Emerging resistance mutations in PI-naive patients failing an atazanavir-based regimen (ANRS multicentre observational study).

Background: Atazanavir is a PI widely used as a third agent in combination ART. We aimed to determine the prevalence and the patterns of resistance in PI-naive patients failing on an atazanavir-based regimen. Methods: We analysed patients failing on an atazanavir-containing regimen used as a first line of PI therapy. We compared the sequences of reverse transcriptase and protease before the introduction of atazanavir and at failure [two consecutive viral loads (VLs) >50 copies/mL]. Resistance was defined according to the 2014 Agence Nationale de Recherche sur le SIDA et les Hépatites Virales (ANRS) algorithm. Results: Among the 113 patients, atazanavir was used in the first regimen in 71 (62.8%) patients and in the first line of a PI-based regimen in 42 (37.2%). Atazanavir was boosted with ritonavir in 95 (84.1%) patients and combined with tenofovir/emtricitabine or lamivudine (n = 81) and abacavir/lamivudine or emtricitabine (n = 22). At failure, median VL was 3.05 log10 copies/mL and the median CD4+ T cell count was 436 cells/mm3. The median time on atazanavir was 21.2 months. At failure, viruses were considered resistant to atazanavir in four patients (3.5%) with the selection of the following major atazanavir-associated mutations: I50L (n = 1), I84V (n = 2) and N88S (n = 1). Other emergent PI mutations were L10V, G16E, K20I/R, L33F, M36I/L, M46I/L, G48V, F53L, I54L, D60E, I62V, A71T/V, V82I/T, L90M and I93L/M. Emergent NRTI substitutions were detected in 21 patients: M41L (n = 2), D67N (n = 3), K70R (n = 1), L74I/V (n = 3), M184V/I (n = 16), L210W (n = 1), T215Y/F (n = 3) and K219Q/E (n = 2). Conclusions: Resistance to atazanavir is rare in patients failing the first line of an atazanavir-based regimen according to the ANRS. Emergent NRTI resistance-associated mutations were reported in 18% of patients.

Prevalence of HIV-1 drug resistance in treated patients with viral load >50 copies/mL: a 2014 French nationwide study.

Background: Surveillance of HIV-1 resistance in treated patients with a detectable viral load (VL) is important to monitor, in order to assess the risk of spread of resistant viruses and to determine the proportion of patients who need new antiretroviral drugs with minimal cross-resistance. Methods: The HIV-1 protease and reverse transcriptase (RT) and integrase genes were sequenced in plasma samples from 782 consecutive patients on failing antiretroviral regimens, seen in 37 specialized centres in 2014. The genotyping results were interpreted using the ANRS v24 algorithm. Prevalence rates were compared with those obtained during a similar survey conducted in 2009. Results: The protease and RT sequences were obtained in 566 patients, and the integrase sequence in 382 patients. Sequencing was successful in 60%, 78%, 78% and 87% of patients with VLs of 51-200, 201-500, 501-1000 and >1000 copies/mL, respectively. Resistance to at least one antiretroviral drug was detected in 56.3% of samples. Respectively, 3.9%, 8.7%, 1.5% and 3.4% of patients harboured viruses that were resistant to any NRTI, NNRTI, PI and integrase inhibitor (INI). Resistance rates were lower in 2014 than in 2009. Resistance was detected in 48.5% of samples from patients with a VL between 51 and 200 copies/mL. Conclusion: In France in 2014, 90.0% of patients in AIDS care centres were receiving antiretroviral drugs and 12.0% of them had VLs >50 copies/mL. Therefore, this study suggests that 6.7% of treated patients in France might transmit resistant strains. Resistance testing may be warranted in all treated patients with VL > 50 copies/mL.

HIV-1 subtype influences susceptibility and response to monotherapy with the protease inhibitor lopinavir/ritonavir.

OBJECTIVE: PI susceptibility results from a complex interplay between protease and Gag proteins, with Gag showing wide variation across HIV-1 subtypes. We explored the impact of pre-treatment susceptibility on the outcome of lopinavir/ritonavir monotherapy. METHODS: Treatment-naive individuals who experienced lopinavir/ritonavir monotherapy failure from the MONARK study were matched (by subtype, viral load and baseline CD4 count) with those who achieved virological response ('successes'). Successes were defined by viral load <400 copies/mL after week 24 and <50 copies/mL from week 48 to week 96. Full-length Gag-protease was amplified from patient samples for in vitro phenotypic susceptibility testing, with susceptibility expressed as fold change (FC) relative to a subtype B reference strain. RESULTS: Baseline lopinavir susceptibility was lower in viral failures compared with viral successes, but the differences were not statistically significant (median lopinavir susceptibility: 4.4 versus 8.5, respectively, P = 0.17). Among CRF02_AG/G patients, there was a significant difference in lopinavir susceptibility between the two groups (7.1 versus 10.4, P = 0.047), while in subtype B the difference was not significant (2.7 versus 3.4, P = 0.13). Subtype CRF02_AG/G viruses had a median lopinavir FC of 8.7 compared with 3.1 for subtype B (P = 0.001). CONCLUSIONS: We report an association between reduced PI susceptibility (using full-length Gag-protease sequences) at baseline and subsequent virological failure on lopinavir/ritonavir monotherapy in antiretroviral-naive patients harbouring subtype CRF02_AG/G viruses. We speculate that this may be important in the context of suboptimal adherence in determining viral failure.

Safety of hematopoietic stem cell transplantation from hepatitis B core antibodies-positive donors with low/undetectable viremia in HBV-naïve children.

Scarce data exist on allogeneic hematopoietic stem cell transplantation (HSCT) outcomes in hepatitis B virus (HBV)-naïve recipients from HBV-experienced donors. Long-term follow-up is herein reported for 17 allogeneic HSCT performed in 13 HBV-naïve children from HBc-antibodies-positive donors between 2006 and 2012. Four donors were HBs-antigen-positive, with detectable but low viremia in 2 cases (<2 log10IU/ml). HBV-DNA was undetectable in all transplanted cell products. Recipients' HBV prophylaxis consisted of pre-transplant vaccination, polyvalent immune globulins, specific anti-HBV immune globulins, and/or oral lamivudine in 3, 12, 8, and 8 children, respectively. No case of HBV transmission occurred based on negative close monitoring of recipients' HBV serology and plasma HBV-DNA during a median follow-up of 22 months. In case of undetectable viremia in the donor, prophylaxis with vaccination and/or immune globulins in the recipient seems to be sufficient and lamivudine prophylaxis might be unnecessary to prevent viral transmission. In case of undetectable viremia in the donor, a systematic screening of HBV DNA in the stem cell product might be unnecessary to confirm the low risk of viral transmission. Prior exposure to HBV in the donor should not be considered a contraindication to HSCT.

Evaluation of an upgraded version of the Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 test for HIV-1 load quantification.

We evaluated the performance of the prototype Cobas AmpliPrep/Cobas TaqMan HIV-1 test, version 2.0, using prospective and archived clinical samples initially underquantitated by the Cobas AmpliPrep/Cobas TaqMan HIV-1 test. The performance of the new test was significantly improved, and the majority of the underquantitation observed with the first-version test was eliminated.

Long-term (96-week) follow-up of antiretroviral-naïve HIV-infected patients treated with first-line lopinavir/ritonavir monotherapy in the MONARK trial.

BACKGROUND: The toxicities, cost and complexity of triple combinations warrant the search for other treatment options, such as boosted protease inhibitor (PI) monotherapy. MONotherapy AntiRetroviral Kaletra (MONARK) is the first randomized trial comparing lopinavir/ritonavir monotherapy to triple combination therapy with zidovudine/lamivudine and lopinavir/ritonavir in antiretroviral-naïve patients. METHODS: A total of 136 antiretroviral-naïve patients, with a CD4 cell count above 100 cells/microL and a plasma HIV RNA below 100,000 HIV-1 RNA copies/mL, were randomized and dosed with either lopinavir/ritonavir monotherapy (n = 83) or lopinavir/ritonavir + zidovudine/lamivudine (n = 53). We focus here on patients in the lopinavir/ritonavir monotherapy arm followed to week 96. The intent-to-treat (ITT) analysis initially involved all patients randomized to lopinavir/ritonavir monotherapy (n = 83), and then focused on patients who had an HIV RNA < 50 copies/mL at week 48 (n = 56). RESULTS: At week 96, 39 of 83 patients (47%) had HIV RNA < 50 copies/mL, five of 83 had HIV RNA between 50 and 400 copies/mL, and three of 83 had HIV RNA > 400 copies/mL. Focusing on the 56 patients with an HIV RNA < 50 copies/mL at week 48, 38 of 56 patients (68%) had a sustained HIV RNA < 50 copies/mL to week 96. To week 96, a total of 28 patients (34%) had discontinued the study treatment. In addition, the allocated treatment was changed for seven patients. PI-associated resistance mutations were evident in five of 83 patients in the monotherapy arm from baseline to week 96. CONCLUSION: By ITT analysis, 39 of the 83 patients initially randomized to lopinavir/ritonavir monotherapy had HIV RNA < 50 copies/mL at week 96. The occurrence in some patients of low-level viraemia (50-500 copies/mL) may increase the risk of drug resistance. First-line lopinavir/ritonavir monotherapy cannot be systematically recommended.

Phylogenetic investigation of HCV-4d epidemic in Paris MSM HIV population reveals a still active outbreak and a strong link to the Netherlands.

OBJECTIVES: The hepatitis C virus (HCV) epidemic is evolving quickly despite new treatments, and due to behaviour changes increasing at-risk situations. We investigated potential origins and evolution of the HCV-4d French emergence among human immunodeficiency virus (HIV)-infected men who have sex with men (MSM), in Paris in 2003. METHODS: We analysed all HCV sequences from the initial Paris outbreak with all newly available sequences publicly available, including sampling date and geographical location, resulting in 184, 68, 156, 107, 13 and 2 sequences from France, The Netherlands, other European countries, Africa, the Middle East or Turkey, Americas and Asia, respectively. Phylogenetic reconstruction was performed using maximum likelihood and Bayesian approaches. RESULTS: HCV-4d sequences from Europe were strongly separated from non-European sequences. Sequences from the initial Paris outbreak were all included into two well-separated and supported clusters with branch support at 100%, mean genetic distance <2.8 substitutions/100 nucleotides and >3.4 substitutions/100 nucleotides between their common ancestor and the previous node. The largest cluster interleaved French (n = 98) and Dutch (n = 28) sequences, suggesting several translocations between these countries. This cluster included 41 French sequences from Lyon sampled after 2014, highlighting its continuous spread within France since the initial outbreak. The smallest cluster included one Paris sequence with UK sequences (n = 9). DISCUSSION: A few previous works have shown HCV-4d transmissions occurring between a few countries. In our work, we suggest a new and large connection between France and The Netherlands MSM communities and highlight a well-separated pan-European transmission network. Large collaborative networks are needed to investigate ongoing transmissions across countries and help specific prevention measures.

Comparative performance of the Biocentric Generic Viral Load, Roche CAP/CTM v1.5, Roche CAP/CTM v2.0 and m2000 Abbott assays for quantifying HIV-1 B and non-B strains: Underestimation of some CRF02 strains.

BACKGROUND: HIV-1 viral load testing is now recommended by the World Health Organization for every patient receiving antiretroviral therapy (ART). OBJECTIVES: The objective of this study is to evaluate the performance of commercial assays for their ability to quantify HIV-1 strains currently circulating in France. STUDY DESIGN: The performances of the Generic HIV-RNA assay from Biocentric were compared to those of the Roche CAP/CTM v1.5, Roche CAP/CTM v2.0 and Abbott m2000 RealTime HIV-1 assays. A total of 1885 HIV-1 plasma samples were tested, including 684 samples from patients included in the ANRS-Primo Cohort. RESULTS: We found a good concordance of quantification between the Roche v2.0 and the Biocentric assays, both of which were superior to the Roche v1.5 assay. We show moderate agreement between techniques; however, CRF02_AG strains and undetermined viruses were underestimated when quantified with the Roche CAP/CTM v2.0. In contrast, a comparison of the Biocentric and Abbott assay results showed strong agreement between assays, indicating that both are well suited for quantification of CRF02_AG strains. Moreover, a 2% underestimation of the B subtypes was observed with the Biocentric assay. CONCLUSIONS: These results have implications for viral load monitoring in Western Africa, where CRF02_AG strains are highly prevalent. Closer epidemiological surveillance and evaluation of commercial assays are still necessary to better evaluate the impact of the genetic evolution of circulating viruses on HIV-RNA quantification in the regions most affected by the HIV-1 epidemic.

[HIV-1 drug resistance in French infected-children: from newborn to adolescent]. / La résistance du VIH-1 aux antirétroviraux chez les enfants infectés : du nouveau-né à l'adolescent.

Limit of antiretroviral treatment success is the emergence of drug-resistant virus. As reported in adult population, prevalence of resistance was high in treated HIV-infected children with detectable HIV viral load. Resistance increased with number of prior antiretroviral treatments, particularly with protease inhibitors. Adolescent boys seem at greater risk to harbor multi-classes resistant virus. In HIV-infected newborns, prevalence of resistance was 20%. Most of resistance mutations detected were in accord to perinatal antiretroviral exposition. Principal mechanism of resistance acquisition in newborns was transmission of resistant viruses from mother to child with early archive in cellular reservoir and long term persistence with or without treatment. Consequences of long term therapeutic strategies in children are major.

[HIV resistance to non-nucleoside reverse transcriptase inhibitors]. / Résistance du VIH aux inhibiteurs non nucléosidiques de la transcriptase inverse (INNTI).

Resistance to non-nucleoside reverse transcriptase inhibitor (NNRTI) has been found to develop rapidly after initiation of NNRTI therapy with high level of phenotypic resistance and large cross-resistance to all licensed NNRTI. NNRTI-selected mutations confer little damage to viral fitness and persist in absence of drug. In HIV-1 non-B subtype, resistance profile could differ and survey is needed. Single dose of nevirapine in the prevention of HIV mother-tochild transmission was associated with selection of resistance and loss of virologic response to NNRTI including-regimen. Furthermore, with continued therapy, viral evolution persists, creating species with greater numbers of mutations and higher level of phenotypic resistance that limits future treatment options.Absence of immunologic and virologic effect when NNRTI interruption was proposed in patients with resistant virus suggest that these compounds have lost all their in vivo antiviral activity. Taken together, strong consideration should be given to discontinuing NNRTI after virologic failure is confirmed.

First next-generation sequencing full-genome characterization of a hepatitis C virus genotype 7 divergent subtype.

We report the near-full-length genome sequence of a hepatitis C virus (HCV) isolate from a man originating from Democratic Republic of Congo, the genotype of which could not be determined by the routinely used sequencing technique. The near-complete genome sequence of this variant BAK1 was obtained by the association of two next-generation sequencing technologies. Evolutionary analysis indicates that this isolate, BAK1, could be the first reported strain belonging to a new HCV-7b subtype. This new subtype has been incorrectly identified as genotype 2 by the Versant HCV Genotype 2.0 assay (LiPA). The requirement of three independent isolates has been filled, and a new subtype can be assigned. More examples of HCV-7 are required to better understand its origin, its pathogenicity and its relationship with genotype 2.

[Male genital tract infection: the point of view of the virologist]. / Infection du tractus génital masculin: le point de vue du virologue.

Attention to viral infection of the male genital tract has been renewed over the last 15 years as a result of the prolific ongoing research on AIDS. Epidemiological studies of the virus in sperm and male genital tract contributes to the understanding of STD physiopathology and helps assessing their impact on male fertility. Recent advances in this field have allowed to offer Assisted reproductive techniques to couples with chronic viral infection, under strict and specific protocols. This paper presents an overview of these recent developments.

Immunogenicity of free histones and of histones complexed with RNA.

Histone antibodies have been obtained by immunizing rabbits with histones H1, H2A, H2B, H3, H4 and triacetylated H4, uncomplexed to RNA. The reactivity of these antibodies was investigated by ELISA using as antigen isolated histones and chromatin as well as thirty-five different synthetic peptides covering the entire sequence of the four core histones, two peptides of H1 and two acetylated peptides of H4. The binding of these antibodies to histones was also measured in immunoblotting and in microcomplement fixation (MCF) tests. In parallel experiments using the same assays the various antigens were tested with antisera raised against histones complexed with RNA. Antibodies induced in the absence of RNA did not react with histones in MCF tests nor with chromatin in ELISA but reacted with the histones in ELISA, although the antibody titers were somewhat lower than in the case of antisera to histone-RNA complexes. Antibodies to RNA-histone complexes reacted with histones in both ELISA and MCF tests. When they were tested with peptide-coated microtiter plates in a direct binding ELISA format, antibodies induced with uncomplexed histones recognized very few fragments which were mainly located in the N- and C-terminal ends of the histones.

Diversity of the V3 region of HIV in Paris, France.

OBJECTIVE: To carry out, within France, a large-scale molecular epidemiological investigation on the principal neutralizing determinant of HIV-1, located in the third variable region (V3) of the envelope protein. Such investigations are of the utmost importance in the identification and monitoring of the distribution and spread of different viral strains internationally. DESIGN: Using polymerase chain reaction (PCR), we examined the genetic variation of the V3 region sequences of 28 HIV-infected patients from Paris, France. RESULTS: Comparison of the Parisian V3 loop sequences with other published data indicates that the range of diversity in France is included within that of a large group that contains sequences from North America, the rest of Europe, Japan, India and Africa. Variability appears to be lower in the V3 loop than in its flanking regions. Five out of the six putative N-linked glycosylation sites show preferential alterations to charged amino acids. We report two motifs at the tip of the loop that have not been described previously. CONCLUSIONS: The structural homogeneity and the wide geographic representation of the major V3 group suggests that a common strategy could be applied to a large proportion of isolates in the development of a broad-spectrum HIV vaccine.

Highly active antiretroviral therapy started in infants under 3 months of age: 72-week follow-up for CD4 cell count, viral load and drug resistance outcome.

OBJECTIVE: To assess the feasibility and impact of highly active antiretroviral therapy (HAART) started in vertically HIV-1-infected infants less than 3 months of age. DESIGN: A multicentre, phase I/II, non-randomized, open-label study (PENTA 7). METHODS: Adverse events, plasma HIV-1 RNA, CD4 cell counts, CD4 cell percentage (CD4%) and clinical progression were recorded at baseline and prospectively to 72 weeks in order to assess the toxicity, tolerability and efficacy of a combination of stavudine, didanosine and nelfinavir. Selection of genotypic resistance was also investigated. RESULTS: Twenty infants, of whom only three had Centers for Disease Control and Prevention stage B, initiated HAART at median age 2.5 months (range, 0.9-4.7) with median HIV-1 RNA concentration 5.5 log10 copies/ml (range, 3.2-6.8) and CD4% 33% (range, 11-66). Median follow-up was 96 weeks (range, 60-144). At week 72, 11 infants were still taking the original treatment. Few adverse events were reported related to treatment, all minor and causing treatment interruption in only three infants. No AIDS-defining events occurred; one child died of non-HIV-related causes (prematurity). All but two had CD4% > 25% at 72 weeks; however, 14 infants had virological failure and six acquired resistance mutations. CONCLUSIONS: Early treatment with stavudine, didanosine and nelfinavir was well tolerated and associated with good clinical and immunological outcomes at week 72. However, a high rate of virological failure with emergence of genotypic resistance is of great concern. More palatable drug combinations for infants and closer drug monitoring are required.

Natural history of serum HIV-1 RNA levels in 330 patients with a known date of infection. The SEROCO Study Group.

OBJECTIVE: To describe the spontaneous course, before the introduction of highly active antiretroviral therapy (HAART), of HIV-1 RNA during the AIDS-free period of the disease. To assess the predictive value of changes in HIV-1 RNA levels. DESIGN: A total of 330 patients with a known date of infection followed in the SEROCO cohort. METHODS: HIV-1 RNA levels (threshold, 200 copies/ml) were evaluated from 2243 frozen sera obtained from enrolment until the onset of AIDS or until February 1996. Lowess curves were used to describe the variations of viraemia during follow-up. A Cox regression model was used to assess the predictive value of early and updated CD4 cell count and viral load. RESULTS: In addition to a lower early viral load, patients who remained AIDS-free had, on average, a longer period of viral load decrease after infection (36 versus 18 months), followed by a slower viral load increase compared with those who progressed to AIDS. A true plateau-phase after the seroconversion period, lasting approximately 4 years, was identified only in patients who remained AIDS-free for at least 90 months. In multivariate analysis, both early viral load and later changes were significant predictors of progression to AIDS. A decrease in the CD4 cell count to less than 200 cells/microl and the onset of a group B condition remained significant predictors of progression. CONCLUSION: Our study extends to the early post-seroconversion phase the prognostic value of extracellular HIV-1 RNA levels. Moreover, our data suggest that, in most HIV-infected individuals, a progressive loss of control of viral replication arises during the early years of HIV-1 infection.

Harmful long-term impact of hepatitis C virus infection in kidney transplant recipients.

BACKGROUND: The long-term impact of hepatitis C virus (HCV) infection in renal transplant recipients remains controversial. We report here our experience, in a homogeneous single center, of 499 patients with a fairly long follow-up. METHODS: We retrospectively studied 499 hepatitis B virus-negative patients who received an initial cadaver donor kidney transplantation at Necker Hospital between January 1, 1979 and December 31, 1994, with a graft or patient survival of at least 6 months. Anti-HCV antibodies were detected at time of transplantation in 112 patients (22%). Patient survival and causes of death were compared among anti-HCV-positive and -negative patients RESULTS: Our results clearly indicate that first cadaver kidney transplant recipients with anti-HCV antibodies had a significantly shorter patient and graft long-term survival than recipients without anti-HCV antibodies (P<0.01 and P<0.0001 respectively). Mean follow-up time after transplantation was 79+/-2 months in the former group and 81+/-5 months in the latter (NS). Increased mortality was primarily caused by liver disease (P<0.001) and sepsis (P<0.01). In a multivariate analysis, HCV infection significantly affected the mortality rate (odds ratio: 2.8). CONCLUSIONS: These results suggest that HCV infection has a harmful long-term impact on the survival of kidney transplant recipients.

Azathioprine hepatitis in kidney transplant recipients. A predisposing role of chronic viral hepatitis.

Influence of viral liver diseases on the occurrence of azathioprine hepatitis was evaluated in 21 kidney transplant recipients. Diagnosis of azathioprine hepatitis was always based on jaundice, which disappeared after azathioprine withdrawal in 18 patients and after azathioprine dose reduction in 3 patients. Histopathological diagnosis of azathioprine toxicity was ascertained in 14 patients. Rechallenge with azathioprine performed in 4 patients, within 2-4 months after the first jaundice episode, resulted in relapse of jaundice in all cases. Viral hepatitis B virus and hepatitis C markers were present in all 20 tested patients (serum hepatitis B surface antigen in 6 patients and anti-HCV antibodies in 17 patients). Biopsy-proven chronic hepatitis was observed in 18 patients, including 14 chronic active hepatitis, 3 chronic persistent hepatitis and cirrhosis in 1. In kidney transplant recipients, azathioprine hepatitis seems to be facilitated or induced by hepatitis B virus or hepatitis C virus chronic hepatitis. Azathioprine reduction or withdrawal should therefore be combined with the diagnostic evaluation and the treatment of viral liver diseases.

Different distribution of HIV type 1 genetic variants in European patients with distinct risk practices.

The use of two genetic markers has permitted the analysis of the distribution of two different human immunodeficiency virus type 1 (HIV-1) variants in patients of the homosexual (HO) and intravenous drug user (IDU) groups in distinct European countries. In Germany, Holland, and Italy the variants circulating in each risk group of HO and IDU patients were genetically distinguishable according to the genetic markers used. In contrast, in France and Spain, the same variant has been recovered from patients with different risk practices. These data highlight the diversity of the HIV-1 epidemic in Europe and the different patterns of HIV-1 variant distribution in European countries.

Human immunodeficiency virus-1 infection in neonates: correlation of plasma and cellular viremia and clinical outcome. French Pediatric Cohort Study Group.

Among human immunodeficiency virus-1 (HIV-1) vertically infected children, two patterns of disease progression have been observed: about 25% develop a severe immunodeficiency within the first 2 years of life; the rest experience a slower progression, like adults. We have assessed infectious viral burden in infected neonates through the French National Prospective Study. Plasma and cell-associated viremia were assayed by endpoint-dilution cultures in samples from 46 infants followed prospectively from birth. Plasma and cell-associated viral burden were found to be significantly higher in rapid progressing infants than in non-progressing infants in the first months of life: before the age of 2 months, between 2 and 4 months of age and by the age of 6 months. Moreover, among the non-progressing children, the infectious viral burden before the age of 4 months was predictive of the viral burden measured after the age of 12 months. In conclusion, this work demonstrates that infectious viral load is a reliable predictive marker for rapid progression to AIDS in infants and could be useful for initiating antiretroviral therapy.