-characterized mutations in the viral reading frames that encode the proteins that are targeted by currently available antiretroviral drugs. An integrated system was developed that includes target gene amplification, DNA sequencing chemistry (TRUGENE HIV-1 Genotyping Kit), and hardware and interpretative software (the OpenGene DNA Sequencing System) for detection of mutations in the human immunodeficiency virus type 1 (HIV-1) protease and reverse transcriptase sequences. The integrated system incorporates reverse transcription-PCR from extracted HIV-1 RNA, a coupled amplification and sequencing step (CLIP), polyacrylamide gel electrophoresis, semiautomated analysis of data, and generation of an interpretative report. To assess the accuracy and robustness of the assay system, 270 coded plasma specimens derived from nine patients were sent to six laboratories for blinded analysis. All specimens contained HIV-1 subtype B viruses. Results of 270 independent assays were compared to "gold standard" consensus sequences of the virus populations determined by sequence analysis of 16 to 20 clones of viral DNA amplicons derived from two independent PCRs using primers not used in the kit. The accuracy of the integrated system for nucleotide base identification was 98.7%, and the accuracy for codon identification at 54 sites associated with drug resistance was 97.6%. In a separate analysis of plasma spiked with infectious molecular clones, the assay reproducibly detected all 72 different drug resistance mutations that were evaluated. There were no significant differences in accuracy between laboratories, between technologists, between kit lots, or between days. This integrated assay system for the detection of HIV-1 drug resistance mutations has a high degree of accuracy and reproducibility in several laboratories.

Differential kinetics and specificity of EBV-specific CD4+ and CD8+ T cells during primary infection

The generation and maintenance of virus-specific CD4(+) T cells in humans are not well understood. We used short in vitro stimulation assays followed by intracellular cytokine staining to characterize the timing, magnitude, and Ag specificity of CD4(+) T cells over the course of primary EBV infection. Lytic and latent protein-specific CD4(+) T cells were readily detected at presentation with acute infectious mononucleosis and declined rapidly thereafter. Responses to BZLF-1, BMLF-1, and Epstein-Barr nuclear Ag-3A were more commonly detected than responses to Epstein-Barr nuclear Ag-1. Concurrent analyses of BZLF-1-specific CD4(+) and CD8(+) T cells revealed differences in the expansion, specificity, and stability of CD4(+) and CD8(+) T cell-mediated responses over time. Peripheral blood EBV load directly correlated with the frequency of EBV-specific CD4(+) T cell responses at presentation and over time, suggesting that EBV-specific CD4(+) T cell responses are Ag-driven.

A multicenter randomized controlled trial of nevirapine versus a combination of zidovudine and lamivudine to reduce intrapartum and early postpartum mother-to-child transmission of human immunodeficiency virus type 1

To determine the efficacy and safety of 2 inexpensive and easily deliverable antiretroviral (ARV) regimens for the prevention of mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) type 1 during labor and delivery, HIV-infected pregnant women were screened at 11 maternity health institutions in South Africa and were enrolled in an open-label short course ARV regimen of either nevirapine (Nvp) or multiple-dose zidovudine and lamivudine (Zdv/3TC). The overall estimated HIV-1 infection rates in 1307 infants by 8 weeks were 12.3% (95% confidence interval [CI], 9.7-15.0) for Nvp and 9.3% (95% CI, 7.0-11.6) for Zdv/3TC (P=.11). Excluding infections detected within 72 h (intrauterine), new HIV-1 infections were detected in 5.7% (95% CI, 3.7-7.8) and 3.6% (95% CI, 2.0-5.3) of infants in the Nvp and Zdv/3TC groups, respectively, in the 8 weeks after birth. There were no drug-related maternal or pediatric serious adverse events. Common complications were obstetrical for mothers (Nvp group, 24.3%; Zdv/3TC group, 26.3%) and respiratory for infants (Nvp group, 16.1%; Zdv/3TC group, 17.0%). This study further confirms the efficacy and safety of short-course ARV regimens in reducing MTCT rates in developing countries.

Concentrations of protease inhibitors in cord blood after in utero exposure

OBJECTIVE

To determine the concentrations of protease inhibitors in cord blood after prenatal protease inhibitor use by pregnant women.

DESIGN

Retrospective analysis of samples collected in a clinical trial.

METHODS

Protease inhibitor concentrations were measured in cord blood samples collected from women enrolling in the PACTG 316 study who were receiving prenatal protease inhibitor antiretroviral therapy.

RESULTS

In cord blood samples from 68 women treated with protease inhibitors during pregnancy, the concentration of these drugs was below the assay lower limit of detection in most samples, including all samples from women receiving indinavir (n = 21) and saquinavir (n = 8), 5 of 6 samples (83%) from women receiving ritonavir and 24 of 38 samples (63%) from women receiving nelfinavir.

CONCLUSIONS

Low protease inhibitor concentrations in the fetus decrease the likelihood of teratogenic and toxic effects of these drugs but could fail to provide protection from transplacental or intrapartum transmission of HIV-1.

Development of resistance mutations in women receiving standard antiretroviral therapy who received intrapartum nevirapine to prevent perinatal human immunodeficiency virus type 1 transmission: a substudy of pediatric AIDS clinical trials group protocol 316

Pediatric AIDS Clinical Trials Group protocol 316 was an international, multicenter, placebo-controlled trial comparing single-dose oral nevirapine (200 mg to mother and 2 mg/kg to infant) with placebo in human immunodeficiency virus (HIV)-infected pregnant women receiving standard antiretroviral therapy. This substudy evaluated the emergence of nevirapine-resistance mutations at 6 weeks postpartum in a subgroup of participants. Maternal risk factors for the emergence of nevirapine-resistance mutations were evaluated. Mutations associated with nevirapine resistance were detectable at delivery, prior to receipt of study drug, in 5 (2.3%) of 217 women. Fourteen (15%; 95% confidence interval, 8%-23%) of 95 women who received intrapartum nevirapine developed a nevirapine-resistance mutation 6 weeks postpartum. The most common mutation was K103N, which was present in 10 women. The risk for development of a new nevirapine-resistance mutation did not correlate with CD4 cell count or HIV-1 RNA load at delivery or with type of antepartum antiretroviral therapy. The risk of nevirapine resistance should be considered when determining the risks or benefits of intrapartum nevirapine in women receiving antepartum antiretroviral therapy.