Isabelle De Vincenzi

Probability of Heterosexual Transmission of HIV: Relationship to the Number of Unprotected Sexual Contacts

: The objective of this study was to investigate the relationship between the number of unprotected heterosexual contacts with an HIV-infected person and the probability of HIV transmission. Data from a European study involving 563 heterosexual partners of HIV-infected subjects were analyzed. The number of unprotected contacts could be estimated for 525 couples (377 with male index case, 148 with female index case) from the reported frequency of unprotected contacts and an estimate of the length of the period during which transmission could have occurred. Nonparametric (isotonic regression) and parametric (Bernoulli model) analyses were performed on data at study entry and on follow-up data (121 couples). The nonparametric analysis resulted in several exposure groups, with the proportion of infected partners increasing with the number of contacts. For example, the percentage of female partners infected ranged from 10%, among those with < 10 unprotected contacts with an infected male, to 23% after 2,000 unprotected contacts. The parametric estimates of (assumed constant) per-contact infectivity were higher for male-to-female than for female-to-male transmission, but not significantly so. However, in comparison with nonparametric estimates, the model assuming constant infectivity appears to seriously underestimate the risk after very few contacts and to seriously overestimate the risk associated with a large number of contacts. Our results suggest that the association between the number of unprotected sexual contacts and the probability of infection is weak and highly inconsistent with constant per-contact infectivity. Probable explanations for these findings include large variability in infectivity between couples and within individuals over time. Estimates based on partner study data under the hypothesis of constant infectivity can, therefore, be highly misleading at a public health level, particularly when extrapolated to multiple casual contacts.

Comparative prevalence, incidence and short-term prognosis of cervical squamous intraepithelial lesions amongst Hiv-positive and Hiv-negative women

Objective: To investigate the impact of HIV infection on the prevalence, incidence and short‐term prognosis of squamous intraepithelial lesions (SIL), in a prospective study with 1‐year follow‐up. Methods: Between 1993 and 1995, 271 HIV‐positive and 171 HIV‐negative women at high risk of HIV infection were recruited, 365 (82.6%) of whom completed the 1‐year follow‐up. The women underwent a Papanicolaou smear test at inclusion and at 6 and 12 months. Human papillomavirus (HPV) was detected at inclusion by Southern blot and PCR. Results: The SIL prevalence ranged from 7.5% for HIV‐negative to 31.3% for HIV‐positive women with CD4 cell counts < 500 × 106/l (P < 0.001). Other factors associated independently and significantly with SIL prevalence were HPV‐16, 18, 33 and related types, HPV‐31, ‐35, ‐39 and related types, lifetime number of partners, younger age, past history of SIL and lack of past cervical screening. The SIL incidence ranged from 4.9% in HIV‐negative women to 27% in HIV‐positive women with CD4 cells < 500 × 106/l (P < 0.001). Progression from low‐ to high‐grade SIL during follow‐up was detected in 38.1% of HIV‐positive women with CD4 cells ≤ 500 × 106/l but in no HIV‐negative nor HIV‐positive women with CD4 cells > 500 × 106/l. HPV‐16, 18, 33 and related types were also associated with higher incidence of SIL and progression from low‐ to high‐grade SIL. Conclusion: HIV‐induced immunodeficiency is associated with high prevalence, incidence and persistence/progression of SIL. A pejorative influence of HIV infection without marked immunodeficiency is less clear. HIV‐positive women with SIL may thus benefit from early treatment when a useful immune response is still present.

Improved methods and assumptions for estimation of the HIV/AIDS epidemic and its impact: Recommendations of the UNAIDS Reference Group on estimates, modelling and projections

UNAIDS and WHO produce biannual country-specific estimates of HIV/AIDS and its impact. These estimates are based on methods and assumptions that reflect the best understanding of HIV epidemiology and demography at the time. Where significant advances are made in epidemiological and demographic research, the methods and assumptions must evolve to match these advances. UNAIDS established an Epidemiology Reference Group in 1999 to advise them and other organisations on HIV epidemiology and methods for making estimates and projections of HIV/AIDS. During the meeting of the reference group in 2001, four priority areas were identified where methods and assumptions should be reviewed and perhaps modified: a) models of the HIV epidemic, b) survival of adults with HIV-1 in low and middle income countries, c) survival of children with HIV-1 in low and middle income countries, and d) methods to estimate numbers of AIDS orphans. Research and literature reviews were carried out by Reference Group members and invited specialists, prior to meetings held during 2001-2. Recommendations reflecting the consensus of the meeting participants on the four priority areas were determined at each meeting. These recommendations were followed in UNAIDS and WHO development of country-specific estimates of HIV/AIDS and its impact for end of 2001.UNAIDS and WHO produce biannual country-specific estimates of HIV/AIDS and its impact. These estimates are based on methods and assumptions that reflect the best understanding of HIV epidemiology and demography at the time. Where significant advances are made in epidemiological and demographic research, the methods and assumptions must evolve to match these advances. UNAIDS established an Epidemiology Reference Group in 1999 to advise them and other organisations on HIV epidemiology and methods for making estimates and projections of HIV/AIDS. During the meeting of the reference group in 2001, four priority areas were identified where methods and assumptions should be reviewed and perhaps modified: a) models of the HIV epidemic, b) survival of adults with HIV-1 in low and middle income countries, c) survival of children with HIV-1 in low and middle income countries, and d) methods to estimate numbers of AIDS orphans. Research and literature reviews were carried out by Reference Group members and invited specialists, prior to meetings held during 2001-2. Recommendations reflecting the consensus of the meeting participants on the four priority areas were determined at each meeting. These recommendations were followed in UNAIDS and WHO development of country-specific estimates of HIV/AIDS and its impact for end of 2001.

Use of antiretroviral drugs to prevent HIV-1 transmission through breast-feeding: from animal studies to randomized clinical trials.

The major remaining challenge in the prevention of mother-to-child transmission is the reduction of the risk in settings where breast-feeding is common. This review gives an update on ongoing or planned antiretroviral intervention studies in resource-limited settings that are aimed at reducing the risk of mother-to-infant HIV transmission during lactation. These strategies include antiretroviral therapy given to the mother to reduce viral load in plasma and breast milk as well as antiretroviral regimens providing prophylaxis to uninfected infants during the period of breast-feeding. The rationale for the interventions based on animal models and human studies is described as well as the study designs of clinical trials. Potential risks and benefits of these interventions to mothers and infants are also highlighted. Laboratory studies nested within several of these trials will provide a better understanding of the pathogenesis of postnatal HIV transmission and its potential prevention using antiretroviral drugs.

Pregnancies before and after HIV diagnosis in a European cohort of HIV-infected women.

ObjectivesBecause most HIV-infected women are of reproductive age, we investigated whether their reproduction planning was affected by their HIV diagnosis. DesignThe European women study is a prospective, multicentre cohort of 485 HIV-infected women with a known interval of seroconversion. MethodsThe incidence of pregnancy was measured with person–time methods. Generalized estimating equation analysis was used to determine risk factors for pregnancy and pregnancy outcomes. ResultsIn 449 women, the age-adjusted incidence of pregnancies decreased from 8.6 before HIV diagnosis to 8.2 and 6.0 per 100 person-years in 0–4 and over 4 years after HIV diagnosis, respectively (P = 0.14). The proportion of induced abortions increased from 42% before to 53% after HIV diagnosis (P < 0.05). The risk of spontaneous abortion did not increase as a result of HIV infection. Since 1995, the proportion of births increased (P = 0.009), whereas that of induced abortions decreased (P = 0.01) compared with earlier years. An increased risk of pregnancy after HIV diagnosis was found in northern and central European women compared with southern European women; there was a lower risk in single women than in women with a steady partner. Of all pregnant women, single women, women between 15 and 25 years of age, and women with multiple partners were at increased risk for induced abortion both before and after HIV diagnosis. ConclusionThe incidence of pregnancy decreased with HIV disease progression. Pregnancies after HIV diagnosis appear to be related largely to social and cultural attitudes. The number of induced abortions was high before HIV diagnosis and it significantly increases thereafter.

HIV-1 detection in cervicovaginal secretions during pregnancy.

Objective:To assess the reproducibility of and factors associated with HIV detection in cervicovaginal secretions (CVS). Design:Longitudinal study of 43 HIV-1-infected pregnant women in Paris. Methods:HIV DNA was detected in peripheral blood mononuclear cells (PBMC) by Amplicor and gagnested polymerase chain reaction (PCR) assays. The HIV genotype was determined by heteroduplex mobility assay. Amplicor and gag nested PCR assays were performed on serial CVS samples for HIV DNA detection, and the HIV Monitor test was used for HIV RNA detection in plasma and CVS. Results:A total of 144 CVS samples were collected from the women included in the study. HIV-1 DNA was detected in 36 (25%) of the 144 samples, from 16 (37.2%) of the 43 women. Results of HIV-1 DNA detection were concordant in the first two samples in 27 (84.4%) of the 32 women with at least two CVS samples. The last CVS sample collected in each woman was HIV-1 DNA-positive in 13 (30.2%) of the 43 women. Three factors were found to be independently associated with HIV-1 DNA detection in CVS: HIV-1 subtype B, absence of zidovudine therapy, and microbial cervicovaginal infection. HIV RNA was detected in CVS from 10 (23.3%) out of 43 women and correlated with DNA detection in the same sample and HIV RNA detection in plasma. Conclusions:DNA and RNA PCR can be used to detect HIV in cells and supernatants of CVS. These techniques may be useful in cohort studies to investigate HIV transmission and to evaluate the efficacy of antiretroviral drugs to reduce HIV excretion.

Relationship between mortality and feeding modality among children born to HIV-infected mothers in a research setting: the Kesho Bora study.

Objective:To assess the relationship between infant feeding practices and mortality by 18 months of age among children born to HIV-infected mothers in the Kesho Bora trial (Burkina-Faso, Kenya and South Africa). Methods:Enrolled HIV-infected women were counseled to choose between breastfeeding up to 6 months or replacement feeding from delivery. Multivariable Cox models were used to compare the infant mortality risks according to feeding practices over time defined as never breastfed, weaned or still breastfed. The category ‘still breastfed’ was disaggregated as exclusively, predominantly or partially breastfed to compare modes of breastfeeding. The relationship between weaning and mortality was also assessed using marginal structural models to control for time-dependent confounders, such as maternal or infant morbidity (reverse causality). Results:Among 795 mothers, 618 (77.7%) initiated breastfeeding. Mortality rates by 18 months among uninfected and infected children were 6 and 38%, respectively. Never breastfed and weaned children were at greater risk of death compared with those still breastfed. Adjusted hazard ratios were 6.7 [95% confidence interval (CI)=2.5–17.9; P < 0.001] and 6.9 (CI = 2.8–17.2; P < 0.001) for never breastfed and weaned children, respectively. Estimation of the effect of weaning using marginal structural models led to similar results. No statistically significant differences were observed according to mode of breastfeeding (exclusive, predominant or partial). Conclusion:Within 6 months after birth, weaned or never breastfed children were at about seven-fold higher risk of dying compared with children who were still breastfed despite a context in which interventions were provided to reduce risks associated with replacement feeding.

Morbidity in relation to feeding mode in African HIV-exposed, uninfected infants during the first 6 mo of life: the Kesho Bora study

BACKGROUND Refraining from breastfeeding to prevent HIV transmission has been associated with increased morbidity and mortality in HIV-exposed African infants. OBJECTIVE The objective was to assess risks of common and serious infectious morbidity by feeding mode in HIV-exposed, uninfected infants ≤6 mo of age with special attention to the issue of reverse causality. DESIGN HIV-infected pregnant women from 5 sites in Burkina Faso, Kenya, and South Africa were enrolled in the prevention of mother-to-child transmission Kesho Bora trial and counseled to either breastfeed exclusively and cease by 6 mo postpartum or formula feed exclusively. Maternal-reported morbidity (fever, diarrhea, and vomiting) and serious infectious events (SIEs) (gastroenteritis and lower respiratory tract infections) were investigated for 751 infants for 2 age periods (0-2.9 and 3-6 mo) by using generalized linear mixed models with breastfeeding as a time-dependent variable and adjustment for study site, maternal education, economic level, and cotrimoxazole prophylaxis. RESULTS Reported morbidity was not significantly higher in nonbreastfed compared with breastfed infants [OR: 1.31 (95% CI: 0.97, 1.75) and 1.21 (0.90, 1.62) at 0-2.9 and 3-6 mo of age, respectively]. Between 0 and 2.9 mo of age, never-breastfed infants had increased risks of morbidity compared with those of infants who were exclusively breastfed (OR: 1.49; 95% CI: 1.01, 2.2; P = 0.042). The adjusted excess risk of SIEs in nonbreastfed infants was large between 0 and 2.9 mo (OR: 6.0; 95% CI: 2.2, 16.4; P = 0.001). Between 3 and 6 mo, the OR for SIEs was sensitive to the timing of breastfeeding status, i.e., 4.3 (95% CI: 1.2, 15.3; P = 0.02) when defined at end of monthly intervals and 2.0 (95% CI: 0.8, 5.0; P = 0.13) when defined at the beginning of intervals. Of 52 SIEs, 3 mothers reported changes in feeding mode during the SIE although none of the mothers ceased breastfeeding completely. CONCLUSIONS Not breastfeeding was associated with increased risk of serious infections especially between 0 and 2.9 mo of age. The randomized controlled trial component of the Kesho Bora study was registered at Current Controlled Trials (www.controlled-trials.com) as ISRCTN71468401.

Early infant feeding patterns and HIV-free survival: findings from the Kesho-Bora Trial (Burkina Faso, Kenya, South Africa)

Objective: To investigate the association between feeding patterns and HIV-free survival in children born to HIV-infected mothers and to clarify whether antiretroviral (ARV) prophylaxis modifies the association. Methods: From June 2005 to August 2008, HIV-infected pregnant women were counseled regarding infant feeding options, and randomly assigned to triple-ARV prophylaxis (triple ARV) until breastfeeding cessation (BFC) before age 6 months or antenatal zidovudine with single-dose nevirapine (short-course ARV). Eighteen-month HIV-free survival of infants HIV-negative at 2 weeks of age was assessed by feeding patterns (replacement feeding from birth, BFC <3 months, BFC ≥3 months). Results: Of the 753 infants alive and HIV-negative at 2 weeks, 28 acquired infection and 47 died by 18 months. Overall HIV-free survival at 18 months was 0.91 [95% confidence interval (CI): 0.88–0.93]. In the short-course ARV arm, HIV-free survival (0.88; CI: 0.84–0.91) did not differ by feeding patterns. In the triple ARV arm, overall HIV-free survival was 0.93 (CI: 0.90–0.95) and BFC <3 months was associated with lower HIV-free survival than BFC ≥3 months (adjusted hazard ratio: 0.36; CI: 0.15–0.83) and replacement feeding (adjusted hazard ratio: 0.20; CI: 0.04–0.94). In the triple ARV arm, 4 of 9 transmissions occurred after reported BFC (and 5 of 19 in the short-course arm), indicating that some women continued breastfeeding after interruption of ARV prophylaxis. Conclusions: In resource-constrained settings, early weaning has previously been associated with higher infant mortality. We show that, even with maternal triple-ARV prophylaxis during breastfeeding, early weaning remains associated with lower HIV-free survival, driven in particular by increased mortality.

Postpartum weight change among HIV-infected mothers by antiretroviral prophylaxis and infant feeding modality in a research setting.

Objective:To assess the relationship between infant feeding, triple-antiretroviral prophylaxis and weight from 2 weeks (baseline) to 6 months postpartum among HIV-infected mothers in a mother-to-child transmission (MTCT) of HIV-prevention trial in five sub-Saharan African sites. Methods:HIV-infected pregnant women with CD4+ cell counts of 200–500 cells/&mgr;l were counselled to choose breastfeeding to 6 months or replacement feeding from delivery. They were randomized to receive perinatal zidovudine and single-dose nevirapine or triple-antiretroviral MTCT prophylaxis until breastfeeding cessation. Mixed-effect linear models were used to compare maternal weight trajectories over time by infant feeding mode. Antiretroviral prophylaxis and BMI at baseline were examined as potential effect modifiers. Results:Among 797 mothers, 620 (78%) initiated breastfeeding. Wasting (BMI <18.5) was rare at baseline (2%), whereas overweight/obesity (BMI ≥ 25) was common (40%). In the model including all women, breastfeeding was not associated with weight loss up to 6 months, irrespective of baseline BMI and antiretroviral prophylaxis. Triple-antiretroviral prophylaxis was associated with weight gain among replacement-feeding mothers with baseline BMI at least 25 (+0.54 kg/month; P < 0.0001). In the model including breastfeeding mothers only, triple-antiretroviral prophylaxis was associated with weight gain among mothers with baseline BMI at least 25 who ceased breastfeeding before 3 months postpartum (+0.33 kg/month; P = 0.03). Conclusion:The results suggest that breastfeeding up to 6 months postpartum is not detrimental for postpartum weight among well nourished HIV-infected mothers at intermediate-disease stage. In the absence of breastfeeding or after weaning, triple-antiretroviral prophylaxis is associated with weight gain among women with high BMI, even after cessation of prophylaxis.