HIV-1 superinfection is not a common event

Immunological and virological characteristics of human immunodeficiency virus type 1 superinfection: implications in vaccine design

Superinfection is frequently detected among individuals infected by human immunodeficiency virus type I (HIV-1). Superinfection occurs at similar frequencies at acute and chronic infection stages but less frequently than primary infection. This observation indicates that the immune responses elicited by natural HIV-1 infection may play a role in curb of superinfection; however, these responses are not sufficiently strong to completely prevent superinfection. Thus, a successful HIV-1 vaccine likely needs to induce more potent and broader immune responses than those elicited by primary infection. On the other hand, potent and broad neutralization responses are more often detected after superinfection than during monoinfection. This suggests that broadly neutralizing antibodies are more likely induced by sequential immunization of multiple different immunogens than with only one form of envelope glycoprotein immunogens. Understanding why the protection from superinfection by immunity induced by primary infection is insufficient and if superinfection can lead to cross-reactive immune responses will be highly informative for HIV-1 vaccine design.

Inferring viral population structures using heteroduplex mobility and DNA sequence analyses

Heteroduplex mobility (HMA) and tracking assays (HTA) are used to assess genetic relationships between DNA molecules. While distinguishing relationships between clonal or nearly clonal molecules is relatively straightforward, inferring population structures is more complex. To address this issue, HIV-1 quasispecies with varying levels of diversity were studied using both HTA and DNA sequencing. Viral diversity estimates and the temporal features of virus evolution were found to be generally concordant between HTA and DNA sequencing. In addition, the distribution of pairwise differences and the rates of virus divergence were similar between the two methods. These findings support the use of HTA to characterize variant populations of DNA and strengthen previous inferences concerning the evolution of HIV-1 over the course of infection.

Frequency and implications of HIV superinfection

HIV superinfection occurs when an individual with HIV is infected with a new distinct HIV viral strain. Superinfection has been reported throughout the world, and studies have recorded incidence rates of 0-7·7% per year. Use of next-generation sequencing has improved detection of superinfection, which can be transmitted by injecting drug use and sexual intercourse. Superinfection might have incidence rates comparable to those of initial HIV infection. Clinicians should encourage safe sexual and injecting drug use practices for HIV-infected patients because superinfection has detrimental effects on clinical outcomes and could pose a concern for large-scale antiretroviral treatment plans. The occurrence of superinfection has implications for vaccine research, since it seems initial HIV infection is not fully protective against a subsequent infection. Additional collaborative research could benefit care of patients and inform future vaccine design.

Risk behaviors among HIV-positive gay and bisexual men at party-oriented vacations

OBJECTIVE

This study examined substance use (intended and actual), unprotected sex, and HIV disclosure practices (disclosure and questioning) among HIV-positive men who have sex with men (MSM) at two party-oriented vacations, where substance use and sexual risk may be heightened.

METHOD

A random sample of 489 MSM attending one of two party-oriented vacations participated in PartyIntents, a short-term longitudinal survey. Nearly half (47%) completed a follow-up assessment at the event or online for up to 2 weeks after the event. We examined rates of baseline intentions to use substances, actual substance use, and unprotected intercourse among HIV-positive men in attendance.Rates among HIV-negative men were estimated for comparison. Multiple logistic regression was used to assess the impact of illegal drug use and HIV status on unprotected anal intercourse (UAI).

RESULTS

HIV-positive attendees (17%) were significantly more likely than HIV-negative attendees to use nitrite inhalants (or "poppers") (24.3% vs. 10.7%). HIV-positive attendees were also significantly more likely to have insertive UAI (64.3% vs. 34.1%) and receptive UAI (68.8% vs. 22.2%). Multivariate models showed associations between HIV status and illegal drug use with UAI (for HIV status, odds ratio [OR] = 4.5, p = .001; for any illegal drug use, OR = 16.4, p < .001). There was no evidence that the influence of drug use moderated risk by HIV status. Rates of HIV disclosure and questioning did not differ by HIV status.

CONCLUSIONS

HIV-positive men attending these events engaged in higher rates of illegal drug use and sexual risk than HIV-negative men. Prevention campaigns targeting MSM at high-risk events should include messages geared toward HIV-positive men.

A strategy for selecting sexual partners believed to pose little/no risks for HIV: serosorting and its implications for HIV transmission

A common HIV/AIDS risk reduction strategy among men who have sex with men (MSM) is to limit their unprotected sex partners to those who are of the same HIV status, a practice referred to as serosorting. Decisions to serosort for HIV risk reduction are based on personal impressions and beliefs, and there is limited guidance offered on this community derived strategy from public health services. This paper reviews research on serosorting for HIV risk reduction and offers an evidence-based approach to serosorting guidance. Following a comprehensive electronic and manual literature search, we reviewed 51 studies relating to the implications of serosorting. Studies showed that HIV negative MSM who select partners based on HIV status are inadvertently placing themselves at risk for HIV. Infrequent HIV testing, lack of HIV status disclosure, co-occurring sexually transmitted infections, and acute HIV infection impede the potential protective benefits of serosorting. Public health messages should continue to encourage reductions in numbers of sexual partners and increases in condom use. Risk reduction messages should also highlight the limitations of relying on one's own and partner's HIV status in making sexual risk decisions.

Evaluation of pre-screening methods for the identification of HIV-1 superinfection

The aim of this study was to compare sensitivity thresholds of two pre-screening methods - the heteroduplex mobility assay (HMA) and the presence of ambiguity codes in population-based sequences - applied for detection of HIV-1 superinfection. HIV-1 env C2-C4 PCR products generated from 48 serum samples isolated from 24 HIV-1 positive and therapy-naïve homosexual men at seroconversion and at approximately 1 year thereafter were subjected to HMA and population sequencing. Clonal sequence analysis was used to determine the sensitivity of each method to detect sequence variability. Results from HMA were compared to pairwise genetic distance of clonal sequences; heteroduplexes resulted from as little as 1.4% pairwise distance between two sequences and were detected even when only 1.5% of the pairwise distance comparisons exceeded this distance threshold. By contrast, the ambiguity code approach using population-based sequencing detected only 20.1% of existing sequence variation and was less sensitive to minority populations <or=20%, resulting in an underestimation of HIV-1 diversity. Thus, HMA was found to be more sensitive for detection of sequence variations than the ambiguity code approach, suggesting that HMA would be a more appropriate method to pre-screen for HIV-1 superinfection.

Partial protection of Simian immunodeficiency virus (SIV)-infected rhesus monkeys against superinfection with a heterologous SIV isolate

Although there is increasing evidence that individuals already infected with human immunodeficiency virus type 1 (HIV-1) can be infected with a heterologous strain of the virus, the extent of protection against superinfection conferred by the first infection and the biologic consequences of superinfection are not well understood. We explored these questions in the simian immunodeficiency virus (SIV)/rhesus monkey model of HIV-1/AIDS. We infected cohorts of rhesus monkeys with either SIVmac251 or SIVsmE660 and then exposed animals to the reciprocal virus through intrarectal inoculations. Employing a quantitative real-time PCR assay, we determined the replication kinetics of the two strains of virus for 20 weeks. We found that primary infection with a replication-competent virus did not protect against acquisition of infection by a heterologous virus but did confer relative control of the superinfecting virus. In animals that became superinfected, there was a reduction in peak replication and rapid control of the second virus. The relative susceptibility to superinfection was not correlated with CD4(+) T-cell count, CD4(+) memory T-cell subsets, cytokine production by virus-specific CD8(+) or CD4(+) cells, or neutralizing antibodies at the time of exposure to the second virus. Although there were transient increases in viral loads of the primary virus and a modest decline in CD4(+) T-cell counts after superinfection, there was no evidence of disease acceleration. These findings indicate that an immunodeficiency virus infection confers partial protection against a second immunodeficiency virus infection, but this protection may be mediated by mechanisms other than classical adaptive immune responses.

Molecular and contextual markers of hepatitis C virus and drug abuse

The spread of hepatitis C virus (HCV) infection involves a complex interplay of social risks, and molecular factors of both virus and host. Injection drug abuse is the most powerful risk factor for HCV infection, followed by sexual transmission and additional non-injection drug abuse factors such as co-infection with other viruses and barriers to treatment. It is clearly important to understand the wider context in which the factors related to HCV infection occur. This understanding is required for a comprehensive approach leading to the successful prevention, diagnosis, and treatment of HCV. An additional consideration is that current treatments and advanced molecular methods are generally unavailable to socially disadvantaged patients. Thus, the recognition of behavioral/social, viral, and host factors as components of an integrated approach to HCV is important to help this vulnerable group. Equally important, this approach is key to the development of personalized patient treatment - a significant goal in global healthcare. In this review, we discuss recent findings concerning the impact of drug abuse, epidemiology, social behavior, virology, immunopathology, and genetics on HCV infection and the course of disease.

Combination antiretroviral therapy failure and HIV super-infection

In addition to development or selection of resistance, failure to continuously suppress HIV-1 production while still using initially effective combination antiretroviral therapy (cART) may result from super-infection with a drug-resistant strain. Both transmission of drug resistant HIV and super-infection have been demonstrated. We analysed HIV pol genes obtained before start of initially successful cART and during failure while still on cART in 101 patients. Difference in precART and cART failure sequences were explained by evolution and not by super-infection.

Identifying HIV-1 dual infections

Transmission of human immunodeficiency virus (HIV) is no exception to the phenomenon that a second, productive infection with another strain of the same virus is feasible. Experiments with RNA viruses have suggested that both coinfections (simultaneous infection with two strains of a virus) and superinfections (second infection after a specific immune response to the first infecting strain has developed) can result in increased fitness of the viral population. Concerns about dual infections with HIV are increasing. First, the frequent detection of superinfections seems to indicate that it will be difficult to develop a prophylactic vaccine. Second, HIV-1 superinfections have been associated with accelerated disease progression, although this is not true for all persons. In fact, superinfections have even been detected in persons controlling their HIV infections without antiretroviral therapy. Third, dual infections can give rise to recombinant viruses, which are increasingly found in the HIV-1 epidemic. Recombinants could have increased fitness over the parental strains, as in vitro models suggest, and could exhibit increased pathogenicity. Multiple drug resistant (MDR) strains could recombine to produce a pan-resistant, transmittable virus.

We will describe in this review what is presently known about super- and re-infection among ambient viral infections, as well as the first cases of HIV-1 superinfection, including HIV-1 triple infections. The clinical implications, the impact of the immune system, and the effect of anti-retroviral therapy will be covered, as will as the timing of HIV superinfection. The methods used to detect HIV-1 dual infections will be discussed in detail. To increase the likelihood of detecting a dual HIV-1 infection, pre-selection of patients can be done by serotyping, heteroduplex mobility assays (HMA), counting the degenerate base codes in the HIV-1 genotyping sequence, or surveying unexpected increases in the viral load during follow-up. The actual demonstration of dual infections involves a great deal of additional research to completely characterize the patient's viral quasispecies. The identification of a source partner would of course confirm the authenticity of the second infection.

Routine HIV-1 genotyping as a tool to identify dual infections

OBJECTIVES

The incidence of HIV-1 dual infections is generally thought to be low, but as dual infections have been associated with accelerated disease progression, its recognition is clinically important. Methods to identify HIV-1 dual infections are time consuming and are not routinely performed.

DESIGN

Genotyping of the HIV-1 protease and reverse transcriptase (prot/RT) genes is commonly performed in the western world to detect drug-resistance mutations in clinical isolates. In our hospital, prot/RT baseline sequencing is part of the patient care for all newly infected patients in the Amsterdam region since 2003. We reasoned that degenerate base codes in this sequence could indicate either extensive viral evolution or infection with multiple HIV-1 strains.

METHODS

We amplified, cloned and sequenced multiple HIV-1 envelope (env)-V3 and gag sequences from patients with 34 or more (range 34-99) degenerate base codes in the ViroSeq genotyping RT sequence (37 out of 1661 available records) to estimate the number of HIV-1 dual infections in this group.

RESULTS

Of the 37 patients included in this study, 16 (43.2%, equal to 1% of the 1661 total records) had an HIV-1 dual infection based on phylogenetic analysis of env-V3/gag sequences. If only sequences with 45 or more degenerate base codes were taken into account, 73.3% of patients showed evidence of a dual infection.

CONCLUSION

We describe an additional use of routinely performed HIV-1 genotyping. In patients with a high number of degenerate bases (> or = 34) in RT it is important to consider the possibility of a dual HIV-1 infection.

Frequency of HIV type 1 dual infection and HIV diversity: analysis of low- and high-risk populations in Mbeya Region, Tanzania

HIV-1 diversity, frequency of recombinants, and dual infection were determined in two populations with different HIV risk behavior. A high-risk cohort of 600 female bar workers and a normal-risk population of 1,108 antenatal clinic attendees and blood donors were recruited. Behavioral data were assessed and blood for HIV- 1 diagnosis and genotyping was sampled. HIV-1 subtypes were defined through the multiregion hybridization assay (MHA(acd)). HIV-1 prevalence differed significantly among the two populations. The prevalence was 67.8% in the population of bar workers and 17% in the normal-risk population (antenatal care attendees and blood donors). Within the normal-risk population the HIV-1 prevalence was lowest in the group of volunteer blood donors. The frequency of HIV-1 infection in women was 1.7 times higher than in men. The overall subtype distribution was A (8.5%), C (40.8%), D (3.8%), AC (25.4%), AD (5.4%), CD (8.8%), and ACD (7.3%). In the high-risk population there was a higher percentage of HIV-1 recombinant strains (54% vs. 40%, p < 0.05) and a higher frequency of dual infections (19% vs. 9%, p < 0.02) compared to the normal-risk population. High-risk populations may play an important role in the evolution of HIV, as they can provide an opportunity for the virus to coinfect, recombine, and adapt to the host-specific genetic background.