Identification of HIV type 1 group N infections in a husband and wife in Cameroon: viral genome sequences provide evidence for horizontal transmission.

HIV-1 is classified into three groups, M (major), N (non-M non-O), and O (outlier); each group arose from a separate transmission of SIVcpz into humans. HIV-1 group N was recently discovered and infections with this virus are rare with only eight documented cases. All group N infections have been found in Cameroon and there is no evidence of direct linkage between the infected patients. We report here the identification of HIV-1 group N infections in a husband and wife. The group N infection in the husband, 1131-03, was identified first based on seroreactivity in peptide EIAs and confirmed by PCR amplification of group N viral sequences. Subsequently the wife, 1015-04, was evaluated and confirmed to also be infected with a group N virus. Near full-length viral genomes were amplified and sequenced from each patient's specimen. The low level of diversity between the two viral sequences provides evidence of horizontal transmission of group N from one spouse to the other. Patient 1131-03 was receiving antiviral therapy consisting of reverse transcriptase inhibitors; the treatment appears effective for suppression of group N viral replication based on apparently low viral load in plasma specimens collected from the patient and the absence of drug resistance mutations in RT sequences amplified from 1131-03. This report brings to 10 the number of group N infections identified and to 5 the number of group N genomes sequenced. Although group N infections continue to be rare, group N is a pathogenic virus and its prevalence needs to be monitored.