Superinfection More Common Than Expected Among Heterosexual Cohabiting Couples in Zambia, Small Study Finds

There's nothing like hearing the results of studies directly from those who actually conducted the research. In this interview, you'll meet one of these impressive HIV researchers and read her explanation of the study she presented at ICAAC/IDSA 2008.

My name is Colleen Kraft. My poster is on HIV-1 superinfection in cohabiting Zambian heterosexual couples.¹

Colleen Kraft, M.D.

We have an HIV discordant cohort that's run by Susan Allen [Director of Rwanda Zambia HIV Research Group in Lusaka, Zambia; 1,000 [cohabiting heterosexual] couples. As they're followed for voluntary counseling and testing, when they become concordantly positive -- when the person that was HIV-negative initially becomes positive -- we look, using gp41, to see if that virus was transmitted to them from their partner. If it was not from their partner, then we look for HIV-1 superinfection from the partner.

We use a screening method called an HMA [heteroduplex mobility assay] and we compare a mix of the male and female sequences against the newly infected partner's sequence by itself. That gives us a baseline to see if we can detect a heteroduplex, which would mean that they have sequence differences that are greater than 5% but are also likely [to have come] from their spouse.

Then, we did single genome amplification from a full-length envelope and did phylogenetic analysis to see if we could detect if there was HIV superinfection. We did some recombination analysis with the bootscanning model and also looked at the clinical data.

We found that in 15 couples, or 30 people, we had three people, or two couples, that ended up having superinfection between the [partners]. In one case, the chronically infected partner had a rapid clinical deterioration with a high viral load, which was, we think, due to the superinfection, [though] we can only assume.

Going into this, had you expected that there would be that many superinfections?

No. In other cohorts, like Julie Overbaugh's cohort in Mombasa, Kenya, they have commercial sex workers, and they found a superinfection rate the same as [the rate of] primary infection of HIV. People are getting another strain [of HIV] as much as they are getting initially infected with HIV. This is a low risk; these are cohabiting heterosexual couples. We did not expect to find [superinfection] this frequently.

I think there was a superinfection study that found HIV superinfection is more likely to happen during the first year after initial diagnosis.

Some of the other research that's come out of Africa has shown that it's more likely in the first year or two, but you can have it as far out as five years.

Our next question is going to be [about] what part of the virus that we have; some of these couples [have been] followed for four or five years, so we're going to be able to answer some of those questions about why they get superinfected later or earlier, since we have both of those cases.

Thank you.

This transcript has been lightly edited for clarity.

References

1. Kraft CS, Hawkins P, Manigart O, et al. HIV-1 superinfection in cohabiting Zambian heterosexual couples. In: Program and abstracts of the 48th Annual ICAAC/IDSA 46th Annual Meeting; October 25-28, 2008; Washington, D.C. Abstract H-4049.