Over 40 nonhuman primate (NHP) species harbor species-specific simian immunodeficiency viruses (SIVs). Similarly, more than 20 species of nondomestic felids and African hyenids demonstrate seroreactivity against feline immunodeficiency virus (FIV) antigens. While it has been challenging to study the biological implications of nonfatal infections in natural populations, epidemiologic and clinical studies performed thus far have only rarely detected increased morbidity or impaired fecundity/survival of naturally infected SIV- or FIV-seropositive versus -seronegative animals. Cross-species transmissions of these agents are rare in nature but have been used to develop experimental systems to evaluate mechanisms of pathogenicity and to develop animal models of HIV/AIDS. Given that felids and primates are substantially evolutionarily removed yet demonstrate the same pattern of apparently nonpathogenic lentiviral infections, comparison of the biological behaviors of these viruses can yield important implications for host-lentiviral adaptation which are relevant to human HIV/AIDS infection. This review therefore evaluates similarities in epidemiology, lentiviral genotyping, pathogenicity, host immune responses, and cross-species transmission of FIVs and factors associated with the establishment of lentiviral infections in new species. This comparison of consistent patterns in lentivirus biology will expose new directions for scientific inquiry for understanding the basis for virulence versus avirulence.

https://www.researchgate.net/profile/Sue_Vandewoude/publication/6754716_Going_wild_lessons_from_naturally_occurring_T-lymphotropic_lentiviruses/links/542d77d00cf277d58e8cc907.pdf

Going Wild: Lessons from Naturally Occurring T-Lymphotropic Lentiviruses

Simian immunodeficiency virus (SIV) naturally infects non-human primates in Africa. To date, 40 SIVs have been described both in natural hosts and in heterologous species. These viruses are highly diverse and the majority cluster in 6 relatively equidistant phylogenetic lineages. At least 8 SIVs are currently considered as recombinant viruses, based on different clustering patterns in different genomic regions. Only three types of genomes are known, based on the number of accessory genes: vpr-containing genomes, vpr-vpx containing genomes and vpr-vpu-containing genomes. vpx resulted by a duplication of the vpr gene following non-homologous recombination and is characteristic of SIVs infecting the Papionini tribe of monkeys and HIV-2 in humans. vpu is characteristic of SIVcpz and HIV-1 and may have originated from a recombination involving SIVs from cercopitecini monkeys. SIV seems to be non-pathogenic in the vast majority of natural hosts in spite of a high levels of viral replication. This is probably a consequence of virus-host adaptation, in which the incubation period of the disease generally exceeds the life span of the African primate host. SIVs also have a high propensity for cross-species transmission. In the new host, the outcome may vary from inapparent infection to highly pathogenic, the former being reported for African monkeys, whereas the latter being observed in macaques and humans. The high diversity of SIVs was generated by a high mutation rate due to a low fidelity of the reverse-transcriptase and active viral and host cell turnover, host-dependent evolution and recombination. Cross-species transmission is not rare, however preferential host switching may drive the majority of cross-species transmissions. Numerous SIVs tested so far are able to grow in vitro on human PBMC, therefore it has been postulated that SIV represents a threat for infection of humans in Central Africa and that AIDS is a zoonosis. However, although the simian origin of the two HIV types is broadly acknowledged, there are no data that AIDS is acquired like a zoonosis. SIV may undergo adaptation in the new human host in order to emerge in the general population. The study of SIV in their natural hosts should provide important clues to the real threat to human populations and also elucidate the mechanisms associated with a long-term persistent viral infection without clinical consequences for the host.

The history of SIVS and AIDS: epidemiology, phylogeny and biology of isolates from naturally SIV infected non-human primates (NHP) in Africa.

Background. A randomized, controlled trial was conducted to evaluate the impact of a directly administered antiretroviral therapy program (DAART) and intensive adherence case management (IACM) intervention on virologic and immunologic response to highly active antiretroviral therapy (HAART) among patients at 3 public human immunodeficiency virus clinics in Los Angeles County, California. Methods. Participants included 250 treatment-naive and treatment-experienced persons for whom no more than 1 prior HAART regimen had failed. Five days per week for 6 months, a community worker delivered 1 HAART dose to DAART participants and observed the participant take it. IACM participants met weekly with a case manager to overcome barriers to HAART adherence. A control group (the standard of care [SOC] group) received the usual care. Results. The majority of patients were Latino (64%) or African American (24%); 57% were monolingual Spanish speakers. Seventy-five percent of the patients were male, and 64% reported an annual income of !$10,000. In an intent-to-treat analysis, no statistical differences were observed in the percentage of patients with an undetectable viral load (i.e., !400 copies/mL) at 6 months between the DAART group (54%), IACM group (60%), and SOC group (54%; ). An on-treatment analysis determined that there were no statistical differences in P 1 .05 the percentage of patients with an undetectable viral load at 6 months between the DAART group (71%), IACM group (80%), and SOC group (74%; ). Additionally, there were no statistical differences in 6-month changes P 1 .05 in the CD4 + cell count or in self-reported adherence to therapy. Conclusions. Among patients with limited prior HAART experience and adherence barriers that had not been assessed before randomization, no differences were found in virologic or immunologic response for DAART or IACM, compared with SOC, at 6 months. DAART and IACM did not improve short-term outcomes when SOC included other means of adherence support that were not controlled for by the study design.

A Randomized Trial of Directly Administered Antiretroviral Therapy and Adherence Case Management Intervention

Feline immunodeficiency virus (FIV) is a lentivirus that causes AIDS-like immunodeficiency disease in domestic cats. Free-ranging lions, Panthera leo, carry a chronic species-specific strain of FIV, FIV-Ple, which so far has not been convincingly connected with immune pathology or mortality. FIV-Ple, harboring the three distinct strains A, B, and C defined by pol gene sequence divergences, is endemic in the large outbred population of lions in the Serengeti ecosystem in Tanzania. Here we describe the pattern of variation in the three FIV genes gag, pol-RT, and pol-RNase among lions within 13 prides to assess the occurrence of FIV infection and coinfection. Genome diversity within and among FIV-Ple strains is shown to be large, with strain divergence for each gene approaching genetic distances observed for FIV between different species of cats. Multiple in fections with two or three strains were found in 43% of the FIV-positive individuals based on pol-RT sequence analysis, which may suggest that antiviral immunity or interference evoked by one strain is not consistently protective against infection by a second. This comprehensive study of FIV-Ple in a free-ranging population of lions reveals a dynamic transmission of virus in a social species that has historically adapted to render the virus benign.

Patterns of Feline Immunodeficiency Virus Multiple Infection and Genome Divergence in a Free-Ranging Population of African Lions

Pathological manifestations of feline immunodeficiency virus (FIV) infection in wild African lions.

Lion lentivirus (LLV) and puma lentivirus (PLV) exist as highly divergent virus clades among populations of indigenously infected nondomestic felidae. The feline immunodeficiency virus (FIV) is highly divergent from LLV and PLV and is pathogenic for domestic cats. When domestic cats are infected with LLV or PLV, they have immunologically and clinically silent persistent infections. We examined whether LLV or PLV infection might impart resistance to FIV superinfection in vitro by infecting domestic cat lymphoid cells with PLV and assessing resistance of these cells to FIV. We found that infection with FIV was highly restricted by prior established PLV infection. To examine whether this resistance applied in vivo, domestic cats were asymptomatically infected with either LLV or PLV and then challenged with pathogenic FIV. Although all cats became infected with FIV, prior LLV or PLV exposure blunted CD4 + cell depletion and suppressed plasma and peripheral blood mononuclear cell FIV loads relative to FIV-challenged controls not infected with LLV or PLV, despite the lack of prechallenge neutralizing antibody activity against FIV. Thus, as compared with naive controls cats previously infected with LLV or PLV were able to more effectively control FIV infection and resist its immunologic effects, despite the substantial genetic divergence between these lentiviruses-raising the possibility that superinfection may impart resistance to lentivirus infection by heightening innate immune mechanisms.

Catherine A. Hageman

Papers

Nonpathogenic lion and puma lentiviruses impart resistance to superinfection by virulent feline immunodeficiency virus.