Thomas Parran Award Lecture: transmission and prevention of transmission of HIV-1

Host factors associated with outcome from primary human immunodeficiency virus-1 infection

PURPOSE OF REVIEW

The early events in human immunodeficiency virus-1 infection are increasingly recognized as critical for the overall evolution of the disease. Viral and host factors interact to establish a point of equilibrium defined by the viral set point. This review highlights new opportunities in the understanding of the genetic and genomic determinants of those early events.

RECENT FINDINGS

The field of human immunodeficiency virus host genetics is shifting from the measure of long-term consequences of infection to the analysis of quantitative biological endpoints of viral control, with particular attention on the earliest events as study phenotypes. The field has also been enriched by a better understanding of the determinant and complex role of human leukocyte antigen and killer cell immunoglobulin-like-receptor variation, and by the completion of the first genome-wide study of determinants of human immunodeficiency virus-1 replication. The genome analysis highlights the central influence of acquired immunity in viral control, and provides an extensive catalogue of novel gene candidates.

SUMMARY

Host genetics and genomic analyses of precise quantitative study phenotypes offer an unprecedented opportunity to dissect critical steps in human immunodeficiency virus-1 pathogenesis.

Characterization of an emerging heterosexual HIV epidemic in Russia

BACKGROUND

The Russian Federation is currently experiencing one of the fastest growing HIV epidemics worldwide. The objective was to identify sexual risk factors for recent heterosexually-acquired HIV infections.

METHODS

A case-control study of recent HIV infection was conducted in the regions of Altaiskiy Krai, Krasnoyarskiy Krai, Saratov Oblast, and Tverskaya Oblast. Data from 166 participants who did not report recent injection drug use were analyzed (19 male cases, 22 male controls, 67 female cases, 58 female controls). Independent risk factors for HIV infection are reported as adjusted odds ratios (AOR) with 95% confidence intervals (CI).

RESULTS

Risk factors were unprotected sex with an HIV-positive/status unknown regular partner (among women only: AOR 5.4, 95% CI 2.1-13); a regular sexual partner who was an injection drug user (AOR 3.6, 95% CI 1.5-8.5); 5 or more sexual partners (among men only: AOR 2.7, 95% CI 0.66-11); unprotected sex with a partner who had a diagnosed sexually transmitted infection (STI) or signs/symptoms of an STI (AOR 6.4, 95% CI 1.1-38); and undiagnosed signs/symptoms of an STI (AOR 3.4, 95% CI 1.5-7.6).

CONCLUSIONS

These data provide evidence of bridging between the injecting and noninjecting populations. Concomitant STI seem to have a major role in fueling the Russian HIV epidemic.

Risk compensation in HIV prevention: implications for vaccines, microbicides, and other biomedical HIV prevention technologies

Studies investigating the effects of biologic HIV prevention technologies have been reported with promising results for slowing the spread of the disease. Although they can reduce the rate of HIV transmission at varying levels of efficaciousness, it is vital to anticipate their impact on subsequent sexual behaviors. Risk homeostasis theory posits that decreases in perceived risk, which will occur with access to HIV prevention technologies, will correspond with increases in risk-taking behavior. Here we review the literature on risk compensation in response to HIV vaccines, topical microbicides, antiretroviral medications, and male circumcision. Behavioral risk compensation is evident in response to prevention technologies that are used in advance of HIV exposure and at minimal personal cost. We conclude that behavioral risk compensation should be addressed by implementing adjunct behavioral risk-reduction interventions to avoid negating the preventive benefits of biomedical HIV prevention technologies.

Beliefs about treatments for HIV/AIDS and sexual risk behaviors among men who have sex with men, 1997-2006

Beliefs that HIV treatments reduce HIV transmission risks are related to increases in sexual risk behaviors, particularly unprotected anal intercourse among men who have sex with men (MSM). Changes in unprotected anal intercourse and prevention-related treatment beliefs were recently reported for surveys of mostly white gay men collected in 1997 and 2005. The current study extends this previous research by replicating the observed changes in behaviors and beliefs in anonymous community surveys collected in 2006. Results indicated clear and consistent increases in beliefs that HIV treatments reduce HIV transmission risks and increases in unprotected anal intercourse. These changes were observed for both HIV positive and non-HIV positive men. African American men endorsed the belief that HIV treatments protect against HIV transmission to a greater degree than White men. Results show that HIV prevention messages need to be updated to educate MSM about the realities of HIV viral concentrations and HIV transmission risks.

The magnitude of key HIV prevention challenges in the United States: implications for a new national HIV prevention plan

The Centers for Disease Control and Prevention has undertaken an advisory process to update its national HIV prevention plan. We offer observations on the magnitude of HIV prevention challenges in the United States and reflect on how these challenges might influence the structure of a new HIV prevention plan. We recommend a plan structure that (1) is based on fundamental principles of prevention, (2) enables accountability and mid-course correction, and (3) if achieved, would result in historic changes in the US HIV epidemic. The recommended plan structure would differentially prioritize serostatus determination and prevention and care interventions for people living with HIV while retaining goals directed at high-risk HIV-negative and general population members.

Experimental infection with Haemophilus ducreyi in persons who are infected with HIV does not cause local or augment systemic viral replication

We infected 11 HIV-seropositive volunteers whose CD4(+) cell counts were >350 cells/ microL (7 of whom were receiving antiretrovirals) with Haemophilus ducreyi. The papule and pustule formation rates were similar to those observed in HIV-seronegative historical control subjects. No subject experienced a sustained change in CD4(+) cell count or HIV RNA level. The cellular infiltrate in biopsy samples obtained from the HIV-seropositive and HIV-seronegative subjects did not differ with respect to the percentage of leukocytes, neutrophils, macrophages, or T cells. The CD4(+):CD8(+) cell ratio in biopsy samples from the HIV-seropositive subjects was 1:3, the inverse of the ratio seen in the HIV-seronegative subjects (P<.0001). Although CD4(+) cells proliferated in lesions, in situ hybridization and reverse-transcription polymerase chain reaction for HIV RNA was negative. We conclude that experimental infection in HIV-seropositive persons is clinically similar to infection in HIV-seronegative persons and does not cause local or augment systemic viral replication. Thus, prompt treatment of chancroid may abrogate increases in viral replication associated with natural disease.

Genomics meets HIV-1

Genomics is now a core element in the effort to develop a vaccine against HIV-1. Thanks to unprecedented progress in high-throughput genotyping and sequencing, in knowledge about genetic variation in humans, and in evolutionary genomics, it is finally possible to systematically search the genome for common genetic variants that influence the human response to HIV-1. The identification of such variants would help to determine which aspects of the response to the virus are the most promising targets for intervention. However, a key obstacle to progress remains the scarcity of appropriate human cohorts available for genomic research.