Development of type 2 diabetes and insulin resistance in people with HIV infection: Prevalence, incidence and associated factors.

BACKGROUND: Diabetes and insulin resistance is an emerging issue in people with HIV. HIV-related mortality and morbidities have decreased markedly over the last few decades, while co-morbidities including type 2 diabetes (T2D) have increased. SETTING: This study investigated the incidence of T2D and insulin resistance in a cohort of HIV-patients on effective treatment. METHODS: Prevalence and baseline predictors of T2D were assessed in a cohort of 570 HIV-positive patients 50 years or older. Patients without diabetes (n = 505) were followed prospectively over a median period of 7.25 year (2012-2020) until T2D development, death or end of the study. T2D was defined as repeated fasting glucose values ≥7.0 mmol/L. Insulin resistance was defined as HOMA-IR ≥3.0. Predictors of T2D development (HIV-related parameters, lipids, hypertension, central obesity, inflammation, smoking and use of statins) were assessed using logistic regression analysis. RESULTS: 30% (153/505) had insulin resistance. During follow up (3485 patient-years) 9% (43/505) developed T2D and 7% (36/505) insulin resistance. Thus, at follow up the prevalence of either T2D or insulin resistance was 46% (232/505). T2D incidence was 1.2/100 patient-years. In multivariate analysis, after adjustment for age, T2D development was associated with baseline insulin resistance, hypertriglyceridemia, central obesity and statin treatment, but no HIV-related factors. CONCLUSION: The incidence of T2D in this cohort of patients with well controlled HIV-infection was high. The predictive factors associated with the development of T2D were not unique for HIV positive patients. The findings underline the importance of lifestyle changes in avoidance of T2D in people with HIV.

Non-AIDS Mortality Is Higher Among Successfully Treated People Living with HIV Compared with Matched HIV-Negative Control Persons: A 15-Year Follow-Up Cohort Study in Sweden.

There is an ongoing debate whether the life span of successfully treated people living with HIV (PLHIV) is comparable with that of the general population. The aim of this cohort study is to compare all-cause mortality between all PLHIV, successfully treated PLHIV, and HIV-negative control persons from the general population and to explore the impact of viral load (VL) at diagnosis. A total of 4066 PLHIV were matched against 8072 HIV-negative controls according to age, sex, and region of birth. Further, associations between VL at diagnosis, time on treatment, treatment outcome, and mortality were assessed over a 15-year period. Cox regression estimates were computed to compare the overall crude and adjusted hazard ratios (HRs) for mortality. After a 15-year follow-up period, successfully treated PLHIV were found to be three times more likely to die when compared with HIV-negative controls (HR 3.01, 95% CI 2.05-4.44, p < 0.001). The risk of mortality decreased from HR 6.02 after the first year of successful treatment. VL >30,000 c/mL at diagnosis was associated with an increased risk of mortality despite long-term antiretroviral therapy (ART) treatment. Although effective viral suppression has led to significant increases in longevity and quality of life, ART has not fully restored life expectancy to a level comparable with that found in HIV-negative persons. Even when PLHIV are successfully treated, there are several other important areas related to death, such as smoking and social factors, where data are still missing.

Lymphogranuloma venereum rates increased and Chlamydia trachomatis genotypes changed among men who have sex with men in Sweden 2004-2016.

This study aimed to determine the incidence of lymphogranuloma venereum (LGV) in Sweden since 2004 and to study in detail a consecutive number of Chlamydia trachomatis cases in men who have sex with men (MSM) during a 10 month period (September 2014 to July 2015). LGV increased from sporadic import cases in 2004 to comprise a spread within Sweden in 2016. Initially, only the L2b ompA genotype was detected, but in 2015 half of the genotyped LGV cases were L2 genotype. The changing genotype distribution in Sweden is linked to increased LGV spread in Europe. High-resolution multilocus sequence typing of 168 C. trachomatis cases from MSM in 2015 resulted in 29 sequence types, of which 3 accounted for 49 % of cases. The increased rates and different genotypes of LGV indicate that more concern for high-risk taking MSM is needed to avoid further spread of this invasive infection.

Recent increased identification and transmission of HIV-1 unique recombinant forms in Sweden.

A temporal increase in non-B subtypes has earlier been described in Sweden by us and we hypothesized that this increased viral heterogeneity may become a hotspot for the development of more complex and unique recombinant forms (URFs) if the epidemics converge. In the present study, we performed subtyping using four automated tools and phylogenetic analysis by RAxML of pol gene sequences (n = 5246) and HIV-1 near full-length genome (HIV-NFLG) sequences (n = 104). A CD4+ T-cell decline trajectory algorithm was used to estimate time of HIV infection. Transmission clusters were identified using the family-joining method. The analysis of HIV-NFLG and pol gene described 10.6% (11/104) and 2.6% (137/5246) of the strains as URFs, respectively. An increasing trend of URFs was observed in recent years by both approaches (p = 0·0082; p < 0·0001). Transmission cluster analysis using the pol gene of all URFs identified 14 clusters with two to eight sequences. Larger transmission clusters of URFs (BF1 and 01B) were observed among MSM who mostly were sero-diagnosed in recent time. Understanding the increased appearance and transmission of URFs in recent years could have importance for public health interventions and the use of HIV-NFLG would provide better statistical support for such assessments.

Establishment and stability of the latent HIV-1 DNA reservoir.

HIV-1 infection cannot be cured because the virus persists as integrated proviral DNA in long-lived cells despite years of suppressive antiretroviral therapy (ART). In a previous paper (Zanini et al, 2015) we documented HIV-1 evolution in 10 untreated patients. Here we characterize establishment, turnover, and evolution of viral DNA reservoirs in the same patients after 3-18 years of suppressive ART. A median of 14% (range 0-42%) of the DNA sequences were defective due to G-to-A hypermutation. Remaining DNA sequences showed no evidence of evolution over years of suppressive ART. Most sequences from the DNA reservoirs were very similar to viruses actively replicating in plasma (RNA sequences) shortly before start of ART. The results do not support persistent HIV-1 replication as a mechanism to maintain the HIV-1 reservoir during suppressive therapy. Rather, the data indicate that DNA variants are turning over as long as patients are untreated and that suppressive ART halts this turnover.

HIV-1 transmission between MSM and heterosexuals, and increasing proportions of circulating recombinant forms in the Nordic Countries.

Increased knowledge about HIV-1 transmission dynamics in different transmission groups and geographical regions is fundamental for assessing and designing prevention efforts against HIV-1 spread. Since the first reported cases of HIV infection during the early 1980s, the HIV-1 epidemic in the Nordic countries has been dominated by HIV-1 subtype B and MSM transmission. HIV-1 pol sequences and clinical data of 51 per cent of all newly diagnosed HIV-1 infections in Sweden, Denmark, and Finland in the period 2000-2012 (N = 3,802) were analysed together with a large reference sequence dataset (N = 4,537) by trend analysis and phylogenetics. Analysis of the eight dominating subtypes and CRFs in the Nordic countries (A, B, C, D, G, CRF01_AE, CRF02_AG, and CRF06_cpx) showed that the subtype B proportion decreased while the CRF proportion increased over the study period. A majority (57 per cent) of the Nordic sequences formed transmission clusters, with evidence of mixing both geographically and between transmission groups. Detailed analyses showed multiple occasions of transmissions from MSM to heterosexuals and that active transmission clusters more often involved single than multiple Nordic countries. The strongest geographical link was between Denmark and Sweden. Finally, Denmark had a larger proportion of heterosexual domestic spread of HIV-1 subtype B (75 per cent) compared with Sweden (49 per cent) and Finland (57 per cent). We describe different HIV-1 transmission patterns between countries and transmission groups in a large geographical region. Our results may have implications for public health interventions in targeting HIV-1 transmission networks and identifying where to introduce such interventions.

Population genomics of intrapatient HIV-1 evolution.

Many microbial populations rapidly adapt to changing environments with multiple variants competing for survival. To quantify such complex evolutionary dynamics in vivo, time resolved and genome wide data including rare variants are essential. We performed whole-genome deep sequencing of HIV-1 populations in 9 untreated patients, with 6-12 longitudinal samples per patient spanning 5-8 years of infection. The data can be accessed and explored via an interactive web application. We show that patterns of minor diversity are reproducible between patients and mirror global HIV-1 diversity, suggesting a universal landscape of fitness costs that control diversity. Reversions towards the ancestral HIV-1 sequence are observed throughout infection and account for almost one third of all sequence changes. Reversion rates depend strongly on conservation. Frequent recombination limits linkage disequilibrium to about 100 bp in most of the genome, but strong hitch-hiking due to short range linkage limits diversity.

Temporal trends in the Swedish HIV-1 epidemic: increase in non-B subtypes and recombinant forms over three decades.

BACKGROUND: HIV-1 subtype B (HIV-1B) still dominates in resource-rich countries but increased migration contributes to changes in the global subtype distribution. Also, spread of non-B subtypes within such countries occurs. The trend of the subtype distribution from the beginning of the epidemic in the country has earlier not been reported in detail. Thus the primary objective of this study is to describe the temporal trend of the subtype distribution from the beginning of the HIV-1 epidemic in Sweden over three decades. METHODS: HIV-1 pol sequences from patients (n = 3967) diagnosed in Sweden 1983-2012, corresponding to >40% of patients ever diagnosed, were re-subtyped using several automated bioinformatics tools. The temporal trends of subtypes and recombinants during three decades were described by a multinomial logistic regression model. RESULTS: All eleven group M HIV-1 subtypes and sub-subtypes (78%), 17 circulating recombinant forms (CRFs) (19%) and 32 unique recombinants forms (URF) (3%) were identified. When all patients were analysed, there was an increase of newly diagnosed HIV-1C (RR, 95%CI: 1.10, 1.06-1.14), recombinants (1.20, 1.17-1.24) and other pure subtypes (1.11, 1.07-1.16) over time compared to HIV-1B. The same pattern was found when all patients infected in Sweden (n = 1165) were analysed. Also, for MSM patients infected in Sweden (n = 921), recombinant forms and other pure subtypes increased. SIGNIFICANCE: Sweden exhibits one of the most diverse subtype epidemics outside Africa. The increase of non-B subtypes is due to migration and to a spread among heterosexually infected patients and MSM within the country. This viral heterogeneity may become a hotspot for development of more diverse and complex recombinant forms if the epidemics converge.

Longitudinal ultradeep characterization of HIV type 1 R5 and X4 subpopulations in patients followed from primary infection to coreceptor switch.

In early infection HIV-1 generally uses the CCR5 coreceptor. During disease progression the coreceptor use switches to include CXCR4 in approximately 70% of infected individuals. The primary determinant for coreceptor use is located in the V3 loop of the viral envelope. Here, ultradeep pyrosequencing (UDPS) of the V3 loop was used to investigate if CXCR4-using (X4) virus may be present as a minority population during primary HIV infection (PHI). Three patients with HIV populations that switched coreceptor use, as determined by the MT-2 cell culture assay, were investigated. Longitudinally collected plasma samples (four to nine samples per patient) obtained from PHI until after coreceptor switch were analyzed by UDPS of the V3 loop. From each sample between 279 and 32,094 reads were generated based on template molecule availability. UDPS analysis showed that the X4 virus that emerged after switch was not present during PHI or prior to overt phenotypic switch. In addition, the phylogenetic analyses indicated that the X4 populations originated from R5 variants that had evolved after the previous R5-only sample was obtained. Finally, one to three major variants were found during PHI, supporting the idea that infection is established with one or just a few viral particles.

Trends in antiretroviral therapy and prevalence of HIV drug resistance mutations in Sweden 1997-2011.

OBJECTIVE: Describe trends in antiretroviral treatments and drug resistance mutations among Swedish HIV-patients over time 1997-2011. METHODS: Treatment histories, viral sequences, and demographic and clinical data were retrieved from the national database InfCareHIV. All ART-experienced patients were included (N = 6537), while resistance tests were restricted to those obtained ≥90 days after ART start. This cohort is fully representative for Sweden since the database covers virtually all diagnosed HIV-patients since the start of the epidemic. Patients were grouped according to the year of first ART, and treatments and mutations were analyzed by calendar year. RESULTS: The prevalence of major drug resistance mutations decreased dramatically over time, most rapidly between 2003 and 2007. Since then there has been a continued slow decrease for NRTI- and PI-associated mutations with an overall prevalence among all ART-experienced patients at 1.1% (NRTI) and 0.3% (PI) in 2011. NNRTI resistance reached the lowest level in 2007-2009 (0.6%), but is now increasing (0.9% in 2011). Patients with first ART exposure before 2001 are still highly overrepresented among those with PI and, to a lesser extent, NRTI resistance. In contrast, almost half of the patients with NNRTI mutations in 2011 initiated their first ART after 2007. CONCLUSIONS: Tremendous improvements in ART options and knowledge have resulted in rapidly declining levels of resistance, and most of the current NRTI and PI mutations are found among patients with a history of suboptimal treatments. However, NNRTI resistance is increasing and is primarily found in patients infected in low- and middle-income countries who initiated ART in recent years. It is plausible that these patients were infected with resistant strains and it is therefore suggested that resource-rich countries like Sweden should test for resistance in minor quasispecies or use PI-based first-line regimens in patients who are at increased risk of carrying resistant virus.

Epstein-Barr virus genome load is increased by therapeutic vaccination in HIV-l carriers, and further enhanced in patients with a history of symptomatic primary infection.

OBJECTIVE: Epstein-Barr virus (EBV) infection is an established risk factor for B-cell lymphomas in Human Immunodeficiency virus (HIV)-1 infected patients. A disturbed EBV-host relationship is seen in patient groups with a high risk for EBV-associated lymphomas. We have analysed this relationship by measuring EBV-DNA in the blood of HIV-1 carriers. METHOD: EBV-DNA load in B-cells was monitored by PCR in non- or insufficiently antiretroviral treated and rgp160-vaccinated HIV-patients. RESULTS: Both asymptomatic HIV-infected and AIDS-patients showed a 25-40-fold increase in the number of B cell associated EBV-DNA copies compared to healthy controls. Patients included in a vaccine trial with recombinant HIV gp160 showed a 5-fold increase of EBV load compared to non-immunised patients and a 50-fold increase compared to healthy controls. There was no difference whether they received vaccine or "placebo". Vaccinated patients with a history of symptomatic primary HIV-1 infection (PHI) had a 280-fold increase in median EBV load compared to healthy controls, thus suggesting a synergistic effect between the vaccination and PHI, which hypothetically could affect lymphoma risk. CONCLUSIONS: We recommend analysis of EBV-load and long term follow up of lymphoma risk in all therapeutic HIV-1 vaccination trials.

Chlamydia trachomatis strains show specific clustering for men who have sex with men compared to heterosexual populations in Sweden, the Netherlands, and the United States.

High-resolution genotyping of Chlamydia trachomatis improves the characterization of strains infecting different patient groups and sexual networks. In this study, multilocus sequence typing (MLST) and ompA sequence determination were used for an analysis of C. trachomatis strains from 203 men who have sex with men (MSM) from Sweden, the Netherlands, and the United States. The results obtained were compared with data from 153 heterosexual women from Sweden and the Netherlands. The overlap in MLST/ompA profiles between MSM from Sweden and the Netherlands was 68%, while the overlap between heterosexual populations from these countries was only 18%. The distribution of genotypes in MSM from the United States was less similar to that in MSM from the European countries, with 45% and 46% overlaps for MSM in Sweden and the Netherlands, respectively. Minimum-spanning-tree analysis of MLST/ompA sequence types identified two large clusters that contained almost exclusively samples from MSM and comprised 74% of all MSM samples. Three other clusters were predominated by samples from women but also contained MSM specimens. Of 19 detected variants of the MLST target CT144, three variants were highly associated with MSM. Our study supports the hypotheses of both tissue tropism as well as epidemiological network structures as explanations for the linkage between specific genetic variants and sexual orientation.

Low prevalence of transmitted drug resistance in patients newly diagnosed with HIV-1 infection in Sweden 2003-2010.

Transmitted drug resistance (TDR) is a clinical and epidemiological problem because it may contribute to failure of antiretroviral treatment. The prevalence of TDR varies geographically, and its prevalence in Sweden during the last decade has not been reported. Plasma samples from 1,463 patients newly diagnosed with HIV-1 infection between 2003 and 2010, representing 44% of all patients diagnosed in Sweden during this period, were analyzed using the WHO 2009 list of mutations for surveillance of TDR. Maximum likelihood phylogenetic analyses were used to determine genetic subtype and to investigate the relatedness of the sequences. Eighty-two patients showed evidence of TDR, representing a prevalence of 5.6% (95% CI: 4.5%-6.9%) without any significant time trends or differences between patients infected in Sweden or abroad. Multivariable logistic regression showed that TDR was positively associated with men who have sex with men (MSM) and subtype B infection and negatively associated with CD4 cell counts. Among patients with TDR, 54 (68%) had single resistance mutations, whereas five patients had multi-drug resistant HIV-1. Phylogenetic analyses identified nine significantly supported clusters involving 29 of the patients with TDR, including 23 of 42 (55%) of the patients with TDR acquired in Sweden. One cluster contained 18 viruses with a M41L resistance mutation, which had spread among MSM in Stockholm over a period of at least 16 years (1994-2010). Another cluster, which contained the five multidrug resistant viruses, also involved MSM from Stockholm. The prevalence of TDR in Sweden 2003-2010 was lower than in many other European countries. TDR was concentrated among MSM, where clustering of TDR strains was observed, which highlights the need for continued and improved measures for targeted interventions.

Lipoatrophy of the footpad in HIV-treated patients is associated with increased PAI-1.

PURPOSE: To describe lipoatrophy of the plantar pedis fat pads in human immunodeficiency virus (HIV) patients with or without long-term antiretroviral therapy (ART); to compare the characteristics of ART patients with and without plantar pedis lipoatrophy; and to examine the effects of HIV and metabolic/cardiovascular risk parameters and treatment history on plantar pedis lipoatrophy. DESIGN: Participants included 134 patients who started protease inhibitors in antiretroviral therapy (ART) in 1996 and 49 treatment-naive patients, recruited in 2004. Participants were examined and graded for lipoatrophy of five body compartments including the plantar fat pads. Baseline HIV- and ART-related factors were documented together with follow-up metabolic/ cardiovascular risk parameters. RESULTS: Plantar pedis lipoatrophy occurred more often among ART patients (60%) than among treatment-naive patients (12%; p < .001). ART patients with plantar lipoatrophy were older, had higher plasminogen activator inhibitor 1 (PAI-1) values, a higher prevalence of lipoatrophy in other body compartments, and longer stavudine and didanosine treatment history as compared to patients without plantar lipoatrophy. Multiple logistic regression modeling revealed that among the metabolic/cardiovascular parameters, increased PAI-1 was strongly and positively associated with plantar lipoatrophy. Among the treatment history parameters, didanosine was the strongest independent predictor for plantar lipoatrophy. Increased PAI-1 was not associated to lipoatrophy in any other location. CONCLUSIONS: Plantar lipoatrophy is common among patients on long-term ART and, though often overlooked, may cause significant discomfort. The association to PAI-1, a well-known marker of increased cardiovascular risk, is intriguing and places further focus on the need for an active approach to evaluating and lowering cardiovascular risk factors in long-term HIV treatment.

Dynamics of HIV-1 quasispecies during antiviral treatment dissected using ultra-deep pyrosequencing.

BACKGROUND: Ultra-deep pyrosequencing (UDPS) allows identification of rare HIV-1 variants and minority drug resistance mutations, which are not detectable by standard sequencing. PRINCIPAL FINDINGS: Here, UDPS was used to analyze the dynamics of HIV-1 genetic variation in reverse transcriptase (RT) (amino acids 180-220) in six individuals consecutively sampled before, during and after failing 3TC and AZT containing antiretroviral treatment. Optimized UDPS protocols and bioinformatic software were developed to generate, clean and analyze the data. The data cleaning strategy reduced the error rate of UDPS to an average of 0.05%, which is lower than previously reported. Consequently, the cut-off for detection of resistance mutations was very low. A median of 16,016 (range 2,406-35,401) sequence reads were obtained per sample, which allowed detection and quantification of minority resistance mutations at amino acid position 181, 184, 188, 190, 210, 215 and 219 in RT. In four of five pre-treatment samples low levels (0.07-0.09%) of the M184I mutation were observed. Other resistance mutations, except T215A and T215I were below the detection limit. During treatment failure, M184V replaced M184I and dominated the population in combination with T215Y, while wild-type variants were rarely detected. Resistant virus disappeared rapidly after treatment interruption and was undetectable as early as after 3 months. In most patients, drug resistant variants were replaced by wild-type variants identical to those present before treatment, suggesting rebound from latent reservoirs. CONCLUSIONS: With this highly sensitive UDPS protocol preexisting drug resistance was infrequently observed; only M184I, T215A and T215I were detected at very low levels. Similarly, drug resistant variants in plasma quickly decreased to undetectable levels after treatment interruption. The study gives important insights into the dynamics of the HIV-1 quasispecies and is of relevance for future research and clinical use of the UDPS technology.

HIV-1 exposed uninfected men who have sex with men have increased levels of salivary CC-chemokines associated with sexual behavior.

OBJECTIVES: To determine whether soluble molecules with known anti-HIV-1 activity are increased in saliva of HIV-1 exposed uninfected individuals of discordant couples of men who have sex with men (MSM), and whether the levels of these molecules are associated with genetic polymorphisms, sexual behavior and/or HIV-1 neutralizing capacity. METHODS: Saliva and PBMC were collected from exposed uninfected individuals (n=25), and low-risk controls (n=22). Levels of CCL2, CCL3, CCL4, CCL5 and CCL11 were detected by Luminex, and SLPI, LL-37, alpha-defensins and IgA2 were detected by ELISA. Single nucleotide polymorphisms (SNPs) were investigated using mass spectrometry or PCR-sequencing. HIV-1 neutralizing activity was assessed using PBMCbased neutralization assays. Self-reported questionnaires described sexual behavior. RESULTS: Exposed uninfected individuals had significantly higher levels of salivary CCL2, CCL4, CCL5 and CCL11 as compared with controls although genetic polymorphisms within the corresponding regions were equally distributed. IgA2 was also increased in exposed uninfected individuals, whereas neither CCL3, SLPI, LL-37 nor alpha-defensins differed between exposed uninfected individuals and controls. The HIV-1 neutralizing capacity of saliva was associated with higher levels of CC-chemokines (but not SLPI, LL-37, alpha-defensins or IgA2) in both exposed uninfected individuals and controls. The increased levels of CC-chemokines were associated with a higher frequency of unprotected oral sex and/or additional casual sex partners. CONCLUSION: HIV-1 exposed uninfected MSM had higher levels of salivary CC-chemokines compared with controls, this finding associated with sexual behavior rather than with genetic polymorphisms. The increased levels of CC-chemokines associated with HIV-1 neutralizing capacity in saliva.

Induction of systemic HIV-1-specific cellular immune responses by oral exposure in the uninfected partner of discordant couples.

OBJECTIVES: Previous studies have identified HIV-specific T-cell responses in HIV-exposed uninfected individuals (EUI). However, so far no study has investigated exposure through oral sex. Our aim was to investigate whether oral exposure is enough to induce a systemic HIV-specific T-cell response. DESIGN: Peripheral blood mononuclear cells were collected from 25 EUI living with a HIV-positive partner. Sexual behavior was described by the EUI in self-reported questionnaires. All clinical data of the infected partners were well documented. METHODS: Peripheral blood mononuclear cells were stimulated with five different HIV peptide pools and HIV-specific T-cell responses were detected using the interferon-[gamma] enzyme-linked immunospot assay. Multiple cytokine production was studied longitudinally using flow cytometry intracellular cytokine assay. RESULTS: The majority of the discordant couples reported having protected anal intercourse but unprotected oral sex. Three of the 23 tested EUI with evaluable results had HIV-Gag or Nef-specific T-cell responses. Two of the responders reported unprotected oral sex as the only route of exposure. The HIV-specific CD4+ and CD8+ T cells in the Gag-responder showed production of multiple cytokines. The magnitude of the responses decreased over time when the level of exposure, determined by the viral load in the partner, declined. CONCLUSION: HIV exposure through oral sex is sufficient to induce systemic HIV-specific CD4+ and CD8+ T-cell immune responses in some uninfected individuals. Further investigation is needed to determine whether these responses have any protective role against HIV infection, or are merely evidence of exposure.

Orally exposed uninfected individuals have systemic anti-HIV responses associating with partners' viral load.

OBJECTIVES: To determine whether oral HIV-1 exposure incites a persistent systemic anti-HIV-1 response in exposed uninfected individuals of discordant couples of men who have sex with men, and whether this response associates with HIV-1 exposure measured by viral load in the HIV-positive partners. METHODS: Plasma were collected from exposed uninfected individuals (n = 25), HIV-positive partners (n = 25) and low-risk controls (n = 22). A peripheral blood mononuclear cells-based neutralization assay was used to test these samples against three primary HIV-1 isolates. Self-reported questionnaires described routes of HIV-1-exposure, and clinical records documented viral loads in HIV-positive partners. RESULTS: At enrollment, plasma samples from seven of 25 exposed uninfected individuals neutralized at least two of the three HIV-1 isolates. No samples from the 22 controls neutralized any HIV-1 isolate (P = 0.01). Of these seven exposed uninfected individuals, six retained neutralization capacity during follow-up. Neutralization capacity among exposed uninfected individuals associated with the highest measured viral load of their respective partners (P = 0.01) and also time since highest viral load (P = 0.02). Purified plasma immunoglobulin (Ig) A1-mediated neutralization was observed in six of the seven samples, whereas none of the IgA1-depleted plasma samples neutralized HIV-1. The neutralizing IgA1 was not HIV envelope specific as detected by ELISA and western blot. CONCLUSION: Orally exposed uninfected men who have sex with men can mount neutralizing anti HIV-1 activity in plasma, mediated primarily by non-HIV envelope-specific IgA1. Neutralization was associated with previous measured highest viral load in the HIV-positive partner, as well as time elapsed since the peak viral load. Neutralization also persisted over time in spite of a continuous low viral exposure.