Non-B HIV subtypes identified in Minnesota

July 2005

Researchers in Minnesota recently identified 83 people infected with subtypes of HIV-1 that are not common in the United States, according to a recently published report.

“We demonstrated the presence of various non-B subtypes of HIV in a region previously thought to be dominated by subtype B,” said Tracy L. Sides, MPH, senior epidemiologist and HIV surveillance coordinator, Minnesota Department of Health.

For the first two decades of the AIDS epidemic in the United States, HIV-1 subtype B has been the predominant isolate throughout the country.

“Our work underscores the need to approach diseases with a global perspective,” she told Infectious Disease News.

Studying HIV subtypes

In recent years, non-B HIV-1 subtypes have been spreading in parts of Europe. Many clinics in Europe now routinely report between 25% and 40% of their patient profile as having non-B clade virus.

Sides and colleagues of the Minnesota Department of Health and the HIV Program at Hennepin County Medical Center sought to examine the prevalence of subtype B and other subtypes in the United States, since it is not known. Subtype testing is generally not conducted with routine HIV/AIDS surveillance.

“Physicians treating patients with HIV-1 should be aware that non-B subtypes of the virus are present in the United States,” she said. “When treating a non-B HIV infection, physicians should select a viral load assay that accurately and reliably quantifies non-B subtypes of HIV-1.”

The researchers also note that all of the subtypes were detected by current US HIV diagnostic tests and that patients with non-subtype B HIV respond equally well to highly active antiretroviral therapy (HAART) as those with subtype B viruses.

In 2003, the Minnesota Department of Health piloted HIV-1 subtyping with routine surveillance to describe and monitor non-B-subtype HIV-1 isolates.

In Minnesota, African-born people make up less than 1% of the population, but in 2002 accounted for 21% of the state’s new cases of HIV.

Accordingly, Sides and colleagues conducted targeted surveillance of 98 African-born HIV patients to determine the existence and variety of HIV-1 subtypes. They also conducted subtype surveillance on 28 non-African born patients diagnosed with HIV at a publicly funded STD clinic in Minneapolis to monitor the introduction of non-B subtypes into Minnesota.

Patient selection

Researchers selected three HIV clinics in the Minneapolis–St. Paul area that provided HIV care to nearly 60% of the 335 African-born people who received a diagnosis of HIV infection through December 2002 in Minnesota, according to the study.

To participate, patients had to be born outside of the United States, living with HIV, receiving medical care at one of the health clinics, residing in Minnesota at the time of the study and be willing to provide a blood sample and informed consent.

Subtyping was made on all Western-blot positive specimens from targeted and sentinel surveillance sites. The researchers determined HIV subtype based on a partial sequence of the gp41 region of the HIV-1 env gene.

Researchers received specimens of 98 African-born HIV-1-infected patients between February 2003 and March 2004. Of these patients, 55% were women, 44% were younger than 35 years old, 80% received HIV diagnosis in 1998 or later, 87% were born in East or West Africa, and 9% were born in Central Africa, according to the study.

Of those, 89% (87/98) were successfully subtyped.

Findings indicated that 95% (83/87) of these participants were infected with non-B subtypes. Seven different subtypes were identified through targeted HIV-1 subtype surveillance, all consistent with strains endemic to the patients’ regions of birth.

Sides and colleagues determined that subtypes C, A, and CRF02_AG/A1 were the most common subtypes among participants, constituting 80% (70/87) of the total. According to the study, 90% of the patients with subtype A, D, or C were from East Africa. Subtypes AG and G were found among those born in West or Central Africa. Subtype C was found in three of the four patients born in South Africa.

Twenty-five (89%) of the 28 non-African patients with HIV-1 were successfully subtyped. Of those, 7% were women, 50% were younger than 35 years old, 64% were white, 18% were black, and 18% were of other races, according to the study.

Sides and colleagues concluded that all of these participants were infected with subtype B.

Importance of subtyping

The researchers noted they believe their results underestimate the prevalence of non-B subtypes in Minnesota because recent immigrants are less likely than assimilated immigrants to have access to the American health care system.

Since their estimates are based solely on patients from health care facilities, they probably missed recent immigrants with HIV infection.

“Our data support the need for a national surveillance system to monitor the genetic diversity of HIV and I hope our findings will encourage other states that have not yet looked at the subtypes circulating in their area to do so, particularly those with large immigrant populations,” Sides said.

Limited subtype data

In an accompanying editorial, Diane Bennett, MD, MPH, of the CDC, explained that this study is important because few such investigations of US subtype prevalence have been conducted, and because the results have national public health implications.

“The United States has no national estimates of HIV genetic diversity, and no prevalence studies have been performed in most areas of the country,” she commented. “The findings of a high prevalence of non-B subtypes in a state where African-born individuals make up less than one percent of the population suggest that it may be time to consider implementing HIV subtype surveillance in states with larger immigrant populations and throughout the United States.”

This report emphasizes the need for better surveillance of HIV-1 subtypes to determine their prevalence. Viral subtype identification may be important because subtypes may differ in terms of the efficacy of potential vaccines, treatments, diagnostic testing for HIV, and monitoring of the health of HIV patients.

“Surveillance of HIV subtypes is important because of the significant public health and clinical implications of viral genetic diversity,” Sides said. “Diagnostic tests, patient monitoring and treatment, vaccine development, and epidemiologic monitoring are all impacted by the genetic diversity of HIV.”

The report was published last month in The Journal of Infectious Diseases.

For more information:

• Sides TL, Akinsete O, Henry K, et al. HIV-1 subtype diversity in Minnesota. J Infect Dis. 2005;192:37-45.
• Bennett D. HIV-1 genetic diversity surveillance in the United States. J Infect Dis. 2005;192:4-9.